OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA
LIBR
OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBR
ID
SITY OF CHIFORNIS
LIBRARY OF THE UNIVERSITY OF CALIFORNIA
SITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA
=
/ / 1> V .
219. Faults in coal-measures 408
220. Section across a Belgian coal-
field 416
221. Coal-measures in a crystalline
rock 417
222. Section across the Alabama
coal-field 419
223. Transverse section of the
Schuylkill coalfield 420
224. Cyathocrinites planus 424
225. Euomphalus pentangulatus . . ib.
226. Orthoceras kiteralis ib.
227. 228. Terebratu/a porrecta 431
229. Megalodon cucuUatus ib.
230. Clymenia linearis ib.
231. 232. Pentamerus KnigMii .. 437
233. Catenipora escharoides 438
234. Asaplius caudattis ib.
INDEX TO TABLES.
1 . Table of the principal elementary substances with their chemical equivalents 8
2. Rivers and river systems, with the areas of drainage and length of stream 34
3. Comparative view of areas drained and left undrained by river systems . . 36
4. Drainage of the North American great lakes . . . . . . . . 37
5. Magnitude and elevation of the principal plateaux or table-land .. ... 42
6. Crests and culminating points of the principal mountain chains . . . . 45
7. Constituents of the atmosphere .. .. .. .. .. .. 49
8. Barometric wind-rose for London . . . . . . . . . . ,.. .'52
9. Rain-fall on different parts of the globe . . . . 54
1 0. Conditions of mean annual temperature on the two sides of the Atlantic . . 59
1 1 . Nature of the effects produced by aqueous and atmospheric action . . 70
12. Analysis of the mud of the Nile . .* . . . . ..... . . 86
13. Nature of the effects produced by igneous action . . . . . . . . 95
14. Table of some principal thermal springs . . . . . . . . 100
15. Velocity of wave transit through various rocks . . . . . . . . 109
16. List of the principal volcanic groups on the earth, with the linear extension
of each group when determined .. .. .. .. .. ..119
17. List of known isomorphous groups of minerals .. .. .. .. 151
18. Table to assist in the determination of minerals by colour . . . . . . 156
19. Table of the classification of minerals V- 171
20. Table of hardness of minerals, and table of crystalline systems .. .. 172
21. Analyses of various kinds of coal .. .. .. .. -'-.'. .. 174
22. Composition of alum, alumstone, and aluminite .. .. ' .. ; .-. 187
23. List of zeolitic minerals .. .. .. .. .. .. .. 194
24. Analyses of clay ironstones . . . . . . . . . . . . 207
25. Analyses of Silicates containing alumina .. '.. ; ..- .. .. 230
26. Analyses of Non-aluminous and other unmetallic silicates. . .. .. 231
27. Analyses of Metallic silicates .... . . . . . . . . 232
28. Analyses of Metallic carbonates . . . . . . ; . . . . . 232
29. Analyses of Metallic oxides 233
30. Analyses of various sulphurets . . . . . . . . . . . . 234
31. Analyses of various metallic salts .. .. .. .. .. .. 235
32. Analyses of various metallic mixtures and alloys . . . . . . 236
33. Alphabetical index of simple minerals and their synonyms .. ,. 237
INDEX TO TABLES. XXV11
PAGE
34. Analyses of various sandstones used for building purposes . . 252
35. Analyses of various limestones used for building purposes . . 256
36. Analyses of magnesian limestones used for building purposes . . . . 259
37. Analyses of various important clays used for economic purposes . . . . 260
38. Analyses of coloured marls . . . . . . . 265
39. Analyses of various metamorphic rocks . . . . . 266
40. Analyses of various simple minerals forming rocks . . . . . . 268
41. Composition of various porphyritic rocks .. .. .. .. .. 270
42. Analyses of red marls and calcareous nodules contained in them . . . . 281
43. Rate of expansion of various rocks. ..... . . 302
44. Comparative view of recent and extinct species of plants . . . . 320
45. Analyses of the residuum of various species of corals . . . . 324
46. Comparative view of recent and extinct echinodermata . . . . . . 325
47. Comparative view of recent and extinct mollusca, articulata and vertebrata 331
48. Table of the superposition of fossiliferous rocks . . . . . . . . 336
49. Analyses of Tchornozem and Regur .. .. .. .. .. 343
50. Relations of the principal Eocene basins in England and France . . . . 359
51. Recent and Older tertiary representative species of certain fishes. . . . 364
52. Relations of the Upper cretaceous deposits of Europe .. .. .. 371
53. Section of Upper greensand and gault in the Isle of Wight, . . . . 376
54. Arrangement of the Lower cretaceous deposits . . . . . . . . 377
55. Subdivisions of the Permian system .. .. .. .. .. 401
56. Areas of coal, and annual production of coal in various countries . . . . 409
57. Table of the principal coal-fields in the British Islands . . . . . . ib.
58. Analyses of different kinds of Newcastle coal . . . . . . . . 411
59. Weight of water evaporated by equal weights of various kinds of coal . . 414
60. Distribution of coal in the United States of America .. .. .. 419
6 1 . Analyses of various kinds of coal . . . . . . . . . . . . 422
62. Distribution of the carboniferous fauna in England . . . . . . 424
63. Production of iron in various countries in 1845 . . . . . . . . 429
64. Production of iron in Great Britain in 1830, 1840, 1843 ib.
65. Divisions of the Devonian and Old Red sandstone rocks . . . . . . 430
66. Absorbent power of different kinds of chalk . . . . . . . . 468
67. Absorbent power of various rocks . . . . . . . . . . . . ib,
68. Analyses of spring water from various deep wells in chalk . . . . 474
69. Account of the solid contents of water obtained from various sources . . 475
70. Sinkings in the Artesian wells at Trafalgar Square and Crenelle . . . . 476
71. Analyses of fire-damp from coal-mines .. .. .. .. .. 491
72. Position and quality of the most important coal-fields of India . . . . 539
73. Analyses of coal from Borneo .. 543
74. Stratified rocks of Southern India 544
AN
ELEMENTARY COURSE
OF
Aivm rr
ERKATA.
rhe K^* n^ , co.eet.he
ln paa, line " Ch ohhe Wea.den
.. LI m jiu LI:-: JJCJ ULTCI
this point, positive knowledge has not extended ; and theoretical
views, drawn from observations at the surface, however interesting
and useful they may be, are not essential in the study of Mineralogy
and Geology. On the other hand, the facts themselves, on which these
sciences are based, are of the highest interest, and also possess direct
practical value ; and the main object in the following pages will
be to place before the student observations that have been made
and results immediately deduced from them. These will include
an account first, of the condition of matter at the earth's surface,
and the changes that take place there by the action of the various
forces of gravitation and cohesion, heat, light, electricity, and mag-
netism ; secondly, of the materials of which the surface is made up,
and their ordinary combinations ; thirdly, of the order of arrange-
ment of the inorganic materials ; fourthly, of the remains of organic
.
AN
ELEMENTARY COURSE
OF
MINERALOGY AND GEOLOGY.
1. THE world on which we live is made known to us by various
investigations, which all have reference either to the actual surface,
or to such moderate depths beneath the surface as are laid bare
by the ordinary operations of human ingenuity and labour. These
have not yet reached so far as either to verify or contradict specu-
lations often entertained concerning the condition, of the great mass
of the interior; so that we should be in total ignorance of this
condition if it were not that, from the calculations of astronomers
as to the earth's mass, we really know its average density, which
appears to be about twice as great as that of the average density of the
solid matter which forms the mass of the external surface. Beyond
this point, positive knowledge has not extended ; and theoretical
views, drawn from observations at the surface, however interesting
and useful they may be, are not essential in the study of Mineralogy
and Geology. On the other hand, the facts themselves, on which these
sciences are based, are of the highest interest, and also possess direct
practical value ; and the main object in the following pages will
be to place before the student observations that have been made
and results immediately deduced from them. These will include
an account first, of the condition of matter at the earth's surface,
and the changes that take place there by the action of the various
forces of gravitation and cohesion, heat, light, electricity, and mag-
netism ; secondly, of the materials of which the surface is made up,
and their ordinary combinations ; thirdly, of the order of arrange-
ment of the inorganic materials ; fourthly, of the remains of organic
B
2 INTRODUCTION.
bodies, contained in and associated with these inorganic materials ;
and fifthly, of the practical conclusions deduced from this kind of
knowledge in reference to agriculture, architecture, civil and military
engineering, and mining. These five departments may be designated
respectively as Physical Geography, Mineralogy, Descriptive Geology,
Palaeontology, and Practical or Economic Geology.
2. Several terms have been, from time to time, introduced into
modern languages from the Greek, to designate descriptions and
histories of the earth. Of these, GEOGRAPHY (from ge, the earth,
and graphia, an account), and GEOLOGY (ge, and logos, a discourse),
both mean in strictness the same thing, but they have been re-
ceived into the language with different senses; the former word,
Geography, being understood to include an account of the surface,
and that chiefly in its adaptation to civilised man ; while the latter
is understood to extend to the structure of the surface.*
So, again, both Geography and Geology have been considered
under various and distinct points of view, according to the taste,
the knowledge, or the immediate object of different writers ; and
terms, such as " physical," " descriptive," and " practical " have
been applied to important divisions of each, while other not less
important, if less manifest, portions have been marked off as dis-
tinct sciences, and have been called METEOROLOGY, HYDROLOGY,
MINERALOGY, PALAEONTOLOGY, &c.
3. Without either lamenting the division thus produced in a
department of science essentially one, or rejoicing at the causes
which have introduced a multitude of labourers into this fertile
field of observation, we will here rather discuss what has been done,
and what may be done, in the way of connecting and bringing to
bear upon each other the multitude of important facts of Physical
Geography and Geology, which every one ought to know, but which
many otherwise well-informed persons have greatly neglected.
The earth on which we live has too great an influence on ourselves,
directly and indirectly, to justify ignorance on the subject of its na-
ture and constitution, or the laws which govern its material existence.
The history of the present is too nearly connected with, and too di-
* A third term GEOGNOSY (from ge the earth, and gnosis knowledge), has also been intro-
duced by the Germans, and was used by early writers in our own country. It is understood to
mean the historical as distinct from the declaratory or descriptive part of the earth's history
(Bischof 's " Geologic"). This term is not likely to be referred to in modern geological works
written in the English tongue, but occurs sometimes in translations from the German, when
the translator deems it advisable to retain the technical meaning of the original, although at
the risk of being imperfectly understood by the English reader.
INTRODUCTION. 3
rectly derived from, the events of the past to allow us safely to neglect
it ; and the mode of arrangement of the materials of which the
outer film of matter, sometimes called "the earth's crust," is composed,
too deeply involves the question of the daily and yearly change that
takes place in what we see about us, to permit with safety any in-
difference in the comparison of results, often hardly to be distinguished
except in degree, and in the probable date of their occurrence.
In all these matters the investigations concerning the earth's his-
tory, which are most generally understood by the term Geology, are
found to be very interesting and important in a general sense, and
affording much useful information ; but, perhaps, it may be well,
before proceeding further, that we should consider briefly the various
applications of such knowledge to useful practical purposes, and in
various employments and professions.
4. There are two ways in which this application may be made ;
namely, with regard to the actual surface of the earth and its de-
pendence on that which happens to be beneath the surface, and also
with reference to mineral substances which it is desired to obtain
by various operations at the surface. Each is worthy of a few words
of explanation.
If in any district we know the Geography, commonly so called,
the political divisions, the natural divisions, the physical features,
the relations of the hills, mountains, plains, and valleys, the rivers
and river systems, the lakes, and the coast, yet still there remains
a very important kind of information to be supplied before we
can be said to know the country and its capabilities. We must
know its structure before we can judge of its future agricultural
value, both for soil and drainage ; we have yet to learn the proba-
bility, or otherwise, of springs of water being obtainable, the future
salubrity of the climate, the material that is at hand to be used for
buildings of all kinds, the permanency of existing conditions, espe-
cially if near the sea, and the possibility of constructing great works,
whether inland or on a coast, with any chance of their stability. We
are also ignorant of the mineral riches of the district in metalliferous
ores ; for, to comprehend all these and many similar matters, we re-
quire a knowledge of that which is beneath the surface and the
arrangement of the materials ; since the soil is derived from the un-
derlying rock, which also must be operated on in all architectural
and engineering operations.
4 INTRODUCTION.
So, again, in the construction of roads, and in many other public
works, where stone is needed for rough purposes, it may happen that
there is abundance of excellent material in the immediate vicinity,
not directly observable at the surface, but cropping out at a distance,
and thus indicated to the eye of one acquainted with the general
laws of the earth's structure. Without such knowledge, no one could
suggest where this material would be continued underground, but
with it the merest tyro could determine the spot where, by removing
some accumulation of soil and detritus, the rock exists. The time
must come when the value of such knowledge will be fully recog-
nised, and when it will be regarded as essential as the practice of
surveying to the profession of an engineer, and perhaps more useful
to the colonist than any other information he can possibly acquire.
But if a knowledge of the earth's structure is of use in operations
of this kind, what shall we say with regard to mining, where every-
thing depends on what we know of the earth's itnerior, and where
both general and local information of the usual condition and
arrangement of rocks is essential. The whole subject of practical
mining is, indeed, so immediately and directly dependent on struc-
ture, that nothing more can be necessary than to mention the fact.
Thus it appears, that in agriculture, architecture, engineering of
all kinds, and mining, an acquaintance with the arrangement of the
materials of the earth's crust, or, in other words, with GEOLOGY,
ought to be combined with, and form part of, that special instruc-
tion which is needed by all who are called upon to act in any of
those branches of practical and applied science. The results of
geolegical knowledge are hardly less interesting to the astronomer,
the zoologist, and the botanist; but these applications do not
properly come within the object of the present work.
Geology treats of the materials themselves, of which the earth is
composed, as well as the mode of their arrangement, but the former
part of the subject is usually called MINERALOGY. The elementary
discussion as to the laws governing the ultimate particles of matter
is a part of CHEMISTRY, and the facts known concerning the general
distribution of matter at the surface belong to the science of PHYSICAL
GEOGRAPHY.
PART I.
PHYSICAL GEOGRAPHY,
CHAPTER I.
OF MATTER IN GENERAL, AND ESPECIALLY OF THE MECHANI-
CAL CONDITION AND CHIEF PROPERTIES OF THE SUBSTANCES
COMMONLY MET WITH NEAR THE EARTH'S SURFACE.
5. THE material substances of which the earth is composed are
regarded either as simple or compound bodies, the former term
including such as have never yet been proved to consist of more
than one kind of substance, and the latter those which the opera-
tions of the chemist have shown to be made up of more than one.
It is evident that future investigations of chemists may either
increase or diminish the list of simple substances or elements, since
the decomposition of many now so recognised may depend on
processes not yet discovered or applied. On the other hand, the
number of possible compound bodies must be indefinite, although the
actual combinations entered into in nature are so limited in various
ways, that a list of what are called " simple minerals," or proximate
elements, found in nature, is by no means very extensive, when we
consider the large number of elementary substances (sixty-one)
admitted in the present state of chemical knowledge. (See 10.)
The supposed ultimate particles of bodies are called molecules or
atoms, and must be extremely minute. Whether the molecules of
certain compound bodies assume a special and quasi-elementary
form remains still doubtful, although facts observed by minera-
logical chemists render this not improbable ; but it is at any rate
certain, that the separation of particles may have effect to a very
great extent, without destroying the affinity between certain sub-
stances. In other words, the tendency to combine together in the
atoms of the same elementary substance is sometimes less powerful
than is observed with regard to certain compound bodies.
PHYSICAL GEOGRAPHY.
Opinions have been entertained as to the possibility of the various elementary sub-
stances being themselves but different combinations of one ultimate atom, and specu-
lations have been made as to the form which the ultimate or atoms may assume. The
spherical is that form that seems at first to suggest itself, and, being the simplest, has
been generally assumed.
Another speculation may be alluded to concerning the degree of divisibility of
matter, and thus of the dimensions of the ultimate atom. Some of the metals are
known to be reducible to an extremely minute state of division ; and, argumentativety,
matter may apparently be proved to be infinitely divisible. These, however, are
matters in which argument can have little value, and facts are extremely difficult to
obtain.
6. Matter is presented to our notice in three different conditions,
the solid, fluid, and gaseous. Some substances may readily be ob-
tained in either of these states, as water, which is usually fluid, but
in winter becomes solid, and when the pressure of the air is removed,
passes into steam at a very small increase of ordinary temperature.
Many other substances, as, for instance, the common metals, are
solid under ordinary circumstances, but may, by the aid of heat, be
melted, although they can hardly be actually converted into vapour.
Others are gaseous at the earth's surface under all common conditions,
but can, by cold and great pressure, be converted into liquids, and
many of them even into solids, while others again are far more
refractory, and will scarcely undergo change without the most violent
means, and under the most careful management.
We are thus led to expect that every substance in nature is
really susceptible of the three states above-mentioned, if we could
obtain favourable conditions of temperature and pressure. There is,
however, apparently a limit to this, since a large number of solids
become decomposed or separated into their elements under the
action of heat, before they pass into the fluid, much less the gaseous
state. This is the case with the common mineral, carbonate of lime
(limestone), which parts with its carbonic acid before fusion. In
this case, however, and perhaps in others, the decomposition may be
prevented if the mineral is confined, and hermetically sealed within
a very strong vessel.
7. Although we know nothing of the absolute weight of the
ultimate atoms of different elements, it is perfectly possible, and
very useful, to determine their relative weight, by assuming unity,
or some number, to represent what is called the atomic weight
of any one, and then by actual observation find the relative weight
of the atoms of other bodies, according to the proportions by weight
in which they combine. Thus, assuming the weight of hydrogen,
the lightest known substance, to be unity, or 1, we find that of
oxygen to be 8, for water being always composed of an equal
number of atoms of hydrogen and oxygen gas (which appears from
experiment), the weight of the atom of the latter must be eight
times that of the former, since 100 grains of water contain ll'l
COMBINATION. 7
grains of hydrogen and 88 -9 grains of oxygen. The theory thus
involved, that bodies combine only in quantities of this kind, or in
multiples of them, is a representation of the actual law of combi-
nation, and only introduces a more convenient way of speaking of
the known combining proportions of various substances. That
there are combining proportions is a simple and well-assured fact,
and every observation and investigation of modern analytical che-
mists proves its universality, so that in fact it forms the basis of all
accurate knowledge in chemistry and mineralogy.
8. The gaseous elements, and other bodies in a gaseous state,
always combine in proportionate measures of size, or volume, as well
as weight ; and the volume is more easily determined, and more
convenient, than the weight. Thus, while water consists of one
atom of hydrogen to each atom of oxygen, and while in each
hundred parts of water by weight 11-1 parts are hydrogen and 88'9
parts oxygen, there are two volumes of hydrogen for each one of
oxygen ; and not only so, but in every case hydrogen enters into
combination in double volumes. There is, therefore, a combining
measure as well as an atomic weight of the elements to be consi-
dered, if we would comprehend the true nature of combination.*
9. Combinations are generally expressed by a particular termination, the exact
meaning of which it is essential that the student should be acquainted with. Thus
when one body combines with another, the termination -ide or -uret is added to that
one which is considered to qualify or modify the other, which is then called the
base. Thus we have combinations of oxygen with one other element called oxides,
and also the following :
From Chlorine are obtained chlorides.
Bromine bromides.
Iodine iodides.
Fluorine fluorides.
And again :
From Sulphur are obtained sulphurets.
Carbon carburets.
Phosphorus phosphurets.
Sometimes, however, we read in chemical books of sulphides and sometimes of
chlorurets, but such expressions are synonyms, and rarely used.
The binary compounds of oxygen which possess acid properties, are named on a
different principle. Thus the acid produced by the combination of sulphur with oxy-
gen is called sulphuric, hyposulphuric, sulphurous, or hyposulphurous acid, according as
the proportion of oxygen is more or less considerable. This illustration will serve to
explain the system ; and, although other terms have been introduced, they will not
come before us in speaking of simple minerals.
Compounds of the second order are combinations of an acid or binary compound
with some element as a base, and they are called, as a group, salts. They are named
according to the acid they contain, the termination -ic being changed to -ate, and -otis
to -ite. Thus from carbonic acid and copper is formed carbonate of copper.
Combinations of water with other oxides are called hydrates.
In the case of double salts the acid is only mentioned once, though it applies to
* The following are the combining measures of some elements. Oxygen one, hydrogen two,
nitrogen two, chlorine two, fluorine two, phosphorus one, carbon two, silicon two, sulphur one,
bromine two, iodine two.
8
PHYSICAL GEOGRAPHY.
both bases. Thus alum is a sulphate of alumina combined with a sulphate of potash,
but is called simply a sulphate of alumina and potash.
In speaking of combinations, and using certain symbols, which are generally the
initial letters of the elements, both the chemist and mineralogist find it convenient to
understand by the symbol one equivalent by weight of the element, or, in other words,
the quantity by weight in which it combines. Thus, signifies one equivalent of
oxygen, H one equivalent of hydrogen, and HO together the combination of one
equivalent of oxygen with one of hydrogen or water. So, again, O 2 signifies two
equivalents of oxygen, and so on ; and thus, as S signifies sulphur, and three equi-
valents of oxygen with one of sulphur form sulphuric acid, S0 3 is the symbol of
sulphuric acid. So a double salt may be thus expressed, KO,S0 3 ; where K, signify-
ing the metal potassium, KO is oxide of potassium or potash, and S0 3 sulphuric acid,
and thus the above symbol expresses sulphate of potash. It is of great importance to
understand these chemical formulae, if the student would become acquainted with the
important facts of mineralogy and geology.
10. We now give a list of the elementary substances, with their
symbols, their equivalents, and in a few cases, their important and
most frequent combinations. The number tabulated is only fifty-one ;
but in addition to them are the following, hitherto only known to
the chemist : Didymium, Erbium, Lanthanum, Niobium, Pelopium,
Ruthenium, Terbium, Thorium, and two others still doubtful, Ilme-
nium and Norium.
TABLE
or
THE PRINCIPAL ELEMENTARY SUBSTANCES,
WITH THEIR CHEMICAL EQUIVALENTS.*
SYM-
BOLS.
Cl.
F.
H.
N.
ELEMENTS.
Gaseous Bodies.
fCHLORINE .
Fluorine .
HYDROGEN
fNlTROGEN
EQUIVALENTS.
H=l
35-50
1870
1-00
14-00
0=100
443-75
233-80
12-50
175-00
100-00
0. fOxYGEN 8-00
Fluid (non-metallic).
Br. | Bromine | 78'26 | 978-30
Non-metallic Solids.
COMMON COMBINATION,
B.
C.
I..
Ph.
Se.
Si.
S.
Boron
fCARBON . . .
Iodine
PHOSPHORUS.
Selenium . . .
tSlLICON . . .
fSULPHUR . . .
10-90
6-00
126-36
32-02
39-57
21-35
16-00
136-20
75-00
1579-50
400-30
494-58
266-82
200-00
HO Water.
S N0 5 Nitric acid.
i( NH~ Ammonia.
BO 3 Boracic acid.
C0 2 Carbonic acid
Si0 3 Silica.
SO 3 Sulphuric acid.
* The table is adapted from Graham's Elements of Chemistry, second edition, p. 108.
TABLE OF ELEMENTS.
SYM-
BOLS.
ELEMENTS.
Li.
K.
Na.
Ba.'
Ca.
Mg.
Metallic Bases of Alkali
Lithium
fPoTASSiUM (Kalium)
-f-SoDiUM (Natronium)
EQUIVALENTS.
H=l
6-43
39-00
22-97
Metallic Bases of Alkaline Earths.
Barium
fCALCIUM . .
MAGNESIUM ,
Strontium . .
68-64
20-00
12-67
43-84
Al.
Gl.
Yi
Zr.
Metallic Bases of Earths Proper.
t ALUMINUM
Glucinum
Yttrium
Zirconium
13-69
26-50
32-20
33-62
Metals proper.
Sb IfANTiMONY (Stibium) .. 129-03
As
Bi
Cd.
Ce.
Cr
Co
Cu.
Au.
Ir
Fe
Pb.
Mn.
Hg.
Mb.
Ni
Os.
Pd
Pt
R
Ag
Ta
Te
Sn
Ti
W
U
V
Zn
t ARSENIC .
fBlSMUTH .
Cadmium .
Cerium . . .
CHROMIUM
COBALT . . .
fCoPFER (Cuprum)
(Aurum)
Iridium
flRON (Ferrum)
LEAD (Plumbum)
MANGANESE
MERcuRY(Hydrargyrum)
Molybdenum
NICKEL ;
Osmium
fPalladium
fPLATINUM
Rhodium
fSiLVER ( Argentina) . . .
Tantalum (Columbium)
fTellurium
TIN (Stannum)
Titanium
Tungsten (Wolfram) .
Uranium
Vanadium
ZINC . .
75-00
70-95
55-74
46-00
28-15
29-52
31-66
98-33
98-68
28-00
103-56
27-67
100-07
47-88
29-57
99-56
53-27
98-68
52-11
108-00
92-30
66-14
68-82
24-29
94-64
60-00
68-55
32-52
O = ioo
80-37
487-50
287-17
858-01
250-00
158-35
548-02
171-17
331-26
402-51
420-20
1612-90
937-50
886-92
696-77
575-00
351-82
368-99
395-70
1229-16
1233-50
350-00
1294-50
345-90
1250-90
598-52
369-68
1244-49
665-90
1233-50
651-39
1350-00
1153-72
801-76
735-29
303-66
1183-00
750-00
856-89
406-59
COMMON COMBINATION
KO Potash.
NaO Soda.
BaO Baryta.
CaO Lime.
MgO Magnesia.
SrO Strontium.
A 2 3 Alumina.
G1 2 3 Glucina.
YO Yttria.
Zr 0,, Zirconia.
Sb 2 S 3 Sulphuret of Ami
mony.
Co 8 As 5 + 8HO. Cobalt
bloom.
Cu 2 S. Copper pyrites.
2CuC+HO. Malachite.
f FeO,C0 2 . Spathic iron.
\ Fe S 2 . Iron pyrites.
PbS. Galena.
Mn0 2 +H0. Wad.
HgS. Cinnabar.
MbS 2 . Sulphuret of Moly-
bdenum.
NiS. Capillary pyrites.
f AgS. Vitreous Silver.
\ AgCl 2 . Horn Silver.
ZnS. Blende.
ZnC 2 . Calamine.
10 PHYSICAL GEOGRAPHY.
A great number of these elements are exceedingly rare ; others
widely distributed, but only in extremely small quantities; and others
again are not met with, except in combination. The names of those
which require to be generally known, as being used in the arts or
producing a marked effect in nature on a large scale, are printed in
capitals in the above list, and those which occur in nature in their
simple or native form, are marked with a little dagger (t).
11. All elementary substances are formed by the aggregation, or
heaping together of the separate atoms of one element, and this is
effected always in the same way for the same substance, when under
similar conditions, so that the substance is always recognisable by
the application of the same means. A perfect or chemical combi-
nation takes place only when one or more atoms of one substance
arrange themselves in perfect symmetry by the side of one or more
atoms of another substance or of several other substances, so as to
form a complete compound atom, which afterwards is capable of
accumulation like a simple atom. The association of atoms without
the formation of compound atoms, is called mixture, and not com-
bination. The former condition (that of mixture) is seen in the
alloys of various metals, as of copper and zinc to form brass, &c. ;
and also in the mixture of oxygen with nitrogen gases existing in
the atmosphere. Combination is seen in a vast multitude of com-
mon substances, of which water is the most widely extended and
the most remarkable. In this state of combination, and as a proxi-
mate element, water, which is formed of oxygen and hydrogen gases,
enters into the composition of almost all compound solids.
12. Upon the earth's surface, and within such moderate depths
as can be penetrated by man, matter exists generally in a solid
form, except in the case of water, which though rarely to a
depth of more than five or six miles covers three-fourths of the
surface ; and the atmosphere, which invests the whole globe with an
aerial veil, reaching seventy, or even a hundred miles, above the
mean level of the surface, but gradually becoming more rare, and
its particles more widely separated in consequence of its elasticity.
But the atmosphere and water, although almost their whole sub-
stance is made up of gaseous elements (or substances, which when
uncompounded, retain the aerial condition at the earth's surface), form
only a small proportion of the whole amount of such elements, for
probably not less than one-half of all solid rocks consists of OXYGEN
GAS, which is thus the most common and abundant of all substances
and one whose properties and influence should never be lost sight of.
HYDROGEN and NITROGEN gases are next in importance to Oxygen
as materials of the crust, or external film of the earth. The former
is not only the chief constituent of water, but is also present in
large quantities in mineral fuel of all kinds, and in most minerals.
IMPORTANT ELEMENTS. 11
Nitrogen forms four-fifths of the atmosphere, and is widely distri-
buted amongst many solids. CHLORINE also is abundantly present,
as well in sea-salt as in other combinations.
13. Of the non-metallic elements, CARBON is the most abundant,
existing in all limestones and rocks containing calcareous matter,
besides forming the chief constituent of coal. SULPHUR is found in
combination with a large number of metals in their most common
form, and occurs native in volcanoes. SILICON, the base of common
flint, sandstone, and siliceous rock of all kinds, may be considered
as forming, on an average, one-half of all those rocks commonly
met with at the earth's surface, with the exception of limestones.
PHOSPHORUS and IODINE have been found in almost all rocks.
14. Of the metallic bases of earth, ALUMINUM is probably the
most abundant ; forming the characteristic part of all clays, besides
being present in almost all other rocks. POTASSIUM, SODIUM, and
MAGNESIUM, the metallic bases whence are derived the salts of
potash, soda and magnesia, are also very widely disseminated, the
two former abounding especially in volcanic rocks of all ages, while
soda is the chief ingredient of common salt, and magnesia, besides
forming an important part of some rocks, is present in sea water.
CALCIUM, from the combination of which with oxygen is produced
lime, and whence therefore all limestones are derived, is a material
of which very large quantities exist in the earth, although it is
perhaps not so abundant as the other elements above alluded to.
Of the metals, commonly so called, IRON and MANGANESE are
those most widely diffused, and the former has been calculated to
form as much as 2 per cent of the whole mineral crust of the globe.
There is scarcely a rock without them, and the same may be said of
Gold, Arsenic, and Titanium, which however are present in infinitely
smaller quantities than either of the others.
15. The mineral substances, then, which chiefly compose the
mass of the earth, may be thus stated.
1. GASES (3), Oxygen, Hydrogen, Nitrogen.
2. NON-METALLIC SOLIDS (5), Silicon, Carbon, Sulphur, Phosphorus,
Iodine.
3. METALLIC BASES OF EARTHS AND ALKALIES (5), Aluminum,
Potassium, Sodium, Magnesium, Calcium.
4. METALS (5), Iron, Manganese, Gold, Titanium, Arsenic.
All these, and many others of great importance in the arts, will
be considered at some length in a future chapter, when minerals are
described. Their names are here given, chiefly to remind the stu-
dent of the fact of their existence in sufficient abundance to
influence various common and characteristic rocks.
12 PHYSICAL GEOGRAPHY.
CHAPTER IT.
OF THE FORCES OF ATTRACTION AND REPULSION, AND OF
LIGHT, HEAT, ELECTRICITY, AND CHEMICAL AFFINITY.
16. THERE are two great and opposing forces in nature, attrac-
tion and repulsion, or in other words there is a constant tendency in
all matter to approach other matter, and a constant action of some
force, of which heat is the most usual indication, tending to keep
the particles of bodies asunder. It is necessary to consider here
so much of chemistry as may serve to explain the action of these
forces with reference to the general constitution of the earth's crust.
The forces of attraction are apparently three, namely, gravitation,
cohesion, and chemical affinity, the latter, however, existing under
very peculiar conditions, and presenting some anomalous cases.
Gravitation is the name given to the attraction of masses of matter
at some distance from each other. Cohesion is also attraction in
mass, but at immeasurably small distances, while Chemical affinity is
a somewhat similar kind of attraction acting, however, upon the
molecules or ultimate atoms. There is only one conceivable force of
repulsion, but it shows itself not alone by expansion, but also by
impenetrability. Electricity as exhibited by the phenomena of
galvanism and magnetism, as well as ordinary electrical action,
belongs to a class of forces usually spoken of as polar.
17. Gravitation appears to affect all matter, not only on and in
our earth, but throughout our solar system ; and to reach even to
the most distant of those bodies throughout the universe, recognisable
either by the eye, or by their effect upon the course which our earth
takes in space. By it every substance on the earth's surface presses
down towards the earth's centre, and thus acquires what is called
"weight," which is in direct proportion to the mass of matter contained
in a given space, and by it also the earth is kept in its position with
reference to the moon, the planets and the sun, and all other bodies
in the universe. Acting, however, thus universally, and increasing
rapidly as the distance between two bodies diminishes, still it does
not appear that gravitation alone would be sufficient to produce
that close contact on which chemical action depends, nor are the
laws which seem to govern the former force altogether applicable
in the latter case.
18. The force of Cohesion is that by which the similar molecules
or atoms of a simple substance, or similar compound atoms are
brought into aggregation, so as to form masses of matter, distin-
guishable from other masses, and having definite properties.
FORCES OF ATTRACTION. 13
This force is very great in solids, small in liquids, and absolutely
nothing in gases, where on the contrary the particles tend to sepa-
rate from each other, and are only retained at any given distance
by external pressure. Cohesion is seen in liquids by their tendency
to assume a spherical form, and also by a certain resistance to the
action of gravitation, since mercury will not run through fine
muslin ; but this cohesion being small and equal in all directions, the
slightest force is sufficient to disturb and separate the particles.
Different liquids exhibit different degrees of cohesion ; the cohesive
power being for the most part nearly proportional to the density.
The force of cohesion acting between different solid masses
brought into close contact at many points is called adhesion, and is
in some cases very considerable, though generally less in amount
than would be found to exist between different parts of one sub-
stance. This kind of attraction effects no change in the properties
of bodies, although, as in the case of cements of all kinds, it binds
different kinds of matter together.
Its power is seen and well exemplified in the case of glass,
especially when a number of plates, smooth and clean, are kept in
close contact by pressure for a long time, as when this is done it is
sometimes impossible to separate the plates without fracture. It
is recognised also in all the ordinary phenomena of friction, and
thus becomes of great practical importance, since adhesion takes
place with different force under different circumstances, and between
different substances in nature.
19. Certain bodies, when placed in contact, exhibit a tendency
to mix with each other only to a limited extent, as when a certain
quantity of common salt is dissolved in pure water ; or they actually
undergo mutual decomposition, as when limestone is placed in
diluted sulphuric acid ; while other substances, as water and alcohol,
may be mixed most intimately without any change or limit. The
cause of decomposition and recombination has been considered to
be some specific attraction between different kinds of matter, which
attraction has received the name of Chemical affinity, and as the
affinity between different bodies not only differs very widely in in-
tensity, but often exhibits itself in a kind of preference to combine
with one body rather than another, it has been called Elective
affinity, and many remarkable facts have been observed by chemists
with reference to this subject. We proceed to explain shortly the
meaning of these expressions.
Chemical combination takes place in various ways and under
various circumstances, but chiefly, and most energetically, when one
or both substances are in the gaseous or liquid state, for they are
then at once brought into very immediate contact. It is also much
assisted by heat, light, and electricity ; and, indeed, the development
14 PHYSICAL GEOGEAPHT.
of one of these imponderable forces is a usual accompaniment of
change in chemical combinations. The time required for the pro-
cess varies greatly under different circumstances.
The proportions in which bodies combine are generally very defi-
nite ; and this is more clearly seen as the affinity between the com-
bining substances is greater. There are also, however, two kinds of
mixture which are not regarded as true combinations ; the first
being like that of water and alcohol, any quantity of the one mixing
with any quantity of the other ; and the other, that of common salt
with water, where a certain quantity, and no more, of the one, is
received into and forms part of a given quantity of the other. When
this quantity has been taken up, the one substance (the fluid) is said
to be saturated with the other. The remaining and more definite
cases include the whole range of true chemical compounds.
21. It will now be understood that affinity as used in chemistry
has a very distinct and peculiar meaning. It is by no means mere
resemblance in any sense of the term, for it is not that relation of
parts or of a whole which only amounts to similarity ; nor is it
mechanical connection, or the attraction of gravitation, cohesion, or
adhesion, as understood when discussing matters relating to phy-
sical science. It means the tendency of different kinds of matter
to form distinct and definite compounds ; and in this sense it is a
peculiar force connected with almost all chemical changes and
operations.
22. One of the most singular of the properties brought under
consideration in investigating the nature of this affinity, is, that
when several bodies, each of which is capable of combination with
any of the others, are allowed to combine freely, there is a selection
made, and this is always according to the same law and is generally
very strongly marked, indicating not only a preference for one par-
ticular combination, but a long gradation of preferences, so that
particular substances select out of a large number those with which
under the circumstances they will unite, and a number of new com-
pounds is the result. Not only is this the case when all the ele-
ments are free, but sometimes when two compounds already formed
are presented to one another, though each one is capable of existing
permanently. The affinity, therefore, that exists is truly elective,
each element choosing or electing one rather than another of the
elements presented to it, and quitting one to unite with another
which it prefers.* This singular elective affinity having been proved
* Thus in dilute nitric acid we may dissolve silver, the nitric acid parting with its oxygen to
the silver, which has a greater affinity for it than the nitrogen. If in this solution, however, we
put in copper, the silver is released from combination, and the oxygen passes to the copper ; if
we put in iron, the copper goes down ; if zinc, the iron is precipitated ; if we put in ammonia, the
zinc is separated, and if, lastly, we put in caustic potass, or soda, the ammonia also is
liberated.
CHEMICAL AFFINITY. 15
to exist for each element, tables have been formed expressing the
order of affinities of each element for others.
There can be no doubt that processes of change dependent on
elective affinities are constantly going on in the solid crust of the
earth, and most distinctly in those crevices and fissures called mineral
veins, in which the great majority of simple minerals exist. It
behoves us, therefore, to bear in mind the true meaning and the
extent of affinity, and its elective character, if we would under-
stand the results presented on a grand scale in nature.
23. But affinity in chemistry is not only elective or definite as to
kind, but also, and in a very remarkable way, as to quantity, for one
element not only prefers to combine with another of a certain kind,
but also to a certain extent and no further, so that the result is not
accidental and variable, but fixed and constant.
This result, indeed, might have been anticipated from a due con-
sideration of the positive and real qualities of certain compounds,
for if every mere mixture was a chemical compound it is obvious
that there would be nothing definite in nature; but it has also
been found that although one ingredient will unite with another
in different proportions, still in such cases these proportions are
multiples one of another.
The law thus indicated includes not only the fact already known
that elements combine in definite proportions, but also that the
combining proportions are related as multiples, and in this form it
is the foundation of what has been already mentioned as the atomic
theory (see 7) ; since if we suppose bodies to be composed of
atoms of their constituent elements grouped either one and one, one
and two, one and three, and so on, and sometimes two and three,
two and five, &c., we shall perceive at once the nature of the limi-
tation of elective affinity when various quantities of different sub-
stances are presented to one another. Whether we term the ultimate
particles assumed, atoms, and speak of their atomic weight/ or whether
these atomic weights are called chemical equivalents or proportions,
as has been suggested, the main result is the same ; and we are able
to represent all those definite compounds which possess a peculiar
and distinctive character, and which alone, therefore, can be looked
upon as individuals, by certain marks and numbers which belong to
them, and them only, and have reference to their absolute and inti-
mate structure.
24. Obeying the laws of elective and quantitative affinity, the
number of actual combinations found in nature, to which any definite
character can be attached, becomes greatly limited, and all known
compounds may indeed be distributed into three orders ; the first
(binary compounds), including those where one element combines
with another, as for instance oxygen with sulphur in sulphuric acid,
16 PHYSICAL GEOGRAPHY.
and sodium with oxygen in soda ; the second (ternary compounds),
those in which one binary compound combines with another, as sul-
phuric acid with soda in Glauber's salt. And, thirdly, there are
combinations of salts with one another, or double salts (quaternary
compounds), such as alum. We have already (in paragraph 9)
explained the usual notation of chemists in this matter.
25. The agents of change in the ultimate particles of bodies are
light, heat, and electricity ; any one of these under certain circum-
stances placing the atoms in a condition favourable to chemical
action, and apparently assisting certain compounds to become de-
composed, and the elements to enter into new combinations. There
is unquestionably a very strong analogy in the case of these three
forces, although at present no proof exists of their absolute iden-
tity, and we shall here merely refer to their properties, so far as they
have reference to changes in the constitution of mineral substances.
Light and heat being very intimately related, especially in their joint
derivation from the sun, it is not easy to dissociate their ideas and
yet retain an appreciation of their actual influence on each other.
Still we must endeavour to do this, and can best succeed by simply
defining or stating the important distinctive properties of each.
26. WHITE LIGHT, proceeding from the sun, and reaching our
earth, is made up of several colours, which are not all either
reflected or transmitted to the same extent in all cases. The result is
that certain objects exhibit to the eye coloured rays only, which are
the mixed rays that result after the atmosphere and the object
regarded have absorbed a part, which is the same under similar con-
ditions, but which varies if the circumstances change. The light fall-
ing at one particular angle (35 for glass), or transmitted through
a certain thickness of any medium, is found to possess very peculiar
properties, and is said to be polarized, and a ray of light passing
through certain substances, is divided into two pencils or rays.
Light is absorbed by all ponderable substances to some extent,
when they are exposed to its influence, and the quantity absorbed
is greater in proportion to the roughness of the surface. Those
substances which present a dark colour to the eye, and through
which light is not transmitted (opaque bodies), absorb most light,
and those which are transparent, the least. The more light a body
absorbs, the more is its temperature raised when exposed directly
to the effect of the sun's rays, which produce heat as well as light.
All bodies, when heated to a certain temperature, become incan-
descent and emit light. Light is also directly connected with
electricity and magnetism, the passage of electricity being accom-
panied by the emission of light when the transmission through a
conductor is broken, and light, under certain conditions, exciting
magnetic action in a steel needle. A ray of polarized light passing
HEAT. 17
through certain transparent substances, is found to be directly
affected, and altered in position, being rotated to the right or left
hand by the passage of magnetic force through the medium, the
direction of rotation being governed by the position of the lines of
magnetic force.
Many substances are decomposed by .the action of light, and
often more readily by one colour than another. The remarkable
and interesting processes of daguerreotype and calotype, or the pro-
duction of pictures by the simple action of light, afford good exam-
ples of this chemical action. In some cases again chemical combi-
nations are effected by exposure to light, and not unfrequently such
combinations are accompanied by decompositions. Many, but not
all, of the changes produced by light, may also be brought about by
a trifling elevation of temperature, or slight electrical action, and
many substances whose affinity for each other is considerable, develop
light and heat at the moment of their combination. Other cases
occur in which mechanical violence, friction, and crystallization are
accompanied by an exhibition of light, often, but not always, con-
nected with the presence of heat and electricity.
27. HEAT, like light, is obtained from the sun's rays, and is
also excited in various ways by mechanical violence, electricity,
animal and vegetable life, and chemical combination. Rays of
heat are reflected or thrown back from the surface, and refracted,
or bent, in passing into a different medium, like rays of light, but
heat is conducted along certain substances, and transmitted through
others, more completely than light, and under different conditions.
Heat is, beyond all other forces, that which chiefly tends to
separate the atoms, or component particles, of bodies from each
other, and is always accompanied by changes of volume when
brought to act on any substance. It is, therefore, eminently a force
of repulsion, and by its agency gaseous bodies tend constantly to
expand, liquids to become gases, and solids to become liquid, and
afterwards gaseous.
Metals, and indeed all solids, expand when heated, but the
amount is generally small, and different in different substances.
The increase is not uniform in all dimensions, as some crystalline
bodies alter their form by changes of temperature, nor is it invari-
ably the case throughout nature that an addition of temperature
produces expansion ; water offering a remarkable exception among
fluids, and a compound of one half by weight of bismuth with one
fourth part of lead and one of tin presenting a similar incongruity
in solids. The case of water is, however, the most remarkable, and
is of very great importance, as upon it depend many striking results
in the general economy of nature. The temperature at which water
is most dense is 39'2 Fahr. ; while that at which it freezes, or passes
c
PHYSICAL GEOGRAPHY.
into the solid state, is well known to be 32 Fahr. : so that, in cooling
down from 39, water expands before solidifying. One result of this
is, that ice is lighter than water, and floats on its surface instead
of sinking. Another, of no less importance, is the great change
effected bj the alternate elevations and depressions of temperature
that take place in many parts of the world on each side of the point
of greatest density, and the corresponding expansions and contrac-
tions, especially in mountain districts
Heat is developed during all chemical change, as well as by per-
cussion, friction, and other mechanical violence, and by the passage
of an electric current. The action of heat alone is, in many cases,
sufficient to produce decomposition, this being the case with water
when the experiment is conducted with great care ; and probably,
at spme temperature or other, the attraction of affinity tending to
form a definite chemical compound would be completely overcome
in every case, and the elementary state of the component parts
attained.
28. The phenomena generally described as due to electricity, gal-
vanism, and magnetism, appear to be only various forms in which
one peculiar force exhibits its action. Magnetism is that form which
is best known and easiest to appreciate on a small scale, because
iron and some of its oxides and alloys exhibit attraction and repul-
sion very distinctly and powerfully, and show a tendency in the
metal, when in- the form of a needle or bar, to place itself in a con-
stant direction with reference to the poles of the earth, when freely
suspended in space. This singular property has been employed now
for a long time in the mariner's compass, as a means of ascertaining
relative position on the earth's surface. It has been found of late
years that other metals, as cobalt and nickel, partake of similar
properties,* being attracted by the magnet and becoming mag-
netic ; but, indeed, all matter is distinctly acted on, more or less
powerfully, by this force, since those elements and compounds which
cannot be made magnetic, or, in other words, which are not attracted
by the magnet, and do not, when freely suspended in bars, arrange
themselves parallel to the earth's axis (strictly speaking, one of the
magnetic axes, as will be presently explained), are repelled by the
magnet, and arrange themselves, if having the form of a bar, in
what may be called an equatorial position, that is, in a plane at
right angles to the straight line joining the two poles.t Of all
* The following is a list of the elements which are now recognised as magnetic ; viz. iron,
nickel, cobalt, manganese, chromium, cerium, titanium, palladium, platinum, osmium. Copper
and zinc, also, although in a simple state belonging to the other class, are in certain states of
combination magnetic bodies.
t This result, the recent discovery of Faraday, can only be obtained by the use of the most
powerful magnets, and is, beyond doubt, the most important contribution physical science
has received since the discoveries of Newton concerning the law of force in gravitation and
the universality of the action of that force.
POLAR, FORCE. 19
substances yet experimented on, bismuth is the most powerful of
this latter kind (called diamagnetic bodies), and after it follow phos-
phorus, antimony, zinc, tin, cadmium, sodium, mercury, lead, silver,
copper, gold, arsenic, uranium, rhodium, iridium, tungsten, which
all tend to place themselves equatorially when undergoing the direct
action of magnetic force. The crystalline condition of these bodies
influences very greatly the direct action produced by magnetic force,
but this will be considered more properly in a future paragraph.
29. If a piece of amber or sealing-wax is rubbed on cloth, it
acquires the property of attracting light bodies, and the force of
attraction thus excited is capable of extremely rapid transmission
either through or upon the surface of certain substances, of which
all the common metals are good examples. This force is called Elec-
tricity. It is diffused throughout all matter, and is constantly
producing effects on the earth, since it is developed not merely by
friction in the substances already named, but by every change in
mechanical or chemical condition effected in those and all other
substances in nature. It is best understood by regarding it as the
result of a current proceeding from or through each material sub-
stance, or of some principle which is ever active in maintaining its
equilibrium, and which, consequently must act in two directions.
It may be called a polar force.
However we may define or limit particular exhibitions of polar
force, and connect them with or separate them from other forms of
force, such as that of gravitation, cohesion, or ordinary chemical
agency, there is now no doubt of the mutual relations of all the
most important of these, since light, heat, electricity, galvanism, and
magnetism can all be made to bring about similar results, and tend
to change the position and alter the association of every known form
of matter, whether simple or compound.
30. The phenomena now recognised as those of terrestrial mag-
netism, and exhibited in various conditions and appearances of the
atmosphere and clouds, have been attributed to currents of electri-
city circulating near the contact of air and earth at the surface of
the solid matter of the globe. It has been supposed by some that
these currents traverse our globe from east to west, and that in this
way magnetic bodies take the direction of north and south, not from
the terrestrial action of fixed magnetic poles, but from the repulsion
of the currents ; but another, view of the case, an earlier theory,
according to which were assumed two fluids, positive and negative,
traversing all matter in opposite directions, and mutually attracting
and repelling each other, has been considered more satisfactory in
explaining the observed appearances.
If a magnetic bar or needle is freely suspended above the earth,
it assumes a given direction and position, which is an indication of
20 PHYSICAL GEOGRAPHY.
the earth's magnetic force. This direction is not true north, except
when the needle is suspended on one of two lines on the earth's sur-
face, called lines of no variation, one in the eastern, the other in the
western hemisphere. " The American line is singularly regular,
passing in a south-easterly direction from north latitude 60 to the
west of Hudson's Bay, across the American lakes, till it reaches the
South Atlantic Ocean, and cutting the meridian of Greenwich in
about 65 south latitude. The Asiatic line of no variation is very
irregular, owing, no doubt, to local interferences ; it begins below
New Holland in south latitude 60, bends westward across the In-
dian Ocean, and from Bombay has an inflexion eastward through
China, and then northward across the Sea of Japan, till it reaches
the latitude of 71 north, when it descends again southward with an
immense semicircular bend, which terminates in the White Sea." *
There are two points in each hemisphere which have been re-
garded as stronger and weaker points of attraction on opposite sides
of the earth's poles of revolution. These are the magnetic poles of
the earth, and are considered to have a regular motion round the
globe : the two northern ones from west to east, and the southern
ones from east to west, so that the line of no variation is constantly
shifting.t
31. " We have also remarkable variations in what is termed the
dip of the needle. It is well known that a piece of unmagnetized
steel, if carefully suspended by its centre, will swing in a perfectly
horizontal position, but if we magnetize this bar it will immediately
be drawn downwards at one end. The force of the earth's magnet-
ism attracting the dissimilar pole has caused it to dip.
" There is in the neighbourhood of the earth's equator, and cutting
it at four points, an irregular curve called the magnetic equator or
aclinic line, where the needle balances itself horizontally. As we
proceed from this line towards either pole the dip increases, until
at the north and south poles the needle takes a vertical position.
The intensity of the earth's magnetism is also found to vary with
the position, and to increase in a proportion which corresponds very
closely with the dip ; but the intensity is not a function of the dip,
and the lines of equal intensity, isodynamic lines, are not parallel
to those of equal dip. We have already remarked on the diurnal
variation of the declination of the needle ; we know, also, that there
exists a regular monthly and daily change in the magnetic intensity.
The greatest monthly change appears when the earth is in its peri-
helion and aphelion in the months of December and June, at which
* Hunt's Poetry of Science, p. 211.
t This line passed through London during the years 1657 to 1662, when the needle consequently
pointed true north. The variation commenced, and continued steadily increasing, after the latter
year, the needle always pointing west of true north, till in 1815, it diverged as much as 24 15' I/".
Since that time it has been slowly diminishing, and now in London amounts to about 23.
TERRESTRIAL MAGNETISM. 21
times a maximum occurs ; and about the time of the equinoxes,
when our planet is at the greatest mean distance from the sun, and
a minimum is detected.
" The daily variation of intensity is greatest in the summer and
least in the winter. The magnetism is generally found to be at a
minimum when the sun is near the meridian, its intensity increasing
until about six o'clock, when it again diminishes.
32. " All these well-ascertained facts give striking proof of the
dependence of terrestrial magnetism on solar influence ; and in
further confirmation of this view, we find a very remarkable coin-
cidence between the lines of equal temperature, the isothermal lines,
and those of equal dip and magnetic intensity.
"Sir David Brewster first pointed out that there were in the
northern hemisphere two poles of maximum cold ; these poles agree
with the magnetic points of convergence, and the line of maximum
heat which does not run parallel to the earth's equator is nearly
coincident with that of magnetic power. Since Seebeck has shown
us that electrical and magneto-electrical phenomena can be pro-
duced by the action of heat upon metallic bars, we have, perhaps,
approached -towards some faint appreciation of the manner in
which the solar calorific radiations may, acting on the surface of
our planet, produce electrical and magnetic effects.
33. "In 1750, Wargentin noticed that a very remarkable display
of aurora borealis was the cause of a peculiar disturbance of the
magnetic needle, and Dr. Dalton was the first to show that the
luminous rays of the aurora are always parallel to the dipping
needle, and that the auroral arches cross the magnetic meridian at
right angles. Hansteen and Arago have attended with particular
care to these influences of the northern lights, and the results of
their observations are :
"That as the crown of the aurora quits the usual place, the
dipping needle moves several degrees forward :
" That the part of the sky where all the beams of the aurora
unite, is that to which a magnetic needle directs itself, when sus-
pended by its centre of gravity :
" That the concentric circles which show themselves previously to
the luminous beams rest upon two points of the horizon, equally
distant from the magnetic meridian, and that the most elevated
points of each arch are exactly in this meridian.
" It does not appear that every aurora disturbs the magnetic
needle, as Captains Foster and Back both describe very splendid
displays of the phenomenon, which did not appear to produce any
tremor or deviation upon their instruments.
34. " Some sudden and violent movements have been from time to
time observed to take place in suspended magnets ; and since the
22 PHYSICAL GEOGRAPHY.
establishment of magnetic observatories in almost every part of
the globe, a very remarkable coincidence in the time of these agita-
tions has been detected. They are frequently connected with the
appearance of aurora borealis ; but this is not constantly the case.
These disturbances have been called magnetic storms, and over the
Asiatic and European continent, the islands of the Atlantic, and
the western hemisphere, they have been simultaneous.
"From observations made at Petersburg by Kupffer and deductions
drawn from the observations obtained by the Magnetic Association,
it appears probable that these storms arise from a sudden displacement
in the magnetic lines of the earth's surface, but the cause to which
this may be due is still to be sought for.
" In the brief and hasty sketch which has been given of the phe-
nomena of terrestrial magnetism, enough has been stated to show
the vast importance of this very remarkable power in the great
operations of nature. We are gradually reducing the immense
mass of recorded observations, and arriving at certain laws, which
are found to prevail. Still the origin of the force, whether it is
strictly electrical, whether it is the circulation of a magnetic fluid,
or whether it is merely a peculiar excitation of some property of
matter, are questions which are open for investigation."*
CHAPTER III.
OF THE EARTH AND THE CONDITION OF MATTER AT ITS
SURFACE.
35. THE matter of which the earth is composed, is collected into
a spherical mass, which, in consequence perhaps of the rotation it
has about an axis, is slightly compressed at the poles and bulges a
little at the equator. The surface of the waters of the ocean is
everywhere nearly equidistant from the earth's centre, and is the
surface from which all heights or depths are measured. The atmo-
spheric veil extends to an unknown but comparatively small elevation
above this, and the extreme depth of the waters of the ocean proba-
bly nowhere greatly exceeds the extreme altitude of the mountains
which rise above the general level of the plains. All that portion
of the solid matter which is permanently uncovered by water, is
called land. Waters collected in depressions or hollows, entirely
surrounded by land, and fed either by running streams or natural
* Hunt's Poetry of Science, ante cit. p. 213217.
MEASUREMENTS OF THE EARTH.
23
springs, are called lakes, or inland seas, and are usually nearly pure,
while those of the ocean and of some lakes, hold in solution a
certain proportion of saline matter. It is probable that all water
contains a trace of those various mineral substances very generally
distributed on the earth, and that it is in a sense a truly universal
solvent.
The mean density of the globe is something more than five and
a half times that of water (about half that of silver), and as the
density of most of the rocks found at the surface is not more than
half as great, it follows that the interior is either composed of
different proportions of the elementary substances, or that these
matters exist there in a far denser state.
36. I append here the best measurements of the earth that I have
been able to procure.
Our planet is an oblate spheroid, of Fig. 1.
which the annexed elliptical diagram (fig.
1 ) is a sectional view ; a 6, represents the
longer, or equatorial diameter, and c -
1
Atlantic System.
87,000
56,000
45,250
40,000
32,500
30,000
29,000
26,000
20,000
17,500
15,750
6,500
89,500
75,500
52,000
44,500
43,250
7,750
310,500
226,000
224,500
30,000
40,000
37,000
33,000
700,000?
600,000?
1,000,000 ?
402,000
11,000
12,000
1,300,000
250,000
95,000
10,000
2,000,000
1,175,000
380,000
335,000
250,000
153.000
82,000
Dii-ect.
410
400
375
300
225
250
410
275
205
230
125
130
360
320
320
320
275
70
1000
630
460
410
260
285
310
1500?
1400?
p
?
p
p
p
975
265
205
1600
1400
640
215
1780
1180
1150
425
10CO
640
400
Including
windings.
700
780
600
500
370
400
550
480
300
320
220
220
500
600
550
650
530
115
1750
1250
1150
520
400
640
480
2500?
2600?
2050
300
300
4000
2000
1000
300
p
2200
1300
1550
1600
860
480
2 Oder
S^l Don ..
Mediter- | Rhone
(810,000). lg
-^ / St. Lawrence and the great
1!] lakes t...
^ Delaware
^o r Mississippi- Missouri . .
^ l Rio del Norte
3' 8 "" 1 Magdalena
Q ^ ^ L Motagua
^ 1 Plata ,
& St. Francisco ^.
V
10,374,000
RIVER SYSTEMS.
35
Names of Rivers.
Area of drain-
age in British
statute square
miles.
Length of course
in Brit. stat.
miles.
Ea
A
(2,35
go"
II,
11
Ame
(485,C
^ ^
L
3 K
S D
& Ii
1
< P
li
Ame
(1,250
Casp
(727,0
Ara
(580,0
Lob
Pacific System.
c Amour
777,000
727,000
716,500
133,000
576,500
440,000
415,000
288,000
260,000
124,000
110,000
250,000 ?
260,000
225,000
Direct.
1400
1750
1325
575
950
1250
1030
700
680
620
500
800?
670
580
1475
1400
1400
515
460
640
685
p
410
?
1100
765
1050
440
1030
630
345
680
920
685
Including
windings.
2750
3300
2650
1200
2000
2500
2300
1100
1720
850
800
?
1540
920
2650
3200
2750
950
1000
1050
1150
p
685
?
2400
1030
1900
640
2750
p
740
1350
1600
1260
I Hoanr-ho
3 ' 50 )^Tcheliang ':.:..:::::
/ Ganges and Brahmapootra . . . .
^ Zambeze (Africa) .
00). * Colorado
Arctic System.
bi
5,302,000
1,233,000
1,050,000
800,000
150,000
140,000
115,000
104,000
85,000
65,000
40,000
600,000
480,000
100,000
70,000
5,032,000
530,000
110,000
87,000
320,000
260,000
240,000
lenek
000) | Churchill
1 Albany
Continental System of Asia.
i Volffa
>an joS :
oo) - IK* ..: :
J r Sir . .
00) * Amoo
1,547,000
36
PHYSICAL GEOGRAPHY.
54. The real drainage received by the different oceans is, however,
much greater than appears by the preceding table, since there are
many large areas and innumerable smaller ones not strictly included
in any system, and drained by streams of smaller size and less im-
portance. These together almost equal the areas referred to in the
table, and are thus distributed :
Area in square
Area in
Drained by the chief river systems in Europe and Asia. ^TJ sa ^ ^
1. into the Atlantic Ocean. systems. countedfor.
a. from the European coast. .405,500*.
b. into the Baltic ........ 312,500 I . fi , Q Oft ~
c. Mediterranean.. 11 0,000 f ' 0iy ' UU
d. Euxine ...... 791,000 J
2. into the Pacific Ocean .......... 2,353,500 \. 11,515,000 9,735,000
3. Indian Ocean .......... 2,213,500
4. Arctic Ocean ............ 3,782,000
5. Central Asiatic basin ...... 1,547,000'
Drained by the chief river systems in Africa.
1. into Atlantic Ocean.
a. from west coast ...... 1,600,000 <, ft() 000
6. into Mediterranean .. 700,000 > W |
2. into Indian Ocean ................ 250,000 j
Drained by chief systems in North America.
1. into Atlantic Ocean.
a. from east coast ----- . . 425,000 \ i Q-TK nnm
b. into Gulf of Mexico .. 1,550,000 / J y ' uul I
2. into Arctic Ocean .......... ! ..... 1,250,000 \ 3 ' 710 ' ( 4 ' 040 ' 0<
3. into Pacific Ocean ............. ... 485,000 J
Drained by chief systems in South America,
1. into Atlantic Ocean.
a. from east coast ...... 4,375,000 -. , , P A nnn o non nnn
6. into Caribbean Sea . . 105,000 \ .......... 4,480,000 2,020,001
Total drained by river systems .............. 22,255,000
Estimated area of Australia (river systems not known) ............ 3,000,000
Area of West Indian, Pacific, and other islands not included ...... 1,130,000
29,245,000
Add area drained by river systems ................ 22,255,000
Total area of land on the earth 51,500,000
55. From this large area a certain portion must be deducted as
receiving no rain, and therefore admitting of no drainage. Thus, in
the northern part of Africa and in Arabia, nearly 6,000,000 of
square miles of country receive either no rain, or so little as to in-
volve no surface drainage ; and in Central Asia another area of more
than 2,500,000 square miles is in a similar condition. In America
there are also rainless regions, one on the coast of Peru and Bolivia,
another in Mexico, and a third on the northern coast of South Ame-
rica at Venezuela, amounting in all to nearly 1,000,000 square miles.
LAKES.
37
But, if we deduct these areas (making in all 9,500,000 square miles),
we still have as much as 20,000,000 square miles drained by small
streams, and not forming part of the principal river basins.
56. The lakes or inland seas, chiefly of fresh water, either not
communicating at all with the ocean, or only communicating by
rivers, come next under consideration. By far the most extensive of
them occur in North America ; but there are also considerable areas
of land thus covered in the old world, and others whose level is far
below that of the adjoining sea, and which would be covered by
water if the evaporation were not greater than the supply from rain.
The existence of lakes has little reference to absolute elevation, and
they are due either to the form of a river-bed, expanding at some
point and containing the water thus introduced, the velocity of the
stream being diminished or destroyed ; or else to the filling with
water of some natural hollow, sometimes by springs, but more
generally by streams, the supply from which is greater than the
evaporation.
The principal North American lakes are five, and they together
cover an area of more than 120,000 square miles. Their dimensions
and elevation above the sea will be found expressed in the following
table :
Total |
length in
Brit. sta.
miles.
Mean
breadth in
Brit. sta.
miles.
Mean
depth in
feet.
Elevation
above the
sea in feet.
Area in
square
miles.
460
90
900
596
42,000
Lake Michigan and Green >
Bay /
480
80
1000
578
32,000
275
92
1000
578
27,500
Lake Erie and Lake St. -i
dair J
300
46
84
565
11,500
Lake Ontario
205
40 .
500
232
7,200
120,200
Besides these, a vast multitude of others exist in the northern
parts of the same continent, some of considerable magnitude, and
many of them the centres of basins of drainage of a wide extent of
country. On the western side of the Rocky Mountains, in Mexico,
and in various parts of South America, are also remarkable lakes,
some being very large, others only covered with water occasionally
during periodical inundations ; and others again, as the Lake Titi-
aca in the Bolivian Andes, presenting a broad sheet of water at an
elevation of many thousand feet above the sea.
57. The lakes of Europe and Asia are smaller in extent than those
of America, but not less interesting in their associations. The
Caspian Sea and the Sea of Aral occupy the lowest part of a vast
space, whose whole extent is not less than 100,000 square miles,
38 PHYSICAL GEOGEAPHT.
hollowed out, as it were, in the central region of the great continent,
and, no doubt, formerly the bed of an ocean. The Caspian Sea has
the lowest level, its surface being 83 1 feet below the level of the
sea, its area 24,000 square miles, and its depth in some parts 600
feet. The Aral Lake is of smaller size, having an area of only
4500 square miles, and it is also much less deep.
Fi 2 The lakes in Asia Minor are
Depression of the Dead Sea. e ven more remarkable than these
in their considerable depression
below the sea-level, the Lake of
Tiberias being 466 feet below the
Mediterranean, or even more ac-
a. Level of the Mediterranean. cording to some travellers, and the
b. Position of Jerusalem. Dead Sea 1388 feet. The depth
c. Level of the Dead Sea. /. - T\ a a j
oi water in the Dead feea exceeds
in some places 300 fathoms. Some idea of the depression will be
obtained by looking at the annexed diagram, fig. 2.
There are large and somewhat important lakes in Central Asia, of
which the Lake Baikal alone has an area of nearly 24,000 square
miles. Other numerous sheets of water, generally of much smaller
size, are scarcely known to European geographers. The lakes of
Europe also are interesting, the largest of them, Lake Ladoga, having
about 1400 square miles of surface. The Swiss and Italian lakes are
of much more limited area, but are, some of them, at a considerable
altitude above the sea, and of considerable depth. Lastly, we may
refer to Africa and Australia as countries in which extensive tracts are
covered with water, although too little is known of their actual extent
to enable us to compare them with the lakes of America or Asia.
In Northern Africa the Lake Melghigh is 160 feet below the level of the Mediter-
ranean, and another lake near the Red Sea, in the country of Adel, has been
described as more than 600 feet below the level of the Arabian Gulf. It is not
unlikely that the great salt tracts in many places are the result of the evaporation of
sea-water left in hollows, and enclosed by some natural barrier.
58. Most of these depressed lakes contain water loaded not only with common
salt but with other soluble salts, especially of magnesia, the quantity of which is
sometimes exceedingly great. In the Dead Sea saline ingredients are present to the
extent of 26-^ per Cent., by far the larger proportion being chloride of magnesium.
A small lake on the steppes, east of the Volga, having an area of about 1 50
square miles, contains no less than 29-13 per cent, of solid matter, and supplies a
large proportion of the salt used in Russia. The salts are chlorides of potassium,
sodium, and magnesium, and sulphate of magnesia, according to the following analysis
by H. Rose:
Chloride of potassium 0'23
sodium 3 - 83
magnesium 1975
Sulphate of magnesia 5'32
29-13
LOW PLAINS. 39
59. The surface of land uncovered by water may be divided thus.
1st, low plains, or tracts of moderately unbroken country, whose
mean level is not many hundred feet above the sea even towards the
interior of continents, and is much less than that near the embou-
chure of the rivers that traverse them ; 2nd, high plains or table
lands, generally more than a thousand feet above the sea in the
interior, and rising at once many hundred feet even near the sea ;
and 3rd, mountain tracts, where the elevations above the general
level put on a distinct and abrupt character, whatever their actual
or relative elevation may be. The elevations that break the surface
of plains are called hills, also without much reference to absolute
elevation.
Regarded in this sense, not only every continent, but even every
part of a continent, and most islands of moderate size, can generally
furnish plains and plateaux, hills and mountains, although on care-
ful comparison, and when we understand the real physical value of
such modifications of the form of land, there will rise out of this
apparent confusion important and distinct systems connected with
changes that have taken place by the action of mechanical force
beneath the earth's surface.
60. The lower levels of the earth are sometimes merely spoken of
as plains, and sometimes as river- valleys ; but when presenting fea-
tures more distinctly marked, they are steppes or deserts, prairies,
savannahs, llanos or silvas. Amongst them are the richest and most
fertile districts upon the earth, and also the most hopelessly barren
and useless tracts that the imagination can picture. They include
the treeless expanses of one part, and the impenetrable forest-dis-
tricts of another part of South America ; the plains of Northern
and Eastern Europe yellow with ripe corn, and the Sahara of Africa
yellow also, but with the dry sand that fills the air and destroys
every form of vegetable or animal existence.
It would be impossible in a work of any moderate extent, even if
devoted entirely to the subject of Physical Geography, to enumerate
and describe all the moderately elevated plains of the earth ; and
here, where only a very general outline is attempted, such detail
would be quite out of place. We may, however, with advantage
speak of some of the more remarkable of the appearances they
exhibit, for " in every zone nature presents the phenomena of these
great plains, and in each they have a peculiar physiognomy deter-
mined by diversity of soil, by climate, and by elevation above the
level of the sea." * We may also add that, however little attended
* See Humboldt's " Aspects of Nature " (Ansichten der Natur, the third German edition of
which, with notes, has been admirably translated into English by Mrs. Sabine, and is recently
published), a work perhaps the most original and suggestive of any of the valuable contributions
to science made by its venerable and distinguished author. Frequent use will be made of it in
this chapter.
40 PHYSICAL GEOGEAPHY.
to, these portions of the earth are the most instructive, when pro-
perly known, in illustrating many points by which Geology derives
assistance from Physical Geography.
The plains of Northern Europe are extensive and well character-
ized, occupying more than two-thirds of the surface of the continent,
and extending eastwards from the German Ocean along the south
shores of the Baltic as far as the Ural Mountains, including Holland,
North Germany, and the whole of European Russia. The Asiatic
low lands are even more extensive ; the plain of Siberia reaching
across to the Pacific, and from the highlands of Asia to the Arctic
Ocean ; those of China, Hindostan, and Independent Tahtary, like-
wise occupying large tracts. Africa also presents in its turn tracts
of low land, one of which, at least, is of vast extent, and characterized
by the most complete sterility, the Great Desert or Sahara, occupy-
ing an area of nearly three millions of square miles, and enjoying a
smaller share of the gifts of nature than any other portion of the
globe of equal magnitude, although by no means uniformly barren.
61. The districts thus affording few or no real elevations of con-
siderable amount are not all perfectly level, since a large portion
consists of rolling or hilly land, generally more picturesque and
interesting, and often more valuable than the rest. The land pre-
senting this intermediate condition, however, is not very easily de-
termined, and there are no calculations at present to be depended on
by which we can tell the limits either of the actual or relative capa-
bilities of the heaths of Europe, the steppes of Asia, or the deserts
of Africa. It may be sufficient to state that with the exception of
the table land of France, and Central Germany, and the moun-
tain districts of the Alps, Pyrenees, and Carpathians and Scandi-
navia, the whole of Northern Europe, whether fertile or barren, and
whether flat or hilly, exhibits marks of recent marine action, so that
we may often perceive in places now not reached even by the rivers,
that there has formerly been a deposit of water-conveyed materials,
and also a wearing or denuding action of powerful marine currents.
62. The low plains of Europe include many river-valleys, en-
closed by high and mountainous ranges, but the larger portion is
not of this nature, consisting chiefly of open and heath-covered
tracts on the shores of the Baltic, embracing, as we have already
said, much of Prussia and Russia, and also of Denmark, and having
a mean elevation of about 360 feet above the level of the sea.
Far in the east of Europe, and on the borders of Asia, is the great
Aralo-Caspian tract, a part of which, the Kirghis steppe, occupies
nearly 15,000 square miles of almost unbroken surface, depressed
nearly 100 feet below the general level of high water in the ocean.
It is terminated by much loftier table lands occupying a principal
space in Central Asia, but these decline towards the Arctic Ocean,
LOW PLAINS.
41
descending to the plains of Siberia, whose elevation is probably
nearly the same as, though somewhat greater than, that of the
European plain. On the south-eastern side of the same lofty range
the alluvial tracts of China occupy 300,000 square miles, while on
the southern side of the Himalayan chain the plains of India
extend, watered by the Ganges and Brahmapootra. Between China
and India we have the low valley of the Irawaddi, as large as the
whole of France ; and on the west of India, the Punjaub, and the
great Indian desert with the valley of the Indus, reach almost to
Beloochistan, low lands also extending towards the Persian Desert
and Arabia, which are separated from the low table land or Desert of
Africa by other, but higher plateaux.
63. The Sahara, the widest extent of low plains in the great con-
tinent, reaches from the rocky country beyond the valley of the Nile
to the shores of the Atlantic, a distance of not less than 2650 miles,
and its width varies from 700 to 1200 miles. Its surface is generally
naked, hard sandstone rock, or loose sand, with intervening portions
covered by gravel or rounded pebbles ; here and there a little earthy
matter or salt is mingled with the sand ; and fertile spots the oases
of the desert watered by springs, are met with at distant intervals.
The largest of them is about 100 miles in length, and from one to
fifteen miles broad. Throughout the greater part of its extent this
desert is probably very little raised above the level of the Atlantic,
and some parts seem actually below that level. No rain falls in
the district, and there is, therefore, no natural drainage.
64. The New World presents very large tracts of low land only
recently emerged from the ocean floor, each of the vast rivers which
characterize that continent running through a plain known by some
distinctive name. Thus, the Amazons waters a tract measuring not
less than 1500 miles in length, and varying in breadth from 300 to
800 miles (comprehending an area of 1,200,000 square miles), almost
covered with gigantic and unbroken forest, and hence called silvas.
Over this tract the quantity of rain that falls during the wet season
is larger than the annual fall in any other part of the world.
The pampas are treeless plains, occupying about 2000 miles of *
country, and extending from the forest desert of the Amazons to
the southernmost limits of South America, with a breadth of from
200 to nearly 500 miles, presenting in this range a great variety of
surface, climate, and vegetation. The country gradually rises from
the Atlantic shore to the foot of the Andes, and, roughly estimated,
may be considered as including nearly 1,000,000 square miles.
The llanos are also treeless plains, and extend along the banks of
the Orinoco, for the most part within the tropics, but their extent
is not more than half that of the pampas : during one half of the
year they are covered with grass, and for the rest desolate.
42 PHYSICAL GEOGRAPHY.
65. The basin of the Mississippi, the greater part of which has
a mean elevation of about 500 feet above the level of the sea, con-
tains gigantic prairies and savannahs, which form such characteristic
features of North American scenery. These occupy a space of
nearly 1,000,000 square miles ; so that, on the whole, more than
one-fourth part of the area of the two Americas is only just removed
above the level of the sea, and is drained by four principal rivers,
the Amazons, the Plata, the Orinoco, and the Mississippi, and their
tributaries. The plains of smaller extent, of which the number is
of course exceedingly great, do not appear in this calculation.
In addition to the large low tracts already mentioned, there can
be little doubt that others, of great extent and low elevation, remain
to be discovered in South Africa and in Australia.
66. Elevated plains are phenomena by no means so frequent on
the earth, or so extensive as those low plains we have been consi-
dering. The most remarkable, for their extent and influence on
the physical features of the globe, are those of Central Asia, Mexico,
Quito, part of South Africa, Abyssinia, Hindustan, Spain, Bavaria,
and France. The following table will give an idea of the relative
importance of some of these :
Estimated area Mean elevation
in square miles. in feet.
Plateau of Auvergne (Central France) 18,000 1,087
Bavaria 8,000 1,663
Castille (Central Spain) 1 00,000 2,239
Iran (Persia) 60,000 2,500
Mysore (Central India) 56,000 2,942
Caraccas (South America) 5,000 3,070
,, Gobi (Central Asia) 600,000 4,220
Popayan 2,000 5,756
California (the great basin) 150,000 6,000
, Abyssinia (round lake Tzana) . . ? 6,076
South Africa (Orange River) ? 6,395
Abyssinia ( Axum) ? 7,034
Mexico 50,000 7,483
Quito 5,000 9,528
Province de los Pastos 4,000 10,231
Thibet 50,000 11,510
LakeTitiaca 30,000 12,853
Arabia also exhibits table-lands of some extent and considerable
elevation, and there are many others not mentioned in the table.
67. Very incorrect ideas have been entertained of the extent and
elevation of lofty plateaux in most parts of the world, and the areas
approximately given in the preceding table, of which the plan and
most of the details are copied from Humboldt,* can only be regarded
as useful guides marking some limit. The usual character of these
districts is greatly dependent on the mountain-chains with which they
are always associated, either directly or indirectly ; and the fact of
* "Aspects of Nature," Eng. tr. vol. i. p. 78.
PLATEAUX AND MOUNTAIN-CHAINS. 43
the existence of such plains often merely intimates in reality that
there has been a broad and deeply seated axis of elevation ; that the
mountain-chain parallel to the principal direction of the plains exists
as a group of ridges rather than one single main elevation ; and that
we are in the vicinity of places where the fundamental forms of
land and the direction of its distribution may fairly be looked for.
Viewed in this light, they are instructive and suggestive, and in all
the higher problems of Physical Geography must be regarded with
great interest.
68. The determination of the mean height of continents or portions of them is equi-
valent to finding the centre of gravity of the masses of land they present above the sea,
and an enumeration of the volume of each and its effect on the whole forms a good
comparative estimate of the true importance of mountain-ranges and plains.
The position of the centre of gravity or the mean height of all the solid parts of
the earth's surface above the sea has been estimated by Humboldt at about 1000
feet, that of all Europe 671 feet, Asia 1132 feet, South America 1151 feet, North
America 748 feet, and the two Americas together 940 feet.
The effect of the plateau of Spain on all Europe is estimated at 36 feet, and that
of the whole chain of the Alps only 20 feet. In Asia the great central plains are
estimated to contribute 120 feet of elevation to the mean. It should be understood
that these results can only be regarded as approximate, and that the calculations give
a maximum limit. (" Cosmos," vol. i. p. 293.)
69. The mountain-chains of the earth can only be conveniently
regarded in this slight sketch of physical phenomena so far as their
uniformity of direction, their physical character and conformation,
and their mass, give them importance by connecting together the rest
of the land on the globe.
If the student will examine a terrestrial globe, or even a good
map of the world, he will recognise two main directions along which
the principal mountain-chains are grouped, and also a number of
transverse spurs proceeding from them. In the Old World (Europe,
Asia, and Africa), the space between two such lines forms a belt,
commencing in Europe with the Pyrenees and the plateau of Spain,
and in Africa with the Atlas Mountains, and continuing towards the
east till they meet in Western Asia, after which they are both continued
together further east, terminating finally on the shores of the Sea of
Okhotsk and the coast of China. In the New World, a similar belt
reaches from the north-western extremity of North America, and ex-
tends to the very southernmost point of South America. Within the
wide embrace of the enclosing ridges of each of these mountain-chains
are contained most of the lofty plains already alluded to ; and between
their flanks and the sea, but sometimes also enclosed within them,
are the lower plains and river valleys. They mark out the great
features of the globe ; and in their own detail, and in the chains
which spring from them and are connected with them, we may read
the history of the world ; since all we know of its present structure,
and all our means of knowing its past history, is dependent on the
44 PHYSICAL GEOGEAPHY.
successive and slow but irresistible upheavals that have lifted these
masses from the general level of the water.
70. The ridges of the mountain-chains of the Old World are the
Alps and Pyrenees in Europe, the Atlas Mountains, and perhaps the
Mountains of the Moon in Africa, and in Asia, the Caucasus, a con-
necting link between Europe and Asia, the Hindoo Koosh, the great
Himalayan chain, and the chain of the Altai Mountains, with their
eastern extensions into China and Mancheu Tahtary. Many others
might be mentioned, but these are the most important, and involve
most of the points of chief interest. They include the most massive
as well as the loftiest mountain masses, the breadth of the chain
between Siberia and India being as much as 1500 miles, and the
extreme length about 10,000 English miles. The greatest heights
attained are in the Himalayan chain in about 80 east longitude,
and exceed 28,000 English feet above the mean level of the sea.
The position of the crest of most highly elevated land is between
81 and 118 east longitude; and thus it is that, while the mean
height of Europe is estimated at not more than 670 feet, that of Asia
is more than half as much again, notwithstanding the wide expanse
of low lands in Siberia, and large tracts in Western Asia actually
below the level of the ocean.
71. The mountains of America form a more simple and complete
chain than those of the Old World, but still present considerable dif-
ferences of breadth and height. The Andes of the south and the
Rocky Mountains of the north are connected by the lofty plains and
ridges of Mexico, and thus form an uninterrupted range, extending
for more than 60 n of latitude on each side of the equator, giving
for the total length of the line of elevation a distance of not less
than 9000 miles. The breadth, however, is rarely considerable ; and
although in North America the range divides, and its two principal
arms include a distance of 300 or 400 miles, the intermediate plains
are by no means so lofty as to affect the general mean elevation of
the continent, as is the case with the high lands of Central Asia,
and even those of Mexico.
72. All the mountains hitherto referred to form part of the main
chains ; but there are also others setting off from them, or, in some
cases apparently unconnected, and having a different principal axis.
Thus the Ural Mountains form a meridional chain quite distinct
from the main group across Europe and Asia.; and the coast-chain
of Venezuela and the mountain systems of Columbia and Guyana
in South America partake in some measure of the same character.
North and south chains in the Old World are also found in South
Africa and Madagascar, in India, in the peninsula of the Birman em-
pire, and in China ; while the principal chain in Australia, at least
on its eastern side, follows the same direction. The mountains of
MOUNTAIN RIDGES.
45
Brazil range nearly parallel to the east coast of South America, and
the Alleghanies to the corresponding coast of North America.
73. A diagram is subjoined (fig. 3), which shows the mean eleva-
tion of the principal mountain-ridges, and that of their culminating
Fig. 3.
Comparative View of the Crests and Culminating points of the principal Mountain-chains.
feet.
a a Crest of the Pyrenees 8000
bb Alps 7700
cc Andes of Quito 11,800
d d Bolivian Andes 15,200
ee Himalaya 15,700
feet.
a'PicNethou 11,168
b' Mont Blanc 15,743
c Chimborazo 21,420
d'lllimani 21,149
e Dhawalagiri 28,072
points. It will be manifest to the eye, that the Himalayan chain
(e e} is the loftiest in every respect, although the actual crest does
not range more than 500 feet above that of the Bolivian Andes
(d d). The latter mountains, however, extend only for a distance
of 500 miles, while the Himalaya group ranges through no less
than fifteen degrees of longitude, which, in latitude 30, is equi-
valent to upwards of 900 miles. Within the range of the Bolivian
Andes occurs the singular plateau of Lake Titiaca, at an elevation
of nearly 13,000 feet above the sea; and the next highest plain
is that of Thibet, amongst the Himalayan Mountains, its elevation
being between 11,000 and 12,000 feet.
74. The mountains of the earth are not all of them included in
these systematic and distinct groups, for we meet with many
striking deviations from the usual direction, and we also meet with
isolated peaks, rising suddenly and boldly from low plains or small
islands. The former are in all cases phenomena worthy of close
study, for the deviation from the prevailing direction will generally
prove to be the result of elevating forces, acting at some period
either long antecedent or subsequent to that of the main axis of
elevation, and thus serves to connect the present condition with
past history. Such isolated mountains are usually conical in form,
and present marks of having recently served as open vents, by which
burning and intensely heated substances, elaborated in the bowels
of the earth, are sent out into the air, and there enter into new com-
binations. Such cases are almost confined to a moderate distance from
46 PHYSICAL GEOGRAPHY.
a coast line, except, indeed, in the remarkable and recent volcanic
mountains of the Celestial Mountains (Thian-Schan), whose nearest
ocean is 1800 miles distant, and which is 1200 miles from any con-
siderable body of water. The grouping, position, and phenomena of
volcanoes will, however, demand further consideration in another place.
75. However sudden the transition may seem, we really pass very
naturally from the consideration of mountain-chains to that of
islands, which appear in groups of two kinds, the one fringing a
coast line, and manifestly having some relations of form to the
adjacent continent; the other kind including detached islands, far
removed from land, and either forming independent chains or being
isolated mountain-tops. Islands, in fact, are nothing more than belts
or detached portions of lofty plateaux, whose subordinate low plains
form the ocean bottom, and whose tops reach above the level of high
water. Similar prominences above the general level, which do not
quite reach that level, are called banks and shoals, of which examples
on a large scale are seen in the great Bank of Newfoundland, the
Agulhas Bank off the south coast of Africa, and the Chagos Bank,
amongst the coral of the Coralline Sea in the South Pacific.
76. Viewed in this light we may at once place as belonging to
the first or continental group, the vast series, commencing with what
has been called the Australian chain, or rather with New Zealand,
and continued by Norfolk Island, New Caledonia, and the New
Hebrides, the Salomon and Louisiada Archipelagos, and New
Guinea, as far as the Moluccas. This belt of islands is throughout
parallel to the coast line of Australia, and is continued by Timor,
Java, and Sumatra, the Nicobar and Andaman islands, parallel to
the Malayan peninsula and the island of Borneo. Another range
may be traced going northwards by the Philippine Islands, Formosa,
the Loo Choo Islands, and the Japanese Islands, to the Kurile
Islands and Kamtchatka, enclosing the Chinese and Japan Seas, and
in close parallelism to the east coast of Asia. The Aleutian Archi-
pelago is in a similar way parallel to the line of coast stretching out
between America and Asia; and a small range of islands may be
observed parallel to the coast of Russian America, reaching down as
far as Vancouver's Island.
Other principal continental islands are seen in the Gulf of Mexico,
where a line drawn through Portorico, San Domingo, Jamaica, and
Cuba to the peninsula of Yucatan, will be found parallel with the
north coast of South America and the east coast of Guatemala.
So, also, in Europe the coast of Scandinavia, the British Isles, the
islands of the Baltic, the islands between Spain and Italy, and those
in the Adriatic, as well as those in the Greek Archipelago, present
similar and sufficient examples ; and near Africa the Island of Mada-
gascar and the Sechelle group are of the same kind.
ISLANDS. 47
77. The islands not referable to existing continental land may
possibly in many cases be portions and indications of ancient land
now depressed below the sea-level. The wide tract in the Pacific
and elsewhere, occupied by coral, and presenting steep cliffs of that
substance, barely removed above the level of low water, is probably
of this kind ; and thus the Low Archipelago and the Society Islands,
with a multitude of other smaller groups between these and the
Caroline Archipelago may be, though apparent exceptions, only con-
cealed examples of the general principle. There are, however, some
other exceptions, referable chiefly to volcanic districts, and due
probably to local elevation in connection with earthquake and volca-
nic disturbances. St. Helena and Ascension Island, the Cape de
Verde Archipelago, the Galapagos Archipelago, and some others are
known to be of this kind.
78. It should not be lost sight of, in taking this view of the
physical features of the earth on a large scale, that the coast-lines to
which the chains of islands are parallel are not, either in the eastern
or western hemisphere, parallel to the chief axis of elevation. In
the Old World this is very apparent, and is exactly accordant with
another very striking fact already mentioned ( 40), namely, that,
while the direction of the belt of high land is nearly east and west,
all the projections of land towards the sea, and all the chief pro-
montories and peninsulas, run out almost due south. At present,
the meaning of this apparent discordance can be only suggested as
worthy of careful notice the explanation may appear hereafter.
79. It only now remains to consider the results of these investiga-
tions with regard to the forms of matter upon the earth. It might be,
and has been, inferred, from the relative proportion of the elementary
substances present at the surface, their ordinary combinations, and
a multitude of other facts well known, but which it has not been
possible to refer to in this brief survey of existing nature, that all we -
can discover consists of a mere oxidized film a crust formed on the
cooling of a mass of matter once existing in a state of igneous fusion.
This is the most natural and the first theory of "the earth, suggested
when a certain amount of general knowledge is brought to bear on
a group of phenomena of enormous extent and complexity ; but
whether such view is sound, whether, indeed, we can thus at all
explain many actual appearances consistently with known facts of
other kinds, it still remains to determine. We shall not here pur-
sue this subject further, but defer till a future chapter the general
considerations which the investigation is calculated to suggest.
.This " igneous theory" has been adopted and supported by almost
all the most eminent of modern geologists and physical geographers;
but still we venture to call upon the reader to suspend his judgment
on the matter till he has learnt the facts.
48 PHYSICAL GEOGRAPHY.
CHAPTER IV.
ON ATMOSPHERIC AND OCEANIC CURRENTS, AND ON CHANGES
OF THE TEMPERATURE AND ELECTRICAL CONDITION OF
MATTER AT THE EARTHS SURFACE.
80. WE have hitherto been considering the condition of matter
forming the earth's crust, as presented in a certain definite shape at
a given instant. We have also considered certajnjrje^which may
be regarded as causes of change, but nothing has been said of
change itselfj and in advancing to this, which is perhaps the most
important department of Physical Geography in relation to Geology,
we shall find it convenient to recognise changes of two J^nds : the
one, a mere movement of particles without any modification of the
mass, or the changa. of pl,ac_observed by the particles of air and
water when set in motion and seen in some mineral substances during
decomposition ; and the other, a distinct and mechanical alteration
in the form or position oTtne solid matter, as induced by the rub-
bing, grinding, tearing up, and rolling or carrying along of earth,
mud, or stones. In the present chapter we shall consider only the
^former kind of changes, and these no more than as they really affect
_ the latter kind. In other words, we shall consider the air and water,
and their movements, as agents of mechanical change in hard rocks.
81. The earth, constituted as we know it to be, and revolving
round its own axis, and also round the sun, which is in some way
an exciting cause of light, heat, chemical action, and electricity, the
different parts of the surface are exposed periodically to the action
of these rays ; and as different substances and different forms of
matter are variously acted upon by the .same amount of exposure,
there is constantly a circulation of the atmosphere produced,
accompanied by heat, and conveying along not only heat, but a
large quantity of moisture, over the earth. There is also a regu-
larly alternating exposure to the stimulus of light, and a similar
daily and even hourly change in the electric state of the air and
earth. The mutual action of these changes, and causes of change,
complicates so greatly the actual phenomena of what is called
weather, that it is proverbially the thing of all others least to be
depended on, and in most temperate climates has come to be
regarded as governed by no laws yet ascertained, and affording no
appearances by which we can predicate future consequences. Per-
haps the simplest and most satisfactory method to adopt in this
place will be, first, to discuss the relations of the atmosphere to
water, or the appearances sometimes called aqueous meteors ; then,
COMPOSITION OF THE ATMOSPHERE. 49
the movements of the air, especially those chiefly referable to simple
and known causes ; and, lastly, the results of the movement of
masses of air differently charged with aqueous vapour, and in
different electrical conditions, when either impinging upon other
masses of air or moving over irregular surfaces of land. Under
these three heads may be brought most of those facts of meteorology,
the knowledge of which is essential to the geologist.
82. The atmosphere presents a mixture of gases, of which oxygen
and nitrogen form the principal part ; but, although the proportions
are nearly invariable, the gases do not form a definite chemical
compound. It may be considered, that pure dry air contains in 100
parts by weight,* 23 parts of oxygen, and 77 parts of nitrogen gas,
the proportion hardly varying to the extent of one percent, under any
known circumstances. Ordinary atmospheric air contains, in addi-
tion, about five parts in ten thousand of carbonic acid and carburetted
hydrogen gases, besides a very variable, and often rather consider-
able, proportion of aqueous vapour, and other substances, which are
usually regarded as impurities, but some of which, as ammonia, seem
very essential to vegetation, and are probably always present.
83. The air being highly elastic, its density is greatest at the
earth's surface, and at the height of about 2 f miles (11,556 feet)
the density is halved, or one volume is expanded into two, so that
at such an elevation the barometer (which measures the density of the
air. by finding the length of a column of mercury effecting the same
pressure, or balancing the pressure of the air) only shows a height
of one half that which it showed near the sea-level. The density
is again halved at about every 12,000 feet of additional elevation,
and at -an altitude of 45 miles the air would scarcely exhibit any
sensible density. It probably extends much further, but is certainly
limited, as, at the height of about three diameters, or 24,000 miles,
the centrifugal force would counterbalance the force of gravity.
84. If the atmosphere were everywhere of the same density as at the earth's sur-
face, its height under ordinary conditions, the barometer standing at 30 inches, would
be about 5-208 miles (26,500 feet); and as 100 cubic inches of air, deprived of
aqueous vapour and carbonic acid, at the temperature of 60 Fahr. and under pressure
of 30 inches of mercury, weigh 30*83 grains, we can determine the weight of the
whole body of pure dry air to be about 4,845,210,000,000,000 tons.
But in estimating the mass of the atmosphere, we must also take into account many
other substances generally present. Thus there is a certain amount of aqueous
vapour, very variable in different places, but measurable on a general average. So,
also, there is a sensible proportion of carbonic acid, carburetted hydrogen and am-
* The following is the composition of dry air by volume; the proportion of aqueous \apour
being too variable to be worth inserting:
Nitrogen 7912,
Oxygen .
Carbonic acid 4 > 10,000
Carburetted hydrogen . .
Ammonia Trace.
GRAHAM'S "Chemistry," second ed. p. 336.
50 PHYSICAL GEOGRAPHY.
monia, and a trace of many other substances. These altogether will appear as follows,
separating the oxygen and nitrogen, and estimating the absolute weight in tons :
Weight in tons avoirdupois.
Nitrogen 3,750,813,700,000,000
Oxygen 1,094,396,300,000,000
Water 50,000,000,000,000
Carbonic acid 3,037,200,000,000
Carburetted hydrogen 1,000,000,000,000
Carbonate of ammonia 250,000,000
Various substances 50,000,000
Total 4,899,247,500,000,000 tons.
Under the last head, u various substances," are included sulphuretted hydrogen,
sulphurous, sulphuric, hydrochloric, and nitric acids, the odoriferous principles of
plants, the miasmata of marshes, various gases liberated in manufactories or by volca-
noes, besides potash, soda, lime, magnesia, iron, manganese, &c. The estimate of
the quantity of water is very doubtful, but is based on the only calculations that have
yet been made.
85. It is owing to the chemical condition of the air, as a mixture
of dry gases with aqueous vapour, and to the never-ceasing changes
in temperature and electrical state thus induced, that we owe the
most remarkable of its phenomena. It is, however, well ascertained
that, notwithstanding the constant absorption of many of its parts
by organized beings, often to an enormous extent, the relative
proportion of the principal gases is very permanent, as air taken
from various parts of the earth, and from various altitudes, has been
found to present no appreciable differences in this respect. The
quantity of oxygen varies slightly in different seasons, and is rather
larger near the surface over the sea than on land.
86. Humboldt* has mentioned as the principal features of a
general descriptive picture of the atmosphere, 1st. Variations of
atmospheric pressure ; 2nd. Climatic distribution of heat ; 3rd.
the humidity of the atmosphere ; and 4th. its electric tension.
Under these heads it will be convenient to consider the facts that
bear on Geology.
87. The pressure of the atmosphere is simply the gravitation
of the whole mass of matter of which it is made up to the whole
mass of the earth. On an average of years it is the same in similar
climates at equal distances from the surface, but exhibits many
periodic and temporary oscillations. It becomes gradually less at
greater heights, as the mass of the atmosphere which presses is there
less. The pressure is the same in all directions, as that of any gas
or fluid must necessarily be ; and thus, though equivalent to about
fifteen pounds on every square inch of surface, it is not felt unless the
air on that surface is removed. The pressure has been hitherto most
conveniently measured against a column of mercury or other fluid,
* See " Cosmos," Sabine's translation, first edition, vol. i. p. 307.
PRESSURE OF THE ATMOSPHERE. 51
and it is found that about 30 inches of mercury, or 34 feet of water,
balance that of the whole atmosphere.* When from any local or
temporary cause of change on the same horizontal plane, or by any
elevation above that plane, the pressure is altered, that of the column
of mercury or water corresponding to it must be altered likewise ;
and thus the fluid in the barometer falls or rises as the pressure of
the air diminishes or increases, f Careful and tabulated records of
the nature and amount of barometric change exhibit three kinds of
these oscillations, viz. diurnal, annual, and irregular. The daily
oscillations present two maxima (one at about 9 h. A.M., and the other
about 10^ h. P.M.), and two minima (at about 4 A.M. and 4 P.M.),
which within the tropics are attained with almost perfect regularity,
undisturbed by storm, tempest, rain, or earthquake, at all elevations
from the level of the sea up to 13,000 feet. Towards the poles, and at
great elevations in temperate climates, this regularity is diminished,
and at length lost, or even perhaps inverted. The amount (or ampli-
tude) of the oscillations varies greatly, but is most considerable near
the equator, amounting there to about ^th of an inch.
88. The second kind of barometric oscillation is that observed
during the successive months of the year. In warm climates north
of the equator the mean pressure diminishes gradually from winter
to summer throughout the year, on the east coast of the great
continent from December to June, in India and at Cairo from
January to July, and in the West Indies from January to August,
the range being about 0'63 inches. In the north temperate zone
there are two minima, one near the time of each equinox, the
summer maximum being, however, lower than that of winter.
89. The irregular oscillations of the barometer are far less readily
explained and described than those periodic ones we have been con-
sidering. They depend on certain winds, on geographical position,
on the fall of rain, and on the electric tension of the atmosphere. The
former conditions will be best understood by reference to the sub-
joined table of the mean barometric pressure under different winds
in the neighbourhood of London ; and although anomalies some-
times occur, especially in the interior of continents, it may be con-
cluded that the barometer is generally highest, cceteris paribus, when
* Regarding the atmosphere as a mixture of gases, the nitrogen gas exerts a pressure equi-
valent to 23-36 inches of mercury
Oxygen gas 6'18 ,,
Aqueous vapour 0*44 ,,
Carbonic acid gas 0*02 ,,
Total 30-00
t In the so-called aneroid barometer (a barometer without fluid), the pressure of the air is
measured by the elevation or depression of the surface of a closed metallic vessel exhaused of air.
The pressure of the air being marked at a given time, any alteration is indicated by the move-
ments of the surface, and communicated by wheels marking the change on a dial by an index.
52 PHYSICAL GEOGRAPHY.
winds blow from the pole, and from the interior of continents, and
lowest when they come from the equator or from the sea.
A table of this kind is called the barometric wind-rose for the
place in question. The following is the barometric wind-rose for
London :
North 29-890 inches.
North-east 29'949
East 29-879
South-east 29796
South 29700
South-west 29-734
West 29-814
North-west 29'844
Mean 29-826 inches.
90. Geographical position, or position with reference to the vicinity
of the sea, wide tracts of desert, lofty mountains or extensive pla-
teaux, produces great modifications in the pressure of the atmosphere,
and therefore in the height of the barometer, so that the total mean
amplitude or range of the barometer during the whole year, or the
summer and winter halves of the year, varies extremely in different
districts, being greatest, so far as observations show, in Iceland, where
the annual range amounts to 14137 inch, and smallest at Batavia,
where it is only 0*1173 inch. It will be understood that the actual
range on particular occasions is often very much greater than these
figures show, the winter range being generally higher than the
summer.
91. The temperature of the atmosphere is greatest at the earth's
surfa'ce in any district, and diminishes at the rate of about 1 Fahr. for
every 350 feet of elevation near the earth, but not so rapidly at great
altitudes. At a certain height, however, the region of perpetual
congelation is reached in every climate ; and if the mountains are
sufficiently lofty this is manifested by their snow-capped summits in
the middle of summer. Generally the snow line, as this limiftis
called, is at the height of 15,000 feet at the equator,* 3800 feet at
60 latitude, and only one foot at 75, but there are infinite local
modifications of the general law, one of the most striking occurring
in the Himalayan mountains, where the snow lies on the southern
declivity at about 15,000 feet, although on the northern, which might
have been expected to show the coldest temperature, it is not met
with till we reach 20,000 feet. The causes of this decrease of tem-
perature in the upper parts of the air are, 1st, that the air in these
regions is expanded, and the quantity of heat in a given area near
* In South America, according to Pentland, the snow line, which is about as high as the
summit of Mont Blanc (15,750 feet) at the equator, actually ascends more than 2500 feet as we
advance southward until it attains the maximum elevation of nearly 18,500 feet not far from
Quito.
PRECIPITATION OF WATER FROM THE AIR. 53
the surface is, therefore, distributed over a much larger area as we
ascend ; and, 2nd, that a great part of the heat of the atmosphere is
obtained by contact with the earth's surface, the sun's rays being
absorbed but little while merely passing through the air. The tem-
perature of the air, as dependent on that of the subjacent earth,
varies, of course, according to climate and season.
92. The condition of the atmosphere with regard to moisture
varies very greatly at different hours and seasons, and in various
places ; but we may consider generally that dry air of a given tem-
perature is capable of holding in suspension a certain limited quan-
tity of aqueous vapour, and that when the temperature is diminished
the capacity for retaining water is also diminished. When, therefore,
warm air fully charged with vapour comes in contact with a cold
surface, or with a cold stratum of air, it is chilled, and part of its
vapour must be precipitated ; either as dew on some solid substance
present to receive it ; or in small drops or globules of water often
still retained in the form of visible vapour, either as mist or fog ; or
else as clouds wafted along by winds, and depositing their load at
a great distance from the spot whence it was evaporated. It may
well be supposed that over the sea and large fresh water lakes the
air is always in a state of saturation. On coast lines also it re-
mains almost fully charged with moisture, but in the interior of
continents the conditions are often very different ; so that there are
some districts having seasons of incessant rain, others where rain
may fall at any time, and others again where no rain falls, and
where the air is, therefore, invariably dry. The air at the surface,
especially in temperate climates, is, however, by no means always in
the same state as that a few hundred feet above ; and the meeting
of two currents high in the heavens will often produce a change
not indicated by instruments or appearances near the earth.
93. The quantity of water distributed over the earth's surface
afjffcr being conveyed through the air in clouds is very large ; far
larger, indeed, than could be supposed without careful investiga-
tion. Tt is the actual quantity of rain falling in a given time that
enters into such calculations, and for the purpose of measuring its
amount various instruments have been contrived. These show,
1st, that while mountain districts on the whole receive a larger
quantity of rain during the year than plains, yet in any place of
moderate elevation more rain falls near the surface than above it ;
2nd. that a larger quantity falls on coast lines on the western side
of great continents in the temperate zones than on the eastern side
or the interior, but in the tropics more on the eastern side j and,
3rd, that more rain falls in tropical than in temperate climates,
though the number of days on which rain falls is greater in the
latter, than the former, case. In the tropics, even in the rainy
54 PHYSICAL GEOGRAPHY.
season, the rain falls chiefly during the day j but in temperate
climates, indifferently by day or night.
94. Within the tropics there is a rainy and a dry season ; and
in the tropical countries of the New World the mean annual fall is
about 115 inches, while in the Old World it is not more than 76
inches, giving a general mean for the tropics of 95 1 inches. In
the temperate zone of the northern hemisphere there is less difference
between the eastern and western continents, the mean being 37
inches, but the extremes in each case exhibit very wide ranges. In
the south temperate zone the fall averages 26 inches only, and in
the frigid zones it has not been measured with sufficient accuracy,
but is very much smaller. It would appear that between three and
four times the total quantity of water retained at one time in the
atmosphere in the form of invisible aqueous vapour or cloud, falls
annually on that portion of the earth's surface marked by the pre-
sence of land ; a striking proof of the frequency of change in the
condition of the atmosphere in this respect, and the rapid transmis-
sion of aqueous vapour through it.
The following table will give the distribution and absolute quantity of water falling
on the land in different districts of the earth according to the latest and best estimates.
It must be understood that in the two frigid zones, and, indeed, in the temperate
zones, the estimate includes the whole fall of water whether as rain or snow :
Area of land Total annual rain-fall
in sq. ms. in cubic feet, in tons weight.
N. and S. Torrid zone 1 9,400,000 4,282,750,000,000,000 ] 1 9,1 77,000,000,000
N. Temperate zone.. 25,150,000 2,160,500,000,000,000 60,000,000,000,000
S. Temperate zone .. 4,350,000 261,500,000,000,000 7,275,000,000,000
N. and S. Frigid zone 2,600,000 70,250,000,000,000 2,000,000,000,000
General total 51,500,000 6,775,000,000,000,000 188,452,000,000,000
95. The electric tension of the atmosphere is constantly undergo-
ing great disturbance, being affected by every change in its humidity
and temperature. The phenomena of storms, not merely of thunder,
but of rain and wind, are intimately connected with, and dependent
on, these modifications. Even the deposit of dew, the gentlest of atmo-
spheric changes, as well as the formation of mists, fogs, and clouds,
and the falling of rain, snow, and hail, must be regarded as both
consequent upon and causing great electric disturbance. When
serene the atmosphere almost always indicates positive electricity.
96. Violent storms occur frequently in the tropics, and are called
hurricanes, tornados and typhoons, but they are generally much
limited in extent and direction. They advance from one point with
a powerful and rapid gyratory motion combined with a direct pro-
gress ; but while the latter is often not more than eight or ten miles
an hour, the former is sometimes 50 or 60 miles, or even more, pro-
ducing destruction in the course of the storm from the irresistible
WINDS. 55
force acquired by such extreme rapidity. All of them are referable
to electrical changes, which have been generally induced by great
and unequal distribution of heat. (See 103.)
97. Winds or currents of air are produced whenever the atmo-
sphere is set in motion, in consequence of one part being displaced
by some local cause and another part rushing in to supply the
vacant place. Winds keep the atmosphere permanently in a state
of complete mixture of the component parts. They help to purify
it by removing miasma and exhalations locally injurious, but ad-
mitting of such dilution as to be ultimately harmless : they favour
arid assist in the fecundation of plants by the distribution of pollen :
they modify and equalize the temperature of various parts of the
surface : they convey clouds, and thus distribute moisture, and
render the interior of continents fertile but sometimes they carry
with them poison and death, for they bear along the insects and the
blight that often destroy the hopes of the husbandman, and the
fever that baffles the skill of the physician.
98. Generally if two districts are unequally heated a cold wind
will set in near the surface from the less heated to the more heated
district, while a corresponding current in the opposite direction
takes place in the upper regions of the atmosphere. Thus, when
the sun shines during the day, and land and water are equally
exposed to its influence, the land is more heated than the water,
and a cool breeze is soon felt setting in landwards ; while in the
evening when the sun has set, and the greater radiation cools the
earth sooner than the water, the converse takes place, and in this
way is readily explained the phenomena of land and sea breezes,
and the numerous apparent anomalies observed in local prevalent
winds.
99. The trade-winds are likewise periodical winds, occurring near
the tropics in the open ocean. The portion of the earth near the
equator is the hottest part of the globe, and the air over it is there-
fore more heated than elsewhere, while on the other hand the
regions near the poles are exposed to perpetual cold. There is
thus induced a constant cool current near the earth, setting south-
wards from the north pole, and northwards from the south pole,
and constant warm currents above this cooler one, proceeding from
the equator towards each pole. These would be distinctly observ-
able everywhere, but for the revolution of the earth round its
axis from west to east, which alters such currents, and produces
a tendency to north-east winds in the northern, and south-east in
the southern hemisphere. But now comes into play another result
of the condition of the atmosphere, for the wind advancing along
the surface from the poles northwards or southwards, must, as it
approaches nearer the equator, arrive successively at points which
56 PHYSICAL GEOGRAPHY.
move more rapidly than itself, as the air at the equator and poles,
in each case, moves once round the earth in every twenty-four hours,
but near the poles the circle of its motion is very small, while at
the equator it is enormously larger. Thus it results, that at certain
latitudes the winds blow constantly from the east, instead of north-
east, and this direction is pretty uniform between the twenty-eighth
parallel on each side of the equator, except that near the equator
(between the third and ninth parallels of north latitude) there is a
region of calms and variable winds, alternating often with violent
storms.
100. The north-east trade-wind is less steady in the Atlantic than
the south-east, probably because of the more confined condition of
the northern part of that ocean. In the Pacific this wind does not
seem to extend beyond about 140 west longitude, that is as far as
there is open sea. The multitude of islands and coral banks in the
rest of that portion of the tropical sea, and the land of the great
continents, both in the Old and New World, preventing these regular
winds from being perceived, and introducing a multitude of local
and distinct currents.
101. The trade-winds, interrupted in their course by the distri-
bution and form of the land in the Indian Ocean, pass there into
periodical winds called monsoons, which blow from the middle of
April to the middle of September in one direction, and from
the middle of October to the middle of March in the opposite
direction. North of the equator the former are south-west, and the
latter north-east winds, and south of the equator the summer mon-
soons are south-east, and those of the winter north-west. The
change takes place gradually, beginning in the upper regions of the
atmosphere and being often accompanied by storms. Monsoons of
less perfect character occur on the coast of Brazil, in the Gulf of
Mexico and elsewhere, and other periodical winds known by various
names are common on most shores.
102. Beyond the limits of the trade- winds in the temperate
climates of both hemispheres, wind more commonly blows from
some one direction than any other, and every country has thus what
are called prevalent winds. South-west and north-west winds pre-
vail near the surface in the north and south temperate zones re-
spectively, and in each case there are return-currents in the upper
regions of the atmosphere.*
103. Storms of the nature of hurricanes are rarely met with
beyond the torrid zone, and they chiefly occur or commence near the
tropics. In the northern hemisphere, the region of the West Indies,
and in the southern, the south-western part of the Indian Ocean,
* The mean direction of the wind deduced from various observations in the north temperate
zone is thus stated by Kamtz : England S. 66" W. : France, S. 88" W. ; Germany, S. 76 W. ;
Denmark, S. 62 W. ; Sweden, S. 50 W., Russia, N, 87 W., and North America, S. 86 W.
STORMS. 57
or rather the islands there situated, are the principal foci whence
have proceeded the most violent storms on record. They move on
the north side of the equator from east round by the north point
of the compass to west (from right to left), and in the southern
hemisphere in the opposite direction (from left to right). In the
former district the storm season is in the autumn months, extending
through August, September, and October, and including, though
rarely, June and July. The storms range from latitude 10, to 50
north, and longitude 50 to 100 west. In the Indian Ocean they
prevail chiefly from December to April, occurring also, though
seldom, in May or November, and in that part of the world they
range from the coast of Madagascar to that of Australia. The ordi-
nary hurricanes seem to extend over a breadth of from 500 to 1000
miles in the Atlantic, and of about 600 miles in the Indian Ocean.
Storm waves and temporary currents (storm-currents) seem often to
accompany a hurricane at sea, the former being true waves raised
above the level of the sea, and carried along with the storm in its
onward course, and the latter consisting of a rotating stream in the
centre of the storm. Torrents of rain and explosions of thunder,
with vivid flashes of lightning, have been generally observed to
accompany hurricanes. The typhoons of the China sea have the
usual range of latitudes for storms (10 to 50 N.), and extend from
the coast of China to longitude 150 east. They occur only once in
about three or four years. The deserts of Asia and Africa, some of
the plains (llanos) of South America, and part of Australia, are
exposed at times to hot stormwinds, which are of the nature of
tornadoes, and are very destructive.
104. By CLIMATE (as Humboldt has expressed in his Cosmos, vol.
i. p. 312, English translation) we understand "all those states and
changes of the atmosphere which sensibly affect our organs : tem-
perature, humidity, variation of barometric pressure, a calm state
of the air, or the effects of different winds, the amount of electric
tension, the purity of the atmosphere, or its admixture with more
or less deleterious exhalations, and lastly, the degree of habitual
transparency of the air, and serenity of the sky, which has an im-
portant influence, not only on the organic development of plants,
and the ripening of fruits, but also on the feelings and whole mental
disposition of man." Many facts bearing on climate have been
already touched on, and we have here chiefly to consider the modifi-
cations of it dependent on position, and the various changes (not
merely possible but certain) that would ensue from an alteration in
the absolute proportion of land and water, and the relative position
and arrangement of the land that may at any time exist.
105. Climate in this sense is chiefly determined by averages of
temperature, not only of the year, but also of the, different parts of
OF THF.
rrw T.Vtt P ST r less
perfectly stratified."*
160. The icebergs appear to be conveyed from the cold shores of the Arctic Ocean
by a current, which, proceeding along the shores of Greenland, approaches the Gulf
Stream on the eastern side of the great Bank of Newfoundland, near latitude 44
north, and between longitude 45 and 48 west. The direction of this current is
south-west. Its temperature in the month of May is 43 to 47 Fahr. while a little
to the west the water is from 61 to 63 Fahr. Another current coming along the
coast from Labrador, brings icebergs which pass by the Straits of Belle Isle, within
350 miles of Quebec, and to this the low summer temperature of the Gulf of St.
Lawrence is due. Thus on the 10th of July, the temperature at the surface being
50 Fahr. that at 50 fathoms "was found to be below 34, and still further to the
south at Tadousac, the water of the ocean at a depth of 90 fathoms, was 35 Fahr.
At the junction with the Gulf Stream, the icebergs diverge towards the east, but some,
notwithstanding, cross its course, which has a mean breadth of 280 miles, and
descend thence as far as 38 north latitude.
Boulders of large size of porphyritic rock (pegmatite), gneiss, &c., which are sup-
posed to have been conveyed by floating ice from the antarctic land, have been found
in the South Shetland Islands, which are entirely basaltic.*)'
161. Another result of the action of ice is mentioned by Sir
Roderick Murchison in his " Geology of Russia." He says, " To-
wards the mouth of the Dwina, and about 110 versts above
Archangel, a white carboniferous limestone (see diagram fig. 13) oc-
Fig. 13.
Ridges of Blocks on the Dwina.
cupies the bank in horizontal layers, the edges of which are partially
covered with mud and sand. The limestone is best seen when the
water is low, as at the period of our visit. About thirty feet above
the summer level of the stream, the terrace on the river-side is
covered for two or three versts by a band of irregularly piled, loose
* Lyell's " Principles," ante tit. p. 228.
t " Voyage of the Bonite," Geologic et Mineralogie.
ACTION OF FROST. 83
and large angular blocks of the same limestone, arranged in a long,
uniform ledge, the surface of which slopes both to the river and to
the roadway, so that the view of the stream is shut out from the tra-
veller by this ledge. In other words, these materials (all purely local)
constitute a broken ridge of stones between the road and high-water
mark. A woodcut will best explain these appearances (see fig. 13),
showing (a) the ancient hillocks of sand above the road-terrace, which
is partially covered with water at high inundations, (b) the ridge of
broken limestone, (c) the sloping river-bank. The occurrence of
these supra-riparial ridges of angular blocks in situ is thus explained :
When the Dwina is at its maximum height, the water which then
covers the edges of the thin beds of horizontal limestone (d) pene-
trates into its chinks, and, when frozen and expanded, causes con-
siderable disruptions of the rock, and the consequent entanglement
of stony fragments in the ice. In the spring the fresh-swollen stream
inundates its banks (here very shelving), and upon occasions of re-
markable floods so expands that in bursting it throws up its icy
fragments to fifteen or twenty feet above the highest level of the
stream. The waters subsiding, these lateral ice-heaps melt away,
and leave upon the bank the rifted and angular blocks (6), as evi-
dences of the highest ice-mark. In Lapland Mr. Bohtlingk has
adduced some extraordinary examples of this sort of glacio-fluviatile
action ; for he assures us that he there found large granitic boulders,
weighing several tons, actually entangled and suspended like birds'
nests in the branches of pine-trees at heights of thirty or forty feet
above the summer level of the streams." *
162. Among the results of that kind of atmospheric and aqueous
action described in the preceding paragraphs of this chapter we may
mention, 1st. the rough and broken surface observable in countries
where naked rocks appear at the surface ; 2nd. the soil derived
from the pounding up of the broken fragments in other districts ;
3rd. the bold and scarped appearance, and the low, muddy, or
shingly tracts observable on the coast ; 4th. the gradual silting up
of river beds and lakes ; in the former case altering the original
course of the stream, and forming a new one, and in the latter
entirely obliterating the lakes ; 5th. the accumulation of detritus
at the mouths of large rivers, and the formation of oceanic and river
deltas ; and, 6th. the distribution of large quantities of mud,
stones, sand, and other transported material on the sea-bottom,
either near or at a distance from the land. It remains to consider,
briefly, the extent to which such action has been traced in cases not
yet alluded to, and to observe the laws according to which the
matter deposited seems to be arranged.
Enough has been already said in previous paragraphs concerning
* " Geology of Russia in Europe and the Ural Mountains," vol. i. p. 506.
84 PHYSICAL GEOGRAPHY.
the first, second, and third of the results mentioned above, which
are chiefly or entirely destructive, and what now remains has
reference chiefly to the silting up of rivers and lakes, and the form-
ation of deltas these being the reproductive effects of aqueous
action and to the arrangement and distribution of materials thus
accumulated.
163. We have first to take into account the actual amount of
reproductive effect produced by running water in some particular
cases of streams and lakes ; and here, as before, we cannot do better
than give one or two statements carefully compiled from the best
authorities, and refer to books already quoted for further and more
detailed illustrations.
An admirable example of the deposit of mud as new land is seen
at the head of the Adriatic Sea, where no tides or strong currents
interfere with the gradual accumulation of river mud, and which
receives two considerable rivers, the Po and the Adige, draining a
wide range on the south side of the Alps and passing through the
great plains of Lombardy. "From the northernmost point of the
Gulf of Trieste to the south of Ravenna there is an uninterrupted
series of recent accessions of land, more than 100 miles in length,
which within the last twenty centuries have increased from two to
twenty miles in breadth." " It is calculated that the mean rate of
advance of the delta of the Po on the Adriatic, between the years
1200 and 1600 was nearly eighty feet a-year, and the mean annual
gain from 1600 to 1804 was upwards of 220 feet;" and we may men-
tion, as other results, that Adria, a sea-port in the time of Augustus,
that gave its name to the adjacent gulf (Adriatic), is now upwards
of twenty miles inland.
164. Rivers exhibit the accumulations of mud due to their
passage over a country, partly by this increase of land along a coast
line, but partly also in the elevation of their actual bed and of the
adjacent valley, and the filling up of the lakes through which they
pass. The result rapidly increases as the work goes on, as will be
understood by referring to the an-
nexed diagrams, where fig. 14 repre-
sents a section across a river course at
Mud deposited by floods when a stream tlie commencement of the deposit, the
runs on a low bed through a valley. river (6) then running through the
lowest part of a valley (a a), between high lands (d d). When the
stream is flooded the mud will be partly deposited over the whole
section, but a large proportion of the turbid water will flow off,
draining back as the stream recovers its natural level. When, how-
ever, the stream has in the course of time raised its bed by successive
deposits (see fig. 15), and the floods cover the adjacent country, the
water will be kept back in the hollows at a a, till evaporated, and the
RIVER DEPOSITS. 85
whole of the mud must be left behind. Thus the valley is gradually
elevated so long as the same causes continue to operate. In the case
of larger rivers, as the Ganges, the Mississippi, and others, the thick-
ness of the alluvial bed near
the river mouth becomes very d
considerable, and even at a dis- '^^~^----^^<^uiiHg lm
tance of a hundred miles or more
Up the Stream, and in the Open Mud deposited by floods when a river has
f . , , ,' 1-1,1 f raised its bed.
plains through which the river
makes its way, is estimated in the Mississippi at more than 250 feet.
All this has, of course, been accumulated by the reproductive action
of the river itself.
165. When a triangular area of land is added to the previously
existing shore, whether of the sea or a lake, the base of the triangle
extending towards the open water and the apex being up the
stream, it is called a delta, from the form of the Greek letter of that
name. Such deltas accumulate often rapidly, and mountain lakes
are not unfrequently entirely filled up by them in the course of
time. In the Lake of Geneva the Rhone enters as a turbid stream,
charged with a large quantity of mud and detritus, but goes out at
Geneva perfectly transparent. The whole of the mud is left near the
head of the lake, which has thus become very shallow, and the new
matter now annually added, is thrown down upon a slope about two
miles in length. The higher part of the Lake of Como is nearly
filled up, and the lake divided into two, by the detritus transported
by the Adda and Mera ; the Lago Maggiore by the Ticino \ and
many others in like manner. Some large inland seas, as the Baltic,
are sensibly reduced in depth by the accumulations of mud that take
place in them, and the Mediterranean is gradually encroached on by
many of the rivers that empty themselves into it. Of these the Nile
and the Rhone are the most important, but large results are pro-
duced by the infinite multitude of small streams entering along its
coast line.
166. The Delta of the Nile now commences about 100 miles in
a direct line from the Mediterranean, and is at least 230 miles in
breadth ; but the chief effect of the mud brought down by this
river, and deposited near its mouth, is not so much seen in the
extension of the delta seawards as by the elevation of the land over
which the periodic floods of the Nile extend, and which is therefore
gradually increasing in extent. The mud of the river consists of
nearly one moiety of argillaceous earth, together with variable pro-
portions of carbonate of lime, carbon, silica, magnesia, oxide of iron,
and carbonate of magnesia. Each year produces a thin additional
layer, not thicker, on an average, than a sheet of thin pasteboard.
The whole area of the delta ; with the exception of a few sand-hills
86 PHYSICAL GEOGRAPHY.
and artificial tumuli, offers a perfectly level plain, intersected in
every direction by channels. The slope or fall of the Nile from
Cairo is about one in sixteen thousand, equivalent to 15".
The following analysis of the dried mud of the Nile has been recently made by M.
Lassaigne, and is quoted from the Quarterly Geological Journal, vol. v. partii. p. 20.
Silica 42-50
Alumina 24-25
Magnesia 1'05
Peroxide of iron 1 3-65
Carbonate of lime 3'85
Carbonate of magnesia 1*20
Humic acid 2'80
Water .1070
100-00
167. The delta of the Rhone forms a range of marshes bordering
the Mediterranean between Marseilles and Cette, and includes about
320,000 acres. A large part of it is called the Camargue, and in-
cludes about 180,000 English acres, of which a considerable portion
is covered to a small depth by water. The ancient and original
mouth of the Rhone was on the western side of this area, and the
actual embouchure has advanced more than eight miles towards the
sea since the commencement of the Christian era. Several towers
and other buildings mark distinctly the progress thus made.
168. The Danube, another principal river of Europe, emptying it-
self into a nearly closed sea, presents a large delta, the river dividing
into four principal branches at about fifty miles from the coast, the
two extremes of which are about fifty- four miles apart at the extre-
mity. The Volga affords a similar instance of the accumulation of
mud, as there are only a few feet "of water in the Caspian Sea for
a distance of fifty miles from the mouth of that river.
169. The Oceanic deltas, of which in Europe the Rhine is the
most extensive, offer examples of the reproductive effect of river
currents on a very large scale. The present head of the delta is
about forty-five miles from the nearest part of the Zuyder Zee, and
more than ninety miles from the general coast line. The whole of
the coast line of Europe, however, from Calais to the entrance of the
Baltic, requires to be considered in reference to this considerable
and important delta ; and, as the subject has been ably treated, and
at some length, by M. Elie de Beaumont,* we must refer to his
account for the details, without which it is not easy clearly to
understand the nature and cause of the coast changes constantly
going on. It appears that the whole plains of North Central Eu-
rope have been originally covered by sand and gravel, but chiefly by
the fine sand seen on the coast of Flanders. On these have been
* " Le?ons de Geologic pratique," vol. i, p. 253, et seq.
OCEANIC DELTAS. 87
deposited the accumulations of mud brought down by the Rhine,
and the numerous sinkings for wells in various parts of Holland
and Belgium show that such accumulations amount in places to
several hundred feet.
170. The waters of the Rhine, as of other rivers,, have been
examined with reference to the average quantity of solid matter
they hold in suspension at different periods of the year, and it was
found, by two sets of experiments made by Mr. Leonard Homer at
Bonn, that the quantity brought down was about 400 tons weight
per hour.
171. The Granges, including the Bramahpootra, presents a delta of
gigantic dimensions, and is well worthy of notice. It commences
220 miles from the sea, and its base line extends for 200 miles,
including the wide tract occupied by the waters of the river and the
different branches, of which there are eight principal and an almost
infinite number of smaller ones. These are constantly shifting, and
the extremity of the delta altering in position ; and the quantity of
mud poured into the Bay of Bengal is so large that the sea does not
recover its transparency for sixty miles from the coast. The general
slope seawards is gradual, and, with the exception of a deep hollow
about fifteen miles in diameter, is not more than sixty fathoms
deep at a distance of a hundred miles out. The quantity of mud
brought down by this river has been estimated at about 500,000
cubic feet per second during the four months of the flood season, and
about 50,000 cubic feet only per second for the rest of the year ; the
average weight of mud during the rains being 4^th part of the
whole weight of the water. The total annual discharge would thus
be nearly 6,368,000,000 tons, and the average quantity of mud held
in the water about -^^th part by weight.
172. The Mississippi commences to bifurcate at nearly 300 miles
from its principal embouchure, and the head of its delta is about
200 miles from the sea. Its breadth is considerable, and it presents
on the whole an area at least one third larger than that of the Nile.
It is essentially a projecting delta, being bounded on the east, west,
and south by the sea, and advancing steadily outwards, at a rate of
about one mile in a century, or fifty feet per annum. The solid
matter contained in the muddy waters of the river is nearly ten
times as great as in the Rhine, averaging for the year xrVflth of the
whole weight of the water. The mean depth of the mud and sand
in the delta is estimated at not less than 500 feet, which, allowing
3,000,000 cubic feet of mud to be deposited each year, would
require about 85,000 years for the formation of the present area of
mud.* It is, however, probable, that the rate of increase has not
* " Lyell's Principles," ante cit, p. 218. The figures are somewhat altered to include recent
observations.
PHYSICAL GEOGRAPHY.
always been the same, so that the present result may have been
obtained in a much shorter time.
173. In addition to the material thus conveyed along by water a
considerable quantity is deposited from calcareous and other springs.
Several remarkable examples of this kind are quoted by Sir Charles
Lyell, in one of which there is a thickness of 200 or 300 feet of
travertin of recent deposit, while in another a solid mass 30 feet
thick was deposited in about twenty years. He also states " there
are countless other places in Italy where the constant formation of
limestone may be seen," while the same may be said of Auvergne
and other volcanic districts. In the Azores, Iceland, and elsewhere,
silica is deposited often to a considerable extent. Deposits of as-
phalt and other bituminous products occur in other places.
174. We now come to the mode of distribution of the material
removed, deposited, or otherwise accumulated in the manner above
described. In the case of a cliif or hill the annexed -diagram (fig.
16), will give some idea of the kind of process that takes place by
the joint action of the atmo-
Fig. 16. ^f sphere and water. The degrad-
ation at first results in the
formation of a talus of large
blocks (a) thrown down and
irregularly heaped. After this
a further amount of similar
action breaks up these blocks
Deposit of Detritus from a hill or cliff talus. . n / i i
into smaller fragments, which
arrange themselves, as at b, in irregular parallelism with the former;
these again are succeeded by another series, c, and these by others,
until at length ordinary rain or tidal action removes a part in the
shape of mud.
175. When the material thus broken up is exposed to the action
Fig. 17. of running water, a
*j ^ ^p certain amount of
sifting takes place,
and the materials
are deposited in
horizontal
Structure observed in the accumulations made by running streams, degree of
rity, the finer and coarser portions being grouped separately. While,
however, the deposit on the whole is nearly horizontal, different layers
will present an internal arrangement of parts having reference to the
actual direction in which the deposit was made, as marked in the
diagram (fig. 17), where the direction of the current is marked by an
arrow, and the beds a, 6, have been deposited by an opposite current
ARRANGEMENT OF DEPOSITS. 89
to that which produced the earliest beds marked c, d. The bed d
marks a peculiar lenticular, or lens-shaped form, not unfrequently
seen, and due to a temporary and local cause often connected with
the presence of some organic body.
176. All deposits are not of the simple character thus indicated.
The results of the infiltration of water containing carbonate of lime,
silica, oxide of iron, and various soluble earthy salts, through such ac-
cumulations, does not fail to produce considerable change in the course
of time, and alternations of mere mechanical deposits with substances
once held in solution will modify the first appearance and itself
induce further change. The mud also deposited from the waters of
a river, or on a coast, will be of various degrees of coarseness in any
particular spot according to the mechanical force exerted, and every
change, however small, will be marked by a slight, but correspond-
ing alteration in the bedding ; thus, in a moderate thickness of
deposit we shall find a number of distinct
bands, as in fig. 18, one of clayey mud,
another of calcareous mud, another of sand,
another of pebbles, and so on. These will
have an arrangement without much refer-
ence to their relative specific gravity, ex-
cept in the case of each band of similar
materials.
177. But another real and great cause of difference in the deposits
made both by and in water, must be traced to the organic world.
Animals and vegetables inhabiting the water, or brought there by
accident, so often possess hard and indestructible parts that these
are constantly retained and preserved in mud, and not unfrequently
make up very important and thick masses with little or no ad-
mixture of foreign and inorganic substances. Thus, shells of all
kinds, particularly those exceedingly gregarious species common
either in fresh-water, or in the sea, will be amongst these deposits,
and they will also contain fragments of plants, both land and aquatic.
Certain plants, however, are more readily preserved in water than
others ; and these, of course, will be chiefly retained, while many
animals of low organization, such as those which secrete carbonate of
lime from sea-water and form for themselves stony habitations,
become permanent and important portions of the new condition of
things. Such animals can withstand the beating of the waves, and
their houses endure permanently as stony walls flanking extensive
lines of coast and numerous detached islands. The coral animal of
tropical and other seas is thus so dispersed in innumerable banks,
and often builds such massive walls, that it ranks amongst the most
effective causes of change, and requires some detailed explanation in
this place. The coral animals, which are chiefly occupied in the
90
PHYSICAL GEOGRAPHY.
formation of reefs, have numerous calcareous plates, and increase
with very great rapidity. In the seas where they build are also
many bivalve and univalve shells, which add greatly to the mass.
The reef-building corals do not flourish at a greater depth than
120 feet ; and though many species are found living much deeper
they rarely form considerable accumulations.
178. The appearance of a coral island is described by voyagers
as extremely picturesque. A ring of land (see fig. 19) a few
Fig. 19.
View of Whit-Sunday Island, an atoll in the Pacific. +4 1 U/W
hundred yards wide, and measuring from less than one mile to thirty
miles in diameter, rises barely above high water-mark, but is covered
by lofty cocoa-nut trees. Between these and the water is a beach
of glittering white sand, the outer margin of which is encircled with
a ring of snow-white breakers, beyond which again are the dark
heaving waters of the open ocean. The inner beach encloses the
calm, clear water of a shallow lagoon, resting for the most part on
white sand, and seeming of the most vivid green colour when the sun
is shining. " The ocean," says Mr. Darwin, " throwing its breakers
on the outer shore appears an invincible enemy, yet we see it re-
sisted, and even conquered by means which at first seem most weak
and inefficient. No periods of repose are granted, and the long
swell caused by the steady action of the trade wind never ceases.
The breakers exceed in violence those of our temperate regions, and
it is impossible to behold them without feeling a conviction that
rocks of granite or quartz would ultimately yield, and be demolished
by such irresistible forces. Yet these low irresistible coral islands
stand, and are victorious, for here another power, as antagonist to
the former, takes part in the contest. The organic forces separate
the atoms of carbonate of lime one by one from the foaming breakers,
COEAL ISLANDS. 91
and unite them into a symmetrical structure ; myriads of architects
are at work, night and day, month after month ; and we see their
soft and gelatinous bodies through the agency of the vital laws con-
quering the great mechanical power of the waves of the ocean, which
neither the art of man, nor the inanimate works of nature, could
successfully resist. 1 ' *
The structure of one of these islands will be understood by refer-
ence to the preceding sketch (fig. 19), and the accompanying section
(fig. 20). In the diagram fig. 20, a, a represents the narrow habit-
Fig. 20.
Section across an atoll or lagoon island.
able ring ; b, b, the lagoon, and c, an island rising out of the lagoon.
Fig. 21, represents an ideal section of an island on which coral is
supposed to have accumulated to a vast depth. See 239.
Fig. 21.
tkn illustrating the growth of deep Coral-banks by gradual depression of the land.
179. Coral reefs are of three kinds, one of which consists of
narrow strips not presenting any considerable depth, and forming a
fringe to the land in some tropical seas. The other two kinds are
farther removed from the shore, from which they are separated by a
canal or lagoon, and either encircle islands or exhibit nothing more
than the narrow belt of the reef itself. The first kind are called
fringing, the second encircling or barrier, and the third atoll-Jormed
reefs, the name atoll being given, in the seas where these islands
abound, to the circular reefs without high central land. Of these,
fringing reefs occur in the lied Sea, on the east coast of Africa and
Madagascar and the adjacent islands to the north, and in the Indian
Archipelago between the Bay of Bengal and New Guinea and as far
as the Solomon Islands, and they may be traced at intervals to the
south of the Society Islands in longitude 150 W., and northwards
through the Philippines. They also occur exclusively in the West
Indies. The barrier reefs and atolls^are found in the Indian Ocean,
the China Sea, off the east coast ~oT*Australia, and in the Caroline
Archipelago ; and a vast multitude of islands as far as the Low
" Journal of the Beagle," 2nd edit. p. 460.
PHYSICAL GEOGRAPHY.
Archipelago are built up in the same manner, the whole western
portion of the Pacific being sometimes called the Coral Sea from the
innumerable reefs and islands of coral that render navigation there
so dangerous. The absolute area of sea bottom thus occupied at
intervals by the work of one race of animals is so enormous that it
would be difficult to parallel it by any reference to any existing
mountain district,* and the actual magnitude of particular reefs is
not less remarkable. Thus, the barrier reef in New Caledonia is
400 miles long ; and on the coast of Australia the reef extends
for 1000 miles parallel to the shore, and at a distance varying from
20 to 60 miles from it. The Maldive Archipelago is 470 miles in
length, and has a mean breadth of 50 miles, and consists entirely of
atoll islands, the largest of which is 88 miles in length, and only
20 broad. The Chagos group is a series of submerged atolls, and
extends over an area of 170 miles by 80. The Laccadive group
measures 150 miles by 100, and is of the same kind.
180. We are not at present concerned with the important theory
of partial subsidence of large areas below the sea which the extent
and condition of barrier reefs and atolls has suggested, but without
any reference to this no one can help being struck with the vast and
almost unmeasurable extent of the influence here exercised by a
single race of organic beings on the great frame- work of the globe.
In a subsequent paragraph 239, some account is given of the reasons why a very
considerable and long-continued depression of the land must be assumed to account
for the great extent and thickness of the coral-reefs of the Pacific. It is hardly possible
to exaggerate the importance of these phenomena within the present range of latitude
to which the coral animal is confined ; but this does not extend more than two or
three degrees beyond the tropics, except in peculiar cases, where the water is warmer
than usual, as in the West Indies. Coral is now chiefly abundant in the western part
of the Pacific Ocean within the tropics, where most of the atolls and barrier reefs
are found. Whether under former conditions of the earth's surface there may have
been a difference in this respect, so that corals could attach themselves to shores in
our latitude, is a subject which will be considered in a future chapter when treating
of geological problems.
181. Nor are other and even much smaller animals withotrt some
means of producing results in mass. This has been remarkably
shown in the case of infusorial animalcules inhabiting rivers where
the tide periodically advances to a certain point and recedes, leaving
a space alternately occupied by fresh water and salt. Many minute
animals inhabiting the ocean and brought 'up by the tide are killed
at once when immersed in fresh water.
The following is the result arrived at by Ehrenberg, with reference to this subject.
It is taken from an abstract of a paper, originally published in the Proceedings of the
Berlin Academy, 1 843, and translated by the Author of the present work for the
Quarterly Geological Journal, vol. i. (1845), p. 252.
* From the southern end of the Low Archipelago to the northern end of Marshall Archipelago
is a distance of 4500 miles, in which as far as is known every island, with one exception, is atoll-
formed. The number of islands is so large that it has not yet been possible to estimate it
correctly.
INFUSORIAL DEPOSITS. 93
The minute microscopic animals of the sea extend up the bed of the Elbe, and this
is probably the case also in all rivers directly connected with the ocean, as far as the
ebb and flood of the tide are perceptible.
The flood-tide in the upper districts of the river, even where the salt taste is no
longer perceptible, as above Hamburg, does not consist merely of an accumulation of
the river waters, occasioned by checking its outflow, but is now proved to be due to
the direct introduction of the sea water, probably under the river water, and extend-
ing very distinctly as far as 80 English miles above the mouth of the river.
Since in the lower portion of the Elbe, the mud, consisting of a mass of clay and
slime, which often interferes with the navigation, only accumulates so far up as the
flood tide is perceptible, but above this point the bed of the river consists of pure
siliceous and other sand, it is evident that the cause of this singular phenomenon,
which has hitherto not been sufficiently explained, is principally owing to organic con-
ditions. It appears, in fact, that the mixture of river and sea water gradually kills
vast multitudes of the minute organic bodies, and causes them to fall to the bottom,
and form these accumulations.
The marsh land of the lower districts of the Elbe, below Hamburg, and, probably, of
all rivers flowing into the ocean, although considered as humus, does not merely, or even
chiefly, consist of matter brought down by the stream from distant regions, and still
less is it a local production of the minute animalcules existing in river water, but it is
to a very considerable extent derived from organic beings once existing in the ocean.
If we deduct the admixture of fine sand as a matter of iincertain origin, we shall
find, not only at Cuxhaven, near the mouth of the Elbe, but also at Gluckstadt,
that from one quarter to one third of the mass of fresh mud is owing to the influence
of marine animalcules, and that above Hamburg, as far as the flood-tide extends, the
proportion is about half as great, but it has been already shown that what appears
to be fine sand, may also, in a great measure, be an altered state of organic siliceous
shells.
Similar results were obtained from the examination of the mud in the lower dis-
tricts of other rivers emptying themselves into the Baltic. In the neighbourhood of
Hamburg, the thickness of this mud is 15 or 16 feet, and several low islands at the
mouth of the Elbe are entirely formed in this way, the actual proportion of the ske-
letons of the animalcules being equal to one-twentieth of the volume. There is little
doubt that this accumulation will be found to connect itself with the history of the
earlier deposit of the great tract of land, whose northern shore is washed by the Baltic,
and the eastern portion by the German Ocean.
\ 182. Accumulations of vegetable matter must in like manner be
/forming important deposits which will one day appear as beds of
coal or lignite, especially where swamps, turf-bogs, and other loca-
lities admit of the vegetable growth of each year being preserved.
It seems to be chiefly in temperate and cold climates that these phe-
nomena are most marked.
It is not necessary to detain the reader now with further details
of the influence of organic products on inorganic matter, but that
such influence is real and very extensive no one who is familiar
with existing nature will for a moment doubt. Every accumulation
of river mud and coast detritus must contain many fragments of the
animals and vegetables, chiefly aquatic, existing in the vicinity ; and
as these are greatly influenced by climate, present local distribution
of races, and past physical conditions on which this distribution
depends, each spot where such accumulations go on, must present a
history more or less complete of some part of the earth at one period
10,
94 PHYSICAL GEOGRAPHY.
of its existence. The multitude of such chapters of the long and
complicated history of the whole earth, that are in the course of time
stereotyped in beds of mud, and will hereafter form rocks and be
laid open to the naturalist and geologist, must, therefore, become
records of the present condition of organic nature ; and, however
sometimes mixed and confused, will be true and trustworthy docu-
ments by which to study the history of the past. Similar docu-
ments discovered now in rocks and properly studied and interpreted
are, and must be, the means of making out the true nature of the
earth's progress ; and these ancient records are generally available,
whether they refer to animals or vegetables to the highest or the
lowest forms of organization.
183. As a fit conclusion to the present chapter we append an
account of the views of Professor Edward Forbes concerning the
distribution of marine animals in depth, since it is only by a know-
ledge of the actual laws of this distribution, and their bearing on
the habits of animals generally, that any conclusions can be drawn
from the appearance of the remains of various species embedded in
aqueous deposits.
1st. Living beings are not distributed by chance in the bed of the
sea ; certain species inhabit certain localities according to depth, so
that the bed of the sea presents a series of zones or regions, of which
each one has its peculiar group of inhabitants.
2nd. The number of species is much less considerable in the deeper
zones than those near the surface. Vegetables disappear below a cer-
tain depth, and the constant diminution in the number of species of
animals indicates that the zero of animal life is not far distant.
3rd. The number of animal and vegetable species in the northern
seas is not the same in all zones of depth : it increases in the number
of identical or representative species as we descend. The law seems
to be that the parallels in depth below the surface correspond in
this respect to parallels of height above the surface, and have the
same relation to parallels of latitude.
4th. All kinds of sea bottom are not equally capable of supplying
nourishment for animals and vegetables.
5th. Banks of marine animals do not extend indefinitely, each
species living in a particular sea bottom, and being liable to extinc-
tion if the number of individuals should increase so much as to
modify the nature of the bottom.
6th. Animals inhabiting great depths have also a wide horizontal
range.
7th. Mollusks emigrate in the larva state, but perish at a certain
period of their existence, if they do not then find the conditions of
depth and sea bottom favourable for their further development.*
* Ed. New Phil. Journ., April, 1845.
95
CHAPTER VI.
REACTION OF THE INTERIOR OF THE EARTH ON ITS EXTERNAL
SURFACE.
184. THE subject that comes now before us presents series of
changes much more readily appreciated, and apparently more likely
to modify the earth's surface, than those considered in the preceding
chapter. It includes volcanoes and earthquakes, emanations of gas,
and jets of hot and mineral water ; and besides the great interest of
the phenomena involved, the subject is of essential importance in
enabling us to comprehend the general series of modifications of the
surface of our globe. Following the plan adopted in the last chapter
we commence with a scheme by which the reader will see at once
the bearings of the subject, and the general mode in which it will
be treated.*
/. Direct indications of subterranean cliange,
A. By gaseous exhalations, and bituminous and muddy eruptions. 185 188.
B. By thermal and mineral springs. 189 194.
c. By undulations of the earth's surface propagated beneath the surface.
a. Nature of earthquakes. 195 198.
6. Extent of districts subject to them. 199201.
c. Actual range of a single shock. 202 204.
d. Attendant phenomena of fracture, and elevation or depression of the
surface. 205209.
D. By volcanic eruptions.
a. Nature of volcanoes. $ 210 217.
b. Products erupted from volcanoes. 218220.
c. Districts presenting active volcanoes. 221 226.
d. Communication between distant volcanoes. 227 228.
//. Indirect indications of subterranean
A. By former alterations of level in volcanic districts. 230231.
B. By marks of extinct volcanic action.
a. In extinct volcanic cones. 232235.
b. In accumulations of known volcanic products, 236.
c. By alterations of level in districts not volcanic.
a. Elevation of various coast lines. 237 238.
b. Depression of large areas. 239.
185. Flames have in many places been observed to issue from the
ground from clefts in the earth, which appear to allow the escape of
gases from some depth. When such gases are carburetted hydrogen,
or hydrogen, they readily take fire, and long continue to burn.
* The authorities chiefly consulted in this chapter have been " D'Archiac's Histoire des pro-
gres de le Geologic," tome i. ; Bischof's "Geologic;" Von Hof's " Geschichte der Erdooer-
flache;" Lyell's " Principles of Geology;" De la Beche's " Manual," " Researches," and " How
to Observe ;" Beudant's "Geologic," Humboldt's " Cosmos " and "Aspects of Nature," and
Dr. Daubeny's " History of Active and Extinct Volcanoes."
96 PHYSICAL GEOGRAPHY.
When sulphuretted hydrogen, sulphurous vapours, or muriatic acid,
they are either not inflammable, or burn with a flame hardly seen by
daylight, and, therefore, not so likely to be noticed ; and when carbo-
nic acid, which is the most common, and is emitted in great abundance
in many places, they at once extinguish flame and destroy animal life.
Carburetted hydrogen has long been emitted from the ground, and is
actually used in China for culinary purposes and illumination ; and
recently gas obtained in the same way has been used in the village
of Fredonia in the State of New York, in America.
There are several places where this gas issues from the ground on the south of the
great chain of lakes of North America. Three miles south of Lake Erie, it issues
from a blue schist, and a bore-hole is sunk to about 23 feet in schists and bituminous
substances, whence the gas is conducted by tubes to a gasometer, and afterwards con-
veyed to different parts of the town.
In the neighbourhood of Newcastle-on-Tyne, in England, where the coal beds in
some places contain a large quantity of this gas, it is conducted from the deep work-
ing of the mines to the surface, and there burnt, merely to avoid the danger of its
escape into the works. It is evident, that in these cases, the depth from which the
gas is obtained is very small, but other examples are recorded where a constant ema-
nation occurs from great depths, and in the neighbourhood of volcanoes. Such are the
fumaroles (eruptions of aqueous vapour) and solfataras (eruptions of sulphurous vapours)
so often described, and the liornitos or little ovens of the Mexican volcanic plains.
186. Flames issue from the ground, unaccompanied by any true
volcanic phenomena, at what are called salses, at Sassuolo in the
Apennines, about mid way between the Adriatic and Massa on the
Mediterranean coast ; and many other similar appearances are de-
scribed in Tuscany. Eruptions of mud from small orifices, also called
salses, are described as occurring in Java, where gas at a high tempe-
rature, mingled with the vapour of water, has acted and continues to
act powerfully on the surrounding solid matters, disintegrating and
decomposing: them, and forming many new compounds, and sometimes
being accompanied by true eruptions of boiling acid mud.
Very remarkable and destructive floods of hot mud are on record, not only in Java
but in Peru, where in the year 1698, the volcano of Carguaraizo gave forth a torrent
of mud that covered nearly 80,000 acres of ground, and in 1797, an entire village
near Rio Bambo was buried under a similar mass. In most cases the mud itself has
certainly not been brought from any considerable depth, since it contains organic
matter, and abounds in the cases of infusorial animalcules.
Greece and Asia Minor, and also various districts in the Crimea,
have been found to furnish examples of a similar kind of subter-
ranean action, and it is supposed to occur in the bed of the sea of
Azof. At Carthagena in New Spain, in some parts of Hindostan,
and elsewhere, almost the same appearances are connected with
recent volcanic action ; and Humboldt suggests that they present
an image of the constant but feeble activity of the interior of the
globe. They are in some cases continuous and incessant, and in
others occur only at intervals of greater or less magnitude.
MUD VOLCANOES. 97
187. "The phenomena of mud volcanoes are deserving of more attention than geo-
logists have hitherto given to them ; their grandeur has been overlooked, because, of
the two phases presented by them, it is only the second, or calmer state, lasting for
centuries, which has been usually described ; but their origin is accompanied by
earthquakes, subterranean thunder, the elevation of great districts of country, and
lofty jets of flame of short duration. When the mud volcano of Jokmali, on the
peninsula of Abscheron, east of Baku, on the Caspian Sea, was first formed on the
27th of November, 1827, flames blazed up to an extraordinary height for a space
of three hours, and during the following twenty hours they rose about three feet
above the crater from which mud was ejected. Near the village of Baklichli, west
of Baku, the column of flame rose so high, that it could be seen at a distance of twenty-
four miles. Enormous fragments of rock, torn doubtless from great depths, were
hurled to a distance around. Similar fragments are seen around the now tranquil mud
volcano of Monte Zibio, near Sassuolo, in Northern Italy. For fifteen centuries the
Sicilian salse near Girgenti (Macalubi), described by the ancients, has continued in
the secondary stage of activity ; it consists of several conical mounds, from eight or
ten to thirty feet high, subject to variation both in form and height. Streams of
argillaceous mud, accompanied by periodical disengagements of gas, flow from very
small basins containing water, at the summits of the cones. In these cases the mud
is usually cold, but sometimes it has a high temperature, as at Damak in the province
of Samarang, in Java. The gaseous eruptions, which are accompanied by noise, vary
in their nature, consisting sometimes of hydrogen gas mixed with naphtha, sometimes
of carbonic acid, and even occasionally of almost pure nitrogen, as Parrot and myself
have shown in the peninsula of Taman, and in the South American volcancitos of
Turbaco."*
188. When large quantities of bituminous matter occur near the
earth's surface they occasionally yield naphtha springs, petroleum,
and other forms of liquid bitumen, and these if set on fire continue
to burn for a long time, and present on a small scale some of the
phenomena of true volcanoes. They have been designated pseudo-
volcanoes ; and a remarkable instance at Baku, near the Caspian Sea,
has been long known and frequently described. Similar examples
occur at Rangoon, near the delta of the Irrawaddi, and also in China,
in Japan, and in North America. The extraction of the bitumen in
many of these localities is a matter of economic importance, but we
are here only considering the facts as far as they relate to changes
produced at the earth's surface.
189. Eruptions of heated water are common in many volcanic
districts, but nowhere so remarkably as in the Geysirs, or boiling
fountains of Iceland, and we append in the next paragraph the latest
and most authentic account of these to which we have access. Other
cases of boiling springs have been described in Java, Manilla, and in
the circular island of St. Paul, in the East Indies, and also in the
volcanic regions of Central and South America.
190. In a plain about eight miles in breadth, extending from the foot of the
Blafyell to the sea-shore, and connecting itself with the flat moorland of the coast,
lie the springs of the Great Geysir, at the foot of a hill composed of slaty phonolite
and grey trachyte. According to all appearance, this plain, which has scarcely a per-
ceptible inclination to the sea, was once a broad fiord, reaching as far as the jagged
" Cosmos," ante cit., vol. i. p. 212.
98
PHYSICAL GEOGRAPHY.
mountains of the Yarthettur, and the Blafyellshalls. It is clothed with a thick green
carpet of meadow ground, and many larger or smaller springs wind like silver rib-
bons through the grass, sometimes hiding between high banks, then again coming
in sight. To the east and south-east, are seen ranges of flat hills and mountains,
among which can be distinguished the cone of Hecla ; on the opposite side, behind
the Langafyell, the Byarnefyell, higher and steeper, and mostly veiled in dark blue
clouds, clothed at its foot with grass, but at the top showing naked crags, on which
lie bare strata of trap-rock and palagonite. From a considerable distance the tra-
veller perceives, at the foot of the Langafyell, light clouds of steam rising out of the
ground, or sometimes thick columns of smoke whirling upwards in the air, but he
soon finds himself in the midst of a complicated system of boiling springs, which
break forth from a volcanic chasm, extending in the direction of north-north-east.
The valley of the Geysir is mostly filled with a new alluvium, which has here and
there undergone a subsequent elevation, extending northwards from the spring, in a
broad ridge. Through this soil, which has been gradually overlaid by a thick stratum
of siliceous sinter, the deposit from the springs, the Geysir bursts forth, and from the
horizontal beds of this deposit, there has formed in various proportions round the
The Geysirs of Iceland.
Geysir and smaller fountains, a flattened cone, in the midst of which is a perpendi-
cular cylindrical funnel of larger and smaller diameter. In ordinary circumstances,
the basin of the Geysir is filled with crystal-clear sea-green water, of the tempera-
ture of 180 Fahr., and it flows in three small channels over the eastern slope of the
cone. After some time, a sound, as of subterranean thunder, can be distinguished,
resembling that made by a volcano during an eruption, and then a slight tremulous
motion may be perceived on the rim of the fountain. When this has lasted some
seconds it ceases perhaps for a time, and then begins again with increased force, the
water in the basin begins to swell, and the surface becomes convex, and at the same
time great bubbles of steam rise to the surface and burst, throwing up the boiling
water some feet high. Then it is again still, and the whole fountain is enveloped in
THERMAL SPRINGS. 99
clouds of steam. This phenomenon is repeated at regularly recurring intervals of an
hour and twenty minutes to an hour and a half, perhaps for a day, until it suddenly
assumes a different character. A heavier thunder is heard below ; the water swells
violently, and begins to heave and dash in the strongest agitation ; and after a few
minutes, there shoots up a column of water dispersing at the summit into dazzling
white foam ; this has scarcely reached to a height of from 80 to 1 00 feet, when, before
its drops have had time to fall to the ground, a second, and third follows, and rises
still higher. Larger and smaller jets now shoot forth in all directions, some sideways
in arches, others perpendicularly upwards, with a loud hiss like that of a rocket ;
enormous clouds of steam roll upwards ; then comes a loud detonation from below,
followed by another column of water higher than any of the preceding ones, and
mingled with stones ; and after the phenomenon has lasted for a few minutes, the
whole falls and vanishes like the fantastic pageantry of a dream. Before the clouds
of steam have had time to disperse, or the boiling water to run off the sides of the
cone, the basin which had seemed full to the brim, appears almost dry, the water
having sunk nearly 3 feet.*
191. Besides these sources of water at a boiling temperature, there
are also many instances in various parts of the world where water
rising in springs from below the stratum of invariable temperature
(see 111), conveys to us some information concerning the condition
of the interior, and usually has a temperature greater in proportion
to the depth of the source, if that can be traced. Such water also
comes to the surface charged with mineral substances, including gases,
which are often sufficient to give a very distinct character to the water,
rendering it, indeed, useless for ordinary culinary purposes, but valu-
able in medicine, and in the treatment of various diseases. Thermal
and mineral springs, as such sources are called, have thus become of
considerable economic interest, and are noticed and described with
some attention. Any spring of water containing mineral substances
in solution or suspension, and having a uniform temperature through-
out the year, above the mean temperature at the surface, may be
considered to belong to this group, but those only that present dis-
tinct and striking phenomena can be noticed in the brief sketch here
attempted.
192. Generally, but not always, hot springs are situated near
either recent or ancient volcanoes, as those on the slopes of Etna and
Vesuvius on the one hand ; and those at Tbplitz, Pesth in Hungary,
Auvergne, and the Euganean hills, on the other. Those in the Eifel,
and the Pyrenees, and others in the Alps, besides many more in simi-
lar districts, have evidently relation to some local conditions inde-
pendently of present volcanic force. Many, indeed, as the hot springs
at Bath, those of Buxton, and elsewhere in Derbyshire, and others,
cannot be traced at all to volcanic agency, commonly so called, but
they exist where great mechanical disturbances and disruptions have
occurred in the rocks through which the water passes.
193. Mineral waters having a temperature above the mean annual
temperature of the surface generally contain nitrogen, sulphuretted
* Von Waltershausen, " Skizze von Island."
100
PHYSICAL GEOGRAPHY.
of
an
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EARTHQUAKES. 101
hydrogen, or carbonic acid gases, and a variable proportion of certain
salts, of which muriates, carbonates, and sulphates of lime, magnesia,
soda, or potash, are the most active and abundant. They also con-
tain iron very frequently, and occasionally a small proportion of
some one or more of the following substances : ammonia, iodine,
bromine, fluorine, phosphorus, lithia, strontia, barytes, and man-
ganese. As affording the best means of forming an idea of the relative
proportion of these, a table is appended selected from that given by
Dr. Daubeny in the 2nd edition of his work on Volcanoes.
] 94. Besides those in the table may be mentioned the springs of St. Gervais, in
Savoy, which have a temperature of 106 Fahr., and contain 45^ grains of sulph. soda
and lime, and mur. soda and magnesia in each pint of the water; the spring of Acqua
della Bolenta, in Piedmont, temperature 107 Fahr. ; those of Abano, near Padua,
121 ; the Baths of Nero, also 121; spring at Ischia, varying from 83$ to 944 ;
various springs in the north-western provinces of Spain, ranging from 192 to 107;
others, in Southern Spain (Murcia) 104 to 113, Fahr.; several in Portugal from 75
to 95; and the following, also in Portugal, all above 100 Fahr. Monqao, near Ucana
(province of Minho), 109 ; Torres Vedras (Estremadura), 1 1 1; Lagiosa, near Viseu
(Beira), 120 ; Guimarens (Minho), 138; Chaves, near Braganza (Tra loa Montes),
141-8; and San Pedro Dosul near Viseu (Beira), 153.
In Greece, there are springs near the Pass of Thermopylae, whose heat is 1 1 3,
besides several others of lower temperature ; and in European Turkey, several groups,
one of which, near the Balkan, has a temperature of 1624.
Several warm springs have been discovered in North America, ranging from 70 to
1 1 0, Fahr., and there are certainly many much hotter which have not yet been ascer-
tained with sufficient accuracy to enable us to record them here. South America
exhibits numerous examples of similar phenomena, and they have been met with in
several islands of the Australasian Archipelago.
In addition to the substances mentioned in the preceding table, many of the warm
springs contain silica in considerable abundance.
k- 195. In various parts of the world, and at various times, there
nave been felt movements of the superficial crust of the earth, con-
sisting for the most part of one or more rapidly succeeding undula-
tions, accompanied often by sounds, and traceable distinctly in some
particular direction, chiefly linear, taking time to proceed from one
point to another. They are called earthquakes, and are recognised
phenomena in all volcanic countries, but occur also in districts which
present no mark whatever of volcanic origin, and no trace of volcanic
products. The undulations vary greatly in number and frequency,
both on each particular occasion of earthquake disturbance and in a
given time, but they seem much more frequent and more widely
traceable than has been generally supposed.
1 96. The movements of the earth in those shocks that have been felt in volcanic
countries, are described as of three kinds, namely
1st. T/te Undulatory Motion, which takes place horizontally, and heaves the
ground successively upwards and downwards, proceeding onwards in a uniform
direction.
2nd. Tlie Succussive Motion, in which the ground is heaved up in a direction more
or less approaching to the perpendicular, as happens in the explosion of a mine.
3rd. T/ie Vorticose Motion, which seems to be a combination of the two preceding
102 PHYSICAL GEOGRAPHY.
ones, several undulations taking place contemporaneously, and thus interfering one
with the other, so that during its continuance, the surface of the land is tossed about
somewhat in the same manner as that of the sea is during the prevalence of a storm,
when a number of billows, travelling in different directions, strike one against the
other, and thus produce every possible complexity of movement.
Of these three kinds of earthquake-shocks, the first are the most common and the
most harmless. From the second, that of succussion, more is to be apprehended ; but
the vorticose movement is the one which has been felt in the most violent and disas-
trous catastrophes on record.* (See 209.)
197. A hollow noise often accompanies or precedes the shock of
an earthquake, but is occasionally heard some time after it. At
other times no sound whatever has been recognised. Thus, the
great earthquake of Eiobamba in 1797 occurred without noise ; and
on the other hand, there was heard on one occasion in the Caraccas
a loud noise resembling thunder without any earthquake ; but at the
same moment that a volcano in the Island of St. Vincent, more than
600 miles distant, was pouring out a prodigious stream of lava.t
These phenomena of sound are described as very striking, and also
very variable, but they all seem to prove that the cause of the dis-
turbance with which they are connected is very deeply seated, and
extends very widely over the internal surface of the earth's crust.
198. Observations made on slight earthquake shocks in Northern
Europe are highly interesting as showing something of the extent and
nature of such undulations. We are indebted to M. Perrey for col-
lecting and comparing the accounts of a number of observations made
in Europe and Asia Minor, and other records have been kept of the
movements felt in Scotland during several years past. M. Perrey
has succeeded in obtaining accounts of m> less than 3432 distinct
earthquakes that have occurred in Europe and the adjacent parts of
Asia and Africa, between the commencement of the fourth century
and the year 1844 inclusive. Of these the dates of nearly 3000 are
known and they have been found to be thus distributed in the
different months of the year :
December 300 \
January 336 [
February 27 5 )
March 265 x
April 235 I
May 210)
June 201 N
July 216 f
August 236 )
September 221 x
October 252 [
November 232 )
v 2979
or 911 in the winter month
or 710 in the spring do.
or 653 in the summer do.
or 705 in the autumn do.
* Daubeney on Volcanoes, 2nd edition, p. 509. t "Cosmos," vol. i. p. 1Q5.
J " Histoire des Progres de la Geologic," vol. i. p. 606.
SLIGHT EARTHQUAKE SHOCKS. 103
There have thus been 1,712 recorded eruptions between the 1st of October and the
31st of March, and only 1,335 from the 1st of April to 30th of September. This result is
sufficiently remarkable, and it also appears that in each particular year the same order
was observed; but it must not be regarded as important with respect to the general
phenomena of earthquakes in other districts, beyond illustrating the fact that some
seasons and periods are more subject to disturbances than the rest of the year, or, in
other words, that earthquakes exhibit a certain amount of periodicity.
199. In addition to all known volcanic districts, which are with-
out exception localities subject to earthquake action, distinct shocks
often of very small amount, and not sufficient to do any material
damage, have been recorded as occurring in almost every country
in Europe. There is generally but little connexion to be traced
between those of distant countries.
In Scandinavia, M. Keilhau has recorded several shocks, and there seems no
doubt that, with proper instruments, the number within a given period would be
found much greater than is yet known. On the 31st of August, 1819, one occurred,
having a wide range, and there were several between the 7th of March and 29th of
November, 1827. In January, 1845, an earthquake was felt at Arendal, in Norway
and in April, 1841, slight shocks were noticed in Jutland.
Within the British Islands, but especially in North Britain, a large number of
recent earthquake observations have been made, proving frequent but very small oscilla-
tions in certain districts. Small movements near the coast, producing a slight shake,
were felt in Cornwall, in July, 1843; and on the 22nd of December, in the same year,
considerable shocks occurred in Brittany. Various parts of France and Germany
have been subjected to slight disturbances, which are chiefly felt in the valleys of the
great rivers. North Italy has had many, some being of great magnitude, besides an
infinity of smaller extent. Spain, also, has had several, and with regard to Portugal,
one of the most remarkable earthquakes on record destroyed the city of Lisbon, in
1755, and has long been referred to and described as exhibiting phenomena of the
highest interest and extending over an extent of country so wide that its source must
have been very deeply seated and of corresponding energy (see 203). Both South-
eastern and North-eastern Europe, -as well as Hungary, are frequently subject to slight
disturbances of the surface, no less than 318 having been recorded as occurring
in the valley of the Danube since the commencement of the fourth century, while
Syria and Asia Minor have been long exposed to much more violent shocks. North
Africa partakes of the movements of the northern and eastern shores of the Mediter-
ranean. Russia seems to be the country where there occur the smallest number of
earthquakes, and in the Ural Mountains they are almost unknown.
200. While the whole of Europe and the adjacent countries are
thus manifestly acted on by subterranean forces, which are with few
exceptions sudden and momentary, and very often extremely small
both in local effect and extent, Central, Eastern, and Southern Asia,
and the islands between Eastern Asia and the Australasian Archi-
pelago, are from time to time subjected to more continuous, more
severe, and far more extensive concussions, often shaking and de-
stroying wide tracts. In those countries also, whenever careful
observations are made, the annual number of small shocks is found
to be very considerable.
The whole chain of the Andes, and much adjacent country, but
especially the central Cordilleras and Mexican Andes, are exposed to
104 PHYSICAL GEOGRAPHY.
every kind of subterranean disturbances. The length of the line
along which these phenomena are both common and violent is not
less than 1000 miles, but the lateral extension does not seem very
great, although more considerable on the side of the coast than
towards the interior. North America, especially in the valley of the
Mississippi, is also frequently shaken ; and the islands of the Pacific
are many of them known to undergo a like series of movements.
201. On the whole it appears that the whole or some parts of every
large tract of land, besides numerous islands and portions of the sea
bottom, are exposed to the disturbing forces we are now considering,
for whenever the sea bottom is disturbed, and probably on few other
occasions, waves of translation are generated apart from the ordinary
action of tides and marine currents, and such waves are extremely
frequent on many coasts. It cannot, therefore, be doubted that
there is everywhere beneath the surface some tendency to change,
however slight, and that this tendency is shown by paroxysmal
movements at variable but sometimes considerable depth beneath
the surface, having little relation with each other, though not unfre-
quently repeated in nearly the same direction and over the same
area. Many districts in which the shocks of earthquakes often recur
are unquestionably those in which volcanoes act ; and certain re-
lations have been established between volcanic eruptions and earth-
quake movements, which we shall allude to presently, and which
should on no account be lost sight of. Still there are so many, and
such important exceptions to these apparent relations, and the sub-
ject is still so obscure, that many observations are needed before a
satisfactory conclusion can be arrived at.
202. The actual extent or range of the shock in each particular
case is a matter which we must next consider, and it will be found to
vary almost infinitely, the smaller movements being only just trace-
able, and not affecting at the same time more than a single village
or a few square miles, while the larger shocks range not only over
tracts many hundred miles in length and breadth, but across wide
oceans, and from one continent to another. The latter kind are,
however, comparatively rare ; and in describing one or two a suffi-
cient idea will be obtained of all the more important facts. In most
of the movements of small extent and frequent recurrence little injury
is done, the disturbance not affecting more than a single building or
part of a building. In others, however, the shake and undulation are
sufficient to induce the natives of the countries where they occur to
erect their habitations, and even their public buildings, with a view
to the chance of shocks of moderate extent, although no style of
construction can defend a town against the effects of large and more
serious disturbances.
203. The following account of the great earthquake that destroyed
EARTHQUAKE OF LISBON. 105
Lisbon on the 1st of November, 1755, will be read with interest, and
well describes the chief phenomena. The city had suffered greatly
by an earthquake in 1531, and much damage had then been done by
an accompanying wave, described as a great swell. In that case, no
doubt, as in the other, the disturbance had affected the bed of the
ocean, elevating a portion of the water, and forming a vast wave of
translation, which coming in after the earth-wave, served to complete
the mischief the latter undulation had commenced. We extract the
account from a work published in 1757.
u There was a sensible trembling of the earth in 1750, after which
it was excessively dry for four years together, insomuch that some
springs formerly very plentiful of water, were dried, and totally lost,
at the same time the predominant winds were east and north-east,
accompanied with various, though very small, tremors of the earth.
The year 1755 proved very wet and rainy, the summer cooler than
usual, and for forty days before the great earthquake clear weather,
yet not remarkably so. The 31st of October, the atmosphere and
light of the sun had the appearance of clouds with a notable obfus-
cation. The 1st of November, early in the morning, a thick fog
arose, which was soon dissipated by the heat of the sun, no wind
stirring, the sea calm, and the weather as warm as in England in
June or July. At 35 minutes after 9 o'clock, without the least
warning, except a rumbling noise, not unlike the artificial thunder
at our theatres, immediately preceding, a most dreadful earthquake
shook by short, but quick vibrations, the foundations of all Lisbon,
so that many of the tallest edifices fell that instant. Then, with a
scarcely perceptible pause, the nature of the motion changed, and
every building was tossed like a waggon driven violently over rough
stones, which laid in ruins almost every house, church, convent, and
public building, with an incredible slaughter of the people. It con-
tinued in all about six minutes. At the moment of the beginning
some persons on the river, near a mile from the city, heard their
boat make a noise as if run aground or landing, though then in
deep water, and saw at the same time the houses falling on both
sides the river. Four or five minutes after the boat made the like
noise, which was another shock, which brought down more houses.
The bed of the Tagus was in many places raised to its surface.
Ships were drove from their anchors, and jostled together with great
violence ; nor did the masters know if they were afloat or aground.
The large new quay called Cays Depreda, was overturned, with
many hundreds of people on it, and sunk to an unfathomable depth
in the water, not so much as one body afterwards appearing. The
bar was seen dry from shore to shore ; then suddenly the sea, like a
mountain, came rolling in, and about Belem Castle the water rose
fifty feet almost in an instant ; and had it not been for the great
106 PHYSICAL GEOGRAPHY.
bay opposite to the city, which received and spread the great flux,
the low part of it must have been under water. As it was, it came
up to the houses, and drove the inhabitants to the hills. About
noon there was another shock, when the walls of several houses
which were yet standing, were seen to open from top to bottom more
than a quarter of a yard, but closed again so exactly as to leave
scarce any mark of the injury.
" This earthquake came on three days before the new moon, when
three-quarters of the tide had run up. The direction of its progress
seems to have been from north to south nearly, for the people on the
river, south of the town, observed the remotest buildings to fall
first, and the sweep to be continued down to the water's side. Few
days passed without some shock for the space of an ensuing year.
October 10th, 1756, at 11 o'clock at night, there was one which threw
down the greatest part of an hotel in the parish of St. Andrew ;
and the 1st of November, 1756, being the anniversary of the fatal
tragedy of this unhappy city, another shock gave the inhabitants so
terrible a fresh alarm, that they were preparing for their flight into
the country, but were prevented by several regiments of horse placed
all round by the king's orders."
204. The earthquake of Lisbon was not confined to the spot at which the chief
mischief was effected. At Colares, at a distance of about 20 miles, three distinct
shocks were felt on the 1st of November, accompanied by the emission of a quantity
of smoke, and the fountains were affected. At Coimbra, several buildings were
destroyed ; at Oporto the shocks were felt for six or seven minutes, during which, every-
thing shook and rattled ; the river also being much affected. In Spain, at and near
Cadiz, the destruction was only inferior in importance to that experienced at Lisbon,
the shocks commencing some minutes after 9 A.M., and at 11, a wave coming in
described as 60 feet higher than common. At Gibraltar, a tremulous motion was felt
about ten minutes after ten o'clock, and at Madrid at five minutes before ten o'clock,
the indications in each case very decided, but the result not very destructive. Malaga
felt a violent shock, and at Seville the earthquake damaged the cathedral, and killed
several people. All Spain was more or less affected.
Out of the Peninsula, France was affected in several places on the same day, and
at various parts of the Normandy coast, at about 1 1 o'clock, much disturbance was
observed in the motion of the ocean. Near Angouleme, a subterranean noise was
heard, after which the earth opened and discharged a torrent of water mixed with
red sand. In Italy, earthquakes were felt at Milan, and at Turin, and the waters of
the Mediterranean were greatly disturbed, especially about the island of Corsica, where
there was also a slight shock. In Switzerland, great agitation was noticed, chiefly in
the waters of the Lakes of Geneva, Neufchatel, and Zurich.
While these parts of Europe were disturbed, movements were also felt in Germany,
where the waters of several of the principal rivers were disturbed, and some towns,
as Strasburg and Stutgard, suffered slightly from earthquake shocks. The same took
place in Holland, Norway, and Bohemia, the indications of disturbance being in all
cases chiefly seen in the rivers, and in deep springs of water, which were evidently
shaken, and often rendered muddy. This occurred especially, at Tb'plitz, at Amster-
dam, Haarlem, Leyden, Rotterdam, and the Hague.
The British Islands experienced this shock in various ways, but chiefly also in the
disturbance of rivers, ponds, and springs of water. Shocks, however, were distinctly
felt in the lead mines of the Peak of Derbyshire, and near Reading in Berkshire.
RESULTS OF EARTHQUAKE MOVEMENTS. 107
Various movements of the water were seen along the coast, but most distinctly on
the southern and eastern shores of England, and also in Loch Lomond and Loch Ness,
in Scotland, and in the lakes of Cumberland. On the coast of Ireland the same phe-
nomena were observed, and at Cork there were two shocks of an earthquake. The
amount of rise of the water varied considerably, but seems to have been about equi-
valent to a general upheaval of the bed of the ocean, lake, or stream, to an extent
of from 10 to 30 inches in vertical height. The time of the disturbances in Eng-
land was, in different places, from half-past 9 to 1 1 o'clock, although with some
exceptions.
Besides these places in Europe, many parts of Africa were affected, especially on
the Mediterranean coast, Algiers, Morocco, Tangier, and Tetuan, being all injured by
severe earthquakes. In the Atlantic the Island of Madeira and the Canary Island
suffered ; the water rose in the sea at Antigua and Barbadoes ; and in the open ocean,
several ships were violently agitated by sudden and considerable waves.
It has been observed, that besides a multitude of other places, this great earthquake
was very sensibly felt in Europe, al Fahlun in Sweden ; in Africa at the capital of the
Empire of Morocco ; and in America at the Island of Barbadoes. Between Fahlun
and Barbadoes are 70 of a great circle, nearly ; between Barbadoes and Morocco 49,
and between Morocco and Fahlun, 33 of the like degrees. Now these constitute the
three sides of a spherical triangle, to which, if a well-known theorem be applied, it
will be found, that the effects of the earthquake of the 1 st of November, 1 755, were
distributed over very nearly 4,000,000 of English square miles of the earth's surface ;
a most astonishing space, and greatly surpassing any thing of this kind ever recorded
in history.*
205. The permanent results of earthquake movements, or of the
transmission of a wave through the earth in any district, may be
of two kinds ; either a mere cracking and splitting of certain rocks,
and a consequent removal to a short distance of those which were
in doubtful equilibrium ; or the positive elevation or depression of
an area more or less extensive.
It is chiefly in volcanic districts that the former and least con-
siderable result that of splitting and slightly upheaving or depres-
sing small portions of the surface has been observed, and examples
figured in the annexed diagrams, figs. 23, 24, 25, will enable the
Fig. 25.
Alterations of level produced by Earthquakes.
reader to understand the nature, and something also of the relative
extent of the disturbance. A chasm thus formed in Calabria has
been found to measure as much as a mile in length, 105 feet in
breadth, and 30 feet in depth. Another was three-quarters of a
mile long, 150 feet broad, and above 100 feet dfcep, and a third a
quarter of a mile long, 30 feet broad, and 225 feet deep, t
* " History and Philosophy of Earthquakes," p. 333.
t Lyell's " Principles," ante eit., p. 459-
108 PHYSICAL GEOGRAPHY.
206. " Sir W. Hamilton was shown several deep fissures in the vicinity of Mileto,
which, although not one of them was above a foot in breadth, had opened so wide during
the earthquake as to swallow an ox and nearly one hundred goats. The Academi-
cians also found, on their return through districts which they had passed at the com-
mencement of their tour, that many rents had, in that short interval, gradually closed
in, so that their width had diminished several feet, and the opposite walls had some-
times nearly met. It is natural that this should happen in argillaceous strata ; while
in more solid rocks, we may expect that fissures will remain open for ages. Should
this be ascertained to be a general fact in countries convulsed by earthquakes, it may
afford a satisfactory explanation of a common phenomenon in mineral veins. Such
veins often retain their full size so long as the rocks consist of limestone, granite, or
other indurated materials ; but they contract their dimensions, become mere threads,
or are even entirely cut off, where masses of an argillaceous nature are interposed.
If we suppose the filling-up of fissures with metallic and other ingredients to be a
process requiring ages for its completion, it is obvious that the opposite walls of rents,
where strata consist of yielding materials, must collapse or approach very near to
each other before sufficient time is allowed for the accretion of a large quantity of
veinstone."*
207. " The undulations in earthquakes have been examined with tolerable accuracy,
in respect to their direction and intensity, by means of pendulums and sismometers,
but in their characters of alternation and periodical intumescence, they ha-ve by no
means attracted sufficient attention. In the city of Quito, which is situated at the
foot of a still active volcano the Rucu-Pichincha and at an elevation above the sea
of 9539 feet, and which possesses fine cupolas, high-roofed churches, and massive
houses of several stories in height, I have been often surprised in the night by the
violence of the earthquake-shocks ; but these, though extremely frequent, very rarely
injure the walls, whereas, in the Peruvian plains, even low dwellings built of reeds,
suffer from apparently far slighter oscillations. Natives of those countries, who have
experienced many hundred earthquakes, believe the difference to be less in the greater
or less duration of the shocks, or the slowness or rapidity of the horizontal oscillation,
than in the alternation of motion in opposite directions." t
208. The following is the order of the phenomena of an earthquake occurring at
or near the sea, according to Mr. Mallet, who has lately paid careful attention to the
physical and mathematical problems connected with these disturbances :
" First, we have the earth sound-wave, and the great earth-wave, or shock ; the
sound-wave through the air ; the sea-wave occurring at the time, called the forced
sea-wave ; and the great sea-wave ; all originating at the same moment and pro-
duced by one impulse.
" The sound-wave through the earth, and the great earth-wave or shock, arrive
first, and are heard and felt on land, accompanied, as far as the beach, by the small
sea-wave called the forced sea-wave ; these are almost instantly succeeded by the
sound-wave through the sea ; next arrive the aerial waves of sound, and continue to
be heard for a longer or a shorter time ; and finally, the great sea- wave rolls in upon
the shore.
"The velocity of the land -wave, and that of the accompanying sea- wave being
ascertained, it would seem possible to determine the distance (out of sea) from the
spot affected at which the earthquake originated. But the former will vary with the
nature of the rock through which it is transmitted, for the harder and more elastic
the rock is, the greater will be the velocity of- the earth- wave produced, and vice
v&rsd.
u Now whilst the elasticity of cast-iron is 5'895, thai; of limestone varies from 2'4 to
635 ; slate being 7 '8 ; Portland stone, 1-5 7 ; white marble, 2'15. From these data
we may calculate that the velocity of the wave-transit per second in
* Lyell, ante cit. p. 460. t " Cosmos," ante cit. vol. i. p. 192.
VOLCANOES. 109
Limestone (soft lias) was 3,640 feet or 40 miles per minute.
Sandstone 5,248 57
Portland stone 5,723 62
Marble 6,696 73
Carboniferous limestone . . 7,075 78
Clay slate 12,757 140
"The observed speed of the great Lisbon earthquake, according to Mitchell, was
only 1 750 feet per second, the difference being assignable to breaches of continuity
and other causes of retardation. The sea- wave, on the contrary, had not one- tenth
of that velocity, or did not travel more than 175 feet per second ; so that, if the
interval of time between the two was, as it is reported, half an hour, the focus of the
impelling force would have been about sixty miles distant from the land." *
209. The vorticose movement described as characterising certain
earthquake undulations has been explained by Mr. Mallet in a
manner far more reasonable than had before been done. He con-
siders that the motion is the same kind in every case, but that " the
centre of adherence between the ground and the base of the object
moved is, in^these vorticose movements, neither directly under the
centre of gravity, nor in the plane of motion passing through its
centre of gravity, but in some point of the base outside the line of its
intersection by the plane ; in this case the effects of the rectilinear
motion in the plane of the base will be to twist the body round upon
its bed, or to move it laterally and twist it at the same time, thus
converting the rectilinear into a curvilinear motion in space ; the
relative amount of the two compounded motions being dependent
upon the velocity, and time of movement of the base, and upon the
perpendicular distance measured horizontally at the surface of ad-
herence, between the centre of adherence and the centre of gravity
of the body." t
210. We come next to the subject of volcanoes, which has, indeed,
generally been considered as taking precedence of that of earth-
quakes, but concerning which we shall here say very little, except
as it bears upon the important views of physical geography we have
endeavoured to impress upon the student in the present chapter.
We commence with a description of one of the most striking pheno-
mena on record the first origin of a volcanic district, and the com-
plete history of the whole volcanic process, as it occurred in the
plains of Malpais, in Mexico, about a century ago.
211. The formation of the volcano of Jorullo is, indeed, one of
the most extraordinary physical revolutions recorded in the history
of our planet, for it exhibits an instance of the elevation of a moun-
tain of scoriaB and ashes 1695 feet above the level of the adjoining
plains, in the interior of a continent 106 miles distant from the
coast, and very far from any active volcano. The elevation took
place in the plain of Malpais on the western side of the city of
* Daubeney on Volcanoes, 2nd edition, p. 525.
t Mallet, " Memoirs of the Royal Irish Academy."
110 PHYSICAL GEOGRAPHY.
Mexico, the plain being about 2500 feet above the sea, and bounded
by basaltic mountains.
In the month of June, 1759, a subterranean noise was heard, and
hollow sounds of the most alarming nature were accompanied by
frequent earthquakes, which succeeded each other for from fifty to
sixty days. From the beginning of September, however, everything
seemed to announce the complete re-establishment of tranquillity,
when in the nights of the 28th and 29th the horrible subterraneous
noise re-commenced, and the frightened Indians fled. A tract of
ground from three to four square miles in extent then rose up
in the shape of a bladder, and the bounds of this convulsion are
still distinguishable from the fractured strata ; but so completely is
the bladder shape to be traced, that while near its edges the district
is only 39 feet above the old level of the plain, the convexity in-
creases towards the centre to an elevation of 524 feet. (See fig. 26.)
Those who witnessed this catastrophe from a neighbouring eleva-
tion, assert that flames were seen to issue forth for an extent of more
than half a square league, that fragments of burning rock were
thrown to prodigious heights, and that through a thick cloud of
ashes illumined by volcanic fire, the softened surface of the earth
was seen to swell up like an agitated sea. Two rivers precipitated
themselves into the burning chasms, and the decomposition of the
water doubtless contributed to invigorate the flames, which were
distinguishable at the city of Pascuaro, more than thirty miles dis-
tant, and situated on an extensive table land nearly 5000 feet above
the plains. Eruptions of mud, and especially of strata of clay,
enveloping balls of decomposed basalt in concentric layers, appeared
to indicate that subterranean water had no small share in producing
this extraordinary phenomenon. Thousands of small cones from
6 to 10 feet high, called by the natives ovens (hornitos), issued forth
from the Malpais ; and, although, according to the testimony of the
Indians, the heat of these volcanic ovens had suffered a great dimi-
nution within fifteen years of Humboldt's visit, he states that he
has seen the thermometer rise to 212 Fahr. on being plunged into
fissures which exhale aqueous vapour. Each small cone is a fuma-
role, from which a thick vapour ascends to the height of from 22 to
32 feet, and in many of them a subterranean noise is heard, which
appears to announce the proximity of a fluid in ebullition.
In the midst of the ovens six large masses, elevated from 300 to
1600 feet each above the old level of the plains, sprung up from a
chasm, of which the direction is N.N.E. and S.S.W. The most
elevated of these < enormous masses is the great volcano of Jorullo.
It is continually burning, and has thrown up from its north side an
immense quantity of scorified and basaltic lavas containing frag-
ments of primitive rocks. These great eruptions of the central
VOLCANOES. Ill
volcano continued till the month of February 1760, but in the
following years they became gradually less frequent.
At the time of Humboldt's visit twenty years afterwards, although
the subterraneous fire appeared less violent than at first, and the
Malpais and the great volcano had begun to be covered with vegeta-
tion, they nevertheless found the air heated to such a degree by the
numerous small ovens, that the thermometer at a great distance
above the ground and in the shade rose to 109 Fahr. This fact
proves that there is no exaggeration in the accounts of several
Indians, who affirm that for many years after the first eruption the
plains of Jorullo, even at a great distance from the ground which
had been thrown up, were uninhabitable on account of the excessive
heat which prevailed.
The traveller is still shown two rivers bearing the names of those
whose waters formerly traversed the plain, and which disappeared
on the night of the 29th of September, 1759. At a distance of
6500 feet to the west of the former streams, and in the tract which
was the theatre of the convulsions, two rivers now burst through
the argillaceous vault of the hornitos, making their appearance as
warm springs, and raising the thermometer to 186 Fahr.*
The annexed diagram (fig. 26) will give an idea of the mode in
Fig. 26. '&l
Section across the elevated part of the Plain of Malpais.
which the plain was elevated, and the proportionate elevation of the
principal hills.
212. A volcano generally may be described as a conical hill or
mountain, with a cup-like hollow or crater at the summit, from
which issue occasionally gaseous and acid vapours mingled with
steam ; certain scoriaceous rocks of small specific gravity called vol-
canic ash and pumice, often in the form of fine dust ; and at more
distant intervals several mineral substances in a state of partial or
complete fusion called lava. There can be no doubt whatever that
a very high temperature obtains at small depths beneath the surface
in every active volcanic district ; but there seems no sufficient proof
of this high temperature being the result of communication with
great depths below the surface, or of any volcanic products being
other than surface rocks altered by the admixture of alkaline earths,
which render them readily fusible. It is, however, certain that there
* From Humboldt's "Nouvelle Espagne," as quoted in Daubeney's work on " Active and
Extinct Volcanoes."
112
PHYSICAL GEOGRAPHY.
exists in many cases free communication underground between vol-
canoes at . great distances from each other, and that earthquake
action is checked or prevented in many districts by the occasional
eruptions of ashes and lava that take place at a volcanic vent.
213. Volcanoes are rarely isolated, being on the contrary almost
always collected into groups, some linear, and others apparently in
circular or elliptic areas. (See 226.) They vary indefinitely in
height, some possessing no elevated cone whatever, others being of
moderate elevation, while some rank among the very loftiest of the
mountains of the globe. The proportionate size of the crater and
other details also vary greatly ; some craters, as that of Vesuvius,
seen in the accompanying sketch (fig. 27), being small, but distinct,
and others, as the vast cavity of Kirauea, in the island of Hawaii
Fig. 27.
Crater of Vesuvius in 182Q.
(Owhyhee), of enormous magnitude, measuring 16 miles in circum-
ference and 1200 feet in depth.
214. Humboldt says, " The degree of intensity of the upheaving force is shown
by the height of the volcano, which varies from that of a mere hill to that of a cone
of above 18,000 feet of elevation. It has appeared to me that the height of vol-
canoes exercises a great influence on the frequency of eruptions, which are far more
frequent in the lower than in loftier volcanoes. As instances, I may place in a series
Stromboli, 2,318 feet; Guacamayo, in the province of Quiros (whence detonations
VOLCANIC DISTRICTS.
113
are heard almost daily as far as Chillo, near Quito, a distance of eighty-eight miles) ;
Vesuvius, 3,876 feet ; Etna, 10,870 feet ; the Peak of Teneriffe, 12,175 feet ; and
Cotopaxi, 19,070 feet. If we suppose the seat of action to be at an equal depth
Fig. 28.
Map of the Isle of Palma.
below the general surface of the earth in the case of all these volcanoes, it must require
greater force to raise the molten masses in the case of the higher mountains ; and it
is not surprising that Stromboli, whose elevation is the least considerable, should have
been in a state of constant activity for many centuries, and still serve as a flaming
beacon for the mariners who navigate the Tyrrhenian Sea, whilst the loftier volcanoes
are characterized by longer intervals of repose."*
215. Volcanic districts generally present marked physical fea-
tures, and the characteristic aspect thus assumed will be best under-
* " Cosmos," vol. i. p. 21".
114
PHYSICAL GEOGRAPHY.
Section across a Crater of Elevation.
Fig. 30.
stood by referring to the annexed physical map of the Isle of Palma
(one of the Canary islands), which is reduced from an admir-
able map prepared by M. Von Buch, and exhibits the central ele-
vated crater and deep furrows or gorges (locally called barancos),
not infrequent in the sides of recently elevated craters. -It is
evident by the natural sections afforded in the ravines that the
whole island is one of those phenomena described by Von Buch as
craters of elevation, the beds all rising towards a central and lofty
ridge, as shown in the diagram fig. 29.
216. The true structure of
such volcanoes and volcanic
groups is further illustrated in
a group of islands in the Greek
Archipelago, of which Santorin
is the principal. A chart of
these islands is given in fig. 30, and a sectional view across them in
fig. 31. The large crescent-shaped island of Santorin, and the islands
Therasia and Aspro-
nisi, here form the
ridge of the half-ele-
vated crater, while
the central islands
Hiera Nea, Micra
Kameni and Phera,
are portions of small
cones rising above
the waves. Of these
Hiera was first ele-
vated 186 years be-
fore the Christian
era, and other small
islets in the years
19, 726 and 1427.
In 1573 was formed
Micra Kameni, and
in 1707 Nea Kame-
ni, which was further
elevated in 1709,
1711, 1712, &c.
Other islands of the
Greek Archipela-
go are formed
in the same ^-^>?
manner. Map an d Section of Santoriu and the adjacent Islands.
VOLCANIC PRODUCTS.
115
217. As a still further illustration of the structure of volcanoes,
and in the case of one of very large dimensions, we may next refer
to the subjoined view and profile of Etna and the adjoining district,
figs. 32, 33. This view will serve to correct the idea that mighc
Lava of 1832
Terminal cone[
SOUTH.
Val del 13ov<
Lava of l66c
Catania
Cyclopean Isles
Fig. 32.
nag*
NORTH.
; Taormina.
Fig. 33.
View and Profile of Mount Etna and the surrounding Country.
arise on the first consideration of volcanic phenomena, and enable
the student to see the small space which the crater and lava currents
occupy in proportion to the mass of a large volcanic mountain.
218. It is no part of our plan to dwell at any length on the sub-
ject of volcanic products. They include, as has been already said,
gases, vapours, ashes and lava ; and after a brief account of remark-
able eruptions of the two latter, we shall pass on to another part of
the subject. Little doubt can be entertained that these are derived
from near the surface, especially since it has been discovered by
Ehrenberg that even where no fresh-water exists and no trees grow,
the ashes erupted from volcanoes in small islands in the open ocean
abound with the remains of fresh-water and terrestrial infusorial
animals and plants. In Mexico, Peru, the Isle of France, and many
other volcanic regions, the fine volcanic dust has yielded these re-
mains ; and it is only in one place (in Patagonia), that the specimens
of tuff and ash examined by M. Ehrenberg have yielded marine
infusorial forms. It is generally the siliceous fragments that have
been preserved, and these are often half obliterated.
219. As an instance of a volcanic eruption extremely remarkable
for the extent of its influence, we may here give, in a few words, an
account of what took place in the Island of Sumbawa (one of the
116 PHYSICAL GEOGRAPHY.
Sunda Islands, lying to the east of Java), in the year 1815. The
noise of the explosions accompanying this eruption was heard at
the distance of 970 miles to the west, and 720 miles to the east of
the island. The ashes were carried 300 miles in the direction of
Java, and more than 200 miles northwards towards the Celebes, in
sufficient quantity to darken the air ; and they were found floating
in the ocean to the west of Sumatra, a distance of more than 1000
miles, forming a mass two feet thick, through which vessels with
difficulty forced their way.
220. Perhaps the most remarkable eruption on record, in respect
of the quantity of lava ejected, was that of one of the Icelandic
volcanoes, the Skaptaa Jokul, in the year 1783. On the 8th of
June in that year, the unfortunate inhabitants of the south coast
of Iceland observed numerous pillars of smoke rising in the hill
country towards the north, which gradually collected into a dark
band, obscuring the light of day, and advancing in a southerly
direction against the wind, showering down vast quantities of sand
and ashes. The cloud continued to increase until the 10th, when
fire-spouts were seen in the distance, and there were slight shocks of
an earthquake. On the llth the large river Skaptaa, which had
lately been much swollen, entirely disappeared ; and this accident
was fully accounted for on the ensuing day, when a current of lava
burst from one side of the volcano, and rushed with a loud crashing
noise down the channel of the river, which it not only filled, but
overflowed, although in many places the channel was from 400 to
600 feet deep, and 200 feet broad.
The fiery stream, leaving the hills, had its course checked for
several days by a lake in the low country ; but this also was at
length filled up, and the torrent proceeded in two streams, one
taking an easterly and the other a southerly direction. The lava
continued to flow till the 20th of July, and, following chiefly the
course of the Skaptaa, it poured over a lofty cataract, filling up in
a few days an enormous cavity, which the waters had been hollowing
out for ages.
Up to this time the eastern part of the island had escaped any
more serious injury than the showers of ashes, which fell every-
where j but on the 28th of July a further eruption was threatened ;
and, on the 3rd of August, a thick vapour arising, and the waters
disappearing from the bed of another river, the Hverfisfliot, prepared
the inhabitants to expect a fiery torrent ; which, accordingly, on
the 9th, rushed on with indescribable fury, overflowing the country
in one night to the extent of more than four miles, and converting
their fearful anticipations into still more dreadful realities. The
eruptions continued at intervals till the end of August, and closed
with an earthquake of extreme violence.
ERUPTION OF THE SKAPTAA JOKUL. 117
The immediate source, and the actual extent, of these torrents of
melted rock have never been accurately determined ; but the stream
that flowed down the channel of the Skaptaa was about 50 miles in
length, bj 12 or 15 miles in its greatest breadth, and that in the
other river-course, about 40 miles in length, by 7 miles in breadth.
In thickness it was very variable ; being as much as 500 or 600
feet in the narrow channels, but in the plains rarely more than 100
feet, and often not exceeding 10 feet. Taking the lowest average,
and calculating the whole mass, it does not appear that there can
have been less than twenty thousand millions of cubic yards, or
forty thousand millions of tons of matter, poured out of the bowels
of the earth, in a melted state, in the short space of ten weeks,
during which the eruption lasted.
It would not give a just idea of the result of this fearful event did
we not add, that, at the most moderate calculation, 1300 human
beings lost their lives during, or in consequence of the eruption ; and
that it also involved the destruction of 20,000 horses, 7000 horned
cattle, and 130,000 sheep. The fisheries on the southern coast of
the island were destroyed \ and Iceland has not to this day recovered
from the disastrous events of the year of the eruption of the Skaptaa
Jokul.
These accounts of a few of the more striking phenomena of recent
volcanic action will give some notion of the magnitude and extent
of the deep-seated disturbing forces incessantly at work, tending to
reproduce those irregularities of surface which are destroyed and
levelled by the antagonist force of running water.
221. We pass on now to a very important part of the subject
namely, the actual number and distribution of volcanoes on the
earth's surface, for these phenomena are not seen everywhere, nor do
they occur like earthquakes without leaving visible traces. There
are two kinds, or rather conditions of appearance to be observed and
sought for, volcanoes exhibiting indications of either present or past
activity. Sometimes the extinction of volcanic influence in a dis-
trict once manifestly subject to it, is sufficiently marked to leave
no question as to the matter, but it is not always so j and many
instances are known of volcanoes which have offered no instance of
activity within the memory of man, or even the historic period, but
which yet cannot be said to be extinct, but are rather dormant.
Still there are in Europe many well marked cases of extinct volcanoes,
but elsewhere it will be convenient to group together, in explaining
their geographical distribution, all the volcanic cones, heaps of ashes,
currents of lava, and other volcanic products, regarding them all as
indications of recent volcanic activity.
222. In Europe and its dependencies there are active volcanoes
only in South Italy, in Sicily and the adjacent islands, in the Grecian
118 PHYSICAL GEOGRAPHY.
Archipelago, and in the island of Iceland. Extinct volcanoes are
found in Auvergne (Central France), in the Eif'el, on the Rhine near
Bonn (the Siebengebirye), in the Black Forest near Switzerland, and
in many places in Western Germany between the two last named
districts. Other indications appear in Northern Bohemia and North-
eastern Bavaria, in Silesia, Moravia, Hungary, Transylvania, Styria,
North Italy, Central Italy, Spain and Portugal.
223. In Asia marked volcanic phenomena have been described in
most parts of Asia Minor and Palestine in Arabia, Persia, and the
adjoining countries, in Central and Eastern Asia, throughout the
Indian Archipelago, in the Japanese and other islands parallel to the
east coast, and in Kamtchatka. Many of the most frequent and
magnificent exhibitions of volcanic force have occurred in the chain
of the Sunda Islands, running along from the Malayan peninsula
towards Australia, and thence to New Zealand. Other volcanic dis-
tricts occur in the Pacific between this archipelago and the coast of
America. Africa exhibits numerous volcanic appearances on its
northern, and also on its western coast ; and most of the islands in
the Atlantic, lying near this continent, are volcanic, as well as some
of those in the Indian Ocean.
"The great distance from the sea of the volcanoes of the interior of Asia is a re-
markable and solitary phenomenon. Abel Remusat, in a letter to Cordier, first directed
the attention of geologists to this fact. The distance in the case of the volcano of
Pe-schan to the north, or to the Icy. Sea at the mouth of the Obi, is 1780 miles; to the
south, or to the mouths of the Indus and the Ganges, 1760 miles ; to the west, 1590
miles to the Caspian in the Gulf of Karaboghaz; and to the east, 1180 miles. The
active volcanoes of the New World were previously supposed to offer the most remarkable
instances of such phenomena at a great distance from the sea; their distance, however,
is only 150 miles in the case of the volcano of Popocatepetl in Mexico, and only 107,
120, and 182 miles in those of the South American volcanoes Sangai, Tolima, and de la
Fragua respectively. I exclude from these statements all extinct volcanoes and all tra-
chytic mountains which have no permanent connection with the interior of the earth."*
224. North America presents a broken, but evident chain of vol-
canoes along its western coast, parallel to and near the Pacific shore.
Central America abounds with volcanoes, and the Antilles among
the West Indian Islands present everywhere either active or extinct
volcanic phenomena. In South America the whole of the Cordil-
lera of the Andes from Mexico to Patagonia, and beyond Tierra del
Fuego to the South Shetland Islands, must be regarded as one great
volcanic system, the distinct indications of volcanic force being rarely
at sufficient distance to allow of doubt as to the existence of a true
subterranean communication.
225. The subjoined table will give a general idea of the distribu-
tion of volcanoes over the world, and the comparative number of
distinct volcanic vents in the different regions. It includes about
400 described examples of active volcanoes, being those of which
* " Aspects of Nature," (English edition) vol. i. p. 88.
CHIEF VOLCANIC GROUPS.
119
there is some evidence of activity within the historic period. Many
of them, indeed, have not been known as distinct points of eruption
for many centuries ; but this does not remove them from the list, as
it is very possible for the internal fire to slumber for a much longer
period between two epochs of outburst. By giving an idea of the
actual distances within which the principal groups are placed, as
well as the number in each case, perhaps this table will be found to
communicate a tolerably distinct idea of the importance of each group.
In many cases, however, the volcanoes are very closely congregated
in knots about the centre of the district, while towards its outskirts
are only a few cones and craters.
226. List of the Principal Volcanic Groups with the linear
extension of each group.
Number
of
Volcanoes.
Linear
extension in
Brit. sta.
miles.
Atlantic Ocean.
Jan Meyen Island (Greenland) . . 2 p
Iceland 8 J
Azores 2 )
Canary Islands 7J- ?
Cape Verde Islands 1 j
Ascension Island I
Trinidad Island 1
Tristan da Cunha Island 1
West India Islands 10 450
Mediterranean group
Lower Italy 2 ^ p
Lipari Islands 2 *
Greek Islands 1
Red Sea 2
Indian Ocean (west side)
Bourbon Island lj
Mauritius Island If- ?
Rodriguez Island 1 J
Asiatic Continent
Western Asia 3
Central Asia 2
Eastern Asia ?
Asiatic Coast
Kamtchatka group 21 900
Kurile Islands group 18 800
Japan Islands group 23 1 700
Bonin and Mariana Islands .... 9 1000
Formosa 3 280
Luzon and the Philippine Islands 21 1000
Molucca Islands .....* 12 700
North-west coast of New Guinea 4
Sunda Islands group
Floris and adjacent Islands to \ ,
the west as far as Serva ....J J
Sumbawa and others 9 350
120 PHYSICAL GEOGRAPHY.
Java ........................ 43 ...... 650
Sumatra .................... 7 ...... 900
Andaman Islands ............ 5 ...... 600
Eastern Archipelago
Groups of Islands between New \ .
Guinea and New Zealand . . *
New Zealand ................ 2
Friendly Islands .............. 2
Pacific Ocean
Hawaii (Owhyhee) group ...... 4
Society Islands, .............. 1 )
Marquesas Islands ............ 1 /
Easter Islands ................ 1
Galapagos Islands ........ , . . . 1
America
Aleutian Islands .............. 35 ...... 1200
North American Series ........ 10 ...... 2000
Mexico ...................... 7 ...... 700
Guatemala .................. 38 ...... 850
Quito ...................... 17 ...... 450
Peru and Bolivia .............. 12 ...... 600
Chile ...................... 22 ...... 1200
Tierra del Fuego .............. 3 ...... 400
Antartic Land ........................ 3
Those groups to which no linear extension is marked are for the most part detached,
and exhibit only imperfect communication with any other district. The groups con-
nected by brackets are probably related, but too imperfectly to justify any statement
as to their linear extension.
227. One more matter remains for consideration before we quit
the subject of volcanoes. It is the nature of the subterranean com-
munication that exists between those of the same or different groups.
On this point, as on so many others, we may quote, as of the highest
authority, the language of Humboldt, when speaking of the plateau
of Quito, where occur the lofty volcanoes of Pichincha, Cotopaxi,
and Tunguragua. This, he says, is to be viewed asli syjgle volcanic
furnace? " The subterranean fire breaks forth sometimes through
one and sometimes through another of these openings, which it has
been customary to regard as separate and distinct volcanoes. The
progressive iriarch of the subterranean fire has been here directed for
three centuries from north to south." He also states, " that in 1797
the volcano_ of Pasto, east of the Guaytara river, emitted uninter-
ruptedly for three months a lofty column of smoke, which column
disappeared at the instant when, at a distance of 280 miles, the great
earthquake of Riobamba, and an immense eruption of mud, took
place, causing the death of between 30,000 and 40,000 persons." *
228. Facts of similar kind are not wanting in South Italy, tending to prove an
open subterranean communication between Etna and Vesuvius and the adjacent vol-
* "Aspects of Nature," ante cit. vol. ii. p. 222.
ALTERATION OF LEVEL. 121
canic vents, since, in nearly 130 recorded disturbances within the last eight centuries,
there have occurred few instances of activity from more than one crater at the same
time, and not one of any important eruption from the two principal mountains or from
any of the smaller cones within a considerable interval. In this way it seems
clear that however distinct the volcanoes of the same system may be at the surface,
they are in each case parts of one general effect, produced by some deep-seated sub-
terranean cause.
229. Volcanoes have been arranged into two classes, "central
volcanoes " and " volcanic chains " but whether such distinction
really exists in nature, we may be allowed to doubt. The former
term has been applied to those districts in which a region of volcanic
disturbance appears to extend to pretty nearly the same distance in
every direction from one central point, while the latter includes
instances, of which many are given in the annexed table, where the
chain is much further continued in one direction than any other.
The volcanoes in the latter case have been compared by Humboldt
to a number of vents, either in one line or in parallel lines, connected
with some far-extended subterranean fissure, such as we may imagine
to have reference to the elevation of a mountain chain. The Peak
of Teneriffe is a well-marked example of a central volcano, and so also
is the Isle of Palma ;* which well illustrates the peculiar appearance
presented in such cases. A theory of the formation of volcanoes by
elevation at a central point has been based upon this latter view, and
explains many of the appearances presented in the Canary Islands
and Azores. It does not, however, apply universally, as the volcanic
cone is often entirely subordinate to the mountain elevation, and has
been established long after the main direction has been given to great
and important lines of elevation. It may, indeed, be stated generally,
that all the principal volcanic systems are dependent on main lines
of direction, or axes of mountain chains, this being the case even for
the continental land of the Old World, although so few volcanoes exist
there that it is not easy to connect them into one general group. In
the New World, the fact is too manifest to require further notice than
a reference to the map.
230. The permanent alteration of level of large tracts of land in
consequence of earthquake and volcanic action, is a subject which has
not yet received full illustration, but that numerous and important
temporary changes of level have accompanied or followed the mo-
mentary undulations in disturbed districts is beyond question. One
of the standard examples of this, referred to by almost every recent
writer on geology, is that of the Temple of Jupiter Serapis near
Naples, where the temple appears to have been originally built very
near the level of the Mediterranean, after which the ground with the
temple gradually sank down ; thermal waters also issuing in the vici-
nity, and forming a brackish lake, which left a black incrustation on
* See fig. 28, 215.
122
PHYSICAL GEOGRAPHY.
the stone walls as far as the water reached. The lower part of the
columns and the floor of the temple seem then to have become covered
Fig. 34.
Temple of Jupiter Serapis.
with a quantity of ashes and tufa,
to a thickness of about eight feet,
and the depression of the surround-
ing soil being continued, the incrus-
tation increased, at first irregularly,
and perhaps slowly, till at length
the sinking was so considerable that
the greater part of the columns be-
came submerged, the upper and un-
covered portions being exposed to,
the action of the air, and the part
in the sea being eaten into by vari-
ous marine animals, as far down as
there was no covering of ashes and
tufa. At length the ground was
elevated, and, at the present day,
the whole is above the level of the
adjacent sea. The movements are
still going on, and a change of
position has been recognised within
the last few years.
The following are the oscillations as stated by Lyell (" Principles," p. 494). First,
About eighty years before the Christian era, when the ancient mosaic pavement
was constructed, it was about twelve feet above its actual level, or that at which it
stood in 1838 ; secondly, towards the close of the first century after Christ it was
only six feet above its actual level ; thirdly, by the end of the fourth century it had
nearly subsided to its present level ; fourthly, in the middle ages, and before the
eruption of Monte Nuovo, it was about nineteen feet below its present level ; lastly,
at the beginning of the present century, it was about two feet two inches above the level
at which it now stands in 1838.
231. Subsidence has also been noticed in the low ground subject
to earthquakes at the mouth of the Indus, where the same earthquake,
during which a large tract was depressed, exhibited also the elevation
of a long mound, measuring as much as fifty miles in one direction,
and in some places sixteen miles broad.
The valley of the Mississippi has lately undergone some change
during long-continued earthquake undulations in 1812. These
changes are described by Sir C. Lyell,* and appear to afford a good
illustration of the nature of depression. Many districts in South
America have been known to present indications of very recent change
of level, altering the beds of rivers, and sometimes, by the elevation
of a coast line, destroying large numbers of marine animals. The
harbour of Port Royal in Jamaica on one occasion sank down nearly
* Lyell's " Principles," ante cit. p. 444.
EXTINCT VOLCANOES. 123
50 feet, and the number of similar examples of alteration of level,
immediately resulting from earthquake disturbance, is quite sufficient
to prove a connection between the two sets of phenomena.
232. We have already, in a former paragraph ( 222), in speaking
of the volcanoes of Europe, had occasion to notice several which are
now in a state of inactivity, and concerning which there is reason to
suppose they are really extinct. When, as in the cases there men-
tioned, the actual condition of the mineral products is such as to
indicate considerable antiquity, or when the destruction of form of
the ancient volcano has been at all complete, there is, perhaps, little
difficulty in determining to which class it should be referred; but in
other cases there is often great want of satisfactory evidence. The
appearances presented in some well-known instances leave no doubt
as to their identity with recognised volcanic results, and it will be
desirable to describe some of these. All of them have been perfectly
quiet, and free from the disturbances of volcanic action, during, and
probably long before, the existence of man upon the earth, but all of
them exhibit, with the utmost distinctness, series of volcanic pheno-
mena exactly resembling those which are described as characterising
Etna and Vesuvius in modern times.
233. The volcanic district of the Rhine extends for about twenty-four
miles from east to west, and from six to ten miles from north to south.
The volcanic cones have been forced up through beds of ancient date,
and the lava has been poured out around the base of the hills, often
extending to considerable distances without much reference to the pre-
sent configuration of the country. A number of ancient craters, some
of which are now lakes, may be observed at different points on each
bank of the Rhine, but the walls of these craters are usually made up
of cinders and scoriae, and the deep indentations and fractures of the
walls often show the points whence a lava current must once have
issued. On the whole, however, the lava seems to have been chiefly
erupted through cracks and fissures in the subjacent rocks, and to
have been spread evenly over the surface, often in very thin bands.
By far the most important feature of the volcanic district of the
Rhine is the great basaltic * platform, partly in the Duchy of Nassau
and extending on the right bank of the Rhine, but reaching still
further to the east, and forming the hills called the Vogels Gebirge.
In the former district the lava beds are covered up in many places
by a remarkable bed of lignite, or brown coal, but an area of not less
than 1000 square miles of country in the neighbourhood of the Rhine
seems to have been in former ages overwhelmed by a flood of lava,
probably spread out beneath the waters of an inland lake long since
dried up. The thickness of the bed is not very considerable.
* Basalt is the name given to rocks supposed to be ancient lava currents, but now present in
places where no volcanic activity is discoverable. The term is further explained in 236.
124 PHYSICAL GEOGRAPHY.
234. The district of Central France which in former times was' the
seat of subterraneous disturbance, reposes on, or rather rises out of, a
granite platform ; the Mont D'Or, the most conspicuous of the volca-
nic cones, rising suddenly to the height of several thousand feet, and
being composed of layers of scorise, pumice stones, and fine detritus,
with interposed beds of basalt. A considerable number of minor
volcanoes form an irregular ridge on the platform, and extend for
about eighteen miles in length and two in breadth. They are usually
truncated at the summit, where the crater is often preserved entire,
the lava having issued from the base of the hill ; and the lavas may
be traced from the crater to the nearest valley, usurping the channel
of the river, which in some cases has since been re-excavated.
235. In Catalonia the eruptions have burst entirely through
Secondary rocks, and the distinct cones and craters are about fourteen
in number, but there are besides several points whence lava may have
issued. The volcanoes are most of them very entire, and the largest
has a crater 455 feet deep, and about a mile in circumference. The
currents of lava are, as usual, of considerable depth in the narrow
denies, but spread out into thin sheets over the plains ; the upper
part is scoriaceous, further down it is less porous, and at the bottom
it becomes prismatic basalt, about five feet thick, resting on the sub-
jacent Secondary rocks.
It is probable that the western part of Asia and the Peninsula of
India exhibit the phenomena of recently extinct volcanic action on
a scale far grander than is known in Europe, for in these countries
the lava has been poured out over an area of many thousand square
niiles, and rests in flat tabular masses upon the country.
Volcanic rocks, like thoseof the Westerwald andVogelsgebirge may be traced at inter-
vals, both southward towards Switzerland, and eastward across the north of Bavaria
into the north of Bohemia. They accompany the porphyries of the Odenwald, near
Heidelberg, and the granite of the Fichtelgebirge ; in some cases presenting volcanic
cones, and in others only trachytic rocks. The hot springs of Carlsbad and Toplitz and
the vicinity of these spots, marks the continuance of the district towards Silesia, and ba-
saltic cones occur on the south flanks of the Erzgebirge, in Saxony, and in several places
between Dresden and Freyburg. Various places in Upper Silesia, and others on the
western border of Moravia, near Hungary, present rocks which can only be referred to
causes resembling those now in action in volcanic districts, while in Hungary itself, on
the southern flanks of the mountain chain which separates that country from Gallicia,
even more striking and distinct remains are presented of ancient volcanic fire. These
are chiefly of the rock called trachyte, which is one of the compounds formed by the
association together of various silicates at a high temperature. Transylvania presents
several instances of old craters and half-extinct solfataras, while Styria, North Italy,
Central Italy, European Turkey, and other adjacent countries towards Asia Minor,
afford connecting links with the present sources of active volcanic disturbance in
South Italy and the Greek Archipelago. Several places in Asia Minor near Smyrna,
and thence to the valley of the Jordan, and wide tracts in Persia, carry the evi-
dences of volcanic agency far into Asia, while the shores of the Red Sea, and the
extremity of Arabia are proofs of a similar kind in connection with the volcanic
islands of the Indian Ocean.
PERMANENT ELEVATION OF LAND.
125
236. In many parts of our own country and elsewhere, but espe-
cially in the Isle of Staffa and the opposite coasts of Antrim in
Ireland, indications are afforded of the presence of melted rock,
identical in composition with lava, and yet unconnected with any
obvious volcanic appearances. Such indications have generally
been referred to submarine eruptions, but as they can hardly be
View of Fingal's Cave, Isle of Staffa.
described without some account of the beds and other rocks with
which they are associated, any details must be postponed to a future
chapter. Beds of lava thus dissociated from true volcanoes are
usually called basalt, but they differ much in appearance, texture,
and even composition. With them, and sometimes without any
other evidence to connect them with igneous agency, we not unfre-
quently find minerals and rocks referred to as tuff or volcanic ash, but
such evidence is imperfect, and in many respects unsatisfactory.
237. We have seen that in the neighbourhood of volcanoes and
in extensive districts subject to earthquake action, there are often
local and temporary changes of level, consisting frequently of oscil-
lations, and limited to small areas. Besides this, however, elevation
and depression of a different and more extensive kind has been
observed in many parts of the world where no vicinity of volcanoes
and no distinct subterranean action can be traced, to account for
such change. The coasts of the Baltic Sea and Northern Ocean, the
coast line of Britain, and the shores of Greenland, have been chiefly
referred to in evidence of elevation of this kind, but it will be clear,
on a moment's consideration, that some peculiarly favourable circum-
126 PHYSICAL GEOGRAPHY.
stances are required that we may obtain the required proof of the fact
in question. The amount of supposed change is indeed rarely more
than a few feet in a century, and no measurements of the elevation of
land above the sea-level so accurate as this have been made till within
a very few years, owing partly to the real difficulties of measurement,
and the liability to error from the imperfection of instruments, and
partly to the absence of any admitted and recoverable base line. On
the shores of the Baltic, however, where there are hardly any tides,
where the inner line of coast is defended by a fringe of islands, and
where the rocks are hard and often very near the surface, the means
are presented by nature, and they have not failed to attract notice.
The result is, that there appears to have been a gradual but slow up-
heaval, very different in different places, but sufficient, in the course
of the last two or three centuries, to lay bare many rocks before sunk,
to expose the foundations of buildings built on the shores at the water
line, to choke up and render useless old channels between rocks, and
even to lay bare some beds of marine shells. The so-called raised
beaches, found in various parts of England at a height of from 20 to
200 feet above the present coast line, often exhibit gravel and sand
with marine shells having all the peculiar features of the existing sea
beach ; and similar terraces, more or less distinctly marked in various
places along the whole European coast line of the Atlantic, afford
ample proofs that this change of level and gradual uplifting of the
land has gone on for a long while. Some remarkable ledges, eaten
out, as it were, from the hard and steep rocks, at certain heights on
the bold cliffs of Finmark near the North Cape, seem to prove that
there must have been long alternations of elevation and repose ; and
also that the elevations have been by no means uniform over the
whole area lifted, but much more in one direction than any other,
and gradually less in amount in a direction at right angles to this.*
238. South America, also, as it presents the most magnificent
chain of continuous mountain ridges and the largest river systems
in the world, seems to afford the most distinct and best instances of
slow elevation, and the upheaval of an ocean floor into the main
land of a vast continent. Mr. Darwin has shown that for a distance
of at least 1200 miles from the Rio de la Plata to the Straits of
Magellan on the eastern side, and for a still longer distance on the
west, the coast line and the interior have been raised to a height of
not less than 100 feet in the northern part, but as much as 400 feet
in Patagonia. All this change has taken place within a compara-
tively short period, for in Valparaiso, where the effect is most con-
siderable, modern marine deposits with human remains are seen at
the height of 1300 feet above the sea.
* See the evidence on this subject collected by M. Bravais, and translated in the " Quarterly
Geological Journal," vol. i. p. 534.
PERMANENT DEPRESSION OF LAND. 127
239. The vast tracts described in the last chapter* and presenting
the work of the coral animal as an effectual barrier against the waves
of the Pacific, seem to mark areas of subsidence not less extensive
than those of the main land of South America exhibit elevation. The
only reasonable explanation of the existence of banks of dead coral
many hundred feet deeper than the extreme limit at which the coral
animal which built them could have lived, is in the assumption that
a gradual depression took place of the land on which they were ori-
ginally based, and this also involves the former existence of a large
tract of land near the Equator to the east of, and partly including the
Indian Archipelago. That such depression of a large area is in other
respects probable, appears from the form and distribution of the land
in that part of the world, and from the fact of the elevation of large
areas elsewhere.t
" That the bed of the Pacific and Indian Oceans, Avhere atolls are frequent, must
have been sinking for ages, might be inferred, says Mr. Darwin, from simply re-
flecting on two facts ; first, that the efficient coral-building zoophytes do not flourish
in the ocean at a greater depth than 120 feet ; and secondly, that there are spaces
occupying areas of many hundred thousand square miles, where all the islands con-
sist of coral, and yet none of which rise to a greater height than may be accounted
for by the action of the winds and waves on broken and triturated coral. Were we
to take for granted that the floor of the ocean had remained stationary from the time
when the coral began to grow, we should be compelled to assume that an incredible
number of sub-marine mountains of vast height (for the ocean is always deep, and
? often unfathomable, between the different jjjfllls) had all come to within 120 feet of
the surface, and yet no one mountain had risen above water. But no sooner do we
admit the theory of subsidence, than this great difficulty vanishes. However varied
may have been the altitude of different islands, or the separate peaks of particular
mountain chains, all may have been reduced to one uniform level by the gradual sub-
mergence of the loftiest points, and the additions made to the calcareous cappings of
* the less elevated summits as they subsided to great depths. "J
L 240. Such, then, is the evidence on which we assume that there
are districts of the earth now undergoing depression on a scale not
dissimilar to, nor, indeed, unconnected with that on which we recog-
nise elevation. By observations of this kind on low islets which only
retain their existence because they have been found convenient for
the habitation and structures of the coral animal, we are enabled to re-
cognise the last vestiges of lofty peaks, which once, perhaps, existed as
mountain tops penetrating the region of the clouds. We thus recon-
struct in imagination the land which has been submerged, and may
even be induced to speculate concerning the date of the submergence,
j and the plants and animals that clothed the ancient continent.
L Considered, however, in their extent, and in their bearing on the
general argument, these various facts and probabilities with respect
to disturbance of the earth's crust suggest conclusions in the highest
degree important and interesting.
* See 178. t See a Memoir on this subject by Mr. Dana, " Silliman's Journal,"
t Lych's " Principles," ante cit. p. 760. vol. xlv. p. 131.
128 PHYSICAL GEOGRAPHY.
We have seen, for instance, that the solid framework of our globe
is frequently exposed to subterranean action, obtaining relief from
time to time by volcanic outbursts of melted rock and ashes thrust
forth from beneath with almost inconceivable force and velocity ;
at other times tearing asunder the thin .crust that has cooled over
the boiling and restless mass beneath, producing undulations and
' earth-waves which embrace in their vibrations a large proportion of
the surface, which carry terror with them and leave destruction
behind them. We have seen, also, that besides movements of this
kind, readily and immediately perceived, there are others, affecting
areas no less extensive, and in a still greater and more permanent
manner ; modifying the form of land, producing or destroying con-
tinents and islands, and effecting changes which in their turn influence
the conditions of life upon the earth.
Changes of this kind, so considerable that it is difficult fully to
i realise their amount, so majestic in their progress that the age of
man is hardly an appreciable instant in reference to the time they
occupy, so directly influencing the great physical features of the
earth, that our speculations with regard to them carry us back to an
early period of its existence, will at once be recognised as of the
most vital importance in reference to the continuous and ancient
history of our globe.
And the facts thus learnt harmonise perfectly with other pheno-
mena of nature, for they speak of the existing condition of things
as incidental and not permanent : as a part, and a very small part,
of a mighty and continuous whole.
They remind us, also, that if we study nature we must everywhere,
and at all times, expect modification and change. The ide
matter and motion are thus seen to be inseparable, and no ratipnal
conclusions can be arrived at without bearing this truth constantly
in mind.
And, lastly, we learn that although there is nothing permanent in
the forms which matter may assume, there is still order and unity,
and the most enduring permanence in the laws which govern and
produce them. This is beyond doubt a conclusion of infinite value,
for it connects together into one system facts and groups of facts
which would otherwise be discordant, and it affords the key for the
solution of innumerable difficulties and apparent discrepancies ob-
served when we endeavour to trace out the great plan of nature.
PART II.
MINERALOGY,
CHAPTER VII.
CRYSTALLOGRAPHY, OR MINERAL SUBSTANCES AS DETERMINED
BY FORM AND STRUCTURE.
241. IT is the object of Mineralogy to describe the form, the
internal structure, the chemical composition, the physical properties,
and the uses to man of all those natural material productions which
are not organic, or in other words, of those not capable of repro-
ducing their like by any mutual action, and not modified by the
influence of life. The combinations of which it treats are thus
always identical under similar circumstances, and far from any modi-
fication being induced in the results in different countries, or at
different times, as is the case with animals and vegetables, there can
be no reason to doubt that during all time for so long, at least, as
the same laws have been in existence similar minerals and rocks
may have been repeated without variety. In all simple minerals,
therefore, of which the particles have once obtained a condition of
mechanical and chemical equilibrium, there seems to be no tendency
to change or undergo decomposition were it not that chemical forces
are constantly at work, tending to decompose and rearrange all ex-
isting combinations of matter.
242. Like all Natural History sciences in which numerous indivi-
duals have to be described in their mutual relations to one another,
the classification of these, or the arrangement of like individuals in
certain groups, is a most important preliminary study, since it is only
by the aid of arrangement that we are enabled to remember, com-
municate, and apply our knowledge. In a good systematic nomen-
clature ideas are suggested by mere position in the system, and a
knowledge of this position becomes a representative of the natural
substance itself. Without such a basis, indeed, there is little
K
130 MINERALOGY.
advance to be made ; and thus it is requisite that certain properties
should be admitted and recognised by which the different groups are
naturally and readily distinguished, and these may be called the
characteristics of the individual.
- 243. The characteristics of minerals, or the Natural History pro-
perties by which we distinguish one from another, are of very dif-
ferent kinds. They include colour, external form, hardness, weight,
and internal structure, as the most important visible characters, while
actual chemical composition affords the most valuable information
when minute comparison and further investigation are needed. Be-
sides these there are certain optical and electrical properties, and some
other physical ones which are also well worthy of careful attention ;
and, lastly, there exist very well marked and curious relations of
form, the result, probably, of chemical action, which it is necessary to
consider minutely in determining the true nature of simple minerals.
~- 244. It may seem, perhaps, that mere form is not likely to be so
important a character in the determination of minerals as many
others, for we are in the habit of regarding stones and minerals as
almost without definite shape. In reality, however, few things in
nature are so truly and neatly defined as simple minerals ; and on
looking a little more closely we shall find that this is the case not
only externally, but also in intimate structure, so that not only are
many substances found in nature having a regular shape, but these
can often be cleaved or split readily in a certain way, while if broken
in any other direction they exhibit ragged and uneven edges. Such
bodies are technically said to exhibit structure, because, although the
texture of the interior of other stones and minerals may be equally
manifest, yet in these only does the observation of texture lead to a
knowledge of the mode of formation.
* 245. The various natural history properties of minerals require
to be understood before it is possible to have any distinct notion of
Mineralogy ; and in order to appreciate these properties much atten-
tion must be paid to the subject of form. It is fortunate for the
student that the number of original forms is greatly limited in na-
ture ; and although the number of possible combinations of known
elementary substances is almost infinite, the knowledge of form re-
quired is not so difficult as it might at first seem. We must first
consider the subject as having reference to structure generally, in a
mathematical sense, before proceeding to the other physical charac-
ters, such as the chemical composition, or the mutual relation of the
various physical properties.
"" 246. The regular forms assumed by minerals are well known
under the name of crystals, and the part of mineralogy which refers
to it is thence called CRYSTALLOGRAPHY, or a description of crystals.
The first thing to be done, therefore, is to become familiar with
CRYSTALS. 131
crystals, especially those met with in nature, and to learn the relation
they have to one another, and to simple commensurable solids to
which they can be shown to belong.
_ In the transition from the gaseous or fluid state to the solid,
many substances assume the condition of a regular geometrical solid
bounded by plane faces. Such are the forms most readily recognized
. as ' crystals,' and they occur, whether the solidification takes place
by the separation of the solid from an aqueous solution, or by cool-
ing from igneous fusion. The beautiful crystals occasionally found
in nature, forming part of the earth's crust, and embedded in various
rocks, have, doubtless, been formed under one of these conditions.
In some cases, as in the sublimation of sulphur, a body proceeds at
once from the gaseous state to the solid without passing through the
fluid state. In others, slow cooling from a high temperature to a
much lower one superinduces the same condition, without a transition
from one condition of matter to another.
Each substance usually exhibits a peculiar crystalline form of its
own, although occasionally the same substance crystallizes in two dis-
tinct and incompatible forms, in which case it is said to be dimor-
phous. Sometimes also two different substances are found having
the same crystalline form, and they are then said to be isomorphous.*
These terms will be subsequently illustrated at greater length, and
their bearing on mineralogy considered.
247. When several crystals of the same substance are examined
we do not find amongst them an absolute geometrical identity of
form. The annexed figure (36) represents a group of alum crystals,
in which the actual form is confused, but where the prevalence of
an arrangement of one kind of forms may be readily distinguished.
Widely, however, as different crystals may seem to depart from the
normal or typical form, they may usually be traced to this with more
or less difficulty. Thus, in quartz crystals where the usual form is
that of a six-sided prism terminated by six-sided pyramids, the sides
of the pyramids are by no means always regular and alike, for they
are of various sizes and in various relations to one another, and in
this way are produced many irregularities ; but a careful examina-
tion shows that notwithstanding apparent modifications, and in spite
of all these differences, the angle between corresponding faces in
crystals of the same substance is invariable. Thus the angle between
two sides of the prism of quartz is invariably 120, and the angle
between the adjacent sides of the pyramid is 133 44', and so on.
248. Simple crystalline minerals are generally so constructed and
Dimorphous from (dis) twice and (morphe) form, and Isomorphous from (isos) like, (morphe)
form, signify respectively diversity of crystalline form in the same mineral species, and as-
sumption of the same crystalline form by two different minerals. By crystalline form it is here
meant to include every compatible variety belonging to a distinct system of crystallization. (See
A OQfl 'JAA *
132 MINERALOGY.
so built up of like parts, that, by proper management and a skilful
hand, we can obtain an ultimate or primitive form of each crystal
by splitting off parallel faces of various thickness, or by removing
edges, or angles, which may have replaced faces. To understand this
Fip. 36.
Group of Alum Crystals.
fully requires a little familiarity with the nature and derivation of
solid figures, and the terms employed in speaking of them.
249. The following are the more important laws with respect to this property,
which is technically called cleavaye :
1. It is uniform in all the varieties of the same mineral.
2. It occurs parallel to the faces of a fundamental form or along the diagonals.
3. It is always the same in character parallel to similar faces of a crystal, being
obtained with equal ease, and affording planes of like lustre and conversely, it is
dissimilar parallel to dissimilar planes. Thus it is the same parallel to all the faces
of a cube ; but in the square prism, the cleavage parallel to the base differs from that
parallel to the sides, because the base is unequal to the lateral planes. There may be
an easy cleavage parallel to the base, and none distinct parallel to the sides, as in
topaz ; and the reverse may be true.
4. All simple minerals do not present cleavage, or, at least, the cleavage, in many,
cannot be discovered. Quartz, for example, cannot be cleaved by the knife and ham-
mer ; but it may, sometimes, be made to exhibit the property by plunging it into
cold water, while very hot.
5. Some minerals present peculiar cleavages of subordinate character, independent
of the principal cleavage ; thus, calc spar has, sometimes, a cleavage parallel to the
longer diagonal of its faces.
6. Cleavage extends to rock masses, where it is observed, as in slate, chiefly with
reference to one set of planes. The jointed structure, in many rocks, is also a result
of the same property.*
* Dana's " Manual of Mineralogy," p. 35.
SYMMETRICAL FORMS. 133
250. An angle of a plane figure is well known to be formed by
the inclination of two lines meeting at a point. It cannot, of itself,
enclose any space, since every limited space or area requires at least
three straight lines to enclose it, and must, therefore, have at least
three angles.
An angle of a solid figure, on the other hand, is (see fig. 37)
composed of at least three planes or faces which meet in a point, and
such an angle is called a solid angle. If, therefore, from a solid we
cut off an angle there must be a face instead, and this is called re-
placing a solid angle by a plane face. If there is a regular solid, or
Fig. 37. Fig. 39.
Fig. 38.
a solid formed symmetrically, by faces some of which are similar and
equal (see fig. 38, 39), it is possible to alter or replace the solid angles
symmetrically, and still retain symmetry, but not otherwise. In crys-
tallography it is always supposed that changes in crystals take place
symmetrically.
251. The symmetry here understood is strictly mathematical, and supposes con-
stant reference to perfectly regular and exactly corresponding parts. In the case of
a cube, where the sides are all equal, and the solid angles also exactly equal and
placed in the same way, it would mean acting at the same time in the same way and
to the same extent on all the sides together, or all the solid angles together, or all the
edges together. If, however, the figure should be a prism, such as a double cube, then
the four enclosing sides, the two end planes, the four edges of the sides, and the eight
of the two ends would have to be considered as distinct groups, and any one set could
be acted on independently of the other. Hence arise many of the peculiar modifica-
tions of form seen in crystalline solids, and the necessity of understanding what is
really meant by symmetrically acting on a fundamental or derived form.
252. Besides solid angles and the plane faces which enclose them,
and of which every solid body must have, at least, four, there are
also edges formed by the inclination of each two planes towards each
other, and these are also symmetrical in all regular figures (see fig.
39). If we take the simplest solid as a cube (fig. 41), there will
clearly be six equal sides, or plane faces, all squares ; eight equal
solid angles (each exhibiting three equal plane angles), and twelve
equal edges ; and since each solid angle is made up of three plane
angles, there must be twenty -four plane angles. In this case all the
plane angles are right angles.
253. Now, if a crystal exist in the form of a cube and be cleaved
or split to the same extent parallel to each side, we may thus repro-
134 MINERALOGY.
duce smaller cubes ; but it may also be possible to remove the solid
angles ; and if this is also done symmetrically, or so that each por-
tion removed is exactly alike, we shall obtain a different solid, also
p. 4Q regular, but derived from the cube, and at length
becoming a figure like that shown in fig. 40,
where the letter a marks the original surfaces,
and o the new surfaces produced by the removal
of the solid angles. The new surfaces will be
triangles whose sides are all equal, and the old
surfaces, though reduced in size and changed
in position, are still squares. The figure now
having six square sides has eight triangular ones
besides, and is thence called the cube-octahe-
Cube-octahedron. j *. i i i -,
dron* by which is meant a figure derived from
the cube and octahedron. It has twelve solid angles, six square plane
faces (a), eight triangular plane faces (o) which are derived, twenty-
four edges and forty-eight plane angles. Most natural crystals are
capable of being cleaved or split in some particular directions in accord-
ance with the law of their formation ; and in this way, by aid of
cleavage, we may derive one solid from another, and discover the sim-
ple and fundamental form from the complicated or less simple one.
Crystals modified in this way can only be affected according to the following
laws:
1. All the similarparts of a crystal are similarly and simultaneously modified, or
2. Half the similar parts of a crystal, alternate in position, are modified independ-
ently of the other half.
The following terms are employed in describing the modifications of crystals.
Replacement; an edge or angle is replaced when cut off by one or more secondary
planes.
Truncation ; an edge or angle is truncated when the replacing plane is equally
inclined to the adjacent faces.
Bevelment ; an edge is beveled when replaced by two planes which are respectively
inclined at equal angles to the adjacent faces. Truncation and bevelment can occur
only on edges formed by the meeting of equal planes.
254. In describing the crystalline form of a body it is necessary
to neglect accidental modifications, and consider each surface, or
enclosing plane, as if it were removed or supplied in perfect symme-
try. The ultimate or primitive form thus obtained may be con-
veniently called the ideal crystal, to which the actual crystal only
approximates, sometimes more and sometimes less distinctly (see fig.
36). One reason why the same surfaces do not always exactly cor-
respond in nature is in consequence of accidents of original formation
or subsequent interference, the result being that the general aspect
* Crystalline forms are often described by terms borrowed from the Greek language. Thus,
octa signifies eight, and hedron side; and the following, derived from the Greek numerals, and
constantly used in composition, may be useful to assist the memory of the student: hemi. half;
monos, one ; tetra, four; penta, five; hexa, six; hepta, seven; octa, eight; deca, ten; dodeca,
twelve ; ifeosi, twenty. So also gonos signifies an angle.
SYSTEMS OF CRYSTALLIZATION. 135
of the crystal is often so different from the ideal form, that it is dif-
ficult for the beginner to recognise the one in the other. It is, how-
ever, highly important that this point should be carefully attended
to, since very apparent and considerable modifications in form are
produced by the unequal distance of the plane faces from the middle
point of the crystal.
255. In order to obtain a starting point from which we may more
closely investigate crystalline form, and the comparison of opposite
and corresponding positions of detached plane faces, certain lines
have been assumed in crystals under the name p.
of axes, with regard to which the different
plane faces exhibit a symmetrical position.
The lines, for instance, drawn in fig. 41,
through c the centre of the cube to the middle
points of each side, are of this kind. All the
lines thus drawn are of equal length, and each
makes right angles with the other two. Every-
thing that can be done or described with re-
spect to the solid can be referred to these
lines, and all calculations made much more conveniently with respect
to them than in any other way.
The position of such lines or axes, and the relation of the parts
into which they divide the crystal, is not the same in all cases; and
with respect to this fundamental character six different crystalline
systems have been assumed, to which the greatest attention should
be paid, as they illustrate the whole subject of crystalline form.
256. 1st. The regular (also called octahedral, monometric or
tesseral) system, in which there are three similar and equal axes at
right angles to one another. This system includes the cube, octa-
hedron, dodecahedron, and a number of other well known figures.
2nd. The square prismatic, or di-metric system, with three axes
at right angles to one another, but not all equal to one another.
Includes the square prism and square octahedron.
3rd. The hexagonal system, in which are four axes, of which
three are similar and in one plane, intersecting one another at an
angle of 60, while the fourth axis is dissimilar and at right angles
to the plane. Includes the rhombohedron and hexagonal prism.
4th. The rhombic, prismatic or trimetric system, with three axes
at right angles to one another, but all dissimilar. Includes the right
rhombic prism, right rectangular prism, and rhombic octahedron.
5th. The monoclinic, or oblique prismatic system, having three
dissimilar axes, two of them not at right angles to one another, but
the third at right angles to both of them, and to the plane in which
they are. Includes the right rhomboidal prism, and oblique rhom-
bic prism.
136 MINERALOGY.
6th. The triclinic, or doubly oblique prismatic system, in which
the axes are dissimilar, and no one is at right angles to the others.
Includes the oblique rhomboidal prism.
257. The relative importance of each system will be best understood by the follow-
ing table of 351 minerals referred to crystalline systems in one of the latest works on
Mineralogy (Nicol's " Mineralogy "). Out of the whole number of species there
described (506), 36 are mentioned as amorphous, 64 massive, and 21 compact. Several
are doubtful, some dimorphous, and some isomorphous.
1st Regular system . . . 67
2nd Square prismatic system 33
3rd Hexagonal system 66
4th Rhombic system 107
5th Monoclinic system 64
6th Triclinic system 14
351
It should be mentioned that the rhombohedral forms of the third system are some-
times distinguished from the hexagonal. Of the number of species in the third system
33 belong to the former and the same number to the latter division.
The First, or Regular System.
258. It is usual to consider the regular octahedron as the funda-
mental or ideal, as it is the simplest form, of the regular system. It
is a solid enclosed within eight similar and equal triangles. The
solid angles, the edges, and the angles which the plane faces make
Fi 42 with each other are all equal, the latter being
109 28'. The axes are the lines joining
opposite angles, and are all equal, and at
right angles to one another. In the figure
(42) the angles are marked by the letter A,
the edges by D, and the plane faces by o.
The whole may be regarded as a double py-
ramid perfectly symmetrical in every respect.
The regular octahedron is a form which
many substances, both simple minerals and
the results of artificial manipulation, com-
monly assume. Among them we may mention magnetic iron, and
perfect crystals of alum.
259. Various modifications of the octahedral form are produced
by removing portions of the solid by planes parallel to one or more
of the different plane faces, edges, or solid angles. In this way are
obtained the common crystals of alum, some of the salts of lead, and
many other minerals. The following are simple secondary forms
derived from the octahedron.
1. The cube or hexahedron as seen in fig. 43. In this the solid
angles (A) of the octahedron (fig. 42) are supposed to have been
replaced (or cut off) by plane faces (), and the plane faces (o) by
SYSTEMS OF CRYSTALLIZATION. 137
solid angles (o) ; the edges (D) disappear, and instead of them other
edges (F), are formed at right angles to them. Each of the solid
angles in this case has been removed, as far as the central points of
each of the triangular plane faces.
2. The dodecahedron (fig. 44) is formed by twelve rhombic* faces,
the angles being of two kinds. In this figure the edges (D) of the
octahedron have been replaced by planes (d), the plane faces (o) by
solid angles (o), and new edges (G) are introduced at the intersec-
tion of the planes (d). The original angular points of the octa-
hedron (A) are retained, but the planes of which the angle is made
up are altered.
3. The tetrakis-hexahedron, or pyramidal hexagon (fig. 45), is a
solid of twenty-four faces consisting of a cube surmounted on each
plane face by low pyramids. It is hardly necessary to describe the
Cube. Dodecahedron. Tetrakis-hexahedron.
way in which either this, or the pentagonal dodecahedron (fig. 46) is
derived, further than by mentioning the introduction of faces marked
c?/ 2 , which will readily be seen to have refer-
ence to the faces d, derived in the dodecahedron
from the edges of the octahedron marked D.
There is also the ikosi-tetrahedron, and some
other forms rarely met with, and which need
not here be noticed.
260. Besides the ordinary modifications of
a crystal by the treatment of each part sym-
metrically, there are also to be considered the
half modifications already alluded to. Forms of
this kind are called hemi-hedral, or half-sided :
, , . i , -I -I / ,i Pentagonal dodecahedron.
and one ot the simplest is obtained from the
octahedron, by continuing alternate faces till the intermediate
faces disappear. According to the faces made to disappear, the
result will assume one of the forms represented in the diagrams
* A rhomb is a plane figure, of which the opposite sides and angles are equal, but the angles
are not right angles.
138
MINERALOGY.
Views of the tetrahedron.
figs. 47, 48, which are perfectly equal, but differ in position. The
figure is called the tetrahedron, or four- sided. The polygonal dode-
cahedron (fig. 44), may be derived in the same way and may be
regarded as a hemi-
hedral form easily de-
rived from the tetra-
kis-hexahedron, which
is a twenty-four-sided
figure.
261. We come now
to the cases of com-
bination belonging to
the first system. In
the first of these (fig.
49), the form of the octahedron prevails, and in the next (fig. 50)
Fig .50. the cube form pre-
Fig. 49. ^^^^^^^^^^^^^H ya il s - Both are com-
binations of the cube
with the octahedron.
When the two forms
are equally deve-
loped the resultant
figure is the cube-oc-
tahedron already re-
ferred to (fig. 40).
The next figure (51) represents a combination of the dodecahe-
dron and the octahedron. In this figure the faces (o) of the octahedron
predominate, and the form obtained by the modification is very
peculiar. Fig. 52 is a combination of the cube with the dodeca-
hedron, and fig. 53, that of the tetrahedron with the cube. These
Fig. 51.
Fig. 52.
Fig. 53.
are the principal combinations met with in nature, but we add the
figure of a combination of three forms (see fig. 54), viz., the cube
(a) (which dominates) with the octahedron (o), and the dodecahe-
dron (d).
SYSTEMS OF CRYSTALLIZATION. 139
262. Among the forms of crystalline bodies most important to be known, and
belonging to the first or regular system, are the following. The names of some of the
minerals frequently met with of the different fonns, are added as instances :
Octahedron (o) : Spinelle, Magnetic iron ore. (fig 42.) p- 5^
Hexahedron or cube (a): Fluor spar, Rock-salt, (fig. 43.)
Dodecahedron (d) : Garnet, Hauyne. (fig. 44.)
First ikositetrahedron : Loucite, Garnet, Analcime.
Hemi-octahedron (tetrahedron) : Grey copper, Blende,
(figs 47,48.)
First tetrakis -hexahedron : Gold, Copper, (fig. 45.)
It will be easily understood that, provided the system is
the same, a mineral may present itself in various forms
without being dimorphous. Thus Garnet is sometimes do-
decahedral and sometimes ikositetrahedral.
263. The principal abundant or useful minerals crystalliz-
ing in the first system are the following : Alum, Analcime, Blende, Boracite, Native
copper, Chromate of iron, Diamond, Fluor spar, Galena, Garnet, Gold, Grey copper,
Horn silver, Native iron, Iron pyrites, Leucite, Magnetic iron ore, Native mercury,
Red oxide of copper, Rock salt, Sal ammoniac, Native silver, Smaltine, Spinelle.
The Second, or Square Prismatic System.
264. The fundamental form of this system is the square octahe-
dron, a figure which differs from the regular octahedron in the ver-
tical axis being either longer or shorter than the horizontal axes.
The adjacent figure (55) represents the solid in the latter case. The
Fig. 55. Fig. 56. Fig. 57.
vertical axis in this system has no proportional relation to the
others ; in Zircon, for instance, the relation is as 0*64 to 1, and it
varies with the mineral species.
The eight sides of the square octahedron are not equilateral tri-
angles, but are all equal to each other. The section through the
lateral angles (A) is a rectangle, and is called the base (see fig. 56),
while the section through the vertical angles is a rhomb (fig. 57).
There are thus two dimensions of solid angles, the vertical and
horizontal ; the latter made up of four similar and equal angles, and
the former of four angles, not all similar and equal.
265. In all the octahedrons of the second system the principal
axis joins the two vertical angles, but the secondary axes may have
140
MINERALOGY.
either the position seen in fig. 58, joining the opposite angles of the
base, or that of fig. 59, uniting the middle points of opposite sides.
The two kinds of figures thus formed are called respectively the direct
and the inverse, or octahedrons of the first and second class.
Fig. 58.
Fig. 59.
Fig. 60.
266. The combinations of the second system include, first, that of
the direct and inverse octahedrons with each other, as shown in fig. 60,
which has the edges (D) and the angle (c) replaced by sides d and c.
Fig. 61. Fig- 62.
Fig. 64.
In fig. 61 is a combination of the primitive octahedron with the
right prism of the same class. We have next (fig. 62) the combina-
Fig. 65. tion of the acute octahedron with
the right prism of the second class,
the latter being the principal form ;
and, thirdly (fig. 63), the obtuse
or primitive octahedron, with the
prism of the second class, the octa-
hedron dominating.
When the edges of the long square
octahedron are truncated the resul-
tant figure becomes a prism ; and
this may either remain a parallele-
piped or be terminated with a low
pyramid. Thus the combination of the primitive octahedron with
the right prism of the same class gives the figure represented in 64.
SYSTEMS OF CRYSTALLIZATION. 141
Lastly, fig. 65 represents the primitive (obtuse) octahedron com-
bined with the acute octahedron of the same class and the right prism
of the second class. The prism here dominates.
267. The hemihedral forms of the second system correspond with
those of the first, and the hemi- octahedron is the most important.
Crystals of this kind are derived from the square octahedron of both
classes, just as the tetrahedron is derived from the octahedron, the
faces being isosceles triangles, the edges of two kinds, and the angles
unequal. Copper pyrites occurs in this hemihedral form.
268. The following are the principal minerals of this system, viz. Apophyllite,
Copper pyrites, Idocrase, Rutile, Scapolite, Tin ore, and Zircon.
The Third, or Hexagonal System.
269. The forms which belong to this system have four axes, three
of which are equal and in one plane, making angles of 60 with
each other, and the other axis is at right
angles to the plane in which these are. The
vertical axis is taken as the principal axis.
No relation exists between the length of the
principal and secondary axes. The diagram,
fig. 66, is the principal simple form, and con-
sists of two hexagonal pyramids on a common
hexagonal base. The faces are isosceles tri-
angles. The edges are of two kinds, twelve ter-
minal (D), and six lateral (G). The solid angles
are also of two kinds, two terminal or ver-
tical (c), of six plane faces, and six horizontal
or lateral (A), of four. This figure is the Jiexagonal dodecahedron.
There are two classes of dodecahedrons dependent on the disposition of the
secondary axes with respect to the base. In the first class, the axis join the angles
of the base as in fig. 67, and in the second class they join the middle of the opposite
sides, as in fig. 68. Hence result some combinations and derived forms.
Fi< ? 68 ' Fig. 69.
270. The rhombohedron, or hemi-dodecahedron, is a form derived
from the dodecahedron, and admits of two varieties, the one repre-
142 MINERALOGY.
sented in figure 69, and another having the same relation to this as the
second tetrahedron has to the first. These are the hemihedral forms
of the third system, and they are very important, as the number of
minerals crystallizing in this manner is as large as that in which the
forms are not hemihedral.
271. The combinations in this system are varied, and have con-
siderable interest, but it is not necessary to describe many of them.
In fig. 70 is that of the primitive dodecahedron with the first derived
Fig. 70
Fig. 71.
Fig. 72.
prism. It is the most usual form of Quartz. The next figure (fig.
71) represents the prism combined with the principal rhombohedron.
We sometimes find a hexagonal prism (72) terminated by plane faces
a combination of the prism and the terminal faces.
272. The following are the principal minerals that crystallize in this system in the
complete (holo-hedral) form. Apatite, Chlorite, Copper-nickel, Emerald, Graphite,
Uni-axal or Magnesia mica, Pyromorphite, Quartz, and Red oxide of zinc. The fol-
lowing are usually rhombohedral (hemi-hedral) forms: Native antimony, Native arsenic,
Calamine, Calc spar, Chabasite, Cinnabar, Corundum, Dolomite, Manganese spar,
Spathic iron, Specular iron, and Tourmaline.
The Fourth, or Rhombic System.
273. The characteristic of this system is, that although the three
axes of the octahedron, which is its fundamental form, are at right
angles to one another, as in the regular and square prismatic systems,
no two of them are equal to each other. The relation of magnitude
also is different for different bodies, and no one of the axes can be
considered the principal one; although, for the sake of convenience,
the one most commonly presented as principal in the ordinary form
of any particular crystal is sometimes so designated.
In this system the common base of the octahedrons is a rhomb
and not a square ; it has therefore two obtuse and two acute angles,
and its diagonals are unequal.
It hence results, that of the six angles of the figure there are only
two and two alike, so that they can be symmetrically modified only
SYSTEMS OF CRYSTALLIZATION.
143
to this extent. The only simple form is the right octahedron with a
rhombic base, fig. 73, of which figs. 74, 75 are the sections made by
planes through the terminal edges. Fig. 76 represents the base.
Fig. 73.
Fig 74. Fig. 75.
274. The compound forms of this system are several. In fig. 77
is a combination of two of the octahedrons with a prism and the ter-
minal face. Fig. 78 is the principal octahedron combined with two
vertical prisms ; fig. 79, a combination of horizontal prisms ; and
Fig. 80.
Fig. 77. Fig. 78. BHHHHaH^aH Fig. 81.
fig. 80, a combination of the vertical prism with the terminal face.
Lastly, we have, as in fig. 81, combination of the principal octahe-
dron with the lateral faces a and b.
275. Hemi-hedral forms are presented amongst the crystals referred to the fourth
system ; but they are much more rare in it than in the others. Sulphate of magne-
sia presents a tetrahedron of this nature, and in Manganite there is a combination in
which it appears. There are no hemi-hedral forms of the fifth or sixth systems
found in nature.
276. A very large number of minerals are referred to this system, which appears to
admit of innumerable variations and modifications, resembling each other and often
approximating to the forms of the regular and square prismatic systems. The follow-
ing may be regarded as the most interesting and best known species, Andalusite,
144
MINERALOGY.
Anhydrite, Arragonite, Celestine, Sulphuret of antimony, Harmotome, Heavy spar,
Brown haematite, lolite, Jenite, Manganite, Mesotype, Mispickel, Nitre, Olivine,
Orpiment, Prehnite, Pyrolusite, Ruby silver, Staurotide, Stilbite, Strontianite, Sul-
phur, Talc, Topaz, Wavellite, Witherite.
5th. Monoclinic or Oblique Prismatic System.
277. In this system there are three unequal axes, one at right
angles to the plane in which are the two others, which latter, how-
ever, are not at right angles to one another in that plane.
Fig. 82. The annexed figure (82) is an octahe-
dron of the monoclinic system. It differs
essentially from the octahedrons already
described, not being enclosed by eight
equal triangles, but by scalene triangles
of two kinds. It is not met with in nature
in its simpler forms, being obtained only
in combination. The section obtained
through the terminal edges is represented in fig. 83, and is a paral-
lelogram. The section through the lateral edges, fig. 84, is a rhomb,
and forms the base.
Fig. 84. i n fi gure 82 the
four edges in each
of the two planes
in which are two
axes not at right
angles to one an-
other, are similar
and equal : of the
other edges those opposite one another are similar and equal.
The four surfaces cut off by similar planes at either of the sets of
equal edges form rhombic prisms, of which the edges are in each case
parallel to one of the axes. These may be called oblique rhombic
prisms ; and in all crystals of this system an oblique rhombic prism
may be considered as the prevailing form, which may be so placed
that the edges are in a horizontal plane.
The octahedrons of this group may be much varied in crystals of
the same mineral species, according to the length of their axes. The
combinations vary also greatly ; but though not a true simple form,
one condition of the solid requires to be assumed as the primitive
form, while the others, having relations to this, must be considered as
derived.
278. The oblique octahedrons are figures of which the faces are
inclined at once to each of the three axes ; but there are two other
groups of Monoclinic crystals, those, namely, of which the faces are
inclined towards two axes being parallel to the third, and those in
which the faces are inclined towards one axis, and parallel to two
SYSTEMS OF CRYSTALLIZATION.
145
others. Of these the former are four-sided prisms, which may be di-
vided into three principal classes, viz. Four-sided prisms whose faces
are parallel to the principal axis, and those whose faces are parallel
to the second or third axis respectively. Some of the crystals of
Gypsum (fig. 86), and a combination met with in Mesotype, are
examples of the first case, and fig. 87 (a form of Pyroxene) represents
the second. They are frequent and characteristic combinations.
In the annexed diagrams, fig. 85, represents a combination of the complete prin-
cipal octahedron with the principal vertical prism and the terminal faces. The next
Fijr. 85.
Fig. 87.
diagram, fig. 86, is a combination of the oblique anterior prism ot the principal octa-
hedron with its vertical prism and the terminal face. Fig. 87 is a combination of the
oblique posterior prism of the principal octahedron of Pyroxene with its terminal
oblique posterior face, its vertical prism, and the first and second lateral faces.
279. The following are the most interesting of the minerals referred to the Mono-
clinic system, viz. : Augite, Crocoisite, Cyanite, Epidote, Felspar, Gypsum, Horn-
blende, Hypersthene, Malachite, Mica, Realgar, Sphene, Tabular spar, Talc, Vivianite,
Wolfram.
6th. Tridinic, or Doubly OUique Prismatic System.
280. In this system all the three axes are unequal, and neither
Fig. 90.
of them is at right angles to two others. The octahedron of this
system (fig. 88) never appears in its complete state. It is formed of
eight sides, of which only the pair parallel to one another are equal
L
146
MINERALOGY.
and similar, so that each pair of such sides may undergo modification
differently ; and this is the case also with the edges and angles.
The oblique rhombic prism of the former system corresponds with
the oblique prism of fig. 89 ; but the latter figure has, it will be
seen, only the opposite and parallel faces, angles, and edges equal and
similar. The simple form (fig. 89) is the ideal or fundamental form
of Sulphate of copper.
281. The possible modifications of form of this system are numerous,
and highly complicated, but the forms actually presented in nature are
very few, and it includes but a small number of minerals. One of the
most simple forms is represented in a diagram (fig. 90). It is a crys-
tal of Axinite, and is a combination of the left face of the principal
octahedron with parts of the vertical prism and several faces.
282. The whole number of crystalline minerals referred to this system is but four-
teen, and of these Albite, Axinite, and Labradorite are the only ones of any interest.
283. The ultimate forms of crystals, and the system to which they
must be referred, depending thus entirely on the angles which one
side makes with another, it becomes of the greatest consequence to be
able to measure and determine these angles accurately. As we have
already shown, the system may be determined theoretically by re-
placing the missing angles, edges, or sides ; but since the change of
form in a true crystal is always symmetrical, and' the natural faces,
which may easily be determined, are all inclined at the true angle
towards each other, the measurement of this angle is a mechanical
operation, requiring some care and some knowledge of Crystallo-
graphy. Instruments have been contrived for the purpose, under
the name of Goniometers (gonos, an angle ; meter, measure).
284. The common goniometer (fig. 91) consists of a semicircular
arc, divided into 1 80 degrees, and terminated by a diameter, a b.
It is provided with two arms,
one of which (g K) is capable
of a sliding motion in the
direction of the diameter,
along which it is placed, and
the other arm (df) turns
on the centre of the arc.
Each of these arms is parti-
ally slit, to allow of the parts
on one side of the centre
p- j
being shortened,
admit of a more
and thus
Common Goniometer. admit of a more accurate
measurement of small crystals. The faces of a crystal whose angle
of inclination is to be measured, are applied between these arms
when opened just sufficiently to admit them ; and when the arms
GONIOMETERS.
147
are found, on close examination, to touch them both along the
whole length, the number of degrees may be read off on the edge of
the revolving arm.
In the absence of such an instrument, results, often sufficiently
near, may be obtained by making a pair of extempore arms of card,
and laying off the angle when measured on a piece of paper, when
it may be determined either by a scale or any graduated arc. It
is seldom that by the common goniometer we can measure within a
quarter of a degree of truth, and this is rarely sufficient to have any
important scientific value.
285. The reflecting goniometer is a far more accurate instru-
ment than the former, and may be applied with as much convenience
to very minute crystals, which are generally more perfect, as to
larger ones which alone can be measured by the former instrument.
It is found that surfaces of r ^th part of an inch are sufficiently
large for the purpose of determination by it.
The instrument (fig. 92) consists of a movable circle, LL, having
a rim graduated to half degrees, and a fixed vernier scale for more
Fig. 92.
WollMtotft reflecting Goniometer.
minute measurements. A hollow main axis, a b, passes through the
centre of the circle, and another, a c, passes through it, turned by
the handle s, by which the crystal only is moved, in order to com-
plete its adjustment. The crystal, z, being then conveniently fixed,
by means of a piece of wax or in any other way, upon the extremity
of the smaller axis (and it is necessary to be so fixed that a line
148 MINERALOGY.
drawn on the face to be examined is parallel to the main axis) the
circle is set with the mark of 1 80 opposite the zero point of the
vernier, and a horizontal line, previously assumed as a mark, is ob-
served by reflection from the face of the crystal to coincide with
another corresponding mark, the eye being brought quite close to
the crystal and almost in contact with it. A bar of a window-
frame may be selected as one mark, and a horizontal line on a slate
as another, and the main axis is then turned until the same line
is seen reflected in the next face of the crystal into the same place.
The angle between the faces may then be read off by the assist-
ance of the vernier. The circle is placed vertically by the aid of the
screws x, and the support p q r, and is moved by the handle v.
It is not difficult to understand the optical principle on which this instrument is
constructed. If the eye observes an object by reflection from the plane surface of a
crystal, and the crystal be turned round until another face represents the same object
in the same spot, the crystal must have been turned through an angle equal to the
difference between the angle of the two faces, and the angle of the crystal can be
thus obtained.
This reflective goniometer was invented by Dr. Wollaston. It is a convenient and
elegant instrument, admitting of very great accuracy of measurement, and not diffi-
cult to manage with a little practice. Other reflecting goniometers have been em-
ployed by Mitscherlich, Babinet, Adelmann, and others, chiefly for purposes of very
minute observation in particular cases, or where the ordinary instrument fails.
286. We have been considering in the preceding pages crystals
whose form is theoretically perfect; but it is very rare that such
perfection is found in specimens of minerals presented for observa-
tion, and if it does occur, the size is generally extremely minute.
Many faces in the crystals commonly met with are deformed, im-
perfect, broken, rudimentary, or altogether wanting, and the very
grouping together of a multitude of individuals prevents any one of
93. them from retaining its
normal condition. Thus,
for example, the form of
quartz crystals usually
approximated is the hex-
agonal prism terminated
by two hexagonal pyra-
mids, as in fig. 93, but the
shape commonly found is
often extremely different.
In the case of carbonate
of lime again, the usual
normal form is the rhom-
bohedron (fig. 94), the angle being 105 5'; but the cleavage being
very perfect in three directions parallel to the faces of the solid, a
great variety of other rhombohedrons may be obtained, more or less
flattened.
VARIETIES OF CRYSTALLIZATION. 149
287. In their primitive forms crystals never present re-entering
angles, but such appearances are not unfrequent in cases where two
or more crystals grow as it were out of one base. Sometimes there
is a certain degree of symmetry in the way in which individuals of
a group collect themselves together, as in the crystals represented in
fig. 95 (the form usually assumed by the mineral called Staurotide),
and usually " twin crystals," as such cases are sometimes called,
exhibit distinct marks of their origin. The form represented in
fig. 96 is another example of complicated form, often presented by
gypsum. It may be easily derived from the more simple form in
fig. 97, already described ( 278,) by cutting this latter into two
parts by the plane omnpqr, and making one half perform half
a revolution with respect to the other. Such an arrangement is
Fig. 95. Fig. 97.
Fig. 96.
sometimes called hemitropy, and the crystal, as in fig. 96, is called a
hemltrope. Twin crystals are also called ' macles.'
288. Crystals are occasionally found with curved faces, an acci-
dent of structure more common in some minerals than others, and
not unfrequent in the Diamond. Spathic iron and Pearl spar, in like
manner, present curved rhombohedrons ; and certain minerals, as
Alabaster and Carbonate of lime, very frequently exhibit curved crys-
talline forms even more curious and distinct. Other minerals run
into greatly elongated and needle-shaped crystals, and are thence
called acicular. Ice, when crystallized, often assumes very strange
and sometimes extremely beautiful forms, seen both in the snow-flakes
that fall through the atmosphere, and in the rime or hoar-frost that
forms on windows during cold weather. The rate of crystallization
very greatly influences the result, and for the elaboration of large
groups time seems absolutely required. Any interruption in the
process of crystallization is probably always marked in the crystal
that results, and the mode of growth is laid bare when these inter-
ruptions have been regular. Crystals of quartz often show a gradual
accretion of this kind.
150 MINERALOGY.
289. Crystalline form is not absolutely to be depended on in the
determination of minerals, since there are cases in which the same
mineral presents itself under more than one form, the forms being
incompatible or referable to different crystalline systems, while,
occasionally, different minerals appear in the same or very nearly
the same form. The former case is denominated dimorphism, or
polymorphism, according as the number of different forms presented
is two or more, and the latter is isomorphism. In a similar way,
when minerals crystallize in nearly the same form, they are said
to be plesiomorphs. False or imitative forms of crystals are some-
times met with, and are called pseudomorpks, while even the true and
determinable forms are rarely complete, and exhibit numerous com-
plications and irregularities. Of these conditions and the chemical
principles involved, isomorphism is the most interesting, and will
demand the most careful attention. Whatever also may be the true
form of a mineral, it is, as we have seen, generally complicated by
position and circumstances, thus adding not a little to the other diffi-
culties of accurately determining mineral species. Certain substances
appear especially liable to anomalous varieties of form connected with
their mode of accretion; and others, although to a certain extent
regular, exhibit a singular want of symmetry in some particular
directions. Hemihedral forms, already alluded to, belong to this
group, and certain crystals in which a very large quantity of some
foreign substance or impurity is present, are also of the same kind.
The crystals of Fontainbleau sandstone are examples in point. They
consist of about one third part carbonate of lime, and the rest sand,
and appear in rhombohedrons.
290. The following are examples of minerals frequently presented in an unsymme-
trical form, viz. : Iron pyrites (cube), Grey cobalt (cube), Grey copper (tetrahedron),
Sulphuret of zinc (tetrahedron), Boracite (cube), Arseniate of iron (cube), Copper
pyrites (prism with square base), Quartz (rhombohedron ), Tourmaline (rhombohe-
dron), Phosphate of lime (regular prism with six faces), Silicate of zinc (right rhom-
bic prism). We have named in each case the proper or symmetrical form, from
which the unsymmetrical crystals are derived.
291. Dimorphism (from dis, twice, and morphe, form) was first ob-
served in the case of Carbonate of lime, which in addition to the usual
type of crystallization, seen in Calc spar, is presented also in Arrago-
nite, in a totally distinct and incompatible form ; but since this fact
was determined many other similar examples have been found, and
they appear to have reference to the existence of peculiar conditions
of solidification. The following list includes all substances at pre-
sent recognised as dimorphous, viz., Sulphur, Carbon, Oxide of
titanium, Specular iron ore, Iron pyrites, Carbonate of lime, Car-
bonate of iron, Carbonate of lead, Arsenious acid, Sulphate of mag-
nesia, Sulphate of zinc, Seleniate of zinc, Seleniate of nickel, and
Chromate of lead, some of the latter salts passing from one crystal-
ISOMORPHISM. 151
line system to another by the application of heat. Other substances
have been described as presenting themselves in more than one sys-
tem of crystallisation, but there is some doubt concerning them.
Others again are trimorphous, or polymorphous, presenting them-
selves in more than two forms, and of these, Sulphate of nickel is an
example. The fact of the same body existing in more than one
usual condition, and having different physical characteristics, has
been called by Berzelius allotropy (allotropos, of a different nature),
and includes polymorphism, which relates only to crystalline form.
Carbon is a good example of this condition, as it crystallises per-
fectly in the Diamond, imperfectly in Graphite, and is amorphous,
but quite distinct, in Anthracite and Coal.
292. Isomorphism (isos, the same, morphe, form), a converse phe-
nomenon to that of allotropy, is not unfrequently found to occur in
crystalline minerals, and is far more important than it, as indicating
natural relations between elements not otherwise resembling each
other in their properties. By it is meant a close resemblance or
actual identity of crystalline form in minerals, when one element, or
proximate element, is replaced by some other. It is not easy at
present to say exactly how far the general principle of isomorphism
is accurately true ; but as an example of its action in well known
minerals it may be sufficient to give the following measurements of
the angle of the rhombohedron, into which the following minerals
(all carbonates) crystallize :
Calc spar (carbonate of lime) 105 8'
Diallogite (carbonate of manganese) 106 51' 107
Spathic iron (carbonate of iron) 107
Dolomite (carbonate of lime and magnesia) 107 25'
Calamine (carbonate of zinc), 107 40'
293. Although, according to the most general view of the
nature of isomorphism, there is no limit to the replacement that can
take place in different bodies, still there are in fact such widely dif-
ferent degrees according to which bodies are isomorphous, that tables
of these degrees afford very important information ; we quote there-
fore from Graham's Chemistry the following list of known isomor-
phous groups :
1. Sulphur, Selenium, Tellurium.
2. Magnesium, Calcium, Manganese, Iron, Cobalt, Nickel, Zmc 4 Cadmium, Copper
Chromium, Aluminum, Glucinum, Vanadium, Zirconium.
3. Barium, Strontium, Lead.
4. Tin, Titanium.
5. Platinum, Iridium, Osmium.
6. Tungsten, Molybdenum, Tantalum.
(And ivith two atoms of the preceding elements.)
7. Sodium, Silver, Gold, Potassium.
8. Chlorine, Iodine, Bromine, Fluorine.
9. Phosphorus, Arsenic, Antimony, Bismuth.
152 MINERALOGY.
In addition to the above isomorphous elements it may be well to append here a short
list of remarkable isomorphous compounds :
10. Alumina, Peroxide of iron, Peroxide of manganese.
11. Lime, Magnesia, Protoxide of iron, Protoxide of manganese, Protoxide of zinc.
12. Baryta, Strontia, Oxide of lead.
13. Phosphoric acid, Arsenic acid.
294. A peculiar kind of isomorphism has been noticed, which
appears not unlikely to have important influence in the mineral
kingdom, and which consists in the substitution of water for other
substances, without change of form being induced. By the analysis
of a great number of minerals it appears that one atom of magnesia,
protoxide of iron or protoxide of manganese, and probably also of
oxide of zinc, protoxide of nickel and protoxide of cobalt, may be
replaced by three atoms of water ; and one atom of oxide of copper
by two atoms of water, without change of crystalline form. This
is called polymeric isomorphism* (polys, many, meros, a part).
The water in these cases is a proximate element.
295. Pseudomorphism (pseudos, false, morphe, form), or the occur-
rence of a mineral in a form not its own, and not obtained by the
regular process of crystallization, occurs in various minerals, and is
chiefly owing to external conditions which have limited the direc-
tion and extent of the development of the mineral. Thus crystals
of quartz form in, and adapt themselves to, the cavity left by crystals
of fluor spar which have been removed j and other similar instances
have been from time to time observed, some well known and strik-
ing examples of which are subjoined.
296. Specular iron, properly rhombohedral, has been observed in octahedrons hav-
ing the form of Magnetic iron ore, from which it has been no doubt derived. Crystals
of Carbonate of lead are changed into Minium, or oxide of lead'; Minium into Galena;
Witherite, or carbonate of barytes into Sulphate ofbarytes, or heavy spar ; Wolfram, or
tungstate of iron, into Tungstate of lime, &c. So, also, but less easily explained, we
find Prehnite imitative of Analdme and Laumontite , Steatite of Quartz, Cole spar, Spi-
nelle and Hornblende ; Quartz of Cole spar.
297. Pseudomorphous crystals are generally distinguished by
having a different structure and cleavage from that of the mineral
imitated in form, their angles are generally rounded, their surfaces
dull, their texture is more or less granular, and their hardness differ-
ent. This phenomenon may be due, first, to a change of composition
by aqueous or some other agency, without the original crystal losing
its form ; secondly, by the actual, but gradual, and atomic removal of
one mineral and replacement by another ; thirdly, by simple infil-
tration into the cavity left by a decomposed crystal ; and, fourthly,
by the incrustation of one mineral upon another, by which process
we first have the form of the original crystal repeated in that of the
incrusting one, and then perhaps, by the subsequent removal of the
first hollow, as well as pseudomorphous crystals of the second.
* First discovered by Scheerer, and referred to in Gmelin's "Hand-book of Chemistry."
English translation, (published by the Cavendish Society), vol. i. p. 93.
PSEUDOMORPHISM. 153
298. The process of fossilization or petrifaction, by which organic
bodies become changed into stone, and capable of indefinite preser-
vation in the earth, is of this kind. It appears in the most perfect
cases to be a substitution, particle by particle, of some permanent
mineral substance, as quartz, carbonate of lime, sulphate of lime, or
others, for each particle of the original organic compound. In the
case of wood and the soft parts of animals the actual cellular tissue is
replaced, and though in other examples the interstices between
adjacent particles may only be filled up so to form a cast of the
original, yet is this cast so true a representative of the most minute
organization as to retain every point of structure, and endure the
most careful examination under the best microscopes, without yield-
ing any evidence as to the nature of the change or substitution that
has been made.
299. Although when definite form and structure are observable
in minerals, there can be no question as to the advantage, and even
necessity, of referring to it as a means of determining species, still
there remain a vast multitude of substances which have definite and
most important properties, but no distinct crystalline form or struc-
ture, and which therefore, in technical language, are called amor-
phous (a, privative, and morphe, form). Some bodies assume the
crystalline and amorphous form almost indifferently, and according
to the circumstances of their passage into the solid state ; some
are more inclined to assume the one form, and some the other, while
other again are rarely or never found in the crystalline state. Thus
quartz occurs both amorphous and crystalline in great abundance
everywhere, and is chiefly crystalline in mountain districts. Carbon
occurs amorphous in anthracite and coal, and crystallized in the dia-
mond and graphite. Carbonate of lime is amorphous in common
limestone, semi-crystalline in marble, crystalline in calc spar; and so
also with a vast variety of other substances. There are two means
by which the nature of amorphous bodies may be determined, one
mechanical, and involving a consideration of the physical properties
of the substance ; the other chemical, and requiring an analysis of
the contents, and a determination of the proportions of each. We
proceed in the next chapter to consider these, as affording the best
methods for determining mineral species.
300. There is yet another condition to be noticed before concluding this part of
the subject it is a difference in the properties of compound bodies, probably arising
from the different grouping of the simple atoms which make up a compound atom.
Thus, when two or more compounds exhibit different physical and chemical rela-
tions, but are found to possess the same composition, they are called isomeric (z'sos,
equal ; meros, a part). Most of such instances occur in organic and not in inorganic
chemistry, and therefore, it is not necessary here to refer to them more in detail.
True isomeric conditions are at present recognised in the mineral kingdom with regard
to phosphoric acid, tellurous and telluric acid, peroxide of tin and tartaric acid.
154
CHAPTER VIII.
PHYSICAL AND CHEMICAL CHARACTERISTICS OF SIMPLE
MINERALS.
301. THE characteristics of simple minerals, including those that
are amorphous, are, 1st. Conditions of structure or texture : 2nd.
Optical peculiarities ; 3rd. Phosphorescence ; 4th. Electricity and
Magnetism ; 5th. Odour ; 6th. Taste ; 7th. Hardness ; 8th. Specific
Gravity ; and 9th. Chemical Composition. Of these the first eight
are generally described as physical, and are determined at once by
the senses or by mechanical agency. The last, or chemical structure,
requires the assistance of chemical action, and involves a certain
extent of decomposition to determine it.
302. The CONDITIONS OF STRUCTURE of minerals are seen in their
texture, state of aggregation, and fracture. The former is either
columnar, lamellar, or granular, and the different kinds of each are
thus distinguished :
1. Columnar texture is that which is made up of minute fibres or
prisms, closely compacted together. It is common in the seams of
rocks, and sometimes in incrustations. It may be of the following
kinds :
Fibrous, or with delicate parallel fibres. Ex., Gypsum and Asbestus.
Retictdated, with the fibres crossing and resembling a net.
Stellated, with fibres radiating from a centre and producing a star-like appearance.
Ex., Stilbite, Wavellite.
Radiated and divergent, fibres radiating but not stellar. Ex., Quartz, Grey antimony.
2. Laminated texture exhibits laminse or leaves (parallel plates),
either thick or thin, separating easily or with difficulty.
Foliaceous, leaves thin and separating easily. Ex., Mica, whence this variety is
sometimes called micaceous.
Tabular, laminae thick. Ex., Quartz, Heavy spar.
The laminae may be elastic, as in Mica ; flexible, as in Talc or Graphite ; or brittle, as
in Diallage. They are also sometimes arranged in stellar shapes, as in Mica.
3. Granular texture. This term explains itself, and admits of
the following varieties :
Coarse Granular, as Granular marble.
Fine Granular, as Granular quartz, Specular iron.
Impalpable, as Chalcedony, Opal.
Friable, or easily crumbled by the fingers.
303. Massive minerals also take certain imitative shapes, not
peculiar to either of these varieties. The following terms are used
in describing them :
Globular, when the shape is spherical, and the structure either radiating or concen-
CONDITIONS OF STRUCTURE. 155
trie. When they are attached in groups they are said to be implanted. Iron pyrites
is often presented in this form.
Reniform, or kidney-shaped.
Botryoidal, when a mass consists of a number of rounded prominences like a bunch
of grapes.
Mammittary, resembling the former, but consisting of larger prominences.
Filiform, like a thread.
Acicidar, slender like a needle.
Stalactitic, cylindrical or conical, hanging from the roof of a cavern or cavity. Car-
bonate of lime, Brown iron ore, Malachite and Chalcedony, are the chief minerals
found in a stalactitic form.
Drusy a cavity is said to be drusy when it is lined with distinct crystals. A
mineral having a drusy cavity is sometimes called a geode.
304. The state of aggregation of minerals exhibits another pecu-
liarity of structure ; and in this sense solid minerals may be brittle,
sectile, malleable, flexible, or elastic terms which are used in the
following senses :
A mineral is called brittle if the particles lose their coherence and separate with a
grating noise into powder, when we attempt to alter their respective situations in the
substance. Of this kind are the gems, spars, pyrites, and many other minerals.
If a mineral is malleable, the particles, when detached by a knife, do not lose their
connection ; so that from such a mineral we may detach slices, as from metallic lead.
Many minerals, such as Mica, cannot be sliced, and when cut, lose their mutual
connection ; but instead of flying about remain quietly upon the instrument. These
are called sectile, and are intermediate between brittle and malleable.
Minerals are flexible if the particles admit of their relative situations being changed
and do not resume their former position ; and, lastly, they are said to be elastic,
if, having been so changed, they resume their former situation when the force is
removed.
305. The fracture of a mineral is a character that has sometimes
been noticed, and, so far as it is distinguished from cleavage, is the
irregular structure observable in breaking a mineral by violence in
any direction. Sometimes the face presented by the broken mineral
is round and smooth, resembling the inside of a shell, in which case
it is called conchoidal. Other kinds of fracture are distinguished as
uneven, even, fibrous, or splintery terms which explain themselves,
and hackly, by which is meant the appearance presented when a
metal such as gold is torn asunder. All regular fracture must be
considered as cleavage.
306. The OPTICAL PROPERTIES OF MINERALS are such as depend
on light, and are only observable in its presence. They include
colour and streak, lustre, transparency, iridescence, refraction, and
polarisation, and may unquestionably be of great importance in some
cases.
307. By COLOUR is meant the colour of the entire mineral ; and
this may be either metallic or non-metallic. The metallic colours
are as follow : *
* The subjoined table is from Hardinger's translation of " Mobs' Mineralogy." It will be
found useful in many cases.
156 MINERALOGY.
. 1. Copper-red; the colour of Native copper, and, less distinct, Copper-nickel.
2. Bronze-yellow ; Iron pyrites.
3. Brass-yellow ; Copper pyrites.
4. Gold-yellow; Gold.
5. Silver-white ; Native silver, Arsenical pyrites (mispickel), Cobaltine.
6. Tin-white ; Mercury, Native antimony, Native arsenic.
7. Lead-grey ; Galena, Sulphuret of molybdenum, Vitreous silver.
8. Steel-grey ; Native platina, Graphic tellurium.
9. Iron-black ; Magnetic iron ore, Specular iron ore, Grey copper.
The following are non-metallic colours :
WHITE.
1. Snow-white; Carrara marble, Arragonite.
2. Jteddislirwhite ; varieties of Calc spar and Quartz, Dolomite.
3. Yellowish-white ; varieties of Calc spar and Quartz.
4. Greyish-white ; Granular limestone.
5. Greenish-white ; Amianthus, Talc.
6. Milk-white; Opal.
GREY.
7. Bluish-grey ; Hornstone, varieties of Carbonate of lime.
8. Pearl-grey ; Horn silver, Quartz, Heavy spar.
9. Smoke-grey ; Flint (dark varieties).
10. Greenish-grey ; Cat's eye and other varieties of Quartz, Mica.
11. Yellowish-grey; Compact limestone, Flint.
12. Ash-grey; Epidote, Leucite.
BLACK.
13. Greyish-black; Basalt, Lydian stone, Anthracolite.
14. Velvet-black; Obsidian, Schorl.
15. Greenish-black ; Pyroxene.
16. Brownish-black; Coal, Mica.
17. Bluish-black ; Black cobalt.
BLUE.
18. Blackish-blue; Azurite (dark varieties).
19. Azure-blue ; Lapis lazuli (bright var.), Azurite (light var.)
20. Violet-blue ; Amethyst, Fluor spar.
21. Lavender-blue ; Lithomarge, Porcelain jasper (var.).
22. Plum-blue ; Spinelle (rare var.), Fluor spar.
23. Prussian-blue ; Sapphire (bright var.), Cyanite.
24. Smalt-blue; Gypsum (several var.).
25. Indigo-blue ; Vivianite (phosphate of iron).
26. Duck-blue ; (blue, with much green and a little black), Spinelle (var. Ceylanite)
Talc.
27. Sky-blue ; Liroconite (arseniate of copper), Fluor spar.
GREEN.
28. Verdigris-green (green much inclining to blue) ; Amazon stone.
29. Celandine-green (green with blue and grey) ; Chlorite, Beryl (var.).
30. Mountain-green (green with much blue) ; Beryl, Topaz, Aqua-marine.
31. Leek-green (green with a little brown) ; Prase.
32. Emerald-green ; Beryl, Emerald, Malachite (var.)
33. Apple-green (light green with a little yellow) ; Chrysoprase.
34. Grass-green ; Green diallage, Malachite, Uranite.
35. Pistachio-green (green with yellow and a little brown) ; Olivine, Epidote.
36. Asparagus-green (pale green with much yellow) ; Asparagus stone, Grossular
(Garnet).
37. Blackish-green ; Serpentine, Augite (var.).
38. Olive-green ; Garnet, Pitchstone, Olivine, Pharmaco-siderite.
VARIETIES OF COLOUR. 157
39. Oil-green (pale green with very little yellow and brown) ; Blende, Beryl,
Pitchstone.
40. Siskin-green (light green very yellow) ; Uranite, Pyromorphite.
YELLOW.
41. Sulphur-yellow; Sulphur.
42. Straw- yellow (light yellow with a little grey) ; Topaz (var. Pycrite).
43. Wax-yellow (yellow with grey and a little brown) ; Common opal, Molybdate
of lead.
44. Honey-yellow (yellow with a little red and brown) ; Calc spar, Fluor spar,
Amber.
45. Lemon-yellow (purest yellow) ; Yellow orpiment, Uran ochre.
46. Ochre-yellow (yellow with brown) ; Quartz and Massive quartz, with Oxide of
iron.
47. Wine-yellow (pale yellow with a little red and grey) ; Topaz, Fluor spar.
48. Cream-yellow (pale yellow with a little red and very little brown) ; Lithomarge.
49. Orange-yellow (yellow inclining to red) ; Molybdate of lead (var.).
RED.
50. Aurora-red (red with much yellow) ; Red orpiment.
51. Hyacinth-red (red with yellow and a little brown) ; Hyacinth, Garnet.
52. Brick-red ; Stilbite, Porcelain jasper.
53. Scarlet ; Cinnabar, Ruby-silver.
54. Blood-red; Pyrope-garnet.
55. Flesh- red ; Heavy spar.
56. Carmine ; Spinelle, Red oxide of copper.
57. Cochineal-red ; Red silver, Garnet.
58. Rose-red ; Rose-quartz, Carbonate of manganese.
59. Crimson ; Ruby, Cobalt-bloom.
60. Peach-blossom-red (red with white and some grey) ; Lepidolite, Cobalt-bloom.
61. Columbine-red (red with a little blue and much black) ; Garnet.
62. Cherry-red (dark red with much blue and a little brown) ; Red antimony.
63. Brownish-red , Red ochre.
BROWN.
64 . Reddish-brown (brown with much red) ; Blende, Zircon.
65. Clove-brown (brown with red and a little blue) ; Axinite, varieties of Quartz.
66. Hair-brown (brown with a little yellow and grey) ; Wood opal, Brown iron
ore (hydrous oxide).
67. Brocoli-brown (brown with blue, red, and grey rare) ; Zircon.
68. Chesnut-brown (purest brown) ; Egyptian jasper.
69. Yellowish-brown (brown with much yellow) ; Flint, Jasper.
70. Pinchbeck-brown (yellowish-brown with metallic lustre) ; Mica (several varieties).
71. Wood-brown (brown with yellow and grey) ; Amianthus (var. Mountain wood).
72. Liver-brown (brown with grey and a little green) ; Common jasper, Quartz,
Cobalt-ochre.
73. Blackish-brown (brown with much black) ; Brown-coal.
308. Besides these there exist a great number of shades or varie-
ties, which may be expressed by the indications of those two which
they most nearly represent. Colours may also differ in intensity,
and may be spoken of as pale, light, deep, or dark, according to their
quality.
The varieties of colour occurring in the same species form unin-
terrupted series, which cannot well be described, but which deserve
study. Fluor spar offers a good and simple example of this series
158 MINERALOGY.
of colours. Several of the gems, as Diamond, Sapphire, Topaz, and
Emerald also afford instructive series.
309. The streak is the appearance presented when a mineral is
scratched with a sharp instrument, in which case either a powder is
produced, or the scratched place assumes a higher lustre than before.
The best method of observing the colour of the powder is to rub the
mineral on a piece of porcelain biscuit or a file till the powder
appears. Some minerals retain their colour in the streak, as spars,
and white varieties generally ; others change colour, as many oxides
and sulphurets of metals ; while others, again, are too hard to
exhibit any change. The student should be aware that a heap of
very fine powder is white, whatever the substance from which it is
obtained.
310. LUSTRE depends on the nature of the surface of a mineral,
which causes light to be reflected in different ways and to a different
extent. There are thus various kinds of lustre and many degrees.
There are six kinds of lustre, as follows :
1. Metallic, the usual lustre of metals ; imperfect metallic-lustre is expressed by
the term, sub-metallic.
2. Vitreous, the lustre of broken glass. An imperfect vitreous lustre is termed
sub- vitreous. Both the vitreous and sub- vitreous lustres are common. Quartz pos-
sesses the former in an eminent degree ; Calcareous spar often shows the latter. This
lustre may be exhibited by minerals of any colour.
3. Resinous, lustre of the yellow resins. Ex., Opal, Zinc-blende.
4. Pearly, like pearl. Ex., Talc, Native magnesia, Stilbite, &c. When united with
sub-metallic lustre, the term metallic-pearly is applied.
5. Silky, like silk ; it is the result of a fibrous structure. Ex., Fibrous carbonate
of lime, Fibrous gypsum, and many other fibrous minerals, more especially those which
in other forms have a pearly lustre.
6. Adamantine, the lustre of the diamond. When sub-metallic, it is termed me-
tallic-adamantine. Ex., some varieties of White lead ore.
The degrees of intensity are denominated as follows :
1. Splendent, when the surface reflects light with great brilliancy, and gives well-
defined images. Ex., Elba iron ore, Tin ore, some specimens of Quartz and Pyrites.
2. Shining, when an image is produced, but not a well-defined image. Ex., Calca-
reous spar, Celestine.
3. Glistening, when there is a general reflection from the surface, but no image.
Ex., Talc, Copper pyrites.
4. Glimmering, when the reflection is very imperfect, and apparently from points
scattered over the surface. Ex., Flint, Chalcedony.
5. Dull. A mineral is said to be dull when there is a total absence of lustre.
Ex., Chalk.
311. TRANSPARENCY is the property which many substances
possess of transmitting light, and we have chiefly to observe with
reference to it the relative quantity of light transmitted. These
degrees are :
1. Transparent, allowing small objects to be distinctly seen.
2. Semi-transparent, allowing objects to be obscurely seen.
3. Translucent, allowing light to pass, but no object to be seen.
REFRACTION AND POLARIZATION OF LIGHT. 159
4. Sub-translucent, when the acute edges of a mineral allow some light to pass.
5. Opaque, not transmitting any light.
Few species of a non-metallic appearance are perfectly opaque,
and some, though opaque in one direction, allow light to pass
through them in another. Many minerals vary exceedingly in the
degree of transparency they present.
312. Under the term IRIDESCENCE may be included a play, or
change of colours, opalescence, tarnish, and other peculiarities, often
very remarkable, and well distinguishing certain minerals. It is
necessary to define these briefly.
Play of Colours, describes the condition when several prismatic colours appear in
rapid succession on turning the mineral. They are well seen in the Diamond and in
precious Opal.
Change of colour is seen as in Labradorite, when the colours alter slowly on turning
in different positions.
Opalescence is seen when there is a milky or pearly reflection from the interior of a
specimen, as in some Opals and in Cat's eye.
Iridescence occurs when prismatic colours are seen within a crystal. It is usually
an effect of fracture, and is common in Quartz, Selenite, and sometimes in Calc spar.
Tarnish is when the surface-colours of a mineral differ from the true and internal
colour. It is the result of exposure, and sometimes presents the hues of the rainbow.
Peacock-ore (Copper pyrites) is an example.
313. POLYCHROISM is a property belonging to some prismatic
crystals, presenting a different colour in different directions. The
term dichroism is sometimes used, the colours occurring only in
two directions, as in lolite, hence called Dichroite. Mica is another
example. The different colours are observed only in crystals with
unequal axes. The colours are the same in the direction of equal
axes, and often unlike in the direction of the unequal axes a
principle at the base of polychroism.*
314. REFRACTION and POLARIZATION of LIGHT. A ray of light
proceeding from any object, and passing from any one medium or
transparent substance to another, is more or less bent out of its
original direction, and this bending is called refraction. Thus,
when a straight stick is held aslant in water it appears bent at the
contact of air and water ; and all transparent minerals bend aside
rays of light to a certain extent, dependent on their structure.
The index of refraction, therefore, or the measure of the extent to
which light is bent aside on passing into a mineral, is one means of
identifying it. The accidental colours presented by certain sub-
stances modify this measure, and in the cases of dimorphism referred
to in the last chapter the refraction is different in the two forms
assumed by the same mineral. Sir Isaac Newton suspected the true
chemical composition of the diamond from observing its high refrac-
tive power.
315. When a ray of light is passed through certain minerals,
* Dana's " Manual of Mineralogy," p. 75.
160 MINERALOGY.
instead of continuing its course as usual, after being bent aside on
entering the new surface, it is separated into two parts, each part
undergoing a different refraction and ultimately emerging by itself.
An object seen through such a mineral appears double, and the phe-
nomenon is called double refraction. Jt occurs very distinctly in
Iceland spar, but extends to all crystalline minerals belonging to
such of the fundamental forms as have unequal axes. When the object
in these cases is seen through the vertical axis, it appears single, but
in all other directions double. Double refraction affords a most
important means of determining minerals, since it is derived from the
intimate structure of the substance, and is not affected by the admix-
ture of slight impurities. It is usual to consider one of the two rays
transmitted after double refraction as the regular, and the other as
the extraordinary ray. Generally, the extraordinary ray is further
removed from the axis of the crystal than the other, but this is not
always the case.
316. When light is thus refracted doubly the extraordinary ray
exhibits a peculiar property, called polarization, and if afterwards
viewed through a thin plate or slice of another doubly-refracting
crystal, it becomes alternately visible and invisible as the latter plate
is revolved, and it also presents a curious display of prismatic colours.
Light may undergo this change of condition, or become polarized,
by reflexion at a certain angle from most substances, or by passing
through thick plates.
317. PHOSPHORESCENCE. The property of emitting light either
by friction or when gently heated, is called phosphorescence, and is
possessed by several minerals. It is exhibited in quartz by friction,
light being readily evolved with a peculiar smell when one piece is
rubbed against another, and the mere rapid motion of a feather
across some specimens of Blende (sulphuret of zinc) will often pro-
duce light of more or less intensity. Although comparatively few
minerals are phosphorescent by friction, many exhibit light of this
kind when exposed to a certain temperature, and the light is often
of different colours. Exposure to heat, however, destroys the phos-
phorescent power, although it may often be renewed by passing
electric shocks through the calcined mineral, the light that then
appears not being always of the same colour as before. Electricity
has a very manifest power of increasing the intensity of natural
phosphorescent light, and repeated electrical discharges have been
known to communicate distinct shades of colour, permanent, at
least for a time, to calcined minerals.
The diamond is remarkable for exhibiting distinct phospho-
rescence after being exposed for some time to the light of the sun.
318. ELECTRICITY, including also under this head MAGNETISM, in
its reference to mineralogy, involves considerations concerning the
ELECTRICITY. 161
capacity of different minerals for the development in them, and the
transmission through them, of electric currents. It also has refer-
ence to those instances in which electric force is exerted by a mineral
in its natural condition, as in the case of the magnet.
A great many minerals are capable of having electricity deve-
loped in them by means of friction, but it appears that the kind of
electricity thus induced has no reference to the characteristics of the
minerals. Pressure even betwixt the fingers will excite distinct
positive electricity in pieces of doubly refracting Calc-spar. Topaz,
Arragonite, Fluor-spar, Carbonate of lead, Quartz, and other mine-
rals, show the same property, but in a much smaller degree. Heat,
or change of temperature, excites electricity in the following mine-
rals, Axinite, Prehnite, Boracite, Tourmaline, Calamine, Topaz,
Sphene, Calc-spar, Beryl, Heavy-spar, Fluor-spar, Diamond, Garnet,
and others.*
With regard to the power of minerals to conduct electricity many
experiments have been made, and many results recorded, but no
important general law seems to have been obtained bearing on
the classification of minerals. It would seem that generally native
metals are the best conductors, next the sulphurets, and then the
oxides. Lustrous metallic crystals are said to be generally good
conductors, and unmetallic crystals generally bad. Crystals often
conduct differently in opposite directions, but some individual crys-
tals would seem to be almost perfect non-cOnductors.
Many minerals exhibit electric polarity by the simple application
of heat. This is the case most strikingly with tourmaline.
The following remarks, by M. Becquerel, concerning the development of electricity
in the Tourmalin, are of some interest :
"At 30 Cent., electric polarity was sensible ; it continued unchanged to 1 50 Cent.,
as long as the temperature continued to rise, but if stationary for an instant the polarity
disappeared, and shortly manifested itself reversed, when the temperature began to
decline. If only one end was heated the crystal was unpolarized, and when two
sides were unequally heated each acquired an electrical state independently of the
other."
319. Iron, Cobalt, Nickel, Iridium, and some other metals, are all
attractable by the magnet in certain mineralogical states ; and some
other minerals are so after exposure to great heat. The ordinary and
manifest phenomena of polarity and attraction are confined, however,
to a few ores, chiefly of iron. (See note p. 18.^
320. ODOUR is not possessed by any minerals in a dry unchanged
state ; but it may be obtained from several by moistening with the
breath, by friction, by heat, or by the application of acid. Amongst
the most remarkable varieties are the following :
Argillaceous, the odour of moistened clay, obtained from Serpentine, Chlorite and
some allied minerals, by breathing upon them.
* Nicol's " Mineralopry," p. "2.
162 MINERALOGY.
Fetid, the odour of sulphuretted hydrogen, obtained from some varieties of Quartz
and Limestone, by friction or a blow with the hammer.
Sulphurous, odour obtained by friction from Pyrites, and by heat, from most of the
sulphurets.
Horse-radish odour, perceived when the ores of Selenium are heated.
Garlic-odour, obtained by friction from some, and by heat from most, of the arse-
nical salts and ores.
321. The TASTE is a means of distinguishing many of the soluble
minerals the tastes of the salts of soda, of alum, of vitriol, &c., being
well known and easily recognised. Many decomposed minerals,
although they have no sensible taste, adhere more or less strongly to
the tongue, and thus affect that organ.
The tastes of minerals are thus described :
1. Astringent, having the taste of vitriol.
2. Sweetish-astringent, taste of alum.
3. Saline, taste of common salt.
4. Alkaline, taste of soda.
5. Cooling, taste of saltpetre.
6. Bitter, taste of epsom salts.
7. Sour, taste of sulphuric acid.
322. HARDNESS is a very important and distinctive character of
minerals ; but as it is of necessity a purely relative distinction, an
acknowledged scale must be obtained, composed of well known mi-
nerals, of which each preceding one is scratched by that which follows
it, while the latter does not scratch the former ; and care must be
taken that the intervals are as equal as possible, and not so small as
to render the employment difficult and uncertain, or so considerable
as to give no definite conclusion.
The following is the scale that has been selected as possessing these properties:
1. Talc.
2. Gypsum Rock-salt.
3. Calc-spar (any cleavable variety).
4. Fluor-spar (any cleavable variety).
5. Asparagus-stone (from Salzburg, possessing a conchoidal fracture) or Apatite
(transparent crystals).
6. Felspar (cleavable variety).
7. Quartz (limpid and transparent).
8. Topaz (any transparent crystal).
9. Corundum or Sapphire (the cleavable variety called Corundum stone).
10. Diamond.
Specimens of all these can be readily obtained with the exception of No. 5 ; but it
has been found impossible to discover a substitute, and there is, also, too much differ-
ence between this and felspar (6). Foliated mica has been added between 2 and 3,
and numbered 2*5, and a crystalline variety of Scapolite between 5 and 6 as 5'5.
323. The best use of the scale may be thus illustrated. The mine-
rals of the scale having been selected pure, with natural cleavage faces,
and having solid angles of the same form and edges in good condition,
and the student, being provided with a fine, very hard, and well-tem-
pered file, should try with a corner of the given mineral to scratch
the members of the scale, beginning with the hardest. Having reached
SPECIFIC GRAVITY. 163
the first that is distinctly scratched, he must have recourse to the file,
and compare upon it with a very light touch the hardness of this
degree, of the next higher degree, and of the given mineral. Care
must be taken to employ specimens of each nearly agreeing in form
and size, and also as much as possible in the quality of the angles.
From the resistance opposed to the file, and the noise occasioned by
their passing over it, we argue with perfect security upon their mutual
relations in respect of hardness. The experiment is repeated with
any alterations thought necessary till we consider ourselves arrived
at a fair estimate, which is at last expressed by the number of that
degree with which it has been found to agree most nearly, decimals
being likewise added if required.
It must be mentioned, that those minerals which cleave readily in
only one direction, often show a less degree of hardness on the perfect
face of cleavage than in other directions. Such minerals can be only
properly determined, in respect of hardness, by attending to this
peculiarity.*
"^ 324. SPECIFIC GRAVITY. The relative weight of bodies is expressed
in common language by saying that one is heavier than another,
meaning that if the two substances have the same form and dimen-
sions, there is a greater pressure downwards in the one case than the
other. Thus a cubic inch of lead weighs much more than a cubic
inch of wood ; but as both would displace the same quantity (one
cubic inch) of water, if placed in a vessel full of that fluid, both may
be measured against and compared with water as a standard, f The
relative weights thus obtained are called specific gravities ; and the
specific gravity of a mineral is often of very great importance in de-
termining its nature and place in the series.
325. The following methods of finding the specific gravity of solids will be found
convenient :
If the specimen is large enough to be suspended conveniently by a thread, weigh it
first in air by a fine balance, expressing the result in grains, and taking care previ-
ously to remove dust or loosely-adhering particles. Then suspend it by a horsehair
from the scale-pan (it is convenient to have a hook attached to it for this purpose),
and thus suspended, immerse it and re- weigh it in water, taking care that it is covered
on all sides by at least half an inch of water, and carefully brushing off with a feather
any bubbles of air that adhere to the surface. The results may then be noted as
follows :
Weight of substance in the air in grains
Deduct weight of ditto in water
Difference
This result gives the weight of a bulk of water equal to that of the specimen, and
* We have given this rather full account of the mode of determining hardness, which is
chiefly taken from Haidinger's translation of " Mohs' Mineralogy," believing that as an approxi-
mate method it may have great value when others are not readily available.
t Distilled water at a temperature of 60 Fahr. is the standard usually employed.
164 MINERALOGY.
by dividing the weight of the specimen in air by this number, the specific gravity is
obtained.
weight of substance in air
Specific gravity = weight of equal bu]k of ^^
If, however, the substance is in the form of fine sand or very small lumps, it is
better, after weighing it carefully, to take a small dry phial furnished with a stopper,
counterpoise this phial accurately in the weight scale by shot or strips of lead, then fill
it completely with pure water, taking care that no bubbles of air are left in, and
weigh the quantity of water it contains : afterwards empty the bottle and dry it
inside.
Next fill the bottle about two-thirds full of the powder to be examined, weigh
this and record the weight. Then fill the bottle once more with water, taking care,
as before, that all bubbles are expelled and none of the powder washed out. Once
more weigh it.
We have then to make the following calculation :
Weight of powder and water in grains
Deduct weight of powder alone =
Difference (weight of water left in bottle) . . . . =
Weight of bottle full of water in grains
Weight of water left in bottle)
Difference (weight of water displaced >
by, and equal in bulk to, powder) )
. weight of powder in air
The specific gravity= weight rf water displace(L
326. The minerals of which we intend to find the specific gravity, must be per-
fectly pure, and the greatest care should be taken to remove, as much as possible,
whatever heterogeneous substances may adhere to them, or, at least, we should con-
sider and mention the probable influence of such admixture on the correctness of the
results. All the vacuities, also, or empty spaces within the specimens, should be
carefully opened ; and in order to get rid of these it will be necessary, in some cases,
to have the minerals broken down till we can no longer detect a want of continuity in
the fragments.* _ _
327. The CHEMICAL COMPOSITION of minerals must be determined
by a process of chemical analysis, which it is not the object of the
present work to describe. We shall here merely allude to the simplest
and most usual means of detecting some characters which may lead at
once to a knowledge of the mineral without complete analysis. These
means involve the use of acids and alkalis, and also the appearance
of minerals when exposed to heat under a blow-pipe, either alone or
with certain salts called fluxes. Many minerals which exhibit no
distinct crystalline form, and no sufficient external physical charac-
ters, may still be readily distinguished by very simple operations of
this kind.
328. Water alone is sometimes employed in the determination of
minerals, but its use is limited to a few soluble salts ; for although
some stony minerals, as sulphate and carbonate of lime, and even
* Bowman's " Practical Chemistry," p. 41.
CHEMICAL COMPOSITION OF MINERALS. 165
silex, are no doubt soluble to some extent in water, the proportion is
too small to afford any practical indication.
329. Acids offer a far more valuable and important test, and in
many minerals produce immediate decomposition. The acids em-
ployed are either sulphuric, muriatic (hydrochloric), or nitric, gene-
rally mixed with more or less water, and applied either at the ordinary
temperature or with heat. The points to be determined and observed
when the acid is applied, are
1. Whether the mineral is acted on and dissolved by the acid.
2. Whether if so it is dissolved with effervescence.
3. Whether the whole mineral is at length dissolved, or an earthy
or gelatinous residue obtained.
In the first case the action may be either rapid or slow, and the
resulting solution either coloured or colourless a result of consider-
able importance, since a green solution almost always arises from the
presence of copper ; a pink, or rose-coloured solution from cobalt, &c.
330. With regard to substances that dissolve with effervescence
both the kind and intensity of effervescence should be noticed.
Native copper, Copper pyrites, and other native metals, metalliferous
ores not oxides, and some in which the proportion of oxygen is
small (protoxides}, give off nitrous acid vapours when dissolved in
nitric acid, and may be at once distinguished thus, Pitch blende
is immediately distinguished from Wolfram by this experiment.
It is important to notice whether the effervescence is accompanied
by any odour, and if the gas evolved is coloured.
In many cases the effervescence takes place without colour or
odour, as happens with the carbonates, which are entirely dissolved,
their carbonic acid being liberated in the form of gas. In Carbonate
of lime the action is extremely rapid and violent ; in Dolomite very
slow, and generally it only commences a minute or two after the
substance in a state of powder has been thrown into the acid. The
degree and kind of effervescence at once distinguishes several nearly
allied and very similar minerals.
331. Many substances are only partly soluble, leaving a distinct
residuum, while others exhibit a gelatinous, transparent mass, float-
ing like a cloud in the solution. The hydrosilicates often exhibit
this property, the floating jelly being the hydrate of silica. Nephe-
line, Meionite, and other minerals (generally zeolites see 417), are
good examples. It is useful sometimes to observe the proportion and
nature of the residue, as in this way, for example, the difference
between pure and argillaceous carbonates of lime may be detected, a
point of some consequence in determining the value of limestone for
the manufacture of cement.
332. Alkalis are occasionally, though very rarely, resorted to by
the mineralogist for the determination of species ; some minerals, as
166 MINERALOGY.
horn-silver, being soluble in caustic ammonia, and caustic potash
affecting the silicious jelly obtained by the solution of the hydrosil-
icates in acid.
333. The application of HEAT is extremely important in determin-
ing minerals ; and this may be effected either by calcining or roast-
ing, to discover and drive off volatile substances ; by the application
of stronger heat to produce fusion ; and by observing the results of
fusion.
Some minerals, such as Native bismuth, Sulphuret of silver, Cryo-
lite, &c., are at once reduced to the fluid state on exposure to the
flame of a taper, or a jet of burning gas ; but this is not generally
the case, and a much higher temperature is required to obtain useful
results. The usual and most convenient means of gaining this end
is to concentrate the flame by a blow-pipe, a bent tube terminating
with a fine orifice, through which common air or some gas is forced.
In this way a blast being obtained, and the heat of a flame brought
to bear on any required object, the behaviour of the mineral may be
well and minutely observed. It is no part of the intention of the
present work to give minute instructions on a subject of this kind,
and we shall, therefore, quote the brief, but distinct notice of the
use of the blow-pipe from Professor Dana's " Manual of Mineralogy,"
referring to larger and more complete treatises on blow-pipe analysis
for further information and practical results.*
334. In using the blow-pipe it is necessary to breathe and blow at the same time
that the operator may not interrupt the flame in order to take breath. Though
seemingly absurd, the necessary tact may easily be acquired. Let the student first
breathe a few times through his nostrils while .his cheeks are inflated and his mouth
closed. After this practice let him put the blow-pipe to his mouth and he will find
no difficulty in breathing as before, while the muscles of the inflated cheeks are
throwing the air they contain through the blowpipe. When the air is nearly ex-
hausted, the mouth may again be filled through the nose, without interrupting the
process of blowing.
A lamp with a large wick, so as to give a broad flame, and fed with olive oil, is
best ; but a candle is more conveniently carried about when travelling. The wick
should be bent in the direction the flame is to be blown.
The flame has the form of a cone, yellow without and blue within. The heat is
most intense just beyond the extremity of the blue flame. In some trials it is neces-
sary that the air should not be excluded from the mineral during the experiment, and
when this is the case, the outer flame is used. The outer is called the oxidating flame,
and the inner, the reducing flame.
The mineral is supported in the flame either on charcoal, or by means of steel for-
ceps with platinum extremities. The charcoal should be firm and well-burnt. Char-
coal is especially necessary when the reduction of the assay needs the presence of
carbon ; and platinum when simple heat is required. Platinum foil for enveloping
the mineral, and small platinum cups are also used- When nothing better is at hand
* One of the most important works on the subject is that of Plattner, which has been trans-
lated into English by Dr. Muspratt. The extreme beauty and accuracy of its results have
raised blow-pipe analysis into a distinct branch of chemical science, whose practical conclusions
are invaluable, and in many cases are more to be depended on than those from any other method
of assay or analysis.
ANALYSIS OF MINERALS. 167
the mineral Mica, or Cyanite may be employed. The fragment of mineral under trial
should be less than half a pea in size, and often a thin splinter is required.
To test the presence of water, or a volatile ingredient, the mineral is heated in a
glass tube or test vial. The tube may be three or four inches long, and as large as a
quill. The flame is directed against the exterior of the tube, beneath the assay, and
the volatilized substance usually condenses in the upper part of the tube. By inserting
into the upper end of the tube a strip of litmus or other test-paper, it is ascertained
whether the fumes are acid or not. The substances thus driven off are water, oxygen
gas, mercury, sulphur, arsenic, &c.
335. Some species require for fusion the aid of what are called fluxes. Those more
commonly used are borax, salt of phosphorus, and carbonate of soda. They are fused
to a clear globule, to which the mineral is added ; or powdered and made up into a
ball with the moistened mineral in powder. In this way some minerals are fused
that cannot be attacked otherwise ; and nearly all species as they melt undergo
certain changes in colour, arising from changes in composition, which are mentioned
in describing minerals.
The above-mentioned fluxes, also, are often required in order to obtain the metals
from the metallic ores. On heating a fragment of copper pyrites with borax, a globule
of copper is obtained ; and tin ore heated with soda yields a globule of tin.*
336. The composition of minerals when learned by analysis gene-
rally presents some substances which may be regarded as non-essential
to the perfect crystalline condition, and thus the true vjalue and che-
mical determination of the mineral is not at once obtained. The
application of the theory of chemical proportions will, however, gene-
rally be sufficient to show clearly what is essential and what is acci-
dental. Thus, for example Calc spar in its purest form of Iceland
spar is found to consist of
Carbonic acid 4371 1 ]00 . 00
Lime 56-29 /
and if this is reduced to show the atomic relation, we shall find that
the real proportion is two atoms of carbonic acid to one atom of lime,
which represents the true nature of the mineral. But if we take
a piece of common limestone it may give such an analysis as the
following :
Carbonic acid 35-41
Lime 45-59 j
Clay 15-40 f
Oxide of iron 3-60 J
And here at first there seems little resemblance ; but if we carry the
calculation a little further, we shall find that the 35'41 parts of car-
bonic acid in this latter analysis contain 25-58 of oxygen, while the
45-59 of lime contain 12*80 ; the proportion being still 2:1, and
the minerals, therefore, identical. The existence of impurities and
foreign substances in minerals often greatly confuses the analyses
obtained, and it requires great care to avoid error. Generally no
species can be admitted in mineralogy as well established in which
atomic relations cannot be traced very clearly, and where these do
not recur in every fair instance. In the example before us the
* Dana's " Manual of Mineralogy," ante cit. p. 68.
168 MINERALOGY.
simple relation of one atom of oxygen in the base to two atoms in
the acid establishes the species distinctly, and every instance in
which this relation exists is only a variety of the species, even if
it present peculiar physical characters.
337. The substances found in nature in a simple state have been
already indicated (see ante 8), as well as the other elementary sub-
stances hitherto determined by chemists. The elements generally are
capable of combining in definite proportions of one and one, two and
two, three and three, one and two, one and three, two and three, and
so on ; but although the whole number of possible combinations is
thus almost infinite, those really occurring in minerals are extremely
few, and comparatively speaking, are simple most of them being
binary combinations, or including only two elements in their purest
form, and even the possible number of these being greatly reduced
by two conditions.
338. One cause of the limitation of mineral species is, that only
thirteen of the elementary substances, as at present known, are essen-
tial in natural combinations. In other words, no natural combina-
tion exists without some one of these substances, and the number of
compounds is thus reduced considerably. The following are the
substances : Oxygen, Sulphur, Selenium, Chlorine, Fluorine, Carbon,
Silicium, Tellurium, Arsenic, Antimony, Gold, Osmium, Mercury.
339. The other limiting cause is the extreme simplicity of the
laws which appear to govern natural combinations of the inorganic
kingdom, a single atom of one element in combination with one or
more of another being far the most common case, and the combina-
tion of two atoms of one with three of another element being the
proportion which may be regarded as next in abundance. Occasion-
ally, no doubt, we meet with instances of greater complication, as
where three atoms of one element combine with four of another, but
such minerals are rare, and no examples more complicated than these
are at present known.
340. Frequent instances occur of what are called ' compound atoms' obeying similar
laws of combination to those just alluded to. Thus, in the case of Iceland spar already
mentioned, the mineral may be regarded as made up of two compound atoms of carbonic
acid and one of lime the compound atoms consisting in the one 'case of two atoms of
oxygen and one of carbon, and in the other of one atom of oxygen and one of carbon.
It is often convenient to be able to express the compound atoms more simply than in
the method already explained. This is done by employing Italic characters to mark
the compound, and Roman letters the simple atoms. Thus, Ca signifies Calcium, and
Co, lime. (CaO.)
Referring to the table before quoted ($ 8) we find the chemical equivalents or
atomic weights of Oxygen (0) to be 8, of Carbon (C) 6, and of Calcium (Ca) 20.
Hence, Carbonic acid is represented by (20+C = l6+6 = ) 22 ; Lime, by (Ca-f-0
=20+8:= )28 ; and Carbonate of lime by (carb. acid+lime=22-i-28=:) 50. In
many cases the proximate elements (as the carbonic acid and lime are also sometimes
called) are those which it is most essential to discover in a mineral, and for this reason
it has been thought well to allude to it here.
COMBINATION OF ELEMENTS. 169
In thus recurring once more, and for the last time, to the subject of chemical com-
bination and the laws that influence it, we would impress upon the student of geology
the absolute necessity of such preliminary acquaintance with the laws of chemistry
before attempting to learn the actual phenomena of rocks. All the important and
widely-spread masses of mineral matter that make up the solid portion of the earth's
crust are modifications of certain simple minerals combined and metamorphosed in
accordance with the laws we are here attempting to enunciate. Chemistry is in this
sense elementary to geology ; although, perhaps, the highest and most important
problems in geology can only be solved ultimately by the aid of the chemist.
341. When binary compounds, of which oxygen is one element,
are decomposed by galvanic action, the oxygen is always liberated at
the positive, and the other element (then called the base), at the
negative pole. As it is well known that electricities of the same
nature are mutually repellent, the name electro- negative is given to
those elements that proceed to the positive, and electro-positive to
those which appear at the negative pole. Oxygen is the only ele-
ment that is constantly presented at the positive pole, all others
being positive or negative according to circumstances ; sulphur and
arsenic, for example, being positive with respect to oxygen, and
negative with regard to other elements.
342. Amongst the thirteen elements, one of which is essential to
all binary combinations, two are far more abundant than the rest
namely, oxygen and sulphur ; the former being not only present, but
forming a very important proportion of the whole mass, in every one
of the rocks of which the earth's crust is made up, and the latter almost
equally important in reference to the metalliferous minerals which
form useful ores. Oxides and sulphurets are the most abundant as
well as the most widely distributed binary compounds.
343. Ternary combinations are generally composed of two binary
combinations which have a common element ; thus carbonate of lime
is of this kind ; and this, as well as most others, is formed of two
compound elements, of each of which oxygen is one, or else of two
combinations, each containing sulphur.
In this and many ways, as well as by the limitation in the number
of the atoms which combine, the total number of minerals is greatly
limited, and the number of natural groups is brought within very
easy and distinct description.
344. The most common of all minerals, and the most abundant in
quantity, are either oxides, carbonates, or sulphurets, or, in other
words, are bodies in which oxygen, carbonic acid, and sulphur are
combined with other elements or proximate elements, so as to form
binary or ternary compounds. We also find silicates presented in
nature very generally, while fluates, borates, aluminates and phos-
phates almost complete the list. The remaining minerals naturally
formed and at present known, are either modifications of those already
named, or else examples (such as chromates, tantalates, and others
where the base combined with oxygen forms an acid, which afterwards
170 MINERALOGY.
combines with some other base or binary compound), bearing a dis-
tinct relation to these, although occasionally somewhat complicated.
345. Numerous systems have been suggested and adopted by dif-
ferent authors for classifying minerals, all of them subject to many
and great inconveniences, since all separate by wide intervals sub-
stances having manifest relations, and bring together others which
have few manifest and important resemblances. Some of these are
sanctioned by names of the highest authority, but being based on
theoretical views not universally admitted they have not obtained gene-
ral assent. The plan which will be adopted in the following pages is
chiefly founded upon the chemical nomenclature of M. Dufrenoy, and
in it the number of minerals is reduced as much as seems justifiable.
In the subsequent descriptions the unimportant species are merely
named, but the names are, when necessary, accompanied by as full a
list of synonyms as is likely to be useful. The total number of species
referred to will be found to amount only to about 350, about 150 of
which are merely named. A large number are omitted as only de-
termined by the chemist, and belonging, therefore, to the domain of
chemistry rather than geological mineralogy.
The principle of classification thus adopted is essentially chemi-
cal, the crystalline form being referred to only as a useful distinctive
character in certain cases. The metals are collected together and
described in groups easily referred to ; the earthy minerals are also
arranged in a manner which seems both natural and convenient, and
the various simple salts forming ternary compounds are collected
into their principal groups. The method is no doubt partly artificial,
but it is to a great extent natural and easily understood.
346. Of other methods of classification it is not perhaps advisable
to say much. Those in which form and structure are chiefly regarded
differ in principle from the one here adopted, and are more purely
artificial. An endeavour has been made by Dufre"noy, and appa-
rently with some success, to frame a system which shall be at least
natural in the great majority of cases. Some exceptions may be
recognised, as in the case of the Silicates, since it is difficult to
exclude the Silicates of iron, copper, and other metals from Class IV.,
and almost equally difficult to include them and yet preserve the
groups of metalliferous minerals entire.
Many cases also occur in which the number of bases is so large,
and the predominant influence of any one so slight, as hardly to
justify the mineralogist in excluding the same mineral from several
groups. Isomorphism interferes occasionally by substituting one ele-
ment for another, and concealing the real nature of the chemical
constitution of several remarkable and abundant substances.
The general principles of the method adopted will be understood
by reference to the subjoined outline.
CLASSIFICATION OF MINERALS.
171
347. Table of the Classification of Minerals.
CLASS I. Simple bodies or binary compounds, never bases, generally essential
ingredients in combinations, and serving as proximate elements.
Group 1. Hydrogen. Group 4. Sulphur.
2. Carbon. ,, 5. Selenium.
3. Silicium.
CLASS II. ALKALINE SALTS.
Group 1. Salts of Ammonia. Group 3. Salts of Soda.
2. Salts of Potash.
CLASS III. ALKALINE EARTHS AND EARTHS.
Group 1. Salts of Barytes. Group 4. Salts of Magnesia.
2. Salts of Strontia.
3. Salts of Lime.
5. Salts of Yttria.
6. Salts of Alumina.
Group 1.
2.
3.
4.
5.
, 6.
7.
8.
9.
10.
11.
12.
CLASS IV. SILICATES.
Anhydrous aluminous Silicates.
Hydrous aluminous Silicates.
Silicates of Alumina and Lime or their isomorphs.
Aluminous and alkaline Silicates and their isomorphs.
Hydrous aluminous Silicates with alkaline and lime bases and
their isomorphs.
Non-aluminous Silicates.
a. with Lime as a base.
b. with Zircon as a base.
c. with several bases.
Silico-aluminates.
Silico-fluates.
Silico-borates.
Silico-titanates.
Silico-sulphurets.
Aluminates.
CLASS V. METALS.
Group 1. Cerium.
2. Manganese.
3. Iron.
4. Chromium.
5. Cobalt.
6. Nickel.
7. Zinc.
8. Tellurium.
9. Cadmium.
10. Antimony.
1 1 . Arsenic.
12. Mercury.
13. Titanium.
14. Tantalum.
J5. Niobium.
16. Petopium.
Group 17. Ilmenium.
18. Lead.
19. Tin.
20. Bismuth.
21. Uranium.
22. Tungsten.
23. Molybdenum.
24. Vanadium.
25. Copper.
26. Silver.
27. Gold.
28. Platinum.
29. Iridium.
30. Osmium.
31. Rhodium.
32. Palladium.
172
CHAPTER IX.
DESCRIPTION OF NON-METALLIC SIMPLE MINERALS.
348. WE now commence the description of minerals, and, in
order that the account may be as distinct, and at the same time as
useful as possible, we propose to mention in most cases the chemical
composition of the mineral, its hardness, its specific gravity, and the
system in which it crystallises, using sometimes certain convenient
symbols to shorten the description and avoid the constant repetition
of the same expressions. The chemical composition will be given
sometimes in full, but frequently according to the method indicated
in the first chapter (see 8), water being represented by the symbol
Aq instead of HO, and the symbols printed in italics representing the
combination of the element referred to with its full proportion of
oxygen. Hardness is indicated by the letter H, and the degree of
hardness by figures referring to the table inserted below. The specific
gravity is marked by SGI.
Tattle of Hardness.
1 = Talc 6 = Felspar.
2 = Gvpsum or Rock-salt. 7 = Quartz.
3 = Calc-spar. 8 = Topaz.
4 = Fluor-spar. 9 = Corundum.
5 = Apatite. 10 Diamond.
Table of Crystalline Systems.
1 Octahedral, or Regular. 4 Rhombic, or Prismatic.
2 Square prismatic. 5 Monoclinic.
3 Hexagonal, or Rhombohedral. 6 Triclinic.
CLASS THE FIRST.
349. The minerals included in this class are electro-negative
bodies, never appearing as bases, and always forming an essential in-
gredient in binary combinations. Some of them (Oxygen, Hydrogen,
Nitrogen, Chlorine) form permanent gases, either alone or in combi-
nation with other substances of the same group. Others, as Carbon
and Sulphur, are sometimes conveniently considered in their charac-
ter as combustibles, and others, again, will be described amongst
metals. Lastly, there are many not found, except in combinations
which must be referred to the group of Silicates. To the present class
must be referred several elementary substances not met with in nature
uncombined, but we only mention those which are important.
HYDROGEN.
HYDROGEN GAS (H), disengaged during volcanic eruptions.
SULPHURETTED HYDROGEN (HS), found in certain mineral waters.
CARBORETTED HYDROGEN (HC), marsh gas ; fire damp of coal mines.
WATER (HO or Aq.)
CAKBON. 173
CHLORINE.
HYDROCHLORIC ACID (HC1), emitted in volcanic districts.
CARBON.
350. This substance occurs in nature as a simple mineral in no
less than three distinct forms, two of them, Diamond and Graphite,
crystallizing in different systems ; and the third, though massive
and amorphous, quite unlike either of the others in many important
characters. With the exception of the two crystalline forms, the
various minerals of which carbon is a principal ingredient, burn at a
low temperature, with flame and sensible odour. They are mostly
derived from organic substances, and consist of combinations of
carbon with hydrogen, and occasionally sulphur. They are conve-
niently distinguished as resins, bitumens, and coals.
351. DIAMOND (Octahedral, C, H=10, SG=3'5 3-6). The dia-
mond is the crystalline form of pure carbon. It usually appears in
regular octahedrons, whose specific gravity is 3 '55. It burns with
a bluish flame, and is consumed at a high temperature. It is the
hardest known substance, and the one of greatest value when pure, of
good colour, and of fair dimensions. It becomes electric by friction.
Diamonds are found in various parts of the East Indies, in Brazil, in
the Ural Mountains, and in Africa, generally in a quartzose conglo-
merate. The colour of the most valuable of these gems is blue, green,
or red the latter, a rose tint, when the diamond is in other respects
good, obtaining the preference. A black variety occurs, but is very
rare. The purest of all are limpid. Diamonds are estimated accord-
ing to their weight in carats, one carat being nearly equal to four
grains troy. The largest known specimen weighed, before cutting,
nearly six ounces troy.
Besides its value as an ornament, the diamond is exceedingly
valuable for the purposes of engraving and cutting glass, and advan-
tage is taken of the frequent curvature of the crystalline faces to
produce the hardest cutting edge. The grinding and cutting of the
diamond is effected by hand, by the mutual friction of two speci-
mens, assisted by the powder of the same substance.
352. GRAPHITE (Hexagonal, C, H=0-5 1, SG=1'9 2-245) is
generally regarded as an allotropic form of carbon, which thus ap-
pears to be dimorphous. It is also called Plumbago or Black lead,
and has been regarded as a Carburet of iron, but in its pure state it
consists of 95 to 96 per cent, of pure carbon, and 2 -*- per cent, of
other matters, chiefly lime and alumina. Its specific gravity varies
a good deal, but the purest varieties are the lightest. Graphite is
crystalline either in little plates or small hexagonal spangles. It is
generally laminated or granular. In its pure state it is very valu-
able, but extremely rare. In an impure state it is common, and
174 MINERALOGY.
generally found in lumps in altered rocks. Its uses in the arts are
various the best specimens are cut into thin strips for the manu-
facture of artist's pencils. A large quantity is employed in polishing,
and in making crucibles for chemical purposes. The best specimens
are from Cumberland, but the chief supply from Mexico and Ceylon.
Coal Sub-Group.
353. ANTHRACITE (Amorphous, C, H=2 2-5, SG = 14 1-7)
has a semi-metallic lustre. It burns with difficulty. It contains
from 70 to 90 per cent, of carbon, and six to eight per cent, of
volatile substances, generally consisting of incombustible ashes, of
which Silicate of alumina forms a large part. There is a pure
vitreous variety, perfectly homogeneous, and of distinct conchoidal
fracture, but the common kinds are mixed with foreign matter. It
appears to be a third, but uncrystallized form of carbon, and is found
both in veins and beds, sometimes in altered rocks, and with metal-
liferous ores. The following is an analysis of Anthracite from
Wales : Carbon 92-56, Hydrogen 3-33, Oxygen and Nitrogen 2-53,
Ash 1-58.
354. BITUMINOUS COAL is less hard, more laminated, much richer
in volatile ingredients, and much more readily inflammable than
anthracite, containing from ten to thirty per cent, of matter chiefly
volatile. It is abundant in certain localities, and is the kind chiefly
used as fuel. The Caking coal is the kind obtained chiefly at New-
castle. Splint coal and Cherry coal are the names of varieties.
Cannel coal is compact and of even texture, with little lustre. It-
burns freely like a candle, without swelling. Jet is still harder, of
deeper colour and higher lustre. It is set in jewellery, receiving a
high polish. It contains about 37^ per cent, of volatile matter. The
principal localities of coal and other economical facts will be given
in a future Chapter.
The following analyses may be useful. They are chiefly those obtained lately
under the superintendence of Dr. Lyon Playfair :
Locality. Carbon. Hydrogen. Nitrogen. Sulphur. Oxygen. Ash.
Welch Coal. EbbwVale 8978 5-15 2-16 1-02 0'39 1'50
Ditto... Coleshill 73'84 5-14 1-47 2'34 8'29 8'92
Scotch ditto. Dalkeith 74'55 5'14 O'lO 0'33 15'51 4-37
Ditto... Grangemouth.. 79-85 5-28 1'35 1'42 8'58 3-52
English ditto Forest of Dean. 73*52 5'69 2'04 2'27 6'48 10-00
Westphalia Coal 96'02 0'44 2-94 0'60
French Coal.. Blanzy 76-48 5-23 16'01 2-28
* 355. Lignite or Brown-coal, also called Bovey-coal and Wood-coal, is much less pure
than bituminous coal, and usually contains water as well as rather a large proportion
of earthy ash. There are many varieties, and the quantity of matter given off at a
moderate heat by distillation, is at least equal to that of the carbon contained. Dyso-
dil is a yellow or greyish highly laminated substance often found with Lignite,
burning vividly and spreading an odour of asafoetida.
CARBON. 175
Bitumen /Sub-Group.
356. BITUMEN. Naphtha, Petroleum, Mineral Pitch, Asphalt, Mi-
neral oil. (CH 2 , generally fluid, SG=0-7O9). These are names
given to various forms of bitumen, consisting of compounds of carbon
and hydrogen, found both solid and fluid in nature, and presenting
no regular form. Some of them, as Petroleum, ooze from rocks of
the coal formation, and harden on exposure ; and even Naphtha,
which is a limpid or yellowish fluid, issuing from the earth in large
quantities in Persia and the Birman empire, also blackens and
hardens in the course of time. Lakes of bitumen exist in the Isle
of Trinidad, issuing at a high temperature, boiling in the middle,
but solid and cold near the shores.
The variety called Asphalt is met with abundantly on the shores
of the Dead Sea, but it also occurs in the Pyrenees, and has been
obtained from thence to mix with gravel, and form a pavement. It
has a conchoidal fracture, is sectile, H=2, SG=1'1 1-2. It is
opaque and resinous, and has a strong bituminous odour when
rubbed.
357. MINERAL CAOUTCHOUC. Elastic Bitumen, Elaterite. (CH 2 . Very soft.
SG = 0'8 1'23.) It occurs in soft, flexible masses of brownish black colour, con-
sisting when pure of 85 per cent, of carbon, and 13'3 per cent, of hydrogen. It
burns readily with yellow flame and bituminous odour. Idrialine is a variety con-
taining upwards of 94 per cent, of carbon, and represented by the formula C 3 H 2 .
Resin Sub-Group.
358. AMBER (C 10 H 8 0, H=2~2-5, SG=1-08). It occurs in
irregular transparent masses, of yellow colour and resinous lustre.
Consists of carbon 79, hydrogen 10-5, oxygen 10-5. Burns with
yellow flame and aromatic odour. It is used for ornamental pur-
poses, for pipe-heads in Turkey, and yields when burnt a carbo-
naceous residue, whence the finest black varnish is coloured. It is
highly electric by friction. It is unquestionably of organic origin,
and is chiefly found on the shores of the Baltic between Konigsberg
and Memel. It often contains the remains of insects, and sometimes
even the most delicate parts of flowers.
RKTINITE, Retin-aspfialt, occurs in roundish sub transparent masses of earthy lustre
on lignite. It is a mixture of a vegetable resin with bitumen.
Fossil Copal, a native resin found at Highgate, and elsewhere. Berengelite, Guya-
quillite, Middletonite, Piauzite, are other names for similar fossil resins.
MOUNTAIN TALLOW and HatcJietine are the names given to substances intermediate
between resins and bitumens. They have generally resulted from the decomposition
of organic substances.
Sc/ieererite, Fichtelite, Konlite, Hartite, Ixolite, Ozokerite, are the names of varieties
differing in the proportion of carbon and hydrogen. Mellite is sometimes regarded as
a resin and sometimes as a salt of alumina. See 398.
CARBONIC ACID GAS (C0 a or C). Abundant in mineral waters and
volcanic districts.
176 MINERALOGY.
BORON.
BORACIC ACID (J5-}-Aq.) found in certain mineral waters.
SILICIUM.
359. QUARTZ (Si0 3 or Si, Hexagonal, H=7, SG=2-6o 2-8).
One of the most abundant substances in nature, and one whose dif-
ferent forms are very frequently presented to the mineralogist. It
consists exclusively of silica. It strikes fire with steel, and scratches
glass and most other substances, except a few gems. It is infusible
before the blow-pipe, and insoluble in ordinary acids. The following
division into five sub-species will be found useful :
1. Rock Crystal. 4. Flint.
2. Compact Quartz. 5. Earthy Quartz.
3. Agate.
360. ROCK CRYSTAL, Amethyst, and some other varieties of Quartz, are crystalline
and highly transparent, with distinct and well-marked vitreous fractrre. The ame-
thystine varieties (Amethyst and Hose quartz) contain alumina and oxide of manganese,
and the Cairngorm or Smoky-quartz, a small quantity of bitumen. White varieties,
(Milky-quartz), are phosphorescent when rubbed together, and give out a strong odour.
Ferruginous quartz is coloured with iron, and is remarkable for often presenting well-
shaped crystals.
The general form of quartz-crystals is a regular six-sided prism, terminated by six-
sided pyramids ; but the usual crystals are modifications of this original form, although
frequently retaining a distinct trace of it. Cleavage is rarely traceable by ordinary
means, but may often be detected by heating a crystal and plunging it in water. The
tendency of cleavage is to produce the fundamental form, of which perfect specimens
are extremely rare. Quartz exhibits double refraction to a moderate degree.
Rock crystal is frequently penetrated by acicular crystals of titanium, by crystals
of asbestus, producing the mineral called Cat's-eye, and by crystals or plates of mica,
as in the case of Avanturine. The latter is a rare mineral in nature, the specimens
sold being usually factitious. A fluid has been observed occupying cavities in quartz
crystals, which was at one time supposed to be water ; but Sir David Brewster has
shown it to consist of two oleaginous liquids volatile at different temperatures. False-
topaz or Eitrine, is a name given to pale, yellow, pellucid crystals of quartz resem-
bling topaz.
COMPACT QUARTZ, or Quartzite, is the name given to metamorphic sandstones found
in the Alps and elsewhere. Granular-quartz is an earthy form of it. Sandstone passes
into granular quartz and quartzite, and will be described in a future chapter as a rock.
361. AGATE is a stalactitic or concentrically- formed quartz, frequently presenting
distinct and beautiful coloured bands. Agates are called by various names according
to their appearance, structure, or colour ; thus, when undulating and many -coloured,
they are Riband-agates; when zigzag, Fortification-agates; and when apparently
broken, Ruin- agates. When the colours and bands are not very numerous, but arranged
in flat horizontal layers, the name Onyx is given to them, and they are then employed
for cameos, one colour being partly removed in the process of manufacture. When
the colours are mixed irregularly, the specimens are called Mocha-stones or Moss-
agates^ and present the appearance of enclosed vegetation, generally due to the imper-
fect crystallisation of colouring salts of manganese or iron.
362. Agate, when of pearly or smoky grey colour, subvitreous or waxy lustre,
great translucency, and clear tint, is called Chalcedony, and specimens presenting a
blood-red colour, either uniformly distributed or in patches, are Carnelians. These
are much used in the less-expensive kinds of jewellery, and the colours are gene-
SILICEOUS MINERALS. 177
rally deepened by long exposure to the sun's rays. Sard is a deep brownish-red, and
Chrysoprase an apple -green variety, the latter coloured by nickel ; while a peculiar
dark green quartz mineral of this kind, spotted as if with drops of blood, is called
Heliotrope or Bloodstone. A faintly translucent leek-green variety, resembling jasper,
is called Plasma, It presents conch oidal fracture.
Chalcedony is not unfrequently stalactitic, and is occasionally formed in cavities.
These specimens often attain very large size. Chert seems to be a sort of granular
chalcedony and passes into the rock called ffornstone.
363. FLINT. This is a massive compact silica, of dark shades of smoky grey,
brown, or black. Its fracture is conchoidal ; it forms into masses of various gro-
tesque and irregular shapes, and is abundantly present embedded in chalk, often pre-
senting the structure of soft, spongiform, and other marine animals.
It is less transparent than any of the varieties of agate, and is connected with them
by chert, fragments being sometimes found which present both forms in a hard speci-
men. There is a variety of flint occasionally met with in a spongy or cellular form,
the cavities being themselves subsequently filled with quartz, forming a stone adapted
for grinding. This kind of mill-stone differs from the coarse granular sandstone used
generally for the same purpose in England.
Float-stone is a name given to a fibrous spongy variety of quartz so light as to float
in water. Tabular-quartz is another form, also cellular, but consisting of plates either
parallel to or crossing one another.
364. EARTHY QUARTZ. This sub-species consists of a powdery mineral, often
found on the surface of flint, or produced by infusorial ancimalules, or else deposited
by thermal springs as a siliceous incrustation on organic bodies. The well-known
polishing powder of Bilin, in Bohemia, and common Tripoli, is of this kind. Gelatinous
silex (Randanite) is a remarkable variety, and Malthacite and Micluielite are Hydrates
of silica, probably belonging to this group. Adhesive-slate, Polishing-slate, are other
varieties.
365. JASPER. The minerals to which this name is given are
merely varieties of quartz coloured by iron, of which they contain
2-75 4- per cent. They are quite opaque, often present zones or
bands like agates, admit of high polish, and are of some value.
Next to the valuable and ornamental specimens, those called Lydian
stone, Basanite, or Touchstone, are the most important, being of a vel-
vet black colour (produced by carbon), and used on account of their
hardness as a test on which to determine the purity of the precious
metals, the half- polished surface acting as a fine file, and the black-
ness of the mineral showing the colour of the metal.
366. OPAL (H=5'5 6'5, SG=2-2-2). Opal may almost be
regarded as a distinct species, presenting always a per centage of
wa{;er, which, however, varies from little more than two to more
than thirteen parts in a hundred, together with (generally) some
oxide of iron, and a small quantity of the alkaline earths. It is
compact and amorphous, and sometimes stalactitic, of very variable
colour, and often with a play of colours of great brilliancy ; of hard-
ness inferior to pure quartz, and of comparatively low specific
gravity. The following are the most remarkable varieties.
1. Precious-opal, Noble-opal, A valuable gem, the largest known specimen of
which weighs 17 ounces, and is as large as a man's fist. External colour milky, with
rich play of delicate tints.
2. Fire-opal, Girasol, Yellow with bright hyacinth or fire-red reflections.
If
178 MINERALOGY.
3. Common-opal, Semiopal, has milky opalesccnce, but no true play of colours.
4. Hydrophane. Opaque, white, or yellowish when dry, but translucent and opal-
escent when immersed in water. It is strongly adherent to the tongue.
5. Cacholong, resembles chalcedony, but contains water and also a little alumina.
6. Hyalite, Mullens-glass, Fiorite, a glassy transparent variety resembling very
transparent gum-arabic ; occurs in small concretions, stalactitic and stalagmitic.
7. Menilite, a brown opaque variety, not unfrequently slaty, found in kidney-
shaped masses at Mont Menil, near Paris.
8. Wood-opal, impure, resembling wood, and consisting of wood petrified with opal.
9. Opal-jasper, resembles jasper and contains iron.
10. Tabaslieer, a siliceous aggregation found in the joints of the bamboo.
11. Siliceous- sinter has sometimes an opaline character, and is deposited from hot
springs and near volcanoes.
SULPHUR.
367. SULPHUR (Prismatic, H=2-3, SG=l-9 2-1) occurs native
in acute octahedral crystals, and massive. Colour and streak a peculiar
and well known yellow ; lustre resinous ; very brittle ; transparent
or translucent on the edges. It is common in volcanic districts,
often in an efflorescent form, and in fine powder. Large quantities
are obtained in this way from Vesuvius, and are used in the manu-
facture of gunpowder, for bleaching, in the manufacture of sulphuric
acid, and also in medicines. It is often deposited from springs.
The trade in native sulphur is not unimportant. In 1844, about 66,000 tons
were exported from Sicily ; and in 1845, more than 40,000 tons, of which quantity
nearly one half is brought to England.
SELENIUM.
ARSENIC ( 477).
PHOSPHORUS.
368. Sulphur, Selenium, and Arsenic, have very close relations with each other, the
two former minerals especially, but the latter, as well as Tellurium and Osmium,
which likewise have chemical relations with sulphur, are more conveniently considered
as metals. Selenium and Arsenic form compounds called Seleniurets and Arseniurets.
Sulphur forms Sulphurets of various metals; these compounds being at once determined
by the odour given off when heat is applied. The odour of sulphur and also of
burning sulphur, are well-known ; that of selenium resembles horse-radish ; and
that of arsenic, garlic. Selenium is found native and also in combination with sulphur
and arsenic in SELEN-SULPHUR. Arsenic and its combinations will be described
amongst the metals. Phosphorus is chiefly known in its combinations, either directly
us in Phosphurets, or in the form of phosphoric acid, in the phosphates of various
metals and other bases. ..
The following elements belong in strictness to the present class,
but are more conveniently considered under the class of metals. A
reference is given to the paragraph where they are described.
TITANIUM ( 482). TELLURIUM ( 473). CHROMIUM ( 461).
TANTALUM ( 483). MERCURY ( 480). OSMIUM ( 514).
VANADIUM ( 495). MOLYBDENUM ( 494). RHODIUM ( 515).
ANTIMONY ( 475.) TUNGSTEN ( 493).
ALKALINE SALTS. 179
CLASS THE SECOND.
ALKALINE SALTS.
The minerals belonging to this class are soluble in water, and
have a distinct taste.
Salts of Ammonia.
369. SAL AMMONIAC, Sal volatile, Salmiac, Hartshorn, Muriate of
ammonia, (Octahedral, H=1'5 2, SG= 1-528.) Found crusted and
efflorescent, and sometimes crystalline, the usual form being a regu-
lar octahedron. Occurs in many volcanic districts, and about ignited
coal seams ; soon decomposes, and is volatile at a low temperature ;
colour white, yellowish, or grey ; soluble in three parts of water. Used
in medicine, in dyeing, by tin workers in soldering, and mixed with
iron filings, or turnings, to pack joints in stearn apparatus. Obtained
artificially.
MASCAGNINK, Sulphate of ammonia with water. (H =22-5, SG = 1*7 1'8.)
GUANITE, Phosphate of ammonia and magnesia.
STRUVITE, Phosphate of ammonia and magnesia, with water. This mineral and
the preceding are only doubtfully referred to the mineral kingdom.
Salts of Potash.
370. NITRE, Saltpetre, Nitrate of potash, (Rhombohedral. Isomor-
phous with Arragonite, H=z2, SG 1'93.) In white subtransparent
crusts and acicular crystals ; colour, white ; translucent. Soluble in
three parts of cold, or two parts of hot water. Is widely distributed
especially in Spain and Egypt, and is abundant, being derived from
the decomposition of various rocks. Used in the manufacture of
gunpowder and fireworks, and of nitric and sulphuric acids, in medi-
cine, and in glass-working.
SULPHATE OF POTASH.
SYLVINE, Chloride of potash ( SG = 1'9 2). This and the preceding salt have
been found native.
ALUM, a double salt of alumina and potash, is described among the salts of alumina
( 398).
Salts of Soda.
371. ROCK SALT, Chloride of sodium, (Octahedral, NaCl, H=2, SG
=2'257.) Occurs in cubes and derived forms, also in masses more or
less laminated, and associated with gypsum, and in fibrous masses.
It is a chloride of sodium, generally with some impurities. It is
soluble in nearly three times its weight of water and decrepitates
on charcoal. Colour of crystals when pure, white, greyish, rose-red,
yellow, and amethystine. Sometimes massive.
Very abundant in certain districts : it occurs in thick beds and
masses in the New red sandstone of Cheshire in England, at Cardova
180 MINEEALOGY.
in Spain, Wieliczka in Poland, Halle in the Tyrol, Bex in Swit-
zerland, and in various places in Hungary.
NITRATINE, Nitrate of soda (Hexagonal, isomorphous with Dolomite. H~]-5 2,
SG~2'1 2'2). Abundant in South America. Used in the manufacture of aqua-
fortis.
NATRON, Carbonate of soda (Monoclinic, H 1 1'5, SG^l'4 1'5). Used in
manufacture of soap, in smelting silver, in dyeing and bleaching, and for medicine.
TRONA, f/roo, Hydrous sesqui-carbonate of soda (Monoclinic, H 2*5 3, SG
2-12-2).
GAV-LUSSITE, Hydrous bi-carbonate of soda and lime (Monoclinic, H=2'5, SGr=
1-91-95).
GLAUBER-SALTS, Bloedite, Hussite, Hydrous sulphate of soda (Monoclinic, H
1-5 2, SG = 1'4 1-5). Used in medicine.
THENARDITE, Anhydrous sulphate of soda.
GLAUBERITE, Bronynartine^Polyhalite^ Sulphate of soda and lime.
MARTINSITE, Chloride of sodium and sulphate of magnesia.
372. BORAX, Tincal, Hydrous borate of soda (Monoclinic, H=
2 2-5, SG=1'716). In white transparent crystals with glassy
lustre. Taste, sweetish alkaline; swells, and becomes opaque white
before the blowpipe, and fuses. Is soluble in twelve times its weight
of cold, and six times its weight of hot water. Formerly obtained
chiefly from Thibet, but now from Tuscany. Used as a flux in
various metallurgical operations, in soldering, and in the manufacture
of imitative gems.
CLASS THE THIRD.
ALKALINE EARTHS AND EARTHS.
373. All the minerals of this class are stony; when pure they
are colourless, or milk-white. Usually (with the exception of
Corundum) not hard enough to scratch glass. Specific gravity, ex-
cept in the case of Tungstate of lime, between 2'5 and 4-6 ; gene-
rally infusible before the blowpipe.
Salts of Barytes.
374. WITHERITE, Barolite, Carbonate of Barytes, (Prismatic, H=3
3 '5, SG 4'3.) Remarkable for its high specific gravity; occurs
generally in six-sided prisms, or modified rhombic prisms, very im-
perfectly cleavable ; and also in globular and botryoidal masses,
showing prismatic structure. Brittle. Decrepitates before the blow-
pipe, fusing easily to a transparent globule, which becomes opaque
on cooling. Effervesces in nitric acid. It is chiefly abundant at
Alston Moor in Cumberland, and Anglezark in Lancashire, and
also in Styria. It is used to obtain the salts of barytes, much used
in chemical analysis, and also in pyrotechny, and in the manufacture
of colour for artists ; it is poisonous. Sulphato-carbonate of barytes
is a variety of this mineral containing sulphate of barytes.
SALTS OF STRONTIA AND LIMB. 181
BARYTO-CALCITE, Bromlite, Carbonate of lime and barytes.
375. HEAVY-SPAR, Hepatite, Bologna spar, Sulphate of Barytes,
(Prismatic, H = 3 3'5, SG=4-3 4-7.) This mineral is presented
in various forms, viz., crystalline, fibrous, saccharoid, compact, and
earthy. Its high specific gravity distinguishes it from most mine-
rals. Some varieties are fetid when rubbed, others phosphorescent
when heated. It decrepitates before the blow-pipe, and fuses with
difficulty. It does not effervesce with acids, and exhibits no metal-
lic reactions before the blowpipe ; colour white, inclining to yellow,
grey, blue, red, or brown ; streak white. It is generally associated
with ores of metals, especially lead. It is used sometimes instead of
white lead, either openly, or in adulterating the latter mineral, but
mixed with white lead it forms the pigments called Venice white,
Hamburgh white, and Dutch white, according to the proportions.
Bologna spar is highly phosphorescent after calcination. Allomor-
phite is identical ; Cawk is a massive variety.
DREELITE. Sulphate of barytes and lime.
Salts of Strontia.
376. STRONTIANITE, Carbonate of strontia (Prismatic, H=3-5,
SG=3'6 3-8), occurs in modified rhombic prisms, with nearly
perfect cleavage ; also in fibrous and granular masses, sometimes
globular, with internal radiated structure. Colour usually light
green, white, grey, and yellowish-brown ; brittle, transparent, or
translucent ; vitreous lustre. Fuses before the blowpipe tinging
the flame red. Found with galena at Strontian, in Argyleshire,
N.B., whence the name. Used in the preparation of nitrate of
strontia, which is extensively employed in giving a red colour to
fireworks. Emmonite and Stromnite are varieties, the latter is some-
times called Barystrontianite.
377. CELESTINE, Sulphate of strontia. (Rhombohedral, H=3
3-5, SG=3-9 4.) Crystallised in modified rhombic prisms, some-
times flattened, often long and slender, with distinct cleavage. Also
massive, laminated, columnar and fibrous rarely granular. Trans-
parent or translucent ; colour blue or white ; lustre pearly or vitre-
ous. Phosphorescent when heated. Very brittle. Found abun-
dantly in Sicily with Sulphur and Gypsum, and frequently mixed
with sulphates of lime and barytes, forming Calcareo-sulphate of
strontian, Bar yto -sulphate of strontian, Calcite and Natrocalcite.
Baryto-celestine is a variety.
Salts of Lime.
378. CALC-SPAB (CaC^ Hexagonal, H=3, SG == 2-5 2-8).
This very important mineral, remarkable for the varieties of form in
which it is presented, may be best described under the following
1 82 MINERALOGY.
subdivisions, all of which have the same chemical composition when
pure, although they are greatly modified in appearance. All effer-
vesce freely with the mineral acids, and all under the blow-pipe are
reduced to quick-lime. All are easily scratched with a common knife.
Gale-spar is one of the two dimorphic forms of Carbonate of lime ;
the other form is called Arragonite, and will be described separately.
1. Crystalline carbonate of lime.
2. Fibrous ditto.
3. Saccharoid ditto.
4. Compact ditto.
5. Earthy ditto.
379. CRYSTALLINE VARIETIES. Iceland-spar includes the most perfect and dis-
tinct crystals, and these are transparent with vitreous lustre, doubly refractive in a
high degree, and generally rhombohedrons. Cole-spar, or Calcite, is a name given to
similar crystals when opaque ; they are often white or pinkish. One variety of the
fundamental rhombohedron is called Nail-head spar, and a common dodecahedron is
Dog-tooth-spar. Many other forms also occur. The vast variety of forms into
which this mineral passes, renders it difficult to describe at least, in crystallography,
but in other respects it is very easily recognised. The cleavage is perfect, and all
varieties are brittle. The crystals sometimes attain gigantic dimensions.
Argentine is a white laminated limestone containing a small portion of silica, and
Nacreous carbonate of lime, Madreporite, Schiefer or slate spar . and Aphrite,Schaum-erde,
or Earth-foam belong to the group which we are now considering. Plumlo-calcite is
a calc spar containing a certain per centage of carbonate of lead. Fontainebkau sand-
stone is an impure pseudomorphous variety of carbonate of lime.
380. FIBROUS VARIETIES. Of these, Satin-spar is the most common, and speci-
mens of it, worked by the Egyptians, are sometimes called Alabaster. The fibrous
varieties chiefly occur in veins traversing rocks of different kinds, but are also pre-
sented in the well-known Stalactites and Stalagmites^ concretions found in caverns in
limestone rocks.
381 . MARBLES. Under this head are included all the semi-transparent, semi-crys-
talline, or crystalline forms of carbonates of lime to which the name marble is applied.
The finest kinds for statuary purposes, from Carrara, are of a pure white, and from
Paros, of a waxy cream colour; others are mixed with various metallic oxides, occur-
ring in veins, and producing clouded and coloured varieties, used for various orna-
mental purposes. Giallo-antico is yellow and mixed with a small proportion of hy-
drate of iron, Kosso-antico, a deep blood-red ; Mandelato, a light red ; and Verd-
antique, a cloudy green variety mixed with serpentine. Cipolino, is a mixture of
talcose schist with white saccharoidal marble. The Black-marble of Derbyshire
presents a combination of carbonate of lime and bitumen, and like some of the other
marbles of that part of England, made up entirely of coralline or encrinital remains
or shells, belongs rather to the next group.
382. COMPACT VARIETIES. The carbonates of lime of this group are extremely
abundant in quantity, and present very great modifications. They form thick deposits
of various geological dates ; are presented in association with various proportions of
argillaceous earth, of silex, of oxide of iron, and of carbon ; are of various colours
and various degrees of hardness, and exhibit great varieties of texture. The follow-
ing are important varieties:
1. Hydraulic-limestone, the per-centage of argillaceous earth being 10 to 12 in mo-
derately good samples, 1 5 in ordinary sorts, 1 6 in good, and 20 to 30 in those which
are eminently adapted for making hydraulic cement.
2. Cement -stone. A name given to compounds where the proportion of argillaceous
earth is still greater than in the former case. Thus the stone from which Roman-
SALTS OF LIME. 183
cement is made in England contains 36 per cent, of clay and 8*60 per cent, of oxide
of iron. They are at once recognised by the argillaceous odour they emit when
breathed on. They frequently form lumps or nodules in clay. Stinkstone, or Anthra-
conite, is a bituminous variety, giving off a fetid odour when struck.
3. Oolite is a small-grained, and Pisolite a large-grained, compact stone, formed of
carbonate of lime, and consisting of concentric layers collected round a central point,
usually organic, and cemented by a calcareous cement.
4. LumacMle, or Fire-marble, is a dark brown variety having brilliant chatoyant
reflections.
5. Uncrystalline, or rather semi-crystalline marbles, of which there are many kinds,
form another group, some of uniform texture and of various colours, others veined,
others more or less fossiliferous. The Purbeck and Petworth marbles, Forest-marble,
&c., are English examples.
383. EARTHY VARIETIES. Of these there are also several. Clialkis, perhaps, the
most abundant, and consists of nearly pure carbonate of lime in a peculiar mechanical
condition. Rock-milk, or Agaric-mineral, and Mountain-meal, resemble chalk, but
are still more earthy. Calcareous tufa, and the Calcaire grassier, of Paris, are other
examples. Marl is an earthy carbonate of lime with a large per-centage (40 to 50 per
cent.) of clay. Stalactites and Stalagmites, the incrustations found in caverns, are also
sometimes earthy. A large number of limestones must be regarded as rocks rather
than simple minerals, and will be described in a future chapter.
384. ARRAGONITE, Prismatic carbonate of lime, Igloite, Flos-ferrL
(Prismatic, H = 3-54, SG=2'93.) A remarkable dimorphic
form of carbonate of lime, crystallising often in hexagonal prisms or
stellated forms, and appearing in fibrous seams and in globular
coralloid masses. Its colour is white, with tints of grey, yellow,
green, and violet. It is transparent or translucent. Found asso-
ciated with gypsum and iron ore beds. It is not employed for any
purpose in the arts.
385. DOLOMITE. Pearl-spar, Miemite, Sitter-spar, Garofian, Tha-
randite, Brown-spar, Rhomb-spar. (Hexagonal, H=3'5 4-5, SG
=2-82-95.) A compound of carbonate of magnesia with carbonate
of lime (CaGo, + MgG^ ) ; infusible before the blowpipe ; effervescing
slowly with acids ; colour generally yellowish or creamy ; lustre
pearly; brittle; translucent. It burns to lime like common limestone,
and makes a stronger cement. It is used in the manufacture of
Epsom salts. As Magnesian limestone it forms extensive and widely
spread deposits in various districts, some of them producing excellent
building material.
The Blue-limestone, or Blue Lava, of Vesuvius, is really a dolomite, and belongs
therefore to this group. Predazzite is, probably, a variety.
386. FLUOR-SPAR, Chlorophane, Fluate of lime (Octahedral, H=4,
G=3'l 3-2). Called by miners Blue John. Generally found in
tolerably perfect cubes, or compact. Transparent or translucent,
exhibiting much variety of colour, generally shades of yellow, blue,
or green. Many varieties are phosphorescent when heated. Used
for ornamental purposes, and in the manufacture of fluoric acid.
It abounds in the lead-mines of Derbyshire, Cornwall, and elsewhere.
Ratofkite is fluor-spar with sulphate of barytes.
184 MINERALOGY.
387. GYPSUM, Alabaster, Satin-spar, Selenite, Hydrous Sulphate
of lime (Monoclinic, H = l-5 2, SG=2'264-2-3o). Like carbo-
nate of lime and dolomite, this mineral, which is very abundant,
presents itself in several forms, being found crystalline or lamellar,
fibrous, saccharoid, and compact. It consists of CaS 3 -f-2 Aq. The
plates, of which laminated varieties are formed, bend in one direction,
but are brittle in another. It is eminently foliated in one direction.
It parts with its water, and is whitened on calcination, becoming,
when ground, Plaster of Paris, a substance which is well known, and
which becomes solid on admixture with a certain quantity of water.
The more remarkable varieties are Alabaster or snowy gypsum,
Fibrous or Plumose gypsum and Satin-spar, and radiated gypsum.
When crystalline, it is often quite transparent, and is generally
colourless, or lightly tinted. It shows no action with acids. Used,
as above-mentioned, in the manufacture of Plaster of Paris, and also
for various ornamental purposes, chiefly as Alabaster.
388. ANHYDRITE, Muriacite, Vulpinite, Anhydrous sulphate of
lime (Prismatic, H=3 3-5, SG=2-8-3). The name Anhydrite
is given to crystalline anhydrous sulphate of lime, and Vulpinite to a
mixture of the same salt with a little silex. The latter mineral
takes a high polish, and is used for ornamental purposes, being harder
than the other varieties. Anhydrite is generally somewhat harder
than statuary marble, and presents no whitening or exfoliation before
the blow-pipe.
389. APATITE, Phosphorite, Asparagus Stone, Moroxite (Hexago-
nal, H=5, SG=3-166 3-285). Phosphate of lime with chloride or
fluoride of calcium. Occurs generally crystalline. Soluble in nitric
acid j fusible with difficulty. Its powder is phosphorescent. Qt is
found in various districts in a granular, compact, concretionary, or
earthy form, and frequently in old rocks. It has been attempted,
but not successfully, to make use of the Phosphorite of Estremadura
(where it is very abundant) for agricultural purposes.
390. The following phosphates, arseniates, and other salts of lime,
are of little general interest.
PHARMACOLITE, Hydrous Arsenate of lime. Hcddingerite is a variety contain-
ing a larger per-centage of water, and Picropharmacolite, a supposed sub-arsenate,
containing magnesia. Both are referred, by Dufrenoy, to this species ; Roselite is,
probably, another variety.
BERZELITE, Anhydrous sub-arsenate of lime with magnesia.
ROMEINE, Antimonate of lime.
PEROWSKITE, Titanate of lime.
PYROCHLORE, Titanate of lime, uranium, cerium and iron.
SCHEELITE, White wolfram. White tungsten, Tungstate of lime.
NITRATE OP LIME.
MURIATE OF LIME.
HAYESINE, Hydrous borate of lime.
OXALATE OF LIME.
SALTS OF MAGNESIA AND ALUMINA. 185
Salts of Magnesia.
PERICLASE, Native magnesia.
BRUCITE, Hydrate of magnesia.
NEMALITE, Hydrous carbonate of magnesia.
BREUNERITE, Carbonate of magnesia.
391. MAGNESITE, or Meerschaum (H=z2 2-5, SG=0-8 1-0), is
an earthy and siliceous carbonate of magnesia, often confounded with
the true carbonate, which is much more rare. It resembles chalk,
but is harsher. It gives off water on calcination, and does not
effervesce with acids when pure.
Aphrodite, Dermatine, and Quincite, are varieties ; the first-named nearly pure,
but much heavier than magnesite (SG 2'21) ; the second contains iron and man-
ganese, and the last a large per-centage of silica. The mineral is used in the manu-
facture of pipes, and obtained chiefly from the Crimea and from near Konie, in
Natolia. The name Magnesite is sometimes given to a compact and pure carbonate,
whose specific gravity is 2'85 2*95.
BORACITK, Rliodizite, Borate of magnesia.
HYDROBORACITE, Hydrous borate of magnesia with lime.
WAGNERITE, Phosphate of magnesia.
392. EPSOM SALTS, Epsomite, Sulphate of magnesia (Prismatic,
H=2 2-5, SGr=l-7 1-8). Found occasionally in caverns and in
mineral springs. Used in medicine. Obtained artificially from
dolomite. Astrakanite and Reussin are varieties.
NITRATE OF MAGNESIA.
MURIATE OF MAGNESIA.
Salts of Yttria.
393. The following are of little importance. They contain, besides yttria, other
rare earths and metals, especially cerium, zirconium, uranium, lanthanum, tantalum,
&c. See 444.
PHOSPHATE OF YTTRIA, Xenotime, Thorite.
YTTROCERITE, Fluate of yttria, cerium, and calcium.
YTTROTANTALITE, Black, yellow, and brown varieties, consisting of compound
Tantalates of yttria and lime with uranium, and, in some cases, cerium, and lan-
thanum, combined, also, with Tungstates of iron, uranium, &c. Euxinite is identified
with the brown Yttrotantalate.
FERGUSONITE, Tantalate of yttria and zirconium.
GADOLINITE, Silicate of yttria, cerium and iron, with glucina.
Salts of Alumina.
394. CORUNDUM (Hexagonal, isomorphous with peroxide of iron
and chrome, A1 2 0.,, H=9, SG = 3-9 4-16). The minerals col-
lected together under this name, and consisting essentially of pure
crystalline alumina coloured by iron or other metallic oxides, differ
enormously in colour, appearance, and value. There are two prin-
cipal groups, one crystalline and the other granular ; each of which
requires some notice. All specimens agree in possessing extreme
hardness, inferior only to the diamond, and this gives great value to
the granular varieties, which would otherwise be worthless. The
specific gravity is high. All are infusible under the blow-pipe, and
186 MINERALOGY.
totally unchanged by acids. The different varieties that have been
analysed give from 84 to 98 per cent, of alumina, with a variable
proportion of oxide of iron and silica.
1. CRYSTALLINE VARIETIES. These are generally transparent, and coloured blue
or red ; the former most frequently ; the colour is often confined to the edges of the
crystal. The crystalline form usually six-sided prisms, but often not traceable.
The fine azure or indigo-blue varieties are called Sapphire ; the red, Oriental rul>y ; the
yellow, Oriental topaz ; the green, Oriental emerald ; and the violet, Oriental amethyst,
Of these, the ruby is the most valuable, and fine stones often exceed the diamond in
value. The best crystalline corundums are obtained from the kingdom of Ava and from
Ceylon. The largest known ruby is in the crown of Russia. Imperfect opaque lami-
nated masses exhibiting distinct cleavage are found in Ceylon and elsewhere, and
have been called Compact corundum. Corundum, is the name given, generally, to
rough, opaque, dull masses.
2. GRANULAR VARIETIES. These are better known by the name of Emery.
They are impure, and occur in boulders, or nodules, in gneissoid, mica-slate, or talcose
rock, and even in granular limestone, associated with oxide of iron. The colour is
smoke-grey or bluish-grey ; fracture imperfect. The use of this mineral is chiefly
confined to cutting and polishing gems and other very hard substances. The best
kinds are those having a blue tint ; but many substances are sold under the name of
emery which contain no corundum. Emery is cliiefly brought from Naxos, Smyrna,
and other Greek islands, and from Spain, Saxony, Greenland, and the East Indies.
395. We have next a small group of Hydrates of alumina of little
importance.
GIBBSITE, a Hydrate of alumina (^M+Aq, H=3 3'5, SG=2'4). Earthy,
greenish colour, and resembles chalcedony. Contains alumina 64'8, water 35'7.
HYDRARGYLITE, another Hydrate of alumina, probably containing two parts of
alumina to one of water (2Al-\- Aq). Claussenite is a variety.
DIASPORE, a third Hydrate of Alumina (3 JZ-j-Aq). A variety of this mineral
from Chemnitz exhibits dichroism.
396. WAVELLITE. Hydrous phosphate of alumina, probably with
fluate of alumina. (Hexagonal, H = 3'5 4, SG=2-33 2-37.)
A fibrous, pale-green, or yellowish mineral, usually in small hemi-
spheres, attached to fissures in aluminous rocks. Translucent.
Common at Barnstaple in Devonshire. Of no value. Fisckerite and
Peganite from the Ural are, perhaps, distinct, but may for the present
be included either with Wavellite or Turquoise. A supposed. Plum-
biferous phosphate of alumina has been described, and also a mineral
called Childrenite, supposed to contain phosphoric acid, alumina,
and iron.
AMBLIGONITE, Phosphate of alumina and lithia.
LAZULITE, Klaprothrine, Double phosphate of alumina and magnesia.
397. TURQUOISE. Calaite, Agaphite, Johnite. Phosphate of alu-
mina with copper and iron. (H = 6, SGr=2'62 3.) A well-
known mineral, used for ornamental purposes, having a bluish green
colour, nearly opaque, and of somewhat waxy lustre. Hardness a
little greater than Apatite. The blue colour is lost by the action of
muriatic acid. The considerable value of this amorphous gem has
induced imitations, which are now very common, but they are gene-
SILICATES. 187
rally much softer than the true mineral. Varisdte is also a phos-
phate of alumina, of a green colour.
FLUELITE, Fluoride of alumina.
CRYOLITE, Ice-stone, is a Fluoride of alumina and sodium, and Chiolite is nearly
allied.
398. We have now a small group of Sulphates of alumina of some
interest.
FEATHER-ALUM, Hydrous sulphate of alumina, common in solfataras, in mines, and
generally where argillaceous rocks are exposed to the action of decomposed sulphurets.
WEBSTEUITK, Aluminite, Hydrous sub-sulphate of alumina, found in compact reni-
form masses and beds, at Halle in Saxony, and Newhaven in Sussex. Of white
colour and earthy appearance.
ALUM STONE. Alunite. Hydrous sub-sulphate of alumina and
potash. (Hexagonal, H=3'5 4, SG=2'6-2-8.) Abundant at
Tolfa near Rome, in Hungary, and elsewhere, and much used formerly
in the manufacture of common alum, to which it very closely
approximates. Found in crystals with perfect cleavage, and also
massive. Pearly ; translucent. Alum is chiefly obtained now from
the decomposition of certain shales.
NATIVE ALUM. This is also a hydrous sub-sulphate of alumina and potash, the
proportion of water being larger than in alum-stone. Ammonia-alum, Soda-alum, Mag-
nesia-alum, Iron-alum, and Manganese-alum, are isomorphic varieties in which ammo-
nia, soda, magnesia, iron, or manganese, replace the potash. The minerals called
Davyte, Piasopkane, and Pickerinyite, are varieties of the same kind.
The three minerals, alum, alum-stone, and aluminite are often confounded. The
following analyses of them may, therefore, be useful:
Alum. Alumstone. Aluminite.
Alumina 10'8 31'8 29'8
Potass 10-1 5-8
Sulphuric acid 337 27'0 23'3
Water 45'4 337 467
100-0 98-3 99-8
MELLITE, Hydrous mellite of alumina, is a resinous substance found on bitu-
minous wood, in Thuringia, and sometimes regarded as a resin. It is probably of
organic origin, or at least derived from organic sources.
CLASS THE FOURTH.
SILICATES.
399. The minerals of this class are stony. Their specific gravity
ranges from 2 -5 to 4, rarely approaching the latter. They are gene-
rally crystalline, and rarely quite amorphous, except, indeed, in the
case of the hydro-silicates of alumina. They form two distinct
groups, the hydrous and anhydrous silicates ; the first soft, and
readily soluble in acids, the second hard, and either insoluble in
acids, or only soluble with difficulty. Few of them are of great use
in the arts, and those chiefly as ornaments and for jewellery.
188 MINERALOGY.
Anhydrous Aluminous Silicates.
400. CYANITE. Disthene, Sapparite. (Monoclinic, H=5 7, SG
= 3-56 3-7.) Silicate of alumina. It is an abundant mineral.
Usually found in long thin-bladed crystals, of light blue colour and
pearly lustre, with distinct lateral cleavage ; rather brittle, infusible,
and without a flux, only losing its colour before the blow-pipe. White
varieties are called Rhoetizite, and fibrous specimens Fibrolite. Bu-
cholzite is an analogous mineral, also fibrous. Sillimanite is a variety
occurring in rhombic prisms, with brilliant and easy cleavage.
Worthite resembles Cyanite, but contains water. (See 397.)
ANDALUSITE (Hexagonal, H= 7 7'5, SG = 3'1 3- 3). A silicate of alumina and
probably a form of Cyanite, which is in that case dimorphous. This mineral occurs in
right rhombic prisms, massive, coarse, columnar, but never fine-fibrous. Colour
flesh-red and grey ; lustre, vitreous or pearly ; tough ; translucent to opaque.
Tesselated and cruciform crystals of Andalusite are common, and present several
varieties. Steinmark is a compact variety. Both Cyanite and Andalusite often contain
iron.
STAUROLITE, CUastolite, Cross-stone, Staurotide. (Hexagonal, H:=6'75, SG=3'3
3*7.) Silicate of alumina and iron. Colour grey, reddish-brown, or dark brown.
Occurs, generally, in micaceous schists and gneiss. It is very abundant, and gene-
rally cruciform, two crystals crossing each other. (See 287.) Cliiastolite is com-
mon in some slate rocks.
Hydrous Aluminous Silicates.
401. Almost all the minerals included in this group are badly
defined and doubtful, few of them occurring crystalline or with per-
manent well marked character.
FAHLUNITE, TriJdasite, Hydrous silicate of alumina with magnesia, oxide of iron,
and oxide of manganese. Pyrargillite is a variety. The following are, also, hydrous
silicates of alumina Pholerite, Hydrobucholzite, Worthite, Gilbertite, tiosite, Groppite,
and Smelite. They are generally soft and earthy, often resembling clavs and mag-
nesian earths, from which they are, however, distinguishable by becoming milk-white
before the blow-pipe, and refusing to fuse. They are none of them of any known
use.
402. CLAY. Under this name may be included a multitude of
earthy minerals, whose base is hydrous silicate of alumina, but
which present admixtures of iron, manganese, lime, 'magnesia, potash
and soda, with free silica. The proportions of silica, alumina, and
water are variable, and thus the different varieties may be collected
into groups. They are all amorphous, and many of them very useful
in various plastic arts.
Clays proper. The clays of this group contain only from 10 to 12
per cent, of water. They resist the action of acids, and form into
a tenacious paste with water. They are much used in the fabri-
cation of china and pottery, and include several distinct varieties.
1. Kaolin or Porcelain-day, the material used in the manufacture of the finer kinds
of porcelain, and derived generally from granitic rocks, and from the decomposition of
felspar. It is of loose earthy texture, SG=2"21 to 2*26. Different localities give
SILICATES. 1 89
clay of this kind containing from 17| to 47| per cent, of silica, 15 to 44 per cent, of
alumina, 5 to 1 5 per cent, of water, a proportion varying from a mere trace to 6 per
cent, of alkaline earths, with traces of iron and manganese, and from less than one to
more than 12 per cent, of sand or free silica.
2. Plastic-clay, or Potter's-clay, used for the less valuable and costly kinds of pottery.
The varieties thus designated are far more soapy and plastic than the former, abso-
lutely infusible when pure, slightly soluble in acids, especially after moderate calcina-
tion, and parting with their water only at a red-heat. A specimen from Devonshire,
of good quality, shows the following composition : Silica 49'60, alumina 37*40, water
11-20.
Lithomarge is a variety referable to this group.
3. Brick-clay or loam, contains a little lime, varying from 5 to 6 per cent., partly
as carbonate and partly as silicate. Most clays of this kind contain iron.
4. Marl is the name given to combinations of clay with 20 25 per cent, of
carbonate of lime.
5. Ochres. These are generally mixtures of a large proportion of oxide of iron with
clay ; they are sometimes of uniform yellow or red tint, and sometimes variegated.
Plinthile is a ferruginous clay, and so, also, is Fettbole.
6. Bituminous clays, containing a variable proportion of carbon. Stourbridge
clay is of this kind, and is used in the manufacture of crucibles, and for other pur-
poses where exposure to intense heat is required.
403. Hydrated clays. These contain a much larger proportion of
water, and have in many cases distinct properties, but only one of
them has any economic value.
7. Fullers-earth, a greenish or bluish earth containing about 25 per cent, of water,
50 per cent of silica, and 20 per cent of alumina. Soft, tenacious, and falling to
pieces in water; generally of blue or green colour, SG=2'3 2'5. Fuses into a
greenish grey glass before the blow-pipe. It was formerly much used in the fulling
of cloth, and is still valuable for that purpose.
8. Halloysite, or Halloylite, a whitish opaline mineral becoming transparent in
water, like hydrophane. (SG=2' to 2'2.) Fusible before the blow-pipe, unc-
tuous and steatitic to the touch. The following minerals belong to this variety
Tuesite, Lenzinite, Cymolite, Razoumoffiskine, Mountain-soap, Aluniocalcite.
9. Allophane differs but little from Halloysite, but contains generally much more
water. It is translucent, like wax. Its colour is pale blue and streak white. H 3,
SG = 1'85 1'90. It changes colour and becomes opaque before the blow-pipe, and
tinges the flame green. Occurs reniform, massive, and sometimes earthy. Schrotte-
rite, or Opal Allopliane, is a variety.
10. Kollyrite is a Hydrous silicate of alumina, in which the proportion of silica is
extremely small. It is white and translucent. Erinite is probably a variety, or, at
least exhibits but little essential difference.
Silicates of Alumina and Lime, or their Isomorplis.
404. GARNET. (Octahedral, H=6'5 7-5, SG=3-5-4'3.) The
large and interesting group of minerals collected under this name
afford the best illustration of the theory of isomorphism. They
present great differences of specific gravity, corresponding to differ-
ences of colour, and great complication in their chemical compo-
sition, but their form remains the same, and they may all be
represented theoretically by the formula B Si + b Si, B represent-
ing bases which combine with 3 atoms of oxygen, and b other
190 MINERALOGY.
bases, combining with only one. Thus some are Al Si + Ca Si, or
Silicate of alumina and lime, or very nearly so ; but it is so com-
monly the case that instead of alumina only, there is alumina and
iron, or iron only, and the replacement is so variable, that no line
can be drawn between this mineral and a Silicate of iron and lime
(Fe Si + Ca Si), and all the apparent species, however strongly
marked, thus pass into each other. It is, however, found conve-
nient to collect the whole series into four groups, which are called
respectively Grossulare, Almandine, Melanite, and Spessartine. The
general crystalline form is the dodecahedron and its modifications ;
but massive specimens are common. The fracture is conchoidal,
and there is a tolerably distinct cleavage parallel to the faces of the
dodecahedron. The prevalent colour is red. Crystals transparent
to opaque ; lustre vitreous ; brittle. They are generally fusible
before the blow-pipe.
405. The following are the chief varieties :
GROSSULAR VARIETIES. These are silicates of alumina and lime ; the}- include
Grossularite in greenish crystals ; Essonite or Cinnanujn-stone, of light cinnamon yel-
low colour, and high lustre ; Erlan, Wilnite, Aplome, a deep brown or orange variety ;
Romanzovite, Topazolite, a yellow variety ; Colophonite, a coarse granular resinous
variety ; and Succinite, also a granular garnet.
ALMANDINE VARIETIES. Silicates of alumina and iron ; violet, red, brown,
or black colour : hard ; heavier than the former group. It includes the Almandine or
Precious garnet, the mineral commonly used in jewellery under the name of garnet ; a
magnesian garnet, in which magnesia replaces the iron ; and the Pyrope, or Bohemian
garnet, also magnesian, but where a part of the alumina is replaced by oxide of chrome.
MELANITE VARIETIES. In these, the alumina is replaced by peroxide of iron,
and they are, therefore, silicates of iron and lime. Melanite, Rothoffite, Pyreneite,
and Allocliroite, are the principal forms, the latter still referable to the garnets, though
possessing a certain quantity of free silica.
MANGANESIAN VARIETIES. Spessartine is the name given to a deep red gar-
net in which protoxide of manganese replaces the lime of the usual formula, so
that it becomes silicate of alumina and manganese. Ouwarovite is a fine emerald
coloured form in which oxide of chromium replaces the alumina. Compact garnets of
this kind have been found.
406. IDOCRASE (Square Prismatic, H=6-5, SGr=3'35 4). A
brown, green or blue, subtransparent species, generally presented in
modified square prisms, and including the minerals Vesuvian, Ege-
ran, Cyprine and Frugardite, as well as Idocrase. Protheite is a
variety, and so also is Xanthite. All are silicates of alumina and
lime with iron.
407. EPIDOTE (Monoclinic, Hzi6 7, G= 3 -32 3-5). Another
well known mineral assuming many forms, and described by several
names. There are three prominent varieties: Thallite, Zoisite,
and Manganesian Epidote, determined chiefly by crystalline struc-
ture, but partly from the difference of colour, which in the first is
fine pistachio green, in the second, greenish grey, and in the last
violet. They are represented generally by the formula 2JB Si +
SILICATES. 191
b Si, which shows their relations with garnet (see the description of
that mineral). Pistacite, Bucklandite, Thulite, Scorza, Violane, Wit-
hamite, are either synonyms or varieties of Epidote.
408. SCAPOLITE (Square Prismatic, H=5 5-5, SG=2-6 2-8).
Under this name are included Wernerite, Paranthine and Meionite,
together with Nuttalite, Ekebergite, Gabronite, Barsowite, Bergmanite,
Ottrelite, Palagonite and Scolexerose. Arktizite and Rapidolite are
also synonyms. The mineral thus designated is represented by the
formula (3AI Si + Ca Si). It is widely distributed in old crystal-
line rocks and some volcanic rocks, presenting many varieties of
form and structure. Ampkodelite is a mineral of a similar composi-
tion, except that a certain quantity of the lime is replaced by-
magnesia.
GEHLENITE, Stylnbite. Contains 35 per cent, of lime.
MARGARITE, Pearl-mica.
409. IOLITE (Prismatic, Hzr 7 -7-5, SG=2 5 2-7). A remark-
ably glassy violet-coloured mineral, transparent, and presenting di-
chroism very distinctly, whence it has been called Dichroite. It is also
called Cordierite and Water sapphire, the latter name being given
by jewellers to a variety from Ceylon, which presents different
colours in two directions. Its formula is 3 Al Si + (MgFe) 1,,.
Steinheilite is a synonym.
The following minerals, essentially silicates of alumina with another base, may be
regarded as pseudomorphous varieties of iolite. Bonsdorfite or Hydrous lolite, Es-
markite, Praseolite, or CUorophyUite, Faldunite or Triclasite, Weissite, Finite, Giesec-
frite or Oosite, Gigantolite.
410. NEPHRITE or Jade, also called Axe-stone and Ceraunite
(H=6-5 7-5, SG=z2-9 3-03). A hard, tough, and compact
stone of greenish colour, without cleavage, lustre vitreous. It is a
silicate of alumina and magnesia.
SORDAWALITE, Silicate of alumina and magnesia with phosphate of magnesia.
411. EMERALD (Hexagonal, Hzr 7-5-8, SG=2'6-2'8). Sili-
cate of alumina and glucina. This mineral is sometimes perfectly
transparent, and of a beautiful green colour, forming one of the rarest
and most precious gems ; more frequently it is semi-transparent, of
sea-green colour, and often of large size. The less coloured speci-
mens are called Beryl or Aqua-marine. Crystallises in hexagonal
prisms. Beryls are often of large size, but seldom transparent. The
name Davidstonite has been given to a supposed variety.
EUCLASE (Al 2 Si+2GSi, Monoclinic, H=7'5, SG = 3'09). Cleavage very per-
fect ; always crystalline ; very brittle ; electric by simple pressure ; colour sea-green
or blue ; highly doubly-refracting ; used sometimes as a gem, but rarely cuts well
owing to its great brittleness.
PHENACITE. Silicate of glucina.
192 MINERALOGY.
Aluminous and Alkaline Silicates and their Isomorphs.
412. Felspar group. Granites and many other unstratified rocks
contain, as an important constituent part, a laminated nacreous
mineral of white or pink colour and peculiar lustre called felspar.
Generally this mineral is composed of silica, alumina, and potash,
but this composition is by no means invariable, soda and other alka-
line bases sometimes replacing the potash, the relative proportion of
the ingredients varying, and modifications of the crystalline form
being often observable. It has become necessary, as these variations
from the original type have been studied, that the whole group of
minerals, which with quartz and mica compose granitic rocks, and
possess the external characters called felspathic, should be distinctly
understood, for they do not all belong to the same crystalline system,
and they possess important atomic differences, although their exter-
nal characters are easily confused. Several ways have been suggested
of bringing the subject into order, and the one here adopted is that
given by M. Dufrenoy in his work on Mineralogy.
413. FELSPAR, or Orthose, also called Adularia and Orthoclase (Mo-
noclinic, Hzz6, SGzr 2-39 2-58), is the original species of the whole
group, and must, therefore, be mentioned first. It is found crystal-
line, generally reddish-white, or flesh-coloured, and opaque ; some-
times, as in Amazon stone, of a fine green. Fracture eminently
lamellar. It becomes glassy white before the blow-pipe, and fuses
with difficulty at the edge into a semi-transparent glass. Compo-
sition, Silicate of alumina and potash (3AI Si 3 + K Si 3 ), but a
portion of the potash is generally replaced by soda. A mineral
named Ryacolite by G. Rose has been identified with felspar.
Laminated varieties sometimes present fine chatoyant lustre, as Moon-stone. Many
felspathic rocks present earthy varieties of this form, and others compact felspar
or Petrosilex, sometimes called Fusible hornstone, of which Adinole and Leelite are
synonyms. A silky felspathic mineral is called Necronite, and some clear and
brilliant crystals, Ice-spar.
Clink-stone or Phonolite^ is a greyish variety of true felspar, frequently occurring in
volcanic districts. Pitchstone or Retinite is a blackish, or bottle-green mineral, also vol-
canic ; and Obsidian or Volcanic-glass, of which Marekanite is a variety, is also a well-
known volcanic product. Pumice or Volcanic-ash, is a light spongy modification of
obsidian ; and Murchisonite, an interesting mineral from the New red sandstone of
Exeter, is no doubt of the same origin although it exhibits a small excess of silica.
The most interesting and most abundant forms of these and many other minerals will
be alluded to again as rocks.
414. ALBITE (Triclinic, 11=66-5, SG=2-6 2-7). In this
species the potash of felspar is exactly replaced by soda, so that its
formula is (3AI Si 3 + Na Si*\ It includes Peridine, Tetartine,
Carnatite and Cleavelandite. It is generally crystalline, but also
massive and laminated. It resembles felspar in many respects, but
is heavier. There are massive varieties, white and almost saccha-
roid, and sometimes fibrous. Some earthy Albites are also known,
SILICATES. 193
whence soda-kaolin is derived. A peculiar soda-felspar is obtained
from the Vosges and from Monte Rosa presenting some anomalies.
Loxoclase is another variety from America.
415. LABRADORITE. Labrador felspar, Opaline felspar (Tricli-
nic, H=6, SG=2-6S-2-74). A*felspar in which lime and soda
together replace the potash. It is usually in cleavable massive
forms, has nearly perfect * cleavage, and presents a series of bright
chatoyant colours, especially blue and green. It receives a high
polish, and is sometimes used in jewellery. The name Saussurite
has been given to a variety found in the Alps and called by De
Saussure, Jade. Chonikrite is probably of the same kind. Glaucolite
and Silicite are other varieties.
PETALITE, a felspathic mineral in which lithia takes the place of potash.
SPODUMENE or Triphane^ another felspathic mineral, with a yet larger proportion
of silicate of lithia in the place of silicate of potash.
OLIGOCLASE, Soda-spodumene, a mineral having the same relation to spodumene
that albite has to true felspar. It occurs in the granites of Sweden and Norway, and
also in the recent volcanic rock of Teneriffe. Lime-oligoclase has been found in
Iceland.
ANORTHITE, Biotine, Christianite, Indianite. In this mineral, a certain proportion
of magnesia, soda, and lime , replace a corresponding portion of the potash in felspar.
With this species the list of felspathic minerals terminates.
416. LEUCITE. Leucolite, Amphigene, Vesuvian garnet (Octahe-
dral, H= 5 -5 6, SG=2-4 2-5). Occurs in dull, glassy crystals,
of the form of a trapezohedron of greyish colour. It is translucent
and brittle. It is a silicate of alumina and potash, and is very
abundant in the lava of Vesuvius.
Most of the following species are complicated combinations of
various bases with silicate of alumina, and are of little general
interest. Many of them are volcanic.
SODALITE, Canorinite, Stroganowite. Silicate of alumina and soda with chloride
of soda.
NEPHELINE, Beudaniine^ Davyne, Pinguite, Elaolite y Fat-stone, Contains soda
15' potash 6* or carbonate of lime.
DIPVRE contains lime 9*6 and soda 9'4.
HUMBOLDTILITE, Melltlite, Somervillite, chiefly silicate of lime.
SARCOLITE.
LATROBITE, Diploite.
RAPHILITE.
COUZERANITK.
Aluminous Hydrated Silicates with Alkaline and Lime bases, and
their Isomorphs.
417. The group now to be considered includes a number of mine-
rals greatly resembling each other ; they are glassy, and frequently
milk white, but admit of various tints of colour. They are neither
very hard, nor very heavy. SG=1*95 to 2-7. They give off
water before the blow-pipe, and are soluble in acids.
o
194 MINERALOGY.
Many of the minerals of this group are called Zeolites, on account of their boiling
and swelling when exposed to the heat of the blow-pipe flame. The following list
contains the names of those determined by Dr. Thomson, and the more important of
them will be found described in their places. Most of them, however, must be
regarded as synonyms :
Agalmatolite Glottalite Natrolite
Analcime Gmelinite Neurolite (?)
Antrimolite Harmotome Plinthite (?)
Apophyllite Harringtonite Pyrophyllite
Brewsterite Heulandite Rhodalite
Chabasite Ittnerite Scolezite
Chalilite (?) Karpholite Steatite
Chlorite Laumontite Stellite
Cluthalite Lehuntite Stilbite
Erinite Levyne Talc
Esmarkite Mesotype Zeuxite
418. MESOTYPE (Rhombohedral, H 5 5-5, SG:=2-17 2-3).
The following minerals are comprehended under this name, Meso-
type, Natrolite, Scolezite and Mesolite. Radiolite or Brevicite, Capor-
cianite, Lehuntite, Stellite, Harringtonite, Cluthalite, Poonahlite and
Antrimolite are varieties. They are all hydrous silicates of alu-
mina and lime, or soda, and are chiefly volcanic, either recent or
ancient.
419. STILBITE (Rhombohedral, H = 3-54, SG = 2-1 2-2).
Occurs in amygdaloid ; is generally crystalline ; highly lamellar.
White, red, grey, yellow and brown. It is a hydrous silicate of
alumina and lime. Spherostilbite and Hypostilbite are closely allied.
420. HEULANDITE (Monoclinic, H=3-5 4, SG=2-1 2-2), in-
cluding Lincolnite and Aedelforsite, is composed in nearly the same
way that Stilbite is, but in somewhat different proportions. It is a
volcanic mineral. Epistilbite is probably a variety.
421. The following are all hydrous silicates of alumina with lime,
potash, soda, and other alkaline earths, and have little general
interest. In some interesting species the per centage of alumina
and other bases is given. It has not been thought necessary to men-
tion the proportion of silica, nor must the quantities mentioned be
regarded as invariable.
BREWSTERITE (contains strontiaand baryta).
FAUJASITE contains about 17 percent, alumina, with 10 per cent, lime and soda.
GISMONDINE, Zeagonite, Alrazite, contains about 26 per cent, alumina, with 14 per
cent, lime and potash.
EDINGTONITB contains alumina 28, lime 1 3.
GLOTTALITE contains alumina 16, lime 24.
LAUMONTITE, Leonhardite, contains alumina 22, lime 12.
PREHNITE, Koupholite, in six-sided prisms or massive reniform andbotryoidal, and
of compact texture ; colour light green ; found in trap and other igneous rocks ;
receives a handsome polish. (It contains alumina 23, lime 26.)
422. CHABASITE, with Gmelinite or Hydrolite, Levyne^ Lederolite, Phacdite, Acadio-
lite, Herschelite, Beatimontite, Haydenite (Rhombohedral, H=4 4'5, SG=2 2'2).
A group of minerals of rather doubtful identity, composed of nearly 50 per cent.
SILICATES. 1 95
of silica with alumina, lime, soda, potash, and water. Form of crystals generally
nearly cubical, but different in some varieties. (Alumina 20, lime 10, soda and
potash 2.)
HARMOTOME, Morvenite y Eremite, Cross-stone, a silicate of alumina and barytes.
(Alumina 16, barytes 18.)
CHRISTIANITE, Phillipsite (Lime or Potash Harmotome). (Alumina 20, lime 6,
potash 7.)
ANALCIME, Cubicite, Sarcolite. (Alumina 23, soda 14.)
ITTNERITE. (Alumina 28, lime 5, and soda 12.)
SCOULERITE, Pipestone. (Alumina 17, soda 12, with lime and magnesia.)
THOMPSONITE, Comptonite, Chalilite. (Alumina 31-6, lime and soda 17'2.)
KILLINITE.
AGALMATOLJTE, OncJtosine, Figure stone. (Alumina 33, potash 76.)
SAPONITE, Piotine, Kerolite, Soapstone (not Steatite).
RHODALITE, Pagodite.
VERMICULITE.
KARPHOLITE.
PYROSCLERITE, Kammererite.
KIRWANITE.
PYROPHYLLITE.
423. CHLORITE (Hexagonal, Hl-1-5, Gzz2-78 2-96). It is
a silicate and aluminate of magnesia and iron. Under this species
are included certain crystals formerly regarded as talc, which may
be grouped under the names Chlorite, Pennine and Ripidolite. Hexa-
gonal chlorite is generally greenish, massive, and granular, or in in-
elastic laminae, and is very widely dispersed in rocks. Pennine is
more crystalline, and Ripidolite of different crystalline form. Chlorite
schist is a rock variety. All these minerals may be detected by the
argillaceous odour given off on breathing upon them.
424. The following are all silicates in which alumina and iron
play an important part.
LEPIDOMELANE, a black and micaceous mineral containing a large per centage of
iron.
NACRITE, Granular-talc, contains potash.
WICHTINE, contains lime, magnesia, and soda.
SEYBERTITE, Clintonite, Holmite, Holmesite, Xantophyllite^ Silicate and Aluminate
of magnesia, calcium, and iron.
GEDRITE.
SISMONDITB.
BOMBITE.
Non-aluminous Silicates.
425. APOPHTLLITE (Square prismatic, Hrz4'5 5, SG=2-3
2 '4). Occurs crystalline, and in lamellar masses; very nacreous ;
cleavage very perfect ; colour, white and greyish. It is a hydrous
silicate of lime and potassa, frequently with fluorine. Tesselite is
another name for the mineral, and Oxahverite a variety. Albin is a
white variety.
TABULAR-SPAR, Wollastonite, Chelmsfordite, Bisilicate of lime.
EDELFORSITE, Trisilicate of lime.
DYSCLASITE, Okenite, Danburite, Hydrous tetra-silicate of lime.
PECTOLITE, Osmelite, Silicate of lime and soda.
196 MINERALOGY.
426. TALC, Silicate of magnesia (Rhombohedral and Monoclinic,
H = l, SG ~ 2*68 2*9). A very soft mineral of eminently pearly
lustre and unctuous feel. Colour, greenish white. Usually in foliated
masses, but sometimes crystalline, stellate or divergent, easily sepa-
rating into thin translucent plates, flexible, but not elastic. The
purest variety is foliated, others are fibrous, and others take the
place of mica in granite, producing the rock called Protogine. Lapis
ollaris or Potstone is an impure variety, also called Indurated talc or
Talcose slate.
427. STEATITE. Another silicate of magnesia nearly resembling
talc. It is presented in two states, both soft and soapy, but one
more compact than the other. French-chalk and Soapstone are varie-
ties of Steatite or synonyms. Rensselaerite is an American variety.
428. SERPENTINE, also called Ophite, includes several varieties ;
they are all hydrous silicates of magnesia with iron, manganese or
chrome, and sometimes alumina. The following are varieties :
Picrolite, Schiller asbestus or Baltimorite, Picrophyllite, Rhodochrome,
Hydrophite and Cliloropliyllite. Precious serpentine is a beautiful
and valuable marble, and when mixed with limestone constitutes
verd antique.
METAXITE, Serpentine with asbestos.
PYRALLOLITE, an amorphous and impure silicate of magnesia.
PICROSMINE, JBoltonite, Hydrous siJicate of magnesia.
429. OLIVINE, also called Peridote and Chrysolite. Silicate of
magnesia and iron. (Prismatic, H=6-5 7, SGzz3.34). The fol-
lowing are varieties : Limbilite, Chusite, Hyalosiderite, GoeJcumite,
Batrachite, Tautolite and Knebelite. An olive green mineral occur-
ring usually in lava and basalt in embedded grains translucent and
glassy cleaving readily. It is characteristic of some lavas, and is
used occasionally as a gem.
VILLARSITE, Silicate of magnesia with iron and manganese.
430. ZIECON, called also Hyacinth, Jargon, Ceylanite. Malacon is
a variety. (Square prismatic, H 7'5, SG~4 4*7). This mineral
occurs in crystals, and also granular. Colour, brownish red, and red
of clear tints ; also yellow and grey. Streak, uncoloured ; lustre,
adamantine ; fracture, conchoidal and brilliant. It is a silicate of
zirconium coloured generally with iron. Its hardness (near corun-
dum) renders it valuable for jewelling watches. It is also sometimes
set as a gem.
AESCHYNITE, Titanate of zirconia with several rare metallic bases.
POLYMIGNITE, another titanate of zirconia, &c.
POLYCRASE, Tantalate and titanate of zirconia with uranium, &c.
WOHLERITE, Silicate and tantalate of zirconia, &c.
OERSTEDITE, Silicate and titanate of zirconia, &c.
EUDYALITE, Silicate of zirconia, lime, soda, &c.
SILICATES. 197
The next mineral is only interesting as giving an earthy element (Thorium) not met
with elsewhere. It is
THORITE, Hydrous silicate of thorium.
We have next to consider a series of minerals of considerable
importance in the composition of rocks, and having several bases.
The first is the Hornblende group, including a considerable number
of varieties. The name Amphibole is given by Dufrenoy to the
principal species. The group of Augites will follow. Analyses of
hornblendic minerals will be given in a future paragraph, and the
minerals again referred to when rock masses are considered.
431. HORNBLENDE, or AMPHIBOLE (Monoclinic, H=5 6, SG=
2-9 3*4). There are two principal sub-species, Tremolite or calca-
reous amphibole, and Hornblende or ferruginous amphibole, but they
pass into each other.
Tremolite or White Amphibole, also called Grammatite, occurs generally fibrous,
of greenish colour, and nearly transparent. Actinolite is a radiated variety, but is
sometimes glassy. It occurs asbestiform or massive. Compact Tremolite is sometimes
called Jade, and is used for various ornamental purposes.
Black Amphibole or true Hornblende is much more abundant than tremolite. It is
generally in laminated masses, sometimes acicular as in StraMstein, sometimes lami-
nated, and sometimes granular as in Pargasite; or in globular masses, or compact as
Hornstone. The colour is generally dark green, but not invariably. Hornblende is
an essential ingredient of many rocks, such as syenite, trap, and hornblende-slate.
Arfvedsonite is a variety containing 30 per cent, of oxide of iron. Phyllite is another
ferruginous variety. Polylite has a smaller proportion of silica, but in other respects
resembles hornblende ; and Diastatite only presents some difference of crystalline
form. Some varieties of Asbestos belong to Amphibole, but the whole group will be
described tinder the species Pyroxene, to which it more properly belongs.
BABINGTONITE presents striking resemblances to Amphibole, and also to Tourmaline,
but has been considered a distinct species.
432. PYROXENE, or AUGITE (Monoclinic, H=5 6, SG=3'2
3*5). This is the name given to a large group of minerals, pre-
sented under various external forms, and, like Amphibole and some
others already described, offering very striking, though difficult
cases, of isomorphism and dimorphism. Many divisions of the
species have been suggested, but we retain that of Werner, advocated
also by Dufrenoy, as best adapted for our purpose. According to
this view, there are two principal groups, Diopside and Augite,
the former chiefly occurring in igneous rocks, and the latter in
modern volcanic districts. The Augites are all silicates of magnesia
and lime, combined with one or more bases, of which protoxide of iron,
and protoxide of manganese are most abundant. These bases all
replace each other. This mineral occurs crystalline and massive,
sometimes fibrous, sometimes granular, and sometimes compact.
Lustre vitreous. Brittle.
433. DIOPSIDE or White malacolite is white or pale clear green, more or less trans-
parent ; Sahlite and Baikalite are darker green ; Mussite occurs in long, flat, crystal-
line plates ; Coccolite in grains, green or white ; Lherzolite is compact ; Fassaite and
Allalite are names that have been given to other varieties ; Hedenbergite and Jeffersonite
198 MINERALOGY.
are ferruginous varieties. Hyperstliene is a highly lamellar variety, also containing
iron, but black, with metallic lustre ; it has been called Paulite. Some manganese
varieties will be described amongst the ores of manganese.
An important group of this sub-species is that which contains Asbestos, Amianthus,
Mountain-wood , Mountain-cork, and Mountain-leailier. These are some of them so
fibrous that they admit of being woven into cloth , which from its incombustibility and
the slowness with which heat passes through it is used as a defence in entering heated
or burning places. Some kinds seem to be hydrous silicates of lime, magnesia, and
iron, and might perhaps be regarded as a distinct species ; others belong to the species
Amphibole. Zeuxite is a distinct variety of diopside though resembling Amianthus.
AUGITE or Black-pyroxene, the form usually found amongst modern volcanic
rocks, appears in black or greenish-coloured crystals, and contains a good deal of lime,
as well as iron and magnesia. Basalt has been regarded as a massive form of this
variety, and will be further described when treating of rocks.
A crystalline mineral has been described under the name of Ouralite, intermediate
between amphibole and pyroxene.
434. DIALLAGE (Monoclinic, H=4-5, SG=3'2-3-5), Silicate
of lime and magnesia. This name has been applied to different
minerals. It may be considered to include Bronzite, a mineral of
greenish brown colour and metallic lustre, common in serpentine;
and Schiller-spar, a dusky green mineral, brittle, and of metallic
pearly lustre. The former abounds in magnesia, but contains very
little lime. The latter is more calcareous. Antigorite is a variety
of bronzite. Smaragdite is an emerald green mineral, also belonging
to bronzite. Gobfiardite is probably a variety of schiller-spar.
RETINALITB ; Hydrous silicate of magnesia and soda.
435. Cronstedtite or Chloromelane, of which Sideroschisolite is probably a variety, is
a silicate of iron. Hisingerite or Thraulite, Stifpnomelane, Chloropale, Herbeckite,
Pinguite, Fettbol, Verona earth, Nontronite, Anthosiderite, Polyhydrite, Chamoisite and
Xylite, are also impure silicates of the same metal. Silicates of copper, zinc, and other
metals are also known.
There are several other minerals consisting of hydrous silicates of iron and other
bases, in which iron occupies so large a part that they will be more conveniently con-
sidered among the ores of that metal. As, however, they also belong to this place,
it may be convenient to mention their names. They are Jenite (llvaite, Lievrite),
Wehrlite, Polyadelphite, Achmite, Crokidolite, and Commingtonite (See 460).
Silico-Fluates.
436. TOPAZ, Silico-fluate of alumina (Hexagonal, H=8, SG=
3*5). Crystallizes in right rhombic prisms; cleavage perfect, parallel
to the base. Colour wine-yellow, greenish, bluish, or reddish ;
streak white ; lustre vitreous. Occurs generally in old porphy-
ritic rocks in the Ural and Altai mountains, and also in Scotland.
It is found in Brazil, frequently as a pebble. Employed in jewellery,
the colour being altered by heat. Becomes electric by heat. Has two
axes of double refraction. Picnite and Pyrophysalite are varieties ;
but the former is thought to differ in its crystalline system.
CHONDRODITE, Brucite, Maclurite, Silico-fluate of magnesia.
437. MICA, Muscovy Glass. A group of minerals having extremely
perfect lamination and a marked semi-metallic lustre, more or less
SILICATES. 199
pearly. They present several examples of isomorphism in the sub-
stitution of some of the alkaline earths for others, and an instance of
dimorphism in the two varieties called uni-axal and bi-axal mica.
Mica is important as forming one of the constituents of granite, and
it is used in Siberia and elsewhere as glass, owing to its trans-
parency, toughness, and perfect cleavage. According to Hauy, it
may be divided into laminae only ^^oVtr?5 tn f an i ncn thick.
Potash mica or Bi-axal mica (Monoclinic, H=2 2-5, SG=2'65 3). Colour,
shades of white, grey, green, brown, red, violet, and black ; silver-white, greyish-
green, and black, being the most usual. This is the common kind of mica, and
generally occurs in thin foliated masses, plates, or scales, in granite and mica-schist.
The usual composition is Silica, 46'3; alumina, 36'8; potash, 9'2; peroxide of iron, 4'5;
fluoric acid, 0'7; water, 1'8.
Lithia-mica or Lepidolite occurs in crystals of purplish colour, and in masses of
aggregated scales. Lithia here replaces a portion of the alumina to the extent of from
2 to 6 per cent , and the proportion of fluoric acid is much more considerable than in
potash mica. It is monoclinic or perhaps triclinic.
Magnesia-mica or Uni-axal mica (Hexagonal, H~2'5 3, SG=2'85 2'9). In
this mineral, a certain proportion of magnesia (10 to 26 per cent, of the whole
mineral) replaces alumina, which is present only to the extent of about 15 per cent.
The proportion of potash remains nearly the same for all varieties of mica, but is gene-
rally intermediate in this variety between the proportions met with in the two former.
Biotite is another name for this mineral.
Fuclisite is a green mica containing chrome. Plumose mica is a variety in which
the scales are arranged in a feathery form. The name Rubellane has been given to a
red mica. Margarodite is a variety of common mica. Hydrous-mica contains 14
per cent, of water.
LEUCOPHANE contains 11| per cent, ofglucina.
Silico-borates.
DATHOLITE, Esmarkite, Hydrous boro-silicate of lime. (Monoclinic, H=5 5*5,
SG 2\9 3.) Found crystalline and botryoidal, in the latter case called Botryolite.
Colour, whitish; translucent. When abundant it is used in the manufacture of borax.
Haytorite^ and Hutnboldtite are varieties.
438. TOURMALINE (Rhombohedral, H = 6-5-7-5, SG=3 3-3).
Crystalline in prisms, also coarse columnar, and sometimes massive.
Brittle. Lustre vitreous to resinous. Electrically polar when heated.
Blue and green varieties exhibit dichroism. Black, or brown black
is the more common colour, but red and yellow crystals occur. The
composition of tourmalines is very varied and complicated j boracic
acid, however, is an almost invariable ingredient, and there are three
varieties, one containing a sensible proportion of lithia, another of
soda, and a third of potash. Most specimens contain a proportion of
iron or manganese oxides.
Rubellite is a red variety; Indicolite, an indigo blue; and Brazil-emerald, a green.
Tourmaline was formerly called Schorl ; but the latter name is now confined to a
sub-species.
AXINITE, Thumite, Yanolite. In violet crystals, remarkable as one of the few
representative forms of the unsymmetrical oblique prism.
200 MINERALOGY.
Silico- Titanates.
439. SPHENE, Titanite (Monoclinic, H 5' 5'5, SG=3'4 3'6). A well-known
mineral, coloured variously with greenish-grey, greyish, or reddish-green tints. It
occurs in altered rocks, and consists of silico-titanate of lime. Greenovite is a rose-
coloured sphene, containing manganese. Menaccanite is a dark variety. Pictite
is dirty yellow. The name Semeline has been given to an orange-yellow variety.
MOSANDRITE contains also cerium and lanthanum.
Sulphur-silicates.
The minerals in this group contain sulphur. They are few in
number, but one species has considerable interest.
440. LAPIS-LAZULI, Lazulite, Ultra-marine (Octahedral, H=5-5,
SG=2'38 242). Generally massive ; of a rich and brilliant azure
blue colour, supposed to be due to the presence of sulphuret of
sodium. Obtained from Persia, and near Lake Baikal in Siberia, in a
vein with white calc-spar ; also with iron pyrites. Crystallises rarely
in dodecahedrons. It is used in mosaic-work and other costly inlaid
furniture. When powdered it is manufactured into ultra-marine,
but this has lately been made artificially. Hauyne, with a nearly
allied mineral, Spwellane, also 'called Nosean, cannot with propriety
be separated.
HELVINE is remarkable for containing sulphuret of manganese as one of the bases
in the silicates of which it is composed. It is the only instance known in which a
sulphuret acts in this way.
Aluminates.
441. SPINELLE, Aluminate of magnesia (Octahedral, H=8, SG
=3*4 3-8). A common crystalline gem, resembling various pre-
cious stones, and deriving its ordinary names from those resem-
blances. The scarlet or bright red crystals are called Spinelle-
ruby, the rose-red Balas-ruby, the orange-red Rubicelle, the violet
Almandine-ruby, the green Chloro-spinelle, and the black Pleonaste.
Opaque octahedral crystals are called Ceylanite. They are of the
hardness of topaz. The colour is derived from oxides of iron,
chrome, copper, or other metals. The mineral is found in igneous
rocks, the black varieties in volcanic districts, and the lighter
colours in granite and gneiss.
AUTOMOLITE, or Cfahnite, resembles spinelle, but contains upwards of 30 per cent,
of oxide of zinc.
DYSLUITE is a similar mineral with a large per centage of iron.
CHRYSOBERYL or Cymopkane, Aluminate of glucina (Hexagonal, H=8'5, SG=
3'69 3-78), is a beautiful and valuable gem, but rarely without flaws. Colour,
bright green. H=8'5-, SG=3'69 3'78. Specimens from the Ural have been
called Alexandrite.
TURNERITE ; Aluminate of lime and magnesia.
201
CHAPTER X.
DESCRIPTION OF METALS AND METALLIFEROUS MINERALS
OR ORES.
THE minerals that remain to be described are those to which the
term metallic applies with more or less accuracy. They are collected
together into one class, and include a variety of species of great
interest and importance.
CLASS THE FIFTH.
METALS.
442. This class, as defined by Dufrenoy, includes two divisions,
very easily distinguished by their aspect.
1. The native metals, and combinations of native metals with
each other possessing a metallic lustre.
2. Combinations of metals with oxygen or with acids, not having
generally a metallic lustre, and in this respect resembling the sili-
cates in appearance. They have, however, a peculiar aspect, and a
high specific gravity, and they almost always yield a regulus or
metallic ash on trial with the blowpipe.
In the present chapter these various minerals will be grouped
under the head of the metal most important in their composition,
and, after a short notice of the metal itself, the chief ores, if any,
will be alluded to, and the names only (with the composition) of
the other minerals mentioned. All the metals will be found here,
although some are also referred to in another chapter.
CERIUM.
443. This metal has no known use, and is only found in very
small quantities, frequently with Yttrium and Fluorine. The chief
minerals in which it occurs are from Sweden, and Cerite (a silicate)
is the only one at all abundant or easily recognised. Cerium is
named from its wax-like appearance (Ceros wax). (See ante, 393.)
The metal is said to be of whitish colour, brittle, infusible except
before the oxy-hydrogen blow-pipe, and volatile when intensely
heated. It conducts electricity badly.
CARBO-CERINE, Parasite, Carbonate of cerium.
CERIUM-OCHRE, Hydrous oxide of cerium.
CRYPTOLITE, Phosphate of cerium.
MONAZITE, Edwardsite, filengite, Eremite., Phosphate of cerium, lanthanum, and
thoria.
FLUO-CERINE, Fluoride of cerium.
BASI-CERINE, Hydro-fluoride of cerium.
ORTHITE, Cerine, Allanite^ Bodenite, Pyrorthiie. Silicates of the protoxides of
^U2 MINERALOGY.
cerium, iron, and manganese, with alumina, yttria, and lime, water, and various
impurities.
CERITE, Hydrous silicate of cerium.
TSCHEWKINITE, Silicate and titanate of cerium, lanthanum, and didymium, with
oxide of iron.
MANGANESE.
444. The earthy oxides of this metal are very widely diffused
over the earth, frequently in bands of small thickness between the
oldest and secondary groups of rocks, but often in masses without
any regularity, either parallel or transverse to the stratification. The
sandstone called by foreign geologists Arkose is that in which these
masses chiefly occur. The crystalline minerals of manganese are
generally in thin veins. The metal when obtained resembles cast-
iron, is moderately ductile, but breaks with a blow of the hammer ;
is fusible with great difficulty, rapidly tarnishes and falls to powder
on exposure to damp air, decomposing water and giving off the odour
of hydrogen when breathed on. (SG=7'86.)
Manganese is not used in the arts in the metallic state, but its
oxides are employed in bleaching to a very large extent, owing to
the facility with which they part with their oxygen gas. Besides
this use, the oxides are valuable in giving violet colours to glass, and
removing brown and green tints from the same substance. The
sulphate and chloride are used in calico-printing, and the sulphate
gives a chocolate or bronze colour. Wad, one of the impure hydrous
oxides, is used also as a coarse pigment, and in glazing pottery.
The ores of manganese are generally associated with iron, often with
barytes, and sometimes with cobalt.
MANGANESE-BLENDE, Alalandine ; Sulphuret of manganese (Mn S).
ARSENICAL MANGANESE ; Arseniuret of manganese (Mn As).
HAUSMANNITE ; Sesqui-oxide of manganese.
BRA UNITE ; Protoxide of manganese.
445. PYROLTJSITE, Peroxide of Manganese (Mn0 , Hexagonal,
H=2 2-5, Sa=4-7 5). Colour blackish grey of black; gene-
rally massive, botryoidal, fibrous, earthy or compact, and often den-
dritic. This is the most common ore of manganese, and is much
worked in various parts of Germany, in Thuringia, Westphalia, Mo-
ravia, Saxony, and Bohemia j in Hungary and France ; in the United
States ; in Brazil ; in England, in Cornwall, Devonshire, and Somer-
setshire ; and in Scotland near Aberdeen. It contains very little
water, and gives off 10 to 11 per cent, of oxygen at a red heat.
MANGANITE ; Hydrous sesqui-oxide of manganese. This mineral is described by
Beudant and referred to by Dufrenoy, asAcerdese. It is much harder than Pyrolusite
(H=3'5), containing oxygen in excess, and about KTper cent, of water. The
names NewkirTcite and Varvacite, have been given to varieties. It has little value.
446. WAD, Bog manganese, also called Earthy manganese, a
peroxide of manganese, with much water (H=3, SG=2-3 3-7).
This ore is very impure, being mixed generally with oxides of iron,
IRON. 203
cobalt, copper, and various other substances. It is used in bleach-
ing, and in the manufacture of the pigment called umber, and when
mixed with linseed-oil often takes fire spontaneously. It is found
near Exeter, and in many places on the continent of Europe.
An aluminate of the peroxide of manganese occurs near Siegen on
the Rhine, and appears to be a distinct mineral.
447. PSILOMELANE (H=5 6, SG=4-1 4-2), a doubtful mi-
neral, probably a mixture of manganite of barytes or potash, with
peroxide of manganese. It is an abundant ore, generally accompa-
nying other ores of the same metal. It contains cobalt. Heterodin
and Marceline are similar ores, containing silica.
DIALLOGITE, Rhodocrolite, Carbonate of manganese. (Hexagonal, H~3'5 4'5,
SG = 3'3 3-6.)
HUREAULITE, HETEROZiTE, and TRiPHYLLiNE, or Triplite, are phosphates of
manganese and iron. Dufrenoy puts Iron apatite in the same list.
448. BI-SILICATE OF MANGANESE, Manganese-spar, Red-manga-
nese, Horn-manganese, Hydropite, Rhodonite, Photozite (Monoclinic,
H=7, SG= 3-54 3-68). A deep rose or flesh-coloured mineral,
crystalline or granular, translucent at the edges, with irregular
fracture. It is sufficiently common generally, though rare in Eng-
land, and is found both in veins and beds. It is susceptible of a
fine polish, and is used as an ornamental stone, and also in colouring
glass and glazing pottery. Troostite, or Troolite, is a variety con-
taining iron. Bustamite, Opsimose, and Dyssnite, are probably varie-
ties obtained by partial decomposition.
TRI-SILICATE OF MANGANESE is a concretionary mineral, much lighter and less
hard than the former, and very brittle. Allagite is a variety. All the silicates of
manganese are doubtful, and contain many impurities and accidental substances.
IRON.
449. We have already mentioned iron as the most abundant and
universal metal, and it is also the most useful. It is found in almost
all minerals, combined with many metals directly, and with most
indirectly, and with sulphur, silica, carbon, and other earths. The
ores from which the metal is obtained are numerous, and for the
most part easily recognised. They have a specific gravity below 8,
and generally as low as 5 : their hardness is seldom more than 6-5.
They belong to various systems of crystallization. Iron is also found
native in masses, which seem in most cases to have passed through a
portion or the whole of our atmosphere, but in this case there is
always a certain proportion of nickel (from 1 to 25 per cent.),
together with chrome, cobalt, and other metals, sulphur, magnesia,
and often some portion of other alkaline earths. Stones of this kind
are called meteorites, and they have been found in various parts of the
world. They exhibit a hardness of about 4'5 and SGp7'3-7'8.
They are magnetic, malleable, and do not rust so readily as iron
204 MINERALOGY.
The largest known specimen is estimated to weigh 30,000 pounds.
Other specimens of native iron are said to have been found, but are
certainly extremely rare.
Pure metallic iron can only be obtained with great difficulty, and
by chemical manipulation on a small scale. It is the most tenacious
of all metals and highly ductile, but cannot be beaten into very thin
leaves; a cylindrical wire, whose diameter is r ^th of an inch (2 mille-
metres), just breaking under a weight of 550 pounds (250 kilo-
grammes). It is most malleable at a temperature exceeding red
heat. Oast iron fuses at 2786 Fahr., but malleable iron requires
the highest heat of a smith's forge. Two pieces may be cemented
together by hammering ; this is called welding, and is usually aided
by the mixture of a little sand, which forms a fusible silicate at the
surface, and prevents oxidation. The iron obtained by the ordinary
processes, and used in the arts generally, contains sulphur, phos-
phorus, carbon, and titanium. Its value differs according to the pro-
portion in which some of these are present.
450. IRON PYRITES, Marcasite, Martial pyrites, Mundic. Bisul-
phuret of iron (Dimorphous, Octahedral and Hexagonal ; Fe S 2 ;
H=6 6'5, SGr=4'8 5*1). A well-known, very common mineral,
of peculiar bronze-yellow colour, frequently found crystallized in
cubes, and often radiated, or in masses of various forms. It occurs
in rocks of all ages, and often contains a little gold. It is brittle,
strikes fire with steel, and easily gives off a sulphurous odour when
exposed to heat. It is of great use in the arts (though not as an ore
of iron), since it affords a large part of the sulphate of iron and
sulphuric acid of commerce, and much sulphur and alum. It is a
mineral very much exposed to spontaneous decomposition. White
iron pyrites is a second form of the mineral crystallizing in the
hexagonal system ; it is a little paler in colour than the other
variety, and decomposes yet more readily. Crucite is a variety.
MAGNETIC PYRITES is a softer mineral, found chiefly in old rocks.
It is of a reddish colour, and probably consists of Fe S 2 + 6Fe S.
451. ARSENICAL PI RITES, Mispickel (FeS 2 +Fe As, Hexagonal,
H=5-5 6, SG=6 6'2), is a silver white or almost steel grey
mineral, generally crystalline, and occasionally used in the manufac-
ture of arsenic, but of little value. One variety contains cobalt. An
axotomous variety is considered by Dufrenoy a distinct species.
LEUCOPYRITE is the name given to an arsenical iron with very little
sulphur, and is called by Haidinger Lolingite. It appears to be an
impure arseniuret.
452. MAGNETIC IRON ORE, Octahedral iron ore, Oxidulated iron,
Magnetite, Peroxide and Protoxide of iron (Octahedral, H=5-5
6*5, SG=4'9 5-2). Colour iron black; streak black; brittle.
A very generally diffused and important ore of iron, common in the
IRON ORES. , 205
old rocks, and generally presenting, iron 71*785; oxygen 28*215;
or peroxide of iron 69 ; protoxide of iron 31 ; and often 1 or 2 per
cent, of silica, and some oxide of titanium. It is often magnetic,
and always strongly attracted by the magnet. It is usually in octa-
hedrons, but occurs also in sand, and sometimes fibrous or amorphous.
Little of this ore is found in England, but in Norway, Sweden, and
Russia nearly all the iron, for which those countries are celebrated,
is made from it. It also forms the centre of a vast mass of iron
ore in the isle of Elba, and is abundant in India, in North America,
in Mexico, and in Brazil. Large amorphous specimens exhibiting
polarity are called lodestones or native magnets. Gillingite is a
variety.
FRANKLINITE is a peroxide of iron, probably combined with man-
ganate of zinc. Dysluite and Isophane seem identical.
453. SPECULAR IRON ORE, Red haematite, Micaceous iron, Oligist,
Iron-glance. Peroxide of iron (Hexagonal, H==5*5 6*5, SG=
5*1 5*3). An ore of iron present in some of its varieties almost
everywhere. Colour generally dark steel-grey, or iron-black, and
when crystallised having splendent lustre. When pure the ore con-
tains 69*34: iron, 30*66 oxygen, and is therefore a true peroxide,
but it is generally mixed with impurities. The different varieties
have been separated into two .groups, including, 1st. the metalloid
minerals ; 2nd. the concretionary, generally known as red haematite,
and the red earthy oxides.
The first group contains the Specular iron, very abundant at Elba,
and in volcanic districts, and often presenting brilliant iridescence
with perfect metallic lustre ; the Micaceous ore, composed of flat
spangles, which separate on touching, and soil the finger; and amor-
phous Oligist, called in Brazil Itaberite or Martite.
The second group includes all the red earthy oxides of iron, from
the ochres to those having metallic lustre ; all the red haematites,
often brown, but forming a red powder, much used in burnishing,
and also in mixing with poor iron ores in England ; the compact
red oxides ; and the hydrous varieties found in grains. Red chalk,
Jaspery clay iron, are varieties, and the clay ironstones, which
supply the vast manufactures of iron in England and Scotland, are
sometimes considered to be of this kind. They are, however, partly
carbonates.
454. BROWN HJEMATITE. Under this name we include the numer-
ous hydrous oxides of iron, to which the following names have been
given : LepidokroMte, Limonite, Brown iron-stone, Goethite, Oetite,
Oolitic and Pisolitic iron ore, Turgite, Iron ochre, and others. Its
crystallization is unknown. H=5 5*5, SGr= 3*4 3-95. It is
opaque ; with a fine fibrous fracture ; brown, yellowish-brown, yellow,
brownish-yellow, or blackish-brown colour; and yellowish-brown
206 MINERALOGY.
streak. It contains, when pure, rather more than 80 per cent, of the
peroxide of iron, and from 12 to 18 per cent, of water. Under the
names Lepidokrdkite^ Goethite, and Rubin-glimmer, are included the
crystalline varieties, while the various other minerals are amorphous
or earthy. Bog iron ore is an impure variety, containing phosphorus
( 459). Goethite is considered to differ from the true Brown haema-
tites by a different proportion of water. Stilpnosiderite seems also
a variety. The Brown haematite is valuable in polishing. Yellow
ochre is a common pigment. The mineral, if it occur in sufficient
quantity, is valuable as an ore of iron.
455. SPATHIC IRON, Sparry iron, Spathose iron, Brown-spar,
Sphcerosiderite, Siderite, Clay iron stone. Carbonate of iron. (Hexa-
gonal, H=3'5 4*5, SG=3-7 3-9.) A very important ore of iron
in various places, though not used much at present, so far as the
purer and more crystalline forms are concerned. Analyses of vari-
ous specimens show that protoxide of manganese is generally present
with the iron, and magnesia is generally present with the lime,
while the per centage of protoxide of iron varies from under 37 to
nearly 64 per cent., with from 30 to 42 per cent, of carbonic acid.
There is a strong tendency in these crystalline carbonates to assume
a spherical form ; and hence the name Siderite and Sphcerosiderite,
from the starlike radiation that results.
Vast masses of the sparry carbonate occur in Styria and Carinthia,
in the duchy of Nassau, in the Pyrenees, in Bohemia, and elsewhere.
They are only partially worked.
Junkerite is a variety of this mineral. Thomaite is a carbonate of iron in rhombic
prisms. Mesitine spar, a carbonate of iron and manganese, sometimes called Rhomb
spar. Oligon spar is another variety.
456. The Clay iron stones of England, Wales, and Scotland, found
and worked in association with the coal and limestone of the carboni-
ferous period, contain from 50 to nearly 90 per cent, of carbonate of
iron, mixed with much earthy and carbonaceous matter. They are
of the first importance, owing chiefly to the almost indefinite quan-
tity present, and the circumstances under which they occur. The
total amount of iron made annually in the British islands is not
much less than two millions of tons. Similar deposits occur in the
coal formations of Belgium and Silesia.
The argillaceous or clay ironstone is of ash-grey colour, sometimes inclining to
yellowish and bluish, also brown and reddish brown. The latter is usually the effect
of exposure to weather or heat. It occurs in amorphous or flat tabular masses, also
in globular and irregularly reniform masses ; the latter are sometimes solid, sometimes
hollow, or enclose the same substance in pulverulent state. In the latter case they are
termed cetites. The fracture is even, earthy, sometimes flat conchoidal ; occasionally
the structure is slaty. It yields easily to the knife, and is meagre to the touch.
SG 3'35. It blackens and becomes very magnetic before the blow-pipe. The fol-
lowing is the analysis of a specimen from Low Moor Iron- Works, near Bradford,
Yorkshire, called Black Iron-stone, of the specific gravity of 3'035, by Mr. Richard
IRON ORES.
207
Phillips: Protoxide of iron with a trace of oxide of manganese 43*26, carbonic acid
29'30, silex and alumina 2078, carbonaceous matter 2'67, lime 1'89, moisture I'OO,
loss 1-1.*
The following analyses of Clay ironstone nodules, chiefly from South Wales, per-
formed at the Museum of Economic Geology, will be found useful.f
Name and locality of the bed.
Per centage of
Metallic iron.
Carbonate of
iron.
I
I 1
41-5
38-5
38-4
36-8
36-4
34-9
337
307
29-4
26-6
24-6
86-0
79-9
79-5
76-4
75-4
72-4
70-0
63-9
60-9
55-5
51-04
V'6
16-4
11-0
23-0
10-0
22-16
14-0
13'5
4-1
12-6
24-6
27-6
7-0
26-1
39-1
44-5
2fi-80
Black band, Beaufort Iron- Works, Pontypool. .
Maesteg Valley, No. 3, Lower black band ....
457. CHROMIC IRON, Chromite, Chromate of iron and alumina
(Octahedral, H=5'5, SG=4-4 4'5). This mineral consists of
green oxide of chromium 60, protoxide of iron 20-1, alumina 11-8,
magnesia 7 '5. Occurs in octahedral crystals or massive, in small
green fragments, attracted by the magnet. Colour iron-black and
brownish- black. Found in serpentine and crystalline limestone,
commonly in some of the Western islands of Scotland, either in
veins, nests, or disseminated, but chiefly obtained from Sweden, the
Ural, and the United States. It is much used in the preparation of
pigments, and is an important and valuable ore.
458. The following minerals are of little practical importance.
They are titanates and tantalates of iron and other bases, iron, how-
ever, being an important ingredient.
ILMENITE, Crichtonite, MoJisite, Washingtonite, Mengite, Menackanite. Titanitic iron
contains from 8 to 53 per cent, of peroxide of titanium, and from 92 to 46 per cent,
of peroxide of iron.
ISERINE, Gregorite, Gallizinite, Titaniferous sand, Nigrine, another titanate of iron
with manganese.
TANTALITE, Ferro-tantalite, Tantalate of iron and manganese, with tin.
COLUMBITE, Baierine^ Niobite. Niobate and tantalate of iron and manganese with
tin. Contains the new and rare metal Niobium.
WOLFRAM (H = 5' 5*5,SG 7'1 7*5). Tungstate of iron and manganese, lime
sometimes replacing part of the iron. This mineral, though of no value in itself, is
not without interest in its association with the ores of tin, which it interferes with so
much as sometimes to render the ore valueless. It is hard and of high specific gravity
* Phillips' " Mineralogy," 3rd edit. p. 237.
t " Memoirs of Geological Survey of Great Britain," vol. i. p. 186.
208 MINERALOGY.
(H = 5 5*5, SG=7'1 7'5) ; sometimes magnetic. Colour brownish-black, with a
reddish brown streak. It fuses before the blow-pipe to a magnetic globule studded
with crystalline points (See $ 490).
459. The phosphates of iron are numerous, and possess some
interest. The most common is that first named.
VIVJANITE, A nglarite, Mullicite. Blue phosphate of iron (Monoclinic, H =2, SG =
2'66). There are two varieties of this mineral, one crystalline and the other earthy.
The former contains Phosphoric acid 26'99, iron protoxide 42'10, water 28 50. The
latter or earthy varieties contain more iron. Phosphate of iron is often found as an
incrustation, and is sometimes used as a pigment. The earthy variety is called
Native Prussian Blue. This mineral is found in many European countries and in
various parts of America, often in an earthy friable state with what is called Bog iron-
ore. The species thus named seems indeed to be an impure earthy phosphate com-
bined with manganese and a large per-centage of water. It is earthy, friable, and
amorphous ; colour brown-yellow, blackish-brown, or grey; sometimes very abundant,
and used in the manufacture of iron, though not well fitted for that purpose, owing to
the presence of phosphorus. It is supposed to be derived from the decomposition of
other rocks. It is found rather abundantly in Scotland and England, and contains
about 66 per cent, oxide of iron.
DUFRENITE, Green phosphate of iron (Phosph. ac. 28'42 ; iron protoxide 57'60;
water 12'15).
DELVAUXINE, Brown phospate of iron (Phosph. ac. 13'60 ; iron protox. 29 ;
carb.lime 11 ; water 42-20).
KAKOXENE, Hydrous phosphate of iron and alumina.
460. The following are silicates of iron. Others have been
already described ( 424), and some, as Green-earth, or Glauconite,
hardly admit of definite description. Some are used as ores.
YENITE, Jenite, Licvrite, Ilvaite, is a silicate of iron and lime, containing upwards
of 50 per cent, of oxide of iron. Wehrlite is a variety. POLYADELPHITE is another
silicate of iron and lime, containing less iron (about 22 per cent.) and some magnesia
and alumina. ACHMITE is a silicate of iron and soda, and KROKIDOLITE is a silicate
of iron, magnesia, and soda. COMMINGTONITE is a silicate of iron, manganese, and
soda.
BERTHIERITE, Chamoisite; a silicate and aluminate of iron. This mineral, con-
taining 60 per cent, of protoxide of iron, is obtained in abundance from the green
sand of Chamoisin, in the Valais, near St. Maurice, in Switzerland, where it is
worked as an ore. It is attracted by the magnet ; and there are several varieties
furnishing three sorts of ore, the brown, blue, and grey, all oolitic and bedded.
CRONSTEDTITE. Chloromelane, is a silicate of iron, manganese, and magnesia.
SideroscMsolite is very similar ; but contains more iron.
HISINUERITE is another silicate of iron, and with it are associated the following
minerals Stilpnomelane, Ckloropale, HerbecMte, Fettbol, Verona earth, Nontronite,
Anthosiderite, Xylite.
PYROSMALITE is a silicate with 14 per cent, of muriate of iron.
461. The following are sulphates, arsenates, oxalates, and other
salts of iron.
COPPERAS, Misy, Sulphate of protoxide of iron.
NEOPLASE, Red sulphate of iron. Sulphate of the protoxide and peroxide.
COQUIMBITE, Sulphate of the peroxide with water. This is white, and the so-
called Yellow sulphate is another sulphate of the peroxide.
PHARMACOSIDERITE, Beudardite, Cube ore, Arsenate of iron.
SCORODITE, Neoctese, Symplesite. Another arsenate of iron.
ARSENIO-SIDERITE. Arsenate of iron and lime.
CHROMIUM. COBALT. 209
PITTIZITE, Iron-sinter, and Fibro-ferrite^ are sulphates, phosphates, and arsenates of
the peroxide of iron.
HUMBOLUTITE, or Oocolite, is an oxalate of iron.
CHROMIUM.
462. Chrome is a hard, brittle metal of greyish-white colour re-
sembling iron, having a high metallic lustre, and exceedingly infu-
sible. Its specific gravity is 6, but is rarely obtained in the metallic
state and has never been used as a metal. It does not oxidise readily
on exposure to the air, but combines readily with oxygen at a red
heat. Combined with oxygen it appears as oxide of chrome, and with
iron and lead it forms chromates of those metals ( 457, 488). It
occurs with iron in meteorites.
The ores of chrome are employed in the manufacture of chromate
of potash, a yellow salt largely used by calico-printers. Mixed with
a soluble salt of lead an artificial chromate of lead is produced of
deep orange red or orange yellow colour, which forms an excellent pig-
ment, used both in oil and water colours, in calico-printing and in
dyeing. The oxide of chrome gives a green colour to glass and por-
celain, and is the colouring matter of the emerald. Chromic acid
enters into the composition of the spinelle ruby, and is employed in
calico-printing from its power of discharging the vegetable and animal
colouring matters.
CHROME OCHRE, Oxide of chrome. This mineral has been found in the Shetland
Islands and in France in an earthy state the proportion of oxide of chrome varying
from 2| to 25 per cent. Wolchonskite is a name given to a variety from Perm, in
Russia. Wiloschine is another variety.
CHROMATE OF IRON has been already described ( 457).
COBALT.
463. The metal Cobalt is of reddish steel-grey colour, brittle, rather
soft, and capable of taking a high polish. SG=8'5. It alters less
than iron on exposure and is rather less fusible. It has not been found
native, and the metal is not employed in the arts, but its oxides are
very valuable, being employed in the manufacture of a blue colour,
much used under the names smalt and zaffre in the manufactures of
porcelain and pottery. They are also used as pigments, " Cobalt blue"
or " Thenard's blue" being prepared from the phosphate, and largely
used by decorative painters and sometimes as a substitute for ultra-
marine. They are also employed in colouring glass and in painting
on porcelain. The impure oxides employed in the arts are chiefly
produced from the arsenical ores and the earthy oxide. About 650
tons weight of zaffre are annually obtained from various parts of
Germany, and 200 tons of smalts from Norway. Zaffre is the impure
oxide and of an intense blue colour. When melted with three parts
210 MINERALOGY.
of sand and one of potash it forms a blue glass, and this pounded very
small is called smalts. So intense is the blue afforded by zaffre that
one grain will give a full blue to 240 grains of glass. Cobalt is gene-
rally found in nature combined with nickel and arsenic. The ores
without metallic lustre have a reddish colour ; those with metallic
lustre are tin-white or pale steel-grey.
COBALT PYRITES, Sulphuret of cobalt.
464. SMALTINE, Arsenical Cobalt, Tin-white Cobalt (CoAs 2 , Octa-
hedral, H=5'5, SG==6'4 7*3). A tin-white or steel-grey mineral,
with dark grey or iridescent tarnish. Gives off garlic fumes when
heated. The cobalt varies from 18 to 23-5 percent., and the arsenic
from 79 to 69 per cent. A variety with from 9 to 14 percent, of
cobalt is called Radiated white cobalt.
COBALTINE, Grey cobalt, another arsenical cobalt (Arsenio-sulphuret). Danaite is
a variety. Bismuth cobalt is another variety.
465. EARTHY COBALT, Peroxide of cobalt (H=1-1'5, SG=2'2
2-6). Obtained with oxide of manganese. Colour black or blue-
black. Very variable in the quantity of cobalt it yields, and at
present little used. Found in Germany, the Ural, and England,
and abundantly in Missouri and Carolina in the United States.
Horn cobalt seems a variety.
466. COBALT BLOOM, Erythrine, Peach-blossom ore, Red cobalt
ochre. Arsenate of cobalt (Monoclinic, H=2'5, SG=2'9 3). Found
with other cobalt ores, and as an incrustation. It is valuable as an
ore of cobalt. Colour peach and crimson red ; transparent. Con-
sists of oxide of cobalt 39-2, arsenic acid 37'9, water 22-9. Roselite
and Lavenduline are probably identical. Arsenite of cobalt results
from the decomposition of this and various arsenical ores.
COBALT VITRIOL, Sulphate of cobalt.
NICKEL.
467. Nickel is of brilliant white or greyish colour, ductile, more
malleable than cobalt, and capable of being rolled and drawn into
wire. SG=8*8. At low temperatures it is as magnetic as iron, but
loses this property when heated. It is rather less fusible than iron.
It is a useful and rather valuable metal, found native in meteoric
iron, and associated with arsenic in various ores, none of them very
abundant. It accompanies cobalt and silver, and sometimes copper.
It does not oxidise on exposure at ordinary temperatures. An alloy
of this metal with copper and zinc is much used as a substitute for
plate in German silver, the usual proportions being, copper 100 parts,
nickel 4, and zinc 6. The White copper of Germany is a similar
alloy. The Packfong or Tutenague of the Chinese is also nickel with
copper and zinc, but with the admixture of silver, cobalt, and iron.
The ores of nickel have a metallic lustre and pale colour.
NICKEL ORES. ZINC. 211
NICKEL PYRITKS, Capillary pyrites, Millerite, Sulphuret of nickel.
BISMUTH NICKEL, Sulphuret of nickel and bismuth.
468. COPPER NICKEL, Nickeline, Kupfer-nickel, Arsenical nickel
(Hexagonal, H=5'5, SG=7-3 7-7). Contains, Nickel 44, Arsenic
54 ; the arsenic sometimes replaced by antimony. Colour pale cop-
per-red. Brittle. Metallic lustre. Found with cobalt and silver in
veins, generally in old rocks in Saxony, Bohemia, and Styria, and
rarely in Cornwall and Scotland. Used as an ore.
WHITE NICKEL, Cloanthite, another arsenical ore, much poorer in nickel, and not
containing more than 20-28 per cent.
PLACODINE, a third ore also arsenical, with 57 per cent, nickel.
NICKEL GLANCE, a fourth, with 28 38 per cent, nickel and some sulphur.
AMOIBITE, a fifth, with 10 per cent, more nickel than the last, but 14 per cent, of
sulphur.
ANTIMONIAL NICKEL, Breitliamptite, contains Nickel, 29 33; antimony, 63 68,
and is, therefore, represented by Ni Sb.
NICKEL STILBINE, Allmanile, an antimonial sulphuret of nickel.
NICKEL GREEN, Tombazite, Arsenate of nickel, with 36 per cent, of the oxide.
EARTHY OXIDE OK NICKEL.
GREEN HYDRATE OF NICKEL.
' PIMELITE, a clay containing 15 per cent, of oxide of nickel.
ZINC.
469. Zinc is much used in the arts, generally in sheets. It melts
at rather a low temperature (773 Fahr.), and boils at a white heat.
It is so volatile as to be occasionally distilled. Its colour is bluish
white, its fracture clean and laminated, and very brilliant. SG =
6*86 7*20, varying according to its condition, as cast or beaten. It
is very easily oxidised, but the tarnish does not eat into the substance.
It is not found native, but has long been used in the manufacture of
certain metallic alloys, of which Brass is the best known. It is now,
and has always been, obtained from the carbonate and silicate, which
are very abundant in the lead districts of England (Derbyshire, Alston
Moor, Mendip Hills, &c.), in Silesia, Poland, Carinthia, in Central and
Eastern Asia, especially China, and in North America. It is malle-
able between 220 and 230 Fahr., and may then be hammered out,
rolled into sheets, and drawn into wire. At higher temperatures,
between 400 and 500 'Fahr., it is so brittle that it may be pounded
in a mortar. It is tough and intractable at common temperatures.
Wire y'oth inch diameter sustains a weight of 26 pounds. In England
the annual make is upwards of 1200 tons, and in Belgium and on
the frontier of that country, 2600 tons. In Silesia, about 2500 tons
are made every year.
Brass is made from copper and an ore of zinc (calamine). Zinc is
much used now as a cheap substitute for lead in lining cisterns, co-
vering roofs, forming water-spouts, and manufacturing many kitchen
and dairy utensils. It is also engraved on (instead of stone) for
212 MINERALOGY.
zincographic printing. The sulphate and oxide are employed in
medicine. It is used by the Chinese as a coin.
470. BLENDE, Black jack, Sulphuret of zinc (Octahedral, ZnS,
H = 3-5, SGr=4'16). Not much used as an ore, though very com-
mon. It is found abundantly with lead ores, and is sometimes
accompanied by calamine. It is often phosphorescent by friction.
Marmatite is a variety.
SELENIURET OF ZINC.
VOI.ZINE, Oxy-sulphuret of zinc.
471. CALAMINE, Carbonate of Zinc (Hexagonal, H=5, S.G =
4-1 4'5). This, is the usual ore of zinc, and the metal is obtained
from it by distillation. It is crystalline, massive, or incrusting.
Colour impure white, green, or brown. Subtransparent. Brittle.
Effervesces in nitric acid. Contains about 65 per cent, of oxide of
zinc (four-fifths of which is pure zinc), and about 35 per cent, of
carbonic acid, but is often impure, containing iron, manganese, and
cadmium. It occurs commonly with galena and blende in the Men-
dip Hills in Somersetshire, in Flintshire, Derbyshire, and elsewhere
in England, in Belgium, near Aix-la-Chapelle on the Rhine, in Car-
inthia, Silesia, Hungary, Siberia, and in the United States. Zinc
Bloom is an earthy carbonate, containing 15 per cent, of water.
Aurichalcite is a variety, also containing water. The rare metal
Cadmium is found with this ore. Pseudomorphous crystals are
common, resembling Dog-tooth spar.
472. ELECTRIC CALAMINE was long confounded with calamine. It
is, however, a true Silicate of zinc. (2Zn S + Aq, Triclinic, H =
4-55, S.G.= 3-35 3-45.) Colour whitish, bluish, greenish, or
brownish. Transparent. Brittle. Strongly electric when gently
heated, and some varieties become electric by friction. It occurs with
calamine generally in the lead mines, and sometimes contains cad-
mium. It is valuable as an ore of zinc. Mancinite is also a silicate,
and Willemite an anhydrous silicate.
HOPEITE, supposed to be a phosphate of zinc.
BRUCITE, Red oxide of zinc and manganese (Triclinic, H=4
4'5, SGr=5-4 5-56). Colour deep or bright red; streak orange-
yellow. A good ore when abundant, and one easily reduced, but it
is nearly confined to North America. Tephroite is identical.
HYDRATE OF ZINC AND COPPER.
PYRRHITE, Oxide of zinc (?)
WHITE VITKIOL, Sulphate of zinc. It is supposed to arise from the decomposition
of blende.
TELLURIUM.
473. Tellurium occurs native, and also in combination with gold,
silver, iron, lead, and bismuth. Its colour is brilliant white, like
that of tin ; it is brittle, rather less fusible than lead, and combus-
CADMIUM. ANTIMONY. 213
tible. SG=6-115. It is extremely rare, and only found in the
metallic state. It is of no use in the arts. The following are the
most usual combinations :
NATIVE TELLURIUM (Tellurium, iron, gold).
GRAPHIC TELLURIUM, Graphic Gold, Aurotellurite (Tellurium, gold, silver).
BLACK TELLURIUM (Tellurium, gold, lead, silver, sulphur).
FOLIATED TELLURIUM (Tellurium, lead, gold, copper, silver, sulphur).
BISMUTH TELLURIUM (Tellurium, bismuth, sulphur, selenium).
CARBONATE OF TELLURIUM, Herrerite., Carbonate of tellurium and nickel.
CADMIUM.
474. This metal occurs with ores of zinc chiefly in Silesia, in the
proportion of from 2 to 1 1 per cent. It is also found in England in
the form of sulphuret in the mineral called Greenockite. When re-
duced, the metal has the colour and lustre of tin, but with a shade
of grey. It takes a high polish. It resembles tin not only in colour,
but in softness, ductility, and in the peculiar creaking sound it emits
when bent and heated. It is malleable, and fusible at 442 Fahr.
SG=8-6. Its oxide and sulphuret produce fine brown and orange-
yellow colours which may be used as pigments. The sulphate has been
used in medicine. Some other uses have been suggested, of which
the most important is coating iron tubes with a mixed deposit of cop-
per and cadmium to supersede the so-called " galvanised iron," or iron
dipped in melted zinc.
GREENOCKITE (Hexagonal, CdS, H = 3 3'5, SG = 4-8 4'9).
ANTIMONY.
475. Antimony is a silver-white metal, slightly blue, and with very
brilliant lustre. Its hardness is about equal to that of gold. SG=
6-7 6*8. Compact, and brittle. It does not oxidise on exposure at
ordinary temperatures, but fuses a little below red heat and burns
vividly. It is found native but not abundantly. It occurs generally
with lead, silver, arsenic, &c., but the only important ore is the sul-
phuret. As a metal it is used in the manufacture of type metal, of
which it forms from one fourth to a twelfth part, the rest being lead,
with a little tin, bismuth, and copper. Mixed with lead alone it
forms the rather brittle plates from which music is printed. Hard
pewter is made of 12 parts tin and 1 antimony. Britannia metal of
100 parts tin, 8 antimony, 2 bismuth, and 2 copper. With iron it
forms a hard whitish alloy. A very small quantity renders gold un-
malleable. The sulphuret (crude antimony) has sometimes been used
in the East to stain the hair of an intense black. The oxides are
much used in medicine, and also in giving colour to factitious gems.
Hungary alone supplies 600 tons annually, and large quantities are
also obtained in England and France, and lately from Borneo.
NATIVE ANTIMONY, with a little silver.
STJBLITE, Antimonate of antimony.
214
MINERALOGY.
ANTIMONATE OF LEAD (Ant. 31 per cent).
ARSENICAL ANTIMONY (Antimony 37 per cent., arsenic 62).
476. GREY ANTIMONY (Sb. S 3 , Rhombic H=2, SG=4-6-4-7).
An important mineral, containing, ant. 73, sulph. 27. Colour lead-
grey. Sectile, cleaving readily. Often in long prismatic or acicular
crystals, with strong vertical strisB. Occurs in masses or veins in
the metamorphic and igneous rocks. Often compact and sometimes
capillary. It fuses rapidly in the flame of a candle. It resembles
the oxides of manganese, but is easily distinguished by its cleavage.
ZINKENITE, Sulphuret of antimony and lead (proportion of antimony 45 percent.).
PLAGIONITE do. (Ant. 38 per cent.).
FEATHER ORE, Sulph. of ant. and lead (Ant. 31 per cent.).
BOULANGERITE, Sulphuret of ant. and lead (Ant. 25J per cent.).
JAMESONITE, do. with iron and bismuth (Ant. 35 per cent.).
RED ANTIMONY, Kermes mineral, Antimony blende, Sulphuret and oxide of anti-
mony (Ant. 75 per cent.).
WHITE ANTIMONY, Oxide of antimony (Sb 2 3 ).
ANTIMONO-PHYLLITE, an impure oxide of antimony.
ANTIMONIC ACID.
ANTIMONIOUS ACID.
In addition to these are several other sulphurets of antimony and
lead, which must be regarded as ores of lead. These are Steinman-
nite, Killbrickenite, Kobellite, White silver. Geokronite and Boulange-
rite are sometimes regarded as belonging to this group.
BERTHIERITE, Haidingerite, Sulphuret of antimony and iron.
(Ant. 52 per cent.)
ARSENIC.
477. Arsenic occurs in a native state, nearly pure, and also with
many other metals, especially iron, cobalt, nickel, silver, copper, anti-
mony, and manganese. It is a bluish-white or steel-grey metal with
brilliant lustre. It is very soft (H = 3-5) but brittle, and has a gra-
nular fracture and granular or lamellar texture. Its specific gravity
is 5'7 6. At a high temperature (365) it volatilizes and is readily
inflammable, giving off a strong odour of garlic. It readily tarnishes,
becoming almost black by exposure to the air.
Arsenic combines with oxygen in White arsenic (arsenious acid)
and with sulphur in two forms, both common and valuable minerals.
It also forms arseniurets with various metals, many of which have
been described. It is used in the arts as a metal, in mixture with
lead, to manufacture shot, its effect being to make the lead break
readily in drops. It is also an ingredient in several alloys of lead,
antimony, bismuth, &c. White arsenic is used in medicine, and in
the manufacture of glass, and by candle-makers, and the sulphurets
(realgar and orpiment) are valuable pigments, used both in dyeing and
in the fine arts. Arsenic acid forms many metallic and other salts,
called Ar senates.
WHITE ARSENIC (As 2 O 3 ).
PHARMACOLITE, Arsenate of lime.
MERCURY. TITANIUM. 215
478. REALGAR, Red sulphuret of arsenic. (AsS.) Found in oblique
prisms or massive ; of a beautiful clear cochineal or orange-red
colour. Transparent. H = 1-5 - 2, SG = 3-35 - 3-65. Found
chiefly in Transylvania and Hungary, with tellurium and gold ; also
from China. Used in fireworks. Contains 70 per cent, arsenic.
479. ORPIMENT, Yellow sulphuret of arsenic (As (7 S 3 , H:=l < 5, SGr
= 3-48). Rarely crystalline. Contains 61 per cent, of arsenic. Sub-
transparent. Sectile. Obtained from Hungary, Turkey, China, South
and North America. Made use of as the basis of the pigment called
King's yellow.
MERCURY.
480. Mercury is found native in association with the sulphuret or
chloride, the only ores. It is fluid at ordinary temperatures, has a
silver-white colour and brilliant lustre. SG = 13-596. It solidifies
at 39 Fahr. and volatilises very easily. Its principal use is in the
preparation of silver and gold. The annual supply from all sources
is about 1600 tons. When solid, mercury is malleable. In its ordi-
nary state it combines very readily with some metals, as gold, silver,
and tin. It tarnishes readily on exposure.
In addition to the use of mercury in the amalgamation of the ores
of the precious metals, it is employed in gilding, in silvering mirrors,
in filling thermometer and barometer tubes, and in various philoso-
phical instruments. The salts of mercury are used in medicine.
NATIVE AMALGAM (Mercury and silver, with 6472 percent, of
mercury).
481. CINNABAR, Sulphuret of mercury (HgS, H=2-5, SG =
8-098) ; contains 86'29 per cent, of mercury. The principal ore of
mercury. Colour bright red to brownish red ; streak red. Found
crystalline in tabular or six-sided prisms, and massive. Sectile ; nearly
opaque. It occurs with talcose and argillaceous slate, or with por-
phyries, in rocks of various ages, and is volatile, and easily reduced.
The principal mines in Europe are in Idria, Almaden, and the Pala-
tinate (on the Rhine near Bingen) ; it is found in Peru, Chili, and
Mexico ; and lately very abundantly in California. It is used as a
pigment, under the name vermilion, but chiefly in the preparation
of the metal by distillation.
HORN QUICKSILVER (Chloride of mercury), is a tough sectile ore found in the
Almaden and Ober Moschel (Rhine) mines.
SELENIDE OF MERCURY.
lODIC MERCURY.
TITANIUM.
482. Titanium, although a metal, and occurring sometimes native,
has more analogies with silica than with the metallic minerals gene-
rally. It occurs chiefly in nature in combination with oxygen, form-
ing titanates of various earths and metals, and is very universally
diffused with quartz and iron.
216 MINERALOGY.
When obtained artificially as a metal or in the slags of iron-works,
(where it is found not unfrequently in the form of brilliant cubic
crystals*), titanium is found to be of copper-red colour, very brittle,
hard enough to scratch quartz and steel, very light (SG=5'3), and
infusible at all ordinary temperatures, not being affected by the high-
est heat of the blast furnace. In a crystallised state it is not acted
on by acids, but when powdered is less refractory. Titanium is at
present little used for any practical purpose, but an attempt was once
made to employ it as a pigment.
RUTILE, Nigrine, Titanic acid, a reddish-brown mineral, found in altered rocks,
and used to a small extent in painting on porcelain, and in enamelling artificial teeth.
ANATASE, another variety of Titanic acid.
BROOKITE, a third variety.
WARWICKITE, Fluoride of titanium and iron.
SPHENE is a silico-titanate, and is mentioned with some other salts of this metal in
a former paragraph ( 439).
MENACCANITE, Titaniferous iron.
483. TANTALUM or COLUMBIUM, NIOBIUM, PELOPIUM, and ILMENIUM,
are other metals which may be mentioned here, but of which too little
is known to admit of further reference. They are none of them at
all employed in the arts.
TANTALUM or COLUMBIUM combines with oxygen, forming an acid
whence are produced several compounds called tantalates. (SG=G.)
It appears hard, and is infusible before the smith's forge, though
fusible by the aid of the oxy-hydrogen blow-pipe.
LEAD.
484. Lead is a metal of great importance in the arts. It is found
native, but only very rarely, being usually in combination with silver,
antimony, arsenic, selenium, sulphur, molybdenum, chrome, and vari-
ous acids. The only important ore is the sulphuret. Lead when
pure is of bluish grey colour, tarnishing black. H=1'5, SGr=
11-3 11 '4. It is ductile and malleable, but the least tenacious of
all metals. Its texture is close like that of gold or silver. It is
inelastic and one of the least sonorous of the metals. It melts at 612
Fahr., soils the fingers when rubbed, and marks paper. It emits a
peculiar odour when rubbed in the hand. It is apparently soluble
to some extent in perfectly pure water, and as the solution is poi-
sonous cannot safely be used for culinary purposes. Lead oxidises
readily on exposure, but not deeply, assuming a dull earthy aspect.
It may be considered as the most abundant and most widely diffused
metal after iron ; about 55,000 tons are annually produced from the
British mines only.
Metallic lead is much used in the arts in various ways : in thick
sheets for roofing, lining cisterns, &c., and also in much thinner
sheets for smaller works ; it is cast into pipes for conducting water,
* These crystals are now regarded as cyanide and nitruret of titanium.
LEAD ORES. 217
gas, &c. ; alloyed with tin to make solder, and in the manufacture of
pewter ; and with antimony and tin in type metal ; alloyed wi 4 th
arsenic it forms shot ; combined with oxygen it forms massicot and
litharge, both protoxides, and the latter of them used in the manu-
facture of flint glass and in separating silver from lead ores ; it forms
also red lead, a deutoxide used in the manufacture of flint glass and
as a pigment ; the carbonate or white lead is a well-known paint, and
the chromate a yellow pigment ; the acetate, sugar of lead, is used
in various ways in medicine and the arts.
4:85. GALENA, Lead glance, Sulphuret of lead, almost always con-
taining silver. (PbS, H=2'6, SG=7'57.) This very important
mineral occurs in cubical crystals, in coarse or fine granular masses,
or fibrous. When pure the proportion of lead is 86 per cent., and
there is generally some silver, varying indefinitely in amount, but, if
present in no larger a proportion than 1 part to 10,000 (3 ounces to
the ton), the silver can be separated with advantage in reducing the
ore. Galena has a brilliant metallic lustre and lead-grey colour, and
is brittle. The principal localities for this mineral in England are
Durham and Northumberland, Cumberland, Yorkshire, Shropshire,
and Cornwall ; Cardiganshire and Flintshire, in Wales, Ireland,
Scotland, and the Isle of Man also yield a considerable quantity.
It occurs in Saxony, the Hartz, Spain, and France, in various places ;
in Belgium, near Namur ; in Bohemia ; in Siberia and in many
places in Asia ; and in North America in the Missouri district, in
vast abundance. It is usually in veins. Cuproplumbite is a galena
with 24 1 per cent, of sulphuret of copper.
The following names have been given to minerals in which sul-
phuret of lead is the principal ingredient, but in which antimony,
bismuth, iron, copper, or other substances, replace a portion of the
lead. In the opinion of M. Dufrenoy, these are not sufficiently defi-
nite to be regarded as species.
Steinmannite, Sulphuret of lead and antimony, proportions unknown.
KMricfonite, Sulphuret of lead and antimony, with arsenic, and iron, or copper
(lead 68-87, iron 0-38, antimony 14'39).
Kobellite (Antimony 9"24, lead 40' 12, bismuth 33'3, iron 2'96, copper 0'80).
Weissgultigerz (rather an ore of silver than lead, containing iu one specimen 20
per cent, of silver, and 48 of lead).
GEOKRONITE, Antimono-arseniuret of lead, Pb 5 (Sb As a ).
COBALTIC LEAD ORE, Arseniuret of lead containing cobalt.
BOULANGERITE, Plumfjostib. Antimono-sulphuret of lead.
DUFRENOYSITE, Arseno-sulphiuet of lead.
CLAUSTHALITE, Selenid of lead.
TELLURID OF LEAD.
BOURNONITE, Antimono-sulphuret of lead.
486. The following are oxides and sulphates of lead.
MASSICOT, Yellow oxide of lead.
NATIVE MINIUM, Red oxide of lead. The red lead of commerce is an artificial
product. Plumbic ochre is a similar ore of yellow colour.
218 MINERALOGY.
SULPHATE of LEAD, Anglesite, a mineral sparingly distributed, but found occasion-
ally with galena. Cupreous anylesiie is a hydrous azure-blue sulphate of lead and
copper, found chiefly at Lead-hills, and a Cupriferous sulphate of lead also exists.
487. WHITE LEAD ORE; Carbonate of lead (H=3 3-5, SG=
6*47). A white or greyish mineral, worked for lead when abundant,
and affording, when pure, 75 per cent, of the metal. With sulphate
of barjtes it forms the pigment called Venice white.
DIOXYLITE, Sulphato-carbonate of lead.
LEADHILLITE, Sulphato-tricarbonate of lead.
CALEDONITE, Cupreous sulphato- carbonate of lead.
488. PYROMORPHITE ; Phosphate of lead (H=3'5 4, SG. = 6-5
7). A bright green or brown mineral, sometimes orange-yellow,
owing to the admixture of chromate. Streak nearly white ; lustre
resinous. Polysphceride and Muscoide are varieties.
MIMETINE, Phosphato-arsenate of lead. Hedipliane, is a variety. Nussierite is
another mineral referable to the same species.
HYDROUS ARSENATE OP LEAD.
CORNEOUS LEAD, Chloro-carbonate of lead.
CERASITE, Cotunnite, Chloride of lead.
VANADINITE, Vanadate of lead.
CROCOISITE, Chromate of lead. The pigment called chrome yellow is obtained from
this mineral. It contains chromic acid 31'85, protoxide lead 68' 15.
MELANOCHROITE, Subsesqui-chromate of lead (23'64 per cent, chromic acid).
VAUQUELINITE, Chromate of lead and copper.
MOLYBDATE OF LEAD.
TUNGSTATE of LEAD.
PLUMBO-RESINITE, a doubtful mineral containing oxide and phosphate of lead,
alumina, and water.
ANTIMONATE OP LEAD.
TIN.
489. A useful metal, of silver-white colour, having a peculiar taste,
and an odour recognized when the metal has been long held in the
hands. Tin is very malleable, and may be beaten into very thin
plates, especially at a temperature about that of boiling water. It
has, however, little tenacity, a wire of -^th of an inch breaking
with a weight of about 50 pounds, and it is not very ductile though
more so than lead. It may be beaten into leaves y^^th of an inch
thick. It is very fusible, melting at 442 Fahr. (a temperature
170 below the melting point of lead), and burning with a bright
flame. It gives out a peculiar cracking noise when bent, but is
scarcely if at all elastic. Its specific gravity is 7-28, but may be a
little increased by hammering.
Tin oxidises slowly on exposure, whence its value in coating iron
and copper. It alloys freely with quicksilver, bismuth, lead, and
other metals.
The principal ore of tin is the oxide, and it is obtained chiefly
from the south-west of England, Saxony, Bohemia, and Hungary in
Europe, and from Malacca and Banca in the East Indies. It is also
TIN. BISMUTH. 219
found in Chili and Mexico, and occurs in many other mineral dis-
tricts, but in very small quantities. About 5000 tons are produced
annually in England, and not more than that quantity from all other
known localities. Tin is much used in the manufacture of tin-plate
(iron coated with tin) and for tinning copper, and also as tin-foil,
which, alloyed with quicksilver, forms the reflecting surface in glass
mirrors. The salts, dissolved in muriatic acid, are used in dyeing and
calico-printing, and the metal is alloyed with copper in various pro-
portions, to form bronze, bell-metal, speculum metal, &c.
NATIVE TIN.
TIN PYRITES, Bell metal ore, Sulphuret of tin.
490. TIN ORE; Oxide of tin (St0 2 H=65, SG=6-9). The
only important ore of tin. Occurs crystallised, massive, or in grains ;
frequently as gravel. Colour brown or black ; in veins in crystalline
rocks, often with wolfram, copper, and iron pyrites, and other mine-
rals. Wood tin is the name given to botryoidal and reniform shapes,
with concentric and radiated structure. Toad's eye tin is the same
variety on a small scale. Stream tin is the gravel-like ore found with
detritus.
Tin ore resembles in colour and form, several minerals, from which it is often de-
sirable to distinguish it. The principal of these are Brown idocrase, Zircon, Zinc
blende, some tantalates, and Wolfram (tungstate of iron). Its high specific gravity is
a sufficient characteristic with respect to the three minerals first named, of which the
specific gravities are 3'3, 4'4, and 4'1, respectively, instead of 6'9. The tantalates
are not so hard, barely scratching glass and being readily scratched by steel.
Before the blow-pipe, the oxide of tin gives metallic tin with soda, and an opal white
enamel with borax. The tantalates colour borax yellowish-green, like oxide of iron,
and wolfram is lamellar and readily fusible.
BISMUTH.
491. A metal of considerable interest and some value, employed
in the arts in a variety of ways. It is chiefly found native, and the
whole -supply at present comes from Saxony. It has a greyish or
reddish- white colour, with a distinct reddish shade. SG=9'9.
The metal crystallises readily in cubes. Its texture is generally crys-
talline. It is brittle of hardness between copper and lead, breaks
under the hammer, and cannot be drawn into wire. It fuses at 497
Fahr. It is not a common metal, and is usually associated with iron,
arsenic, and other metals, or with sulphur and oxygen. Native
bismuth is occasionally found.
When mixed with other metals, bismuth generally renders them
more fusible, but this is not the case when only present in small quan-
tity. The uses of bismuth are in the manufacture of type-metal, and
of some kinds of solder j it is also used in the form of nitrate as a
cosmetic (Pearl powder). Plumber's solder consists of 1 bismuth, 5
lead, and 3 tin. A mixture of 8 bismuth, 5 lead, and 3 tin consti-
tutes a fusible metal which melts at a heat a little below that of
220 MINERALOGY.
boiling water (200 Fabr). A small addition of mercury adds to
the fusibility. Tbe nitrate of bismuth is employed as a mordant for
lilac and violet dyes in calico printing.
SULPHURET OF BISMUTH contains 81 per cent, bismuth, and fuses in the flame of
a candle.
ACICULAR BISMUTH, Sulphuret of bismuth, lead and copper, with gold.
TETRADYMITE, Tellurium and bismuth.
BISMUTH OCHRE, Oxide of bismuth with carbonate of iron.
BISMUTITE, Carbonate of bismuth.
BISMUTH BLENDE, Silicate of bismuth.
URANIUM.
492. A very combustible metal, burning in the air at a tempera-
ture of 400 Fahr., but unaltered by exposure at ordinary tempe-
ratures. It more resembles the metallic bases of the alkaline earths,
and especially magnesium, than the true metals ; it has, however, a
metallic lustre equal to that of silver, and it is malleable to a certain
extent. Its colour is greyish or reddish-brown. SG=9. It is
almost infusible. The oxides of Uranium are used in the porcelain
manufacture as a pigment, yielding a fine orange tint in the enamel-
ling fire, and a black colour in that in which the porcelain is baked.
PITCHBLENDE, Oxide of Uranium (UO. H=i5'5, SG=6'35 6'48). A greyish,
brownish, or velvet black mineral, often massive; opaque; dull; containing 79 to 87
per cent, of protoxide of uranium with silica, lead, iron, and some impurities. It
occurs in veins with ores of lead and silver in Saxony, and with tin in Cornwall.
Uranic ochre is a hydrous peroxide found with pitchblende. It is a yellow pulveru-
lent mineral. Coracite resembles pitchblende, but contains alumina. Gummi-erz,
or hyacinth-red pitchblende, is a variety with Vanadium. Pittin-erz is another
variety.
URANITE, Phosphate of Uranium. This includes two minerals, Uranite and Chal-
kolite, the one containing phosphate of lime, and the other phosphate of copper, com-
bined with the phosphate of uranium. They are very brittle, the former is of
bright clear yellow, and the latter of green colour. H=2, SG=3'12 or 3'33.
SAMARSKITE, Urano-tantalate, Oxide of uranium with niobic and tungstic acids.
JOHANNITE, Uran vitriol, sulphate of uranium.
TUNGSTEN.
493. Tungsten is a hard brittle metal of light steel-grey colour and
brilliant metallic lustre. SGr=17'5. Barely fusible at the greatest
heat of the smith's forge, but when heated to redness in the open air
it burns into the peroxide (tungstic acid). Its ores, tungstates of
lime, iron, and manganese, are very frequently associated with those
of tin, and injure the latter greatly. Tungstic acid has been found
native. No use has been made of it in the arts, nor have any of its
compounds been found valuable.
WOLFRAM, Tungstate of iron and manganese (see 458, 490).
TUNGSTATE OF LEAD.
TUNGSTATE OF LIME.
TUNGSTIC OCHRE.
MOLYBDENUM. VANADIUM. COPPER. 22 1
MOLYBDENUM.
494. Molybdenum is a silver-white, brittle, very infusible metal ;
not to be procured in buttons by the heat of the smith's forge, and
having a specific gravity of 8'64. It oxidises readily. It occurs in
nature with sulphur and oxygen, and also with lead as Molybdale of
lead. The sulphuret resembles lead and is remarkably unctuous to
the touch, by which it may be readily distinguished. This metal has
been little used in the arts.
MOLYBDENITE, Sulphuret of molybdenum (Mb S 2 ). Used sometimes in colouring
porcelain.
MOLYBDIC OCHRE, Molybdic acid, or oxide of molybdenum.
VANADIUM.
495. A silver-white metal, obtained from some Swedish ores of iron,
and from Vanadinite (a vanadate of lead), and vanadates of copper,
or combined with lime. It has no value in the arts, unless a sugges-
tion to employ vanadate of ammonia as a writing fluid should be
found of importance.
COPPER.
496. This very important metal has been known from the earliest
times, and is used in a vast variety of operations in the arts. It is,
when pure, of a peculiar and characteristic red colour, and transmits
a beautiful green-coloured light when in extremely thin pellicles,
obtained by a chemical process. Its density varies. SG=8'78
8-96. It acquires a disagreeable odour by rubbing, and has a distinct
taste. It melts at the temperature of 1996 Fahr., and at a white
heat burns with a green flame. It is very malleable, being reduced
by hammering into thin leaf, and it is also capable of being drawn
into very fine and strong wire. A thread whose diameter is J^th of
an inch supports a weight of 300 pounds. Copper is the most
sonorous of all metals ; it is harder and more elastic than silver. It
bears exposure to dry air perfectly unaltered, but damp air and acid
vapours convert it into a green substance, called verdigrease.
Copper is found native in Cornwall, in the Ural mountains, in
China, and in Brazil, either in octahedral crystals (H = 2-5 3, SG
= 8-58) or in threadlike, mosslike, or arborescent shapes, generally
in granite or metamorphic rocks, and especially at their junction.
It generally contains silver. It is also found native in very large
masses in volcanic rocks on the shore of Lake Superior, where one
lump has been quarried whose weight was estimated at 80 tons ; it
measured 50 feet in length, 6 feet deep, and averaged 6 inches in
thickness. Silver is not associated with these masses in the shape
of alloy, but intimately mixed in grains and strings.
The chief ores of copper from which the metal is obtained for the
market are the yellow and grey sulphurets, the oxide, and the carbo-
nate. The solutions of the sulphate also yield some portion. The
222 MINERALOGY.
quantity of metal obtained from Europe is about 26,000 tons annu-
ally; in addition to which a large quantity is brought from Chili,
from South Australia, and lately from North America. The ores
from Cornwall and Devon yield about 12,000 tons annually.
Copper is used by itself as a metal very extensively in the manu-
facture of machinery of various kinds and in sheathing ship's bot-
toms. It is also alloyed with tin in bronze, speculum metal, and
bell-metal; with zinc in brass, pinchbeck, tombac, and Dutch gold, and
with nickel in German silver ; it is worked for ornamental purposes
in the form of Malachite (green carbonate) ; Azurite (the blue car-
bonate) is used occasionally as a gem ; and the sulphates are valuable
in dyeing. Other salts are employed in the manufacture of blue and
green colours and in medicine.
497. VITREOUS COPPER ORE; Bi-sulphuret of copper (Cu 2 S, con-
taining sulphur 20*6, copper 77, iron 1-5 ; Rhombic ; H=2-5, SG=
5-5 5*8). Colour blackish lead-grey, tarnishing blue or green;
lustre dull. Fusible in the flame of a candle ; soluble in nitric acid.
Resembles sulphuret of silver, but is easily distinguishable by the
blow-pipe button or by the colour of the solution in nitric acid,
which is, in this mineral, green. This is one of the most important
of the ores of copper, and is found with other ores in Cornwall, Scot-
land, Saxony, Silesia, Norway, Siberia, and the United States. It
passes into Black copper ore, and is accompanied by Variegated
vitreous copper.
STOMEYRINE, Sulphuret of silver and copper (Hr=2'5 3, SG=6'2 6'3), found
massive or crystalline. Contains silver 52'9, copper 31 '4, and sulphur 157. Colour
like the former, but with brighter lustre.
BLUE COPPER, Covelline, Indigo copper. Sulphuret of copper (Cu S, sulphur 32'
copper 66-, H=2 SG=3'8).
SELENID OF COPPER.
EUKAIRITE, Selenid of silver and copper.
PHILLIPSITE, Sulphuret of copper and iron (FS-|-2Cu 2 S, H=3, SGrr 5), contain-
ing copper 61, iron 14, sulphur 27'75. It is an ore found in Tuscany, and worked
there. Colour reddish-brown, fracture reddish, conchoidal and unequal.
498. COPPER PYRITES ; Sulphuret of copper and iron (Sulphur
36-2, copper 33-8, iron 30- ; Square Prismatic, H = 3'05, SG=
4'17). This is the most important and most abundant ore of copper
in England, Sweden, and various other places. It occurs in tetrahe-
dral or octahedral crystals, and in dendritic forms, but most fre-
quently massive. It is of brass-yellow colour, high metallic lustre,
and frequently iridescent. (Peacock ore.) It is often much mixed
with iron pyrites. It resembles native gold and iron pyrites, and
sometimes tin pyrites, but is easily distinguished by its greater
hardness and shade of colour from the first-named mineral, by its
less considerable hardness from the next, and by its behaviour under
the blow-pipe from the latter. It resembles also Phillipsite, from
COPPER ORES. 223
which it may be distinguished by its lower specific gravity, and the
colour, when newly fractured. The average quantity of metallic
copper yielded by the ore is often only about 8 or 9 per cent.
499. GREY COPPER ORE ; Fahlerz. A mixed sulphuret, contain-
ing, sulphur 26, antimony 24, copper 35, with variable proportions
of arsenic, zinc, and silver. It corresponds with another ore, called
Silver Fahlerz, in which silver replaces the copper. H = 3'5, SG=
4-6 5. Brittle. Colour steel-grey ; bright metallic lustre.
TENNANTITE, Arseniferous grey copper.
ARSENICAL COPPER (Cu 3 As).
500. RED COPPER ORE (Cu 2 0) contains copper 88-78, oxygen
11-50. (H = 3 5 4, SG = 6.) It has a deep red colour of various
shades, and is found crystalline, massive, and earthy, but is not
present in sufficient abundance to be used as an ore. A variety, of
brick-red colour, occurs in Siberia, and is called by the German
mineralogists Ziegel-erz, or tile-ore.
501. TENORITE ; Black oxide of copper; is a valuable ore in
many mines. It occurs in dull, black, earthy masses, soiling the
fingers. It yields 60, 70, or even 80 per cent, of copper, and is con-
sidered to be a natural protoxide, but often contains sulphur, and is
most likely the product of the decomposition of other ores. When
found with other copper ores, there is little danger of mistaking this
mineral. In other cases, as it resembles the oxides of manganese
and cobalt, it may be distinguished by the colour given to the button
of glass, obtained under the blow-pipe. In the present mineral it is
emerald-green, in manganese violet, and in cobalt rich blue.
502. AZURITE ; Blue carbonate of copper. A deep blue or azure-
coloured mineral (Monoclinic II = 3 '5, SG=3-83), containing, carb.
ac. 24, ox. copper 70, water 6; generally crystalline, but also amor-
phous. Found in beautiful crystals at Chessy in France, in Siberia,
lately in South Australia, and elsewhere. When abundant it is
valuable as an ore of copper.
503. MALACHITE; Green carbonate of copper (Monoclinic H=2*5,
SG=4). Contains, carb. ac. 18', deut-ox. copper 70-5, water 11-5.
This beautiful ore, remarkable for its rich velvet-green colour, is
probably in all cases an incrustation or deposit from aqueous solu-
tion. Till lately, it was only found abundantly in Siberia, at Nijny-
Tagilsk, whence very large quantities have been obtained, and where
the finer specimens are greatly valued as an ornamental stone.
Within the last few years the mines of South Australia have proved
extremely rich in the same kind of ore, and it is now worked com-
monly, and to great advantage for the metal. It may be recognised
by its colour, which, however, resembles that of several salts of copper,
lead, and uranium. Malachite may be distinguished by its silky
texture, and its complete solution, with effervescence, in nitric acid.
224 MINERALOGY.
BURATITE, Hydro-carbonate of zinc, copper, and lime.
MVSORINE, ( Cu (7) Anhydrous carbonate of copper.
ATACAMITE, Chloride of copper.
SULPHATO-CHLORIDE OF COPPER.
DIOPTASE, Silicate of copper, contains about 50 per cent, of oxide of copper.
504. CRYSOCOLLA; Hydro-silicate of copper. A bright or bluish-
green, massive or earthy mineral, found in Siberia and America,
containing from 40 to 53 percent, of oxide of copper and 17 per
cent, of water, and sometimes used as an ore. It is distinguished
from malachite by its residuum after exposure to the action of nitric
acid. Velvet copper ore is probably also a silicate.
505. BLUE VITRIOL, Sulphate of copper, occurs native with the
sulphurets of copper as the result of decomposition. It is a soluble
salt, and easily recognised by its nauseous metallic taste.
BROCHANTITE, Sub-sulphate of copper, insoluble. Kcenigite is identical.
506. The following phosphates and arsenates of copper are of no
value in the arts. The arsenates give the garlic odour before the
blow-pipe. The phosphates give no fumes, and exhibit the reaction
of phosphoric acid.
LIBETHENITE, Aplierese, Phosphate of copper (ox. copper 667, ph. ac. 28 7, water
4'3), probably amorphous with Olivenite.
PHOSPHORI-CALCITE, Ypoleine, Hydro-phosphate of copper (ox. copper 62'8,ph. ac.
217, water 155). Trombolite and Pelocronite are varieties.
OLIVENITE (Ox. copper 58, arsenic acid 21, water 20).
ERINITE (Ox. cop. 59'4, ars. ac. 33'8).
LICORONITE (Ox. cop. 36, ars. ac. 22'5, water 25).
APHANESITE (Ox. cop. b'2'8, ars. ac., 27, water 7*5).
EUCHROITE (Ox. cop. 47*5, ars. ac. 34, water 19), Copper froth is a variety.
CONDURRITE ( Ox. 60'5, ars. ac. 26, water 9).
COPPER MICA (Ox. cop. 58, ars. ac. 21. water 21 ).
VOLBORTHITE, Vanadate of copper.
SILVER.
507. This important and valuable metal is very widely distri-
buted over the earth, and is found either native ; in ores, combined
with oxygen, sulphur, and chlorine ; or with other metals, of which
antimony, iron, arsenic, lead, copper, bismuth, and cobalt may be men-
tioned as the principal. The associated earthy minerals and rocks are
granite and other porphyritic rocks, gneiss, and various metamorphic
rocks, and occasionally limestones, sandstone, and shales, of different
geological periods.
Silver is distinguished by its beautiful white colour and brilliant
lustre, which does not readily tarnish on exposure, unless sulphur-
ous vapours are present. When perfectly polished it reflects more
light and radiates less heat than any other metal. Its specific
gravity is 1047. It is harder than gold, but softer than copper, and
the addition of a small alloy of copper hardens it. Next to gold, it
is the most malleable metal, and it has also great tenacity, a wire of
SILVER. 225
of an inch supporting nearly 200 pounds. It fuses at a white
heat at the temperature of 1873 Fahr., and absorbs a large quantity
of oxygen gas when kept long in a pure state, melted and exposed
to the air. It has been beaten into leaves j-^nuoth of an inch in
thickness, and drawn into wires finer than the human hair. It is
flexible. It is acted on by nitric and sulphuric, but by no other,
acids.
Silver is obtained chiefly from the sulphurets often in combination
with antimony ; and also from the chloride, and native silver. South
America has supplied the largest part, although the mines of Saxony,
Bohemia, Hungary, Spain, Norway, the Hartz, Austria, and Russia,
as well as many in Asia, have yielded enormous quantities. It is
estimated that the value of the silver raised annually amounts to
more than 5,000,000 of pounds sterling.
The uses of silver are numerous and for the most part well known.
In its pure state it is too soft for coin, plate, and other ornamental
purposes, requiring an alloy of copper, by which it becomes much
harder without material alteration of colour or other properties. The
standard silver of British coin is an alloy of 18 dwt. of copper to 11
oz. 2 dwt. of pure silver : the pound troy of 12 ounces being coined
into 66 shillings. In the arts silver is employed in silvering or
plating other metals either by a thin coating of the solid metal, by
solutions of silver, or by the process of electro typing. The oxide of
silver is used in giving a yellow colour in porcelain painting the
nitrate is used in surgery as a caustic, and mixed with alcohol it
forms a fulminating powder used in the preparation of percussion
caps, lucifer matches, &c. The iodides and nitrates of silver are
important ingredients in the processes of Daguerreotype and Calo-
type.
NATIVE SILVER is generally combined with from 10 to 15 per cent,
of copper or bismuth, and is often crystallised in octahedrons. Native
amalgam is a combination of mercury with silver, already alluded to,
and represented by the formula AgHg 2 . Arquerito is another com-
bination, and consists of Ag 6 Hg. It'has been regarded as native
silver, and is much worked in the rich mines of Arqueros in Chili.
It is malleable. SG=10'85.
AURIFEROUS NATIVE SILVER.
ANTIMONIAL SILVER (Ag 2 Sb). An ore accompanying arsenical ores of silver, but
not abundant enough to be worked.
ARSENICAL SILVER (AgF 2 As, the iron being regarded as isomorphous with silver)
A rich ore very variable in its yield of silver; silver white, brittle, yielding readily
the garlic odour. Sometimes valuable as an ore.
MOLYBDIC SILVER.
508. VITREOUS SILVER; Sulphuret of silver. (AgS, H=2 > 5, SG
= 6*9 7'2.) The richest and most abundant ore of silver. Found
crystalline, branching, or dendritic, and amorphous ; malleable ; rea-
Q
226 MINEEALOGY.
dily fusible. Colour lead or steel-grey ; easily tarnished. It resem-
bles the grey sulphuret of copper, but is easily distinguished by its
specific gravity. It contains, when pure, 86'5 per cent, of silver.
509. BRITTLE SILVER ORE; Black silver, Sprbdglaserz (H=3'5,
SG=5'9 6 -9). Sulphuret of silver and antimony, copper and
arsenic sometimes replacing the silver. A very important ore in the
South American mines. Specimens have been found to contain from
66 to 68 per cent, of silver, and others containing somewhat more
silver, and some arsenic, have been named Polybasite. The specific
gravity is the best test of this, as of the preceding ore.
SULPHURET OF SILVER AND ANTIMONY, SchH.fgla.serz (silver 22*93, lead 30*27,
antimony 27'38, sulphur 18*74).
FLEXIBLE SULPHURET OF SILVER, Sulphuret of silver and iron. It is very soft,
yielding readily to a knife.
STERNBERGITE, Sulphuret of silver and iron (Ag S 2 -j-4 FS).
SULPHURET OF SILVER AND COPPER.
510. RUBY SILVER (3AgS + Sb 8 S 3 , H=2_2-5, SG=5-72-5-84).
An abundant ore of silver in Mexico, and found in Saxony. Easily
distinguished by its brilliant cochineal colour and red streak. It is
transparent or translucent. It yields nearly 60 per cent, of silver.
There are two varieties, one dark and the other light red, the former
combined with about 20 per cent, of antimony, and the latter with
15 per cent, of arsenic.
PROUSTITE (3 Ag S+As 2 S 3 ).
MIARGYRITE, Antiiuonial sulphuret of silver.
SELENIURET OF SILVER (Ag Se).
511. HORN SILVER; Chloride of silver. (AgCl 2 , SG=5'27.) Con-
tains, when pure, 68 to 76 per cent, of silver. A soft mineral, of
grey, green, or bluish colour ; cutting like wax or horn. Readily
known by its softness, and much worked in South America and
Mexico, especially at Potosi.
IODIC SILVER (Ag 2 I).
BROMIC SILVER ( Ag Br 2 ).
CARBONATE OF SILVER (Ag C 2 ).
GOLD.
512. Gold is found only native, and rarely pure, being generally
alloyed with silver, and frequently with copper, palladium, and os-
mium. It always presents the peculiar yellow character which
belongs to it, and takes a very brilliant polish. Its hardness is infe-
rior to that of silver, but greater than tin and lead. It is the most
malleable and, with the exception of iron, the most tenacious metal.
Its specific gravity is very high (amounting to 14*857 for pepitas,
and as much as 19*258 when hammered). It is fusible at a tempe-
rature of 2016 Fahr., but is unaltered by exposure. Beaten into
thin leaves it is transparent, and transmits light of a beautiful green
colour. It also appears of brilliant greenish colour when in fusion.
GOLD. 227
Gold has been formed into wire of the diameter of only j~ th of
an inch, 550 feet of it weighing only 1 grain. It has been beaten
into leaves only 2so 1 ooo th of an inch in thickness. It expands more
than any other metal when fused. It is unaffected by any of the
simple mineral acids, but dissolves in nitro-muyiatic acid.
Gold occurs in crystals ; in dendritic and branching fragments ; in
filaments, grains, and minute flat spangles ; and also in lumps or
pepitas. It is rarely obtained with profit from the veins in which
it has been originally formed, and is chiefly procured from gravel
and detritus, together with which it has been removed by the action
of water from its original position in rocks. JSlectrum is a variety,
containing a large proportion of silver, which seems to replace and
be isomorphous with the gold. The palladium-gold, or Jacotinga
of Gongo Soco in Brazil, is another variety, and there is also found
occasionally another mixture of gold and palladium, and an alloy of
gold with rhodium.*
The uses of gold are numerous, and for the most part well known.
Alloyed with one llth part by weight of copper or silver, it is used
in this country as a coin, being then much harder than in its pure
state. With a still larger admixture of other metal, it is very exten-
sively used in jewellery. In consequence of its extreme divisibility
and malleability, it is used in gilding or coating other substances
with an exceedingly thin film, which is very durable, owing to the
perfect manner in which it resists oxidation from exposure. Some
of the salts of gold are used in porcelain painting.
The rocks in which gold is found are very variable, including
granites, slates and schists, and even limestones. The alluvial depo-
sits containing particles of the metal, and most prolific when sifted
and washed, are quartzy sands with iron. It has been considered
that the sand of any river pays for washing if it yield on an average
24 grains of gold per hundred weight of sand.
The chief localities in which gold is worked to profit are, 1. the
Ural mountains and the adjoining district of Siberia ; 2. the upper
part of California, only recently found to produce this valuable metal
in abundance, but promising a large supply ; 3. Brazil ; 4. Central
and Western Africa, the exact localities being unknown ; 5. the
East Indian Islands ; and, 6. Bohemia and Transylvania. The total
annual supply, on an average of several years, does not exceed 40
tons, its value being about 5,000,000 sterling ; but during the past
year (1849), more than 10 tons have been reduced in London from
the recently discovered gold-washings of California.
Masses of gold of considerable size have been found from time to
time ; several specimens weighing as much as 1 6 pounds troy, one of
* The author endeavoured to collect and arrange in a useful form the various facts relating
to the distribution of gold, in a little work (" The Gold Seeker's Manual"), published at the
commencement of the year 1849.
228 MINERALOGY.
27 pounds, and one, discovered in 1842, weighing nearly 100 pounds
troy. These are all from the Ural ; but other large masses have been
reported from the province of Quito weighing 50 and 60 pounds.
Auro-tellurite and Graphic tellurium are ores of tellurium, chiefly
valuable for the gold they contain. The latter contains 30 per cent,
of gold.
It may be useful to mention that the English sovereign contains 123'274 grains
troy of gold, 22 carats fine, and therefore 113'001 grains of fine gold. Thus the
ounce troy of fine gold is worth 41. 4s. \\\d., nearly, and the ounce of standard
gold, being l-12th less, amounts to 31. 17s. lOgrf. The French Napoleon weighs
99-564 grains, of which 89-61 are fine gold. The Dutch 10 florin piece weighs
103-88 grains, and the American eagle 269-85 grains, of which 232 are fine. The
pound troy of standard gold is coined into 46-^j- English sovereigns, and the pound
avoirdupois of fine gold is worth 611. 18s. lid.
PLATINUM.
513. This rather remarkable metal, of whitish iron-grey colour and
extreme specific gravity (rising to 21 '53 in purified and prepared
specimens), is distributed, like gold, in grains or pepitas, and ob-
tained from the sands of valleys opening out from crystalline rocks.
It cannot be melted by the heat of the fire, but admits of welding in
the manner already described for iron ( 449). Its hardness is
4 45, and it is scratched by iron. It is usually combined with
palladium, rhodium, iridium, and osmium, besides copper and iron.
The malleability of platinum is very considerable, as it may be
beaten into leaves as thin as tin-foil. Its ductility is however far
more remarkable, as Dr. Wollaston obtained a wire not more than
ao * 00 th of an inch in diameter. Its tenacity is very great, as the
same chemist found that a wire of -j-g^T^*^ 1 ^ an ^ nc ^ w ^l support
a grain and a third without breaking. Except Tantalum it is the
most infusible of all metals. It is very slightly magnetic. In thin
plates it is ductile and flexible.
Platinum is found (always in the metallic state) in Brazil and
Peru, in Spain, and in the Ural Mountains. The particles are gene-
rally small and rarely larger than a pea, but a mass has been found
weighing 20 pounds.
It is of great value in the manufacture of utensils and instruments
required to resist oxidation, and the action of acids and mercury, at
very high temperatures. It is however not very plentiful. Coins
have been made of it in Russia.
IRIDIUM.
514. A metal which has been rarely applied to any use. It is
found with the ores of platinum in the washings of two localities in
the Ural The specimens found are generally mixtures or alloys of
this metal and another, equally rare, named OSMIUM. Iridium is
OSMIUM. RHODIUM. PALLADIUM. 229
extremely hard, and its specific gravity is 18-68. It is brittle, of
whitish colour, and when carefully polished resembles platinum. It
is scarcely affected by acids but forms several oxides and chlorides,
and combines readily with carbon. It is infusible in the heat of a
smith's forge, but may be melted before the oxy-hydrogen blow-pipe.
It appears to be one of the metals that do not decompose water. The
name is derived from the variegated colours (iris, a rainbow) of its
solutions.
OSMIUM.
515. OSMIUM is a dark-grey or blue metal, infusible except before
the oxy-hydrogen blow-pipe, and having a specific gravity of 19-5 (?).
It is usually found alloying platinum. Its peroxide is extremely
volatile and has a pungent odour. It has not been applied to any
useful purpose.
OSMIRIDIUM is a natural alloy of Osmium and Iridium.
RHODIUM.
516. This metal is very rare, and is often, when found, associated
with the native platina of Peru. It gives hardness to steel, and in
the proportion of 1 to 2 per cent, might be alloyed with that metal
to some advantage if it were more abundant. Like Iridium, it has
been used instead of gold to manufacture the nibs of metallic pens.
It is of whitish colour, difficult of fusion like Iridium, and extremely
hard and durable. SGr=lO65. The name is derived from the red
colour (rhodon, a rose) of some of its salts.
PALLADIUM.
517. A metal not at present much used, but more abundant than
either of the preceding. It is extracted from the auriferous sands
and platinum of Brazil. It greatly resembles Platinum in colour,
and has a splendid steel lustre when polished. It is malleable and
ductile ; very flexible when in thin laminae, but not very elastic.
SG=11'3 11*8. Somewhat harder than bar iron and about equal
to fine steel. Fuses with great difficulty at the highest heat of a
smith's forge. It is acted on by nitric acid, but resists ordinary ex-
posure without tarnish. It has been used in the manufacture of
some philosophical and surgical instruments.
Native Palladium occurs in grains apparently composed of di-
verging fibres, but in other respects these grains differ little in
external character from those of the native platina among which
they are found. It melts easily with the addition of sulphur, and
forms a deep red solution with nitric acid.
230
APPENDIX.
ANALYSES OF IMPORTANT MINERALS.
TABLE I.
<
SILICATES CONTAINING ALUMINA.
Mineral.
Silica.
Alumina
(Glucina)
Lime
(Magnesia).
Potash or
Soda.
Iron oxides
(Manganese
oxide).
Water.
1 . Cyanite
36-67
63-11
....
...
1-19
2. Garnet, No. 1
38-30
21-20
81-25
....
6-50
3. Do. No. 2
39-62
19-30
r 3-28
* 2-00 Mg
....
34-05
0-80 Mn
4. Do. No. 3 . .
37-55
26-74
/ 31-35
1 4-78 Mu
5. Do. No. 4
35-00
14-25
....
....
c 14-00
35-00 Mn
6. Epidote
33-50
15-00
14-50
....
{l2-00 Mn
7 lolite
50-25
32-42
10*85 Mg
/ 4-00
1 0-68 Mn
8. Emerald
66-45
16-75
0-60
15-50G7
9. Felspar, No. 1
65-91
21-00
0-11
no-is*
1 3-50 Na
8*00 K
10. Do. No. 2 ..
66-60
18-50
1-09 Mg
\ 4-00 Na
11. Phonolite
57-66
19-96
rl-01
1 1-53 Mg
6-06 K
6-98 Na
3-42
0-75 Mn
}2-33
1 Albite
67*99
19-61
0'66
11-12 Na
0-70
] 3. Leucite
53-75
21-63
21-35 JT
14. Mesotype . .
48-17
26-51
....
16-12 Na
....
9-17
15. Stilbite
58-00
16-10
9-20
....
17-40
16. Chlorite
31-47
16-67
32-56 Mg
5-97
12-43
No. 1 is from the St. Gotthard, by Resales. No. 2, an Essonite, from Ceylon, by
Klaproth. No. 3, a precious garnet (Almandine) from the Zillerthal, by K obeli. No.
4, a Melanite, of red colour, from Lindbo, by Hisinger. No. 5, a Spessartin, or man-
ganesian garnet, from Spessart, by Klaproth. No. 6, a violet or manganese Epidote,
by Cordier. No. 7, a specimen from Fahlun, by Stromeyer. No. 8, a Beryl* from
Siberia, by Klaproth, containing 15-50 per cent, of Glucina. No. 9, a yellowish
white variety from the Ural, by G. Rose. No. 10, a Glassy felspar, from the
Drachenfels, by Berthier. No. 11, is a mean of six analyses, from various localities,
by Gmelin. No. 12, a specimen, from Finland, by Tengstrom. No. 13, a crystal,
from Somma (Vesuvius), by Klaproth. No. 14, a specimen from Auvergne, by
Fuchs. No. 15, a specimen from Desmine, by Moss. No. 16, from the Zillerthal,
by Kobell. Where no other base is mentioned, Alumina is understood in the second,
Lime in the third, and Iron in the fifth column.
ANALYSES OF IMPORTANT MINERALS.
TABLE II.
NON-ALUMINOUS AND OTHER UNMETALLIC SILICATES.
231
Mineral.
Silica.
Magnesia
(Lime).
Alumina
(Zirconia).
Potash,
Soda,
Lithia.
Metallic oxides,
(various) .
Various
Substances.
17. Talc ....
63-00
33-60
....
....
3-40 Aq
18. Steatite ..
63-95
28-25
....
0-60 Fe
2-71 Aq
19. Serpentine
41-95
40-64
0-37
11-68^9
/ 8-17 Fe
20. Olivine ..
40-09
50-49
0-19
....
J 0-20 Mn
( 0-37 Ni
21. Zircon ..
32-60
64-50 Zr
....
2-00 Fe
22. Hornblende
No. 1.
}eo-io
24-Vl ,,
12-73 Ca S
0-42
....
r 1-00 Fe x
X 0-47 Mn/
0-83 HF
0-15 Aq
23. Do. No. 2
42-24
13-74 ,
12-24 Ca /
13-92
s 14-59 Fe
X 0-33 Mn
24.Augite,No.l
54-64
18-00 ,
24-94 Ca J
....
r 1-08 Fe
X 2-00 Mn
25. Do. No. 2
53-55
15-25 >
22-21 Ca /
0-14
....
, 8-14 Fe
i 0-73 Mn
6. Do. No. 3
48-70
9-90 i
14'60(7a /
1-60
20-30 Fe
2-20 Aq
27. Diallage..
53-71
17-55 ,
17-06 Ca S
2-82
8 ' 08 {Mn
} 1-04 Aq
28. Topaz
35-52
55-14
....
17-21 F
29. Mica,No. 1
41-00
18-86
16-88
8-76 K
{ 5-86 Fe /
4-30 Aq
30. Do. No. 2
36-54
0'93 Ca
25-47
5-48 K
r 27-06 Fe .
X 1-02 4f*'
2-70 F
/ 12-07 N
31. Tourma- >
line, No. 1 /
37-80
1-42
30-56
2-09 Na
1 v * \
\ 0-50 F \
1 2-50 Mn)
9-905
32. Do. No. 2
39-70
0-16
40-29
(3-02Z
} 2-30 Mn
6-655
33. Lapis lazuli
35-80
3'lQCaC 2
34-80
23-20 Na
....
3-10 S
34. Spinelle . .
2-02
26-21
69 01
/ 0-71 F
i 1-10 Cr
No. 17 is from the Zillerthal, by Beudant. No. 18, from near Abo, by Teng-
strb'm. No. 19, Noble serpentine^ from Fahlun, by Lichnell. No. 20, Basaltic
olivine, from the Vogelsgebirge. No. 21, from Ceylon, by Vauquelin. No. 22, Tre-
molite, from Fahlun, by Bonsdorff. No. 23, an aluminous hornblende, from Vogels-
berg, by Bonsdorff. No. 24, a Malacolite, from Finland, by H. Rose, belonging to a
group nearly colourless. No. 25, a green Baikalite,\>j H. Rose, belonging to a green
group. No. 26, Asbesttis, from the Little St. Bernard, by Berthier. No. 27, Stil-
ler-spar (greenish colour), from the Hartz, by Kbhler. No. 28, Topaz from Saxony,
by Forchhammer. No. 29, Uni-axal mica, by Kobell. No. 30, Bi-axal mica, from
Cornwall, by Turner. No. 30, a brown variety (Schorl), from Mursinsk, Russia, by
Rammelsberg. No. 31, a specimen of noble tourmaline or Rubellite, from the same
locality, and by the same chemist. No. 33, is by Clement and Desormes, and is con-
sidered as representing the true composition of the mineral. No. 34, Spinelle ndy,
by Abich. In the fifth column, when Roman characters are used, the protoxides of
the metals are meant; when italic, the peroxides.
232
MINERALOGY.
TABLE III.
METALLIC SILICATES.
Mineral.
Silica.
Oxide of princi-
pal Metal.
Various metals.
Various
ear thy bases.
Water.
35. Cerite
18'00
68'59 Ce
2-QO Fe
1*25 Ca
9 60
36. Manganese spar..
37 Jenite .
48-00
29*83
49-04 Mn
r 32-70 Fe i
1'51 Mn
r 3-12 Ca
\ 0-2 2 My
12-43 Ca
38. Charaoisite ....
3.9. Electric Calamine
40. Sphene
14-30
24-89
32-29
1 22-85 Fe /
60-50 Fe
66-83 Zn
41*58 Ti
1 - 07 Fe
7-80 Al
0-81 l>
26'61 Ca
17-40
7-50
41. Bismuth blende..
42. Crysocolla ....
22-23 .
26*00
69-38 Bi
41*80 Cu
r 2*40 Fe >
t 0-30 M t
2-5 Fe
3-31 Ph
3'70 Ca
1-01
23-50
No. 35 is an analysis by Hisinger. No. 36, a lamellar variety by Berzelius. No.
37, the mean of several analyses by Rammelsberg. No. 38, from Chamoisin, by Ber-
thier. No. 39, a variety from Limbourg, by Berzelius. No. 40 is from Zillerthal, by
H. Rose. No. 41, is by Kersten. No. 42, from Cornwall, by Berthier.
In this and subsequent tables the peroxide is meant where the symbol is printed
in italics.
TABLE IV.
METALLIC CARBONATES.
Mineral.
Oxide of the prin-
cipal Metal.
Carbonic
acid.
Salts of various
other metals.
Various bases.
Water.
43 Diallogite . .
50*96 Mn
31*24
7'3 FeC
r8'9 CaC
44. Spathic iron ....
45 Do
50-41 Fe
43-82 Fe
38-64
26*18
7-51 MnO
1 1-6 MgC
(2'35M ff
"1 0-32
r 23-00 C
46. Calamine
61-92 Zn
34-18
r 2 03 FeC
* 7-
47. White lead ore . .
48. Malachite . .
82-00 Pb
70'50 Cu
16-00
18'00
1 1*12 PbC
2- Fe
11-50
No. 43, is from Freiberg, by Berthier. No. 44, a crystalline variety from Hachen-
burg (Nassau), by Karsten. No. 45, a clay ironstone, from the Black band of
Lanarkshire. Amongst the various bases are included silica, alumina, and some lime.
The carbon is not pure. No. 46 is a pure variety from Nertschinsk, by Kobell.
No. 47 is from Leadhills, by Klaproth. The iron includes also alumina. No. 48
is a green compact variety from Turjinsk, by Klaproth.
ANALYSES OF IMPORTANT MINERALS.
233
TABLE V.
METALLIC OXIDES.
Mineral.
Principal metal.
Oxygen.
Other metals.
Earthy bases.
Water.
49 Pyrolusite
61*80 Mn
ot.^9
rO'66Ba^
1-57
OO i -
...
\ 0-55 Si >
50 Wad
57.72 Mn
9ft.OO
l"40/?a
10-66
51. Magnetic iron ore
68-38 Fe
OU Ltd
26-54
2-00 Mn
2-6 8 Si
52. Red Haematite . .
63-62 Fe
2672
9-66 Ti
53. Brown Haematite
55-00 Fe
24-30
4-00 Mn
2-60
1370
54. Chrome ochre . .
68-65 Cr
31-35
55. Earthy cobalt . .
22-75 Co
16-06
31-21 Mn
....
22-90
56 Red zinc .
75-04 Zn
18'46
r 0-40 Fe
. 5-50 Mn
57 Arsenite
75-76 As
24-24
68 Rutile
58-85 Ti
38-75
2-40 Fe
59. Minium
90-70 Pb
9-30
60. Tin ore
77-50 St
21-50
0-25 Fe
0-75 Si
61. Pitchblende
65-96 U
13-19
. 3-03 FF.
f 6-20 Pb
j 1-13 As
2-81 Ca ,
0-46 Mg I
5-30 Si )
0-36
I 0-65 Bi
62. Molybdic ochre . .
65-71 Mb
33-40
63. Red copper ore . .
85-50 Cu
11-50
64 Tenorite
78-83 Cu
2007
No. 49 is from Devonshire, by Turner. It contains 11 '6 per cent, of oxygen in
excess. No. 50 is also from Devonshire, by Turner, and contains 8-82 per cent, oxy-
gen in excess. No. 51, a foliated variety, from Arendal, Sweden, by Kobell. No.
52 is a variety from the St. Gotthard, by Kobell. The titanium is considered to be
titanic acid. No, 53 is an earthy hydrate of iron by Beudant. No. 54 is the chemi-
cal composition of the oxide, which is, however, rarely pure. No. 55 is a variety from
Saalfeld, by Dobereiner, in which there is 6-78 oxygen in excess. The analysis
can hardly be expected to be the same for any two specimens. No. 56, a variety by
Hayes. No. 58 is by Kersten. No. 60 by Klaproth. No. 61, from Joachimsthal,
by Rarnmelsberg.
Many of the ores, of which analyses are given in the above table, are of consider-
able importance, but very few are presented commonly in nature in a pure form. A
reference to the text will show which of them are valuable ores, and it will be ex-
plained in a future chapter how widely spread are the combinations of oxygen with
metallic bases. On the whole, it may be considered that the oxides and sulphurets
afford the principal portion of the various metals used in the arts.
234
MINERALOGY.
TABLE VI.
METALLIC SULPHURETS,
Mineral.
Principal
metal.
Sulphur.
Various other
metals.
Various
other
substances.
65. Manganese blende
62'10 Mn
37 90
47-30 Fe
52-70
67. Magnetic pyrites
59-85 Fe
40-15
68. Arsenical pyrites
34-94 Fe
20-13
43-42 As.
69 Cobalt pyrites
43-20 Co
38-50
r 14-40 Cu
0-33
61-34 Ni
35-79
1 3-53 Fe I
r 1-73 Fe
7 1 . Bismuth nickel
40-65 Ni
38-46
1-14 Cu
14-11 Bi
3-18 Fe
1 1-68 Cu
72. Blende
61-50 Zi
33-00
1-58 Pb
0-28 Co
4-00 Fe
73 Green ockite . .
77-55 Ca
22 -41
73-77 gb
26-23
75. Berthierite ....
54-70 Sb
31-33
, ll-43Fe
J 2-54 Mn
76 Realgar . . .
69-57 As
30-43
I 0-74 Zn
77. Orphnent ..
61-86 As
38-14
78. Cinnabar
85-00 Hg
14-25
79. Galena
83-00 Pb
16-41
0-08 Ag
80. Bournonite
39-00 Pb
16-00
, 28-50 Sb
I 13 50 Cu
81 . Vitreous copper ore
78-50 Cu
18-50
1 1-00 Fe
2-25 Fe
0-75 Si
31-20 Cu
34-46
,3080 Fe
1-10 Si
83. Grey copper ore (Fahlerz) . .
84. Silver Fahlerz {
37-98 Cu
25-23 Cu
25-77
} 23-52
{ 2-44 PI, As
/ 23-94 Sb
0-62 Ag
J 0-86 Fe
2-88 As
1 7*29 Zn
f 26-63 Sb
< 3-72 Fe
85. Vitreous silver . .
17-71 Ag
86-39 Ae
13-61
I 3-10 Zn
86. Brittle silver ore .
68-54 As
16-42
r 14-68 Sb
87. Ruby silver
58-95 Aw
16-61
1 0-64 Cu
22-85 Sb
0-30 Si
No. 65 is by Arfvedson. No. 66, by Hatchett. No. 67, by Stromeyer. No. 68
by M. Chevreul. No. 69, from Bastnaes, by Hisinger. No. 70, from'Camsdorf, by
Rammelsberg. No. 71, by Kobell. No. 72, lamellar varieties from England, by
Berthier. No. 73, by Jameson. No. 74, from Scotland, by Thompson. No. 75, from
Braunsdorf, by Rammelsberg. No. 76, 77, by Laugier. No. 78, from Carniola, by
Klaproth. No. 79, a specimen from Hanover, by Westrumb. No. 80, a variety
ANALYSES OF IMPORTANT MINERALS.
235
from Cornwall, by Klaproth. No. 81, from Katharinenberg, by Klaproth. No. 82,
a botryoidal variety from Cornwall, by Phillips. No. 83, a crystalline specimen from
Hungary, by H. Rose. No. 84, from Wolfach, in the Black Forest, also by H. Rose.
No. 85 from Joachimsthal, by Klaproth. No. 86, from Chemnitz, by H. Rose.
No. 87, from Andreasberg, by Bonsdorff.
TABLE VII.
VARIOUS METALLIC SALTS.
Minerals.
Principal
metallic and
other base.
Principal
combining
substance.
Metallic
impurities.
Earthy
impurities.
Water.
88. Psilomelane
51-22 Mn
26-28
.... {
16-50 #<>
2*00 J
4-00
8 SU Chromic iron {
30-44 Fe
12-22 Al
} 52-95 Or
0-70 Al \
43-78FeO
30*32 P
25*00
,
0*03 Si J
91. Pharmacosiderite
39-20 Fe
, 37-82 As \
i 2-53 Ph *
0-65 CaO
....
J8-61
92 Copperas . . .
25-70 FeO
98-80 fl
45-40
93. Cobalt bloom .,
36-52 Co
tt\J Ov O
38-43 As
1-o'l'FeO
23-10
94. Nickel green . .
36-20 Ni
38-30 As
r 1-53 Co
t trace Fe
.... j
23*91
95. Tungsten
18-70 Ca
75-25 W
{ 0*75 Mo
1-50 Si
96. Pharmacolite ..
25-00 Ca
50-54 As
....
....
24-46
0-70 J5V
97. White vitriol ..
28-50 ZnO
29-80 S
v / u F e
0-40 Mn
}
40*80
98. Horn quicksilver
85-11 Hg
14-89 Cl
99. An^lesite
71-00 PbO
24*80 S
1-00 Fe
2*00
100. Pyromorphite {
56-62 PbO
7-50 Pb
32-49 Ph
2-57 a
0-68 Ca Ph
0*13CaF
101. Crocoisite
68-50 PbO
31-50 Or
102. Molybdateoflead
58-40 PbO
37*00 Mb
3-08 Fe
0*28 Si
K.OQ />_
103. Uranite
61-73 U
15*20 Ph
0*06 SnO
O OO C-Q5 ^
1 57 Ba /
15-48
104. Vanadinite .. {
6 6- 33 PbO
7-06 Pb
j 23-43 V
0*16 Fe
2-45 C1H
105. Libethenite
63-90 CuO
\ 28-70 Ph
....
....
7*40
106. Horn silver
67-75 Ag
27*50 Cl
6*00 Fe {
1-75 Al
0-25 S
No. 88 is from Romaniche, by Berthier. No. 89, a crystallized specimen from Bal-
timore, by Thompson. No. 90, a compact earthy variety from Hillentrup, by Brander.
No. 91, by Berzelius. No, 93, 94, from near Schneeberg, by Kersten. No. 95,
from Pengilly, Cornwall, by Klaproth. No, 96, from Swabia, by Klaproth. No
97, from Schemnitz, by Beudant. No. 98, by Berzelius. No. 99, from Anglesea,
by Klaproth. No, 100, an English specimen, by Kersten. No. 101, by Berzelius.
No. 102, from Bleistadt, by Hatchett. No. 103, from Autun, by Berzelius. No.
104, Wicklow (? or Wanlockhead), by Thompson. No. 105, from Libethen, by
Berthier. No. 106, from Saxony, by Klaproth.
236
MINERALOGY.
TABLE VIII.
VARIOUS METALLIC MIXTURES AND ALLOYS.
Mineral.
Principal
metallic base.
Principal
combining
metal.
Other metals.
Other
substances.
3*42 Fe i
107. Smaltine
20-31 Co
74-22 As
0'89 Su
i 0'16 Cu /
, 0-34 Fe
108. Copper nickel . .
44-21 Ni
54-72 As
f 0-32 Pb I
i Trace Co)
0-40 Su
109. Antimonial nkl.
33-75 Ni
, 32-06 As 1
\27-90 Sb J
1*04 Fe
r2-65Su
12-00 Si
110. Graphic tellu- -,
rium, or gold *
r 30-00 Au->
^ 10-00 Ag'
60-00 Te
111. Arsenical antim.
37-85 Sb
62-15 As
112. Native amalgam
25-00 Ag
73-00 Hg
113. Arsenical copper
71-64 Cu
28-36 As
114. Antimonial silver
76-00 Ag
24 00 Sb
115. Arsenical silver
14-0 Ag
62-90 As
17-89 Fe
5-75 S
116. Electrum
64-00 Au
36-60 Ag
, 2-35 Ir
12-98 Fe j
117. Native platinum
73-58 Pt
1-15 R
1
/
0-60 Si
1 0-30 Pd
5-20 Cu J
118. Platin-iridium ..
55 44 Pt
/ 27-79 Ir
\ 6-86 R
1 0-49 Pd
4-14 Fe
3-30 Cu
119. Osmiridium
46-77 Ir
r 49-34 Os >
1 3-15 R. f
0-74 Fe
Nos. 107 and 108, are from Reichelsdorf, by Stromeyer. The latter is extremely
variable in different specimens. Several similar ores of nickel occur which we have
not space here to enumerate ; but the next, No. 109, is remarkable. The analysis is
the mean of two by M. Berthier. No. 110, is by Klaproth. No. Ill, from Alle-
mont, by Rmmelsberg ; but as the metals are isomorphous, there is no definite com-
pound. No. 112, from Moschel-Landsberg on the Nahe, by Heyer. No. 13, from
Chili, by M. Domeyto. No. ] 14, from Wolfach, by Klaproth. No. 115, from An-
dreasberg, by Dumenil. No. 116, from Schlangenberg, by Klaproth. No. 117, from
Nijny Tagilsk, by Berzelius. In this analysis there was found in addition 2-30 per
cent, of Osmium and Iridium in a state of combination. No. 1 1 8, from Brazil, by
Svanberg, and No. 1 19, from Katharinenberg, in the Ural, by Berzelius.
ALPHABETICAL INDEX
OF THE MINERALS DESCRIBED IN THIS DIVISION OF THE WORK.
fi& a description of minerals is of comparatively little value with-
out ready means of reference, the author has thought it advisable to
append here an alphabetical index, by which the reader may at
once find the paragraph at which any required mineral is referred to.
This index includes about 1150 names, of which nearly seven hun-
dred are synonyms, but, in the present state of mineralogical nomen-
clature, it seemed absolutely necessary to introduce this large num-
ber. Even now the index is by no means perfect, though sufficiently
so for most practical purposes.
ABRAZITE, 421.
Acadiolite, 422.
Acerdese, 445.
Achmite, 4 GO.
Acicular bismuth, 491.
Actinolite, 431.
Adhesive slate, 364.
Adinole, 413.
Adularia, 413.
Aedelforsite, 420.
Aeschinite, 430.
Agalmatolite, 422.
Agaphite, 397.
Agaric mineral, 383.
Agate, 361.
Alabandine, 444.
Alabaster, 380, 387.
Albin, 425.
Albite, 414.
Alexandrite, 441.
Alkaline earths, 373.
Allagite, 448.
Allalite, 433.
Allanite, 443.
Allochroite, 405.
Alloraorphite, 375.
Allophane, 403.
Ahnandine, 405.
Almandine ruby, 441.
Alum, 248, 398.
Alumina, 394.
Alumina salts, 394398.
Aluminates, 441.
Aluminite, 3-98.
Alumocalcite, 403.
Alunite, 398.
Amalgam, native, 480.
Amazon stone, 413.
Amber, 358.
Ambligonite, 396.
Amethyst, 360.
Amethyst, oriental, 395.
Amianthus, 433.
Ammonia salts, 369.
Amoibite, 468.
Amphibole, 431.
Amphigene, 416.
Amphodelite, 408.
Analcime, 422.
Anatase, 482.
Andalusite, 400.
Anglarite, 459.
Anglesite, 486.
Anhydrite, 388.
Anorthite, 415.
Anthosiderite, 435, 460.
Anthracite, 353.
Antigorite, 435.
Antimonate of lead, 475.
Antimonial nickel, 468.
Antimonial silver, 507.
Antimonic acid, 476.
Antimonous acid, 476.
Antimono-phyllite, 476.
Antimony, 475.
Antrimolite, 419.
Apatite, 389. -
Aphanesite, 506.
Apherese, 506.
Aphrite, 379.
Aphrodite, 391.
Aplome, 405.
Apophyllite, 425.
Aqua marine, 411.
Arfvedsonite, 431.
Argentine, 379.
Arktizite, 408.
Arquerito, 507.
Arragonite, 384.
Arsenic, 368, 477.
Arsenical antimony, 475.
Arsenical cobalt, 464.
Arsenical manganese, "444.
Arsenical nickel, 468.
Arsenical pyrites, 451.
Arsenical silver, 507.
Arsenio-siderite, 461.
238
MINERALOGY.
Arsenous acid, 477.
Asbestos, 433.
Asparagus stone, 389.
Asphalt, 356.
Astrakanite, 392.
Atacamite, 503.
Augite, 433.
Aurichalcite, 471.
Aurotellurite, 473, 512.
Automolite, 441.
Avanturine, 360.
Axestone, 410.
Axinite, 438.
Azurite, 502.
BABINGTONITE, 431.
Baierine, 458.
Baikalite, 438.
Balasruby, 441.
Baltimorite, 428.
Barolite, 374.
Barsowite, 408.
Barytes salts, 374, 375.
Baryto-calcite, 374.
Baryto-celestine, 377.
Baryto-strontianite, 376.
Basalt, 433.
Basanite, 365.
Basi-cerine, 443.
Batrachite, 429.
Beaumontite, 422.
Bell metal, 496.
Bell metal ore, 489.
Berengelite, 358.
Bergmannite, 408.
Bergmehl, 383.
Berthierite, 460, 476.
Beryl, 411.
Berzelite, 390.
Beudantine, 416.
Beudantite, 461.
Biotine, 415.
Biotite, 437.-^
Bismuth, 491.
Bismuth blende, 491.
Bismuth cobalt, 464.
Bismuth nickel, 467.
Bismuth ochre, 491.
Bismuth tellurium, 473.
Bismutite, 491.
Bitter spar, 385.
Bitumen, 356.
Bituminous coal, 354,
Black Jack, 470.
Black lead, 352.
Black silver, 509.
Black tellurium, 473.
Blende, 470.
Bloedite, 371.
Bloodstone, 362.
Blue copper, 497.
Blue John, 386.
Blue lava, 385.
Blue vitriol, 505.
Bodenite, 443.
Bologna spar, 375.
Boltonite, 428.
Bombite, 424.
Bonsdorfite, 409.
Boracic acid, 358.
Boracite, 391.
Borax, 372.
Boron, 358.
Botryolite, 438.
Boulangerite, 476, 485.
Bournonite, 485.
Bovey coal, 355.
Brass, 496.
Braunite, 444.
Brazil emerald, 438.
Breithamptite, 468.
Breunerite, 391.
Brevicite, 419.
Brewsterite, 421.
Britannia metal, 475.
Brittle silver ore, 509.
Brochantite, 504.
Bromic silver, 511.
Bromlite, 374.
Bronze, 496.
Brongnartine, 371.
Bronzite, 435.
Brookite, 482.
Brown coal, 355.
Brown spar, 385, 455.
Brucite, 391,436,472.
Bucholzite, 400.
Bucklandite, 407.
Buratite, 503.
Bustamite, 448.
CACHOLONG, 366, v. 5.
Cadmium, 474.
Cairn-gorm, 360.
Calaite, 397.
Calamine, 471.
Calcareous tufa, 383.
Calcite, 377, 379.
Calc spar, 378383.
Caledonite, 487.
Cancrinite, 416.
Cannel coal, 354.
Capillary pyrites, 467.
Carbo-cerine, 443.
Carbon, 350.
Carbonic acid gas, 358.
Carburet of iron, 352.
Carburetted hydrogen, 349.
Carnelian, 362.
Carnatite, 414.
Cat's eye, 360.
Cawk, 375.
Cement stone, 382.
Celestine, 377.
Cerasite, 488.
Ceraunite, 410.
Cerine, 443.
Cerite, 443.
Cerium, 443.
Cerium ochre, 443.
Ceylanite, 430, 441.
Chabasite, 422.
Chalcedony, 362.
Chalceolite, 492.
Chalk, 383.
Chalk, red, 453.
Chamoisite, 435, 460
Chelmsfordite, 425.
Chert, 362.
Chiastolite, 400.
Childrenite, 396.
Chiolite, 397.
Chlorine, 349.
Chlorite, 423.
Chloromelane, 435.
Chloropale, 435, 460.
Chlorophane, 386.
Chlorophyllite, 409, 428.
Chloro-spinelle, 441.
Chondrodite, 436.
Chonikrite, 415.
Christianite, 415, 422.
Chrome ochre, 462.
Chromic iron, 457.
Chromite, 457.
Chromium, 462.
Chrysoberyl, 441.
Chrysolite, 429.
Chrysoprase, 362.
Chusite, 429.
Cinnabar, 481.
Cinnamon stone, 405.
Cipolino, 381.
Claussenite, 395.
Clausthalite, 485.
Clay, 402.
Clay iron stone, 456.
Cleavelandite, 414.
INDEX.
239
Clink-stone, 413.
Davyte, 398.
Clintonite, 424.
Delvauxine, 459.
Cloanthite, 468.
Dermatine, 391.
Cluthalite, 41$.
Diallage, 434.
Coal, 354.
Diallogite, 447.
Cobalt, 463.
Diamond, 351.
Cobalt bloom, 466.
Diaspore, 395.
Cobalt pyrites, 463.
Dichroite, 409.
Cobalt vitriol, 466.
Diopside, 433.
Cobaltic lead ore, 485.
Dioptase, 503.
Cobaltine, 464.
Dioxylite, 487.
Coccolite, 433.
Diploi'te, 416.
Colophonite, 405.
Dipyre, 416.
Columbite, 458.
Disthene, 400.
Columbium, 483.
Dog-tooth spar, 379.
Commingtonite, 460.
Dolomite, 385.
Comptonite, 422.
Dreelite, 375.
Condurrite, 506.
Dufrenite, 459.
Copal, fossil, 358.
Dutch gold, 496.
Copper, 496.
Dysclasite, 425.
Copper mica, 506.
Dysluite, 452.
Copper-nickel, 468.
Dysodil, 355.
Copper pyrites, 498.
Dyssnite, 448.
Copperas, 461.
Coquimbite, 461.
EARTH FOAM, 379.
Coracite, 492.
Earthy cobalt, 465."
Cordierite, 409.
Earthy quartz, 364.
Corneous lead, 488.
Edelforsite, 425.
Corundum, 394.
Edingtonite, 421.
Cotunnite, 488.
Edwardsite, 443.
Couzeranite, 416.
Egeran, 406.
Covelline, 497.
Eitrine, 360.
Crichtonite, 458.
Ekebergite, 408.
Crocoisite, 488.
Elaeolite, 416.
Cronstedtite, 435, 460.
Elastic bitumen, 357.
Cross-stone, 400, 422.
Elaterite, 357.
Crucite, 450.
Electric calamine, 472.
Cryolite, 397.
Electrum, 512.
Cryptolite, 443.
Emerald, 411.
Crysocolla, 504.
Emerald, oriental, 395.
Cube ore, 461.
Emery, 395.
Cubicite, 422.
Emmonite, 376.
Cupreous anglesite, 486.
Epidote, 407.
Cupriferous sulphate of lead,
Epistilbite, 420.
486.
Epsomite, 392.
Cuproplumbite, 485.
Epsom salts, 392.
Cyanite, 400.
Eremite, 443.
Cymolite, 403.
Erinite, 403, 422, 506.
Cymophane, 441.
Brian, 405.
Cyprine, 406.
Erythrine, 466.
Esmarkite, 408.
DANAITE, 464.
Essonite, 405.
Danburite, 425.
Euchroite, 506.
Datholite, 438.
Euclase, 411.
Davidstouite, 411.
Eudyalite, 430.
Davyne, 416.
Eukairite, 497.
FAHLERZ, 499.
Fahlunite, 401, 409.
False topaz, 360.
Fassaite, 433.
Fat- stone, 416.
Faujasite, 421.
Feather alum, 398.
Feather ore, 476.
Felspar group, 412, 415.
Fergusonite, 393.
Ferro-tantalite, 458.
Ferruginous quartz, 360.
Fettbol, 402, 435, 460.
Fibro-ferrite, 461.
Fibrolite, 400.
Fichtelite, 358.
Fiorite, 366, t. 6.
Fire marble, 382, v. 4.
Fischerite, 396.
Flexible sulphuret of silver,
509.
Flint, 363.
Float stone, 363.
Flos ferri, 384.
Fluelite, 397.
Fluocerine, 443.
Fluor spar, 386.
Foliated tellurium, 473.
Fontainebleau sandstone,
379.
Fortification agate, 361.
Fossil copal, 358.
Franklinite, 452.
French chalk, 427.
Frugardite, 406.
Fuchsite, 437.
Fuller's earth, 403.
GABRONITE, 408.
Gadolinite, 393.
Gahnite, 441.
Galena, 485.
Gallizinite, 458.
Garnet, 404.
Garofian, 385.
Gay-lussite, 371.
Gedrite, 424.
Gehlenite, 408.
Gelatinous silex, 364.
Geokronite, 476, 485.
German silver, 467.
Giallo-antico, 381.
Gibbsite, 395.
Gieseckite, 409.
Gigantolite, 409.
Gilbertite, 401.
240
MINEEALOGY.
Gillingite, 452.
Girasol, 366, v. 2.
Gismondine, 421.
Glauber salts, 371.
Glaubertite, 371.
Glaucollte, 415.
Glottalite, 421.
Gmelenite, 422.
Gobhardite, 435.
Goekumite, 429.
Goethite, 454.
Gold, 512.
Grammatite, 431 .
Graphic gold, 473.
Graphic tellurium, 473.
Graphite, 352.
Green earth, 460.
Greenockite, 474.
Greenovite, 439.
Gregorite, 458.
Grey antimony, 476.
Grey cobalt, 464.
Grey copper ore, 499.
Groppite,401.
Grossularite, 405.
Guanite, 369.
Gummi-erz, 492.
Guyaquillite, 358.
Gypsum, 387.
HEMATITE, BROWN, 454.
Haematite, red, 453.
Haidingerite, 390, 476.
Halloylite, 403.
Halloysite, 403.
Harmotome, 422.
Harringtonite, 419.
Hartite, 358.
Hartshorn, 369.
Hatchetine, 358.
Hausmannite, 444.
Hauyne, 440.
Haydenite, 422.
Hayesine, 390.
Haytorite, 438.
Heavy spar, 375.
Hedenbergite, 433.
Hediphane, 488.
Heliotrope, 362.
Helvine, 441.
Hepatite, 375.
Herbeckite, 435, 460.
Herrerite, 473.
Herschelite, 422.
Heteroclin, 447.
Heterozite, 447.
Heulandite, 420.
Hisingerite, 435, 460.
Holmesite, 424.
Holmite, 424.
Hopeite, 472.
Hornblende, 431.
Horn cobalt, 465.
Horn manganese, 448.
Horn quicksilver, 481.
Horn silver, 511 .
Hornstone, 362, 431.
Hornstone, fusible, 413.
Humboldtilite, 416.
Humboldtite, 438, 461.
Hureaulite, 447.
Hyacinth, 430.
Hyalite, 366 v. 6.
Hyalosiderite, 429.
Hydrargylite, 395.
Hydroboracite, 391.
Hydrobucholzite, 401.
Hydrogen gas, 349.
Hydrolite, 422.
Hydrophane, 366 v. 4.
Hydropite, 448.
Hydrophite, 428.
Hypgrsthene,jt33j
Hypostliblte, 419.
ICELAND SPAR, 379.
Ice spar, 413.
Ice stone, 397.
Idocrase, 406.
Idrialine, 357.
Igloi'te, 384.
Ilmenite, 458.
Ilmenium, 483.
Ilvaite, 460.
Indianite, 415.
Indicolite, 438.
Indigo copper, 497.
lodic mercury, 481.
lodic silver, 511.
lolite, 409.
Iridium, 514.
Iron, 449.
Iron apatite, 447.
Iron glance, 453.
Iron ochre, 454.
Iron pyrites, 450.
Iron sinter, 461.
Iserine, 458.
Isophane, 452.
Itaberite, 453.
Ittnerite, 422.
Ixolite, 358.
JACOTINGA, 512.
Jade, 410, 431.
Jamesonite, 476.
Jargon, 430.
Jasper, 365.
Jeffersonite, 433.
Jenite, 460.
Jet, 354.
Johannite, 492.
Johnite, 397.
Junkerite, 455.
KAKOXENE, 459.
Kammererite, 422.
Kaolin, 402.
Karpholite, 422.
Kerolite, 422.
Killbrickenite, 476,485,
Killinite, 422.
King's yellow, 479.
Kirwanite, 422.
Klaprothine, 396.
Knebelite, 429.
KobeJlite, 476,486.
Koenigite, 504.
Kollyrite, 403.
Konlite, 358.
Koupholite, 421.
Krokidolite, 460.
Kupfer nickel, 468.
LABRADORITE, 415.
Lapis lazuli, 440.
Lapis ollaris, 426.
Latrobite^ie.
Laumontite, 421.
Lavenduline, 466.
Lazulite, 396, 440.
Lead, 484.
Lead glance, 485.
Leadhillite, 487.
Lederolite, 422.
Leelite, 413.
Lehuntite, 419.
Lenzinite, 403.
Leonhardite, 421.
Lepidokrokite, 454.
Lepidomelane, 424.
Lepidolite, 437.
Leucite, 416.
Leucolite, 416.
Leucophane, 437.
Leucopyrite, 451.
Levyne, 422.
Lherzolite, 433.
Libethenite, 506.
INDEX.
241
Lievrite, 460. 4
Mesitine spar, 455.
Neoplase, 461.
Lignite, 355.
Mesolite, 519.
Nepheline, 416.
Limbelite, 429.
Mesotype, 418.
Nephrite, 410.
Lime salts, 378, 390.
Metaxite, 428.
Newkirkite, 445.
Limonite, 454.
Meteorite, 449.
Nickel, 467.
Lincolnite, 420.
Miargyrite, 510.
Nickel glance, 468.
Lithomarge, 402.
Mica, 437.-
Nickel green, 468.
Liroconite, 506.
Micaceous iron, 453.
Nickeline, 468.
Loam, 402.
Michaelite, 364.
Nickel pyrites, 467.
Lodestone, 452.
Middletonite, 358.
Nickel stilbine, 468.
Lolingite, 451.
Miemite, 385.
Nigrine, 458.
Loxoclase, 414.
Milky quartz, 360.
Niobite, 458.
Lumachelle, 382 v. 4.
Millerite, 467.
Niobium, 483.
Lydian stone, 365.
Mimetine, 488.
Nitratine, 371.
Mineral caoutchouc, 357.
Nitre, 370.
MACLURITE, 437.
Mineral oil, 356.
Nontronite, 435, 460.
Madreporite, 379.
Mineral pitch, 356.
Nosean, 440.
Magnesian salts^ 391.
Minium, 486.
Nussierite, 488.
Magnesian limestone, 385.
Mispickel, 451.
Nuttalite, 408.
Magnesite, 391.
Misy, 461.
Magnetic iron ore, 452.
Mocha-stone, 361.
OBSIDIAN, 413.
Magnetic pyrites, 450.
Mohsite, 458.
Ochre, chromic, 462.
Magnetite, 452.
Molybdenite, 494.
Ochre, iron, 455.
Malachite, 503.
Molybdenum, 494.
Ochre, molybdic, 494.
Malacolite, white, 433.
Molybdic ochre, 494.
Ochre, red cobalt, 466.
Malacon, 430.
Monazite, 443.
Ochre, yellow, 454.
Malthacite, 364.
Moon-stone, 413.
Octahedral iron ore, 452.
Mancinite, 472.
Moroxite, 389.
Oerstedite, 430.
Mandelato, 381.
Morvenite, 422.
Oetite, 454, 456.
Manganese, 444.
Mosandrite, 439.
Okenite, 425.
Manganese blende, 444.
Moss agate, 361.
Oligist, 453.
Manganese spar, 448.
Mountain cork, 433.
Oligoclase. 415.
Manganite, 445.
Mountain leather, 433.
Oligon spar, 455.
Marble, 381.
Mountain meal, 383.
Olivine, 429.-*.
Marcasite, 450.
Mountain soap, 403.
Olivenite, 506.
Marceline, 447.
Mountain tallow, 358.
Onchosine, 422.
Marekanite, 413.
Mountain wood, 433.
Onyx, 361.
Margarite, 407.
Miiller's glass, 366, v. 6.
Oolite, 382, v. 3.
Margarodite, 438.
Mullicite, 459.
Oolitic iron ore, 454.
Marmatite, 470.
Mundic, 450.
Oosite, 409.
Martial pyrites, 450.
Martinsite, 371.
Murchisonite, 413.
Muria'cite, 388.
Opal, 366.
Ophite, 428.
Marti te, 454.
Musc6ide, 488.
Opsimose, 448.
Mascagnine, 369.
Muscovy glass, 437.
Orpiment, 479.
Massicot, 486.
Mussite, 433.
Orthite, 443.
Meerschaum, 391.
Mysorine, 503.
Orthoclase, 413.
Meionite, 408.
Orthose,413.
Melanite, 405.
NACRITE, 424.
Osmelite, 425.
Melanochroite, 488.
Nail-head spar, 379.
Osmiridium, 314.
Melinite, 416.
Naphtha, 356.
Osmium, 515.
Mellite, 398.
Natro-calcite, 377.
Ottrelite, 408.
Menaccanite, 439.
Natrolite, 419.
Ouralite, 433.
Menachanite, 458.
Natron, 371.
Ouwarovite, 405.
Mengite, 443, 458.
Necronite, 413.
Oxahverite, 425.
Menilite, 366, v. 7.
Nemalite, 391.
Oxalite, 461.
Mercury, 480.
Neoctese, 461.
Oxidulated iron ore, 452.
R
242
MINERALOGY.
Ozokerite, 358.
PALAGONITE, 408.
Palladium, 517.
Paranthine, 408.
Parasite, 443.
Pargasite, 431.
Paulite, 433.
Peach-blossom ore, 466.
Peacock ore, 498.
Pearl-mica, 408.
Pearl powder, 491.
Pearl spar, 385.
Pectolite, 425.
Pelocronite, 506.
Pelopium, 483.
Pennine, 423.
Periclase, 391.
Pericline, 414.
Peridote, 429.
Perowskite, 390.
Petalite, 415.
Petroleum, 356.
Petrosilex, 413.
Phacolite, 422.
Pharmacolite, 390, 477.
Pharrnacosiderite, 461.
Phenacite, 411.
Phillipsite, 422, 497.
Pholerite, 401.
Phonolite, 413.
Phosphori-calcite, 506.
Phosphorite, 389.
Phosphorus, 368.
Photozite, 448.
Phyllite, 431.
Piauzite, 358.
Pickeringite, 398.
Picnite, 436.
Picrolite, 428.
Picropharmacolite, 390.
Picrophyllite, 428.
Picrosmine, 428.
Pictite, 439.
Pimelite, 468.
Pinchbeck, 496.
Pinguinite, 416.
Pinguite, 435.
Finite, 409.
Piotine, 422.
Pisolite, 382, v. 3.
Pisolitic iron ore, 454.
Pissophane, 398.
Pistacite, 407.
Pitchblende, 492.
Pitchstone, 413.
Pittin-erz, 492.
Pittizite, 461.
Placodine, 468.
Plagionite, 476.
Platinum, 513.
Pleonaste, 441.
Plinthite, 402.
Plumbago, 352.
Plumbic ochre, 486.
Plumbo-calcite, 379.
Plumbo-resinite, 488.
Plumbostib, 485.
Polishing slate, 364.
Polyadelphite, 460.
Polybasite, 509.
Poly erase, 430.
Polyhydrite, 435.
Poly lite, 431.
Polymignite, 430.
Polysphaeride, 488.
Poonahlite, 419.
Porcelain clay, 402.
Potash salts, 370.
Potstone, 426.
Praseolite, 409.
Predazzite, 385.
Prehnite, 421.
Protheite, 406.
Proustite, 510.
Psilomelane, 447.
Pumice, 413.
Pyrallolite, 428.
Pyrargillite, 401.
Pyreneite, 405.
Pyrites, arsenical, 451.
Pyrites, capillary, 467.
Pyrites, copper, 498.
Pyrites, iron, 450.
Pyrites, magnetic, 450.
Pyrochlore, 390.
Pyrolusite, 446.
Pyromorphite, 488.
Pyrope, 405.
Pyrophyllite, 422.
Pyrophysalite, 436.
Pyrorthite, 443.
Pyrosclerite, 422.
Pyrosmalite, 460.
Pyroxene, 432.
Pyrrhite, 472.
QUARTZ, 359364.
Quartzite, 360.
Quincite, 391.
RADIOLITE, 419.
Randanite, 364.
Raphilite, 416.
Rapidolite, 408.
Ratofkite, 386.
Razoumoffskine, 403.
Realgar, 478.
Retin-asphalt, 358.
Red antimony, 476.
Red copper ore, 500.
Rensselaerite, 427.
Retinalite, 435.
Retinite, 358, 413.
Reussin, 392.
Rhodalite, 422.
Rhodium, 516.
Rhodizite, 391.
Rhodochrome, 428.
Rhodocrolite, 447.
Rhodonite, 448.
Rhaetizite, 400.
Rhomb spar, 385.
Riband agate, 361.
Ripidolite, 423.
Rock crystal, 360.
Rock milk, 383.
Rock salt, 371.
Romanzovite, 405.
Romeine, 390.
Roselite, 390, 466.
Rose quartz, 360.
Rosite, 401.
Rosso-antico, 381.
Rothoffite, 405.
Rubellane,437.
Rubellite, 438.
Rubin-glimmer, 454.
Rubicelle, 442.
Ruby, oriental, 395.
Ruby silver, 510.
Ruin-agate, 361.
Russite, 371.
Rutile, 482.
Ryacolite, 413.
SAHLITE, 433.
Sal ammoniac, 369.
Salmiac, 369.
Sal volatile, 369.
Saltpetre, 370.
Samarskite, 492.
Saponite, 422.
Sapparite, 400.
Sapphire, 394.
Sarcolite, 416.
Sard, 362.
Satin-spar, 380, 387.
INDEX.
243
Saussurite, 415.
Scapolite, 408.
Schaura-erde, 379.
Scheelite, 390,
Scheererite, 358.
Schiefer spar, 379.
Schilfglaserz, 509.
Schiller asbestus, 428.
Schiller spar, 435.
Schorl, 438.
Schrotterite, 403.
Scolexerose, 408, 415.
Scolezite, 419.
Scorodite, 461.
Scorza, 407.
Scoulerite, 422.
Selen-sulphur, 368.
Selenid of copper, 497.
Selenite, 387.
Selenium, 30'8.
Seleniuret of silver, 510.
Semeline, 439.
Serpentine, 428.
Seybertite, 424,
Siderite, 455.
Sideroschizolite. 435, 460.
Silicates, 399.
Silicite, 415.
Silicium, 359.
Sillimanite, 400.
Silver, 507.
Sinter, 366 v. 11.
Sismondite, 424.
Slate spar, 379.
Smalt, 463.
Smaltine, 464.
Smaragdite, 435.
Smelite, 401.
Smoky quartz, 360.
Soapstone, 422, 427.
Soda salts, 371.
Sodalite, 416.
Somervillite, 416.
Sordawalite, 410.
Sparry iron, 455.
Spathic iron, 455,
Spathose iron, 455.
Specular iron ore, 453.
Speculum metal, 496.
Spessartine, 405.
Sphairosiderite, 455.
Sphaerostilbite, 419.
Sphene, 439, 482.
Spinellane, 440.
Spinelle, 441.
Splint coal, 354.
Spodumene, 415.
Stalactite, 380.
Stalagmite, 380.
Staurolite, 400.
Staurotide, 400.
Steatite, 427.
Steinheilite, 409.
Steinmannite, 476, 485.
Steinmark, 400.
Stellite, 422.
Sternbergite, 509.
Stilbite, 419,475.
Stilpnomelane, 435, 460.
Stilpnosiderite, 454.
Strahlstein, 431.
Stream tin, 490.
Stroganowite, 416.
Stromeyrine, 497.
Strom nite, 376.
Strontia salts, 376, 377.
Strontianite, 376.
Struvite, 369.
Stylobite, 408.
Succinite, 405.
Sulphur, 367.
Sulphuretted hydrogen,349.
Sylvine, 370.
Symplesite, 461.
TABASHEER, 366, v. 10.
Tabular quartz, 363.
Tabular spar, 425.
Talc, 426.
Tantalite, 458.
Tantalum, 483.
Tautolite, 429.
Tellurid of lead, 485.
Tellurium, 473.
Tennantite, 499.
Tenorite, 501.
Tephroite, 472.
Tesselite, 425.
Tetartine, 414.
Tetradymite, 491.
Thallite, 407.
Tharandite, 385.
Thenardite, 371.
Thomaite, 455.
Thomsonite, 422.
Thorite, 393, 430.
Thraulite, 435.
Thulite, 407.
Thumite, 438.
Tile ore, 500.
Tin, 459.
Tin oxide, 490.
Tin pyrites, 489.
Tin-white cobalt, 460.
Tincal, 372.
Titaniferous sand, 458.
Titanate, 439.
Titanium, 482.
Toad's eye tin, 490.
Tombac, 496.
Tombazite, 468.
Topaz, 436.
Topaz oriental, 395.
Topazolite, 405.
Touchstone, 365.
Tourmaline, 438.
Tremolite, 431.
Triclasite, 409.
Triklasite, 401.
Triphane, 415.
Triphylline, 447.
Triplite, 447.
Tripoli, 364.
Trombolite, 506.
Trona, 371.
Troolite, 448.
Troostite, 448.
Tschewkinite, 443.
Tuesite, 403.
Tungsten, 493.
Tungstic acid, 493.
Turgite, 454.
Turnerite, 441.
Turquoise, 397.
Tutenague, 467.
Type metal, 475.
ULTRA MARINE, 440.
Uran vitriol, 492.
Uranic ochre, 492.
Uranite, 492.
Uranium, 492.
Uranotantalite, 492.
Urao, 371.
VANADINITE, 488, 495.
Vanadium, 495.
Variscite, 397.
Varvacite, 445.
Vauquelinite, 488.
Velvet copper ore, 504.
Venice white, 487.
Verd-antique, 381.
Vermiculite, 422.
Verona earth, 435, 460.
Vesuvian, 406.
Vesuvian garnet, 416.
Villarsite, 429.
244
MINERALOGY.
Violane, 407.
Vitreous copper ore, 497.
Vitreous silver, 508.
Vitriol, blue, 505.
Vivianite, 459.
Volborthite, 506.
Volcanic ash, 413.
Volcanic glass, 413.
Volzine, 470.
Vulpinite, 388.
WAD, 446.
Wagnerite, 391.
Wanvickite, 482.
Washingtonite, 458.
Water, 349.
Water sapphire, 409.
Wavellite, 396.
Websterite, 398.
Wehrlite, 460.
Weissgiiltigerz, 485.
Weissite, 409.
Wernerite, 408.
White antimony, 476.
White arsenic, 477.
White iron pyrites, 450.
White lead ore, 487.
White nickel, 468.
White silver, 476.
White tungsten, 390.
White wolfram, 390.
Wichtine, 424.
Wfflemite, 472.
Withamite, 407.
Witherite, 374.
Wilnite, 405.
Wiloschine, 462.
Wohlerite, 430.
Wolchonskite, 462.
Wolfram, 458.
Wollastonite, 425.
Wood-coal, 355.
Wood-opal, 366, v. 8.
Wood-tin, 490.
Worthite, 401.
XANTHITE, 406.
Xanthophyllite, 424.
Xenotime, 393.
Xylite, 435, 460.
YANOLITE, 438.
Yellow ochre, 454.
Yenite, 460.
Ypoleine, 506.
Yttria salts, 393.
Yttrocerite, 393.
Yttrotantalite, 393.
ZAFFRE, 463.
Zeagonite, 421.
Zeolites, 417.
Zeuxite, 433.
Ziegel-erz, 500.
Zinc, 469.
Zinc-bloom, 471.
Zinkenite, 476.
Zircon, 430.
Zoisite, 407.
PART III.
DESCRIPTIVE GEOLOGY.
CHAPTER XL
OX THE NATURE OF ROCKS, THE MODE OF THEIR ORIGINAL
AGGREGATION AND SUBSEQUENT METAMORPHOSIS, AND THE
DIFFERENT KINDS OF ROCKS THAT ARE FOUND NEAR THE
EARTH'S SURFACE.
518. BY the term rock, in Geology, is understood any aggregation
of minerals, or fragments of minerals whether crystalline or amor-
phous, hard or soft, compact or loose, forming now an essential part
of the mass of matter subject to our observation near the earth's sur-
face. Rocks may, therefore, be mere mechanical heaps, presenting no
structure, and nothing from which their history can be traced ; or
they may be mechanical heaps arranged so that we can readily dis- .
cover the law of their formation ; or finally, they may be so far mo-
dified by some re-arrangement of particles the result of chemical
action that the history they present is that of subsequent change,
more or less obscuring the evidence of original formation. The vast
majority of examples are of the latter kind, and are often very diffi-
cult to comprehend, since few rocks are without marks of some action
which has changed them from their original condition, and to deter-
mine how far this alteration is the result of desiccation, pressure, the
attraction of cohesion, or time ; and how much of it is due to chemi-
cal causation ; has rarely been determined by geologists, and has formed
but a small part of the objects of chemical investigation. In this
chapter an attempt will be made to lay before the student an account
of the actual condition of various rocks ; but in doing so it will be
necessary to introduce some views of the nature of such rocks which
are not quite in accordance with those commonly entertained. With-
out, however, pledging the student to any opinions on the theoretical
246 DESCRIPTIVE GEOLOGY.
part of the subject, it is very desirable that attention should be di-
rected to such investigations, as having direct reference to the most
pressing and important department of practical, as well as scientific,
geology.
519. Rocks may be regarded in two ways, either as derived from
certain crystalline masses, such as granite, presumed to be part of the
original oxidized film of the earth before it became affected by at-
mospheric or aqueous agency, and thence called Primitive, Endoge-
nous, or by other similar and significant names ; or, as mineral
substances accumulated at first in a manner more mechanical than
chemical, and afterwards changed, by the action of chemical force,
into the condition in which we now find them. The former view in-
volves the idea that a large part of the surface has undergone little
change, and that masses of rock remain, for an indefinite period of
time, in a state of permanent equilibrium, so far as their internal and
molecular arrangement is concerned. The latter view, without as-
suming that changes have really taken place in these respects, admits
the possibility of their occurrence ; and as it teaches us to proceed
from the known to the unknown, and requires no statement of theory
at starting, we shall here endeavour to carry the reader along, step
by step, by its assistance, commencing with phenomena that we can
explain distinctly, and advancing gradually to those concerning which
we can only speculate.
520. The essential minerals in all natural combinations on a large
scale, are Quartz, Limestone, Clay, and Water ; and we must refer
to the paragraphs where the three former have been described as
minerals, for an account of their important chemical arid mineralo-
gical characteristics. We have, however, now to consider them in a
somewhat different point of view, as amorphous masses, compounded
generally of several substances, and admitting of many varieties of
appearance and structure. In this form they abound everywhere,
while the crystalline forms, unmixed with other substances, are so
little abundant that we may safely regard them as rare exceptions to
the general rule. The common varieties, the common associations,
and the common modifications, are the materials for the geologist ;
and he often puts aside the crystalline mineral as an object of in-
terest quite distinct from, and subordinate to, the amorphous, massive,
or semi-crystalline rock. It must not, however, be concluded that
the crystal and the mineral species are useless even to the geologist,
for they often afford good evidence of change having taken place in
the whole mass ; and with such evidence it is of the greatest import-
ance that he should be acquainted,
521. While the great mass of all rocks is made up of quartz, lime-
stone, or clay, or admixtures of these, there are many other substances
whose presence is not less invariable ; although the proportion they
ESSENTIAL INGREDIENTS OF ROCKS. 247
bear in point of actual quantity is often extremely small. Such in-
gredients may be regarded as of two kinds those which are essential
in giving to the various rock masses either their character of useful-
ness, or the marks by which they may be distinguished ; and those
whose presence is not easily recognised owing to the small proportion
in which they exist, or which, if found, are not known to have any
useful properties under the circumstances in which they appear.
Among the first group Iron is the most remarkable, giving colour to
almost every natural substance, and performing many parts in nature
of infinite importance. The bases of various alkaline earths, and
chiefly the salts of potash and soda, may be mentioned as present to
almost equal extent and in nearly the same way. Carbon, Magnesia,
Sulphur, and Phosphorus, among the solids ; and Chlorine and Nitro-
gen among gases, complete the list of substances of this nature.
522. Of elements widely distributed, but whose value and necessity
are not so manifest, Manganese, Gold, Arsenic, and Titanium, are well
known metals : and Fluorine, Iodine, and Lithia, other substances also
widely spread. Some of these, as gold, are of great value when ob-
tained in sufficient quantity ; but in the proportion in which they are
found in most rocks, the cost of extraction would be very much more
considerable than the value of the produce. Others, as Titanium,
have no known value. We may regard the substances thus widely
but not abundantly distributed, as more important in modifying
than in forming rocks ; and it is clear that when there is any possi-
bility for chemical action to take place, the materials at first accu-
mulated independently of each other, will soon begin to act on each
other, and may in many cases produce combinations totally unlike
those originally constituted.
523. We learn from the investigations of modern chemists, that
j ' new combinations may take place in solid bodies, without either sub-
stance being in a state of absolute fusion, or of aqueous solution. The
passage of an electric current through moist clay, tends to produce an
entire re-arrangement of the particles of the mass, giving to the whole
a lamination which the original did not possess, and which has no re-
ference to any original lamination of the mass itself ; and also sepa-
rating certain impurities, and collecting them into simple minerals
in some crevice or cavity.
Amongst the evidence of this kind to which we can directly refer is that of Mr
Robert Were Fox. This gentleman submitted a mass of moist clay worked up with
acidulated water, to weak voltaic action for some months ; and it was found at the
end of that time^ to exhibit when dry a rude laminated structure, the planes of the
laminae being at right angles to the electric forces. Mr. Hunt has also made experi-
ments, extending these investigations to other substances .with similar results.*
Besides this direct evidence with regard to rocks, there have also been observations
* Mem. of Geol. Survey of Great Britain, vol. i. p. 451, and vol. ii. p. 631.
248 DESCRIPTIVE GEOLOGY.
made by some distinguished chemists which, so far as they go, illustrate the same
principle. Thus M. Mitscherlich, in experimenting on the sulphates of lime and other
substances, found prismatic crystals of nickel distinctly modified, and the internal
arrangement of the atoms changed, by a few days' exposure to the sun's rays, without
the exterior being affected ; and Sir H. de la Beche has well observed in quoting this
experiment, " When acquainted with these and other facts of the same kind, we are
led to suppose that rocks may not only become visibly altered by the long-continued
action of diminished or increased heat upon them, but that they may also have their
various parts differently arranged, as to mutual attraction, without the general appear-
ance of the rock being sensibly changed."* The same author adds, in another place,
" Crystals of sulphate of zinc and sulphate of magnesia, gradually heated in alcohol,
lose their transparency, and are found composed of numerous small crystals, differing
in form from those used in the experiment." Mitscherlich has observed that the
optical properties of plates of sulphate of lime and other substances were altered by
changes of temperature ; showing an alteration in the interior structure while no
sensible exterior modification could be observed in the plates. The various temper-
ing of steel and the annealing of glass, must also arise from new arrangements of the
particles of steel and glass caused by heat insufficient to produce fusion. If we take
a piece of common green bottle-glass and expose it to continued heat, insufficient
to cause fusion, we obtain a crystalline substance composed of numerous prisms ar-
ranged at right angles to the surfaces of the glass, the external form of which remains
unaltered, notwithstanding the new arrangement of the internal particles.
524. Among the mineral substances present in most rocks in very
small quantity, a considerable number are the same as those which
are also found in organic bodies either animal or vegetable. We
must in all cases suppose that the elements were originally obtained
in some way from the mineral kingdom, but the reaction of the or-
ganic on the inorganic world has manifestly gone on so long as to
render it very difficult to determine in each particular rock, whether
certain substances present are, or are not, proximately due to organic
causes. To give a single and familiar instance of the exact meaning
of this, let us refer to such accumulations of coal as are now well
known and universally admitted to be of vegetable origin. These
consist chiefly of carbon, and the carbon thus obtained must have
been derived either directly or indirectly from the mineral kingdom,
although now so far as its origin can be traced, it partly exhibits or-
ganic structure, and is partly restored to what must be regarded as
an inorganic state. So in other cases the accumulations of shells of
marine animals, consisting of carbonate of lime, although inorganic
so far as the present form of their existence is concerned, are clearly
due to organic causation ; and so again the infusorial mud found
embedded near the mouths of rivers, is an inorganic product due to the
secretions of organic beings. It is, however, difficult to draw the line
between that which is and that which has been organic.
525. As long as by direct evidence of any kind we can trace actual
organization, as in the ashes of coal, the shape of a sea-shell or coral,
or the siliceous skeleton of an animalcule, there is no difficulty in de-
termining how these substances were introduced, and this is especially
* De la Beche 's "Theoretical Researches," p. 106.
DIFFERENT KINDS OF ROCKS. 249
the case when the materials form part of regular beds, amongst which
it is easy to suppose organic remains would be found. Thus in the
mud, sand or silt of rivers, or in the accumulations of broken mate-
rial near a coast, no one would be surprised to find twigs, leaves,
broken shells, fishes teeth, and other matters of the kind ; but when
we discover, as has been lately done, that the remains of animals re-
sembling those inhabiting the land and fresh-water are thrown up
into the air, as volcanic products, from islands without fresh-water in
the middle of a great ocean, some astonishment may well be felt,
although the fact seems equally beyond question. When, however,
salts of potash and soda, together with phosphorus, carbonate of lime,
and other substances, are the only evidences of the former existence
of animals "and vegetables, it is by no means an easy matter to decide
how far the presence of a certain excess of minerals, usually or always
rare, is indicative of organic origin, or refers to a condition of the
earth before animals and vegetables existed on its surface.
526. Geologists have generally agreed to speak of the various rocks
presented to their notice, as separable into three groups. These have
been named respectively, MECHANICAL, METAMORPHIC, and CRYSTAL-
LINE ; or AQUEOUS, METAMORPHIC and IGNEOUS : the term Metamor-
phic indicating an intermediate state not very distinctly limited in
its meaning. The Mechanical or aqueous rocks are understood to
include all the ordinary sandstones, limestones, and clays, or mixtures
of these, which appear to have been deposited from water, and which
show lamination, or as it is called, stratification : and on the other
hand, the Crystalline or igneous group comprehends certain mineral
masses, of which granite is a familiar example, which are found in
many districts, and in which marks of mechanical deposit cannot ge-
nerally be traced. We shall have to recur frequently to these terms,
which are too firmly rooted in the scientific language of the day to be
neglected or disturbed ; but as, in fact, there is hardly one of the infi-
nite variety of accumulations of mineral matter at the earth's surface
which is not metamorphic in the strict sense of that term, we do not
willingly admit a distinction which is certainly not of Nature's making.
The only way in which we can obtain a satisfactory notion of the
different groups of rocks seems to be by referring each, as far as pos-
sible, to its origin as a mechanical aggregate, and then tracing the
various transformations or metamorphoses which each may undergo
when exposed to such chemical action as we can fairly assume. This
mode of treatment has at least the advantage of distinctness, and the
student will thus see as he advances the bearings of the subject, and
also recognise its weak points as well as its strength.
An idea will at the same time be communicated of the influence of
organic products, and of the use of their study in the higher problems
of Geology altogether distinct from that usually afforded, which has
250 DESCRIPTIVE GEOLOGY.
reference only to the determination of the relative date of formation
of certain similar mineral masses.
It is not difficult to recognise three divisions, to some one of which
a very large number of rocks may be referred ; these divisions having
reference to the mineral ingredient which forms the characteristic in
each case. We may call them, the sand group, the lime group, and
the clay group respectively, and we purposely avoid any more accu-
rate definition at present, in order that they may be more readily
understood and more generally inclusive. We will now mention the
principal conditions occurring in each of them, in the order of their
occurrence in nature, so far as we can trace it.
The Sand Group.
527. The simplest mechanical condition of the rocks referred to
this group is that of fine white sand, the particles being small, of uni-
form size, and consisting of nearly pure quartz. Such material is
not unfrequently seen by the sea-side, and it is there found to be
absorbent of water, becoming then compact and even hard, admitting
readily of impressions upon its surface, and retaining them for some
time. Such material also occurs not unfrequently alternating with
clays, and if met with in sinking a shaft or making a cutting, readily
gives out the water it contains, and, from its loose texture, is soon
removed. It is then called quick-sand.
If we take up an ordinary piece of white sandstone, and compare
it with this loose sand, some differences will be recognised, and we
thus are introduced to the first and simplest modification of a rock.
The particles of sand have now been consolidated, and a texture is
observable which may be fine or coarse according to the size of the com-
ponent particles, and loose or compact according to the way in which
it has become solidified. The process of consolidation thus induced
may be merely the result of the force of cohesion, for no doubt the
continued contact of the particles under heavy pressure may produce
such change ; but the infiltration of water containing the small quan-
tity of silica usually present in sea- water, or of a little clay, lime, or
iron, also found there in small quantities, is often the immediate
cause of this consolidation, while a little carbon or bitumen frequently
points to organic agency.
528. Loose sand exposed for a long time to great heat without
pressure, as at the bottom of a furnace, will sometimes consolidate
and form a compact and very durable but brittle stone. It is diffi-
cult generally to avoid the presence of a small quantity of alkaline
earth, which serves as a flux; but examples have been often ob-
tained of pure sand forming into a loose rock with a coarsely
columnar structure. This seems to be a first approach to crys-
tallization, and is generally assumed by rock masses when circum-
SAND-ROCKS.
stances are favourable, that is, when they have long been exposed
to uniform conditions of pressure and temperature ; a high tempera-
ture not being required.
An interesting example of the effect of continued heat upon the sand made use of to
line the inside of a reverberatory furnace has fallen under the author's observation, a
specimen having been sent to King's College for examination. The sandy floor was
originally of perfectly loose texture and of a deep red colour (owing to the presence
of oxide of iron). Its thickness amounted to several inches. After having been for
about a fortnight at the bottom of the furnace, the part nearest the fire became of a
black colour and a loose scoriaceous texture, but at a very little depth the scoriaceous
appearance ceased, and there was found a considerable thickness of compact, close-
grained sandstone without colour, exhibiting a distinctly columnar structure. Below
this the sandstone gradually passed again into loose red sand as the effect of the heat
had been less felt.
529. The most compact form of sand rock is that denominated
quartz rock, or quartzite. We quote the following account of its ge-
neral characters from Dr. Macculloch. " It is occasionally, but rarely,
found in a compact state and crystalline throughout ; little differing
from quartz as it occurs in veins ; but even in these cases showing a
constant tendency to divide in parallel beds. More generally, when
pure, it has an aspect obscurely granular, which by degrees becomes
somewhat lax and arenaceous ; the grains varying in size and in the
intimacy of their union. In some of these examples, it appears to
be a granular crystallized mass ; in others, it possesses a mixed me-
chanical and chemical texture ; while, in a third, the rounded aspect
of the grains, and the small number of the points of contact, appear
to indicate an origin chiefly mechanical, and resulting from the ag-
glutination of sand. These are its varieties when in the purest state,
and, I may add, that cavities are sometimes found in the specimens,
containing regular although minute crystals."*
The rock thus characterized is considered as primitive, but from
the account given and the specimens usually obtained, it appears that
the transition from the granular to the crystalline state is so gradual
as to justify the idea that the one is but an altered form of the other.
530. Beside these three varieties of pure sand rock, there are,
however, innumerable others presented in nature, where the sand is
associated with clay, calcareous matter, iron, manganese, and other
impurities. We append analyses of some well-marked instances from
building materials used in England. (See TABLE I.)
In the subjoined table, the stones referred to may be described as follows :
1. The Craigleith stone, from near Edinburgh, is a whitish grey stone with siliceous
cement, slightly calcareous, with occasional plates of mica. 2. The Darley Dale stone,
from near Bakewell, is of light ferruginous brown colour, has an argillo-siliceous
cement, contains decomposed felspar with plates of mica, and has irony spots. 3. The
Heddon stone, from near Newcastle-on-Tyne, is of light brown ochrey colour, and is
similar in composition to that from Darley Dale, with the exception of the plates of
" Western Islands of Scotland," vol. ii. p. 221.
252
DESCRIPTIVE GEOLOGY.
mica. 4. The Kenton, from the same district, is also of light irony brown colour, and
contains mica in the planes of bedding. It has an argillo-siliceous and ferruginous
cement. 5. The Mansfield stone (Nottinghamshire) has a rosy brown colour and a
magnesio-calcareous cement.*
TABLE I.
ANALYSES OF SANDSTONES.
Constituent minerals.
1.
Craigleith,
SG=2'232.
2.
Darley
Dale,
SG = 2'628.
3.
Heddon,
SG=2-22Q.
4.
Kenton,
SG=2'24/.
5.
Mansfield,
SG=2'338.
Silica
98-30
96-40
95-10
93'10
49-40
1-10
0-36
0'80
2-00
26-50
Carbonate of magnesia. .
Iron alumina
0-00
60
o-oo
1-30
o-oo
2-30
o-oo
4-40
16-10
320
\Yater and loss . . .
o-oo
1-94
1-80
0-50
4-80
100 '00
100-00
100-00
100.00
100-00
531. The chief varieties of sandstone rocks are, \&i. fine-grained
sandstones, more or less adapted for building purposes ; 2nd. flag-
stones or laminated sandstones, which are sometimes even flexible,
and are chiefly used in paving, though sometimes for coarse roofing ;
3rd. grit-stones or fine conglomerates, in which quartz pebbles, usu-
ally small, are associated with smaller grains, and cemented together
into a hard mass, often used in the manufacture of mill-stones ; and
4th. coarse conglomerates or pudding-stones, of which examples are
not rare, but which are seldom available for any useful purpose.
They all occur in most parts of the world, and are almost all more
or less coloured by iron. They are little affected by acids, and
usually stand exposure well, but they are often associated intimately
with other sandstone rocks much less pure ; and if these impurities
consist of carbonates or sulphates of lime, or contain potash or soda,
the rock is apt to lose its valuable and durable character, and is
exposed to injury from disintegration.
532. Besides being used for building, the fine white sands, when
pure, are valuable in the foundry, in the manufacture of glass, and
in sawing marble and other stones. The fine hard kinds are used as
whetstones and scythe-stones, and a peculiar quartzose conglomerate,
called itacolumite, found io Brazil, is the matrix of the topaz and
some other gems, while a similar, but peculiar, siliceous grit in India
contains diamonds. *
In quartzose rocks, and in the crevices in such rocks, are found
many valuable metals, of which gold and platinum are the most
remarkable. Iron is also widely distributed through them, and
crystals of titanium often penetrate massive quartz as well as quartz
crystals. Garnets often occur in quartz rock.
* Report of Committee on Building Stones.
LIME-ROCKS. 253
533. Of the fragments of quartz rock and of the harder sand-
stones are formed many of the beds of gravel common in various
parts of the world, which appear to be deposits left behind by moving
water, and originally derived from the breaking up and wearing away
of much larger masses. Except when a little oxide of iron or carbo-
nate of lime has served as an imperfect cement, such gravel has rarely
undergone any true consolidation ; and thus we have in it an exam-
ple of siliceous rock in a very irregular and confused state, Blocks
of other kinds of stone not unfrequently appear in it.
534. Quartz rock, and siliceous accumulations of all kinds, are
usually very barren of organic remains a fact easily explained,
when we consider their origin, since gravel and sands are not those
places where marine animals chiefly inhabit, and any materials of
organic origin conveyed to such places would be exposed to much
injury from mechanical attrition. The soluble salts and other
mineral ingredients of organic beings might, however, in many cases
become collected in the vicinity of siliceous aggregations, and perhaps
under various conditions tend to modify the rock. This is especially
the case with seaweeds, which have in some instances been present
in great abundance, and of which indications are found in the che-
mical composition of the enclosing rocks, and animal bitumen is
also sometimes found in sand and quartz rock to a very remarkable
extent.
The Lime Group.
535. A piece of soft chalk, or the soft calcareous mud produced
from the rubbing and pounding of limestone by a river or the sea,
presents to us the best and simplest example of calcareous rock in its
first stage. It consists of nearly pure carbonate of lime, combined,
however, with a small proportion of silica. When from calcareous
mud a portion of the water is evaporated, a certain amount of solidi-
fication is produced, and we see before us a mineral into which water
is readily absorbed, and which, if exposed to the action of heat
under considerable pressure, assumes a hard and compact texture,
becoming either chalk, limestone, or marble ; but it is rarely that
calcareous rock occurs in nature in a simple and pure state, even
crystalline masses often containing foreign substances. Among them
silica is perhaps the most universal, while magnesia, and to a smaller
extent, potash, soda, iron, manganese, and even phosphorus and
fluorine, may be mentioned as extremely common.
Limestones, moderately solidified and tolerably pure, are either
finely granular, like the harder varieties of chalk, or else approximate
to the condition of what we may call earthy marble, examples of
which are abundant in the south of France and the north of Italy,
254 DESCRIPTIVE GEOLOGY.
and are well adapted for building purposes. They are extremely
compact and of close texture, and often show a conchoidal fracture
when broken. They are hard, white or cream-coloured, and contain
few of the fragments of animal substances present during their
formation. They have undergone, apparently, the same change as
the finer white sandstones, exhibiting the result of a simple expo-
sure to the action of the laws of cohesion under favourable circum-
stances.
536. Few, however of the common limestones of any country are
so nearly simple in their composition, and very few indeed, if any,
fail to exhibit in some way or other marks of an origin which has
some reference to organic beings. When we consider for a moment
the vast quantity of carbonate of lime which is daily and hourly
being separated to form the solid parts of animals, and remember
that this operation goes on in the depths of the ocean, and on its
shores, to a far greater degree than is possible on shore that every
race of molluscs, crustaceans, and zoophytes, inhabiting shells or
building coral reefs, or other stony skeletons and dwelling-places,
secretes a quantity of this material, which is obtained from the sea-
water, and rendered permanent in a solid form : when we remember,
too, that the quantity secreted by each individual during its brief
existence is almost always greater in proportion as the animal is
smaller, and its life shorter, and that at the same time the number
of individuals is then largest and the multiplication of the species
most rapid, little astonishment will be felt at the vast accumulations
thus made in the course of years, or the result thus produced upon
the mass of solid matter in the earth's crust.
The composition of limestones, even of those that exhibit no
organic bodies, corresponds so nearly to that of the solid matter
secreted by animals, and it is so difficult to understand the deposit
and formation of carbonate of lime without some such means, that
most naturalists have admitted, as highly probable, the suggestion
that all rocks of the kind, exhibiting mechanical structure, or afford-
ing organic remains, are partly, if not entirely, of organic origin.
Whether some of those that exhibit even the greatest amount of
crystalline structure, may not be of the same kind, we shall presently
consider. We have not here taken into account the deposits of
travertin and stalactite from fresh water, as these are never exhi-
bited on a very large scale, and do not affect the general question.
537. Referring to an estimate in a former paragraph ( 44), we
find that the total weight of carbonate of lime in solution in salt
water may be roughly estimated at about 400 millions of millions
of tons. This would correspond to more than 2,000,000 of tons of
carbonate of lime in each square mile of ocean, allowing a mean
depth of 1000 feet, and this quantity no doubt is restored as fast as
LIME-ROCKS. 255
it is removed, being dissolved by the water where the waves beat
against limestone rocks in various parts of the world. It must also
be amply sufficient for the supply of all the marine animals, since
it is probable that only a part of the solid matter secreted becomes
permanently included in rock masses, and even this part is most
abundantly secreted near shore.
538. The modifications of limestone are abundantly distributed,
and are many of them very valuable. The principal are, Oolites ;
Compact limestones, more or less crystalline ; Limestones that may be
called Massive marbles; and innumerable varieties of Crystalline
marble. Other kinds are present only in comparatively small quan-
tities and in particular districts, but these are very widely spread,
and appear under different names in every district, the degree and
nature of the modification varying almost indefinitely.
Oolite is the name given to limestones made up more or less com-
pletely of minute egg-shaped particles (whence the name), generally
concentric, and often consisting of calcareous matter accumulated
about some minute point of organic origin. Many of the common
building stones of England, especially those from the neighbourhood
of Bath, Portland Island, Ketton, and others, are of this kind, and
analyses of a few of the more important will be found useful. Some
of these are given in TABLE II. ; and we may here remark that the
first set, No. 1 to 6 inclusive, give the composition of the residuum,
and are therefore more detailed than the others. These are copied
from the " Memoirs of the Geological Survey of Great Britain," vol.
ii. pt. ii. p. 685. The rest are from the " Report on Building Stones
for the new Houses of Parliament," and were made under the super-
intendance of the late Professor Daniell.
539. Compact limestones and massive marbles are frequently so
far altered from their original condition as to have acquired a dis-
tinct and semi-crystalline texture, a fine grain, and a more or less
jointed or crystalline structure. They are often coloured by me-
tallic oxides, of which those of iron are by far the most abundant;
they constantly exhibit organic remains, of which corals and shells
are the most common ; and they almost always abound in small
crevices, which may perhaps be the result of contraction owing to
the removal of a portion of the water they once contained. These
crevices not unfrequently contain crystals of pure carbonate of lime.
Caverns are very common in limestone rocks.
Compact limestones pass by insensible degrees into true crystalline
marbles, of which the finest examples are obtained from Italy and
Greece, but which are not wanting in other districts. We append,
as a useful note to this part of the subject, another extract from the
work of Dr. Macculloch already quoted :
540. Speaking of "primary limestone," the name sometimes given
258
DESCRIPTIVE GEOLOGY.
PQ
VARIETIES OF MARBLE. 257
to the variety we are now considering, he says, " It exists, either in
a considerable succession of unmixed beds, or else in rare and slender
strata, or laminae intermixed in small proportion with some other
rock ; most frequently, with the argillaceous schists. It is also
found in irregular masses or large nodules, which can scarcely be
said to possess a stratified shape, and which very much resemble, as
already remarked, the masses of serpentine that occur in similar situ-
ations. Excepting in the crystalline form it is never found in veins,
and in this respect it is exactly analogous to quartz, the veins of
which are very similar and generally found in the same situations.
"Beds of limestone are often bent, and even considerably con-
torted, as are those of the rocks which it accompanies ; and these
flexures are most visible in the varieties which contain mica. They
seem to present no variations of structure but the laminar, which
are deserving of notice.
" The texture varies from the highly crystalline, of a larger or finer
grain, to the uniformly compact, and the earthy ; and the mineral
composition requires no notice, as it is fundamentally a simple rock.
It is, however, much modified in aspect by the presence of unessen-
tial minerals."*
541. We conclude this description of lime rocks with an account of some of the
more remarkable varieties of marble, chiefly from Dana's " Manual of Mineralogy."
It necessarily includes some combinations that we shall afterwards again mention,
and also some referred to in a previous paragraph as minerals :
" Verd antique marble Verde antico is a clouded green marble, consisting of a
mixture of serpentine and limestone. A marble of this kind occurs at Genoa and in
Tuscany, and is much valued for its beauty. A variety is called Polzivera di Genoa^
and Vert d'Egypte.
" The Cipolin marbles of Italy are white, or nearly so, with shadings or zones of
green talc. The Cardiglio is a grey variety from Corsica.
" Compact limestone usually breaks easily into thick slabs, and is a convenient
and durable stone for building and all kinds of stone work. It is not possessed of
much beauty in the rough state. When polished it constitutes a variety of marbles
according to the colour ; the shades are very numerous, from white, cream and yellow
shades, through grey, dove-coloured, slate-blue or brown, to black.
" The Nero-untico marble of the Italians is an ancient, deep black, marble ; the
Paragone is a modern one, of a fine black colour, from Bergamo; and Panno di morte
is anpther black marble with a few white fossil shells.
" The Rosso-antico is deep blood-red, sprinkled with minute white dots. The Giallo
antico, or yellow antique marble, is deep yellow with black or yellow rings. A beau-
tiful marble from Sienna, Brocatello di Siena, has a yellow colour with large irregular
spots and veins of bluish-red or purplish. The Mandelato of the Italians is a light
red marble, with yellowish-white spots ; it is found at Luggezzand. At Verona,
there is a red marble, inclining to yellow, and another with large white spots in a red-
dish and greenish paste. The Bristol marble is a black marble, containing a few
white shells, and the Kilkenny is another similar kind.
" The Portor is a Genoese marble, very highly esteemed. It is deep black, with
elegant veinings of yellow. The most beautiful comes from Porto- Venese, and under
* Macculloch's " Classification of Rocks," p. 365.
258 DESCRIPTIVE GEOLOGY.
Louis XIV. a great deal of it was worked up for the decoration of Versailles. Ruin-
marble is a yellowish marble, with brownish shadings or lines, arranged so as to re-
present castles, towers, or cities in ruins. These markings proceed from infiltrated
iron or manganese. It is an indurated calcareous marl.
" Oolitic raarWehas usually a greyish tint, and is speckled with rounded dots, look-
ing much like the roe of a fish. Shell marble contains scattered fossils, and may be
of different colours. Crinoidal, or encrinital marble differs only in the fossils being
mostly remains of encrinites, resembling thin disks. Madreporic marble consists
largely of corals and the surface resembles delicate stars : it is the Pietra stellaria of the
Italians. Fire marble, or LumacMle, is a dark brown shell-marble having brilliant
chatoyant reflections from within. Breccia marbles and Pudding-stone marbles are
polished calcareous breccia, or pudding stone.
" Stalagmites and Stalactites are frequently polished, and the variety having banded
shades is often highly beautiful. The Gibraltar stone, so well-known, is of this kind.
It comes from a cavern in the Gibraltar rock, where it was deposited from dripping
water. It is made into inkstands, letter-holders, and various small articles.
" Wood is often petrified by carbonate of lime, and occasionally whole trunks are
changed to stone. The specimens show well the grain of the wood, and some are
quite handsome when polished.
" The finest statuary marbles come from the Italian quarry at Carrara (Carrara
marble) ; from the Island of Paros, whence the name Parian ; from Athens ; and from
Ornofrio, in Corsica, of a quality equal to that of Carrara. The Medicean Venus,
and most of the fine Grecian statues are made of Parian marble. These quarries,
and also those of the Islands of Scio, Samos, and Lesbos, afforded marble for the
ancient temples of Greece and Rome. The Parthenon, at Athens, was constructed
of marble from Pentelicus."
542. The common minerals found in veins in limestone rocks are
Gale spar ; Fluor spar ; the sulphurets and other ores of lead and
zinc, the former generally associated with silver ; the sulphurets,
chromate, and other salts of iron ; the oxides of titanium ; several
hornblendic and augitic minerals ; Mica and Chlorite ; Salts of ba-
rytes and strontian ; Serpentine, Talc, Steatite, Apatite, Garnet,
Emerald, Graphite, and Bitumen. Very perfect crystals of quartz
sometimes occur.
543. Sulphate of lime, or Gypsum, is frequently present in suffi-
cient abundance to be designated as rock, and is then valuable either
as yielding Plaster of Paris or furnishing Alabaster for ornamental
purposes. In the former case it is earthy or massive, but in the
latter semi-crystalline. It is also found crystalline, as in Selenite.
Gypsum is frequently associated with sands accompanying beds of
common Rock-salt (chloride of sodium). The masses thus found
are often very thick, but limited in extent.
The gypsum beds of the neighbourhood of Paris consist of three
distinct masses separated by beds of marl (calcareous clay), and having
numerous thin bands of clay and marl interstratified with each.
Each mass has some special characteristic, and may be traced to a
considerable distance. They contain organic remains rather abund-
antly distributed. Gypsum occurs frequently in lenticular or wedge-
shaped masses.
Phosphate of lime occurs as a rock in some districts, though hardly
MAGNESIAN LIMESTONE.
259
to a sufficient extent to be worth referring to here. It is usually
massive, but sometimes earthy and sometimes crystalline.
Fluate of lime, or fluor spar, called sometimes Blue John by the
miners of Derbyshire, is occasionally found in large quantities as a
massive mineral.
544. Carbonate of lime, as we have seen, often contains a small
proportion of carbonate of magnesia ; but when the latter constituent
is present in larger quantity, the mineral is called Dolomite. Very
large rock masses of dolomite occur in England and elsewhere. Dolo-
mite has lately been recommended as a building material, and is used
in the construction of the new houses of Parliament. The following
analyses of five of the principal magnesian limestones employed for
building purposes, will be useful for comparison with other rocks :
TABLE III.
ANALYSES OF MAGNESIAN LIMESTONES.
Constituent minerals.
1.
Roach
Abbey,
SG=2'134.
2.
Park Nook,
SG=2'138.
Huddle-
stone,
SG=2-147.
4.
Bolsover
Moor,
SG = 2-3l6.
5.
Bolsover
Quarry,
SG=2'324.
57-50
5570
54-19
51-10
54-05
Carbonate of magnesia . .
3.9-40
0'80
41-60
o-oo
41-37
2-53
40-20
3-60
38-58
1-30
070
0-40
0-30
1-80
1-36
Trace
1-50
T60
2-30
1-61
3-30
271
100-00
10000
100-00
100-00
100-00
I. The Roach Alibey stone, from near Bawtry, in Yorkshire, has a whitish cream-
colour; semi-crystalline; with dendritic spots of iron or manganese. 2. The Park
Nook, from near Doncaster, is cream-coloured, and in part crystalline. 3. The Hud-
dlestone, from near Sherburne, in Yorkshire, is also a whitish cream-coloured stone,
and semi-crystalline. 4. The Bolsover stone, from near Chesterfield, in Derbyshire,
is of light yellowish brown colour, and almost crystalline in its texture. The other
Bolsover stone (5) is from near Mansfield, and is of brownish colour. The specific
gravities in this table are those of dry masses. Those of the crushed particles are
much higher, ranging between 2'840 and 2'867. The limestone used for the Houses
of Parliament is from the neighbourhood of the Bolsover quarries.
The Clay Group.
545. Under this title are included chiefly impure silicates of alu-
mina ; and the most remarkable varieties of these have been already
described amongst minerals (401-403). Common clay usually con-
tains, besides silicate of alumina, a variable proportion of silica, iron,
lime, and water, with traces of manganese, potash, soda, magnesia, and
carbon, and being more frequently and more abundantly mixed with
such impurities than either limestones or sandstones, some extent of
260
DESCRIPTIVE GEOLOGY.
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GNEISS. 269
but thin when they do so alternate. Gneiss is often hardly to be
distinguished from granite even by the most experienced eye, and it
is constantly penetrated by granitic veins parallel to the apparent
planes of lamination. The contortions of the strata are remarkable
and on a very magnificent scale.
562. " The varieties comprehended under the terra gneiss are so considerable, that
no general description can be given, and it is necessary to describe separately that of
each variety. The three marked varieties of structure may be comprised under the
granitic, the schistose, and the laminar.
" The granitic variety is distinguishable by its general resemblance to granite, which
it also emulates in the infinite variety, intermixture, magnitude, and proportions of
the several ingredients. It frequently passes into granite by an undefinable transi-
tion ; and, both this transition and the resemblance to the granitic character, occur
chiefly in those cases where the beds of gneiss are in the vicinity of granite. At the
point of junction, the two rocks are sometimes undistinguishable : and a similar gra-
dation often exists in those parts which are traversed by granite veins. The distinc-
tion consists in the general parallelism of the mica, or of the hornblende ; or else of
some other ingredients ; from which cause the rock is either actually fissile, or else
displays indications of a foliated structure. As that structure becomes more perfect,
it recedes further from granite.
*'In the schistose variety, the texture is commonly minute, while the position of the
several minerals above-mentioned is more accurately parallel. Hence, the rock is
almost always very readily fissile ; and in some instances, indeed, possesses this qua-
lity in such perfection as to be applicable to the same purposes as argillaceous schist.
This variety passes into quartz rock, by the loss of its mica or hornblende, or, some-
times, of its felspar also ; and, in this case, its structure is commonly more granular
than when it passes into micaceous schist. When it graduates into the latter rock,
by the loss of its felspar, it is generally very distinctly laminar or schistose.
" The two preceding varieties are the most abundant. The laminar is rare, but it
occurs in several parts of Scotland. In this variety, each constituent mineral is dis-
posed separately in laminae nearly continuous ; and*, as the quartz and the felspar are
the predominant substances, it is marked by considerable peculiarity of aspect ; par-
ticularly when, as is not unfrequent, the former is white, and the latter red, or when
their colours are in any other manner strongly contrasted. When perfect, the lami-
nar variety presents no trace of a granular structure ; but it passes into both of the
preceding, and thus loses its definite character. Although so decidedly laminar in
composition, it is far less fissile than the preceding variety."*
563. The colours of gneiss vary considerably and are frequently disposed in stripes
producing a much greater difference of aspect in hand specimens than is really import-
ant in the rock.
The following minerals are common in gneiss, viz., Actinolite, Calc spar, Epidote,
Felspar, Fluor spar, Garnet, Hornblende, Idocrase, Molybdena, Oxide of iron, Quartz,
Tourmaline, Zircon.
564. The composition of gneiss is that of granite, and we are
now brought to the consideration of this rock by a series of trans-
itions perfectly natural, and none of them involving any extreme
amount of change. At the same time it should be clearly under-
stood that the condition of this and many others regarded as igneous
rocks does not in any case resemble that of fused rocks, since the
only examples of fused rocks of which we have any distinct know-
ledge, present appearances totally distinct, and exhibit the simple
* Macculloch's " Classification of Rocks," p. 253.
270
DESCRIPTIVE GEOLOGY.
minerals and elements of which they are compounded in an entirely
distinct system of arrangement. We have no evidence that lava by
any change connected with the continuance of heat could part with
a large part of its soda and potash bases and obtain magnesia j still
less can we show any thing like experimental proof of the original
formation of felspar crystals, or mica crystals, in a siliceous base in
modern or ancient lava, or pumice, or the separation of the quartz
.into the compact mass found in the true porphyritic rocks. These
are all subsequent and true metamorphic results, and must be treated
as such.
565. We append as before, in a tabular form, a series of analyses
which will assist in the comprehension of this part of the subject.
TABLE VIII.
COMPOSITION OF VARIOUS PORPHYRITIC ROCKS.
Component mine-
rals.
i.
Granite
(Normal).
2.
Granite
(Felspa-
thicj.
3.
Granite
(Mica-
ceous).
4.
Syenite
(mean of
several).
5.
Greenstone
(mean of
several).
6.
Protogine
(mean of
several).
Silica
72-30
74-00
68-10
69'91
54'86
75"24
15-30
14-10
18-30
10*37
15-56
6'59
4'86
7-00
0'33
Magnesia
} 3-30
2-50a
5'30a
I 6-26
9-39
9-26
Potash ....
4*55
6-83
4-55
Soda ...
} 7-40
6'80
6-40
2-69
4-03
roe
0'07
0-11
0*50
075
Water
2'00
98-30
97-40
98-10
99-21
98-82
99-05
a Includes also oxide of iron.
566. The composition of granite will be seen to conform with that
of the other rocks above-mentioned much more distinctly when we
consider the extremely variable composition of the component mine-
rals, at least within certain limits. Regarding the various groups as
silicates of alumina and potash, or soda, with various alkaline earths
replacing the alumina or alkaline bases, there will appear little to
distinguish the granites from argillaceous slates beyond their crys-
talline condition, and the presence of the alkaline bases in a some-
what larger proportion. It seems clear that these differences are
better accounted for by supposing slow change in rocks originally
mechanical by the simple action of chemical force, than by assuming
for which there is no sufficient reason the original igneous fluidity
of rocks of which many could not be elaborated in their present form
GRANITE. 271
from a state of igneous fluidity by the agency of any laws not known
to affect matter at the earth's surface. *
567. The granites form, however, too important a group of rocks
to be passed over without a more lengthened definition and descrip-
tion than has yet been given. It is usual to apply the name granite
only to porphyritic combinations of quartz, felspar, and mica, and
to recognise by other names the examples in which any substitution
is made for either mineral. Thus, when hornblende replaces the
mica, the rock is called Syenite (from the granite of Syene in Egypt) ;
when the mica is replaced by talc or steatite, it is Protogine (the gra-
nite of Mont Blanc) ; and other names have been given to different
varieties. We quote once more from Dr. Macculloch a brief but
clear statement of the essential characteristics of those rocks of which
granite is the type.
" Granite masses are sometimes continuous for a great space ; so
that they possess no definite form ; or, if any such form be present, it
cannot be discovered. At other times they are disposed in large de-
finite bodies, not unaptly compared to feather-beds, separated by fis-
sures or joints. When these masses possess large dimensions in two
directions only, they often resemble the beds of stratified rocks, and
have sometimes been mistaken for true strata. Occasionally these
dimensions are so proportioned, that they resemble irregular sphe-
roids ; but these forms appear to have resulted from the wearing of
the angles of masses originally prismatic.
" The extended beds above mentioned are frequently subdivided by
fissures into smaller prismatic and cuboidal masses j and as the sub-
divisions generally take place in two opposite directions, or are
vertical and parallel to the great mass or bed, these prisms are found
piled on each other in a manner resembling huge masonry. The
angles of the prisms being further subject to wear, as are the conti-
guous surfaces in a less degree, the result is an aggregate of irregular
spheroids often piled on each other in a very fantastical manner.
This consequence, it is evident, can only take place when the fis-
sures are nearly horizontal and vertical. In all others the detached
parts must fall away. A few rare instances occur in nature, where
the dimensions of the prisms are so considerable in one direction, that,
when grouped in erect positions, they present an irregular columnar
appearance.
" Lastly, the great laminae, or beds of granite, are often vertical as
well as horizontal or inclined ; and the rock thus presents continuous
smooth precipices laterally, while above, it terminates in sharp peaks.
" A minute but irregular prismatic structure, independent of the
former, is sometimes to be seen in granite. It is, also, occasionly mi-
nutely laminar, or exfoliates in crusts. These crusts are sometimes,
concentric respecting one or more centres, at others they are flat
272 DESCRIPTIVE GEOLOGY.
In some cases they appear to be the consequence of an original con-
cretionary structure in the rock ; in others it is equally certain that
they are produced by the action of the atmosphere, as they occur
equally in masses of artificial forms ; in the shafts of columns for ex-
ample, and in blocks squared by the tool.
568. " With these comprehensive geological features, are united
the following mineralogical characters.
" The texture is, with one exception, always crystalline and con-
fused ; the several minerals of which it is composed interfering with
each other's forms. With the single exception of the graphic variety,
it is also granular ; but varying much in the fineness of the texture,
or in the magnitude of the parts.
" The magnitude of the parts in granite is extremely various, each
constituent mineral sometimes exceeding an inch in dimensions, and
at others being almost invisibly minute. Various textures are also
often united in a very limited space, or the rock passes imperceptibly
from fine to coarse-grained. Occasionally, also, irregular patches or
veins of a fine texture, are seen imbedded in a coarser variety. In
one rare instance the parts affect a spheroidal arrangement.
"Granite, therefore, consists fundamentally of quartz, felspar, mica,
and hornblende, variously combined ; but other minerals occasionally
enter into the composition, so as to form integral parts of a common
mixture. They are, it is true, comparatively rare, but they cannot
conveniently be excluded from the definition.
" These minerals are, Actinolite, Chlorite, Talc, Compact felspar,
and Steatite.
569. "The colours of granite are infinitely varied ; that of the
hornblende, where it exists, being invariably black, or an extremely
dark green : it only contributes to modify that of the rock, by the
proportion which it may bear to the other ingredients. When in
great excess, it forms compounds nearly black : in other cases it pro-
duces various tints of grey. Grey and black tints also arise from the
presence of black mica. But this mineral is also either white or
brown, and is thus productive of corresponding differences in the
colours of the granite into which it enters.
"The felspar is subject to a greater variety of hue than either of
the other ingredients ; and, as it is commonly the most abundant,
it often regulates the colour of the rock. Dark red and white are
the most common extremes of colour, and it is also found of various
intermediate tints of red. Occasionally it is ochre yellow, pale grey,
blackish grey, or nearly black, and, in one rare instance, green. It
does not seem well ascertained whether those varieties which, like
that of Labrador, disperse coloured light, belong to granite : in some
instances, at least, it appears certain that the compounds which con-
tain them appertain to the overlying or trap family.
GRANITE,
273
" The quartz of granite is most commonly white, or watery ; and,
being generally the next ingredient in proportion to the felspar, it
also assists in many cases to determine the colours of the compound.
Occasionally it is also grey and smoke-coloured, sometimes nearly
black. It may be remarked, in concluding this part of the subject,
that each of the three preceding minerals may exist of different
colours in the same compound."
570. Granite and porphyries frequently appear in the form of
veins occupying crevices and fissures in other rocks, and very often
filling up narrow clefts in those rocks with which it is in contact.
Many examples of this are seen in Scotland, and of one the annexed
diagram (fig. 98) will give an idea, while innumerable others have
Fig. 98.
Contact of Granite with Slaty rocks in
Glen Tilt.
a. projecting fragments of granite.
b. enclosed fragments of slate.
been noticed and described in vari-
ous districts. It has been custom-
ary with geologists to refer at once
all these to a kind of injection of the
porphyry while in a state of igneous
fluidity \ and appearances have been
triumphantly referred to showing
change in the adjacent rock, and
thence assumed to afford convincing
proof of the igneous nature of the
change. Now, however, that we
know how similar are the effects of
slow chemical action at moderate
temperatures to the rapid action of
great heat, and how little the changes
produced really require the interpo-
sition of melted rock, much more careful and minute observation is
needed before the subject can be considered as settled, and much
must be done by the chemist on a large scale, and by observations of
Nature in the field as well as in the laboratory, to assist the geologist
in coming to conclusions.
571. Granite and the other rocks of the same kind frequently con-
tain metalliferous ores, contained in veins chiefly parallel to each
other, and forming series of variable interest, The metals in Eng-
land from this rock are chiefly tin and copper ; in South America,
silver ; and in the Ural Mountains, gold : but, elsewhere, many others
are found. Many simple minerals also occur in these rocks, of which
the following are the most remarkable, viz. : Actinolite, Andalusice,
Apatite, Beryl, Chrysoberyl, Corundum, Emerald, Epidote, Graphite,
Idocrase, Iron oxide, Iron pyrites, Jade, Lapis lazuli, Schorl, Spo-
dumene, Sphene, Stilbite, Topaz, Tourmaline, Tremolite.
572. Of all the altered and so-called igneous rocks that we have
described, those of one group, including the older porphyries, many
T
274 DESCRIPTIVE GEOLOGY.
basalts, and many important trachytic masses, are either less mani-
festly bedded than the others, or are so extensively developed that
their thickness cannot be determined. They also exhibit little or no
mechanical structure. It is such rocks that have been regarded by
many geologists as the solid framework or skeleton of the globe, and
have been named Primitive, igneous, or erupted, and by Humboldt
Endogenous rocks. They were also called by the early geologists Plu-
tonic, and by Sir C. Lyell Hypogene, all these terms expressing the
opinions held as to their origin. Some, however, both in former
times and now, have been inclined rather to consider the possibility
of all these being really but different forms of such substances as
make up the more distinctly mechanical rocks we mean the sand-
stones, limestones, and clays, and the substances occasionally asso-
ciated with them. We do not now wish to discuss the question, but
merely let the reader understand that the theoretical views alluded
to are not quite unquestioned, and that many additional facts and
careful deductions from them are still needed in this much neglected
department of geology.
573. " The following account of what he regards as endogenous rocks, given by Hum-
boldt, in his " Cosmos,' 1 will be useful as noting and defining some varieties of these
rocks not before mentioned. He considers the whole group as separable into several
series of rocks :
1. Granite and Syenite of very different ages, the granite often the more recent.
2. Quartzose porphyry, frequently imbedded as veins in other rocks. The matrix
is usually a fine-grained mixture of the same elements as those which form the larger
disseminated crystals. In granitic porphyry, which is very poor in quartz, the feld-
spathic base is almost granular and laminated.
3. Greenstone, or Diorite, granular mixtures of white albite and dark green horn-
blende, forming Dioritic porphyry when the crystals of albite are disseminated in a
compact paste. The greenstones, either pure, or, as in the Fichtelgebirge, containing
laminae of diallage, and passing into serpentine, have sometimes penetrated, in the
form of beds, between ancient strata of green argillaceous schist ; but they more
often traverse the rock in the form of veins, or appear as domes of green stone, ana-
logous to domes of basalt and of porphyry.
Hyperstliene rock is a granular mixture of Labrador feldspar, and hypersthene.
Eupliotide and serpentine, containing sometimes, instead of diallage, crystals of
augite and uralite, and thus becoming nearly allied to a more abundant, and, I might
almost say, a more active eruptive rock, viz., augitic porphyry.
Melapliyre, and the porphyries containing crystals of augite, uralite and oligoclase,
to which latter. species the celebrated verd-antique belongs.
Basalt, containing Olivine and its elements (which treated with acids, give gelati-
nous precipitates), Phonolite (argillaceous porphyry), Trachyte and Dolerite : the first
of these rocks is partially, and the second always divided into tabular laminae, which
gives to them an appearance of stratification, even when covering a large extent.
Mesotype and Nepheline form, according to Girard, an important part in the composi-
tion and internal texture of basalts. The nepheline in basalt reminds the geologist of
the Miascite of the Ilmen mountains in the Ural, a mineral which has been confounded
with granite, and which sometimes contains zircon ; it also reminds him of the
pyroxenic sepheline discovered by Gumprecht, near Lobau and Chemnitz.*
* Cosmos, Sabine's Trans, vol. i. p. 240.
EXPERIMENTS ON BASALT. 275
574. It would not be right to conclude this chapter, in which we
have endeavoured to prepare the reader to exercise an independent
judgment in the matter of igneous and metamorphic rocks, without
referring to the experiments of Mr. Gregory Watts on the result of
slow cooling of old lavas, and the apparent tendency to reform in
crystalline arrangement when the rate of cooling was comparatively
slow. The experiment was somewhat imperfect, and on a small
scale, and perhaps in some respects has proved too much as well as
too little to satisfy speculative geologists, but we are not aware that
it has since been repeated. The quantity of material was about seven
hundred weight, and consisted of basalt from the rock called Rowley
rag in Staffordshire.
" The mass was placed in a reverberatory furnace, and exposed to the intense heat
which is obtained in that way. It was found to melt with a less degree of heat than
would have been required by an equal weight of pig iron, and as it melted it was
allowed to subside into the deeper part of the furnace in the fonn of a liquid, but
rather tenacious glass. A portion of it being then taken out and suffered to cool, re-
tained the character of perfect glass. The remainder of the mass was left in the fur-
nace, and was cooled very gradually, not being extracted for eight days. It was then
cold externally, but still retained a considerable degree of internal heat. The extreme
irregularity of its shape caused it to be so differently affected during the cooling that
many peculiarities in the arrangement of bodies passing from a vitreous to a stony
state were thus exhibited in a very remarkable way.
5/5. " The first result, that of the rapidly cooled basalt resembling obsidian, or vol-
canic glass, is interesting and important, as it identifies two minerals exceedingly un-
like in appearance and texture. The other results obtained from examining the
cooled mass are also interesting.
" The first tendency towards arrangement in the particles of the fluid glass was
exhibited in minute globules thickly disseminated through the mass, and where the
arrangement extended a little further the mass was observed to be compact, to have
an even conchoidal fracture, and it was then of a dark chocolate colour and greasy
aspect, and resembled some varieties of jasper in its opacity and compactness.
"But the temperature favourable to the internal arrangement of the particles being
continued as in the thicker portions of the mass, another change commenced, and a
still greater advance towards stony texture was observable. This next step took
place by a fibrous radiated structure exhibited in connexion with a tendency to sphe-
roidal concretion, the centres of the formation of the spheroids being comparatively
remote from each other, and not intermingling when two come in contact, but com-
pressing one another, thus showing the nature of those conditions under which the
columnar structure becomes superimposed ; this latter being clearly only a particular
fonn of the spheroidal structure.
" The next change that took place appears to have arisen from the fibrous structure
of the spheroid becoming compact, so that the internal character of the mass was
more decidedly stony, and possessed great tenacity. Its colour was now black, and it
was quite opaque, but a continuation of the temperature appeared to render the mass
more granular, and its colour more grey, while the molecules arranged themselves
into regular forms, the whole mass becoming pervaded by crystalline laminae, polarity
being indicated, and the commencement of crystallization clearly taking place.
" The cavities at this point began to exhibit regular crystals projected from their
walls, and this went on until the mass became porphyritic, and ultimately the whole a
congeries of crystals."*
* Phil. Trans, for 1804, p. 279, et seq.
276 DESCRIPTIVE GEOLOGY.
576. Referring once more to the analyses given in several former
paragraphs, the reader, if his attention should be turned to the
chemical bearings of the science of geology, will not fail to notice the
importance of duly estimating the extent to which isomorphism may
account for the varieties presented in the composition of the several
simple minerals to which the crystalline rocks most nearly approxi-
mate. In the case of soda and potash this is remarkably the case,
there being few instances where either of these bases is present with-
out the other. Lime and magnesia, and sometimes oxide of iron,
replace each other in like manner, while sometimes water takes the
place of some of the usual component parts. In all these cases the
difficulties of obtaining any exact idea of the nature of rocks are
infinitely increased by the fact that it is only in crystalline minerals
that any approach to uniformity of composition can be traced ; while
on the other hand the usual materials presented are amorphous and
massive, and loaded with accidental matter, masking and obscuring
the true nature of the fundamental rock.
577. In addition to the difficulties thrown in the way of the geo-
logist by the infinite diversity of form presented when the same
elements are mingled in different proportions, and the substitutions
that take place of one element for another, we must also take into
consideration the obscurity that at present hangs over the whole
question of the composition of rocks, in consequence of our ignorance
of the essential conditions under which chemical action may take
place. The apparent ultimate identity of heat, electricity, and che-
mical force would suggest the possibility of many changes even in
solid masses of rock when removed from the earth's surface below
the stratum of invariable temperature, provided only time were
granted to sufficient extent. Such changes might simulate, or even
be actually identical with, those really produced in other places by
very high temperature acting for a shorter time ; while the ceaseless
course of magnetic currents through the external film of the earth
cannot but have great influence on every form of matter exposed to
its influence. There are, however, some changes that, according to
the present state of knowledge, we are bound to suppose must be
produced by exposure to great heat, but which, on the other hand,
chemical action without the rapid development of heat might avoid,
and the fact of the existence of metamorphic rocks in which no such
changes have supervened, seems to point to the necessity of recon-
sidering the whole subject of the so-called igneous and metamorphic
rocks. We can imagine nothing more worthy of the attention of the
physical chemist than to obtain and record facts bearing on these
interesting problems concerning the earth's history.
277
CHAPTER XII.
ON THE STRUCTURE AND MECHANICAL DISPLACEMENT
OF ROCKS.
578. HAVING in the preceding chapter explained to the reader
the nature of rock masses, and the circumstances under which they
may have been accumulated, we come next to consider the actual
state in which we find them, or, in other words, their structure and
position, two conditions, a knowledge of which is of the highest
importance to the practical man, and on which all accurate know-
ledge of the principles of physical geology must be based.
In describing the structure of rocks, we are obliged to use cer-
tain terms, already defined as regards mineralogy, but now to be em-
ployed in a more extended sense. Thus the lamination which in
simple minerals is easily distinguishable as a distinct and well-defined
character must now be regarded as extending through whole rocks
in infinitely varying degrees of perfection. So also Cleavage, which
is a character determining certain minerals, and enabling the crys-
tallographer to discover the ultimate simple form of many rough and
apparently shapeless specimens, here assumes a wider range, and
becomes only a kind of lamination ; while spheroidal and columnar
masses are exhibited on the grandest scale, and we have conglome-
rates which put on every appearance of aggregation, from the mere
heaping of dissimilar materials to the perfect association exhibited
in true porphyries. It will be the object in this chapter to explain
the details of structure as a fit conclusion to the account given of the
composition and displacement of rock masses.
579. The only essential points of structure may be conveniently
denominated concretionary, prismatic, laminated, and porphyritic.
Each includes several varieties, and each is frequently referred to by
geological writers under distinct names. All are more frequent and
more manifest in rocks of crystalline or semi-crystalline texture than
in those retaining distinct marks of their mechanical origin ; but
most of them may be recognised in all rocks to some extent.
580. Any accumulation of similar mineral matter in irregular
masses included in other rocks, or any condition of a rock in which
it tends to separate into spheroidal parts with or without concentric
arrangement, must be referred to the kind of structure called con-
cretionary. The more regularly the separate aggregations are ar-
ranged, the more clearly do they admit of description and definition ;
but they are not necessarily concentric in any case, nor are they
always greatly different in their nature from the enclosing rock.
278 DESCRIPTIVE GEOLOGY.
Concretions are not generally crystalline throughout their mass,
though they sometimes contain crystals either in veins or dissemi-
nated. Globular or reniform concretions are found in limestones,
sandstones, and clay, in almost all conditions of these rocks ; while
the more complete and perfect spheroidal structure characterises
basalts, granite, and other rocks called igneous. Some concretions
are represented in the annexed diagram (fig. 99).
F . 99 581. "The forms
_ of concretions are vari-
ous ; they are some-
times nearly or abso-
lutely spherical, in
which case they touch
Lenticular masses and nodules. "by points Only, and
the intervals are filled by the same or by another substance.
Examples of this are to be found in some siliceous schists and in
some limestones.
" In other cases, by compressing each other they become oblate
or indented, or assume various irregular shapes ; and they thus
sometimes form a mass which presents an aspect as much granular
as it is concretionary. Some of the shales which are found in con-
tact with trap rocks present examples of this peculiar structure.
Such concretions further possess at times a distinct lamellar or a
radiated structure ; and in one rock (pearlstone) they sometimes
contain a central particle of another substance.
582. "Rocks of this structure often acquire a botryoidal surface
after exposure to the weather j and in some instances this concre-
tionary arrangement is so concealed in the apparently uniform frac-
ture of the rock, that it is only distinguishable under these circum-
stances.
" In the cases to which the preceding remarks apply, the general
structure of the rock is concretionary throughout. The concretions
are also of limited size, varying from that of poppy- seed to the dia-
meter of an inch : but in other instances the concretionary structure
is confined to particular parts of a rock, or insulated concretions are
imbedded in an uniform mass. Such concretions are commonly of
large size, and generally in the form of oblate spheroids. In some
rare instances they are attached in pairs by a cylindrical stem ; in
others they are cracked on the surface into polygonal forms, which
are consequently frustra of pyramids." *
583. But, in addition to these examples, many basalts and granites
are absolutely converted into a mass of concentric globes of various
dimensions but with no interstices ; and some limestones, containing
much carbonate of magnesia, exhibit large heaps of detached and
* Macculloch's " Classification of Rocks," p. 125.
CONCRETIONARY STRUCTURE. 279
hard spheroids of carbonate of lime, separated only by magnesian sand.
These abound in the magnesian limestone of the coast of Durham,
where they are accompanied by very singular concretions of other
and more complicated forms, some being honeycombed, others con-
centric, and others laminated.
The most remarkable instances of concretionary structure that have yet been de-
scribed are seen on some parts of the coast of Durham, where the magnesian limestone
forms bold cliffs, which appear as if made up of an irregular pile of cannon balls. In
this case, however, the carbonate of magnesia forms but a subordinate part of the rock,
the concretions themselves consisting of carbonate of lime ; and it would seem that,
during the process by which the concretionary structure was effected, the magnesia
was almost entirely separated, and left in the form of dolomitic or magnesian earth.
The curious spheroidal masses above alluded to are found associated with the lami-
nated variety of magnesian limestone; and, on separating the beds, the laminae are
often seen not to be continuous, but made up of circular plates, running into one another.
In this case the discoid forms of the laminae indicate a tendency to aggregation about
different centres, even when, owing to some cause, the operation could not develope
itself in a vertical direction.
At the planes of separation, however, between two of these laminated beds, the
concretions are more perfect, and approach the spherical form ; the spheroidal masses
impress both the upper and lower surfaces of the beds with which they are in contact ;
and the rock exhibits at one and the same time an earthy, a crystalline, a laminated,
and a spheroidal structure. It is clear, therefore, that the concretionary form has
been superinduced by some internal movement of the particles after their deposition.
When the concretions are more perfect they are sometimes grouped into beautiful
and regular clusters, or by mutually penetrating each other, produce a number of gro-
tesque forms, and occasionally a kind of honeycombed appearance, in which the small
cells are arranged in horizontal lines, but still in concentric circles.
584. Many rocks offer extensive and numerous bands, which con-
sist of the aggregated particles of some one mineral originally disse-
minated, and now separated from the mass. Thus in impure clays
containing some carbonate of lime, calcareous nodules, not without
a proportion of argillaceous matter, collect into distinct layers, as
in the bed of clay through which the Thames makes its way ; and in
other clays, as the shales of the coal-measures, a carbonate of iron
abounding with earthy impurities has been frequently formed in
bands parallel to each other and at no great distance apart (see
466). It is easy to perceive that these were not rounded before
deposition, for they actually graduate into the enclosing rock ; nor
are they, as might be expected, concentric, but, on the contrary, they
are generally laminated, the laminae having the same direction as the
great mass of the stratified rock of which they form a component
part.
585. " The laminae of the nodules are precisely parallel to the
laminae of the shale or marl in which they are enclosed, and little
doubt can exist that they once constituted continuous portions of
each other. The particles of calcareous matter have separated from
the mass of marl, and have congregated together as we now see
them. When we fracture these nodules through their centres and
280 DESCRIPTIVE GEOLOGY.
parallel to the laminae, we generally find some fossil, such as a fish, an
ammonite, a nautilus, or a piece of wood, which seems to have formed
the point of attraction to the various particles of calcareous matter
that have assembled together. We might, therefore, infer that a
fossil or other foreign body was always necessary to the production
of the nodules ; but, though such bodies are very commonly disco-
vered in the centres of the nodules, they are not always present in
them. The nodules have resulted from the aggregation of these
particles in such a manner that the original laminated structure has
not disappeared. If we conceive a particular line of deposit to have
contained calcareous matter, which, though insufficient to constitute
continuous limestone beds, was too plentiful to remain disseminated
in the marl without endeavouring to arrange itself differently and in
small masses, we may probably approximate to the truth. This
view is borne out by considering how some of the upper beds of the
lias limestones at the same place are circumstanced. They are evi-
dently only extended lines of flattened nodules, which are, however,
not generally laminated but compact, the arrangement of the particles
having been more general.
" Now the latter structure in rocks, evidently mechanically pro-
duced, and even not calcareous, must be familiar to every geologist,
though it is more prevalent where calcareous matter is intermingled
with other substances. It is common in various sandstones, and is
evidently the result of the attraction of certain particles among each
other after deposition. The lamellar structure of nodules in siliceous
sandstones is sometimes also observable, an aggregation of particles
having taken place on the same principle as that above noticed in
the lias, the cementing matter being sometimes calcareous, at others
siliceous.
586. " Layers of nodules not lamellar, yet composed of substances
which have separated out from the constituent parts of a mechanical
rock after deposition, are common in many strata. The ironstone no-
dules of the coal-measures seem to have been thus produced. They
also sometimes contain organic remains, such as portions of fossil vege-
tables ; but as multitudes exist without organic exuviae, they are
evidently not essential to the formation of the nodules. The matter
of nodules appears sometimes to have separated out from the body of
the rock in which they are found in such a manner, that there has
been a contraction of parts from desiccation in the interior, producing
cracks which have subsequently been filled up by the infiltration of
carbonate of lime.
" In the concretions commonly known as turtle-stones, Indus Hel-
montii, &c., the external parts have first become consolidated, so that
during the desiccation of the interior, the internal parts were com-
pelled to separate into cracks and shrink towards the circumference,
CONCRETIONARY STRUCTURE. 281
leaving the largest fissures in the innermost parts, as must necessarily
happen. The subsequent filling up of the cracks is generally illus-
trative of the gradual accumulation of matter from the sides of such
veins towards their middle portions. Coat above coat of carbonate of
lime cover one another until the sides meet, highly crystalline matter
filling up the irregular cavities which have often thus resulted. No-
dules of this description, which generally exhibit no trace of either
concentric or lamellar structure, are frequent in many clays and
marls."*
587. Concretionary structure then generally involves some changes
from the original conditions of deposit, but these run through an
almost infinite gradation. In clays the concretions, as we have seen,
consist of the impure and earthy carbonates of lime or iron, origin-
ally disseminated through the mass, but subsequently collected into
definite masses. In limestones, siliceous concretions are more com-
mon, but sulphuret of iron is not rare, while in siliceous rocks, as
sandstones, we find marl, gypsum, rock-salt, and other substances.
So, again, in cavities which are not veins, we find concentric masses
of iron and manganese oxides, and of carbonates of copper. On the
surface of clays, such minerals as Websterite appear, and elsewhere
the magnesian minerals form into concretionary masses. Fullers-
earth and many described simple minerals, belong to the same group
of phenomena, being segregated bands ; and many instances of substi-
tution observed with regard to organic remains, must be regarded as
fundamentally of similar nature.
The following analyses "f of red marl from the Old red sandstone of South Wales,
containing cornstone (calcareous) nodules, and also of one of the nodules embedded,
will illustrate the nature of the change when this segregation takes place. The rock
originally must have contained a good deal of silicate of alumina and carbonate of
lime, or in other words, must have been a chalky mud.
Marl. Nodule.
Silica 64-3 19-5
Alumina 2M 7'2
Carbonate of lime 0'2 69'3
Peroxide of iron 9'6 2'2
Water 4'5 0'9
Traces of chlorine, &c., and loss 0'3 0'9
100-0 100-0
588. Different as they may seem to be, there is little doubt that
concretionary and prismatic structures truly pass into each other by
insensible gradations. The former, when most complete, is seen in
spherical masses, flattened, as if by pressure against each other : the
usual condition of what is called ' columnar basalt,' in many of the
best known and most remarkable exhibitions of that rock. On the
other hand, the prisms which are most characteristic of the second
* De la Beche's " Researches in Theoretical Geology."
t " Memoirs of the Museum of Economic Geology," vol. i. p. 63.
282 DESCRIPTIVE GEOLOGY.
kind of structure, are also frequently rounded at the angles, and de-
composition proceeding regularly from the surface towards the centre,
lays bare the concentric arrangement which has been induced. But
it is not always that the wear proceeds thus regularly. It often
commences in several places at once, and tends to split the rock into
coarse laminae, and thus indicates lamellar instead of concentric ar-
rangement. There is, however, this difference that in the structure
we are now describing, the forms approximate those of cubes, or
rhombs, and represent a more advanced state of crystalline action
than the former : and in most cases this advance is seen even in the
texture of the rock and the nature of the contained minerals.
589 There may be considered to be two kinds of prismatic structure
the simple prismatic and the columnar, the former being usually
observable on a much larger scale than the latter, and affecting such
rocks as granite, crystalline limestone, quartz rock, and slate ; while
the latter is seen best in basalt, where the quantity of matter is by
no means so considerable. All the rocks exhibiting either kind, con-
tain occasionally simple crystalline minerals, and between interstices
are found plates of quartz, carbonate of lime, sulphate of barytes,
oxide of iron and manganese, native silver, native gold, platinum,
and other metals. The structure of the rock itself is often distinctly
crystalline ; occasionally throughout, but more frequently as a con-
fused crystalline, or amorphous and massive rock, in which crystals
are embedded. Many terms are used to describe this condition-of a
rock, in which it splits more readily in one direction than another,
and in all kinds of quarrying and mining a knowledge of its nature
and amount is in the highest degree important. The grain of gran-
ite is of this kind. So also are the joints in most calcareous building
stones, and the dine in coal, the latter material offering indeed excel-
lent examples of this kind of structure, and being at the same time
distinctly altered and presenting other crystalline characters.
590. " In the columnar structure, as the term implies, the prisms
generally possess a considerable length in proportion to their breadth,
and they are not limited to the quadrilateral form. In a few in-
stances, owing to the extreme shortness of the prisms, the columnar
passes to a tabular, or a lamellar and jointed structure ; but the two
are united under this head, in consequence of their general resem-
blance and of the undefinable line by which they are separated.
Where the columnar structure is on a very large scale, it might be
supposed to belong to that division which is included under the term
of external configuration ; but, in reality, it is properly placed
here.
" The columnar structure is invariably aggregated. No instance
is known of a single column, as there are of single spheroids, included
in an amorphous mass. Pitchstone scarcely offers an exception, as
PRISMATIC STRUCTURE. 283
the small columns which it sometimes exhibits, are portions of
lamellae.
" As the prisms are often accumulated in a parallel manner, of the
same length, and for a considerable space, they unite to form a bed,
or pseudo-stratum ; or else such a bed appears to be split into prisms,
and that division generally takes place nearly at right angles to the
leading planes. But as such planes are not necessarily parallel, so,
in a mass of prisms, the lengths of these concretions will be found to
vary in different parts.
u Not unfrequently the most regular columnar structure vanishes
in the same continuous mass, and in a gradual manner. This takes
place, either laterally or in the direction of the axis.
591. "In a columnar mass, the axes may be vertical, or inclined
to the horizon at any angle, or horizontal ; and, in these cases, it is
implied that the prisms are straight, as well as parallel to each other.
The parallel position is not, however, necessary. In a collection of
prisms, they are sometimes found to radiate from some imaginary
centre, or from more than one. In other cases, they are placed in va-
rious irregular ways and entangled together. In some instances such
irregular prisms are found more or less accumulated, or dispersed
and intermixed with the same rock in an amorphous state. When a
collection of prisms is parallel and erect, with straight axes, and on
a large scale, well known effects of architectural regularity are pro-
duced. These are exemplified in the Giants' Causeway, in Fingal's
Cave in Staffa, and in many other localities.
592. " The prisms are not necessarily straight. At times they are
slightly, at others, very conspicuously curved. Sometimes the same
curvature affects a considerable associated number ; or the prisms are
then bent in a manner more or less parallel. In such examples, the
general effect of regularity is not destroyed. In other instances the
curvatures are variously opposed, or the bent are intermingled with
straight prisms.
" A columnar mass is sometimes formed of a collection of short
prisms, placed in a manner more or less parallel, but so that the ex-
tremities of some are in contact with the middle parts of others. In
such cases they impress each other, and the effect of regularity in the
structure of the mass nearly disappears.
" As the prismatic is united to the bedded form, so it occurs toge-
ther with the concretionary ; but, in the only instances known, the
prisms are short and united with the amorphous mass. On the small
scale, as in columnar ironstone, which is but a modification of shale,
a collection of prisms is not only curved but sometimes minutely
undulated.
593. " The prismatic structure is not limited to beds, or masses,
but occurs also in veins. In this case the prisms are most commonly
284 DESCRIPTIVE GEOLOGY.
at angles to the plane of the vein. But they have been also found to
occur in a direction parallel to it, and either horizontally or verti-
cally placed. The columnar structure is sometimes combined with
the lamellar ; and the lamellae may either be parallel, or at right
angles to the axis of the prism.
" In an aggregate of prisms, they are always found in contact, ex-
cept in the case of an union with the spheroidal structure, when they
are separated by empty intervals, or by intervals filled with another
substance. The contact is sometimes such as to admit of the ready
separation of the prisms ; at other times, there is a partial or more
complete coalescence.
594. " The sizes of prisms are various. In diameter or thickness
they rarely exceed nine feet ; and from that, they vary to one foot or
less. In columnar ironstone (which, as a modification of shale, is
here ranked with rocks), they are sometimes even less than the tenth
of an inch, so that the mass becomes nearly fibrous. In length, they
vary from 1 foot to as much as 300 feet, or even more ; but when
the length becomes so considerable, it is difficult, for want of access,
to determine truly whether the single prisms of a mass are continu-
ous throughout. The forms are equally various, from three-sided,
upwards, even to twelve ; but figures of four, five, and six sides, are
the most common. Such figures are by no means regular, unless in
a few accidental cases ; and every modification of form may be found
aggregated in the same mass. Nor are the sides of the prisms neces-
sarily straight ; being sometimes convex or concave.
595. " Prisms are sometimes continuous for a considerable length.
At others they are divided by oblique or irregular joints. In many
instances the joints are at right angles to the axes and occur at dif-
ferent intervals, from an inch to many yards. When such joints
possess an average general distance varying from one to three feet,
a considerable appearance of artificial regularity follows; and it
must be remarked, that the -most perfect and numerous joints occur
in the most regularly formed columns. They are in some cases, as
already noticed, so frequent as to produce tabular prisms, not reach-
ing to or exceeding an inch in size.
" In the joints the surfaces in contact are sometimes uneven, at
others flat, at others again, alternately concave and convex ; and
either of these forms may be found in the lower portion. In some
remarkable examples of a lower concave surface, the angles of the
inferior portion protrude in a point which covers a corresponding
deficiency in the upper. In others, equally remarkable, the surface
of a joint is marked by a channel parallel to its boundary and near
the edge of the prism. The first of these is exemplified in the
columnar traps, or basalts, the last in columnar ferriferous shale, or
ironstone.
CLEAVAGE. 285
596. "In the smaller columnar structure the prisms are some-
times longitudinally striated ; and, in some instances, further dis-
tinguished by protuberant rings or inseparable joints. Examples of
this may be found in limestone, in jasper, and in argillaceous iron-
stone.
"In the act of decomposition, the portions of jointed prisms some-
times give indications of a lamellar structure, which, in the progress
of desquamation, leaves a spheroidal nucleus, each successive lamina
becoming gradually more regularly curved. This case is analogous
to that which occurs in the common prismatic structure already
noticed, and admits of the same doubts as to its real nature." *
597. The structure called laminated is either that which will be
fully exemplified and explained in speaking of stratification, or else
a more completely fissile kind called also cleavage. The latter will
here need careful consideration. It is confined to slate rocks, and is
greatly limited even amongst them, if we regard the term in its
strict sense, for in many so called slate rocks, only a small propor-
tion of the whole mass will be found to split in delicate and well-
marked cleavage planes. Cleavage, however, often passes into a
still more perfect foliation marked by distinct crystals on the planes
of foliation, and this is the case not only with slates, but mica and
hornblende schists, and gneiss.
598. In most rocks exhibiting cleavage there is some evidence to
be obtained of stratification, and some proof of subsequent mechani-
cal disturbance. It appears that generally the direction (strike) of
cleavage planes is parallel to that of elevation or to the principal
anticlinal axes of the district. In Wales, over more than two-thirds
of the Principality, where slate rocks are abundant, this direction is
between N.N.E. and E.N.E. ; in the Lake district of Westmoreland
and Lancashire, E.N.E. ; in Devonshire and Cornwall it is generally
W.S.W. to E.S.E. But it is chiefly in South America that these
phenomena are presented on such a scale as to lead to a notion of
their real extent ; and there, Mr. Darwin informs us, that for a space
of 300 miles on the shores of the Chonos and Chiloe Islands (lat.
41 to 46 S.), there is seldom a deviation of more than a point of
the compass from a N. 19 W. and S. 19E. cleavage strike, while
the same direction is retained with little change over a very much
greater range of country. In these cases there seems no complete
coincidence between the strike of the cleavage and that of the strata,
but the general range of the axis of elevation often agrees with
the latter direction.
599. While the direction of the cleavage planes is thus constant
there seems generally to be a wide and singular diversity both in the
amount and direction of the dip or inclination. The angle of dip
* Macculloch's "Classification of Rocks," p. 129, et seq.
286 DESCRIPTIVE GEOLOGY.
is generally high, but varies or oscillates from one side to the other
of a vertical plane. The dip of the cleavage has manifestly no rela-
tion whatever to that of the beds, or to the changes of position which
they have undergone, and not unfrequently on the two sides of the
same mountain chain we find the inclinations opposite and converg-
ing downwards, the cleavage planes between them being vertical.
This is the case in the Alps and other mountain districts, and
bears no doubt upon the general question of the forces involved in
the production of the phenomena. In some cases, though not com-
monly, a second cleavage is found to have affected the same rocks,
but this seems only a further exemplification of the metamorphism
the rock has undergone.
600. It is highly probable, if not absolutely certain, that a pro-
cess of change has gone on during a long period and to an enormous
extent in all rocks, but especially those silicates of which alumina
is the principal, and the other alkalies and iron the secondary bases.
The effect of such changes has been to re-arrange the particles of
the rocks, producing a new and perfect lamination in some one plane
determined by local and external circumstances, and a less perfect,
but recognisable lamination in a direction transverse to the prin-
cipal one, tending to collect like mineral masses in these planes.
Most of these planes will be found parallel to one principal line of
direction, having distinct relation to the general elevating forces
which have produced the existing physical features of the district,
and have terminated when these physical features were firmly and
permanently impressed on the earth's surface. What the cause may
have been we will not here speculate, but that it was something
more than mechanical, and something less than igneous, will, we
think, be at once admitted by every one who has studied the pheno-
mena however slightly.
601. The last important variety of structure is porphyritic, by
which term geologists have agreed to denominate all rocks having
crystals imbedded in a matrix. Granite, Syenite, and a host of
other rocks are of this kind, and trachytes, basalts, altered slates,
Fresh- water series 350 1
Barton clays . ... 300 [
Ores de Beauchamp . . 50
Calcaire grossier, and
Glauconie grossiere. 100
Baffshot sand 400
Bracklesham sands 700 *
Bognor beds 250
Sables inferieurs (part) 100
Mottled clay and sand 80
Mottled clay and sand 150
Argile plastique .... 60
830
1750
540
761. The important relations of the Lower Tertiary deposits in these
three districts will be at once seen in the above table, by which it
appears that the upper part of the series is only presented in the
continental locality, the middle part chiefly and most perfectly in
Hampshire, but also in each of the other two, while the lower mem-
* See " Quarterly Geol. Journ.," vol. Hi, p. 400.
360 DESCRIPTIVE GEOLOGY.
ber is most important in the basin of the Thames, but well repre-
sented also in Hampshire and Paris. The lowermost member of the
series is nearly the same in each locality, but the others differ greatly.
We proceed to consider some of the most interesting points with
respect to each of the principal divisions.
762. The gypseous series of the neighbourhood of Paris is interest-
ing and worthy of notice, both for its fossil contents and its mineral
composition. It consists of a siliceous limestone of fresh-water
origin, occasionally alternating with, and sometimes covered by white
and green marls, with a considerable quantity of gypsum, the latter
being chiefly developed in the centre of the basin-shaped depression
in which the Tertiaries are there deposited. These beds contain land
Fig. 172.
Skeleton of Palseotherium
(Paris Basin).
and fluviatile shells, fragments of wood, and great numbers of the
bones of fresh-water fish, of crocodiles and other reptiles, of birds,
and even of quadrupeds, the latter being usually isolated, and often
entire. The gypsum beds have been extensively quarried for the
manufacture of " Plaster of Paris " (obtained by burning the gypsum),
and have yielded a multitude of mammalian remains, of which the
above diagram (fig. 172) will give some idea. It is chiefly the lower
part of the gypsum which may thus be regarded as a great charnel-
house of extinct quadrupeds ; but the uppermost strata, composed of
thick beds of marl either calcareous or argillaceous, are also worthy
of notice, and contain numerous silicified trunks of palm trees.
763. The beds next in order in the neighbourhood of Paris are
those which have been long known as the calcaire grassier, and they
are not less remarkable for their fossil shells than the former are for
their abundant remains of quadrupeds. They consist of coarse
limestones, often passing into sands, and alternating with clayey and
calcareous marls and hard limestones. Nearly a thousand species of
shells are contained in the calcareous sands, and amongst them have
been determined no less than 140 species of one genus, Ceritkium,
BAGSHOT SANDS.
361
usually an inhabitant of brack-
ish water. One remarkable and
gigantic species is figured (see fig.
173), and often attained a length
of upwards of a foot.
764. The fluvio-marine and
fresh-water beds of the Hampshire
basin are best exhibited at Headon-
hill (Alum Bay), and also atWhite-
cliff Bay, in the Isle of Wight,
where they form a large series of
sands and limestones containing
fossils. The Barton clays which
next succeed, and the Bracklesham
sands, have generally been regarded
as contemporaneous with the Lon-
don clay of the Thames basin, but
must now be regarded as higher in
the series. They include a consi-
derable variety of fossiliferous clays
containing more or less marl and
sand, and may safely be referred to
the period of the calcaire grossier.
765. The Bagshot sands have
only lately been so far made out as
to be referred with satisfaction to
any particular part of the Tertiary
series, but since the investigations
of Mr. Prestwich, they must be
looked on as the true and somewhat
important representatives of the
Bracklesham sands, and, therefore,
as immediately succeeding in age,
as well as position, the beds of
clay known as the 'London clay.'
They consist of three principal
members, the middle part contain-
ing clayey deposits, and occasion-
ally presenting fossils, while the
upper and lower are almost entirely
siliceous, and fossils are exceed-
ingly rare. They usually form
barren and heathy districts, and
are frequently found covering the
true London clay.
Fig. 173.
Cerithium giganteum
(Older Tertiary).
362 DESCRIPTIVE GEOLOGY.
766. The London clay, represented in Sussex by the more com-
pact and concretionary beds found at Bognor, is a well marked and
peculiar deposit, generally between 200 and 350 feet thick, and re-
posing on an important series of mottled clays, sands, and pebbles of
the same age as the " Argile plastique " of the vicinity of Paris, and
for that reason the beds are not unfrequently, though very inappro-
priately, called the Plastic clay formation. These mottled clays and
sands have a thickness sometimes amounting to 150 feet, and are
often very distinct in their mineral character from any associated
deposits.
The middle and principal portion of the London clay is generally
of a blackish colour, and tough, but is often mixed with greenish-
coloured earth and white sand, and occasionally encloses layers of
oval or flattened masses of clayey limestone, called " septaria," which
are traversed in various directions by cracks, filled completely with
calcareous spar, and are particularly abundant in the neighbourhood
of Harwich, where they are much used in the manufacture of " Par-
ker's Cement." Many parts of the London clay contain, also, hard
bands, either calcareous or siliceous, and sometimes fossiliferous, and
the cliffs of Harwich occasionally include, besides the veins of sep-
taria, other beds of true calcareous matter.
767. On the continent of Europe there are several localities in
France, besides the Paris basin, where Eocene Tertiaries occur, and
we have already mentioned the deposits on which Brussels is built,
as having the general characters of the London basin. In Northern
Italy, in the neighbourhood of Nice, is a nummulite rock of this
period ; and at Monte Bolca is a remarkably fossiliferous limestone,
also contemporaneous, and containing numerous remains of fishes,
while in many parts of the Mediterranean other beds, also fossilifer-
ous, have been found, of whose Eocene age there can be no doubt.
Besides these, however, we also find widely developed, not only in
Italy but in the Alps, the Apennines, and on both flanks of the Py-
renees, and again in Greece, Asia Minor, and Egypt, a very important
and thick deposit, often of a calcareous nature, chiefly remarkable
for'the vast preponderance among its fossils of a Foraminiferous
genus named Nummulites, so called from its resemblance to a piece
of money. This has generally been referred to the cretaceous or
Newer secondary period, but it is at least partly Tertiary, and Sir
Roderick Murchison has lately endeavoured to prove the necessity of
referring the whole to this newer date. However this may be, there
is no doubt of the study of these beds proving of great interest, and
affording one of the chief connecting links between the deposits of
India and those of Europe. The importance of following out this
question may be judged of when it is remembered that this nummu-
litic formation " extends at intervals through no less than 25 degrees
OLDER TERTIARY FOSSILS.
363
of latitude, and near 100 degrees of longitude, its northernmost ridge
on the north flank of the Carpathians being clearly identifiable with
its southernmost known limb in Cutch, and its western masses in
Spain and Morocco being similar to those of the Bramahpootra."*
768. We next proceed to the consideration of those fossils of the
group which are most valuable as giving an idea of the actual con-
dition of the earth at the time of the deposits of this period ; and
here we at once remark, that so far as the British Islands serve as
the indication, there is strong proof of a great change having occurred,
since the general character of our Eocene fauna and flora is tropical.
With one or two exceptions, indeed, all the species are extinct, and
do not range to formations either above or below.
Fig. 178.
Fig. 180.
Fig. 177.
Group of Fossils of the Eocene period.
Fig. 174. Orbiculina numismalis.
175. Bulimina Murchisonii.
176. Sagrina rugosa.
177- Venericardia imbricata.
178. Serpula in Cardium porulosum.
179. Ampullaria acuta.
180. Turitella imbricataria.
The fullest catalogue of British Eocene fossils (Mr. Tennant's) gives
the number as follows : Plants 100 ; Zoophytes, 4 ; Echinoderms, 5;
Foraminifera, 8; Annelida, 11 ; Cirrhopoda, 3; Crustacea, 4; Con-
* Murchison on the Structure of the Alps. Quart. Geol. Journ., vol. v. p. 305.
364 DESCRIPTIVE GEOLOGY.
chifera and Brachiopoda, 235 ; Gasteropoda and Cephalopoda, 267 ;
Fishes, 97 ; Reptiles, 14 ; Birds, 1 ; Mammals, 14. In addition to
these, however, a very considerable number of species occur exclu-
sively in the Paris Basin, so that upwards of 3000 species in all have
been referred to by Professor Bronu, in his tables already more than
once referred to. Of these, 57 are Mammalia and as many as 136 are
referred to the Vegetable Kingdom. The remains of plants in the
Older Tertiary beds are, however, chiefly fruits, and are almost entirely
obtained from the London clay beds of the Isle of Sheppey, though
other localities are known.
769. The invertebrated animals show a large preponderance of the
ordinary genera of mollusca, and of these a few are represented in
the group of figures annexed (figs. 177 180). There is, however,
a manifest departure from recent specific forms, especially those
inhabiting the immediate vicinity, and, as we have mentioned above,
a tropical character is traceable in the whole arrangement of the
group. When we regard the higher organisations, as those of verte-
brated animals, we find a much further departure from existing local
types, and this is seen the more strikingly as we advance towards the
higher mammals. The fishes, chiefly met with in the London clay,
the beds of Monte Bolca and those of Mount Lebanon, offer repre-
sentative species of a large number of genera and natural families,
of which the modern species are well known. The following short
comparative table will, however, give the best notion of these
relations.
British species Fossil species in
now existing. the London clay.
Perch family 7 7
Mackerel family 11 12
Cod family 20 4
Herring family 8 2
Eel family 8 J_
54 26^
To this we may add, that four of the recent families richest in
species now, are either without a single Eocene species, or are very
sparingly represented, while on the other hand and in their place we
find three extinct genera of one family, now almost confined to the
southern seas ; one of a family now absolutely tropical, and five of
another family now almost limited to the Mediterranean.
770. The reptiles of this period, like the fishes and shells, show a
marked resemblance to the inhabitants of much warmer and more in-
sular climates than those met with at present in the Temperate Zone
of the Northern Hemisphere. They include several lacertian and
crocodilian animals ; some turtles and tortoises, and some gigantic
serpents, which attained a length of from ten to upwards of twenty
AMERICAN EOCENE DEPOSITS. 365
feet. The remains of birds are not wanting to add to the evidence of
this kind.
The land quadrupeds of the Eocene period in Europe, include
several species, all extinct, and most of them referable to the order
Pachydermata, which seems to have been, to a certain extent, the
representative form at that time of the existing groups of Ruminants.
Amongst the fossils must also be mentioned, the remains of a monkey,
a bat, and a few carnivora.
771. The North American representatives of the Eocene rocks are
chiefly found in the Southern states of Virginia, Carolina, and
Georgia ; and consist, in Virginia, of green sand and marl, accompa-
nied by green earth, precisely like older beds belonging to the upper
secondary series of New Jersey, but containing very different fossils.
Further to the south the nature of the deposit changes, and highly
calcareous white marls and white limestones appear, which are covered
by red and white clays, ferruginous sands, and associated layers of
burrstone and siliceous rock. In other places a white limestone
(Santee limestone) characterises these deposits, and has led to the
idea that a passage downwards existed to the cretaceous rocks. Sir
C. Lyell, however, has found that no such passage is indicated by the
fossils. About 125 species of Eocene American fossils are mentioned
by Sir C. Lyell as determined on good authority ; and of these only
seven are identical with European Tertiaries of this age. At least one
fourth of the whole appear, however, to be very closely allied to Eu-
ropean fossils of the same age ; while another fourth differ greatly
from any species obtained from the Eocene strata of Europe, although
belonging to genera abundantly represented in these formations.*
772. South America unquestionably presents, on both sides of the
Andes, Tertiary strata of very ancient date, referable to the Eocene
period. These are of great extent, especially along the shores of the
Atlantic ; but the deposits on the two coasts differ almost entirely in
their fossil contents. It would appear, however, that there is no
evidence, in this part of the world, of the climate having materially
changed, or at least none of its having been more tropical than it
now is in the same latitudes. There is evidence of great change of
level to the extent of 700 or 800 feet of depression along both lines
of coast during this period ; and in the newer deposits there is proof
equally strong and satisfactory, of a large amount of elevation.
773. Among the minerals of importance obtained from Tertiary
deposits, we may mention the stream-ores of gold, platinum, and other
rare metals found with these ; the similar deposits of tin ore ; the lig-
nites met with in various parts of Europe, Asia, and America ; the
fragments of amber from the shores of the Baltic, and the diamond
gravels and sandstones of India and Brazil : of many of these some ac-
* " Quarterly Geol. Journ." Vol. i. p. 442.
366 DESCRIPTIVE GEOLOGY.
count has already been given, and we only now add a brief account
of the circumstances under which the two latter minerals occur.
774. Amber is found in nodules varying in size from that of a
nut to that of a man's head ; but the latter size is very rare. It is
also met with on some sea-coasts, and near the mouth of some great
rivers. It has been found in Sicily, Poland, Saxony, Siberia, and
Greenland : also in our own country, on the Yorkshire coast. Even
some of our clay pits have yielded it : for instance, in one near St.
George's Hospital, Hyde Park Corner, excellent specimens have been
found. But the situation in which it is obtained in most abun-
dance is in East Prussia, along the coast of the Baltic, between
Memel and Dantzic, especially along the shore near Kb'nigsberg.
Amber can seldom be obtained by mining operations ; although
pits are occasionally sunk in sandy downs to the depth of more than
100 feet, where it occurs in small quantities. The usual mode of
searching for it is to explore the sea-coasts after storms, when the
amber is found in nodules rounded by the sea, in a manner similar to
pebbles on the sea-shore.
775. The way in which diamonds are obtained is by digging for
them in the beds of torrents, or among the mud and sand brought
down by periodical rains, where it accumulates chiefly on one bank,
at the mouths of some of the smaller streams, and in the low shift-
ing islands along the shore. They are found in India in the river
Mahanadi, from Chunderpore, where the river Maund joins the main
stream to Sohnpore, where the Mahanadi makes a sudden bend
to the left, producing an extensive mud bank on the northern shore,
making altogether a course of 120 miles. Throughout this extent
the diamond-searchers ply their trade from the time when the rains
cease until their periodical return.
The process of exploring is exceedingly simple, and the only tool
employed is a sharp pickaxe. With this tool the men dig into every
promising spot, and deposit on the banks of the river all the mud
and sand they get up. There it is looked over by the women and
children of the tribes, who for this purpose take a plank five feet in
length by two in width, hollowed out in the middle, and furnished
with a rim on each side three inches in height : they place this plank
in a position a little inclined, just enough to allow water to run off,
heap upon it the mud and sand dug from the river, and continue for
some time to pour water upon it. As soon as the water runs away
perfectly clear, they anxiously look over the hard stony matter which
is left upon the plank, and pick out all the loose pebbles and larger
pieces of gravel ; these they throw away, and the remaining mass,
consisting of smaller grains, they remove to another plank of the
same form as the first, but smaller, and spread it carefully over the
surface, so that every particle can be separately examined ; this they
SYSTEMS OF ELEVATION IN THE TERTIARY EPOCH. 367
do one grain at a time, throwing away all that is merely stone or
gravel, and laying aside every particle of gold or crystal of diamond.
They usually contrive to place the board so that the sun shall shine
upon it at a certain angle during this operation, so that every particle
shall be well illumined. The earth chiefly sought after, and most
accurately examined, is a red ochry clay, containing a small pro-
portion of oxide of iron ; in this the diamond is most commonly
found ; though, as it is sometimes met with in the loose mud, the
whole is well washed and examined.*
776. The general result of the investigations of Tertiary deposits,
may be summed up as follows : First, The European Tertiaries gene-
rally have been deposited not far from land, but in isolated patches,
having little resemblance either in mineral character or fossil con-
tents with those at any considerable distance. The land was, pro-
bably, insular throughout the greater part of the Northern Hemi-
sphere, and gradually more so as we look back into the early history
of the period : so that while the newer deposits are chiefly on pre-
sent lines of coast and low river-valleys except indeed where there is
distinct proof of great local elevation within a short time the older
beds are more distinctly marked and far more indicative of permanent
and important change ; and they seem also to be more independent of
each other. They are, besides, more varied with fresh-water marls and
even with travertin and other deposits from fresh water. During this
period there must, therefore, have been very considerable alterations of
level ; for when we look at the present elevation of several beds, which
must certainly have been formed in tolerably deep water, no doubt
can remain as to this point. In addition, however, to the mechanical
deposits which we have hitherto exclusively considered as of Tertiary
origin, we must now take into account the marks of igneous action,
and the metamorphoses that have altered the condition of various
large mineral masses during the time. Thus, in Central Europe,
south of the Alps, we find striking proofs of change connected with
recent volcanoes ; and these are not confined to the neighbourhood
of Vesuvius and Etna, but extend to the northern part of Italy, and
are no less clear in the Euganean Hills than in Sicily. On the north-
east coast of Spain, also, Catalonia affords convincing proofs that
Nature was not idle. In Greece similar effects have been produced,
and like causes have been at work ; while in Central France, and on
the banks of the Rhine, the ancient volcanic craters may still be
traced, and the erupted products yet remain, forming hills and filling
up valleys, and mingled with various organic remains that mark, in
many cases, the date of eruption. But are there, it may be asked,
* " Penny Magazine," vol. vii. p, 447.
368 DESCRIPTIVE GEOLOGY.
no other marks of change 1 The study of the Alps, difficult and
complicated as it is, has certainly answered this question in the affir-
mative ; and at whatever age those grand movements of elevation
commenced, which have uplifted the East and West mountain-chains
of the Old World, it cannot for a moment be doubted that throughout
the whole of the Tertiary period this line was becoming more distinct,
the mountains loftier, the valleys deeper, and the various deposits
more completely modified from their original condition. Besides the
Alps, however, numerous other mountain-chains of lower elevation
may be traced in Europe ; and one of the most eminent living Geolo-
gists (Elie de Beaumont) has endeavoured to bring together the
known facts with regard to these, and to draw important generalisa-
tions concerning the age of each. Although these views have been
admitted by most recent French writers without question, and are
certainly of great interest and value, we do not propose here to relate
them in any detail, nor could we venture to discuss their truth and
reality in the limited space of the present volume : we shall, there-
fore, conclude this chapter by first mentioning the principal periods
of elevation during the Tertiary period, as given by M. de Elie de
Beaumont, and then giving a general statement of the changes of
the Tertiary epoch.
777. It is considered then that there have been five principal
directions of elevation during the deposit of Tertiary beds, besides
one during which the earlier beds were accumulated. It will, how-
ever, be more convenient in describing them, to commence with the
earliest movements, and so proceed in order of occurrence. The first
period of disturbance, then, during the Tertiary epoch, is supposed
to have brought the Pyrenees into their present place, or at least to
have removed the chalk from its original horizontal position before
any of the Tertiary deposits had been made. It is believed that the
same elevatory movement produced at the same time the nearly
parallel mountain-chains of the Apennines, the Julian Alps, the
Carpathians, and many alps in Eastern Europe, besides numerous
dislocations in the north of France and the Wealden district in Eng-
land and in Germany ; thus being one of the most widely extended
and important disturbances that has affected Europe. Its direction
is stated as being W. 18 N. and E. 18 S.
778. The next principal elevation is supposed to have taken place
between the Older and Middle Tertiary periods, to have produced the
chain of Corsica, and to have upheaved the Paris basin, the valleys of
the Loire and the Garonne, the whole of Switzerland, and the valley
of the Rhone, besides producing many smaller lines of elevation in
Italy. Indications of the same disturbance are supposed to be trace-
able in the Jura Alps and in the eastern part of the Mediterranean.
.The direction of the movement is considered to be north and south.
LIGNITES OF THE TERTIARY PERIOD. 369
779. The next system is that of the Western Alps, and is supposed
to have originated between the deposit of the Middle and Newer ter-
tiaries. It is imagined that the lofty elevations of Mont Blanc and
Monte Rosa are due to this elevation, but that it is traceable very far,
reaching even to Scandinavia in the north, and to the Atlas Mountains
of Africa. Its estimated direction is S. 26 W. and N. 26 E.
780. The next is the system of the principal Alps, supposed to
range W. 16 S. and E. 16 N., including the whole range from the
Bernese or Western Alps, from the Valais to St. Gothard, and extend-
ing eastward into Austria. Besides this, almost the whole of Europe
is believed to have participated in the same movement.
781. The last great elevation is assumed to have taken place after
the Drift period, and to have produced certain dislocations and eleva-
tions in Tuscany, South Italy, and Greece, and also in Sardinia and
the coast of France. Its direction is described as N. 20 W. and
S. 20 E. It is called by M. de Beaumont the System of Tenare.
782. It has also been suggested that these directions may prevail
in synchronous elevations in other parts of the world, and thus that
the mountains of Brazil may have relations with those of the Western
Alps, and the Himalayans with the principal Alps. But it must be
admitted that the generalizations already made concerning this sub-
ject are sufficiently wide, if the difficulty of estimating the true direc-
tion of a mountain chain and the true parallelism of any two chains
are taken into account.
783. The following view of the changes experienced by the oceans
and seas during the Tertiary epoch will fitly conclude the present chap-
ter. It is from the account of the Geological Map of the World in John-
ston's edition of the Physical Atlas already quoted. " During this
epoch the Mediterranean, or another great and corresponding inland
sea, covered the deserts of Sahara, Lower Egypt, and part of Arabia;
for not till long after the commencement of the period were the pre-
sent contours defined, and the lagunes and ancient shores left dry.
Later still, the strait of Gibraltar probably did not exist, and the
waters of our inland sea mingled, through the channels of the Red
Sea and Persian Gulf, with those of the Indian Ocean ; which seems
to explain the analogy of the fossils of the Middle and higher ter-
tiary Mediterranean beds with creatures still living in the Red and
Indian Seas, and with fossils of corresponding age in the great basin
of the Black Sea and Caspian. At the same epoch too, the North
Sea and the Baltic spread over the plains of Northern Europe ; and
another ocean stretched from the recesses of Siberia, and joined with
the Mediterranean, by the Black Sea. Asia Minor contained small
isolated basins ; though the Black Sea, on the south and east, was
confined by its present banks. In the south of Asia, a broad strait
severed the peninsula of India, then a triangular island, from the
B B
370 DESCRIPTIVE GEOLOGY.
chains of the Himalaya and their dependents ; and there existed also
a great fresh-water basin in the peninsula beyond the Ganges, two
other basins at least in China, one on the banks of the Lower Amour,
and two in Siberia. As in the case of Europe, the centre of this
continent was covered by an inland sea, which has now wholly dis-
appeared. Other aqueous masses covered Persia, and probably formed,
later even than the Tertiary epoch, one basin dependent on the
Caspian, and another annexed to the Indian Sea. In another dis-
trict of the continent, large portions of the isles of Sunda, the Philip-
pines, Borneo, New Guinea, and Australia were at this period under
the waters ; and many volcanic peaks now existing, and belonging to
great areas of elevation, had not yet risen above the surface of the
Indian or Malay Seas. Turning to the map of America, we discern
evidence of changes equally singular and extensive. The Gulf of
Mexico then penetrated deep into Mexico, Florida, the lower basin
of the Mississippi, and also into the basins of the northern rivers
of South America. It washed the southern extremity of the Alle-
ghanies, as well as the feet of the Ozark Mountains, and the Mexican
and Columbian platforms. Farther north, a great interior ocean
overspread part of this continent, comprehending the higher Missis-
sippi, and the great lakes. The Gulf of Mexico already contained
a few islands composed of old formations, probably of much larger
size than those whose shores it now washes ; but its volcanic isles
sprung into existence subsequently, during that series of subsidences
and elevations, of ecroulements of the chains along the ancient shore
of South America, which drove the sea from the Ozark Mountains
and the Alleghanies, and fixed its limits farther south. The
northern part of the continent had three islands, the basin of the St.
Lawrence separating the district of the Alleghanies from dry land
on the banks of Hudson bay, and perhaps bending round to the
Icy Sea. The platform of Mexico and Guatemala formed an appen-
dix of the long isle of the Rocky Mountains ; and the Ozark Chain
advanced into the waters. The volcanoes of continental America, as
we see them now, were contemporaneous with the formation of the
Mexican and Mediterranean basins. In South America we discern
abundant proof that, at the Tertiary epoch, the Atlantic covered the
great strait between Brazil, the Andes, and central Guayana, as well
as between the Parima and the chain beyond the Orinoco ; whence
the mingling of the tributaries of this river and the Amazon, as well
as the mode of the division of the waters between certain affluents of
the La Plata and the Amazon. South America was then composed
of three great islands ; for the isthmus of Panama did not exist."
371
CHAPTER XV.
OX THE ROCKS AND FOSSILS OF THE SECONDARY EPOCH.
784. The deposits of the Secondary epoch so far as they have been
as yet examined and described in various parts of the world, may
with some convenience be divided into four principal groups, each of
which again presents well marked subdivisions. Although these
have been already stated in the general tabular view of formations
at the close of Chapter xiii., we here repeat the chief divisions
before proceeding to describe the rocks in detail.
n , f 1. The Upper cretaceous series.
Cretaceous system ..( 2 . The Lo ^ er cre taceous or greensand series.
Clitic system
Liassic system.
Triassic system.
1. Upper cretaceous series.
785. The Cretaceous or newest division of the Secondary or Middle
period is very well exhibited in many parts of Europe by the chalk,
a calcareous deposit too well known to require further description.
Below the chalk and other nearly contemporaneous rocks there occurs
an important group of sands called by French and other continental
writers Neacomian, as being typically represented in the neighbour-
hood of Neuchatel in Switzerland, but in England usually spoken of
as the " Lower greensand formation," that name having been long
familiar to English geologists. We shall find it convenient to de-
scribe the upper and lower divisions of this system separately.
The divisions and usual synonyms of the upper members of the Cretaceous system
are pretty much as follows, but they vary in particular localities, the names of the beds
requiring modification in distant localities, and becoming inapplicable where they have
reference to mineral structure. It is only in England and Europe that characteristic
names have been given, and the corresponding beds in America are quite distinct in
mineral character. In the subjoined table the names of the principal subdivisions
are given, and such synonyms added as are likely to be found useful.
English, Danish, and Belgian
series.
French series.
German series.
Chalk of Faxoe, Denmark.
Maastricht beds, Belgium.
Upper chalk, with flints.
Middle and lower chalk,
(without flints) and
Clunch.
Chalk marl.
Upper greensand.
Gault.
Terrain senonien.
/ Terrain turonien.
1 a. Craie chloritee. \
| b. Glauconie crayeuse j-
V c. Craie tufau.
Terrain albien.
Upper Quader sandstone
Upper Planer limestone.
r Middle Planer.
< Lower Planer.
372
DESCRIPTIVE GEOLOGY.
786. The Chalk is a remarkable and familiar rock widely dis-
tributed not only in England, but in many parts of the continent of
Europe. It is a nearly pure carbonate of lime,* containing, Lime
56*5, Carbonic acid 43'0, Water 0-5, and having a specific gravity
of 2-3. It absorbs water readily. With the chalk are usually found
either bands of black flint or disseminated silex, the flints being
generally in the upper portion, and the lower beds more mixed
with sand, calcareous matter, and iron. Fossils are found in the
chalk very commonly, but by no means universally. Among those
in the upper beds are several Infusoria and Foraminifera, and nu-
merous small corals ; many species of sea-urchin (fig. 181), many of
the remarkable shells spoken of in a former paragraph (\ 145) as
Fig. 182. Fig. 183.
Group of Chalk Fossils.
Fig. 181. Ananchytes ovatus (Upper chalk).
,, 182. Hippurites organisans (Lower chalk).
,, 183. Plagiostoma spinosum ( Upper chalk) .
Eudistce, one of which is there figured, and another is represented in
the annexed figure (182). There are also numerous bivalve shells
(fig. 183 is a very common species), besides remains of Cephalo-
* The following analysis of chalk from Denmark by Professor Forchhammer has been very
recently published :
Carbonate of lime 98'779
Carbonate of magnesia '641
Phosphate of lime 'Oil
Silica '352
Loss '217
100-000
RANGE OF THE CHALK. 373
poda (figs. 157, 158), Crustaceans, Fishes, and Reptiles. The chalk
is a deep sea deposit, and is unlike any rock now known to be in the
course of formation, though it may be compared with deposits re-
sulting from the finely powdered mud accumulated in coral lagoons.
787. The Upper cretaceous rocks are but little made use of in
England except when burnt into lime, or mixed with other soils for
agricultural purposes. The Lower and harder beds have, however,
been employed for internal work occasionally, in cathedrals and other
large public buildings, and they stand well if not exposed to accident
from mechanical violence. Clunch is the name usually given to the
varieties of this kind.
788. The Chalk ranges through England in a north-easterly direc-
tion from Hampshire to the Yorkshire coast, running out in two
spurs to the east, one proceeding along the south coast, forming the
South Downs, and terminating at Beechy Head ; and the other form-
ing the North Downs, and extending to the sea at Dover. The Ter-
tiary deposits of the London and Hampshire Basins cover up and
conceal much of the deposit. Chalk occurs in Ireland on the north-
east coast, but is there partly covered and altered by basalt. The
average thickness of the chalk in England is generally estimated
at about 1000 feet.
789. Crossing the channel which separates England from the con-
tinent the white chalk may be recognised forming cliffs on the shores
of France opposite both Dover and Beechy Head, and the bed recurs
in Denmark in a line continued from the Yorkshire coast towards the
north-east. Rocks of the same kind and of contemporaneous date
range eastwards through a great part of Europe often in a much
harder state than in England, and without the peculiar aspect of the
deposit. In Poland, however, true white chalk is again found, and
extends to the south of Russia, covering the plains of Moldavia, and
constituting the western part of the Crimea. In the chain of the
Caucasus beds of the Cretaceous period, consisting of pure white
chalk, flank the metamorphic rocks of the central axis of the moun-
tain ridge, and even put on something of the physical aspect of the
Downs in the south-east of England.
790. Although totally different in mineral character the Upper
Quader sandstone of North Germany is a contemporaneous rock,
generally a sandstone of loose texture, and extremely barren in or-
ganic remains. Only about 30 species have been obtained from it,
whilst the whole number of chalk species is stated by Bronn to
amount to nearly 3000.
791. In many parts of South Europe, North-eastern Africa and
Asia, there are found bands of limestone containing fossils, chiefly
either corals or Foraminifera, one genus of the latter being especially
common, and from its resemblance to a piece of money very easily
374 DESCRIPTIVE GEOLOGY.
recognised. These fossils, called Nummulites, are found both in low-
est Tertiary and uppermost Secondary deposits, and cannot be con-
sidered to mark the exact age of the beds, but they are valuable
indications, and often the only ones present. Nummulite limestones
occur in Asia Minor, and may be traced at intervals along the wide
tract of country between the Mediterranean and Western India.
Similar rocks occur in North Italy, but are there certainly of older
Tertiary date, and have been already alluded to. The opinion re-
cently adopted by Sir R. Murchison of the contemporaneity of all
Nummulitic beds we are not inclined to put forth at present as gene-
rally admitted, and it is, perhaps, safer to regard many of the Italian
foraminiferous rocks, and much of the Macigno, so widely distributed
in Southern Europe as of doubtful age, while others, among which
the Alberese is most remarkable, is a deposit unquestionably creta-
ceous. The uppermost of the beds, called by Italian geologists
Scaglia, is also a representative of the chalk.
792. The Upper chalk of England is remarkable for containing
bands of nearly pure, black, siliceous concretions well known as
flints. These appear to possess in many cases an organic centre or
origin, but have not unfrequently been segregated long subsequently
to the original deposit of the bed. In the lower part of the chalk
true flints are rarely found, but instead of them grains of silica are
mingled with the rock as an impurity, and are often accompanied by
a good deal of argillaceous matter. The lower bands thus charac-
terised are known by various names, of which Chalk marl is, per-
haps, the most convenient, and they are not unfreqiieutly coloured
with green particles of silicate of iron, or dark red particles of the
oxide of the same metal. These beds are represented in France by
the lower members of the " Terrain turonien," which exhibit nearly
the same peculiarities as in England, though to somewhat greater
extent. In Germany the " Upper Planer " is a marly limestone of
clear grey colour containing about 75 per cent of carbonate of lime.
793. Below the Chalk marl appear bands of still more argillaceous
and siliceous character, the limestone passing often into a greenish
calcareous sandstone coloured by silicate of iron, and thence called
the Upper greensand. This deposit is generally represented by are-
naceous beds or true sandstones in Saxony, and by somewhat similar
beds in France. The following account of the Upper greensand
will be sufficient to give a general idea of its character in England.
This bed is not extensively shown in the South-east of England,
but there is no doubt of its actual presence. Between Godstone and
Reigate, in Surrey, it begins to assume a decided character, and
is quarried for a particular kind of sandstone, called " fire-stone,"
which is valuable for lining fire-places and furnaces. Still further
to the west, and near Petersfield, it runs out beyond the foot of the
UPPER GKEENSAND AND GAULT. 375
chalk escarpment, passing insensibly into the Lower chalk, but the
whole of the terraces (which are at least two miles broad) are exclu-
sively composed of this bed, locally called the " Malm-rock."
Something of a similar step-like appearance may also be observed
in the Isle of Wight, and especially at Black Gang Chine, where the
bed has a thickness of about 100 feet, the lower part being sandy,
with spongiform masses, and the upper part containing abundance of
chert, or hard siliceous rock.
794. Proceeding northwards to the Vale of Wardour, the Upper
greensand is still well represented, the whole series of beds of which
it is composed rising abruptly on the north side of the valley, and
forming a narrow ridge of unequal height. The thickness here is as
much as 50 or GO feet, and the upper beds contain chert. In North
Wiltshire the formation occupies a slightly prominent step below the
foot of the chalk, but towards the north-east it becomes less and less
important, until, in Bedfordshire, it is not more than seven feet thick,
although it still retains its cherty character. In Cambridgeshire
even this peculiarity is gone, but there remains about 18 inches of
a soft sandy mass (rarely containing green particles), separating the
Gault from the Lower chalk. The bed, however, though thus de-
based in its character, is remarkably persistent throughout ; and
further north it again contains chert and firestone, and is finally
observed developed in its characteristic form on the Norfolk coast.
795. Before concluding this account of the Upper greensand for-
mation notice should be taken of a remarkable outlier, forming the
Blackdown Hills in the county of Devonshire. These hills are
capped by about 100 feet of sandy strata representing the lower
part of the Cretaceous system, and consist of layers of cherty con-
cretions, alternating with loose sand. Four of the layers are worked
for whetstones, the mines or pits being driven almost horizontally
into the hill to a considerable distance, and the masses of which the
whetstones are made varying from 6 to 18 inches in diameter. The
looser stone is employed for building.
796. From these workings numerous organic remains have been
obtained, often in fine preservation, and converted into chalcedony.
Upwards of 150 species have thus been determined, of which 90
are not known to occur elsewhere in England, and the deposit must,
probably, have taken place under circumstances somewhat different
from those of the rest of the formation.
Amongst the fossils are some represented in the annexed group ;
these include, however, species from the underlying beds also.
797. The Gault immediately overlying the Lower greensand
is rarely absent, and may, perhaps, be considered as the most per-
sistent of all the subordinate beds of the Cretaceous group in England,
scarcely ever changing its peculiarities of mineral composition or fossil
376
DESCRIPTIVE GEOLOGY.
remains. At Folkstone, where it is seen in perfection, it rises gra-
dually towards the west of the town, and forms a cliff about 120 feet
thick, resting distinctly on the Lower greensand, the section being
well exposed, and the stratum extremely fossiliferous.
Gault is a provincial term, used originally in the middle of Eng-
land, to designate the brick clay, which there belongs to the part of
the Cretaceous system we are now considering. It is a stiff clay
of a blue colour, and the inferior portion of it abounds with iron pyri-
tes, while the upper part contains green particles of silicate of iron.
Fig. 186. Fig. 185. Fig. 187.
Group of Upper greensand and Gault Fossils.
Fig. 184. Nucula pectinata.
,, 185. Ostrea carinata.
186. Ammonites Rhotomagensis.
187- Turrilites costata.
Various nodules and concretions are found throughout, which are
sometimes fossiliferous, but more frequently obscure, and of doubt-
ful origin.
798. The following careful measurements of a section of the Upper greensand and
Gault on the south-east coast of the Isle of Wight, is by Mr. Simms :
Feet.
Upper
greensand.
Gault.
/ Parallel layers of soft rock and chert 37
I Sand, with beds of stone and chert 67 104
j Light coloured gault 43
t Blue gault. No fossils 103 146
Total 250
799. The ' terrain albien' of M. D'Orbigny, is the French repre-
sentative of our Upper greensand and Gault, and puts on something
of the same character. In the north of Germany the Middle Planer,
a sandy or marly bed, poor in fossils, represents the sandy, and the
Lower Planer, a very variable rock, often containing Hippurites,
the argillaceous bases of the Upper cretaceous system. In the east of
Europe the English types are repeated to a small extent j but still
LOWER GREENSAND SERIES.
377
further to the east they have not been recorded. There is a schist
or slate in the canton of Glaris, in Switzerland, contemporaneous with
our Gault.
800. In North America the newer part of the Cretaceous system is
exhibited in several places, but nowhere in the same form as with us.
The rocks there are loose sands, with calcareous bands. They afford
lime, and contain lignites, and somewhat resemble the crag of Suffolk.
They are presented at intervals on an irregular line, measuring nearly
3000 miles in extent. In the Texas there are contemporaneous rocks,
consisting of hard compact siliceous limestone. In South America
there are also cretaceous deposits of the age of our chalk, but they
are not abundant.
2. Lower greensand series.
801. The lower part of the Cretaceous system is hardly less impor-
tant than the upper, although in England it is much less perfectly
exhibited. Along and near the south coast of our island, and at the
back of the Isle of Wight, there are, however, large and important series
of deposits referable to this series. The following is the arrangement
as determined in England and on the Continent of Europe.
English series.
French series.
German series.
1. Argillaceous beds.
2. White and green sandy
beds, and clay.
3. Kentish rag.
4. Atherfield clay.
1. Terrain aptien.
(Argile a plicatules.)
2. Terrain neocomien.
a. Argiles bigarrees.
6. Argiles ostre"ennes.
c. Calcaire a spatan-
gus.
Lower Quader sandstones.
Hilsthon.
Hils-conglomerat.
802. The uppermost member of the Lower part of the Cretaceous
system in England is, as may be seen by the Table, a group of argil-
laceous beds often ferruginous and containing some sands. Then
succeeds a large group of white and green sandy beds, alternating with
many clays, and then succeeds the bed called sometimes the Kentish
limestone, or Kentish rag, which is of considerable value for various
purposes, being used chiefly as rough building stone, and having
a somewhat wide range in the south-east of England. These all ap-
pear in considerable thickness, the series at Hythe measuring 400
feet, and at the back of the Isle of Wight more than double that
amount. The bottom of the whole series is a clay deposit, which
seems to pass very insensibly into the underlying fresh-water clays of
the Upper Wealden.
803. Many fossils are found in the English, and many others in
the Continental deposits of this period ; one or two of the more cha-
378 DESCRIPTIVE GEOLOGY.
racteristic and common of which are represented in the group an-
nexed (figs. 188, 189). A proportion of the whole consists of species
strictly confined to particular parts of the formation, and therefore,
highly characteristic. (See also ante, figs. 145, 147.)
Fig. 188. Fig. 189.
Fossils of the Lower greensand (Neacomian beds*.
Fig. 188. Spatangus retusus.
,, 18Q. Trigonia alseiormis.
804. The ' Plicatula clay,' or Aptian formation of some French geo-
logists, is considered to be identical in position with the upper part
of our series j while the so-called Neacomian beds occupy the place of
the sands and stones of the middle part of the series. According to
this view, so far from the Neacomian deposits representing our Weal-
den, which belongs to the Oolitic period, they do not even reach so
far down as the base of the true Cretaceous series. It is, however, not
improbable that some localities in France and Switzerland may really
be older than our Kentish rag. The Lower Quader, the German re-
presentative of the period in Saxony and Bohemia, is a coarse sand-
stone of loose texture, having a calcareous cement and containing
fossils towards the base ; it is much used as a building material, the
lower portion being well adapted for this purpose.
Deposits of this period possessing considerable interest, have been
found in India near Pondicherry, and also in South America. They
contain fossils analogous, though not identical, with those found in
European beds of the same age.
805. The Speeton clay is a dark blue laminated bed, with nodules
of clay ironstone, having peculiar fossils, but probably belonging to
the base of the Cretaceous system. It occurs only near Scarborough,
in Yorkshire.
3. Wealden series.
806. The Wealden formation consists of a very thick and varied
series of arenaceous beds, based on imperfect limestones, and covered
by a bed of clay. The whole series contains the fossil remains of land,
fresh-water, and estuary animals, and of land vegetables. The group
is interpolated between the uppermost beds of the Oolitic group and
WEALDEN SERIES. 379
the lower ones of the Cretaceous series ; but it offers so many analo-
gies with the former in the nature of its fossils, and passes so insensibly
from it, that it has been considered a member of the Oolitic system.
The following is a tabular arrangement of the different beds in
descending order, as they are observed in various parts of the south-
east of England :
1. Weald clay, with subordinate limestone (called Sussex marble) and sand.
2. Hastings sand, including the beds of Tilgate forest.
3. Purbeck strata, consisting chiefly of compact limestone alternating with clay,
and resting on fissile limestone and the Portland beds.
807. The Weald-clay, the uppermost member of the Wealden
group, though rarely of greater breadth than five or six miles, may
be distinctly traced in England, in the counties of Kent and Sussex,
coming out from under the lowest beds of the Cretaceous system. It
is also visible on the coast of the Isle of Wight, and the highest por-
tion, wherever it appears, consists generally of a blackish clay, in
which are abundant fresh-water shells and other fossils.
The strata which form the base of this superjacent group consist
of beds of sandstone and shelly limestone, with layers of argillaceous
ironstone. The limestone is called " Sussex marble," and is strik-
ingly characteristic of the Weald-clay in England, occurring in
layers which vary from a few inches to more than a foot in thickness,
and which are separated from each other by seams of clay or coarse
friable limestone. It is almost entirely made up of fossil shells
(Paludina), united by a calcareous cement into compact marble,
and has been used, like the Purbeck marble, in the internal decora-
tion of churches and cathedrals, and to make the small insulated
shafts of pillars so common in Gothic architecture.
The limestone, however, is not the only one of the Upper Wealden
strata which has been used for economical purposes, the argillaceous
iron ore contained in it having been formerly worked on the borders
of the once extensive forests of the Weald.
808. The Tilgate beds may be considered to occupy the upper
place in the next or Hastings sand series : and they receive their
name from having been formerly extensively quarried in Tilgate
Forest, near Horsham. They consist of several bands of bluish-grey
sandstone or rather calcareous grit, which are of no great thickness,
and alternate with friable sandstones, some of them highly ferrugi-
nous, others of a white colour and without iron, and others again
containing particles of lignite. The lower of these beds form a con-
glomerate, containing pebbles of quartz, which have apparently been
transported from a great distance.
The lower beds of the Hastings sand are well seen in the cliffs near
Hastings, and consist of a friable sandstone (in which caverns are
excavated) based on beds of shelly limestone and grit, and alter-
380 DESCRIPTIVE GEOLOGY.
nating with shale and clay. These strata are overlaid by another
series of sandy beds, containing a fine building stone, and, together
with the former ones, they abound with organic remains, chiefly
those of fresh-water molluscs.
809. The Purbeck strata, the base of the Wealden formation, may
be divided into two parts, the lowest of them being a coarsely fissile
limestone, locally called " slate," which has been used for roofing and
other economical purposes. This bed, together with a slaty clay with
which it is associated, is of considerable thickness, and is succeeded
by finer compact limestones, abounding with bivalve shells of the
fresh-water genus " Cyclas." These compact fossiliferous limestones
again alternate with clay, and include a thick bed, almost entirely
composed of oyster-shells. The limestones of this part of the series
are quarried for building purposes, as many as fifty-five beds of use-
ful stone being known j and the whole thickness of the upper mem-
ber of the group amounts to about 125 feet. The beds at the top
consist chiefly of the remains of an univalve shell " Paludina," ce-
mented together by carbonate of lime and a large proportion of green
matter ; they have formerly been much worked, and are well known
under the name of Purbeck marble, formerly used in the internal
decoration of cathedrals, &c.
810. Wealden deposits have been found on the coast of France, in
the Bas Boulonnois, and contemporaneous beds are known in some
parts of Scotland, and in the north of Germany. The latter are
extensive and important, consisting chiefly of sandstones, and are
developed to great thickness.
811. The fossils of the Wealden period are chiefly the remains of
plants, a few fresh-water shells and crustaceans, several insects, and
the bones of fishes and land reptiles ; the latter of very great inter-
est, of gigantic proportions, and including herbivorous as well as
carnivorous genera.
812. Dr. Mantell, to whom we are indebted for the most detailed account of the
Wealden formation, describes it as u a series of clays and sands, with subordinate
beds of limestone, grit, and shale, containing fresh-water shells, terrestrial plants, and
the teeth and bones of reptiles and fishes ; univalve shells prevailing in the upper,
bivalves in the lower, and Saurian remains in the intermediate beds ; the state in
which the organic remains occur, manifesting that they have been subject to the
action of river currents, but not to attrition from the waves of the ocean."*
4. The Oolitic or Jurassic series.
813. This great series of deposits is divided naturally in England
into three parts, the upper consisting of the Portland beds reposing
on the Kimmeridge clay, the middle presenting the Oxford clay
covered by the Coral rag, while the lower is far more varied, and
includes numerous bands, chiefly calcareous, but many of them sandy
and clayey.
* Geology of the South-East of England, p. 180.
UPPER OOLITES. 381
The general appearance of the Oolites in England may be described as consisting of
three ridges, running north-east and south-east (or rather north-north-east and south-
south-west) with three extensive and rich plains intervening. The ridges represent
the escarpment of the hard limestone beds of the Lower, Middle, and Upper oolites
respectively, and the plains the softer and less coherent clays and shales alternating
with them. The lower deposits lap over the great plains of the Lias on the west,
and on the east the Upper greensand usually forms a low escarpment, capping
the uppermost beds of the Oolitic series whatever they may be. In the centre
of England, the upper beds are usually absent; in the west, and in the vicinity
of Bath, the whole sequence is nearly perfect ; in the south, the lower lime-
stones form the escarpment, while the upper beds occupy an important place in the
sequence ; and lastly, in the north, it is chiefly the central portion of the system that
is developed, the calcareous part of it there attains its maximum of thickness and
importance.
814. THE UPPER OOLITES. The beds of this age, which are called
on the Continent the Portlandian group, are, so far as the British
Islands are concerned, almost entirely confined in their development
to the south of England, only that stratum of clay which usually
forms the base of the group being exhibited in Yorkshire, in the vale
of Pickering.
815. The group of strata containing the Portland stone, and exhi-
bited in Portland Island, includes several layers of coarse earthy
limestone, which rest on a bed of siliceous sand, mixed with green
particles. This is called the Portland sand, and sometimes attains
a thickness of as much as eighty feet in the west of the island, and
forms a complete passage into the underlying clay.
Above the coarse limestones of the lower part, which usually con-
sist of alternate hard and soft layers to a thickness of fifty or sixty
feet, there are three beds of serviceable stone, interstratified with
clayey or siliceous bands : fossils occur in all these strata, but they
are rare in those beds of the stone which are worked to advantage
for economical purposes.
816. In the upper part of the Portland series, there occurs a very
interesting bed, about a foot in thickness, of a dark brown substance
containing much earthy lignite. This bed, called " the Dirt-bed,"
seems to be made up of black loam, which at some distant period
nourished the roots of trees, fragments of whose stems are now found
fossilized around it. Wherever the dirt-bed is laid open to extract
the subjacent building stone these remains of trees occur, and they
are placed at such distances from one another as trees growing in a
modern forest.
It results from the circumstances of this deposit that the surface
of the Portland stone, at the termination of the Oolitic period, must
have been for some time dry land, and covered with a forest ; and
we have a kind of measure even of the duration of this period in the
thickness of the dirt-bed, which has accumulated more than a foot of
black earth, loaded with the wreck of its former vegetation. " The
382 DESCRIPTIVE GEOLOGY.
regular and uniform preservation also of this thin bed, over a distance
of so many miles, shows that the change from dry land to the state of
a fresh-water lake or estuary (which the nature of the overlying rock
proves to have succeeded the period of dry land), was not accom-
panied by any violent denudation, or rush of water, since the loose
earth, together with the trees which lay prostrate on its surface, must
inevitably have been swept away had any such violent catastrophe
then taken place."*
817. The Kimmeridge clay is of a blue, slaty, or greyish yellow
colour ; it frequently contains a considerable quantity of selenite
or crystallized sulphate of lime ; it usually effervesces with acids, and
exhibits in tolerable abundance both vegetable and animal impres-
sions, although its fossils are rarely in such good condition as to be
preservable in a collection. It is a bed of great thickness, horizontal,
or nearly so, in its stratification, extremely persistent in its peculiar
mineral and fossil characters, but not very extensively developed
either in England or on the Continent. The name Kimmeridge clay
has been applied to it because it is well exhibited at Kimmeridge Bay,
and near the village bearing the same name in the isle of Purbeck.
At this spot there are also found, alternating with the clay, cer-
tain beds of highly bituminous shale, occasionally used for fuel, and
locally known as the Kimmeridge coal. There are many beds of
lignite found in the Oolites, but these are perhaps the most remark-
able, next to those of the lowest Oolitic deposits of Yorkshire and
North America. (See the note at the end of this chapter.)
_. 10A 818. The fossils of the Upper
oolites, in England, include, as we
have already seen, numerous re-
mains of vegetables, and besides
these are many univalve and bi-
valve shells, of which two are
figured in the adjacent cut (Figs.
190, 191). Articulated and ra-
diated animals are rare. Remains
shells from the Upper oolites. o f fishes, of turtles, and of some
^J3gS2^$t marine saurians > occur > but no
mammals.
819. Among the foreign rocks of this part of the Oolitic period
are 1st. the Calcaire de Blangy, on the coast of Normandy ; 2, the
upper beds of the Jura, in Switzerland ; and 3, the Solenhofen beds.
The first are of the age of the Kimmeridge clay, but far more calca-
reous, and, indeed, the Upper oolites of the Jura approximate much
more nearly than the other parts of the system to the Kimmeridge
clay and Portland rocks. The former bed is represented with some
* Buckland and De la Beche. Trans. Geol. Soc. 2nd Series, vol. iv. p. 16.
MIDDLE OOLITES. 383
accuracy by greyish schistose marls containing the Gryphsea virgula ;
but there is a prevalence of iron oxide in the deposit, and about
forty feet of strata, in which pisolitic ore of this metal abounds,
appear to be intermediate between the 'gryphsea virgula' marls, and
the overlying limestones called Portlandian. This apparent pecu-
liarity seems to be owing chiefly to the action of some cause by
which the iron has been separated from the mass, and accumulated
in a bed, instead of being left disseminated. Throughout the whole
series the limestones predominate greatly over the argillaceous beds,
and this appears to be most strikingly the case in the Jurassic
district of the mountain chain of the Alps.
820. The sequence in the north and centre of Germany is nearly
the same as in the Jura, except that the subdivisions are not so
strongly marked, and that we find there a bed of great economical
importance, namely, an exceedingly fine-grained fissile limestone of a
rich cream colour, abounding in fossils, chiefly met with in the north
of Bavaria, near the towns of Solenhofen, Pappenheim, &c., and ex-
ported to most parts of Europe for the purposes of lithography.
On the banks of the Donetz in South Russia there are beds of
Oolitic limestone of light yellow colour, which appear to belong to
this division of the secondary series.
821. THE MIDDLE OOLITES. These consist, for the most part, of a
thick bed of clay, called the Oxford clay, widely expanded through-
out England, and met with also in the same form on the Continent,
and a series of overlying limestones chiefly remarkable for the abun-
dant remains of corals found in them.
822. The upper beds of the Middle oolitic series are partly
calcareous and partly sandy, the former consisting chiefly of a very
interesting group of corals, known under the name of Coral rag, and
the latter the sandy beds (or calcareous grits) often more or less
intermixed with calcareous matter, and containing thin laminae of
clay sometimes passing into irregular bands of hard and tough
marly rock. This calcareous matter seems entirely due to the pre-
sence of crushed and decomposed organic remains.
It is chiefly in Wiltshire, near the towns of Calne and Steeple
Ashton, and in the surrounding neighbourhood, that the corals of
the Coral rag are found in greatest abundance and perfection ; and
this part of our island at the time of the deposit, has clearly existed
in the condition of a coral island in an open sea. The thickness of
the bed is about forty feet ; large portions of it are frequently made
up of the remains of a single species, and an earthy calcareous free-
stone, sometimes used as a building-stone, and full of fragments of
shells, rests immediately upon it, and is surmounted by a fine grained
ferruginous sandstone, slightly Oolitic in structure, and containing a
few fossils, marking the close of the Middle oolitic period.
384 DESCRIPTIVE GEOLOGY.
In the north of England the contemporaneous bed is a calcareous
deposit, also containing corals, but (as at Malton, in Yorkshire) in-
cluding a considerable proportion of the fossil remains of
Fig. 192. shells, both bivalves and univalves. The bed never loses
its coralline character, and may, perhaps, represent an
imperfect coral reef, once extending from the south-west
of England to what is now the right bank of the Humber.
823. The Oxford clay is a very important member of
the Oolitic series, attaining a thickness of not less than
500 feet, and spreading over a great part of England,
more especially occupying the fen-districts in the counties
of Cambridge and Lincoln, which appear to be partly
caused by the union of this bed .with the Kimmeridge
clay, producing a wide expanse of flat and undrained
country. The same deposits are well seen at Weymouth,
and they cover an important part of the East Riding of Yorkshire.
The stratification throughout is nearly horizontal and undisturbed,
being conformable with that of the formations immediately above
and below it.
The appearance of the Oxford clay is that of a stiff pale blue
argillaceous bed, containing a large proportion of calcareous matter,
and a more or less abundant mixture of iron pyrites. Numerous
organic remains are found in it, which are sometimes preserved in
the clay itself, but more frequently form a nucleus, about which iron
pyrites have aggregated. Those preserved in the clay have been
generally found in a very rotten condition.
824. Although the Oxford clay in many places rests immediately on
the Cornbrash, and thus forms the basis of the Middle oolitic system,
this is not always the case, and there is often an intervening stratum
composed of calcareous sandstone abounding in organic remains, and
sometimes entirely made up of them. This bed is called the Kel-
loway rock, or Kelloway's rock, and its thickness varies from three
to five feet.
825. In the north of Scotland in various places, and in some of
the Western islands, small patches of Oolitic rocks have been traced
referable to this part of the period.
826. In Normandy the " Argile de Dives" is the true representative
of the Oxford clay, but in Switzerland the Middle oolites depart
more widely from the type of Western Europe. They are based upon
argillaceous limestone (Kelloway's Rock 1), and the most important
strata of which they are composed consist first, of an Oolitic ore of
iron, occurring in beds of marl and constituting about a third of
the whole thickness of the group, and, secondly, of a bed called the
Nerinsean limestone, corresponding to the Coral rag of our country.
Of these beds the one containing the iron ore is worthy of remark
LOWER OOLITES. 385
from its economic importance, and it has been much worked for a
long period. The Nerinaean limestone is also an interesting bed,
and is so called from a somewhat remarkable fossil with which it
abounds (Nerincea, a genus of univalve shells closely resembling, in
external form, the Turritella and Cerithium), and which is also
found not only in the Coral-rag but in the inferior Oolite in Eng-
land. (See nV. 155.) The Oxford clay is represented in the south
\ O / / JT
of Russia.
827. THE LOWER OOLITES. This extensive series admits of consi-
derable subdivision in the British Islands, but the details seem to be
rather of local than general interest, and though partially extending
to Normandy, are by no means universal in other parts of Europe.
The subdivisions are given in tabular form at the end of the last
chapter, but we must now describe them a little more at length.
828. The Corribrash (the uppermost bed) consists of a variable
thickness of clays and sandstones, which ultimately pass into a thin
rubbly stone, tough and occasionally crystalline, capping the escarp-
ment of the Lower oolites, but frequently absent, or appearing only
as an imperfect outlier. Its name is probably derived from the
excellence of the corn land which results from the decomposition of
the limestones, and their mixture with the sandstones and clay.
829. The Forest marble comes next in order. It consists of car-
bonate of lime, sometimes crystalline, and sometimes marly, includ-
ing about 25 feet of workable stone. Organic remains occur in it
in such abundance as often to make up the whole substance of the
stone. It is replaced in the north of England by sandstones and
shales, which are sometimes carbonaceous. The " Calcaire a poly-
piers " of Normandy is a coralline bed of the same age.
830. The Great oolite consists of a variable series of coarse shelly
limestones, alternating with beds of fine soft freestone devoid of fos-
sils, and admirably adapted for building purposes. The upper beds
afford a number of alternations of hard and coarse limestones, of a
yellowish-white colour and highly fossiliferous, some of which supply
good building material. Below these are shelly limestones and coarse
freestone ; and upon them rests the well known " Bath oolite." The
lowermost strata are fine-grained, scarcely Oolitic, and almost crys-
talline in their structure.
831. The Bradford clay is nearly of the same age as the Great
oolite, and is often the only representative of this part of the series.
It consists, usually, of a pale greyish clay, containing a small propor-
tion of calcareous matter, and enclosing thin slabs of tough brownish
limestone. Its thickness appears never to exceed sixty feet ; it is
often entirely absent, and at other times is so obscurely interstratified
with the underlying Fuller's earth, or the overlying Forest marble,
as to be scarcely recognisable.
c o
386 DESCRIPTIVE GEOLOGY.
The Bradford clay is particularly remarkable amongst the Oolites
for the abundance in it of a peculiar fossil, the Apiocrinite, whose re-
mains are usually found in groups,' the stems of the Encrinites being
attached to the thin bands of limestone interstratified with the clays.
832. In Yorkshire this part of the series consists of nodules of
ironstone over-lying hard blue and fine-grained limestone, the whole
series being non-fossiliferous, with the exception of fragments of
bone and the shells of marine mollusca, around which the iron-stone
nodules have formed. The hard limestones are extremely durable,
and have been found well adapted for various economical purposes :
more especially for works exposed to the beating of the waves, where
smoothness of surface is not required.
833. The Great oolite is separated from the Inferior oolite by
a series of marly beds, containing amongst them a particular kind of
clay used in the manufacture of cloth, and called " Fuller's earth,"
and also a thin bed of calcareous flag-stone, known as the " Stones-
field slate" The former stratum, the Fuller's earth, is chiefly found
at Odd Down, and on the side of Midford Hill near Bath ; but it
forms only a small and unimportant member (geologically speaking)
of the argillaceous deposit beneath the Great oolite. The Stonesfield
slate occurs in two beds, separated by a loose calcareous sandstone,
and is chiefly worked for flagstones and tiles, in quarries dug near
the village of Stonesfield in Oxfordshire. It has long been celebrated
for the singular nature of the organic remains found imbedded in the
fissile limestones which compose it, and beds somewhat similar, and
also foasiliferous, occur also at Colley Weston, a village near Stamford
in Northamptonshire. These latter, however, probably belong to a
higher part of the Oolitic series. The most remarkable of the Stones-
field fossils are the remains of marsupial quadrupeds, part of one of
which is shown in the annexed cut (fig. 193).
Fig. 193.
Jaw of Phascolotherium (Stonesfield slate).
834. The Inferior oolite includes a thickness of about 40 or 50
feet of freestone, forming the last of the series of the Oolitic lime-
stones, and occasionally employed to a great extent as building ma-
LOWER OOLITIC FOSSILS.
387
terial. In the north of England, however, these calcareous beds are
not present, and we find them replaced by sandstones and ironstone.
The proper base of the Oolitic system in the west and south of
England seems to consist of a slightly micaceous yellow sand, often
friable and incoherent, and slightly calcareous.
830. Of the lower members of the Oolitic system the Great oolite
is the most important, both in thickness and practical utility. It
is also the most interesting, for it contains a series of fossil shells
(chiefly found near Minchinhampton), perhaps the most extensive
that has yet been determined from any single bed in the Secondary
period. The Inferior oolite, at Dundry, Bridport, and Leckhamp-
ton, also exhibits a rich and extensive series of fossil shells of extreme
beauty, and in the most perfect preservation ; but these, as well as
the former, are for the most part still undescribed.
Fig. 197.
Fig. 196.
Jroup of
Fig. 1Q4. Terebratula globata.
,, 1Q5. Turbo costarius.
,, 196. Pleurotomaria conoidea.
,, 197. Ammonites striatulus.
The annexed diagram (figs. 194 197) represents some of the
species of univalve and bivalve shells common and characteristic in
this part of the series.
836. The representative of the Lower oolites in France is the
Caen limestone, which is of a well known pale creamy colour, and
has considerable range. It forms extensive plains in Normandy : it
388 DESCRIPTIVE GEOLOGY.
lies nearly horizontal, and is often exhibited in section on the banks
of rivers, from which it is worked in numerous horizontal galleries.
Associated with the limestone there is found silex, chiefly in the form
of black or yellowish flints, which are occasionally stratified, as in
chalk, but sometimes disseminated through the mass : in the upper
part of the group fossils are extremely abundant, and a very con-
siderable number of interesting organic remains of fishes and reptiles
occur in the lower beds, which probably correspond with our Stones-
field slate. The building stone is of admirable quality, soft in the
quarry, of a delicate uniform cream colour, and extreme fineness of
texture. It hardens by exposure, though not till after some years,
and has been very much used for many centuries, not only for the
churches and public buildings of Normandy and the north of France,
but also in other countries to which it is still exported in large quan-
tities. Below the limestone are three or four feet of yellowish irony
calcareous grit, very fossiliferous, and representing the Inferior oolite
of England.
The Lower oolites are represented in Germany and also in Russia,
and probably in the Caucasus. The greater part of the Alpine chain
is of the same date ; but in these cases the true Oolitic character is
generally absent.
837. In India, and especially in the north-western part of the
peninsula, there occur beds which appear to belong to the Oolitic
period. They include in Cutch several beds of coal. It is not im-
possible that other beds of the same age may be met with further
in the east of Asia.
838. America appears to contain hardly any beds belonging to
the newer part of the Oolitic period, but the older part is well re-
presented in North America in very interesting coal-bearing strata
near Richmond, Virginia, situated in a basin in altered and crystal-
line rocks, and containing many Oolitic fossils. The length of this
coal-field is about 26 miles, and its length varies from 4 to 12 miles
The beds consist of quartzose sandstones and coarse grit, the coal
being in the lower part. The coal is divided into two or three seams,
one of which is as much as 30 or 40 feet thick, but the thickness
is very irregular. This subject will be again adverted to at the
close of the present chapter ( 868).
South America contains Oolitic deposits, but it is still doubtful to
what part of the series they may be referred. They contain some
fossils of considerable interest.
5. The Liassic system.
839. The Lias of England consists of strata in which an argilla-
ceous character predominates throughout, but which are also remark-
able for a quantity of calcareous matter mingled with the clay, and
LIAS. 389
forming occasional bands of argillaceous limestone. A few beds of
sand also alternate with the clay and marl, and are sometimes mixed
with the latter, forming a marly sandstone of a white or greenish
colour.
Considered as a formation, the Lias in England may be traced in
a north-easterly direction from Lyme Regis on the coast of Dorset-
shire, where it is displayed along a line of cliffs extending for about
four miles, to the coast of Yorkshire near Whitby. It consists
throughout of the same beds of marly limestone, and from Glou-
cester northwards is remarkably regular, presenting an average and
nearly uniform breadth of about six miles, being covered up on the
east by the escarpment of the Oolites, and the New red sandstone
coming out from beneath it on the west. Its thickness is about 600
feet ; it is little disturbed, and has a regular dip, being conformable
to the underlying and overlying strata, except where it comes in con-
tact with the Carboniferous limestone in Glamorganshire and Somer-
setshire. It is also partially affected by the faults and disturbances
of those districts.
The Lias forms for the most part broad and level plains at the
foot of the Oolitic hills, only a slight escarpment being visible in the
southern counties, although this becomes more prominent on the
borders of Nottinghamshire and Leicestershire, where it forms a well-
marked range, known as the Wold hills. It also occurs occasionally
on the brow of tolerably steep escarpments in the Mendip hills ;
but its maximum of elevation falls short of 500 feet above the level
of the sea.
840. The subdivisions of the Lias are different in different parts
of England ; but on the whole there seem to be four principal
members.
The Upper lias, or Alum shale, is best seen at Whitby, and on
the Yorkshire coast, and it attains there a considerable thickness.
It consists of three distinct parts : the lower division including soft
shales, extremely fossiliferous, which are separated from the upper-
most series, also composed of incoherent slaty beds, by an interme-
diate stratum of hard shale, about 30 feet thick, containing a
quantity of the mineral called jet, and also, occasionally, large frag-
ments of the bituminised wood of coniferous trees. The jet itself is
but a peculiar form of carbon, and there can be little doubt that it
is of organic origin. It is in the upper shales of the Lias, both on
the coast of Yorkshire and at Lyme Regis, that there have been
found the most remarkable and interesting of those fossil remains
of extinct animals, for which the formation is so celebrated. The
presence of alternate bands of tolerably hard limestone and soft
shale, is usually characteristic of the Lias in the different parts of
England where it is most developed. The dark bluish-grey colour
390 DESCRIPTIVE GEOLOGY.
united with this singular riband-like structure, is more particularly
remarkable in the upper beds of the formation, and is well seen at
Lyme Regis, Whitby, and Barrow-upon-Soar, in Leicestershire.
841. The principal locality of the middle beds of the Lias is the
neighbourhood of Cheltenham, where the Marhtone of Dumbleton
hill is crowded with interesting organic remains. It is made up of
alternating layers of coloured clays and sands, which are occasionally
calcareous, and of beds of impure limestone.
This part of the series is also represented in the north of England,
where it has an average thickness of about 130 feet, and consists of
sandy shales, of which the upper portions are distinguished by the
presence of several bands of argillaceous irony nodules.
842. Lower lias shale. The great mass of the lower division of the
Lias is found in the middle of England, and consists of thick beds of
dark-coloured and finely laminated shale, in which are calcareous
bands and concretions. These form the base of the series, and gra-
duate downwards into a whitish sandstone, belonging to the upper-
most beds of the New red system. The transition is different again
in the south of England ; as at Lyme Regis marls of a light bluish
colour represent the upper beds of the New red sandstone and pass
into the Lias limestone by a succession of dark slaty marls, which
are overlaid by a number of grey calcareous beds, and these again
by other slaty marls of the upper series. The marlstone and Upper
lias shales are not present in this part of the deposit in their ordi-
nary form.
843. The lowest portion of the Liassic system occasionally consists
of a very thin bed, in some places entirely made up of the fragments
of fossil bodies (chiefly the remains of fish), but sometimes passing
into a white micaceous sandstone, still recognisable as the same bed,
although without fossils. This bed was first observed underlying a
small patch of Lias, near the town of Aust (situated on the left
bank of the Severn, nearly opposite the mouth of the Wye) j but it
Fig. 198. has since been recognised at
Axmouth, in Devonshire, and
in other parts of England far-
ther north, having a total range
of upwards of 100 miles. It
is rarely more than two or three
inches in thickness, but invari-
ably occupies the same geolo-
gical position, and is for the
Diadema seriale. mogt p arfc so exclusively COD1-
posed of organic remains, that a long period must have been required
for its formation. In some parts of the country, and especially in
Gloucestershire and Worcestershire the passage of the Lias into the
LIAS FOSSILS.
391
underlying beds of New red sandstone is marked by the presence
of calcareous flagstones, called Lower lias limestones; and these
usually alternate with laminated shales, the whole in that case
forming together the lowest deposits of Lias.
Fig. 199.
Fig. 203.
Group of Lias Fossils.
Fig. 199. Spirifer Walcoti. Fig. 202. Plagiostoma giganteum.
,, 200. Piicatula spinosa. ,, 203. Ammonites catena.
,, 201. Pecten Lugdunensis. ,, 204. Belemnites pistilifonnis.
844. On the continent the Lias is frequently found, and the upper
beds resemble those developed in England ; the middle, however, are
usually more calcareous, and the lower more sandy, and these latter
sometimes, as in Belgium, pass insensibly into the Upper new red
sandstone. The town of Luxemburg is built upon a hard sandstone
of this kind, and these beds pass into the rock called Arkose, a pecu-
392 DESCRIPTIVE GEOLOGY.
liar and often metalliferous metamorphosed deposit, occurring where
the Lias sands come in contact with crystalline rocks. Fossils have
been found in South America, and also in northern India, attributed
to the period we are now considering.
845. The Lias is a formation exceedingly rich in fossils ; and
amongst them are representatives of all the principal natural groups.
Corals, however, are exceedingly rare and of small size. Encrinites
are numerous and abundant, especially the Pentacrinite, which at-
tached itself to floating wood. Radiated animals of other kinds cha-
racterise parts of the deposits, and of these the Diadema (fig. 198),
is an example. Insects and Crustaceans have been frequently found.
Star-fishes are common in the marlstone.
Both univalve and bivalve shells of various kinds are characteristic
either of the whole deposit, or of different beds. The Spirifer (fig. 199)
is one of the later species of a genus represented far more abundantly
in more ancient deposits, while thePlicatula (fig. 200), and Plagiostoma
(fig. 202), are among the ancient representatives of more recent forms.
The Pecten (fig. 201), is an example of similar kind ; and the Am-
monite and Belemnite (figs. 203, 204) are eminently characteristic
cephalopodous shells, infinitely abundant during the Lias, and
scarcely less so for great part of the Oolitic period. Above 170
species of mollusca have been described from British localities only,
of which as many as 70 are Ammonites.
Fig. 205.
Restored skeleton of Pterodactyl.
846. Fishes' remains are common in some parts of the Lias, and as
many as 60 species in all have been described : of these many resem-
bled the shark, but none seem to have attained very gigantic propor-
tions. This, however, was not the case with the Reptiles, which
during the period in question, were equally remarkable for their
large size, voracious habits, and incredible abundance. Many spe-
pies belonging to natural orders of these animals long since lost,
TRIASSIC SYSTEM. 393
were then widely dispersed ; and many other species existed of genera
now common in distant parts of the world. The flying reptile figured
in the annexed diagram (fig. 205) is a striking instance of anomalous
structure. The swimming, and indeed strictly marine monsters
named Ichthyosaurus and Plesiosaurus (fig 206) are other examples,
Fig. 206.
Restored outline of Plesiosaurus.
and have been frequently described. The remains of species referred
to no less than twenty-three genera of these animals have been found
in England alone.
6. The Upper new red sandstone, or Triassic system.
847. The deposits belonging to this system are so named from the
tripartite division of them observed on the continent of Europe where
a calcareous rock of some importance (the Muschelkalk) intervenes
between two arenaceous rocks called respectively Keuper and Bunter-
sandstone. In England the absence of the limestone leaves no means
of distinguishing between the two sands, which are only spoken of as
distinct owing to the presence of some doubtful fossils, and a more
marly character, combined with beds of gypsum and rock-salt, in the
upper part. The British series is designated Upper new red sand-
stone.
848. It is in Cheshire, the southern part of Lancashire, and the
northern part of Shropshire, which together form an extensive and
rich plain, watered by the Dee, the Mersey, and the Weaver, that the
uppermost beds of the New red sandstone are chiefly developed ; and
by a minute examination of these beds, and those of Warwickshire,
the saliferous marls have been identified with the uppermost strata
of the foreign Triassic system. Throughout this range the beds are
nearly horizontal, the dip rarely exceeding ten or twelve degrees, and
being constantly towards the east, or a few degrees north or south of
that point. They are, however, affected by some important faults.
The whole district abounds with salt springs, which are more espe-
cially plentiful in Cheshire ; and in that county, also, there occur
extensive masses of rock-salt in a solid state, their total thickness
amounting to not less than sixty feet. These alternate with beds of
gypsum ; with numerous bands of indurated clay of a blue, red, or
394 DESCRIPTIVE GEOLOGY.
brown colour ; and with sandstones, frequently marly, and of a red
colour.
849. The red marl district with brine springs is continued south-
wards into Worcestershire, and northwards into the valley of the Eden,
and the same part of the formation extends also eastwards, occupy-
ing for the most part the plains through which the Humber and its
tributaries make their way to the German Ocean. In Somersetshire
and Devonshire similar sandstones recur, and lie unconformably,
overlapping the inclined edges of the older rocks, or abutting against
them, but uniformly composed of the same materials, remarkable
throughout for the ochraceous colour pervading them. Between Sid-
mouth and Seaton in Devonshire, the red marls contain gypsum in
abundance, and near Teignmouth the cliffs, which are of considerable
height, consist of alternations of argillaceous beds of sandstone and
of conglomerate.
850. The beds which are lowest in position of the Upper new red
sandstone, are chiefly found in the middle of England, and consist of
thick masses of whitish soft sandstone. In some places (as in
Staffordshire) these are surmounted by conglomerates, composed of
rounded pebbles of quartz rock, and other fragments, chiefly of Silu-
rian rocks and Old red sandstone. The total thickness of this part
of the formation is considerable, but has not been accurately calcu-
lated. It is only to be distinguished from the overlying saliferous
marls by small differences of mineral character.
851. The whole of the Upper new red sandstone of England
bears evident marks of its marine origin, even if the occurrence of so
large a quantity of salt associated with it did not place the matter
beyond a doubt. The almost total absence of fossils is, however, a
very remarkable phenomenon, and one which is not satisfactorily
accounted for, either by the prevailing sandy character of the de-
posit, or by the quantity of oxide of iron distributed through it.
Owing to the nature of the alternating marls and gypsum of this
series of strata the vegetable soil arising from its disintegration is
extremely fertile ; and in the greater part of the county of Devon-
shire, in the valley of the Severn, and yet more strikingly in the
agricultural districts of Warwickshire, Worcestershire, Staffordshire,
and Cheshire, many peculiarities may be observed characterising
the formation.
852. The development of the Trias in France and Germany is
different from that just described, and the general character of the
different deposits will be seen by the following division.
The Keuper, the uppermost division, called by the French marnes
irisees (variegated marls), has been identified with the upper mem-
bers of the New red sandstone formation in our own country.
The group usually consists of a numerous series of mottled marls
TRIASSIC FOSSILS.
395
of a red, greenish-grey, or blue colour, which pass into green marls,
black slaty clays, and fine-grained sandstones. Throughout the
series common rock-salt and gypsum are abundant, but the organic
remains of animals are extremely rare. Of plants, however, a con-
siderable number are preserved in some localities, and a species is
represented in the annexed cut (fig. 207), where also will be found
representations of two of the most characteristic fossils of the Mus-
chelkalk, or limestone of the period.
Fig. 209.
Fig. 207.
Group of Triassic fossils.
Fig. 207. Voltzia heterophylla.
,, 208. Encrinites moniliformis.
,, 209, 210. Ammonites (Ceratites) nodosus.
853. The Muschelkalk is a compact limestone of a grey or greenish-
grey colour, and commonly contains in great abundance the remains
of shells and fragments of radiated animals and fishes. It rests con-
formably on the underlying sandstones and either forms an escarp-
ment, or is exhibited in a range of high table-land, such as may be
seen in the north of Bavaria. The upper beds are, on the whole,
more slaty than the lower ones, but still contain compact limestone
396 DESCRIPTIVE GEOLOGY.
bands, characterised by the usual fossils. In the neighbourhood of
Basle, and in some parts of Wurtemberg, the lower part of the form-
ation consists of a yellowish coloured limestone, alternating with thin
bands and veins of gypsum, and contains a considerable quantity of
rock-salt, differing in this respect from the contemporaneous forma-
tions in other districts. Lastly, the muschelkalk is occasionally a
bituminous rock, and emits a fetid, disagreeable odour when rubbed
or struck with a hammer.
854. Among the remarkable fossils of this rock are remains of
an animal whose footmarks are found in the New red sandstones of
England and Germany, and which has been called Labyrinthodon
Fig. 211.
Restored outline of Labyrinthodon.
(fig. 211). From the form of the footmarks, which resemble those of
the human hand, the animal has also been called Chirotherium (clieir
a hand, iherium an animal). Many species of fishes, as well as shells
and some other reptiles, appear to have characterised this part of
the period.
855. The Ores Bigarre, or Bunter Sandstein, is a fine-grained solid
sandstone, sometimes white, but more frequently of a red, blue, or
greenish tint. The structure of the lower part is tolerably close-
grained, and sufficiently compact to form a good building stone j but
the uppermost strata are fissile and incoherent, and pass into an
earthy clay containing gypsum. The intermediate portion is com-
pact, like the lower, but its structure is that of a conglomerate, and
it is used for making millstones. In many districts the Bunter
Sandstein contains numerous remains of fossil plants, and also of
marine shells ; but the latter are rare and confined to particular
localities.
The sandstones and marls of this part of the series are spread
over an extensive tract of land in Western Europe, more particularly
in France, and in South-western and Central Germany. They are
found in France, on the flanks of the Vosges mountains, where they
overlie the Lower new red sandstone (there called " gres de Vosges"},
and again in several parts of Central France, and in the Sub- Pyrenees.
DISTURBANCES OF THE SECONDARY EPOCH. 397
856. The whole series of the Secondary rocks may be regarded as
having been deposited in open seas, which were in some places deep,
in others shallow, and generally dotted over with islands. No con-
tinuous land forming continental masses seems to have prevailed in
any extensive districts in which rocks of this age are now observed,
but abundant evidence exists of the near vicinity of considerable
islands, some of them probably, especially near the present lower
Oolite deposits of England, having considerable mountain ranges.
857. The crystalline rocks of the Secondary period are neither few
nor unimportant. On the north coast of Ireland, and in the southern-
most of the western Islands of Scotland, large quantities of basalt
have been poured out, producing a marked effect upon the chalk,
and probably erupted during the period immediately succeeding the
deposit of that bed. In the New red sandstone of England there
are numerous localities where the older rocks have been forced
through, and some where the sandstone rocks are penetrated by dykes
of crystalline rock, resembling granite and Syenite. The granites
and slates of Charnwood Forest in Leicestershire, must be of early
Secondary origin, and many of the highly altered rocks of the Alps
may safely be referred to the period. It is not unlikely that the
date of change of the metarnorphic schists and the porphyries of the
great mountain chains of Central Asia and the two Americas, are
also Secondary. So far as England and Europe are concerned there
is, however, reason to suppose that the whole Secondary epoch was
marked by almost continuous depression.
858. The elevations of this period, according to M. Elie de Beau-
mont, were four. The first took place between the deposit of the
Lower new red sandstone and the Trias, and is considered to have
had a direction S. 21, W. and N. 21, E., or nearly that of the
Western Alps already described ( 779). It is called the system of
the Rhine, and is marked by the cliffs on the borders of the Rhine
between Basle and Mayence.
859. The next system is that of the Thuringian forest, and runs
W. 40, N. and E. 40, S. It is seen in the chain of mountains
from which it is named, and which extend also into the Bohmerwald,
forming the natural frontier of Bohemia and Bavaria. In France
it is marked in the south-west part of the Vosges mountains and in
the west of the same country in Brittany. It is supposed to have
taken place between the Triassic and Oolitic periods.
860. The third elevation is that of the Cote d'Or, nearly at right
angles to the former, and running W. 40, S. and E. 40, N. It is
extremely well-marked in France and in the Erzgebirge, and seen
also in the cliffs of the Vicentin. It is of the age between the
deposit of the Oolites and the commencement of the Lower greensand.
861. The fourth and last system of this period is that of the Monte
398 DESCRIPTIVE GEOLOGY.
Viso, seen in the Alps of Dauphigny. It runs N.N.W. and S.S.E.,
being nearly coincident with that of Tenare the most modern
system of elevation, and one already described in a former para-
graph ( 781). The disturbances of this part of the period are
supposed to have taken place between the deposit of the two princi-
pal divisions of the Cretaceous series. This last of the great systems
of the Secondary period is supposed to have determined the principal
direction of the shores of Italy, and some of the principal mountain
ridges of Greece.
862. " The distribution of the oceans during the Secondary epoch
cannot be very definitely or surely discerned ; but enough is clear to
reveal a condition of things still more remote in character than that
of the Tertiary epoch from what is in existence now. The Tertiary
seas, whose extent has been already described, were, during this older
period, in close and free communication with each other ; for the
elevation of the Secondary rocks, especially in the old continent,
tending to narrow all their shallow channels, diminished the number
of their points of contact, and still more their extent. The form-
ation and upheaval of all the rocks of this group evolved this result;
but perhaps their operation is most easily seen in the case of the
Jurassic and the cretaceous beds. The lower members of the Secondary
group defined the contours of many basins in Central Europe on the
banks, for instance, of the Rhine ; between the Harz, the Erzgebirge,
and the Thuringian forest ; in England, Poland, Russia, &c. They
also separated the great Siberian basin from the seas of Europe, and
probably diminished the magnitude of the Chinese inland seas.
Humboldt found them in the valley of the Orinoco, and Schomburgk
in the interior of the crystalline district of Guayana. By the Jurassic
formation, on the other hand, distinct walls of separation were esta-
blished in France, Switzerland, in the south-west of Germany, in
Northern Hungary, Spain, and the north of Africa ; and new shapes
were imposed on the basins of Siberia, China, and Central Asia.
Thus emerged the cretaceous masses, completing everywhere the
contours of the Tertiary basins, particularly in three South European
peninsulas ; at the same time isolating Sahara from the Mediterra-
nean, forming boundaries to Arabia, Mesopotamia and Southern Per-
sia, the coast of Tranquebar, the centre and north-east of Asia ;
perhaps China and Borneo, as well as Australia. They are likewise
found on the two slopes of the Alleghanies, on the south-east slope of
the Rocky Mountains, in several parts of Mexico and Colombia, and
among the Andes of Peru and Chili."*
* Johnston's Physical Atlas, ante cit.
OOLITIC COAL-FIELD. 399
Note on the coal-fields of the Secondary epoch.
863. In addition to the various valuable materials obtained from
the Oolitic and other Secondary deposits already noticed, there are
also found in it bands of coal, lignite, and other mineral fuel, suffici-
ently important in some districts to be worthy of more than passing
notice. These are, indeed, of comparatively little value in England,
where the rocks of the older or Palaeozoic epoch are so much more rich
in similar deposits, but elsewhere they form important sources of mine-
ral wealth. We shall, therefore, offer here a few remarks on the
Kimmeridge coal, the Brora coal, the Oolitic coal-field of Yorkshire,
the coal-fields of Cutch in India, of the same geological age, and
lastly, the Richmond coal-field of Eastern Virginia, in the United
States of North America. Corresponding deposits, also Secondary,
but of inferior importance, are found in Piedmont, Lombardy, the
Alps, France, and Silesia, and also in the Andes.
864. The Kimmeridge coal is nothing more than a highly bitu-
minous shale of rather high specific gravity (SG=1'319). It is of
dark-brown colour, and without lustre, effervesces slightly with acids,
contains no iron pyrites, and burns readily with a yellowish, rather
smoky, and heavy flame. It has been used for pottery and other
purposes, but is not much worked at present. Its position is in the
Kimmeridge clay. It is of very little value, and does not extend
widely.
865. The Brora coal is of doubtful geological age, but has been
generally considered as more nearly allied to the lower than to the
upper part of the Oolitic series. It has been mined for more than
250 years, and appears to consist of two workable, and several smaller
seams, the main seam being 3^ feet thick, and worked in one pit at
a depth of 250 and in another at 338 feet. The quality of the coal
is bituminous, it has a cubical fracture, and burns to a white ash.
The total quantity is not large, but upwards of 70,000 tons were
obtained from one pit between the years 1814 and 1826.
866. The Yorkshire Oolitic coal-field contains only a few thin
seams of carbonaceous matter, of very irregular quality, but has been
worked for more than a century, and has yielded a good deal of coal.
The beds overlie the Lias near Whitby, and have been traced to some
distance in the interior, the area being estimated at about 100,000
acres. Some parts of the deposit contain a coal which burns freely,
with comparatively little ash ; but the greater portion can only be
used for inferior purposes.
867. In India there are several coal-fields of moderate dimensions
all of them very imperfectly developed, but belonging, it would
seem, to the Secondary epoch. The most distinctly known is an
area of about 200 miles in length, averaging 20 miles in breadth
400 DESCRIPTIVE GEOLOGY.
in the north side of the Gulf of Cutch. The formation consists
of sandstone and shale, with bands of iron ore and seams of coal,
which do not exceed 18 inches in thickness. The quality of the
coal is described as good ; it ignites quickly, and burns with a
bright flame.
868. By far the most important, if not the only really important
beds of coal of the Secondary period, are those of Richmond, Eastern
Virginia, United States, of which a section is represented in the an-
nexed diagram. The whole productive area has been estimated at
Granite. Deep workings, Granite.
Section of the Bituminous Coal-field, Richmond, Eastern Virginia, U.S.
about 185 square miles, but the depth, except at the outskirts, is
not known. The coal occurs at the base of a large series of granit-
oid sandstones, called psammite, and reposes almost directly on
granite. The whole of the central area is covered by conglomerates.
The number of coal-seams is at least three, the uppermost being the
most important; the total thickness of coal varying from 11 to 40
feet, according to the inequalities of the floor. The quality of the
coal is bituminous and good. It has been long and extensively
worked, Philadelphia alone taking 10,000 tons annually, and it is
found valuable in the manufacture of gas. Several accidents have
happened in working it from explosions of the gas. Some of the
mines contain water, but others are dry.
869. " The coal of Eastern Virginia, although derived from a different vegetation
from that of the ancient carboniferous period, resembles very closely the older coal in
structure, appearance, and composition. That of the Blackheath mine has usually a
highly resinous lustre and conchoidal fracture, and always contains at least as large a
proportion of gaseous or volatile ingredients (hydrogen, oxygen, and nitrogen) as the
coal of the palaeozoic rocks of the United States.
" The coal is also divided into horizontal layers of slight thickness parallel to the
planes of stratification, as in the older kinds of coal. Sometimes these layers consist
alternately of highly crystalline and resinous coal with a bright lustre, and of other
portions exactly resembling charcoal in appearance."
The following is an analysis by T. H. Henry, Esq., of the Richmond coal, dried at
250 Fahr.: Moisture 1 to 1 percent; Carbon 80'38; Hydrogen 4'08; Oxygen
and Nitrogen 6'19; Ash 9 '35.*
* Lyell on the Coal-fields of Eastern Virginia. Quart. Geol. Journ. vol. iii. p. 26l.
401
CHAPTER XVI.
ON THE ROCKS AND FOSSILS OF THE NEWER PORTION OF THE
PALAEOZOIC EPOCH.
870. The older of the three great epochs which have been assumed
by geologists is understood to include a large number of very dis-
tinct deposits, many of them exceedingly thick, and for the most
part traceable over wide areas by rocks marked with very similar
geological and mineralogical characters. The series may be grouped
into about five parts, of which the two of newest date are called
Upper or newer, and the two of oldest date, Lower or older. The
term Palceozoic being applied to the epoch generally, marks the
relative antiquity of the period taken as a whole. The following
are the five principal subdivisions :
rl. MAGNESIAN LIMESTONE, or PERMIAN SYSTEM.
NEWER PALEOZOIC { 2 CARBONIFEROUS sySTKM .
MIDDLE PALAEOZOIC 3. DEVONIAN, or OLD RED SANDSTONE SYSTEM.
r 4. UPPER SILURIAN SERIES.
NEWER PALEOZOIC {5. LowKR SILURIAN SER1ES .
1. The Magnesian limestone or Permian system. >
871. The rocks which immediately underlie those of the Triassic
or Upper or new sandstone series of England, offer a close resem-
blance to the latter in mineral character, but are covered unconform-
ably by them. Elsewhere, however, and especially in Russia, a large
group of deposits of this date exists, and is marked by distinct pecu-
liarities. The abundance of carbonate of magnesia is a character-
istic feature of part of the series, and thus the name "magnesian
limestone" has been generally applied to designate the group.
872. The following are the chief sub-divisions of the system :
1. Magnesian limestone series.
ENGLAND.
Grey thin-bedded limestone. *
Red marl and Gypsum.
Magnesian limestone and magnesian f
conglomerate.
GERMANY.
I Letten.
Zechstein. \ Stinkstein.
* Rauwacke".
j Argillaceous schist.
Shaly beds. 1 Bituminous schist.
Arenaceous schist.
2. Loiver new red sandstone series.
Marly beds, with thin bands of com-
pact and shelly limestone.
Lower new red sandstone.
Rothe-todte-liegende.
D D
402 DESCRIPTIVE GEOLOGY.
873. The Magnesian limestone, and the beds associated with it,
rest immediately on the upper strata of the carboniferous system,
and may be traced from Nottingham to the mouth of the Tyne con-
tinuously, but not rising to a high level, except in part of the county
of Durham, where they are cut off by the coast line. The rock,
being for the most part easily disintegrated, has suffered much from
denudation, and several outliers, or portions of the strata completely
isolated from the principal mass, are seen from point to point beyond
the edge of the formation.
874. The uppermost beds of the series, which overlie the true mag-
nesian limestone, consist of gypseous marls of variable thickness, and
sometimes occupy the base of a low escarpment, formed by a grey,
thin-bedded limestone (the highest bed of the series), which dips into
the plain of the New red sandstone. The thinness of the upper-
most beds is characteristic, and they often pass into mere laminae,
with plates of marl interposed between them. Organic remains are
not common, and when they do appear, they are obscure.
875. The deposit of magnesian limestone which comes next in
order, occupies by far the greater part of the escarpment overhanging
the coal-measures. It is extremely complicated in its structure, pre-
senting more varieties in the arrangement of its subordinate parts
than any newer formation. Considered, however, generally, the lower
part is usually of an open arenaceous texture, and of red colour,
being made up of a congeries of small crystals, coated with oxide of
iron. The crystals, loosely thrown together, as it were, in the lower
beds, occasionally become more closely packed and of paler co-
lour, and a little higher in the series form a tolerably compact rock,
and sometimes a stone of such close grain as to be much used for
troughs and cisterns. The magnesian limestone in this state is called
Dolomite, and the crystalline or semi-crystalline structure of the
mineral is usually predominant, although in some quarries a com-
pact form of it is seen, associated with thin beds of crystalline rock
of loose texture, of the same kind as those described above. The
compact dolomite has a flat conchoidal fracture, and is translucent
at the edges ; but it is very irregular in structure, and passes by
insensible gradations into other varieties. Some account of those
masses of dolomite capable of being used for buildings and other
economical purposes will be found in a previous chapter (Chapter
XI. 544), where also analyses of magnesian limestones are given
and compared with the composition of other limestones.
876. The magnesian limestone occasionally puts on other and very
different forms : at one time, for instance, we find it made up of
laminae parallel to the plane of stratification ; at another, of earthy
masses, which are sometimes hard and regularly bedded, and some-
times unstratified. A remarkable peculiarity of structure in this
MAGNESIAN LIMESTONE. 403
bed has sometimes also obliterated the lines of deposition so that a
section of the rock exhibits a mass of crystalline, compact, cellular,
and earthy materials rudely blended together, and passing into each
other without order or arrangement.
877. But in the apparent confusion thus produced the minute
grains which enter into the composition of the rock are occasionally
well defined and of spheroidal shape. The mass, in such a case, ap-
pears Oolitic, and there are several localities in the southern part of
Yorkshire where Oolitic magnesian limestone is worked as a free-
stone, and resembles not a little the building stone obtained near
Bath from the Secondary rocks. Like this latter stone it cuts
readily in the quarry, and hardens on exposure to the atmosphere ;
but the grains are less uniform in size, possess a glimmering lustre,
and are hollow and made up of concentric laminae.
878. Turning now to the magnesian limestone as exhibited in the
south of England, we shall find the New red sandstone of Bristol
succeeded by a dolomitic conglomerate, made up of angular or
slightly worn fragments of an underlying limestone, cemented by a
red or yellow magnesian paste.
This deposit fills up the hollows and irregularities of the lower
and older rock, and may be seen in the precipitous cliffs on the
Avon. It is undoubtedly the representative of the magnesian lime-
stone of the north of England.
879. The magnesian limestone series may be traced in the north
of France and in Burgundy, but is most fully developed at Mansfeld
in the Thuriugian forest, in the district of the Hartz, and in Fran-
conia. Throughout the south of France it appears to have no re-
presentative, and is most likely altogether absent. When most
perfectly expanded, the whole series is divisible into two groups, the
lower one for the most part argillaceous, and the upper calcareous,
and the series then rests immediately upon the conglomerates of the
Rothe-todte-liegende.
880. The upper or calcareous portion in Germany is called Zech-
stein, and is chiefly a compact limestone, but the highest beds are
marly, consisting of, 1st, a greyish, bluish, or greenish clay, called Let-
ten, often containing rolled fragments of dolomite and crystals of
gypsum. This reposes on (2) a fetid limestone called Stinkstein,
which is a compact or granulated rock, of a blackish-brown or green-
ish colour, and extremely bituminous, giving out an offensive odour
when struck or rubbed. The lower bed (3) of the Zechstein is called
Rauwacke, and consists of a hard but cellular magnesian limestone,
abounding in long, irregular, and narrow cavities, which are most
numerous when the bed attains a considerable thickness, but are al-
most obliterated in the thinner and more compact portions. The
whole thickness of the Zechstein is rarely more than 20 or 30 yards.
404 DESCRIPTIVE GEOLOGY.
881. In the zechstein and the beds associated with it, there are found occasionally
several minerals, amongst which may be enumerated white crystallized carbonate of
lime, crystallized sulphate of lime or gypsum, quartz, and mica. Both the sulphuret
and carbonate of copper, also, occur together with galena in mineral veins traversing
the formation.
882. Of the schistose beds which form the base of the magnesian
limestone series, the lowest is sandy, and forms a kind of transition
from the underlying sandstones. It is of no great thickness, and is
succeeded by a bituminous band, remarkable for great uniformity
both of mineral character and fossil contents, being traceable over a
considerable district in Germany, and forming an excellent geologi-
cal horizon for an extent of, at least, 250 miles. According to M.
D'Aubuisson, one-tenth part of the mass of this bed consists of
bitumen and carbon : and, although not more than a foot in thick-
ness, it contains so considerable a quantity of iron and argentiferous
copper pyrites as to be worth working as an ore, whence it has
received the name of Kupfer-schiefer, or copper slate.
This bituminous schist is also remarkable as containing, in great abundance, the
nearly perfect fossil remains of a large number of extinct species of fish. By means
of these the bed has been identified with the contemporaneous formations in other
countries ; and as the remains of reptiles have also been discovered, associated with
the fragments of fish, the Kupfer-schiefer is thus brought into relation with the
Bristol dolomitic conglomerate, as well as with the Magnesian limestone of Durham
and the Permian System of Russia.
883. The fossils of this part of the series are more abundant than
those of the lower bed though still comparatively rare, and the beds
are poorly provided, not only in species but individuals. On the
whole, however, these remains mark a condition of things more
closely resembling that of the other Paleozoic deposits than those
of the Secondary period.
213. The annexed figures of Brachiopodous
shells, (fig. 213, 214) are characteristic of
the magnesian limestone, and with them
occur several fragments of fishes and some
reptilian remains of much interest. The
whole number of species determined when
Sir R. Murchison first proposed the name
Permian from the Russian equivalents of
the series, was 166 : and although many
have since been added, they do not alter
the general character of the fauna, which
presents a remarkable preponderance of
Magnesian Limestone Fossils. i u >
Fig. 213. Productus aeuleatus. fisheS remains.
214. Spmfer undulatus. 884t The upper mem bers of the Permian system
are far more interesting than the lower portion ; but it has not yet been very clearly
determined what is the cause of the presence of so large a quantity of carbonate of
magnesia in these deposits, while this mineral is elsewhere so rare. Perhaps the best
suggestion is that lately made by Dr. Forchammer, who attributes the dolomination or
LOWER NEW RED SANDSTONE. 405
infiltration of carbonate of magnesia to numerous springs containing that mineral
poured out during or subsequently to the deposition of the carbonates of lime which
form the base of the whole deposit.
885. The lowest bed of the magnesian limestone group is called
from its lithological character and relative geological position " the
Lower new red sandstone ;" but it might very fairly be associated with
the Upper coal-measures, for it contains numerous remains of extinct
vegetables not to be distinguished from species found throughout
the carboniferous system. It differs somewhat, however, from the
coal grits in mineral composition, being more discoloured with oxide
of iron, besides being chiefly made up of a conglomerate in which
quartz and decomposed granite abound. This conglomerate, although
in its lower portion exceedingly coarse, passes upwards into a fine-
grained sandstone, and so by finer sands mixed with marl shows a
gradual transition to the upper and marly beds. Beds of freestone
are sometimes, but rarely, found alternating with the fine sands and
clays of this division ; and the mass is altogether very irregular
both in thickness and extent, appearing to have presented an un-
even surface at the commencement of the deposit of the more recent
magnesian limestones, and in some places to have undergone con-
siderable degradation before those beds were superimposed. The
irregularity thus described as affecting the lower strata must have
been owing, in all probability, to subterranean movements disturb-
ing the bed of the ocean- during the period of their deposition. The
marls associated with the fossiliferous bands in the county of Dur-
ham, are also sometimes bituminous, and traces of bitumen occur in
thin-bedded compact limestones of the same geological date.
886. The Lower new red sandstone, or Rothe-todte-liegende, as ob-
served in Germany, is perfectly similar, in almost all respects, to the
contemporaneous beds in our own country, being made up of coarse
conglomerates, alternating with marls and shaly beds, the conglome-
rates being generally composed of fragments of the neighbouring
crystalline rocks, cemented by a fine ferruginous, and sometimes
argillaceous sandstone.
887. In France this deposit is exhibited wrapping round the old
rocks which form the central axis of the Vosges. It consists of a
coarse incoherent sandstone, generally of a red but sometimes of a
bluish-grey colour, alternating with shaly and micaceous marls, the
whole formation being extremely variable, both in its mineral cha-
racter and in the extent of its development. It passes insensibly
into the upper beds called the " grfo des Vosges? or Vosges sand-
stone, there being no intermediate bed of magnesian limestone.
888. The Permian system of Russia exactly corresponds to the
Magnesian limestone and Lower new red sandstone of our own
country ; but it has been judged advisable to give a distinct name
406 DESCRIPTIVE GEOLOGY.
to the continental group, and the district in which the rocks are
most perfectly exhibited being included in the ancient kingdom of
Permia, that name has been selected, for reasons similar to those
which had induced Sir R. Murchison, on a former occasion, to apply
the term " Silurian formation" to a group typically exhibited in the
region of the ancient Siluri.
The Permian district extends for about 700 miles from north to
south along the western or European flanks of the Ural chain, and
for nearly 400 miles between those mountains and the river Volga.
The strata within this area are described as lying in an enormous
trough of carboniferous limestone, and, although occasionally thrown
into anticlinal axes of some length, are often traceable for great dis-
tances, without any break or interruption of the sequence,
889. The Permian rocks of Russia consist of a great number of
distinct strata of very varied lithological character. They are com-
posed, for the most part, of white limestone with gypsum and rock
salt, of red and green gritstones with shales and occasionally copper
ore, and of magnesian limestones, marlstones, conglomerates, &c.
The whole series is fossiliferous, and contains the remains of extinct
species of animals and vegetables, greatly resembling those of the
Carboniferous period. In the Russian beds, also, there have been dis-
covered reptilian remains like those of the Bristol magnesian conglo-
merate, and fish identical with the species from Durham and from
Mansfeld in the Thuringian forest.
2. The Carboniferous system.
890. The deposits associated under this name include some of the
most important accumulations of mineral wealth met with in the
earth's crust, and they require, therefore, careful and somewhat
detailed notice. There are three principal divisions, designated as
follows, and we proceed at once to the consideration of these.
1 . COAL MEASURES.
2. MILLSTONE GRIT.
3. CARBONIFEROUS LIMESTONE.
As developed in England, the Carboniferous system consists of an
extended series of highly fossiliferous limestones, alternating with
sandstones and shales, the latter frequently containing a large num-
ber of the remains of vegetables, which in some cases are so abun-
dant as to form valuable seams of coal. The relative position of the
different rocks with respect to the coal is not constant. The pre-
sence of carbon is the characteristic feature both in the upper and
lower divisions ; and throughout the whole series there occur at
intervals bands of carbonaceous matter only occasionally of import-
ance as coal, but sufficiently indicative of the vicinity of land clothed
with vegetation.
COAL-MEASURES.
407
Fig. 215.
891. The Coal-measures. This large and interesting group of
deposits, remarkable for containing vegetable matter in an almost
crystalline state, frequently extracted for the purpose of fuel, and
obtained from various parts of our own and other countries, demands
our first attention. It may be described generally as offering a
repeated succession of argillaceous and sandy bands, the former ge-
nerally laminated and called shales, and
both coloured with iron and carbon :
the whole alternating with bands of
nearly pure carbon, varying in thickness
from a fraction of an inch to 30 or 40
feet, or even much more, and amounting
sometimes in number to much more than
100, crowded throughout with fossil
remains of vegetables, and containing
also a few shells and other indications
of animals. The extent to which the
whole series is developed varies much in
different districts, but in South Wales has been calculated by actual
sections to amount to 12,000 feet, the sandstones greatly prepond-
erating, while in Nova Scotia there are nearly 15,000 feet of depo-
sits, apparently of the same date, and none of them in either case
exhibiting direct evidence of marine deposit.
Calamites cannseformis.
Fig. 216.
Fig. 217.
Fig. 218.
Group of fossils from the Coal-measures.
Fig. 216. Sphenopteris Hamighausi.
,, 217. Stigmaria ficoides.
218. Tooth of Megalichthys Hibberti.
892. The uppermost part of the coal-measures generally consists
of gritstones, and does not afford any large proportion of carbona-
ceous matter, so that where the development of the series is most
408 DESCRIPTIVE GEOLOGY.
complete, as in the cases already alluded to, there are some 2,000 or
3,000 feet of the whole series chiefly arenaceous and quite unpro-
ductive of coal. These are sometimes called " upper coal grits," and
are often rather barren of fossils. The middle and lower part of the
series abound in remains of plants, and almost every coal band re-
poses on clay, containing a vast multitude of the rootlets of a tree
(Stigmaria), of which some mention has been already made ( 676).
Ferns (figs. 132,216) and reed-like plants (fig. 215) are also found
in great abundance throughout these deposits, and in a remarkable
fresh-water limestone near Edinburgh, considered to belong to the
base of the true coal-measures, the teeth and jaws of a large and
remarkable fish are often met with, and may be mentioned as cha-
racteristic of the rocks of the carboniferous period. This fish has
been called Megalichthys (megale great, ichthys fish), and one of the
teeth is represented in the diagram (fig. 218). Other fossil remains,
and among them the foot-prints of reptiles, have been recognised in
foreign beds of the Carboniferous period, though not yet observed in
the rocks of this country.
The Megalichthys is one of those genera which may rank amongst the singular
links connecting two great natural divisions, which are apparently so strongly
marked, and separated from one another so widely, as to offer scarcely any points of
resemblance. It combines with many of the characters of a true fish, many close
and striking analogies with reptiles ; and the teeth more especially, so closely
resemble those of some crocodilian animals, that when first discovered they were
immediately referred to that class ; and not only the teeth, but the scales also seemed
to indicate the same affinity.
893. The coal-fields of Great Britain are affected by many exten-
sive and complicated faults. The way in which these influence the
value of the beds may be partly understood by reference to the an-
nexed diagram (fig. 219), where a bed of coal is represented as having
been frequently removed in position, in consequence of which it can
be worked at moderate depth over a distance of country which would
otherwise have carried the deposit far below the surface at the rate
of inclination observed.
Fig. 219.
Faults in coal-measures.
894. The coal-measures occupy definite and limited areas of some-
what considerable extent in various countries of Europe, Asia, and
North America, and in many of the islands adjacent. True coal has
not yet been met with in Africa or South America. We may regard
the following as a rough approximation of the coal areas in the chief
countries mentioned ; only those being referred to which are of the
BRITISH COAL-FIELDS.
409
date of the coal deposits of the British Islands, or at least belonging
to the Palaeozoic period. To this is added a statement of the estimated
annual production.
Countries.
British Islands
Coal-area in
square miles.
12 000
Propn. to 1
whole area.
1 10
Lnnual production
in tons.
30 000 000
.... 2 000
1 100
4 150 000
Belgium
. . 520
1 22
5 000 000
Spain
4 000
1 52
550 000
Prussia .
1 200
1 90
3 500 000
Bohemia
.... 1 000
] 20
United States of America
113000
1 20
4 000 000
British North America
18.000
29
Table of the principal Coal-fields of the British Islands.
Estimated
workable area
in acres.
Number of
workable seams.
Estimated total
thickness of
workable coal in
feet.
Thickest bed
in feet.
Thickness of
coal-bearing
measures in
feet.
1. Northumberland & Dur-
ham District.
^f 6\VCclStlc COfll-ficld
500,000
18
80
7
2. Cumberland and West-
moreland, and West Ri-
ding of Yorkshire.
Whitehaven and Akerton ....
80,000
7
8
2,000
Appleby (3 basins)
17,000
Sebergham (Cumberland) ....
p
1
3
3
Kirkby Lonsdale . . .
2,500
4
17
9
3. Lancashire, Flintshire, &
North Staffordshire.
Lancashire coal-field
380,000
75
150
10
6,000
120,000
5
39
9
200
Pottery, North Staffordshire . .
40^000
24
38
10
Cheadle, ditto
10,000
4. Yorkshire, Nottingham-
shire, Derbyshire.
Great Yorkshire coal-field. . . .
650,000
12
32
10
Darley Moor, Derbyshire . . .
Shirley Moor, ditto . . . . }
1,500
5. Shropshire and Worces-
tershire.
Colebrook Dale, Shropshire . .
21,000
17
40
Shrewsbury, ditto
16,000
3
Brown Clee-hill, ditto . .
1,300
3
Titterstone Clee-hill, ditto . .
5,000
Lickey-hill, Worcestershire
650
?
p
9
Bewdlev ditto . .
45.000
?
410
DESCRIPTIVE GEOLOGY.
Estimated
workable area
in acres.
Number of
workable seams.
Estimated total
thickness of
workable coal in
feet.
c
jl
f
F
Thickness of
coal-bearing
measures in feet
6. South Staffordshire.
Dudley and Wolverhampton . .
7. Warwickshire and Leices-
65,000
11
67
40
1,000
tershire.
40,000
9
30
15
40,000
5
33
21
8. Somersetshire and Glou-
cestershire.
Bristol
130 000
50
90
Forest of Dean
36 000
17
37
Newent (Gloucestershire) ....
1,500
4
15
7
9. South- Welch coal-field.
600,000
30
100
9
12,000
10. Scottish coal-fields.
1,000,000
84
200?
13
6,000
South of Scotland, several (
p
24
94
4 400
P
60
180
13
6 000
?
3
40
30
p
P
?
21
45 000
10
55
Q
11. Irish coal-fields.
Ulster
500 000
9
40 5
Q
200 000
150 000
8
23
Munster (several)
1,000,000
895. It is necessary to remark that the total number of workable seams in each
district is by no means clearly determined in all cases, and that many more local
names of seams are frequently given than there are distinct beds. The appearance of
the same seam in the same district varies often very greatly, and the "thickness of
strata between known beds is sometimes very different within a short distance. The
total number also of workable beds in a district is very rarely obtained in the same
colliery; and thus the object in the above table, which has been rather to give a
good general idea than a perfectly accurate account of particular cases, must be kept
in view by the reader in making any practical use of the information afforded. We
have not space to allude to more than a few of the chief of these areas, and the
peculiar points of geological interest in them to which attention is especially required
are not very numerous.
896. The Newcastle coal-field is almost without ironstone, and in
it the coal-measures repose on millstone grit and are covered up by
magnesian limestone. They consist chiefly of sands, called post, often
of very great thickness and far exceeding in magnitude and extent
BRITISH COAL-FIELDS."
411
the various beds of shale. The sandstone is especially abundant near
the upper part of the series. Cannel-coal is found in the district to
some extent. It contains very little bitumen. The quality of the
coal-seams varies considerably, but the following account of three
principal varieties may be useful.
Analyses of different kinds of Newcastle coal.
Splint- coal.
Caking-coal,
No. 1.
Caking-coal,
No. 2.
Cherry-coal.
1-302
1-274
1-280
1-266
74-961
83'588
87-809
84-694
6.254
5-150
5-159
5-054
4-873
8*743
5-139
8-476
Ash
13-912
2-591
1-393
1-576
Relative heat by the samej
110-34
114-98
122-56
116-63
Relative heat by same volume >
of coal *
108-99
111-31
119-03
112-07
In the above table, the Splint-coal is a coarse variety from a small bed of black
colour and considerable hardness, at the bottom of the series. The Caking-coal, No.
1 , is one of the best coals raised, and is from South Hetton. It is resinous, tender,
and brilliant. The Caking-coal, No. 2, is a lower seam from Garesfield, of brilliant
lustre, highly bituminous, soft, and friable. The Cherry-coal is a thin, soft, friable
bed, sunk through in the Jarrow Colliery. The analyses are by Mr. Richardson,
and are taken from M. Piot's " Memoire sur PExploitation des Mines de Houille
aux environs de Newcastle-sur-Tyne," p. 13. *
897. It is estimated that the mean thickness of the workable coal
over the whole area of the Newcastle coal-field is about twelve feet,
or four yards, and as the weight of a cubic yard of coal may be esti-
mated at above one ton, it thus appears that there have been not
less than about 10,000,000,000 tons of mineral fuel present in the
whole field. It may be considered that about 5,000,000 of tons
are at present removed or wasted annually, which would give a pro-
bable total duration of about 2,000 years from the commencement of
the workings. It is proper, however, to deduct one eighth part as
equivalent to the consumption up to the present time, and thus there
would appear to remain a quantity which would admit of the pre-
sent supply being obtained for 1750 years, or thereabouts. The
works in the Newcastle coal-field, are carried on to a very great
depth, one mine being sunk to 1,488 feet from the surface, and
another at Monkwearmouth to 1,794 feet. A vast quantity of water
often issues from the sinkings.
In estimating the quantity of coal in a given district it is usual and right to make
a large deduction from the apparent surface area to allow for accidents of denudation,
injury from faults, and also for that part of the coal thrown out of workable
depth. After this is done, and the average acreage of coal obtained, we must still
deduct nearly 50 per cent, for what is left underground in pillars and small coal, and
the quantity required for colliery consumption or wasted. When this is done, the
412 DESCRIPTIVE GEOLOGY.
quantity in tons of large saleable coal may be safely estimated as equal to the number
of cube yards. The average weight of good Wallsend coal is stated at 78-945 Ibs.
per cubic foot, the specific gravity being 1*263. This would give 21314 Ibs. the cube
yard.
898. The Whitehaven coal-field is separable into two divisions,
the upper part containing the more valuable seams. Some of the
seams are worked far under the sea ; and one extensive mine has
been destroyed by inundation. The coal is of good quality, burns
with a clear flame, and ultimately cakes. The number of seams is
considerable, but they are chiefly very thin.
899. The Lancashire coal-field presents a very extensive develop-
ment of the coal-measures, of which three divisions have been traced,
the middle containing the most valuable seams. It has been cal-
culated that the total quantity of coal in this field amounts to
8,500,000,000 tons, and the annual consumption is about 3,500,000.
Many of the seams are extremely thin ; but the quality is good. The
sinkings are moderately deep, and not greatly troubled with water.
The area of the Lancashire coal-field is very irregular in form,
measuring about 50 miles in length and 15 in extreme breadth,
reaching from Liverpool in a north-east direction to Yorkshire, and
thence due south, past Manchester and beyond Macclesfield. Besides
this area, which is occupied by true coal-measures, the lower beds of
millstone-grit yield coal to a considerable extent, so that the area
might in this way be extended to include 1000 square miles of coal-
bea'ring strata.
The sections of this region are unequal as regards the aggregate
of strata and of coal-seams. In one direction there are 75 beds of
coal, each more than one foot thick, in 2000 yards of strata, having an
aggregate of 150 feet of coal. Traversing another direction a second
section shows 26 seams of more than a foot, containing 93 feet of
coal. *
In the upper beds occurs a fresh-water limestone, worked at Ard-
wick, near Manchester, and containing many fossil remains. Not far
from this, in geological position, there have been found many trunks
of large trees standing upright on the coal-seams ; and the almost
invariable occurrence of stiff clay, forming a floor on which the coal
rests, has been supposed to prove that vegetable matter formerly grew
upon the spot where the coal is now found, although the great and
sudden alterations in the thickness of the seams show that the sur-
face was exposed to frequent changes of level. Some very considerable
faults are known in the coal-field, the principal one being so exten-
sive as to carry the coal 1000 yards below its former level.
900. The Yorkshire coal-field is remarkable for the great variety
of coals it presents some being very valuable, and some very poor.
* Taylor's " Statistics of Coal," p. 2Q4.
BRITISH COAL-FIELDS. 413
A large quantity is worked near Sheffield, Leeds, Bradford, and
Halifax, much of this being cannel-coal, admirably adapted for gas,
household purposes, &c., and some pieces hard enough to be worth
manufacturing into toys and ornaments. The three principal varieties
are the anthracitic, soft, and cannel coals; the latter being often iri-
descent. The depth to which the Yorkshire seams are at present
worked is not very considerable rarely, if ever, exceeding 1000 feet.
901. The Shropshire coal-fields. Of these the most interesting and
important is that of Colebrook Dale, which is not less remarkable for
its valuable mineral contents of coal and iron, than for the many and
complicated disturbances it has undergone, The coal is of fair
quality, rather heavy, and contains from 34 to 41 per cent, of vola-
tile substances. There are several seams of clay iron- ore, and the
iron made has sometimes been considered the best in England.
The following is stated as the average produce of the area :
Large coals 31,944 tons per acre.
Small coal or slack 7,986
Iron-stone 13,794
Average specific gravity of the coal 1'268
iron-ore .... 3-527
Thus the whole contents of the district may be stated approxi-
mately, as
800,000,000 tons of coal.
275,000,000 iron-stone
902. The South Staffordshire coal-field and the neighbouring dis-
trict are remarkable as yielding apparently a very thick seam of
coal varying from 20 to 40 feet, and locally called " the ten yard
seam." This is, however, in fact composed of a number of seams
(about 13) with very narrow partings, worked together, and there-
fore regarded as one bed. Besides the thick coal there are as many
as 10 other seams known in the district. The workings are not very
deep, the deepest rarely amounting to 800 feet. The quality of the
coal varies, part of it being of the kind called " cannel," but the
greater portion burning to a white ash. A large quantity of iron-
stone is found in some parts of the district, the annual make of iron
being upwards of 500,000 tons. It is hardly possible to estimate
the quantity of gettable coal in the South Staffordshire coal-field.
903. The Ashby coal-field has been estimated to contain about
1,500,000,000 tons of coals. The workings are very deep, some
pits being sunk to 1200 feet. The coal-seams generally repose on
fire-clay, of which a large quantity is exported.
904. The Bristol coal-field is much obscured, and the beds broken,
so that the whole area has been described as including five chief dis-
tricts. The beds are very thin, but numerous. They are also deep,
so that the working is attended by great expense, most of the sink-
414 DESCRIPTIVE GEOLOGY.
ings passing through overlying beds of New red sandstone, Lias, and
even Oolite. A large proportion of the area is still untouched.
905. The South Welch coal-field is generally considered as di-
vided into two parts one being anthracitic and the other bitumin-
ous. The former is supposed by some writers to have been derived
from the latter by exposure to heat. Without discussing this ques-
tion we may state generally, that in this district the western ex-
tension of the basin is the most anthracitic, and that in addition
to the two principal varieties there is a third or intermediate con-
dition of coal now known as " steam-coal," and admirably adapted
for the use of the steam-navy. This kind is extremely compact,
burns without perceptible smoke, and contains so little bituminous
matter as not to be at all subject to spontaneous combustion. It is
found in abundance near the Port of Swansea, and is cheap. The
following account of the weight of water evaporated by one pound
of coal will give a practical idea of the relative value of this fuel.
Weight of Water evaporated by different kinds of Coal.
Ibs. ozs.
Common Scotch bituminous coal 5 14
Hastings Hartley main, Newcastle 6 14 ^
Can's West Hartley ditto 7 5
Middling Welch anthracite 7 1 5J
Merthyr bituminous coal (S. Wales) 8
Llangennech steam-coal ditto 8 14
Cameron's steam-coal ditto 9 7|
Pure Welch anthracite ditto 10 8|
The productive capacity of the South Welch coal-field is not easily
ascertained, as it has been hitherto too little explored to justify any
calculation as to the average thickness of workable coal. The different
estimates vary from 60,000,000,000 to about 100,000,000,000 tons.
906. Almost every one of the numerous seams of coal in this dis-
trict, however thin, is underlaid by a seam or bed of fire-clay con-
taining in abundance the roots of Stigmaria (fig. 217), and many of
the merely bituminous seams are characterised in the same way.
The thickest seam of coal rests on about three feet of underclay, but
seams not an inch thick sometimes rest upon as much as five feet of
this substance, and there are also bands of it without coal. Argil-
laceous shale, sandy shales, and sand-rock form the associated beds,
and there seems no very apparent order of succession. With these
are a number of seams of iron-stone of great value producing an
enormous quantity of iron ; the seams are, however, generally thio,
their total thickness not generally exceeding seven feet in a single
shaft sinking.
907. The coal-fields of Scotland are estimated to equal in area
those of the whole of France, and they amount to one 1-18 part of
COAL-FIELDS OF IRELAND. 415
the total area of the country and its islands. The number of de-
tached areas is very large, and the quantity of coal worked con-
siderable. The quality of the coal is generally dry and free-burning,
not caking like the best coals from Newcastle, and inferior to the
latter in the quantity of heat obtained from combustion. Most Scotch
coals also yield a good deal of white ash, and they are apt to contain
pyrites. Some of the richest and most valuable bands of iron-stone
are obtained from the coal-measures of Scotland, chiefly from the
Basin of the Clyde, and from these a vast manufacture of iron is
carried on, the amount of pig-iron made last year (1849), being
nearly 700,000 tons, an increase of nearly 300,000 tons on the make
of 1844. The associated beds in Scotland include a very large pro-
portion of sandstone, and a peculiar limestone bed worked at Burdie
House near Edinburgh, besides a bed called the encrinite limestone.
The former is a dull, earthy rock about 27 feet thick, of bluish
or blackish grey colour, and often slaty texture. It contains very
numerous remains of fishes, one of which (the Megalichthys) has
been already described ( 891 fig. 218), and some fossil plants, besides
numerous microscopic crustaceans. The encrinite limestone worked
at Gilmerton and Crichton Dean contains similar fossils with the
addition of numerous encrinital fragments.
908. In Ireland there are 7 coal-districts, 1 in Leinster, 2 in
Munster, 3 in Ulster, and 1 in Connaught, those north of Dublin
yielding bituminous, and those south only anthracitic coal. The
Leinster deposit contains 8 workable beds, and it is calculated that
120,000 tons per annum are extracted from it. The Tipperary coal-
field extends about 20 miles in length by 6 in its widest part, and
forms a range of hills of from 300 to 600 feet in height, the coal
lying in deep troughs. The Munster field is the most extensively
developed of all the Irish coal-districts, and occupies considerable
portions of the counties of Clare, Limerick, Cork, and Kerry, but the
coal lies in troughs as in the Tipperary district. These are all
anthracitic.
909. Of the bituminous coal that of Tyrone is a small but inte-
resting field, chiefly remarkable for the variety of rocks found in the
neighbourhood. The coal-strata rest on the Dungannon limestone,
and consist of the usual sandstones and shales, associated with lime-
stone, ironstone, and fire-clay. The coal is abundant and easily ob-
tained, 22 to 32 feet of workable coal being found within a depth 01
120 fathoms.
At the northern extremity of Antrim is a small coal-field remark-
able for its association with the great basaltic mass of that district,
and resting immediately on mica-slate without intervening beds
either of limestone or Middle or Older palaeozoic rocks. At Mulvagh
Bay there are 6 beds of coal, 4 bituminous and 2 anthracitic. The
416
DESCRIPTIVE GEOLOGr.
latter of these beds are fine, one immediately above and the other
below a range of columnar basalt 70 feet thick which lies amongst
the coal-measures.
The coal-district of Connaught is interesting as having been worked
for iron-stone. Its greatest length is about 1 6 miles and its extreme
breadth nearly as great : it occupies hills having flat summits co-
vered with bog, presenting a straight ridge of from 1000 to 1200
feet high. The iron-stone bands are found associated with thick beds
of clay-slate (shale) from 300 to 600 feet thick, and are remarkably
rich. There are 3 beds of coal, the first from 1 to 3 feet thick, the
second from 3 to 3J, and the last 9 inches.*
910. From the coal-measures of the British Islands we pass on
now to consider the coal countries of the continent of Europe. Of
these Belgium is the most important, and as the great Belgian coal-
field extends also into France, we may consider these two at the same
time.
There are two principal divisions of the Belgian coal-area, the one
extending to the east, and known as the Liege coal-field, and the
other to the west forming the Hainault division, and reaching into
France at Douay. The former contains about 100,000 English acres,
and the latter upwards of 220,000 acres, and in both the number of
the coal-seams is exceedingly great, although many of the beds are
very thin and much more disturbed and displaced than is the case
with the contemporaneous English deposits. The annexed diagram
(fig. 220) will give some notion both of the way in which the coal-
Fig. 220.
Section across a Belgian coal-field.
seams are there presented, and the apparent multiplication of them
by very sharp and distinct doublings of the strata. There are said
to be no less than 150 coal seams in the western division of the dis-
trict. The thickness is not often great, and the position renders it
necessary to adapt the methods of mining with especial reference to
this. The quality of the coal is very various, including one peculiar
kind, the Flenu coal, unlike any found in Great Britain except at
Swansea. It burns rapidly with much flame and smoke, not giving
out an intense heat, and having a somewhat disagreeable smell.
There are nearly 50 seams of this coal in the Mons district. No
iron has been found with the coal of Belgium.
* Kane on " The Industrial Resources of Ireland."
BELGIAN AND FRENCH COAL-FIELDS.
417
Fig. 221
911. The most important coal-fields of France are those of the
Basin of the Loire ; and of these St. Etienne is the best known and
largest, comprising about 50,000 acres. In this basin are eighteen
beds of bituminous coal, and in the immediate neighbourhood several
smaller basins containing anthracite. Other valuable localities are
on the Moselle, near Saarebriick ; in Alsace ; several in Burgundy,
much worked by very deep pits, and of considerable extent ; some
in Auvergne, with coal of various qualities ; some in Languedoc and
Provence, with good coal ; others at Arveyron ; others at Limosin ;
and some in Normandy. Besides these are many others of smaller
dimensions and less extent, whose resources have not yet been deve-
loped. The total area of coal in France has not been ascertained,
but is, probably, not less than 2000 square miles. The annual pro-
duction is now not less than 4,000,000 tons. Most of the coal-
measures of France are of the same age as the English deposits, but
repose on granite or other crystalline or metamorphic rocks. The
associated rocks are generally sand and shales. The coal-seams are
almost all comparatively thin, and often irregular ; but several ten
foot seams of fair quality are found. Some remarkable cases are
known in France of the enclosure
of carboniferous rocks in clefts and
hollows in older and crystalline
rocks; but, perhaps, one of the
most remarkable is that repre-
sented in the annexed diagram
(fig. 221), of a coal-bed and asso-
ciated sands and shales enclosed
in porphyritic granite, at La Pleau
(Correze), in the province of Li-
mosin : the coal is ten feet thick,
of bituminous quality, and mea-
sures about 100 acres in extent;
it is worked from a shaft.
912. There are four coal-districts in Central Germany, of the
Carboniferous period, besides several districts where more modern
lignites occur. The principal localities for true coal are near the
banks of the Rhine, in Westphalia ; on the Saare, a tributary of the
Moselle ; in Bohemia ; and in Silesia. The total annual production
exceeds 2,750,000 tons. A considerable quantity of coal is also worked
in Saxony. Of these various localities Silesia contains very valuable
and extensive deposits of coal, which are as yet but little worked.
The quality is chiefly bituminous, the beds few in number, but very
thick, amounting in some cases to twenty feet. Some anthracite is
found. Bohemia is even more richly provided than Silesia, the coal-
measures covering a considerable area and occupying several basins.
Coal-measures in crystalline rock.
418 DESCRIPTIVE GEOLOGY.
More than forty seams of coal are worked ; and several of these are
from four to six feet thick.
913. The basin of the Saare, a tributary of the Moselle, near the
frontier of France, affords a very important and extensive coal-field,
which has been a good deal worked, and is capable of great improve-
ment. No less than 103 beds are described, the thickness varying from
eighteen inches to fifteen feet. It is estimated that at the present
rate of extraction the basin contains a supply for 60,000 years. On
the banks of the Ruhr, a small tributary to the Rhine, entering
that river near Dusseldorf, there is another small coal-field estimated
to yield annually nearly 1,000,000 tons. The whole annual supply
from Prussia and the German states of the Zollverein, or Customs
union, is considered to exceed 2,750,000 tons.
914. Hungary and other countries in the east of Europe, are known
to contain true coal-measures of the Carboniferous period ; but the
resources of these districts are not at present developed. On the
banks of the Donetz, in Russia, coal is worked to some extent, and is
of excellent quality, but it belongs to the older part of the Carboni-
ferous period.
915. Spain contains a large quantity of coal, both bituminous and
anthracitic. The richest beds are in the Asturias, and the measures
are so much broken and altered in position, as to be worked by almost
vertical shafts through the beds themselves. In one spot upwards
of eleven distinct seams have been worked, the thickest of which is
nearly fourteen feet thick. The exact area is not known, but it has
been estimated by a French engineer that about 12,000,000 of tons
might be readily extracted from one property without touching the
portion existing at great depths. In several parts of the province
the coal is now worked, and the measures seem to resemble those of
the coal-districts generally. The whole coal-area is said to be the
largest inEurope, presenting upwards of 100 workable seams, varying
from three to twelve feet in thickness.
916. We pass on now to the consideration of the coal-measures of
the Carboniferous period, as developed in the American continents.
It is only within a few years that these have been in any way known ;
and we are even now in ignorance of many details with regard to the
greater number ; but enough is ascertained to convince any unpre-
judiced person that the supply of mineral fuel there obtainable is
amply sufficient for the requirements of the whole civilised world
for thousands of years, even should the demand increase rapidly,
and the consumption continue to bear reference to the multiplica-
tion of all kinds of industrial occupation. The principal source
of information on this subject, and indeed generally on all sub-
jects concerning the statistics of coal, is an admirable work, by
Mr. R. C. Taylor, recently published, which we have already had
AMERICAN COAL-FIELDS. 419
occasion to make use of in describing the principal coal-deposits of
Europe.
There are in North America four principal coal-areas, compared with
which the richest deposits of other countries are comparatively insig-
nificant. These are the great central coal-fields of the Alleghanies ;
the coal-field of Illinois and the basin of the Ohio ; that of the basin of
the Missouri ; and those of Nova Scotia, New Brunswick, and Cape
Breton. Besides these are many smaller coal- areas which, in other
countries, might well take rank as of vast national importance ; and
which, even in North America, will one day contribute greatly to the
riches of various States. We will endeavour to give a brief outline
of the main facts concerning the chief of these districts.
917. The Alleghany or Appalachian coal-field, measures 750
miles in length, with a mean breadth of eighty-five miles, and tra-
verses eight of the principal States in the American Union. Its
whole area is estimated at not less than 65,000 square miles, or up-
wards of 40,000,000 of acres. The area is thus distributed :
Name of State. Area in acres.
Alabama 2,250,000
Georgia 100,000
Tennessee 2,750,000
Kentucky 5,750,000
Virginia 13,500,000
Maryland 350,000
Ohio 7,500,000
Pennsylvania 9,500,000
41,700,000
918. Making a liberal deduction for unproductive portions, de-
nuded and eroded strata, and the parts of the seams out of reach, we
may still fairly calculate that there exists in this district an area
of 25,000,000 of acres of productive coal-measures. The working
has already commenced in most of the States above-mentioned,
Fig. 222.
Black Warrior River, Rooks Valley. Cahawba River.
Coal. Grit. Limestone. Grit. Coal.
Section across the Alabama coal-fields. (Length 50 miles.)
though not generally to any very considerable extent. Thus, in
Alabama, the beds alternate with the usual sandstone shales and
clays, and the coal-seams worked seem to be from four to ten feet
thick, and are quarried at the surface. They repose on grits, and
appear on the two sides of an anticlinal, as seen in the annexed
diagram (fig. 222). The coal is bituminous, and used for gas. In
420
DESCRIPTIVE GEOLOGY.
Kentucky, both bituminous and cannel-coal are worked in seams
about three or four feet thick, the cannel being sometimes associ-
ated with the bituminous coal as a portion of the same seam ; and
there are, in addition, valuable bands of iron ore. In Western Vir-
ginia there are several coal-seams, of variable thickness, one nine
and a half feet, two others of five, and others three or four feet. On
the whole there seems to be at least forty feet of coal distributed in
thirteen seams. In the Ohio district, the whole coal-field affords on
an average at least six feet of coal. The Maryland district is less
extensive, but is remarkable as containing the best and most useful
coal, which is worked now to some extent at Frostburg. There ap-
pears to be about thirty feet of good coal in four seams, besides
many others of less importance. The quality is intermediate be-
tween bituminous and anthracitic, and it is considered well-adapted
to iron making. Lastly, in Pennsylvania, there are generally from
two to five workable beds, yielding, on an average, about ten feet of
workable coal, and amongst them is one bed traceable for no less
than 450 miles, consisting of bituminous coal, its thickness being
from twelve to fourteen feet on the south-eastern border, but gra-
dually diminishing to five or six feet. Besides the bituminous coal
there are, in Pennsylvania, the largest anthracitic deposits in the
States, occupying as much as 250,000 acres, and divided into three
principal districts. A section of one of these the Schuylkill is
Locust Mountain.
Fig. 223.
Sharp Mountain.
Transverse section of the Schuylkill coal-basin.
represented in the annexed diagram (fig. 223), and occupies upwards
of 100,000 acres. It consists of not less than sixteen workable
seams of three feet and upwards the thickest being nearly thirty
feet. These beds are repeated by numerous flexures, and in the dia-
gram (fig. 223) are twice represented by a disturbed synclinal axis.
919. The Illinois coal-field in the plain of the Mississippi is only
second in importance to the vast area already described. There are
four principal divisions traceable, of which the first or Indiana dis-
trict contains several seams of bituminous coal, distributed over an
area of nearly 8,000 square miles. It is of excellent quality for
many purposes ; one kind burning with much light and very freely,
approaching cannel-coal in some of its properties j other kinds con-
sist of caking or splint coal. In addition to the Indiana coal-field,
there appears to be as much as 48,000 square miles of coal-area in
BRITISH AMERICAN COAL-FIELDS. 42 1
the other divisions of the Illinois district, although these are less
known and not at present much worked. 30,000 square miles are
in the State of Illinois, which supplies coal of excellent quality and
with great facility. The coal is generally bituminous.
920. The third great coal-area of the United States is that of the
Missouri, which is little known at present although certainly of great
importance. From the account given of these localities, the reader
will be able to appreciate in some measure the mineral resources of
the United States, and may perceive also the importance of geological
knowledge in recognising the laws of position of material so valuable.
921. British America contains very large supplies of coal in the
provinces of New Brunswick and Nova Scotia. The former presents
three coal-fields, occupying in all no less than 5,000 square miles,
but the latter is far larger and exhibits several very distinct locali-
ties where coal abounds. The New Brunswick coal-measures include
not only shales and sandstones, as is usual with such deposits, but
bands of lignite impregnated with vitreous copper ore and coated by
green carbonate of copper. The coal is generally in thin seams lying
horizontally. It is chiefly or entirely bituminous.
922. In Nova Scotia there are three coal-regions, of which the
Northern presents a total thickness of no less than 14,570 feet of
measures, having 76 seams whose aggregate magnitude is only 44
feet, the thickest beds being less than 4 feet. The Pictou or central
district has a thickness of 7590 feet of strata, but the coal is far
more abundant, one seam measuring nearly 30 feet, and part of the
coal being of excellent quality and adapted for steam purposes. The
southern area is of less importance. Besides the Nova Scotia coal-
fields, there are three others at Cape Breton, of which one the
Sydney coal is admirably adapted for domestic purposes. There
are here 14 seams above 3 feet thick, one being 11 and one 9 feet.
923. The coal-measures of Australia and those of New Zealand are
of doubtful age. Some parts of the chain of islands between the
Malayan peninsula and Australia are known to contain mineral fuel,
but the exact position in the geological series has not yet been made
out. The same may be said of the Island of Borneo.
China appears to contain large supplies of mineral fuel, which were
worked so long ago as the thirteenth century. Mr. Williams, one of
the latest authorities concerning the statistics of this country, states
that " several kinds, both anthracitic and bituminous, are seen in the
coal-marts of the north. That which is brought to Canton is hard
and leaves a large proportion of ashes after combustion. During
ignition it throws off a suffocating sulphurous smoke. It is employed
in the manufacture of copperas."
Much better qualities are obtained at Nankin and further north-
wards.
422
DESCRIPTIVE GEOLOGY.
924. The following table, the analyses of English specimens chiefly
selected from those by Mr. Mushet, will give an idea of the relative
value of different coals :
ANALYSES OF VARIOUS KINDS OF COAL.
Analyses.
Locality.
Description of
Coal.
Specific
Gravity.
Carbon.
Bitumen, :
Volatile
matter,
Water.
Ash.
1. Newcastle- on-Tyne ..
Bituminous
Ditto
1-257
1-260
57-00
54*90
37-60
40-48
5-40
4-62
3 Ditto
56"40
41-00
2'60
4 North Wales
62*72
36*00
1-28
5. Staffordshire Potteries .
g Yorkshire
Ditto
Ditto
....
62-40
67-14
34*10
30'73
3-50
2-13
Ditto
58-38
39-51
2-00
Ditto
1-235
52-46
45-50
2-04
9 Ditto . ....
Cannel
1-278
48'36
47-00
4-64
10 Ditto ....
Cherry
57-00
40'00
3-00
11. Shropshire
12. South Staffordshire
13 Ditto
Bituminous
Ditto
Ditto
64-10
54-05
54-17
34-77
42-70
43-33
1-13
3"25
2-50
1 4 Dean Forest
Ditto
63-72
32-03
4-25
15 South Wales
Ditto
60"25
33-00
6-75
1 6 Ditto
Ditto
66-02
29*15
2-83
Ditto
70-68
25-82
3-50
18 Ditto . .
91-89
5-61
1-50
19 Ditto
79-50
17-50
3-00
20 Ditto
Steam coal
85-00
11-87
3-30
21 Clyde Valley ....
51-20
45-50
3-13
39-43
56-57
4-00
23. Scotch coal (mean) ....
24. Ireland, Leinster ....
25 Ditto ditto
Dry
Dry anthracitic
1-602
48-81
92-88
79-60
41-85
4-25
12-00
9-34
2-87
8-40
79-15
7-37
13-25
27. Ditto, St. Etienne . .
28. Spain (mean)
Bituminous
Ditto
....
65-68
53-00
27-83
40-00
6-49
7-00
29. Belgian, Hainault ....
30 Ditto Lie^e
Ditto
Ditto
1-276
84-67
76'00
13-23
19-60
2-10
4-40
31. Ditto, ditto
Dry
1-365
81'90
9-00
9-10
32 Silesia
Glance
58-17
37-89
8-93
33. Bengal
Slaty
1-447
41-00
36-00
23-00
34. American Ohio
Bituminous
55-55
41-85
2-60
35. Ditto Alleghany . .
36. Ditto Nova-Scotia
37. Pennsylvania Ditto
Dry
Bituminous
Anthracite
1-321
78-85
58-80
92'60
9-47
28.20
2-25
11-73
12-95
2-25
No. 1, is by W. R. Johnson, mean of several. Some further details are given in
896. No. 2, ditto, Liverpool coal. No. 3, Dunn. No. 4, Mushet, from Dee Bank,
five-yard seam, compact, used for iron. No. 5, Dufrenoy and Berthier, from Apdale,
nearly corresponds with Littlemiiie coal of Lane-end. No. 6, Mushet. Parkgate
main coal, used for blast-furnace. No. 7, ditto. Worsboro' furnace-coal, mean of
two. No. 8, ditto, Alfreton furnace-coal. No. 9, ditto, from Alfreton also. No. 10,
MILLSTONE GRIT. 423
Berthier, from Butterly. No. 11, Mushet, top-coal ; No. 12, ditto, ten -yard coal,
Bentley estate. No. 13, ditto, Corbyn's-hall, Heathen-coal. No. 14, ditto, Coleford
High-delf seam, top part. No. 15, ditto, household coal, Mynyddyslwyn. No. 16,
ditto, white-ash furnace-coal, twelve-feet seam, from Risca. No. 17, ditto, Bedws
ten-foot vein, south side of coal -basin. No. 18, ditto, Y stal-y-ferra works, Swansea,
a six-foot seam. No. 19, ditto, Dowlais works. No. 20, ditto, also from Dowlais,
a nine- ft seam. No. 21, ditto, a furnace-coal. No. 22, ditto. No. 23, W. R. John-
son. No. 24, ditto, a slightly bituminous variety from Kilkenny. No. 25, Dr. C.
T. Jackson. No. 26, by Berthier, mean of 12.. No. 27, M. Gruner. No. 28, ditto,
mean of five. No. 29, M. Cauchy,from near Mons. No. 30, C. Davreux. No. 31,
N. Delvaux, from Harion. No. 32, Richter, from Bielschowitz. No. 33, from
Cherra Ponjee. No. 34, Western Virginia, Valley of the Ohio. No. 35, ditto,
Percy, mean of two, from Frostburgh. No. 36, Johnson, mean of two from Pictou.
No. 37, Percy, mean of 2, Mauch Chunk.
The student must not mistake the nature and use of this table. In almost every
coal- district, a great difference exists in the coal taken from different seams, or differ-
ent parts of the same seam. All that can be attempted by analyses of single specimens,
is to give some notion of the prevailing character. Thus, the proportions of ash in
various coals would be generally those quoted in the table if the ordinary condition of
the coal was taken, but numerous specimens of Newcastle coal would yield much less
than five per cent, of ash, and much Lancashire coal a great deal more. The per-
centage of volatile matter must be taken in the same way, and includes of course
much carbon combined with hydrogen. Other analyses of coal will be found as fol-
lows : 354, 869, 885; these are generally in greater detail.
925. The Millstone grit is a more or less compact gritstone Or con-
glomerate often used in England for millstones and underlying the
true coal-measures, though not unfrequently containing thin seams
of mineral fuel. Thus, in Northumberland there is an area of nearly
350,000 acres of this kind, and in the West-riding of Yorkshire
and Lancashire another district of 650,000 acres with thin seams,
some few of which are workable, but the deposit generally contains
no carbonaceous matter, except a little disseminated through the
mass. Out of England the millstone grit is not generally present,
and indeed the coal-measures frequently offer the only evidence of
deposits of the Carboniferous period.
926. The Carboniferous or Mountain Limestone forms in England
the true base of the upper part of the Palaeozoic series, but it is by
no means always present. It may be regarded as a coral reef occa-
sionally containing bands of shelly, encrinital or other remains, and
numerous fragments of fishes. Sometimes, also, bands of impure coal
occur, which in other countries are of greater value and extent than
with us. In the South-western extremity of England, imperfect coal-
measures, called culm, replace the carboniferous limestone, and this
is the case also in Russia and perhaps elsewhere. In Ireland a pecu-
liar sandy deposit terminates the series. Some of the common fossils
of this period have been already figured (see figs. 143, 156), and
others are represented in the annexed diagrams (figs. 224, 225, 226).
Besides these, however, there are many others found, some of which
are regarded as characteristic.
424
DESCRIPTIVE GEOLOGY.
927. The following is the arrangement of the Carboniferous fauna in England-
Almost all the species belong to the lower part of the series :
Amorphozoa 1
Zoophytes 73
Encrinites 73
Annelids 13
Insects 2
Crustaceans 52
Brachiopoda 184
Conchifera dimyaria 164
monomyaria 1 38
Gasteropoda 162
Pteropoda
Heteropoda 23
Cephalopoda 1 34
Fishes 130
Total species 1,150
Fig. 224. Fig. 225. Fig. 226.
Group of Carboniferous fossils.
Fig. 224. Cyathocrinitesplanus.
225. Euomphalus pentangulatus.
226. Orthoceras lateralis.
928. The culmiferous series of Devonshire occupies a great trough,
the axis of which ranges east and west and extends for about fifty
miles, with a breadth of between thirty and forty miles. Crossing
the edge of this trough, we find a black limestone, overlaid by sili-
ceous flagstones ; and these are followed by sandstones and carbona-
ceous and calcareous shales, which gradually become harder, and pass
into siliceous bands of a dark colour, with earthy carbonaceous part-
ings, surmounted by a regular thick-bedded sandstone, resembling
the gritstones of the coal-measures.
929. The beds, the order of whose superposition has been just
mentioned, form, with a black carbonaceous shale and a black lime-
stone, the lower subdivision of the whole Carboniferous system, as
developed in the south-west of England. The order is somewat dif-
ferent, however, towards Dartmoor, for there an irruption of granite
CARBONIFEROUS SYSTEM OF DEVONSHIRE. 425
has taken place since the deposition of the strata, and the vicinity
of the crystalline rock has produced confusion and violent distortion.
Notwithstanding this, and the frequent repetition of these beds by
faults and disturbances, they are satisfactorily proved to be of great
thickness ; but they contain few fossils, and differ in lithological
character from the rocks, probably of the same age, in the middle
and north of England.
930. The upper culm-measures of Devonshire are the newest beds
of the district, and occupy nine-tenths of the whole surface of the
carboniferous deposit. This group is composed of sandstones and
indurated shales (the latter containing the culm), and is of great, but
unascertained thickness, being perpetually interrupted, coiled upon
itself, and repeated over again, forming an incredible number of
anticlinal and synclinal lines, all of them ranging east and west,
parallel to the strike of the beds.
There is, however, no difficulty with regard to the general order
of superposition, or the extent and real thickness of this part of the
deposit, for both on the northern and southern outskirts of the form-
ation a great ascending series is seen, throughout the whole of which
the dip is tolerably regular.
931. The sandstones of this group are generally close grained, and
of a grey or greenish grey colour, passing occasionally into flagstone
and laminated arenaceous shale, with fine ripple marks at the part-
ings. The shales vary in appearance from sandy beds to soft slaty
clays, not to be distinguished from the common coal shales ; and
amongst these latter are occasionally found dark carbonaceous bands,
containing obscure vegetable markings, discoloured by pyrites.
932. Such are the prevailing characters of the beds which form
the culmiferous series of Devonshire : these beds being the true
representatives of the Carboniferous system. Notwithstanding the
general paucity of fossils, one or two species of shells are not to be
distinguished from species well known in the mountain limestone ;
and the result of a comparison of the remains of plants from the-
culm, with those commonly met with in rocks of the Carboniferous
period, tends yet more strongly to establish the contemporaneity of
the two deposits. Considering the thickness of these culm-measures
in Devonshire, they might represent the whole mass of the mountain
limestone ; and the different mineral character of the rocks, depen-
dent on the circumstances under which they were respectively formed,
might account for considerable alterations in the fossils, and must
have had great influence in modifying the forms of animal life.
933. The Carboniferous system, as exhibited in Yorkshire and
Derbyshire, consists of a magnificent development of mountain lime-
stone, to whose presence the picturesque scenery of those counties is
due, the limestone being partly overlaid on the east, west, and north,
426 DESCRIPTIVE GEOLOGY.
by the millstone grit. The lower part of the millstone grit, however,
is sometimes represented by a series of laminated and often bitu-
minous shales, which rest immediately on the limestone and contain
some bands of iron-stone, and a few thin black limestones ; while the
upper part consists of several hundred feet of pebbly grits and other
sandstones alternating with thin bad coal.
934. Further north, and in the north-western part of Yorkshire,
the mountain limestone becomes a still more important and promi-
nent member of the Carboniferous series, and is capable of local
subdivisions. It is here subdivided into two groups, whose total
thickness is about 1800 feet. Of these two the lower, the Scar
limestone, forms bold bluff precipices, and is pierced in many places
by large natural caverns ; and both here and in the upper strata
(the Yoredale rocks), the limestone is remarkably different from the
contemporaneous beds in the south, containing thin seams of coal,
sometimes worked, and divided into several beds by partitions of
grit and shale. The Yoredale rocks thus contain at least five dis-
tinct beds of limestone, alternating with freestones, flagstones, &c.,
and attaining a thickness of as much as a thousand feet. In the
north-west of England, where the mountain limestone is developed in
the same manner, the upper beds of the series, the millstone grit,
and the true coal-measures, are scantily exhibited ; but in the north-
east, as in Northumberland, the Scar limestone is much broken by
the interposition of pebbly grits, shales, and coal-seams, which en-
tirely change the character of the formation.
935. In Ireland the mountain limestone occupies an important
place, and consists of two great bands of limestone, with a consider-
able thickness of shale and argillaceous limestone and sandstone
interposed, which are known by the name of calp or calp slate. It
is chiefly, however, in the northern and middle districts that the calp
is found, and it gradually thins out towards the south. Beneath
the lower limestone another series of schistose beds (the carbonifer-
ous slate) occurs, and this rests on sandstone beds, often alternating
with shale, and occasionally with limestone. The "carboniferous
slate " of the south of Ireland differs in lithological character from
that of the middle and northern regions, but, from the evidence of
fossils, the two must be looked on as contemporaneous.
936. On the continent the Carboniferous beds are similarly deve-
loped; the lower beds in Westphalia passing into calcareous shales,
containing fossil remains of the carboniferous type. These, there-
fore, are assumed as the base of the Carboniferous system. They are
immediately succeeded by a group of black imperfect limestones and
siliceous schists (Kiesel-schiefer of the Germans), considerably ex-
panded and traceable for some distance, and looked upon as the equi-
valents of the English mountain limestone, the under)ying beds
LOWER CARBONIFEROUS ROCKS OF RUSSIA. 427
representing the shales occasionally met with in England when the
sequence to the older rocks is complete.
937. The black limestone is extremely carbonaceous, argillaceous,
and fetid, and it corresponds so entirely in mineral character with
the culm limestone of Devonshire, that the description of the one
rock might almost serve for the other, not merely as regards its
general appearance and lithological character, but also because the
organic remains, the Goniatites and Posidonise, with which the
rocks in Devonshire are loaded, are in Westphalia also by far the
most abundant fossils of the deposit. On the continent, however,
the culm limestone passes upwards into another limestone of a lighter
colour, and this bed contains all the most characteristic fossils of the
true English mountain limestone.
938. Advancing still further eastwards we find in Russia that
the lower carboniferous beds consist of incoherent sandstone, alter-
nating with a bituminous shale, which sometimes contains thin
bands of impure coal and impressions of plants ; the whole being
surmounted by various beds of limestone, which form the central
group of the Carboniferous system. Of these beds, the lowest is
usually of a dark colour, as in other parts of Europe ; but the
middle, and most extensive, differs entirely from any contempora-
neous rock, being of a milk-white colour resembling chalk, and
loaded with flints. It is also of considerable thickness, and ex-
tremely fossiliferous, and alternates with beds of compact yellow
magnesian limestone, and bands of red or greenish shale or marl,
while associated with it there are splendid masses of white gypsum
and thin bands of limestone inters tratified. The third, or upper
division of the series, is scarcely less remarkable than the central,
being almost entirely made up of myriads of fossil bodies (called
Fusulina), resembling grains of wheat, and forming a limestone
which is of considerable thickness, and appears in the lofty cliffs
which occupy the banks of the Volga, and also in the coal region
between the rivers Dnieper and Don.
939. In Northern Russia, and in the upper beds of the Volga,
the central limestone of the Carboniferous system is totally devoid
of coal, which is found in shales and sandstones, interstratified with
thin courses of limestone in the lower part of the series, and in this
respect exhibits a resemblance to the lower beds of the mountain
limestone in Yorkshire. In the south of Russia, on the other hand,
the central beds of the Carboniferous system are occasionally pro-
ductive of good bituminous as well as anthracitic coal, offering, in
some points, very striking analogies in mineral condition to the great
South Welsh basin. The northern beds are nearly horizontal, but
the coal-field in the south appears to have been disturbed, and to
have been broken up by faults.
428 DESCRIPTIVE GEOLOGY.
940. North America presents some interesting points with respect
to the rocks now under consideration. The Carboniferous series of
Pennsylvania is based upon massive sandstones, conglomerates, and
shales, overlying a bed of fossiliferous limestone. Resting upon
this group, which is of great and uniform thickness, there is a depo-
sit of red shale, which varies in thickness from 3000 to less than
100 feet, and is supposed to thin out and disappear to the south-
west ; and this is partly overlaid and partly replaced by a hard
coarse conglomerate, very thin towards the north-west, but rapidly
swelling out, and becoming from 800 to 1200 feet thick towards the
south-east. None of these formations contain profitable coal, although
the remains of plants are found in them, and a few seams about a
foot thick occur in the red shales. The coal-measures themselves
form the uppermost part of the series, and consist of micaceous sand-
stones, arenaceous, argillaceous, and carbonaceous shales, and valuable
beds of limestone.
941. In other parts of the same wide area the Carboniferous series
manifests similar peculiarities of structure. Thus, in Nova Scotia,
and elsewhere in Canada, the lower beds consist of carboniferous
limestone ; but at Cape Breton the millstone grit appears to termi-
nate the sequence. Newfoundland, also, which presents not less than
5000 square miles of country, occupied by contemporaneous beds,
has hitherto afforded no coal.
942. The coal-fields near Calcutta, those of New South Wales, and
those of Van Piemen's Land, have been sometimes regarded as of
newer and sometimes of older date than the period we are now consi-
dering. Perhaps they may, with some probability, be referred to
the base of the true carboniferous rocks.
The two latter (Australian) districts present several seams of coal
in horizontal beds, alternating with slaty clay, sandstone, and shale,
together with a rock resembling millstone grit, and a hard cherty
rock. Seams of iron ore accompany the coal. The coal is of tolera-
ble quality, and is being worked. Near Lake Macquarie there are
five beds described, having a total thickness of nineteen feet in 204
feet of strata ; the two principal seams being five feet, and the others
three feet thick respectively. The one at present worked is not
more than twenty fathoms below the surface, and not more than
twenty yards from the water.
943. Near Burdwan about 130 miles north-west of Calcutta, a
small coal-area exists, and has been long worked for an indifferent
coal. The beds are eight in number, the largest being four feet and
the others much smaller, giving a total thickness of twenty-four feet
of coal. This coal burns with much flame, but does not cake, and is
accompanied by iron ore. There are many other coal-areas of the
PBODUCTION OF IRON.
429
same geological age in the vicinity, some of which have been partly
described. Amongst these is one to the North-east where the coal
is of superior quality ; but local circumstances have interfered with
the working. Several other small Palaeozoic coal-fields are described
in various parts of the East.
944. The Carboniferous series is not only remarkable for its coal,
it contains also large and very important supplies of metalliferous
ores, chiefly of iron, lead, and zinc. The latter are contained gene-
rally in dykes or veins, expanding against particular bands of car-
boniferous limestone, and often influenced by the presence of crys-
talline rocks. The lead mines of Derbyshire, Alstonmoor, and other
parts of Northumberland and Durham, exist under circumstances of
this kind, and are often found with veinstone of fluor spar, barytes
and calc spar.
945. The condition of the iron ore in the coal-measures of England,
Belgium, France, and America, is well-known to be that of carbonate
and oxide mixed with a large percentage of clayey impurities.
The-concretionary structure generally prevails, and the bands con-
sist of nodules, sometimes laminated, and sometimes concentric, but
usually of flattened spheroidal shape. They often enclose leaves
and other organic remains. The following accounts of the statistics
of the iron trade will afford the best information as to the extent to
which the iron-stone of the British islands is an important mineral.
The details of the iron mines of England will be found in the next
chapter.
Production of iron in 1845.*
Tons. Tons.
Brought up 3,850,000
Great Britain 2,200,000
United States 502,000
France 448,000
Russia 400,000
Zollverein '.. 300,000
3,850,000
Austria 190,000
Belgium 150,000
Sweden 145,000
Spain (1841) 26.000
Rest of Europe 50,000
4,411,000
Production of iron in Great Britain.-^
South Wales
1830.
.... 277 b'43
1840.
505 000
1843.
457 355
South Staffordshire
.... 212 604
407 150
300 250
.... 37500
24] 000
238 550
.... 73,418
82 750
76 200
... 28 926
56 000
49 000
.... 18,000
31,000
25,750
5 327
11 000
25 750
20 500
21,750
North Wales .
25 000
26 500
19 750
Forest of Dean
15,500
8,000
* Taylor's "Statistics of Coal," Introduction, p. xxix.
t Report of Brit. Assoc. for 1846, p. 118.
430
CHAPTER XVII.
ON THE ROCKS AND FOSSILS OF THE OLDER PART OF THE
PALEOZOIC EPOCH.
3. The Devonian, or Old red sandstone system.
946. The various rocks called by English geologists Devonian
or Old red sandstone, according to the different circumstances under
which they appear, are recognised under nearly the same name in
France and Germany, and include also many of the so-called grey-
wacke schists of the latter country.
The following are the principal subdivisions of the group.
OLD RED SANDSTONE SERIES.
HEREFORDSHIRE. SCOTLAND.
/ Quartzose yellow sandstone.
Old red conglomerate j Impure limestone.
* Gritty red sandstone. ^
Cornstone Grey fissile sandstone.
r Red and variegated sandstones.
Co ana mar, SgSSSJSL-i
Great conglomerate.
DEVONIAN SERIES.
DEVONSHIRE. BELGIUM.
Cakareous grits and impure lunestones . %*** I-"*
Red flagstones Lower limestone of Belgium.
Calcareous slates and Plymouth lime- Hard siliceous beds and conglo-
stones merates.
The fossils of this period include many species of corals, en-
crinites, and shells ; of the latter of which a few characteristic species
are figured in the annexed cut (figs. 227 230). Others are repre-
sented in figs. 138, 151, 160. There are also a number of remains
of fishes, some of very great interest from the remarkable peculiarities
of form and structure which they present. Many of these are small,
but others of gigantic proportions.
947. The Old red sandstone of England and Wales consists of
various strata of limestone, marl, and sandstone, alternating with
great thicknesses of conglomerate, which often pass upwards into
overlying sandstones, and the series is expanded over a considerable
portion of our island, rising into lofty mountains, occupying exten-
sive plains, and developed to an enormous thickness.
948. In North Wales, although the Old red sandstone retains its
general character, we find it inferior in thickness and importance
to its development in Herefordshire and South Wales. It again
OLD RED SANDSTONE.
431
increases, however, as we advance still further northwards into West-
moreland and Cumberland, where it appears as an irregular conglo-
merate. In this part of England its largest development is near the
foot of Ullswater, and it rises into a succession of round topped hills
several hundred feet high, the beds being of great thickness. No
true passage is there discernible into the overlying limestones.
Fig. 230. Fig. 227. Fig. 229.
Group of Devonian fossils.
g 228 } Terebratula porrecta.
229. Magalodon cucullatus.
230. Clymenialinearis.
949. The loftiest points occupied by this deposit are the Vans of
Caermarthen and Brecon, the former 2590, and the latter 2500 feet
above the level of the sea. These hills are made up of a conglo-
merate, composed of white quartz pebbles embedded in a red matrix ;
and it is this quartzose conglomerate which gives its name to the
uppermost group of the formation.
The highest beds of the series do not, however, always consist of
conglomerates, but are more frequently composed of beds of sand-
stone, hard and finely grained, and alternating with a few imper-
fectly exhibited mottled marls. The lower portion capping the
escarpment of the cornstone in Herefordshire, furnishes thick beds
of valuable building material, and is occasionally quarried for tiles.
The upper beds are, for the most part, less compact, and commencing
as a fine conglomerate they afterwards become coarser, and alternate
with bands of red and green argillaceous marl. Fine examples of
the conglomerate beds (attaining near Abergavenny a thickness of
200 feet) may be seen on the banks of the Wye, between Ross and
Monmouth, and again on the right bank of that beautiful river, to
the north of Tintern Abbey.
432 DESCRIPTIVE GEOLOGY.
950. The cornstone consists of a number of argillaceous marly
beds, sometimes alternating with sandstone and sometimes with im-
pure limestone, affording, by decomposition, the soil of the richest
tracts of Herefordshire and Monmouthshire. The lower part of this
rock very often contains flaggy beds, some of which are extensively
quarried near Downton Hall, the stone being of a greenish colour,
and highly micaceous, and usually more or less intermixed with
party-coloured marls, or soft argillaceous sandstones, not so compact
as the rock which encloses them. The surface of the sandstone is
frequently worn into irregular holes and patches.
951. But the subdivisions of the sandstones are too entirely local
to allow of any lithological character being given, which can apply
to more than a very limited district. Generally speaking, the im-
pure concretionary limestone, which is more especially denominated
cornstone, appears at intervals in irregular lenticular masses through-
out the district, contracting and expanding in the most capricious
manner ; sometimes replaced by finer and more crystalline limestone,
and sometimes alternating with hard flaggy sandstones. Nearly the
whole of the central and northern parts of Herefordshire, and the
contiguous parts of Shropshire and Worcestershire, are occupied by
this formation ; and its vast thickness is well displayed in the hills
crossed by the new road from Leominster to Hereford. In the
northern portion of the range, and near the mouth of the Towey,
in Caermarthenshire, the limestones are most fully developed, becom-
ing much thicker, and also more crystalline, than in other parts.
952. In Scotland the uppermost becls are highly arenaceous, and
often consist of sandstone conglomerates. The intermediate calca-
reous band is barren of fossils, and is of somewhat singular compo-
sition, yielding unequally to the weather, and exhibiting a brecciated
aspect. It contains masses of chert exceedingly hard, and these,
from the manner in which they are incorporated with the rock, ap-
pear to have been of contemporaneous origin. The bed is several
yards in thickness, and is very persistent, being found both in Moray
and in Fife, localities 120 miles apart.
953. The middle group of the Old red sandstone of Scotland,
corresponding to the cornstone of England, is developed in Forfar-
shire, in Morayshire, and in the grey sandstone of Balruddery, where
the lower beds are absent. It is represented as consisting, for the
most part, of rocks of a bluish grey colour, sometimes, as at Balrud-
dery, resembling the Silurian mudstones, at others forming a hard
fissile flagstone exported as a paving stone, and occasionally ap-
pearing in beds of friable stratified clay, easily washed away by the
sea. The colour, however, throughout is grey, and in this respect
differs essentially from the English contemporaneous beds, which
are chiefly red and green marls.
IRISH DEVONIAN BEDS. 433
954. The base of the whole system is represented by Mr. Miller
as consisting of an extensive and thick conglomerate rising into a
lofty mountain-chain in the county of Caithness, and attaining an
elevation of 3500 feet in the hill called Morrheim, but a great thick-
ness of arenaceous strata, containing conglomerates of various mag-
nitude, intervenes between these and the middle beds.
955. The Devonian beds present a series so distinct that no rela-
tions of mineral or mechanical condition can be traced between them
and the Old red sandstones. The upper beds on which the culms
of Devonshire repose consist of coarse red flags and slates, some-
times alternating with or overlaid by other slates and limestones,
while the lower beds are to be sought for among the calcareous slates
of Cornwall and South Devon. These calcareous slates are occa-
sionally fossiliferous. and are based upon an impure limestone. The
Plymouth limestone in the south, and a group of coarse arenace-
ous beds in the north of Devon, together with the general series
of Cornish rocks, are all included among these calcareous slates.
Throughout the whole series fossils occur, but they are very un-
equally distributed, being locally abundant, although, owing to the
metamorphic character of many of the beds they are sometimes
much altered, and frequently obliterated.
956. The development of the Old red sandstone and the contem-
poraneous beds in Ireland is peculiarly interesting, as completing
within the circuit of our own islands the whole of the chain of evi-
dence necessary to establish the true place of the Devonian grey-
wacke. In the south of Ireland, as in the south of Scotland, the
sequence is perfect from the upper beds of the Silurian system into
the lower beds of an extensive series of coarse conglomerates, which
there represent the Old red sandstone, and these pass upwards
through the numerous gradations of the same formation in Here-
fordshire, until they are at length replaced by roofing slates, re-
sembling those at the base of the culm-measures of Devonshire, and
are finally succeeded by similar strata, the coal-fields of the south
of Ireland assuming the exact character of the Devonian culm. It
is clear that the formations in Devonshire, containing fossils which
are intermediate in character between the Carboniferous and Silurian
systems, must themselves occupy an intermediate position, and must
therefore be on the parallel of some part of the Old red sandstone,
which is thus shown to fill up the whole intervening space.
957. In Belgium and Westphalia the beds of the middle part of
the Palseozoic period commence with a series of 1500 feet of strata,
chiefly composed of coarse, yellowish sandstone, sometimes changing
to grey micaceous flagstone, and alternating with shales and calca-
reous beds ; indicating clearly that this and the overlying deposit of
mountain limestone were absolutely continuous and linked together
F P
434 DESCRIPTIVE GEOLOGY.
by a gradual passage. Below this occurs a series of alternating beds
of an open-grained, yellowish sandstone (psammite) and of indurated
shale or earthy schist ; its total thickness is very great, and in both
the lower and upper parts there occur limestone-bands, and bands of
calcareous shale, extremely fossiliferous, and indicating an approach
to the Carboniferous system.
Without any break of continuity, or any appearance of inter-
rupted sequence, these beds pass into a mudstone, a rock whose
mineral characters resemble, in many respects, those which mark
some Silurian beds of England.
958. The lower limestone of Belgium, underlying this series, is
well defined and of great thickness. Both by the evidence of sec-
tions and by fossils, it has been ascertained to be contemporaneous
with the true Devonian limestone, and it appears identical with that
of South Devon, and with the corresponding beds in Westphalia.
The whole group is of great thickness and is fossiliferous ; but the
line of separation by means of fossils has not been clearly made out,
the upper part of the mass being unquestionably Devonian, while
the lower beds seem to pass into Silurian strata, and contain fossils
common to both formations.
Other beds of the same age have been found in various places in
Westphalia and on the banks of the Rhine ; and they are frequently
greatly disturbed and contorted, presenting numerous examples of
irruptions of melted rock of much newer date than that of the
deposits.
959. The Devonian, or Old red sandstone formations of Russia,
occupy a tract nearly as large as the whole of the British Islands,
and they rest conformably upon low plateaux of Silurian rocks, at-
taining heights of from 500 to 900 feet above the sea level.
In different parts of the large tract of land occupied by formations
of this geological period, there occur varieties of mineral composition
and lithological character quite as great as those already described
in speaking of the contemporaneous rocks in our own country and
Germany ; and the fossils consist of nearly all those which are most
characteristic of the different beds in each, together with a few spe-
cies not met with in Western Europe.
960. On the flanks of the Ural chain the Devonian rocks, over-
lying Pentamerus limestones, appear in the form of limestones and
schistose beds with grits, the limestones resembling, in their dark
colour and sub-crystalline aspect, those of South Devon, and the
whole group quite as dissimilar from that occurring in the flat
regions of Russia, as are the rocks of the same age in the south-west
of England from the conglomerates and tilestones of the Old red
sandstone.
961. In the heart of Russia, again, there exists a great dome-like
FOREIGN DEVONIAN ROCKS. 435
elevation, which rises to the height of about 800 feet above the level
of the sea, and is composed of strata loaded with fossils characteristic
of the Devonian system. But these strata are very unlike any other
known Devonian beds in their lithological character, being composed
of yellow and white marlstones and limestones, the latter often mag-
nesian, and so accurately resembling the Zechstein of Germany (quite
the top of the Palaeozoic system), that, were it not for the evidence
derived from fossils, they would inevitably be referred to the same
period as this latter bed.
962. It is interesting to find that the Devonian system, which
occupies so important a place in European Geology, is repeated on
the continent of America, with nearly the same lithological charac-
ters, and the same species of organic remains. In the Western
States of North America, towards the Alleghanies, a group of about
150 feet of strata has been described, strikingly resembling the lower
part of the Old red sandstone of Scotland, and containing similar
species of fossil fish. These rocks thicken out towards the east, pre-
serving their lithological peculiarities, and attaining a thickness of
1000 or 1500 feet in the neighbourhood of New York, where they
pass insensibly into the carboniferous strata. In other parts of
North America, as, for instance, in Canada, it seems almost certain
that contemporaneous beds exist.
Devonian beds occur also in South America, in the Bolivian Andes,
and in the Falkland Islands, while other portions have been detected
in Australia, and probably occupy a part of several of the islands of
the Southern hemisphere.
963. The slates and schists of the Devonian period in Devonshire
and Cornwall are not unfrequently traversed by systems of veins con-
taining metalliferous ores of various kinds. Dykes of crystalline
rock also are met with, proving that many important disturbances
connected with the protrusion of crystalline rock must be regarded
as more modern than the period of the accumulation of these strata.
The metals most abundant in Devonian rocks in the British Islands
are copper and tin in the east and west veins, and lead, zinc, and
silver in those transverse to this principal direction.
4. The Upper Silurian series.
964. The Upper Silurian rocks of England are chiefly developed
in the counties of Shropshire, Radnorshire, and Herefordshire, and
the whole group may be conveniently divided into three parts, ac-
cording to the following Table :
1. Tilestone.
( Upper Ludlow shale.
2. Ludlow Formation . . . . -j Aymestry limestone.
( Lower Ludlow shale.
436 DESCRIPTIVE GEOLOGY.
The Silurian rocks are so named from the districts in which their main divi-
sions and best developed series were first discovered and described. The district in
question a portion of South -Wales and the adjoining counties of England was
formerly inhabited by the Siluri, a tribe of ancient Britons, and was investigated
geologically by Sir Roderick Murchison, with a view to the determination of a well-
marked series of rocks more ancient than those of the Carboniferous system.
965. The Tilestone has usually been described as the lowest mem-
ber of the Old red sandstone series, but is now regarded as Silurian,
and possesses very marked characters both in structure and fossil con-
tents. It is clearly defined, occupying the loftiest parts of the escarp-
ments of a wild mountain range, attaining an elevation of 1500 to
1600 feet, and running from Llangadock, in Caermarthenshire, in a
north-easterly direction through Brecknockshire, to Builth on the
borders of Radnorshire.
Throughout this extensive range of highly inclined beds tile-
stones are extensively quarried, and consist of hard finely-laminated
micaceous and quartzose sandstones of a greenish colour, usually
associated with reddish-coloured shales, which decompose into a red
soil, therein generally distinguished from the Upper Silurian rocks,
which decompose into a grey soil. In this part of the system organic
remains are abundant in particular localities, and often indicate the
lines of deposit, when transverse cleavage and the faces of joints
would otherwise render the bedding difficult to be distinguished.
966. The upper beds of the Upper Ludlow rock those, there-
fore, which form the next in order of the beds of the Silurian system
consist chiefly of yellowish sandstones of very fine grain, and
slightly micaceous, which succeed the calcareous strata just de-
scribed, with the intervention of a greyish coloured stone. Near
Downton Castle there is a bed of greenish-grey argillaceous sand-
stone, resting on these sandy and flaggy beds, and almost made up of
the remains of fucoids and the columns of some soft zoophyte, which
is overlaid by another fossiliferous bed, seldom exceeding a few inches
in thickness, and occasionally dwindling to a quarter of an inch.
This singular stratum is a matted mass of the scales, defensive fins,
jaws, teeth, and coprolites of fishes, united together, with a few small
shells, by a cement in which variable proportions of carbonate of lime,
iron, phosphate of lime, and bitumen are disseminated. Above this,
again, a succession of micaceous sandstones passes insensibly into the
lower beds of the Old red sandstone.
967. The central mass of the Upper Ludlow formation is made up
of strata, containing more calcareous matter than the lower shales ;
and this imperfect limestone, being mixed with an argillaceous paste,
forms a tolerably durable building stone. The best stone quarried
for such purpose occurs in beds not exceeding eight inches in thick-
ness ; and its surface is frequently marked by undulating ridges and
furrows, supposed to be due to the rippling action of the waves, when
AYMESTRY LIMESTONE. 437
the bed formed the surface-bottom of the sea, and the sediment was
still soft. Markings, resembling those which would be made by the
passage of the smaller marine animals over sand and mud, are also
common on these furrowed surfaces.
968. The Aymestry or Ludlow limestone differs considerably from
the Wenlock limestone, both in its general appearance, and in its
having a less concretionary structure. It is sub-crystalline and
highly fossiliferous, and is fully developed near the village of Aymes-
try, in beds from one to five feet thick, which are of an indigo or
bluish-grey colour, mottled with white, and contain numerous layers
of shells and corals. Near the village of Downton-on-the-rock, this
limestone is well seen in a vertical cliff, the beds dipping at an
angle of about 25 N., and being not less than fifty feet in thickness.
This intermediate calcareous band is frequently absent in locali-
ties where the other portions of the Ludlow formation appear ; but,
when present, it may usually be identified as well by its lithological
peculiarities as by a remarkable fossil (Pentamerus Knightii), (fig.
231, 232), characteristic of it.
Fig. 231. Fig. 232.
Pentamerus Knightii.
The lower beds of the Upper Ludlow formation sometimes pass
by a series of gradual changes scarcely perceptible into the Ay-
mestry limestone, and may even be grouped with it when the former
happen to be concretionary and calcareous. These lower beds are,
however, much more frequently argillaceous, and well entitled to the
name of mudstone, which is often applied to them, as well as to the
Lower Ludlow shales. It is usually only the transition beds from
the underlying limestone, that are at all calcareous ; and these are
also remarkable for being absolutely loaded with the shells of a spe-
cies of Brachiopoda, (Terebratula navicula), which is exceedingly
common wherever this rock makes its appearance.
969. The next rock in order of date the Ludlow shale resem-
bles, in colour, appearance, and want of cohesion, the middle shales
of the Wenlock group, and occurs in valleys, between the Wenlock
and Aymestry limestone. The steep escarpments of several hills west
438 DESCRIPTIVE GEOLOGY.
of Ludlow expose the outcrop of the strata ; and their junction with
the underlying Wenlock limestone is marked by a series of friable
stone-bands, containing corals and spheroidal concretions of clayey
limestone, alternating with beds of clay. The concretionary charac-
ter of the lower part of the series is very remarkable ; and the con-
cretions are almost invariably formed upon some organic body as a
centre.
The main portion of the Lower Ludlow formation is composed
of dirty shales, locally called mudstones ; but these shales change
towards the upper part, and become slightly calcareous. They are
then succeeded by sandy flag-stones, also containing calcareous mat-
ter, and are separated by courses of soapy clay (sometimes used as
fuller's earth), from the overlying beds of limestone.
970. The Wenlock or Dudley limestone forms, in some tracts, the
most prominent feature in the geology of this lower division of the
Upper Silurian strata, and is admirably exhibited in the rock on
which Dudley Castle is so picturesquely placed, and also in the beau-
tiful escarpment of Wenlock edge. The remarkable physical features
of this bed of limestone, and the singular abundance of fossils, of
which the annexed diagram (figs. 233, 234) represents two common
forms, are well known and highly characteristic.
Fig. 233. Fig. 234.
Silurian fossils.
Fig. 233. Catenipora escharoides.
234. Asaphus caudatus.
The Wenlock limestone formation rests conformably on the Wen-
lock shale, and is made up chiefly of concretions of argillaceous lime-
stone, extremely fossiliferous, separated from one another by beds of
shale. The concretions are massive, and valuable for lime-burning,
the best of them being quarried to a considerable extent. They are
of irregular thickness and magnitude, and are surrounded and en-
closed by beds of impure clay and shale ; the clay entering into the
WENLOCK SHALE. 439
innumerable interstices and crevices of the limestone, and giving it
a singular mottled appearance.
971. Occasionally, however, beds of argillaceous limestone alter-
nate with shale ; and at Wenlock Edge, and elsewhere, the whole
series is both overlaid and underlaid by a number of small concre-
tionary nodules of grey limestone, running in layers, and held toge-
ther by shale, with which the nodules sometimes unite, and form
irregular and thin beds of lenticular limestone.
The nodules, so common in the Wenlock limestone, are found also
in other parts of the formation, and are usually crystalline, and full
of corals and encrinites ; the whole group of the Wenlock series,
indeed, may be said to consist of numerous concretionary masses,
separated from each other by a vast predominance of argillaceous
matter.
972. The Wenlock shale, sometimes called the Dudley shale,
consists of a great development of dirty-looking argillaceous beds,
rarely micaceous, and containing, here and there, a few lumps of
impure argillaceous limestone. The colour of these beds varies from a
pale grey to dark grey or black ; and, according to Sir R. Murchison,
the line of separation between the Upper and Lower Silurian beds is
best drawn where the hard sandy, and sometimes calcareous strata,
at the top of the Caradoc sandstone, are succeeded by these softer
shales. Calcareous concretions are met with occasionally, both in
the lower and upper portions, and the laminae of deposit are not
unfrequently indicated by large spheroidal lumps ; but the central
beds are soft, incoherent, and easily washed away, an instance of
which is seen along the escarpment of Wenlock Edge, where the
deep valleys, between that ridge and the Caradoc hills, indicate the
extent of denudation that has taken place in this part of the series.
973. In the north of England, the upper part of the Silurian
system is exhibited in a series of sandy flagstones, with imperfect
slaty bands, based on calcareous slates and the limestone of Coniston
Water-Head. The slaty bands are sometimes calcareous, but do not
contain limestone fit for use ; and the series terminates with red
fossiliferous strata, the fossils occurring in concretions of limestone,
and the whole being overlaid by the marls of the Old red sandstone.
The Silurian group, in this district, although repeated by several
undulations, is still of great thickness, and contains several fossils
peculiar to it but the greatest portion are of known Upper Silurian
types.
On the whole it appears, that certain common lithological cha-
racters pervade most of the strata of the Upper Silurian forma-
tions in England ; but that, while the subdivisions established by
Sir R. Murchison are persistent throughout a large tract of Shrop-
shire, Radnorshire, and Herefordshire, their lithological details as
440 DESCRIPTIVE GEOLOGY.
might indeed have been anticipated, do not apply to other and dis-
tant parts of the country. In the Silurian district the total thickness
of the two formations (the Wenlock and Ludlow) is very considerable,
and it is probably much greater in some parts of North Wales ; while
the beds throughout exhibit every appearance of slow deposition in
the finely laminated shales and micaceous fossiliferous sandstones
which abound in them.
974. The Silurian rocks, though very distinctly divided into an
upper and a lower series in the British Islands, or at least in some
parts of them, are by no means so completely distinguished in other
parts of the world. Still, the upper division has been well traced
in various parts of Scandinavia, Russia, and North America, having
closely allied species of fossils, both of shells and other bodies, and
there can be little doubt of real contemporaneity.
5. The Lower Silurian series.
975. Under this name we include all those fossiliferous beds
hitherto described which underlie the Wenlock shale. In the typi-
cal Silurian district these are the Caradoc sandstone and the Llan-
deilo flags of geologists, but in North Wales the Lower Cambrian,
and in Cumberland the Lower Cumbrian systems of Professor Sedg-
wick must be considered as representatives. The very great extent
and thickness of the beds of this earliest period, the metamorphism
of many of the rocks, and the wide range of a few similar or identical
fossils, all combine to give considerable interest to the group of
Lower Silurian rocks.
976. Caradoc sandstone is the name given to a range of fossiliferous
sandstones, with calcareous bands, whose mineral structure and litho-
logical character are variable, the uppermost beds being micaceous and
thinly laminated, containing bands of impure sandy limestone and
thin courses of sandstone, full of shells and fragments of shells.
Calcareous bands, exceedingly fossiliferous and sometimes burnt for
lime, succeed to these, and alternate with sandy and pebbly grit-
stones ; the upper grits being of a reddish brown or yellow colour,
and overlaid by thick-bedded, finely-grained, siliceous sandstones,
much quarried for flags and building stone. Irregular patches and
occasional courses of limestone are distributed through this rock, and
300 or 400 feet of flaggy beds succeed, composed of fine grained
sandstone of a green colour, and slightly micaceous. These latter
beds are fossiliferous and finely laminated ; but they are almost en-
tirely devoid of argillaceous matter. Where the sections are best
exhibited, there occurs in the lower part of the group a deep reddish
purple sandstone, mixed with clay, and marked with greenish streaks.
977. The base of the system, as recognised by Sir R. Murchison in
the Silurian region, consists of a series of hard, dark-coloured, sandy,
LOWER SILURIAN ROCKS. 441
or gritty beds, readily splitting into flagstones ; which are largely
developed near the town of Llandeilo in Caermarthenshire, and are
thence called Llandeilo flags. These beds are slightly micaceous,
and frequently so calcareous as to contain true limestones. The
Plynlimmon and Bala rocks of North Wales belong to this part of
the series.
978. The various beds of the Lower Silurian series are repeated by
a large number of folds throughout North Wales, presenting a num-
ber of remarkable structural peculiarities in that country, where
the extreme complexity of the phenomena long rendered it almost
impossible to arrive at any satisfactory conclusion. Now, however,
that the whole district has been carefully surveyed and mapped,
there seems little doubt of the real contemporaneity of a large num-
ber of beds apparently forming distinct series. Of these there are
well known examples of great interest not only in the Lake district
as already intimated, but also on the borders of Scotland, in Corn-
wall, in Ireland, and in the Isle of Man. In most of these cases the
deposits consist of slates and shales, more or less mingled with sand
passing into true greywacke or sandy schists and crystalline slates.
The limestones are generally impure, and in lenticular masses or
concretions, rarely fossiliferous, or if so, exhibiting only doubtful and
imperfect fragments of organic bodies.
979. Silurian rocks having very nearly the same mineral character
as those of England are found in various parts of the continent of
Europe, in Asia, Africa, America, and Australia. Of these a very
large portion of the Older division is found in Northern Europe,
where a succession of slates and accumulations of greywacke schist
frequently without fossils, or with very doubtful indications of or-
ganic existence underlie all the deposits hitherto described. Thus,
in Belgium the Ardennes slate is of this kind, and in Bohemia in
the east, and Brittany on the west, fossiliferous beds of the oldest
period have been distinctly traced.
980. The oldest sedimentary deposits of Russia (those on which
St. Petersburgh is situated) are described by Sir R. Murchison as
composed of clays, sandstones, limestone, and flagstone ; which rest
upon gneiss and altered rocks, and, from their position and organic
remains, are to be considered the equivalents of the Silurian system
of England.
In the blue clay which forms the lowest stratum in the Russian
Palaeozoic series, no organic remains have yet been found, and the
first fossiliferous bed is a sandstone, or grit, distinguished by a remark-
able fossil (the Ungulite) unknown in Western Europe ; but in the
overlying limestones, and the flagstones which rest upon them, other
organic remains abound, and the subdivisions agree tolerably well, in
their leading characters, with those established in our own country.
442 DESCRIPTIVE GEOLOGY.
981. With the exception of trifling dislocations, the Silurian rocks
of Russia are so uniformly horizontal that the dip in some places
amounts to only 2 or 3, and in a quarry visited by Sir R. Murchison,
its direction was observed by pouring water on the surface of the
rocks ; but, notwithstanding this nearly perfect horizontality, there
may clearly be traced in the Baltic provinces of Russia a passage
from the lowest beds in the north to the higher ones in the south,
where they are surmounted by others of still newer date.
The horizontal position of these Russian beds would seem to have
been incompatible with any very great thickness ; but the superfi-
cial extent to which they may be traced is considerable, and they
appear to occupy a tract at least as large as the Principality of
Wales. They increase in thickness as they approach the western
boundary of the Russian empire and pass into Scandinavia.
982. The Norwegian rocks resemble the lower strata of the English
Silurian series in mineral character and fossils. At Christiania there
is a group consisting of dark shale, slate and clay, with calcareous
bands and gritstones overlying them, and passing upwards into
strata of limestone, which abound in corals, and of sandstone, shale,
and conglomerate. The whole series contains fossils identical with
those found in the Caradoc sandstone, and the Llarideilo flags j and
Sir Charles Lyell has observed that, at no great distance, there exists
a limestone rich in fossils, several species of which were of Upper
Silurian types, and others common to both the Upper and Lower
Silurian ; he is, therefore, inclined to consider these beds as forming
a passage between the lower and upper portions of the Older palaeo-
zoic group.
The thickness of the beds in Norway, Sweden, and Gothland is
much greater than in Russia, but gradually diminishes towards the
junction ; and the rocks lose many of their characteristic fossils.
983. In the south of Europe the remains of rocks of this ancient
period are exceedingly rare, but they have been found to exist in the
neighbourhood of the Thracian Bosphorus, not far from Constanti-
nople. Mr. Strickland has described from this locality a mass of
argillaceous schist (sometimes exhibiting slaty cleavage), compact
brown sandstone, and dark blue limestone, all of which pass into
one another by insensible gradations. From the nature of the fos-
sils, these rocks seem to be on a parallel with some of the passage
beds, uniting the lower with the Upper Silurian groups in West-
phalia and Belgium.
984. In North America the older rocks are expanded to a vast
extent, and are of great thickness in many districts to the north and
west. One group, indeed, of beds of shale, limestone, and marl, in
the great valley of the Ohio, is estimated to occupy a surface of
10,000 square miles and, by the evidence of fossils, the whole is
LOWER SILURIAN FOSSILS. 443
referred to the earlier Palaeozoic period. These strata are covered
by compact limestone and shale of great thickness, and are said to
exhibit proofs of contemporaneity with the Ludlow series. Many
other parts of North America are remarkable for the extent to
which the oldest fossiliferous rocks have been there developed ; and
the similarity of the organic remains to European fossils communi-
cates an additional interest to the geology of these extensive groups.
Among other remarkable localities may be mentioned the most
northerly points (far within the Arctic Circle) reached by voyages of
discovery, in tracts where the sea is now frozen during great part of
the year. The existence of fossiliferous limestones of the Palaeozoic
period on the shores of the Icy Sea has been proved by specimens
recently brought to this country as ballast.
Even in the extreme south of the great western continent, in
Tierra del Fuego, similar phenomena have been observed, and it
would appear from recent observations, that the lowest strata in
New Holland exhibit fossils very similar to those found in England.
These are bedded in a coarse ferruginous sandstone, slightly mica-
ceous, and not at all unlike the greywacke of German geologists.
985. " Great interest attaches to the Palaeontology of the Silu-
rians on account of their presenting us with the most ancient forms
of organised beings. Representatives of all the great types of life
are present in them, but not of all the subdivisions. Of the verte-
brata we have only traces of fishes. All the sections of the Mollusca
are present, the Cephalopoda and Brachiopoda prevailing ; Trilobites
are the principal and most characteristic of Crustacea in this form-
ation. Zoophytes are abundant. The Silurians appear to have been
deep-sea formations." *
986. Having now arrived at the close of the Older paleozoic
period, let us look back upon the collective extent of these deposits
considering them in the true order of their formation.
Commencing with the crystalline and altered slates of Cumber-
land and North Wales, it may be observed that the proportion of
argillaceous matter and quartz in these first formed beds is, beyond
all comparison, greater, and the mixture with calcareous rocks less,
than in strata of more recent date. Although of a thickness amount-
ing to many thousand feet, the vast series of sedimentary deposits
forming the assumed base of the Silurian system, may be said to
be, almost without exception, composed of clay and siliceous sand, in
which the mineral character is constantly apparent ; while the pre-
sence of mica seems to indicate a preponderance of granitic rocks
amongst those to whose degradation and disintegration this long
series of crystalline slates, mica-schists, micaceous sandstones, and
quartz rock, must be owing.
* E. Forbes in " Physical Atlas."
444 DESCRIPTIVE GEOLOGY.
987. The unvaried character of these beds over large tracts of
country, and the general resemblance that obtains everywhere among
the oldest sedimentary deposits, has been looked upon as a strong
argument in favour of the uniformity of the materials of which the
original framework of the solid surface of the globe was composed.
It must be remembered, too, that we recognise no such appearance
of uniformity in the igneous and altered rocks of more modern date,
nor in the metamorphic rocks of the Alps, or other mountain dis-
tricts, which, indeed, show no indications that can assist us in deter-
mining the conditions under which the formation of strata, resembling
the Sub-silurian rocks, would be possible. It is the opinion of Pro-
fessor Sedgwick (whose familiar acquaintance with all the* geological
phenomena of the lake district, combined with his profound know-
ledge of crystalline and altered rocks, render him well qualified to offer
an opinion), that the abundance of igneous rocks associated with
slates of mechanical origin in Cumberland and Westmoreland, and
the manner in which they alternate, can only be explained by as-
suming that outbursts of molten rock were repeated, from time to
time, from beneath the bottom of the sea, during the whole period
of the formation of many thousand feet of strata. Such a succession
of volcanic eruptions, and to such an extent, would seem to be
totally unparalleled during the deposit of the secondary strata of our
Isles ; nor is anything of the kind observable in rocks of still more
recent date. It may however appear on further consideration that
the chemical condition of these rocks would be better explained by
some hypothesis of metamorphic action.
988. At the same time, and while this action was going on, other
parts of the ancient seas appear to have been subject to quiet un-
interrupted deposits ; but in every case the general character of the
beds deposited was the same ; and even in the rocks which form the
base of the Silurian system, where the micaceous and sandy flags
contain a few calcareous bands and a moderately large proportion of
carbonate of lime, we can easily recognise the materials of decomposed
granite, originally formed into beds of gneiss and mica schist and
then employed in the composition of these quartzose and micaceous,
but sedimentary and fossiliferous, rocks.
989. On the whole, the history of the Older Silurian period may be
regarded as one of unquiet and restless agitation and change, but
apparently of rapid deposit ; and if, in these strata, we do not see
the actual rocks first formed by the action of water upon the earth,
we are at least introduced to a knowledge of formations more uniform
in their character, more extensive in the area over which they are
deposited, and of a thickness enormously greater, than is the case
with the other and newer Palaeozoic formations ; and the contrast
is still more striking when we bring them into comparison with any
DISTURBANCES OF THE PALJ30ZOIC EPOCH. 445
groups of strata formed during the Later secondary, or the Tertiary
period.
990. The beds of the Upper Silurian system, from the Lower
Wenlock to the Upper Ludlow shales, present, amidst all the dis-
turbances by which they have been affected, an appearance of having
been deposited in seas more tranquil on the whole than those of the
earlier period ; and they exhibit a distinct lithological character, in
which the presence of a considerable quantity of carbonate of lime is
a peculiarity, not more strikingly seen in the Silurian strata of
England than in the contemporaneous rocks of Sweden and Norway,
of Russia, and also of North America. The coralline limestones of
this period offer sufficient proof that a change had taken place ;
although the conditions which governed the duration of species
upon the globe, had not yet been brought into action so completely
as to efface the marks of the preceding and earliest period.
991. The systems of disturbing force referred to the Palaeozoic
period, according to M. Elie de Beaumont's views are four : and
although none of them have produced lofty and important moun-
tain chains, they are not without great interest in various parts of
Europe. The first in order of time is supposed to have originated
between the deposit of the Lower and Upper Silurians, and to have
caused the production of the Westmoreland mountains and the
Hundsruck chain. The direction of this movement is calculated to
have been W. 35 S. by E. 35 N. ; closely approximating there-
fore that of the Cote d'Or, which occurred between the Oolitic and
Greensand periods. This system is recognised in a multitude of
localities in the position and structure of many extensive bands of
gneiss and clay-slate, and it is called the System of Westmoreland and
the Hundsruck.
992. The first clear definition of this very ancient elevation, is
due to the researches of Professor Sedgwick in Westmoreland. Its
recognised range is there very extensive ; as, besides the Westmore-
land hills, it comprises the southern range of Scotland, from St.
Abbs' Head to the Mull of Galloway, the ridges of the Isle of Man,
the slate rocks of Anglesea, mountains in North Wales, and hills
in Cornwall. The ridges of the Hundsruck, of the Eifel, and others
in Nassau, have, notwithstanding their great obscurity, been referred
to this system : but the probability is, especially with regard to
the Hundsruck and the Taunus, that these elevations result from
a long continued action from below, whose force, as remarked by
Professor Sedgwick and Sir R. Murchison, is not yet expended,
showing in the hot springs and bubbling fountains of that region,
indications of feeble and, perhaps, expiring efforts. These heights,
in so far as they belong to the Westmoreland system, must have oh-
446 DESCRIPTIVE GEOLOGY.
ginated previous to the deposition of the Old red sandstone, for the
upturned slates pass uniformly under that system, and it seems likewise
clear that only the earlier Silurians were disturbed and displaced by
the elevating forces. The system is thus, probably, the most ancient
of which our globe can now furnish any traces ; although, as those
disturbed Silurians must themselves have been deposited by the ocean
as the debris of mountains, we have no ground whatever for regard-
ing even this early dislocation as the first action of interior forces
upon the earth's surface. It appears certain, too, that the ranges
De Beaumont has included in the group, are but the slenderest frag-
ment of the changes impressed on the globe by the movement in
which they originated ; for the direction of the upheaved strata
(nearly north-east to south-west) coincides with the prevailing direc-
tion of the ancient strata, although unaccompanied by mountains in
almost every portion of the globe. It is the line along which the old
strata of Northern Russia have been dislocated the great lakes in
that region being transverse splits. Captain Bayfield has noticed
similar facts in North America ; and Humboldt long ago marked
the immense extent of the regions manifesting the presence of this
line of force.
993. System of the Ballons in the Vosges, and of the Bocage in
Calvados. The later Silurian rocks, which show no trace of the
previous dislocation, and which must have been deposited at a subse-
quent period, manifest, in their turn, the action of a force in the direc-
tion E. 15 S. to W. 15 N. ; and with this disturbance also prior
to the epoch of the Old red sandstone various mountain ranges, di-
versely placed, are associated. To these, according to De Beaumont's
first views, belong part of the Vosges ; the hills of the Bocage ; hills
in the south of Ireland, and in Devonshire ; elevations near Magde-
burg ; and probably the older part of the Hartz. The direction is
nearly constant ; inclining, however, towards direct east and west.
994. System of the North of England. From Derby, as far as the
frontier of Scotland, a mountain axis intersects the soil of England,
running almost directly from north to south, or deviating a little
towards north-north-west. The critical discussion of this important
range is another of Professor Sedgwick's numerous contributions to
the higher departments of English geology ; and he has distinctly
shown, that while the Carboniferous system has been upheaved, the
time of the action of the force must have preceded the deposition of
the Lower new red (the Vosges) sandstone. This elevated zone is
chiefly remarkable for its immense faults and slips in the raised
strata ; by means of which its presence can be traced beyond the
sphere of its mere mountain ranges. In close connection with it
are the rocks which pierce and dislocate the local formations from
Shrewsbury as far as Bristol. Nay, that part of the French coast
PALAEOZOIC OCEANS. 447
of the Channel, which runs north and south, intimates, in several
ways, that it was originally a fault, occurring during the time of
the great North of England elevation." *
995. System of Hainault. This system, which is rather shown
by dislocations than by elevations producing a mountain range, is
recognised chiefly in a nearly east and west direction (W. 5 S. by E.
5 N.) across Flanders as far as the western extremity of South
Wales. Its date is supposed to have been between some of the de-
posits of the Permian series, and its results on the coal-measures are
too important to be neglected, especially in the smaller coal-fields of
Western Europe.
996. The distribution of oceans during the Palaeozoic epoch is
hardly to be determined from the present state of our knowledge of
geology. Still it may be considered as probable that some islands
had risen above the water in what is now America. In Africa per-
haps a continent existed, or at least three or four large islands now
forming the three chains to the south and the first indications of
the Atlas chain of Morocco. In Asia from three to five islands
might be counted. Palaeozoic deposits had separated the North of
Europe from its neighbouring continent, and marked out on one
side the first contour of the basins of Australia, Hindostan, China,
and Siberia ; and on the other those of Russia, Scandinavia, Central
Europe, the British Islands, France, and Spain. Europe must have
exhibited ten or eleven peaks or primitive islands above the surface
of those early oceans. t We cannot safely speculate on the position
and extent of other land in those wide tracts of ocean which extend
over so large a part of both hemispheres.
997. It does not appear possible at present to estimate, even in
the roughest manner, the amount of crystalline rock of the epoch we
have been considering in this chapter, and no doubt a very large
proportion of that which is found now included in such deposits is
much more modern than the period itself. The mountain- chains
already mentioned, and others that have lifted the Silurian and car-
boniferous rocks, though not so as to produce distinct ridges, afford
ample proof of ancient metamorphoses resembling those of much more
recent date ; and the condition of some, even of the newer deposits of
the period, had certainly undergone change, and been penetrated with
dykes of crystalline rock even before the close of the Palaeozoic epoch.
998. The views of the older geologists with regard to the anti-
quity of crystalline rock, and especially of certain kinds of granite,
can hardly now be received even to the moderate extent to which
some French writers have recently advocated them, for there is
nothing in the granites and protogine of Mont Blanc or other parts
of the Alpine chain which indicates modern date ; and yet there
* " Physical Atlas," C. 2, p. 7. t Ibid. p. 8.
448 DESCRIPTIVE GEOLOGY.
seems no question that the whole of the Alpine chain without ex-
ception was still below the level of the sea at the termination of the
deposit of the chalk, and even during the accumulations of Tertiary
rocks contemporaneous with our London clay. So completely is this
the case, and so much of the porphyritic rocks occupying the most
prominent place amongst existing deposits is clearly traceable to com-
paratively recent epochs, that there is some difficulty in producing
evidence of the very existence of that really ancient granite which
has been described and often regarded as the very skeleton and
ground-work of the earth.
999. But that large quantities of crystalline rock, as granite and
gneiss, did belong to the Palaeozoic period is proved not only from
the appearance of such rocks thrust through some of the most ancient
deposits and not disturbing others that are more recent, but from the
presence of numerous fragments even in the earliest Silurian rocks
obtained certainly from these sources. The presence of mica and
oth^r materials of granite in old rocks might also have suggested
this, and some gravels even are known whose origin must apparently
be sought for so far back in the earth's history as the early part of
the most ancient epoch. It would no doubt be in the highest degree
interesting and satisfactory to discover also some mineralogical cha-
racter which could mark at once the age of crystalline rocks ; but of
this there is no present probability, and we must be contented to
wait for other evidence less manifest if not less satisfactory.
1000. "No doubt, as M. de Beaumont has observed, granitic
eruptions have become more rare in the more recent epochs, and
doubtless it is most true that in the Newer secondary and Older ter-
tiary formations the granitic rocks become more and more excep-
tional ; but had we lived in the Carboniferous or Permian epochs we
might, I conceive, with equal justice have declared the only granites
then visible to be extremely ancient. The more quartziferous varieties,
together with a certain class of metalliferous veins, posterior in date
to the vegetation of the coal period, such as are now known to the
miners of Cornwall or to those of the Ural Mountains, would then
have been unformed, or at least invisible. The ages which have
elapsed since the coal-measures were accumulated are so countless as
to have afforded ample time for the upheaval of much crystalline
rock and metallic ores from great depths, and for the clearing away
of superficial matter by aqueous denudation. To what an extent
this subsequent denudation has been carried may be shown by ad-
verting to the fact that the masses removed must have more than
equalled in volume all the sedimentary strata newer than the coal, for
some part of the materials of such strata have been more than once
ground down into sand or mud since that period and re-stratified."*
Sir C. Lyell. Anniversary Address to Geol. Soc. for 1850, p. 43.
GENERAL OUTLINE OF THE EARTH'S HISTORY. 449
__ 1001. In bringing to a conclusion this division of our subject
let us now recapitulate briefly those facts and groups of facts that
have passed in review before us, and endeavour thus to make out
the final results of geological investigation.
In the first place, we find that the whole crust of the earth is now,
and probably always has been, exposed to the action of certain forces,
producing a change in its physical condition. One of these forces is
almost exclusively superficial, and acts by wearing away gradually but
steadily every prominence above the water-level, and depositing each
particle in regular order, and ultimately at the sea-bottom. The
oldest rocks as well as the newest exhibit the daily and hourly action
of such causes, while the newest as well as the oldest speak of occa-
sional and far more extensive, but paroxysmal action of somewhat
similar nature. Almost all the members of the extensive series of
stratified rocks have thus been formed, so that we might have expect-
ed, if only these causes had been in action, that there would either be
by this time no inequalities left, or that they were originally so vast
as to have resisted hitherto such energetic and persevering attacks.
1002. Neither of these, however, is the case. Besides this action
of water, there is a counter-action going on beneath the surface
connected with the influence of heat. Perhaps there is not one
spot on the whole surface of the earth that is not at this moment,
and that has not been since its first existence, in a state of move-
ment, oscillating up or down. Every fresh observation tends to
render this more probable, and undulations of this kind, sometimes
amounting only to a few inches in a year, influence and greatly mo-
dify the result of aqueous action. Besides slow movements of this
kind there are, however, other and more manifest changes, and in
the neighbourhood of a volcano there are generally proofs of greater
intensity of subterranean action.
1003. Starting with these ideas of the moving forces employed,
and commencing with the older rocks, we find them to consist of
thick deposits of mud and sand, with limestone, indicating the exis-
tence of a broad expanse of open sea, subject perhaps to great tem-
porary changes of level, and therefore to considerable movement, and
containing a multitude of marine animals, almost exclusively shell-
fish of various kinds, uniform, or very nearly so, over conside-
rable tracts, and exhibiting no marks whatever of the vicinity of
land. To this condition of the sea there succeeded another, in which
fishes of very extraordinary form, and totally different from exist-
ing species, were introduced in great variety and abundance, and
flourished not so much perhaps in the deep sea as in the neighbour-
hood of a coast line then being lifted up above the waters. There
was, perhaps, very little land in any part of the north temperate
zone at the period we are now discussing.
G Q
450 DESCRIPTIVE GEOLOGY.
The elevation in progress during this middle part of the older
period seems to have been succeeded first by a period of depres-
sion, during which coral reefs were built, and then by another ele-
vation, until a number of islands were formed, and became clothed
with a rich and luxuriant vegetation of ferns, palms, and other
trees of singular forms, long since extinct. Perhaps it may explain
the condition of this older period if we consider that the whole of
the latter part of it was one of disturbance and rapid undulation of
surface, admitting of the deposition of those numerous beds of vege-
table matter, which have been since converted into coal.
The termination of the period during which fishes had become of
larger size and more abundant than before, was marked by many
disturbances, producing fracture of the beds, but the disturbances
certainly produced their chief effect after the consolidation of the
strata and the formation of true coal from the vegetable matter
deposited.
1004. We come next to the Secondary or Middle period. A very
long interval indeed must have elapsed between the deposit of coal
and the overlying sandstones, and the Upper new red sandstones,
which we find horizontally bedded, and reposing unconformably in
the upturned edges of the older rocks. During this period there
occurred a total change of the inhabitants of the sea.
In the newer beds we find abundant fossil remains referable to
various animals, including many singular and gigantic reptiles, some
of them constantly inhabiting the sea, and most of them highly
carnivorous, but some organised not merely to live on shore but on
vegetable food, and expressly adapted for conditions resembling
those under which the hippopotamus, rhinoceros, and elephant
exist. Besides these marine and terrestrial reptiles we have, however,
a third group, representing the birds, and proving how perfectly
animals having all the typical peculiarities of the most highly
organised class, though the lowest of that class, could be adapted to
exist not only on land and in the sea, but also in the air. With
these animals we find although they are very sparingly distributed
indications of the existence of quadrupeds and birds, and from
time to time such other evidence of land, that we may be certain of
there having been a considerable elevation of the sea-bottom since
the deposit of the sandy beds which repose directly on the coal.
Still there are, so far as we can tell, no marks of an extensive tract
of land in any way resembling that which now exists in the northern
hemisphere. The land during this period was probably distributed
in a totally different manner, being certainly adapted for races of
animals distinct, not only in general form but in many details of
structure, from those which have since replaced, or which now
represent them.
GENERAL OUTLINE OF THE EARTH'S HISTORY. 451
The land, however, probably increased on the whole, rather
than diminished in these latitudes, during the deposit of the Oolitic
rocks, and towards the close there was formed that enormous mass
of freshwater or estuary origin, which we find in the South-east of
England, and which geologists denominate Wealden. This, however,
was followed by a depression, at first, perhaps, alternating with ele-
vations, but soon increasing and becoming considerable, while a
multitude of marine animals secreted enormous quantities of calca-
reous matter, and deposited it at the sea-bottom, in the beds which
have since become chalk. The animals whose remains occur in chalk,
are chiefly those which require deep water, and the very considerable
area over which they are uniformly spread renders it probable that
the circumstances throughout were similar.
1005. At length, but not till after a very long interval, the vast
ocean-floor was broken up, and outbursts of lava hardened and partly
covered the chalk of the North of Ireland, and extended to the
islands of Scotland. Similar eruptions produced analogous effects
elsewhere, while a great line of intense subterranean action lifted up
the beds in the South of England, gave the prevailing direction to
the Pyrenees, the Alps, and the Carpathians, and produced, perhaps,
a very extensive tract of dry land on the southern side, and a few
islands on the north.
1006. About the same time, or not long afterwards, the elevation
of the Himalayans commenced, producing a somewhat similar tract,
but between the two, in Egypt and in Western India, there seems to
have been a deep sea. From this time elevation and depression
must have both gone on over parts of Europe and Asia on an exten-
sive scale, the land that extended westwards and southwards sink-
ing down rapidly, while Northern Europe became nearly covered
with an extensive open but shallow sea, in which were deposited
the sandy and muddy beds of the great existing river- valleys.
Afterwards, elevation again took place, and the existing physical
features of Europe were produced; and while the greater part not
only of Europe but of Northern Asia, was the resort of innumerable
herds of elephants and large cervine animals, the swamps and
marshes were the abode of rhinoceroses and hippopotamuses, numerous
lions and tigers roaming about the forests and plains, associated with
hyaenas and bears. After this, there was a continuation of the ele-
vating process towards the north pole, and a great extension of land
in that direction, so that an almost icy sea extended down nearly
to the central countries of Europe, and enormous icebergs floated
over a great part of the existing land, there depositing the gravel
which had been removed from distant spots, and was often collected
from more than one locality. Another elevation of this part, and a
corresponding depression northward, again changed the inhabitants
452 DESCRIPTIVE GEOLOGY.
and the whole coast line ; and, probably, the present distribution of
land was the result. Lastly, we have, now going on, an elevation in
Northern Europe and a depression in our own latitudes, the result of
which will be to lower the mean annual temperature, although it may
possibly be that the climate will become more equalised in conse-
quence of the slight depressions of the general level.
1007. Such, then, are some of the results of geological investiga-
tion with regard to the changes that have taken place on the earth's .
crust and the successive races that have been its tenants. Exhibit- .
ing results so important, Descriptive Geology cannot now be looked
upon as a subject only fit to be argued and discussed, but must be >
carefully studied. It is a distinct and important pursuit ; its problems ''
involve the highest and most philosophical views of general Natural
History, and of the application of mathematical science. Its con-
clusions are sound and permanent, and its object simple and definite.
The Geologist takes up every branch of descriptive Natural History,
and suggests the laws by which the most obscure of Nature's opera-
tions have been conducted. He makes observations by which the
truth of such laws must be tested, and he accounts satisfactorily
for a multitude of natural phenomena not otherwise to be explained,
giving, in fact, a true and connected history, not only of the earth
itself, but of events that have taken place upon and beneath its sur-
face, and that have influenced its progress towards the condition in
which we now see and study its surface.
And it cannot be that such a history should be known and not
produce important results with regard to those operations that are
carried on by man either upon the earth or in the deep recesses
to which he is able to penetrate. As all such operations necessarily
and immediately depend on the structure and contents of the solid
crust exposed for our investigation, a knowledge of the laws accord-
ing to which the various parts of that crust have been originally
formed and since modified is in the highest degree important.
Geology is no less needed by the engineer and the miner than astro-
nomy is by the mariner. All calculations must be made, all new
works undertaken, and all old ones continued, in accordance with
what is believed to be the structure of rocks, and a knowledge of
structure is obtained only by geological investigation.
PART IV.
PRACTICAL GEOLOGY.
CHAPTER XVIII.
ON THE APPLICATION" OF GEOLOGY TO AGRICULTURE,
ENGINEERING, AND ARCHITECTURE.
1008. IF the Reader has made himself acquainted with the facts of
Geology, or in other words, if he understands the nature of the mate-
rials of which the earth's crust is made up, the order of arrangement
of those materials, and the changes undergone both in the actual
rocks themselves, and in the position they occupy, he will not be in-
clined to question the value of such knowledge to practical men ; or
the nature of the applications of Geology to practical purposes. Such
knowledge must always be available when any thing is undertaken
concerning the earth, either as the basis of operations, or the source
whence all valuable materials are obtained. It may be well, how-
ever, to illustrate this point by a few simple examples.
1009. Regarding the earth first as the basis of operations, it is
well known to every engineer that the whole management of earth-
works, whether for roads or intrenchments, whether in cuttings, tun-
nelling, or embankments, must be greatly influenced by the nature
of the soil, the subsoil, and the underlying rocks ; the latter di-
rectly modifying the former, and being the original and fundamental
cause of all peculiarities of condition. The permanence of any struc-
ture also must, in like manner, depend on the rock in or on which
the foundation is placed, and thus requires a consideration of geo-
logical position ; while questions of drainage and the source of water
supply, both for the use of towns and in agricultural districts,
directly depend on the geological constitution of each locality, since
without reference to so essential a point the principles of science
concerning these matters cannot properly be applied. It is only
454 PRACTICAL GEOLOGY.
within a few years perhaps that such an application has been made,
but the numerous reports concerning the drainage of towns that
have lately appeared, show at once the admitted necessity of some-
thing of the kind ; and in too many cases they have afforded ex-
amples of the want of an acquaintance with the first principles of
Geology on the part of the engineer.
1010. As to material again, it is clear that all substances derived
from the earth should be studied, at least in some measure, in the
place where they occur in a natural state ; and no one is really
capable of judging concerning the value of material without know-
ing something of its history. This applies to agriculturists, who
should know whence soils are derived, and where to look for desir-
able rocks for mingling with others at the surface : to land-valuers,
who ought to be well acquainted with the causes of improvement or
deterioration that may be at hand to affect the value of the property
they estimate : to builders, who require to select the material after-
wards to be used for buildings : to architects and engineers, who
arrange plans dependent for success on the nature of the ground
and that which is beneath it, and its reference to the structure to be
erected upon it : and above all to miners, whose business is chiefly
confined to rocks generally concealed, and who most of all require
a knowledge of laws and conditions, of facts and inferences, concern-
ing the materials of which the earth is constructed, and the circum-
stances under which these materials are generally present.
1011. The facts of Geology which are most important to be
known are chiefly these which relate to structure, involving the
mechanical condition, the chemical composition, and the mechanical
position of rocks. These are all points which must be learnt, not
only by reading and description, but to some extent by actual per-
sonal knowledge ; and no acquaintance with Geology is useful
which is not based on actual observation and investigation. A
single real attempt, however apparently unsuccessful, to map a coun-
try geologically, and draw a section that shall explain the map, will
be of more value than any amount of knowledge of what other people
have effected. Without books, however, to enable the student to set
out in the right direction, but little progress is made, and mistakes
are inevitable,
1012. Although the facts of Geology have been mentioned at some
length in preceding chapters, it may be well to recapitulate a few
of them here very briefly. Thus the first series, those of mechanical
condition, are taught by the natural history definitions of rocks,
and may be described as including their hardness or softness;
brittleness or toughness ; permeability or impermeability to water
their composition as simple rocks, as limestones ; or compound
rocks, as marls and conglomerates ; their texture, whether fine or
AGRICULTURAL GEOLOGY. 455
coarse, compact or loose, crystalline or massive ; and their specific
gravity : these all being points which may be considered as me-
chanical, with reference to masses of rock.
1013. The facts of chemical composition are also important and
varied. They include a knowledge not only of the prevailing
simple mineral, but the associated minerals ; the way in which the
minerals are combined and modified ; the probability of disintegra-
tion and decomposition under exposure of certain kinds ; and the
degree of metamorphic action that rocks have undergone or are
undergoing.
1014. The facts of mechanical position involve the actual position
of stratified masses with respect to the horizon, with respect to
other strata, and with respect to crystalline and unstratified masses.
These are known when the dip and strike, the nature and posi-
tion of the anticlinal and synclinal axes, the systems of faults, and
the various discordances of stratification in a district, are fully made
out. All these facts are learnt by observation ; they are quite inde-
pendent of any controverted points; they offer, perhaps, little of
the romance of Geology to the general reader, but they come home
to every-day life, and no man can be an engineer or a miner, none
can safely pursue agriculture, or rightly carry out sanitary princi-
ples in the construction of a house, a public building, or a town,
without knowing them and acting upon them.
1015. The object in this and the subsequent chapter is merely to give a very brief
and general outline of the application of these facts. The subject admits of much
more extended treatment, and the author has it in view to prepare a more complete
and useful system of Practical Geology. He has already, in a former work,* entered
at some length on various points of interest connected with it, and here only introduces
it as an essential part of an outline of Geology, and as affording opportunity for a
statement of the plan he thinks it advisable to adopt.
1. Agricultural Geology.
1016. The formation of soils is a subject of great interest in
connection with geological structure, and can only be properly
understood by reference to the action of the atmosphere and water
in producing the disintegration and decomposition of various rocks,
together with a due consideration of the way in which a vegetable
soil is derived from a subsoil containing no vegetable ingredients
and this latter from a rock. In many cases the sources whence the
peculiar properties of a soil are derived, and whether these are favour-
able or unfavourable to vegetation, is by no means manifest, and
instances not unfrequently occur where knowledge of this kind
would be exceedingly and immediately useful.
1017. A geological map represents, by systems of colours, a num-
ber of geological facts concerning the rocks of a certain district or
* Ansted's " Geology," 2 vols. 1844.
456 PRACTICAL GEOLOGY.
country, and it is very important to remember, that it neither does
nor professes more than this. It does not, for example, give any
account of the mechanical condition or the chemical composition of
rocks, and no complete account, in most cases, even of the details
of mechanical position ; still less does it indicate the nature of the
subsoil or decomposed rock overlying the principal mass ; and least
of all does it give any idea of the nature of the soil. Combined with
sections, it teaches something more concerning the magnitude of the
rocks and their mechanical position, and perhaps something of the
thickness of the overlying soil and subsoil, and with the accompany-
ing description, if there is one, the actual nature of the rocks is
mentioned. It may seem from this account that to the agricul-
turist such a map would be either useless or mischievous, either
teaching him nothing or telling a falsehood, for he has only or
chiefly to do with the surface, and cannot understand that he may
have a tough clay soil where the map marks " oolite " a loose sand,
where he is led to expect " London clay ;" a rich grey marl in the
" old red sandstone," or other similar anomalies. Still he must not
suppose that the map is without its use. The names, perhaps, are
unfortunate, as being only locally descriptive, but the story told is
true and exceedingly useful when understood, for it really enables
the practical man to discover readily what he ought to know, and is
highly suggestive with regard to the most important facts that bear
upon surface operations.
1018. In a former chapter an account has been given of the com-
ponent parts and structure of rocks, and it is quite certain that in
most cases the subsoil is immediately, and the soil intermediately,
derived from the decomposition of the subjacent rock, so that the
fertility of land depends on geological structure. It would, also,
be easy to show that, by taking advantage of the presence of certain
mineral substances beneath the surface, a soil naturally barren may
often be rendered fertile. The whole subject of mineral manures
consists in the proper employment of such substances as may coun-
teract the injurious qualities of a barren or poor soil, and either
supply the want of some indispensable element of the plant to be
cultivated, or prepare the soil to receive those atmospheric influences
which are essential to the development of vegetable life.
1019. There are two modes in which derivation from another
rock may be traced ; for sometimes a soil consists of nothing more
than the minutely divided particles of one simple rock, as sand,
while in other examples the soil exhibits an admixture of carbon,
and of various mineral substances not easily traceable. It not unfre-
quently happens that rain, penetrating the minute surface-crevices
of an exposed rock, aided by frost, crumbles down the hardest mate-
rials, and, if these crumbled portions are washed away, they are
EELATION OP SOIL TO ROCK. 457
rapidly succeeded by others, so that a soil is formed, which at length,
under favourable circumstances, becomes covered by mosses and
lichens, from whose decay is obtained that supply of carbon and
other materials which in process of time renders the soil fit for the
growth of other vegetables which are useful to man.*
1020. The dependence of a soil on the underlying rock extends
even to its colour, which is white in chalky soils, red on the New
red sandstone and the ochraceous beds of the Greensand, and yellow
on the clays and clay-slate, &c. : but it will not be expected that
these conditions should hold when there is a thick bed of superficial
detritus, such as gravel ; for the gravel must then be looked upon
as the parent rock, and the condition of the soil will be influenced
by the actual underlying bed.
1021. There are one or two general principles with regard to this part of the sub-
ject, Vvhich it may be worth while here to enunciate, but which it will not be neces-
sary to enlarge upon or illustrate.
The depth of a soil is chiefly dependent on the nature of the subjacent rock, and on
its ready decomposability by atmospheric agents.
The texture of a soil also depends on the parent rock, as to whether it shall be loose
and gritty, or tough and clayey, and varies according to the tendency of the rock to
decompose and the manner in which it is affected by decomposition.
The fertility of a soil depends partly on its depth and texture, and partly on its
possessing those mineral constituents which enter into the structure of the plants to
be grown upon it.
The use of the soil in enabling plants to grow is twofold : first mechanical, the soil
affording the plant a firm foundation, and enabling its roots to take up certain quan-
tities of organic and inorganic substances necessary for its nutriment ; and secondly
chemical, inasmuch as all plants, without exception, possess a certain amount of
inorganic as well as organic constituents, which after undergoing decomposition and
entering into new combinations are taken up from the soil, and assimilated for the
use of the living vegetable. These substances are required also to be present in the
soil in such a state that the roots of the plants are able to absorb them.
1022. Liebig states it as distinctly proved, in analyses made by
De Saussure and Berthier, that the nature of a soil exercises a
decided influence on the quantity of the different metallic oxides
contained in the plants which grow upon it,t but it does not fol-
low thence that the actual quantity of alkaline bases varies ; and it
appears, on the contrary, from other investigations, that the total
amount of oxygen united to these bases is always the same in the
same plant, and therefore that the proper quantity of some of them
as bases is essentially necessary; the growth of the plant being
arrested when these substances are wanting, and much impeded when
they are deficient.
The alkalies are often supplied to the soil by rain-water, where
they are certainly present, although it is not known in what form
they exist. Besides these mineral substances, and some others, the
* The amount of organic matter required to give fertility to a soil varies from three to ten
per cent,
t Organic Chemistry, p. 95.
458 PRACTICAL GEOLOGY.
presence of carbon is absolutely necessary, as before-mentioned ; and
the action of the weather, the absorption of rain-water, and, above
all, the chemical changes constantly going on in the process of
gradual oxidation (the oxygen being obtained from the atmosphere),
effect the necessary alterations in the different constituents of the
soil, and render it fit to support vegetable life.
1023. Some plants, as the grasses, require a considerable quantity of silex for their
proper growth and nourishment ; and this, which is chiefly present in the stalk, is
supplied in the form of silicate of potash. But the grasses also require phosphate of
magnesia, which is an invariable constituent of their seeds ; and thus the presence of
phosphorus, potash, silica, and magnesia in the soil is absolutely necessary for the
proper growth and ripening of a crop of wheat. Other plants possess other salts and
alkaline bases, and in different proportions, and all these substances require to be
presented to the roots of the vegetable in the most convenient form for absorption.
1024. It will now be seen in what way the soil acts, and how far
vegetation depends on the actual materials of which the soil is
composed. If any of the constituent parts are wanting, they may
usually be supplied at no very great distance, and it is chiefly such
soils as do not suffer decomposition that are necessarily and hope-
lessly barren ; but these are so few, that they need hardly be the
subject of consideration.
Perhaps one of the most common examples of an ordinary barren
soil is that in which the soil is composed of silex, either pure and
in the form of compact rock, or made up of loose grains of sand,
mingled only with a certain proportion of alumina and oxide of
iron not sufficient to admit of the ready growth of plants. Such
soils as this are to be found on some parts of the coast of Flanders ;
they occupy also the tops of some hills and mountains of igneous
origin, and they certainly offer no prospect of return for labour
bestowed upon them in such situations. But in the interior of a
country where heath and furze once plant themselves and nourish,
although there may be at first little prospect of success to the agri-
culturist, the case is by no means hopeless ; and the vicinity of clay
might often be taken advantage of to bring these districts into pro-
fitable cultivation. The alumina and lime in such case may be
supplied artificially, and the other constituents may often be ob-
tained from the decayed and decomposed plants which have grown
upon the spot. It is unnecessary to say that sandy beds allow the
moisture to traverse them very readily, and are soon heated, so that
the crops grown upon them suffer greatly from drought. This must
be to a certain extent unavoidable.
1025. Stiff clay, unmixed with a sufficient quantity of silica in
the form of loose sand, is sometimes extremely difficult and trouble-
some to bring into cultivation. The chief want here to be supplied
is that of lime ; for there is always abundance of silex, although
not in the best or most convenient form. The stiffest clayey beds,
SOURCE OF FERTILITY IN SOILS. 459
when dressed with lime, are readily made to bear valuable crops ;
but, as the clay is exceedingly retentive of water, and yields it back
to the atmosphere with great difficulty and very slowly, it is often
necessary that artificial drainage should accompany whatever other
method may be adopted for the bringing such soils into cultivation.
The agency of frost in breaking up stiff clays is often of great im-
portance.
102G. Limestone, when pure, or nearly pure, as in the state of
chalk or crystalline limestone, is often a barren rock ; and this is
especially the case when it is exposed on a hill-top, where the rain is
unable to transport argillaceous portions from adjacent clayey beds.
An admixture of clay, however, converts decomposed limestone or
chalk into marl, and in this state it becomes an admirable soil.
Magnesia is also a very common, and almost necessary, constituent
of soils to a certain small extent.
1027. It is worth while remarking here, that the lime and magnesia, as well as the
potash and soda found in soils, are all of great importance, and form bases which,
when mixed with oxygen are in a condition to be absorbed by plants to whose
growth they are essential. None of these earths however alone, nor indeed any two
of them, even when associated with carbon, are sufficient to form a productive soil ;
and, besides being mingled in the proper proportions, it is necessary also that the
mixture should possess a proper texture, adjusted to the quantity of rain that is likely
to fall ; for without this the air is not properly supplied to the root of the plant, and
the process of oxidation, effected during the slow decomposition of this air, and upon
which the growth of the plant seems to depend, does not commence, so that the plant
is either parched for want of moisture, or stifled for want of air. As a general rule, it
has been noticed that more rain falls on mountainous districts than in plains ; and
this exactly answers to the usual position of clayey soils in plains and valleys, and a
freer and more open soil on the high ground.
1028. With regard to the relative value of different geological
formations in agriculture, no general rules can be laid down j and as
it is rather the mineral and physical character than the geological
age, the determination of which is important, the Geologist can only
bring his knowledge to bear in any given instance when he has in-
formed himself of the actual structure of the district.
1029. Before concluding this subject it is right to add a few re-
marks on the determination of the value of land, and the advantage
of an adequate knowledge of Geology in attaining this result.
Where an estate is situated on several beds cropping out in suc-
cession, and of different agricultural value, a person ignorant of Geo-
logy would be greatly puzzled to determine the value of the estate ;
and it would present appearances extremely different if the surveyor
first walked across it in the direction of the dip, and afterwards on
the strike.
In order to obtain a true notion of the value, subdivisions of the
property must be made, and the arranging these would be greatly
facilitated by knowing the lines of out- crop of the different strata.
460 PRACTICAL GEOLOGY.
But, besides enabling the land-agent to do this, and to identify the
various soils with the general productiveness of which in other places
he should be acquainted, Geology would point out what land is in a
forced, exhausted, or ordinary state of cultivation ; while from the
mineral structure of the subjacent rock the composition of the soil
may be inferred, and any substance detrimental or favourable to
vegetation be detected.
1030. "A surveyor, therefore, should be acquainted with the na-
ture and extent of the geological formations, especially those in the
more immediate sphere of his duties ; and in acquiring, as well as
applying this knowledge, he would be much aided by good geologi-
cal maps. He should, also, make himself thoroughly acquainted
with the relative productiveness of the soils on these formations ;
and in valuing an estate, he should observe the texture of the soil
and subsoil, the dip and compactness of the strata, and the form
of the surface of the land ; all these circumstances greatly affecting
the value of landed property."*
2. Drainage.
1031. Drainage is, in many important respects, a truly agricul-
tural subject, for no land can be well cultivated which is not pro-
perly drained, and no drainage can be properly effected without some
reference to the geological structure of the district.
The drainage of an island or continent is effected, under ordinary
circumstances, by means of a gradual and usually gentle inclination
of the surface of the country towards a river-valley, a lake, or a
coast-line. The rain which falls on the various parts being con-
ducted by channels, or rushing down the hill-sides into brooks, is by
them conveyed to the neighbouring rivers, and these, descending into
and traversing the plains, at length reach the sea ; the rate of mo-
tion of the waters in all these channels necessarily depending on the
amount of the fall, and the relation it bears to the distance traversed
during the whole course of the stream from the high ground to the sea.
1032. Now there are two points in this statement which deserve
attention, namely, first, that the rate of motion, or the velocity of
the current, has reference to the distance traversed, as well as the
amount of fall ; and next, that after the water has been conducted to
the foot of the hills, on whose surface it has been partly collected, it
frequently has to traverse a large extent of country nearly horizontal,
or in which the descent towards the sea is hardly appreciable. Both
these points must be evident to every one who considers the subject ;
for the latter is simply a statement of fact, which may be verified by
referring to almost any map ; and the former is equally clear ; for if
a river has to traverse a certain tract of country in a direct line to
* " Whitley's Application of Geology to Agriculture," p. 143.
DRAINAGE. 461
the sea, with a given amount of fall, then if the distance traversed
is increased by means of the sinuosities of the channel through
which the water is obliged to pass, the rate of motion must evidently
be diminished.
1033. In those cases in which an extensive tract of nearly flat
land (its elevation not being much above the level of high-water) is
traversed by a number of streams, nearly stagnant for want of a suf-
ficient fall to carry off the water, there is an evident tendency to
form swampy and marsh land, and the slightest accident may at any
time produce this result, and lay under water a whole district.
1034. But there are other cases of a totally different kind, in
which the long continuance of moisture on the soil is exceedingly
injurious, and prevents cultivation. Among the most remarkable of
these must be ranked those numerous instances of peat-bog which are
so common in Ireland and in many other countries, where the water
is retained partly or entirely beneath a thick tough coating of vege-
table soil, made up of the matted roots of plants. The drainage of
bogs in this condition requires, as may be supposed, a process quite
different from that which would succeed with fen-lands ; and most
of the cases in which it is required to improve land by drainage will
be found to refer either to the class just described, or to that of which
the fens offer the best example.
1035. The very fact of stratification itself, and the manner in
which the subsoil and the soil are derived by decomposition from the
underlying rock, afford a ready explanation of the well-drained con-
dition of the soil in any district that is tolerably fertile. Drainage
is indeed a natural result of the existence of alternating strata of
different materials, some (as sandy beds) allowing water to penetrate
them freely, others (as the clays) resisting its passage, and others
again (as many limestones) admitting the water by numerous cracks
and fissures into reservoirs and subterraneous caverns, but not ab-
sorbing it except near the place of contact, and remaining elsewhere
comparatively dry and unchanged.
1036. All these different beds occurring at intervals, and being
covered up by the subsoil, which rarely resists the passage of water
through it, the surface-water, when in excess, penetrates into the sub-
soil, and is thence carried down till it reaches a permeable stratum,
where it is absorbed and swallowed up, unless, indeed, as sometimes
happens, this bed is already sufficiently loaded with water, and can
no longer receive it. There are thus two very different conditions
under which the natural soil of a district may be rendered infertile
by the presence of stagnant water, and in like manner there are two
ways in which drainage may be effected, the one of which is called
surface and the other deep-draining. By the former is meant the
carrying off the water by drains cut upon the surface, while the lat-
462 PRACTICAL GEOLOGY.
ter depends rather upon the geological condition of the underlying
rock.
1037. Besides the ordinary conditions of stratified rocks, the
faults, or results of the disturbances of strata, may also occasionally
assist the agriculturist in the drainage of land, for some of these
faults are pervious to water, and act as main drains to large portions
of country, while others, again, are filled with clay, and keep in the
water on one side of the fault, preventing its passage to the other.
In either case advantage may often be taken of the fault by any one
possessed of an adequate knowledge of Geology.
1038. As a fit conclusion to this part of the subject, in which
drainage has been considered as connected with agriculture, there are
added here some interesting remarks by Mr. Johnston, abstracted
from his Lectures on Agricultural Chemistry (p. 440).
The advantages of drainage to the agriculturist are numerous
and manifest. In the first place it carries away rapidly the super-
fluous moisture, moderates the natural dampness of the climate in a
wet, boggy country, and is equivalent, therefore, not only to a change
of soil, but also to a change of climate, both with reference to the
growth of plants and the health of the population.
Drainage produces, also, the effect of an actual deepening of the
soil, as it facilitates deep ploughing, and permits a greater absorp-
tion of useful moisture, and useful mineral salts, or organic matter,
while it is also the means of noxious mineral compounds, such as
the salts of iron, being diffused equally and harmlessly through the
soil, or carried away before they have time to form those ferruginous
compounds which are injurious as an impervious subsoil.
Drainage also alters the direction of the currents which occur in
wet soils, the roots of plants obtaining their moisture from the rain
which falls on the surface in drained lands, whereas in deep swampy
ground, their spongioles are only supplied with exhausted subsoil
water.
Lastly, it is a necessary preparation to many other means of im-
provement which may be applied to land, and must in all cases be
preliminary to every kind of building and engineering work, as no
foundation can be stable, and no situation good, in which the water
is allowed to remain and accumulate on a retentive soil.
1039. The process of deep draining differs from that of surface-
draining already described, and has for its object a somewhat diffe-
rent result. It is also connected with the subject of road and canal-
making, and requires to be understood and carefully attended to by
the engineer, for without such attention a canal may be useless, after
all the expense of construction has been incurred ; and a line of road
may be so dangerous as seriously to interfere with the traffic
upon it.
CANAL-MAKING. 463
1040. In the case of road-cuttings, and especially deep cuttings for
railways, and also in tunnelling and shaft-sinking, a familiar ac-
quaintance with the principles of Geology, and a knowledge of the
structure of the earth may be, and of late years often have been, of
very essential advantage. Where bands of sand, or any soluble or
easily-moved material, are crossed by such cuttings, and contain or
transmit water, the position of the outcrop requires to be known to
prevent mischief from slips, and in all cases the slopes of a cutting
should be formed with reference to the dip of the strata, especially
when the cutting is at all in the direction of their strike.
1041. The importance of geological knowledge in canal-making
was long ago recognised, and was applied by Mr.W. Smith, in 1811, in
a very successful manner. About that time many canals were being
cut in the West of England, and these, crossing the Oolitic hills, were
found to be particularly liable to accidents of leakage, being cut
through open-jointed, and sometimes cavernous rocks, alternating
with water-tight clays. In the passage across the former rocks, and
more especially when the summit level of the canal occurs in them,
the water escapes almost as fast as it enters, and all the skill of the
engineer in puddling, and making an artificial bed, is sometimes
exerted in vain, and cannot prevent great and ruinous loss. But
the existence of open joints and caverns is by no means the only,
nor, indeed, is it the greatest source of injury, for innumerable small
faults or slides traverse the country and confuse the natural direc-
tion of the springs, rendering them short in their courses, and uncer-
tain and temporary in their flow, weakening, by their irregular
pressure every defence that may be opposed to them, and causing
leaks, which let through a portion of the water contained in that
level of the canal.
1 042. The general remedy for all these evils was understood by
Mr. Smith, and proposed by him for adoption. It is " the entire
interception of all the springs which rise from a level above the
canal and pass below it through natural fissures and cavities. This
is a process requiring great skill and extensive experience ; some of
the springs, for instance, which it is most important to intercept
come not to the surface at all in the ground above the canal, but
flowing naturally below the surface through shaken or faulty ground,
or along masses of displaced rock which extend in long ribs from
the brows down into the vale, emerge or attempt to emerge in the
banks of the canal ; these no ordinary surface-draining will reach,
and none but a draining-engineer, well versed in the knowledge of
strata, can successfully cope with such mysterious enemies. But
Mr. Smith, confident in his great experience, not only proposed, by
a general system of subterraneous excavation to intercept all these
springs, and destroy their power to injure the canal, but further, to
464 PRACTICAL GEOLOGY.
regulate and equalize their discharge, so as to render them a posi-
tive benefit. This he would have accomplished by penning up the
water in particular natural areas, or pounds, which really exist be-
tween lines of fault in most districts, or between certain ridges of
clay ('horses,') which interrupt the continuity of the rock, and divide
the subterranean water-fields into limited districts, separately ma-
nageable for the advantage of man by the skilful adaptation of
science."*
1043. This account of the nature of the work required in subter-
ranean drainage is so much to the purpose that I need add little
further in illustration of the subject. The principles involved must
in most cases be nearly the same, and whether it is required to pre-
vent a canal from leaking, or a deep cutting or tunnel from being
drowned, or whether, finally, it is the object to prevent that wash-
ing away of a thin intermediate stratum, by the absence of which
an upper bed will be enabled to slide upon a lower one and produce
a landslip, the general nature of the contrivances to be adopted dif-
fers but little, although the particular method must in all cases be
strictly adapted to the special conditions involved, and must vary in
every district. It is only by a clear and accurate comprehension of
the actual cause in each instance, that the draining-engineer can hope
to succeed, whether in combating an evil that already exists, or
preventing an accident that is foreseen.
3. On Water-supply from Rocks.
1044. The distribution of water within the crust of the earth, is a
subject of very great interest to the engineer and miner, and not less
so to the agriculturist, while the condition in which water is present
in the earth, the substances held in solution or suspension, and the
circumstances under which it can be extracted, are questions worthy
of the closest and most careful consideration, with reference to the
supply of water to towns for household and sanitary purposes.
1045. The atmosphere is well known to be the main agent em-
ployed by Nature in the distribution of moisture upon the earth,
absorbing a considerable quantity of water in its passage over the
sea, and afterwards depositing it in the form of rain, owing to changes
which take place in its temperature, and, probably, in its electrical
condition. Of the 'quantity of rain, however, which falls upon the
earth in a given spot, only a small proportion finds its way to the
sea directly and immediately, by means of rivers ; and it has been
calculated by M. Arago that this proportion in the valley of the Seine
is not more than one-third. Of the rest, some portion is, no doubt,
re-absorbed by the atmosphere, and some enters immediately into the
composition of plants and animals ; but a large quantity remains,
* Phillips' Life of William Smith, p. 69.
WATER CONTAINED IN EOCKS. 465
and this descends into the bowels of the earth by means of those
strata which are permeable to water, and it is either retained in them
until they are full, and then poured over their edges into the neigh-
bouring country, to feed the nearest stream or is discharged in the
form of perennial springs, where the containing stratum is exposed
on a hill-side ; or, lastly, is accumulated in the substance of the rock
or in reservoirs, whence it is discharged by some natural or artificial
communication being made to the surface at a lower level.
1046. Rocks, however, vary greatly in the quantity of water they
retain, in the way in which they retain it, in the relative facility
with which they absorb or part with it, and in the degree of acci-
dental interruption that can interfere with the free course of the
water beneath the surface. Thus sands, if loose, allow water to
percolate freely through them ; if hardened, they conduct water very
badly, or not at all ; if broken, they offer natural channels, permit-
ting a very perfect but partial transmission. So limestones, under
certain circumstances, are good conductors ; and, under other circum-
stances, very bad conductors of water : and this is governed by the
nature of the rock, its condition, its position, and generally by those
facts observed and described by the Geologist. Even clays, although
generally tough and quite impermeable, retaining water to any
extent, are sometimes broken by permeable joints, and sometimes are
mixed with so much sand and lime as not to be absolutely close.
1047. Few experiments appear to have been made with reference
to this very important subject. All rocks indeed are known to con-
tain water ; and, so general is this, that many ignorant or half in-
formed persons, think it only necessary to bore to some depth beneath
the surface in any spot in order to discover a spring. The frequent
disappointments in such cases afford proof of the necessity of using
some judgment in the matter j but the more frequent success, how-
ever partial, affords the best evidence of the presence of water gene-
rally at all moderate depths beneath the surface. It is of the utmost
importance to know, as far as possible, the condition of various rocks
in this respect.
1048. Natural springs occur (1) in surface-rocks of loose and open
texture, as sand and gravel fully saturated with water, and not covered
by impermeable beds : these are called land-springs, and cannot rise
above the surface ; (2) at the outcrop or intersection of fully saturated
permeable beds lying between beds more or less impermeable : these
are not uncommon, and often when reached by bore-holes, yield Ar-
tesian springs rising to the surface, though they can rarely be de-
pended on for a large and permanent supply of water ; (3) at the
natural or artificial intersection of a permeable resting on an imper-
meable bed, the former not requiring to be fully saturated to yield
springs : this occurs commonly at sea-cliffs and cuttings, when the
H H
466 PRACTICAL GEOLOGY.
slope of the beds is towards the cliff or cutting ; (4) at open faults,
where the natural descent of a wet bed of loose texture is stopped,
and the water rises nearly to its former level, often in this way pro-
ducing natural Artesian springs ; (5) at anticlinal axes, owing to
pressure from below, probably connected with chemical action :
this and the former case frequently resulting in mineral springs,
sometimes of high temperature. Besides these, which may be re-
garded as natural causes of springs, artificial supplies of water may
often be obtained by penetrating through surface deposits to wet,
permeable beds, occurring between impermeable beds, and receiving
their supplies from a higher level than that reached by the boring ;
or by piercing natural reservoirs or open channels in impermeable
rocks, supplied also from a higher level, and by channels full of water
and producing pressure.
1049. Artesian wells are so called from the French province of Artois, where, so
far back as at the beginning of the twelfth century, it was the custom to obtain
springs of water artificially by piercing the soil to a certain depth in places where no
indication of springs existed at the surface. When, therefore, in other districts water
is obtained by boring, and the water thus reached rises to the surface, or attains a
considerable height in the well, the term Artesian is applied, and serves to distin-
guish these springs from others which flow on a hill-side, or at faults, or in which
there is no tendency to rise above the level of the water-containing bed, or natural
underground reservoir. Dr. Buckland has indeed proposed to limit the term to those
wells in which the water rises above the surface ; but the proximity to the surface to
which the water will rise is so entirely dependent on irregularities of surface that such
a limitation could only induce confusion, and we greatly prefer the more general and
recognised definition.
1050. Of the different kinds of rocks met with in nature, sands
and gravels may be considered the most open, but both require care-
ful examination if we would discover their true condition. Thus,
many sand rocks, although themselves loose and containing much
water with which they would readily part, have undergone a partial
consolidation, or are traversed by a multitude of crevices, and some-
times by systems of faults parallel to each other, filled up with clay,
quartz, or oxide of iron, and crossed by others at right angles to them.
The whole mass of rock is thus divided into compartments or cells,
which have little communication with each other, and one such com-
partment being drained by pumping, others at a distance are not
necessarily affected. When part of a rock of this kind is covered
with gravel little difference might be anticipated ; but if the surface-
gravel covers up and conceals boulder clay of a stiff and tenacious
character and this is by no means uncommon in various parts of
England the compartments above alluded to will be very differently
filled with water in various parts of the same district.
Loose sand rock alternating with bands of marl and not in-
tersected by impermeable bands, such as forms the great mass of
the New red sandstone series in the middle and south of England,
ABSORBENT POWER OF ROCKS. 467
usually allows water to percolate freely to its base, tlie marl beds only
forming local interruptions, and retaining the water at the surface
only so long as it is running towards some natural vent. Harder
sands and sandstones, such as the millstone grit, form an almost im-
passable barrier for water, and conduct it to some other more perme-
able rock.
1051. Clays when of considerable thickness and extent do not
allow water to pass downwards into the earth, and often by their level
and easily-smoothed surface retain large pools and sheets of water to
the great injury of the soil. When there is a natural fall to the sea,
however small, there is always a possibility of greatly improving the
condition of such land by drainage, while springs of water are neither
required, nor if required would they be easily found without sinking.
It may easily happen and the geological structure of the district
would show whether this is likely or not that the clay covers up per-
meable and very wet beds, which would rise to the surface in Artesian
wells.
1052. Calcareous or lime rocks differ very much in their contain-
ing power with reference to water, and much doubt has long existed
as to the true state of such rocks in particular cases. They may be
divided into two groups the one partaking more or less of a spongy
nature, and the other hard and semi-crystalline. The Oolites offer a
kind of intermediate condition. The first of these groups is illus-
trated by chalk, of which the soft upper beds are exceedingly porous
and absorbent of water, but through which, after all, water percolates
but slowly. The lower beds of chalk, though not so soft, are almost
always, when penetrated by sinkings, found to be exceedingly wet, and
a large part of the water yielded freely, though the replacement of
very large quantities rapidly removed seems to take place but slowly.
In addition to the ordinary sources of water in the mass of the rock,
there is no doubt of the existence of numerous fissures and crevices,
and frequent large cavities, in chalk and all other lime rocks, and
these are often filled with water at a very considerable pressure.
1053. As a rock which has for various reasons attracted great
attention, and been very differently described, it may be worth while
to consider in some detail the chalk of England, which presents a wide
range and is pretty uniformly exhibited under the same mineral type.
Chalk has a specific gravity from 240 to 2 -55, or thereabouts; and
by the assistance of his friend and colleague Dr. Miller, Professor
of Chemistry in King's College, the author is able to give a correct
idea of the condition of the rock in respect of absorbent power.
The experiments mentioned below were made in the King's Col-
lege laboratory on three specimens of chalk, one (No. 1) from the
upper chalk near Box Hill, another (No. 2) from the middle bed
near Tring, and the third (No. 3) from the lower beds, probably
468
PRACTICAL GEOLOGY.
chalk-marl, near the bottom of the chalk towards the extremity of
Tring Cutting. The chalk being cut into slabs weighing about a
quarter of a pound each, were weighed in their ordinary state after
being for some months exposed to the air then when absolutely
dry and lastly when saturated by immersion into water in vacuo.
The weight when absolutely dry being regarded in each case as 1000,
we have
No i.
No. a.
No. 3,
1002-73
1002-30
1010-15
1186-57
1160-00
1161-02
Pounds of water in a cube foot of wet chalk ....
Bulk of water in chalk, a cube foot being unity . .
24-987
4
20-628
33
21-349
34
From this it is evident that at least one-third of the bulk of fully saturated chalk
consists of water, so that at a rough estimate there are about 2 gallons of water in each
cube foot of wet chalk. It also results that some kinds of chalk (No. 3) contain one
per cent, of water (by weight) even when apparently dry, while the upper chalk
scarcely contains more than from 2 to 3 parts in 1000 under those circumstances.
1 054. The following table showing the weight and volume of water contained in
several other well-known rocks when saturated, will be found useful. The saturation
is not under an exhausted receiver.*
ABSOEBENT POWER OF VARIOUS ROCKS.
Name of stone.
Locality.
Quality of stone .
Weight per
cube foot.
Ibs. oz.
Grains
of water
absorb-
ed in
each
cubic
inch.
Bulk of
water
absorb-
ed (2 in.
cubes
= 1).
Craigleith
Barley Dale . .
Mansfield red..
Do. white
Ancaster ....
145 14
148 3
148 10
149 9
139 4
136 12
123
128 5
135 8
151 11
133 10.
137 3
153 7
20-4
18-5
26-3
23-5
42-0
36-0
42-8
38-2
34-4
20-1
54-6
56-0
7-2
0-080
0-072
0-104
0-092
0-166
0-141
0-169
0-151
0-135
0-079
0-215
0-221
0-068
Derbyshire
Do
Nottinghamshire ..
Do
Do
Do
Lincolnshire ....
Northamptonshire
Wiltshire
Rutlandshire ....
Dorsetshire
Oolitic limestone
Do
Bath (Box) ...
Ketton
Do
Do
Portland
Do
Derbyshire
Magnesian limest.
Do.
Brodsworth . . .
Park Nook ...
Chilmark ....
Do
Wiltshire
Do
Siliceous limestone
1055. With regard to the fact that in limestones, and such like
rocks, there do exist great natural caverns, and that even in clayey
beds there are alternating bands of sand and gravel capable of receiv-
ing a considerable quantity of water, communicating with the surface
and sometimes passing down to immense depths, there can be no
Report of Commissioners on building stones for the Houses of Parliament.
SUBTERRANEAN COMMUNICATION OF WATER. 469
doubt whatever ; and it is equally certain that in some of them, at
any rate, the sheets of water are of very considerable extent. This
is known not only by the examination of such rocks of the kind as
are exposed at the surface, and by the appearances they there pre-
sent, but also from the occasional cavities discovered in boring for
Artesian wells, and also in sinking deep shafts in mining districts.
1056. As being perhaps one of the most interesting of these, and
proving that springs obtained from great depths are sometimes de-
pendent on atmospheric supplies and obtained by means of the pecu-
liar geological structure of the country, we may mention the case of
a fountain at Nismes, in the south of France, the supply from which,
even in times of great drought, amounts to 145 gallons of water per
minute ; but it is found that, when it rains heavily at a distance of
about six or seven miles from the fountain, in a north-westerly direc-
tion, an increase takes place suddenly in the supply, so that it then
sometimes pours forth as much as 1000 gallons per minute, the
temperature of the water supplied undergoing no change. It is
clear in this case that the spring must be fed from a distance, and by
means of long channels, which allow the water to flow rapidly through
them. The rapidity of communication also is so great, that these
channels must in all probability be open.
1057. As other instances may be quoted, 1st., the rock of Torghal, in Nor-
way, which is pierced from end to end (more than 3,000 feet) by a rectilineal
opening 150 feet high. 2nd. The celebrated cavern of Adelsberg, in Carniola,
which receives the waters of a river, contains a large lake, and has been traced for
a distance of at least six miles, but is probably much more extensive. 3rd. The
fountain of Vaucluse, which issues from subterraneous rocks, and pours forth a
volume of upwards of 13,000 cubic feet per minute, even under ordinary circum-
stances, and this increases sometimes to 40,000 cubic feet. There is also proof that
many of these caverns and subterraneous rivers communicate with the surface, for fish,
and even seeds, are occasionally conveyed into them with the water.
1058. During some sinkings near Dieppe as many as seven great sheets of water
have been tapped ; and under the city of Tours there appears to be distinct evidence
of the existence of a subterraneous river, for on one occasion the fountain in the Place
de la Cathdrale (sunk to 335 feet), brought up portions of vegetable matter, among
which were branches of thorns an inch or two long, the stems, roots, and seeds of
marsh-plants, and different kinds of grain; and fresh- water and even land-shells were
also found mingled with these remains, which from their condition appeared to have
been several months under water.
1059. The actual source of fresh supplies of water to all rocks must
ultimately be the atmosphere, and the quantity received in each year
in a given district is thus calculable within certain limits, if we
know the area of drainage, the nature of the rock, its dip, strike,
and faults, and its absorbent powers, the depth of rock of the kind
observed, and the nature of the underlying bed. The overlying su-
perficial deposits must also be understood, as the presence of clay in
these will manifestly affect the result to a very considerable extent.
Lastly, we must know the mean annual rain-fall in the district, the
470 PRACTICAL GEOLOGY.
extent to which evaporation goes on, and the seasons of the year at
which rain chiefly falls.
The mean annual rain-fall in the vicinity of London and in the East of England is
generally estimated at 26 inches. On the west coast, and especially near hilly or
mountain districts, it is much greater, and in some particular spots is more than five
times that amount. The quantity of water absorbed will depend so much on the nature
of the rock, the season, and the condition of the land, if cultivated, that any calculation
must be exceedingly conjectural. It is not unlikely that as much as 12 inches, the
usual estimate, may be within the mark in the case of chalk, which, when very dry,
absorbs with extreme rapidity. In calculations made afterwards only half that quan-
tity has been assumed, and this there can hardly be a doubt must be greatly within
the true amount.
1060. A familiar but very important example of the quantity of
water present in a rock may be here given from the beds imme-
diately round London. These are well known to consist of clays
reposing, first, on beds of shingle, sand, and other material of loose
texture, and then on chalk, which extends to some distance both
north and south. Both clays and chalk are partly covered also
with gravel, some of which is open, and allows water to run freely
through it, while some contains much clay which would hold water
to any extent. The clay, called " London clay" and described in a
former chapter, is tough, and of course impermeable, and bore-holes
put down, or shafts sunk to any considerable depth in the bed, or
to its base, generally, but not always, yield much water, which rises
in the well sometimes above the surface, often to the surface, and
most frequently to some height without reaching the surface. When
water is lifted by subterranean pressure above the level of a water-
containing bed below' the surface, the wells are, as we have seen,
Artesian, and must in all cases involve the drainage of a district at
some distance from the overlying surface. The very fact of the
welling or springing up of water when a particular bed or reservoir
is reached, seems to require, as a matter of absolute necessity, that
there should be a bed lying above that which yields the water, and
which is in some measure impermeable, although no doubt a relative
impermeability is sufficient when the overlying beds are also wet.
1061. The cause of the water-supply obtained at the base of the London clay, is
the presence there of sands and shingles cropping out at the rim of the basin, gene-
rally at higher levels than the clay itself. These beds conduct water pretty freely,
and a large quantity is retained either on the surface of the chalk or on some bands
of plastic clay occurring amongst the sandy and shingly beds. The cause of the very
great irregularity of the supply from wells sunk into these lowest Tertiary deposits,
seems to be partly the irregular nature of the lower beds, partly the very uneven sur-
face of the chalk, and partly the fact that in some sinkings a reservoir is reached and
in others only a portion of a wet bed is intercepted.
The actual supply of water between the chalk and the true London clay may be
very roughly estimated as follows. There are nearly 300 miles of outcrop of the
plastic clay series, which may be considered to average about a mile in breadth, and
of this one half may be permeable. The supply from 150 square miles of country, at
six inches of rain absorbed per annum, would be about 12,000,000,000 of gallons
WATER-SUPPLY OF ROCKS NEAR LONDON. 471
annually, and the actual quantity present, estimating the total area of the per-
meable beds of plastic clay beneath the London clay at 2,000 square miles, the mean
thickness of the permeable beds at twenty feet, and the bulk of water at one-fourth
that of the sands, will be about 1,500,000,000,000 of gallons. It would, however,
require sinkings over the whole area to obtain any large proportion either of the
contents or the annual supply even if continuous pumping were resorted to, and in any
case there can be no doubt that the quantity rising above or near the surface from
Artesian wells merely sunk through the clay would be in time much diminished.
1062. To return, however, to the case in point. The actual range
of the chalk in England may be divided into two parts, the one ex-
tending northwards, between the gault and lower cretaceous beds in
Kent and Surrey and the continuation of the anticlinal of the
Weald to Devizes ; and the other reaching southwards from that line.
These two areas must be disconnected as far as drainage is con-
cerned, for they have opposite dips, and we must consider the whole
northern district by itself. Measuring from this line to the outcrop
of the gault in Berkshire, Buckinghamshire, Bedfordshire, and
Cambridgeshire, as far as the north coast of Norfolk, we have an
area which may be estimated, very roughly, at about 8000 square
miles, of which nearly one half is covered up by the beds of the
London clay. 2000 square miles more are covered by newer Ter-
tiary deposits, which may also be regarded as impermeable to water,
so that there may possibly remain 2000 square miles of chalk sur-
face exposed to the action of the rain. But we must once more
make a division of this area, for we find, on examination, that one
part dips towards the north and the rest towards the south-east, a
large intermediate portion being very little inclined. The north
downs of Kent and Surrey, and possibly a portion of the chalk near
Marlborough, have the former inclination, and the rest of the range
of the chalk hills the latter ; so that the great triangular hollow or
basin occupied by the London clay is a synclinal axis, receiving the
drainage of the chalk hills on both sides of the valley. If, therefore,
the chalk is found wet at moderate depths near the outcrop of the
beds of London clay, which is generally the case, and if also the chalk
really acts as a sponge, all sinkings into the chalk itself through the
London clay ought to yield water at once, in considerable and nearly
uniform quantity, which is decidedly contrary to experience. Either,
therefore, the chalk is not freely percolated by water, or there is some
local cause for the imperfect transmission of water under the London
basin. It seems probable that very deep sinkings into the chalk
under London will generally yield a large supply of water, although
at various depths and in different quantities.
1063. But if we regard the chalk as a stratified deposit, presenting
bands of somewhat different texture and different water-containing
power, broken into innumerable crevices, traversed by numerous
fissures and joints, and occasionally faulted, we shall probably obtain
472 PRACTICAL GEOLOGY.
a clue to the real cause of the irregularities of the water-supply in this
rock. On reaching any one of the less permeable bands, or any con-
siderable crevice at a depth from the surface, we may expect to find
a large body of water, while when any large unbroken mass, whether
more or less porous, is pierced, there is either no large supply at all,
or a supply very easily exhausted.
1064. Limiting the problem and its conditions yet further, we may
regard the chalk on the southern edge of the London basin as having
generally a northern dip, and yielding with some freedom a number of
springs, coming out along or near the northern exposure of the beds on
the right bank of the Thames. The whole exposed surface of chalk
between the sea-coast and London may be divided into four portions.
First, between the Downs and the river Stour ; second, between the
Stour and the Medway ; 3d, between the Medway and the Darent ;
and 4th, between the Darent and the natural opening between' Green-
wich and Godstone, nearly traversed by the line of the South-Eastern
Railway. Between the Stour and the Darent, a district throughout
which there is chalk at no great depth coming out often on the
banks of the river, there are about 180 square miles of chalk exposed,
and an area about as great is covered up with the London clay be-
tween the chalk and the right bank of the Thames. It may, there-
fore, very safely be asserted that there are in this area about 350
square miles of wet beds, either cropping out near the river, or capa-
ble of being readily tapped, while there are, also, not less than 150
square miles in addition between the Darent and the South-Eastern
Railway. Now calculating from the best known data, this area of
500 square miles will contain in each yard thick of a fully saturated
bed, as much as 14,000,000,000 cube feet of water, or in each yard thick
under ordinary conditions of full absorption, about 12,000,000,000 of
cube feet : in other words, there are about 1,800,000,000 gallons of
water in every yard thick of wet chalk for each mile of outcrop ; and
if natural springs be taken up or tapped at intervals, a certain pro-
portion of this might no doubt be obtained for general purposes. We
have taken one yard of thickness as a convenient quantity, readily
modified to any other thickness.
It might be supposed that a part at least of the water falling on the impermeable
beds, whether London clay or belonging to more modern deposits, would add to the
supply by draining from its surface. This may be the case to a small extent, especi-
ally where small streams come over such deposits, and are lost after passing over some
distance of chalk ; but it is not likely seriously to affect the question, since there must
be a good deal of evaporation from such surfaces in warm weather when much rain
falls, and the superficial coating of soil and gravel almost always allows the water to
enter partially, and prevents immediate drainage to a lower level.
1065. There is, however, a great difference between the supply
obtainable from springs on a line of outcrop, and that from deep
sinkings within a comparatively small area. In the chalk especially,
WATER-SUPPLY OF ROCKS NEAR LONDON. 473
this must be the case, for the percolation of the water through the mass
of the rock, if in any sense complete, must be, and certainly is, very
slow, a well of exhaustion as a well constantly kept pumped down
is called, affecting the immediate surface to a very marked extent,
but not producing much observable difference at a distance, even when
only a few hundred yards.
1066. At Sheerness, water is obtained in the lower part of the London clay at
about 300 feet, and then rises above the level of the ground. At Fulham, the Lon-
don clay does not appear to contain a supply, but sinkings of about seventy feet in
the underlying chalk have been attended with success. At Hammersmith, sinkings
to 360 feet, arid at Chiswick, in the gardens of the Horticultural Society, at 330 feet,
abundant supplies have been obtained : but in the Duke of Northumberland's grounds
above Chiswick, no water was obtained at the junction of the London clay and the
chalk, nor until the latter rock had been penetrated to a great depth. At 620 feet,
however, a reservoir was tapped which delivered the water not only at the surface, but
about four feet above it. Other notices of sinkings into the chalk are given hereafter.
1067. The whole quantity of water in the chalk of England must
be enormously great, but is hardly calculable. At the very lowest
conceivable estimate, considering the total area as 6000 square miles,
the mean thickness only 300 feet, and only one- third of this fully
saturated to the extent of one-fourth its volume, it would amount to
twenty-five millions of millions of gallons ; while the annual supply
from rain to the extent of six inches of water absorbed per annum over
an area of 2000 square miles, would amount to nearly 175,000,000,000,
or more than -j^- -th part of the whole quantity of water contained. If
the population of the chalk districts, including the whole area
covered by London clay and gravel, be taken at 4,000,000 of indi-
viduals, and fifty gallons per day be allowed for each, a very large
and sufficient quantity for all possible sanitary purposes, there will
thus be needed only about 72,000,000,000 gallons per annum for this
purpose, or not much more than a third of the estimated annual sup-
ply from rain, and only 3- th part of the quantity contained in the
rock. It is unnecessary to state that only a part of this is directly
available ; but there must be a very large proportion that could be
pumped out, although it may be a very different question as to how
far this mode of obtaining water on a large scale is economical, or
in other respects advisable.
In the above estimate the quantities throughout are reduced to the very lowest that
can be imagined, to show that the supply of water must be much greater than any
demand that can arise. In point of fact, the proportion of rain entering the rock is
more likely to be 12 inches than 6; the mean thickness of chalk might fairly have been
taken at 600 feet instead of 300 ; and the quantity of water contained, instead of being
taken at one-twelfth, may have been considered one-sixth of the bulk. Estimated in
this way, the quantity of water in the chalk would be 1 00,000,000,000,000 gallons, and
the annual supply 350,000,000,000. In addition to the quantity of rain, a large supply
of water must enter some parts of the chalk from mere absorption from the atmosphere.
1068. The quality of water is unquestionably affected by the rocks
through which it passes : although in this respect it is not always
474
PRACTICAL GEOLOGY.
safe to conclude what the result will be without actual investigation.
Thus water obtained from surface-deposits is almost sure to contain
in solution some of those organic substances which in cultivated land
must always abound, and which are always carried down to some
little distance by the descending supply of rain ; water from irony
rocks, whether sand or otherwise, being generally chalybeate, and that
from calcareous rocks holding carbonate and other salts of lime in
solution. But when we examine the analyses of different rocks, as
given in previous tables, there will be found also a number of other
ingredients, as salts of soda, potash, magnesia, and other substances,
and these will also be taken up, while the very action of water and
the decompositions otherwise going on, produce sulphuric acid and
thus again act upon the containing rock, or alter combinations already
in solution in the water. Thus it results, that in wells, however the
water is obtained, there will be a certain proportion of saline and other
ingredients, although the actual quantity may be less in amount and
different in character in the case of deep and shallow wells in the
same locality.
1 069. It appears from a paper by Professor Brande, in the Quarterly Journal of
the Chemical Society, vol. ii. p. 345, that a well was sunk 426 feet deep, into 202
feet of chalk to supply the Mint. This well was completed 1st of January, 1847.
The water rises to within 80 feet of the surface, and about 45,000 gallons per day
are obtained ; the level being then reduced by this amount of exhaustion to about
1 00 feet from the surface.
Before the water was obtained from the chalk it yielded 44 grains of dry saline
matter in the gallon of water. Since the well was finished the quantity is only 37'8
grains: SG at 55= 100070. The following table will show the contents of this
and two other deep wells into chalk :
Trafalgar
Square.
265 ft.
of chalk.
Mint.
202ft.
of chalk.
Camden
Town.
166 ft.
of chalk.
20'058
JO'53
ll'lO
18'049
8*63
17-60
0.74.0
13'14
1 3-00
1 3-fi71
Carbonate of lime
3*255
3-50
2'254
1-50
0-034
Phosphate of soda
0-291
Phosphoric acid
Trace
Silica
0'971
0*50
Trice
0'908
Trace
2*30
Trace
Total grains per imp. gallon . .
68-240
37-80
44-00
1070. Mr. Brande thinks chalk water generally more pure than that obtained
nearer the surface in wells in the London Basin, and he states that it contains a
smaller proportion of solid ingredients. He gives a list, showing the solid contents of
various waters from several localities and depths, of which the following is a selection,
ARTESIAN WELLS. 475
Gr. per imp. gal.
Artesian well at Crenelle 1 794 ft. 9-86
Thames at Teddington 1 7'40
Brentford 19*20
Westminster 24-40
Greenwich 27'90
New River 19'20
River Colne 21'30
River Lea 2370
Gr. per imp. gal.
Deep well, Royal Mint 426 ft. 37'80
Hampstead waterworks 450 ft. 40'
Apothecaries Hall 45'
Coding's brewery, Lambeth 50'
Combe and Delafield's brewery 56*80
Berkeley Square 60'
Netting Hill 60'
Trafalgar Square 510 ft. 68'24
Tilbury Fort 75'
A few shallow wells contain 105 to 115 grains among these are some from near
churchyards.
1071. Very important questions sometimes arise as to the true
extent of surface area which supplies the river drainage in certain
districts, and although this subject has already been considered on a
large scale, as to the area of river basins, it needs further elucidation.
Certain rocks, chiefly sandstones and grits, are at the same time hard
and unfractured by crevices, and, therefore, allow water to flow over
them without either loss by absorption or injury by the admixture
of impurities. These rocks are eminently impermeable and favor-
able for holding water in reservoirs, while others equally impermeable
as clays abound in mineral substances readily taken up. It
should also be remembered that a certain amount of exposure to air
is useful and almost essential to give water its valuable properties for
household purposes, the oxygen obtained by absorption in that way
being desirable. Thus river water is beyond doubt the best adapted
for all household and sanitary purposes, and next to river water must
be ranked pure spring water, which has been long exposed to air,
and kept in motion for a certain time while flowing in a confined
channel or thrown up in fountains. A comparatively small area may
sometimes supply a very large quantity of water when full advantage
is taken of local peculiarities, although under other circumstances
many times that area would not yield more than a few small streams.
1072. It is very necessary to pay attention in well-sinking to the
beds passed through ; as these, though by no means the -same in the
same district, yet resemble each other so far that a knowledge of the
facts will be always useful. We append as a fit conclusion to this
part of the subject a copy of the sinkings in two Artesian wells one
through the London clay into the chalk in the middle of London, and
476
PRACTICAL GEOLOGY.
the other through the whole series of Tertiary beds and the chalk
in Paris. Both may safely be called successful, and to nearly the
same extent ; the quantity obtained amounting in each to between
300 and 400 gallons per minute, although in the one case at Paris the
water rises to and is delivered at the surface, whereas in London it is
pumped from a considerable depth. The last 500 feet in the Paris
boring is only 6 inches in diameter diminishing from about 1 foot.
The wells in Trafalgar Square commenced the one at 6 feet, and the
other at 4 feet 6 inches, were diminished at 170 feet down, and at
300 feefc were only continued by small bores.
Sinkings in the Artesian Wells at Trafalgar Square and Grenelle.
TRAFALGAR SQUARE, LONDON.
Feet.
Made ground 15
Gravel, shifting gravel and sand 10
LOWER TERTIARY DEPOSITS.
LONDON CLAY 145 t
Thin layer of shells
CRENELLE, PARIS.
Feet.
Plastic clay 30 '
Gravel, &c 10
Green sand 35
220
CHALK
265
167
Gravel and sand 13
LOWER TERTIARY DEPOSITS
Cockle shells
Quartzoze sand with fine parti-
cles of iron pyrites.
Fine sand.
Argillaceous sand.
Mottled clay.
Sand and clay with calcareous
nodules.
CHALK SERIES.
White chalk with flints. A
White chalk with beds of car-
bonate of magnesia and small
flints.
Grey chalk with small particles
of silex.
Grey chalk compact and with-
out silex.
Green chalk and green particles
of silicate of iron.
Blue argillaceous chalk.
Blue argillaceous and sandy
chalk with particles of mica
and veins of green chalk. *
UPPER GREENSAND SERIES.
Clay with iron pyrites, no-
dules of phosphate of lime
and fossil debris (gault).
Green sand.
Clay and greenish sand with
quartz grains.
Argillaceous sand.
Green and white sand.
WATER.
1454
J60
Total feet 510
Total feet 1794
BUILDING MATERIAL. 477
4. On Earthy Minerals used in Construction.
1073. The department of Practical Geology on which we are now
entering has already been the subject of some notice in previous
chapters where the composition and structure of various kinds of
rocks have been described. Thus the different kinds of clay used in
pottery and other similar purposes, and in brick-making the slates
the various limestones, magnesian limestones, and sandstones so
common as building materials, and the marbles, porphyries and other
ornamental stones ; all belong to this, and have each in turn been
described in some detail.
1074. Clays vary much in value and are required for very different
purposes, so that we have brick-clays, fire-clays, pipe-clay, porcelain-
clay and Fuller's-earth, and amongst metamorphic rocks various kinds
of slate. Analyses of these will be found in TABLE IV., p. 260, and
their properties and uses need not be here enlarged on.
1075. Limestones have also been described, and the circumstances
of their mineral composition fully explained. The kind most usually
employed in important constructions in the South of England is
Portland, and in the midland and eastern counties the varieties from
Northamptonshire ; while the use of the magnesian limestone has
been chiefly limited to the north of Derbyshire and Nottinghamshire
and the south of Yorkshire, where such beds offer the cheapest and
best material. A method adopted by M. Brard to determine the re-
lative value of various stones as building material is especially adapted
to the case of Oolites and other calcareous rocks in the middle of
England. It cannot be applied with any certainty to other rocks.
1076. The object of this process is to discover in a short time the relative resist-
ance offered bj r different kinds of stone to the action of damp and frost, and therefore
to determine the durability of stones with reference to exposure. Its accuracy was
determined by a number of 'experiments made in different parts of France and Switzer-
land, and by different persons, and reports to this effect were published in the " An-
nales de Chimie" for 1828, vol. xxxviii.
The following is an abstract of the method recommended to be employed :
1 . Several specimens should be selected from the questionable parts of a block of
stone to be tried, taking, for instance, those which present differences of colour, grain,
or general appearance.
2. These fragments should be cut into two-inch cubes, with sharp edges, and each
marked carefully, so that the part of the block from which they came may be referred to.
3. There must next be prepared a saturated solution of Glauber's salts (sulphate
of soda), the solution being made with cold water, and a quantity of the salt left for
an hour or two at the bottom, after as much has been taken up as the water will at
first absorb. (It will be found that a quart of water absorbs more than a pound of this
salt at ordinary temperatures.) The saturated solution is then to be boiled, and the
cubes prepared are to be plunged into the vessel in which the solution is boiling
violently, care being taken that each one of the cubes is completely submerged. The
boiling is then to be kept up, and the stones retained in the boiling liquid for half-an-
hour exactly. If a longer period elapse, the effects produced exceed those of ordi-
nary atmospheric action and frost.
478 PRACTICAL GEOLOGY.
4. When the boiling is completed, each specimen is to be withdrawn successively,
and suspended from a string, taking care that it touches nothing else, and is com-
pletely isolated. Beneath each there is also to be placed a vessel full of a quantity of
the solution in which it has been boiled, care being taken that it contains no frag-
ments of the stone detached during the boiling.
5. If the weather is not too wet or too cold, it will be found that the surface of the
stones, four and twenty hours after they have been suspended are covered with small
white, acicular crystals of salt. When these appear, the cubes are to be plunged into
the vessel below them, to get rid of the efflorescences ; and this is to be done re-
peatedly, as often as crystals of salts are thrown out during the experiment.
6. If the stone resist the decomposing action of damp and frost, the salt does not
force out any portions of the stone with it, and one finds neither grains, nor laminae,
nor other fragments of the stone in the vessel. If, on the other hand, the stone
yield to this action, small fragments will be perceived to separate themselves, detached
even from the first appearance of the salt, and the cube will soon lose its angles and
sharp edges. The portions thus detached are preserved at the bottom of the vessel
over which the cube is suspended, and their weight may be determined at the com-
pletion of the experiment.
7. The period of duration of the experiment, as recommended by M. Brard,
should be four days, and at the end of that time the particles detached should be
carefully weighed. The result is an index of the amount of disintegration suffered by
the stone, and may be compared with similar results from other stones.
1077. With respect to the decomposition of stones employed for
building purposes, it is greatly influenced, as well by the chemical
and mechanical composition of the stone itself and by the nature of
the aggregation of its component parts, as by the circumstances of
exposure. The Oolitic limestones will thus suffer unequal decom-
position, unless the little egg-shaped particles, and the cement with
which they are united, be equally coherent, and of the same chemi-
cal composition. The shelly limestones, being chiefly formed of
fragments of shells, which are usually crystalline and cemented by
a calcareous paste, are also unequal in their rate of decomposition,
because the crystalline parts offer the greatest resistance to the de-
composing effects of the atmosphere. These shelly limestones have
also, generally, a coarse laminated structure, parallel to the plane of
stratification, and, like sandstones formed in the same way, they de-
compose rapidly when used as flags, where their plane surfaces are
exposed ; but if their edges only are laid bare, they will last for a
very long and almost indefinite period.
1078. Sandstones, from the mode of their formation, are very fre-
quently laminated, and more especially when micaceous ; the plates
of mica being generally deposited in planes parallel to the beds.
Hence, if such sandstone, or shelly laminated limestone, be placed in
buildings with the planes of lamination in a vertical position, it will
decompose in flakes, more or less rapidly, according to the thickness
of the laminae ; whereas, if placed so that the planes of lamination
are horizontal, that is, as in its natural bed, the edges only being
exposed, the amount of decomposition will be comparatively imma-
terial. The sandstones being composed of quartzose or siliceous
BUILDING MATERIAL. 479
grains, comparatively indestructible, they are more or less durable
according to the nature of the cementing substance ; while, on the
other hand, the limestones and magnesian limestones are durable in
proportion rather to the extent in which they are crystalline ; those
which partake least of the crystalline character, suffering most from
exposure to atmospheric influences.
1079. The chemical action of the atmosphere produces a change
in the entire matter of the limestones, and in the cementing sub-
stance of the sandstones, according to the amount of surface exposed.
The mechanical action due to atmospheric causes, occasions either a
removal or a disruption of the exposed particles ; the former by
means of powerful winds and driving rains, and the latter by the con-
gelation of water forced into, or absorbed by, the external portions of
the stone. These effects are reciprocal, chemical action rendering the
stone liable to be more easily affected by mechanical action, which
latter, by constantly presenting new surfaces, accelerates the disinte-
grating effects of the former.
1080. On the whole, it would appear that, where there are no local
reasons to the contrary, preference should be given to limestones over
sandstones for most public buildings intended to be handed down to
future ages ; and this on account of their more general uniformity of
tint, their comparatively homogeneous structure, and the facility and
economy of their conversion to building purposes. Amongst the
limestones, also, those which are most crystalline are to be preferred ;
and some of the magnesian limestones seem to offer the greatest
advantages of durability, uniformity of structure, beauty of appear-
ance, and facility of conversion ; but it should be clearly understood,
that many other limestones, and many sandstones, also form admir-
able building stones ; and these are so distributed through the coun-
try, that there is now no excuse for those architects and engineers
who neglect to examine carefully into the relative durability and ex-
cellence of the stone employed in any edifice about to be constructed.
1081. It might also be shown, that if more attention had been
paid to the qualities of stone, the frequent decay observable in many
buildings, erected even within a few years, might have been avoided
at comparatively small cost, and we should find fewer of our public
edifices losing all traces of the finer work of their original structure.
So long, however, as the opinion and judgment of the mason is al-
lowed to decide on the stone to be used, so long will this result take
place, for " the mason almost always judges by the freedom with which
a stone works, no doubt an important element in the cost of a build-
ing, but certainly one which should not be permitted to weigh heavier
in the scale than durability."*
* De la Beche's Report, p. 486.
480 PRACTICAL GEOLOGY.
CHAPTER XIX.
ON MINING OPERATIONS AND THEIR REFERENCE TO GEOLOGICAL
STRUCTURE.
1082. By mining, we understand all those operations by which
mineral substances are obtained from beneath the earth's surface. It
is chiefly in this way, by position, that mines are distinguished from
quarries or open workings, and when any valuable mineral appears
at the surface, forming the outcrop of a bed or vein, it is usually fol-
lowed either by vertical shafts or horizontal galleries entered from a
hill-side, so that all important workings must have reference to
materials out of the immediate range of observation whose posi-
tion, probable condition, and extension, must be calculated from a
general or local knowledge of strictly geological phenomena. An
acquaintance with those facts of Geology recapitulated at the begin-
ning of the last chapter, is, therefore, of most essential and vital
importance, as without it all mining operations must be mere
speculations of the wildest kind. All practical miners are, indeed,
of necessity geologists to some extent, but though acquainted with
some facts, they are often apt to think slightly of general principles,
without which practical knowledge is mere empiricism.
1083. Mining operations are of two very distinct kinds : the me-
thods employed having reference to the way in which the required
mineral exists in the earth. Thus coal, salt, many ores of iron, and
some of other metals, appear in regular layers, interstratified with
and forming part of, the ,$eries of deposits which together make up
the earth's crust at partidS^r spots, while the usual ores of copper,
lead, &c., occur in crevices formed in rocks after they have been de-
posited, and often since their subsequent metamorphosis. The at-
tempt to obtain a portion or the whole t5f a deposited bed out of the
midst of a number with which it has always hitherto been in contact,
will be at once seen to involve difficulties altogether distinct from
those incurred in clearing out the contents of a crevice or fissure,
the walls of which ceased to be in contact before the material to be
extracted was placed in its existing position.
In the present chapter we shall endeavour to place before the
student the scientific principles of mining, both with respect to stra-
tified minerals and those contained in lodes or veins traversing various
rocks. All mere working details will be omitted, and all statistical
facts, however important, must also be neglected as incompatible
with the object in view. The principal substances obtained by
mining may be described as coal, clay, ironstone, and salt, regularly
MINING FOR COAL. 481
bedded, and various metalliferous ores in mineral veins : each of
these in turn will require some notice.
1. Mining for Coal.
1084. The principal localities in which coal is found, and the cir-
cumstances of the deposit in each case, have been already mentioned,
and the nature of the various kinds of coal and their uses have also
been the subject of description.
There are two exceedingly important matters to be considered and
understood before proceeding to describe the method of working in
coal-mines, and these matters themselves are both eminently practical,
both strictly dependent on that class of phenomena studied by the
Geologist, and both, therefore, proper to be mentioned in this place, as
connected with the Geology of practical mining. One of these is the
frequent repetition or loss of the coal strata by faults and dislocations,
and the other is the fact that those beds containing valuable fuel
capable of being extracted and employed for economical purposes,
are very rarely found except in one formation, and are even confined,
for the most part, to a certain part of that formation, so far as prac-
tical mining is concerned ; this being the case, not only in our own
country, but wherever extensive deposits of coal have hitherto been
found in Europe.
1085. The latter fact is one, the knowledge of which is obtained
by experience only, and as to a certain extent it partakes of the inde-
terminate nature of all negative propositions, it may be considered
as not yet fully proved. But the evidence, if not complete, is at
least exceedingly strong ; and the degree of probability that coal,
as a valuable mineral, is confined to the upper part of the Palaeozoic
series of deposits, is so great, as to be a safe guide in all the specula-
tions of prudent men. It is not that other groups of strata have
always been formed at a distance from land richly clothed with vege-
tation ; for, on the contrary, some (as the Wealden formations) are
entirely of fresh-water origin, while parts of the carboniferous system
seem almost exclusively marine ; and others (as the beds of the Lower
oolites) are associated with sandstone and shales loaded with vege-
table remains. Other accumulations of ancient vegetable matter are
found elsewhere, and indications appear in several of them of sand-
stones and shales, very similar to those associated with the coal ; but
the coal itself is always absent, or worthless, and a search for it in
any bed of the Secondary or Tertiary period, seems sure to result in
disappointment and failure. The Geologist can only lay this fact
before the practical miner as the result of observation, but it is of
great importance, and it is a case in which a sufficient acquaint-
ance with Geology may be the means of saving the expenditure of
1 1
482 PRACTICAL GEOLOGY.
large sums of money, under circumstances where there was not from
the first any reasonable prospect of success.
Numberless instances might be quoted of vain attempts that
have been made to obtain coal in other rocks than those of the Newer
Palaeozoic period in Europe, and each experiment in succession has
only served to strengthen the conviction that must exist in the mind
of every observant Geologist, that few exceptions are likely to occur to
the general rule in this matter. We have already given an account
of one remarkable and interesting exception in America.
1086. The other fact to be considered by the practical miner, is
that of the singularly frequent disturbances that have affected the
beds of coal and the strata associated with them, and the remarkable
complication of the faults that characterise many coal-fields. It
must not be supposed that the effect of these disturbances is either
uniformly advantageous, or always disadvantageous to the immediate
interests of the miner ; but there cannot be the slightest doubt that
we are indebted to such disturbances for frequent repetitions of the
same bed of coal at the surface, when without them it would be so far
covered up by newer deposits as to be utterly unattainable. If occa-
sionally the miner, in prosecuting his labours, or the mine-owner in
following what he considers a valuable seam of coal, is suddenly
stopped by coming in contact with a fault, and finds the coal shifted
several yards above or below, or even completely lost, he must not
forget that it is perhaps owing to these very shifts that the outcrop
has taken place at all in his neighbourhood, and that the coal is
workable in the district in which he is interested.
1087. But there is another important advantage derived from the
existence of these numerous faults in coal strata, namely, that they
intersect large fields of coal in all directions, and by the clayey con-
tents which fill up the cracks accompanying faults, become coffer-
dams, which prevent the body of water accumulated in one part of
the field from flowing into any opening which might be made in it
from another. This separation of the coal-field into small areas, is
also important in case of fire, for in this way the combustion is pre-
vented from spreading widely, and destroying, as it would otherwise
do, the whole of the seam ignited.
1088. An instance of the advantage resulting from the presence of a great line
of fault, occurred in the year 1825, at Gosforth, near Newcastle, where a shaft was
dug on the wet side of the great ninety-fathom dyke, which there intercepts the coal-
field. The workings were immediately inundated with water, and it was found
necessary to abandon them. Another shaft, however, was sunk on the other side of
the dyke, only a few yards from the former, and in this they descended nearly two
hundred fathoms without any impediment from the water.*
1089. The chance of fire is not so hypothetical an accident as might, perhaps, be
thought. Many instances are on record of fires having occurred, sometimes spon-
* Buckland's Bridgewater Treatise, vol. i. p. 544, note.
OUTCROP OF COAL. 483
taneously, from the decomposition of iron pyrites in contact with moisture, sometimes
from lightning, and sometimes wilfully, in consequence of quarrels between the
workmen and the coal-owners. When coal-beds have once been ignited they have
been known to burn on slowly for many years, and within the last twenty years there
has been more than one instance of extensive subterraneous fires, which have destroyed
many acres of coal.
1090. The stratified condition of the coal, and the high proba-
bility of discovering the seam or bed in every part of a district simi-
larly circumstanced, would render the working for coal almost a
mechanical labour, not requiring any special directions or any pre-
vious knowledge, were it not for the extreme abundance of faults,
and the great influence they have upon the productiveness of a coal-
field. But such previous knowledge, united with great experience,
is exceedingly necessary, and requires to be founded on a familiar
acquaintance with Geological phenomena.
1091. One of the most simple, though not the least important
applications of Geological knowledge in mining, may be exemplified
by considering the case of a coal-seam cropping out in a valley, since
there are no less than three very distinct cases that may occur, in
each of which the method to be adopted in working the coal must be
contrived with reference to the Geological position of the bed, and
not only to the fact of the coal cropping out. The first of these is
when the dip of the beds is less than the angle at which the valley
slopes, both being in the same direction, in which case a shaft sunk
anywhere on the rise of the hill will reach the coal, the seam of
which may be worked safely and with little difficulty, the newer beds
being always the highest in position. Elsewhere, however, where
the dip of the bed is greater than the slope of the valley, and the
direction is still the same, no useful result would be attained by sink-
ing on the rise, above the spot where the coal has once been seen, the
older beds coming out on the rise of the hill. Both in this case and
the former the outcrop of the coal may occur at about the same height
on the rise of the hill, the alteration of the dip of the strata being the
only point of difference apparent.
1092. The third case in which it is important to understand the
Geological position of the coal strata occurs when the slope of the
valley is in a different and nearly contrary direction to the dip of the
beds. In this case the newest and not the oldest beds will necessarily
appear the highest in position on the hill-side, and the coal may safely
be looked for at a certain calculable distance below the surface.
1093. Having offered these preliminary observations, as to the cir-
cumstances of the occurrence of coal, let us next proceed to consider
in what way, and under what conditions, the coal can be most con-
veniently extracted from the bowels of the earth ; and as these condi-
tions depend partly upon the nature of the coal itself, partly on the
thickness of the beds, and partly on their depth below the surface at
484 PRACTICAL GEOLOGY.
the place of working, and on the dip of the strata, it will be necessary
to distinguish between the North of England coal-field, where the
beds are of moderate thickness, exceedingly bituminous, and worked
at great depths, and the carboniferous deposits in Yorkshire, Stafford-
shire, Warwickshire, and Wales, where they are either enormously
thick, contain less gas, or can be conveniently obtained from depths
much less considerable. The Newcastle coal being that chiefly made
use of in England as a fuel, it will be convenient to bring it first under
consideration.
1094. When by the various methods already described, or by pre-
vious knowledge of the district, the presence of coal is ascertained,
the first operation to be undertaken before opening a coal-mine is
usually that of boring to discover the most advantageous spot for
sinking a shaft, and extracting the coal. This is often necessary,
owing to the complexity of various systems of faults, and the impos-
sibility of otherwise determining with certainty the prospects of
sinking.
1095. The operation of boring is generally effected with a kind of
chisel, which being attached to an iron rod by means of a screw, and
worked by a little temporary machinery erected on the surface,
makes its way by alternate chopping and scooping, the accumulation
of rubbish being taken out from time to time by an auger, as the
chisel becomes clogged. Successive lengths of rod are screwed on as
the work advances, and the nature of the strata gone through is
determined with considerable facility and certainty by examining
the fragments brought up by the auger.
1096. When in this way, or from previous knowledge of the dis-
trict, it is decided where a shaft shall be sunk, this important work
has next to be commenced.
The shafts in the North of England are usually cylindrical or ellip-
tical, and the smallest diameter is about ten feet. The smaller
shafts are generally divided throughout into two compartments by
an air-tight wall of separation (a brattice), but the larger ones, which
have a diameter of as much as fifteen feet, are sometimes divided into
three parts. One of the compartments is in this case made use of for
drawing the coal to the surface, another for the drainage of the mine,
and a third for ventilation, conveying to the surface the air that has
passed through the workings.
1097. Under the most favourable circumstances, the sinking a
shaft is a work of considerable time and expense, for it is necessary
to line a great part of the interior with bricks to prevent the loose and
incoherent strata from falling, or being washed in ; but it rarely
happens that any depth of shaft can be sunk without meeting with
springs of water, which sometimes empty themselves into the work-
ings to an extent which it would at first appear hopeless to contend
SINKING SHAFTS. 485
against. In such cases there is no safety to be obtained without
lining, with a strong framework, that part of the shaft which passes
through the loose permeable sands. This lining of the shaft is called
tubbing, and many pits around Newcastle and elsewhere (where ex-
treme durability is required, and no expense is spared to obtain this
object) were formerly lined throughout with three-inch boards
nailed to a circular wooden framework, called a crib, which was
firmly attached to the sides of the pit at convenient distances. But
this method, although it has been known to keep out a pressure of
water equal to lOOlbs. on the square inch, is not considered so safe
as the metal tubbing now adopted in all difficult works. In some
recent shafts as much as forty fathoms of a pit have been in this way
completely lined with a strong cast-iron casing.
1098. The depth of the shaft must, of course, vary indefinitely ;
but in the Newcastle coal-field it is rarely less than twenty-five
fathoms, or 150 feet. The most common depth is, however, much
greater than this, pits being sometimes sunk to nearly 300 fathoms
(1800 feet,) and an expense of upwards of 50,OOOZ. being often in-
curred before the seam of coal has been reached which it is intended
to work.
] 099. The most remarkable and enterprising work of this kind on record, is a sink-
ing at Monk- "\Vearmouth colliery, near Sunderland, commenced in 1826, through the
capping of magnesian limestone. The lower beds of the magnesian limestone and the
lower new red sandstone here overlap the coal-measures, and at the place of sinking
their thickness was known to be upwards of 300 feet. At a depth of 330 feet ac-
cordingly the coal strata were reached, but, at the same time, a spring was tapped,
which poured water into the workings at the rate of 3,000 gallons per minute. This
fearful influx was kept under by a steam-engine of 200 horse power, and the work
was made secure by a strong metal tubbing, and carried on successfully, though not
without considerable difficulty.
On entering the coal-measures, however, a new and unexpected check was experi-
enced. No calculation had been made for the extra thickness of the uppermost coal
strata in those parts where the upper beds had been protected from denudation. This
was found to require a much deeper sinking than had been expected ; and the diffi-
culties were increased when, at the depth of 1,000 feet, a fresh feeder, or spring of
water, was tapped. Additional expense and great loss of time was thus caused ; but
the proprietors persevered, and continued the sinking to the depth of 1578 feet, where
they were rewarded by reaching a seam of considerable thickness and value. This
was supposed to represent the Ben sham seam, and they therefore continued the work
to the " Hutton," the most valuable of all. The expense of this pit, including the
necessary preliminary operations, could not have been less than 100,000, and at
least ten years elapsed before any result was obtained. Another more successful and
less expensive sinking, also to an enormous depth and through a large quantity of
water, has been recently concluded in the neighbourhood.
1100. It is usual in the deeper workings to have but few shafts,
owing to the great expense of sinking ; and it is the opinion of some
of the most intelligent coal-viewers, that in this way, independent of
all economical considerations, the deep workings are more conve-
niently and perfectly drained and ventilated, arid that the general
486 PRACTICAL GEOLOGY.
work of the mine goes on better. It must be confessed that this
opinion seems hardly reasonable when the great extent of the under-
ground works to be thus ventilated is taken into consideration. In
some mines upwards of 70 miles of passages, more than 100 fathoms
below the surface of the earth, are only provided with one pit, not
above 12 or 14 feet in diameter, for ventilation, drawing coals, pump-
ing water, and every operation necessary between the surface and the
works.
1101. It is rarely necessary in the coal-fields in the middle or west of
England, or in Wales, to sink so deep for the coal, or undertake such
costly works in order to obtain it ; but the method of sinking is, of
course, the same. In many places, however, it is found more con-
venient to sink a number of pits of smaller size than one large one,
and in this way to avoid the extensive underground operations re-
quired in the north to effect the ventilation of such mines as have
only a single shaft. The thickness of the coal in Staffordshire also
renders it expedient to resort to methods of working on a principle
somewhat different to that followed in the Newcastle coal-field, and
these methods will require to be spoken of separately.
1102. The shaft being sunk, it is usual to drive two galleries, or
levels, the one along a horizontal line on the strike of the coal-seam,
and the other at right angles to this on the rise of the bed. The
former is called the drift, or water-course, and has important refer-
ence to the drainage of the mine, and the latter is the winning head-
way, or main thoroughfare, through which the coal is conveyed to
the shaft when extracted from the galleries afterwards cut. These
two principal arid preliminary cuttings are usually of considerable
dimensions (from nine to twelve feet wide, and six feet high), admit-
ting of the passage of loaded waggons and horses, and they are almost
always provided with a tram or pair of rails. In the shallower mines,
and where a second shaft is sunk, the new shaft opens at the extremity
of the winning headway, and ventilation is at once established.
1103. The method of working must be decided on, not only with
reference to the chance of explosion from certain gases afterwards to
be described, but also after all possible information has been obtained,
and calculation made as to the sustaining power of the roof and floor,
the strata above and below which the coal is deposited. For it
must always be remembered that although so long as the coal re-
mains in its place there is no extraordinary pressure, every part being
equally and proportionably sustained ; yet so soon as the excavation
has commenced, and empty spaces are left, the roof, if sufficiently
coherent, causes the whole superincumbent weight to press on those
portions of coal that may be left in the mine, which in that case act
as pillars, and will inevitably be crushed if their dimensions and
hardness are inadequate.
BOARD AND PILLAR WORKING. 487
1104. If however the roof consist of hard sandstone and the floor
of soft clay, the pressure downwards will tend to displace and force
up the floor, and fill up the spaces left by removing part of the coal.
If, on the other hand, the roof be soft, it will sink in, and if both
roof and floor are moderately hard and tough, they may, after a
time, meet each other mid-way. The surface sinking in, in con-
sequence of this, the result called a creep is sometimes produced.
1 105. Having acquired a knowledge of the nature of the coal itself,
and of its floor and roof, it becomes a most important problem to be
solved by the coal- viewer, how far he can safely proceed in taking
away the coal, and in what way the maximum of produce can be
obtained, with the minimum of danger and loss.
In the Newcastle coal-field, where the coal is full of gas, where
the best seams are worked at very great depths below the surface,
and where the strata associated with the coal are often soft and
incoherent, it is usual to extract the coal by cutting a number of
galleries parallel with each other, and intersected by others at right-
angles thus isolating between four such galleries a pillar of coal
whose dimensions vary according to circumstances.
1106. In the description already given of the first operations of
mining after the shaft is sunk, it has been mentioned that two levels,
the drift and winning headway, are first completed, and after this
other galleries are sometimes driven parallel to the winning head-
way. These galleries are of different dimensions, the larger ones,
which are nine or ten feet wide, are called boards, and they are in-
tersected by other galleries at right-angles to them whose dimensions
are not quite so large, and which are called narrows. The pillars of
coal left between these galleries, in Newcastle workings, must be
from eight to nine yards thick, and until the close of the last
century this method was the only one employed in deep workings,
at least sixty per cent, of the coal being left in the mine.
1107. About fifty years ago, however, an attempt was made, for
the first time, to remove a part of the pillars, and a method was
devised by which fifty-four per cent, of the coal was obtained, and
afterwards, this method succeeding, alternate rows of pillars were
abstracted, and sometimes even half the intermediate ones. Lastly,
Mr. Buddie invented the method called panel-work, by which nearly
the whole of the coal may be obtained with safety.
This method consists in dividing the mine into districts or
panels, separated from one another by walls of coal forty or fifty
yards thick, and extracting the coal from each of such panels in
succession, usually beginning with the one most distant from the
shaft, and completely shutting off all communication with the rest of
the mine as soon as any panel is worked out. Large pillars are at
first left between the boards (which are four yards wide), and the
488 PRACTICAL GEOLOGY.
transverse galleries, (two yards wide), and the dimensions of the
pillars are about twelve yards by twenty-four. As soon as the
galleries are finished, and the work of removing the pillars com-
mences, the roof is at first supported by stout props of Scotch fir, and
when these are also taken away, the roof falls in ; but the whole of
the workings are kept under perfect control so far as ventilation is
concerned, and any part can at very short notice be shut off from
the current of air running through the whole mine, should such an
arrangement be required.
The great advantage of Mr. Buddie's plan is, that while a
large proportion of the whole bed of coal may be by its means ex-
tracted, the ventilation may be generally well preserved, and the
risk of danger from accumulations of gas in old workings almost
entirely avoided, because these old workings can be completely cut
off from the mine as soon as they become in a dangerous state. The
technical name for such workings is pillar and stall, or board and
pillar working.
1108. Such being the method of working in mines where there is
clanger to be anticipated from the presence of inflammable or explosive
gases, let us next shortly consider the nature of the different and
simpler contrivances followed in those districts where the coal is not
fi.ery, and where the associated beds are sufficiently hard and cohe-
rent to support themselves without fear of accident. These are
called long-wall methods.
In the Yorkshire collieries there is something of the regu-
larity observable in the mines of the Newcastle coal-field, but a
greater proportion of the coal is worked out at first, and only a wall
of coal is left. At least two pits or shafts are sunk, communicating
with each other by a gallery called the drift. From the lower, or
engine pit, a gallery is cut on the strike, and likewise another from
the working pit, and these are called respectively the water-gate and
the horse-gate. From the bottom of the working pit a main gallery
is also driven on the rise of the coal, and this, which corresponds to
the winning headway of the north of England, is here called the
main board-gate. Other galleries, parallel to this, are also cut, and
the coal is then worked from the intermediate pillars, leaving only a
narrow wall, and allowing the roof to fall in after those temporary
props are removed which supported it while the works were
advancing.
1 109. In Staffordshire again, where the seam of coal is of extreme
thickness, and consists in fact of several beds united, the method is
somewhat different, as there only a few irregular pillars are left \ but
there is still a wall of coal, although little regard is paid to those
conditions which are justly considered as of the most vital importance
in the mines of the Newcastle coal-field.
VENTILATION OF COAL-MOES. 489
1110. The system of ventilation must, of course, be nearly the
same in its general plan, whatever be the nature of the mine to which
it is adapted ; and therefore, in describing the most complicated and
perfect arrangements of this kind, as carried on in the fiery seams of
Newcastle and its neighbourhood, it will hardly be necessary to men-
tion the smaller degree of the same care and attention paid in the
less dangerous workings of other districts.
1111. Perhaps it is advisable, before proceeding to give an account of the ventila-
tion of coal-mines, that the reader should be made acquainted with some technical
terms that will be used in the description.
A brattice is a wall of separation. Brattices are of two kinds ; either permanent,
and separating a shaft into two or more divisions, in which case it is a strong parapet
wall, sometimes as much as three feet thick; or temporary, and consisting only of a
frame-work of three-inch deal, readily moved to any part of the underground workings.
A piece of tarpauling will often be found serving the purpose of a temporary brattice.
Stoppings are walls made of brick, stone, or timber, and their object is to prevent
the current of air from passing in a given direction. They are of considerable thick-
ness, and in many cases consist of two stout brick walls, with many yards of rubbish
between them.
Trap-doors are moveable substitutes for stoppings in the great thoroughfares of the
workings. They are of several kinds ; as main-doors, which are in sets of two or
three, and always fixed in the strongest manner, and provided with boys to open them
upon a signal, and take care that two of the same set are never open at the same
time. Man-doors are of small size and communicate with the dangerous parts
of a mine. Sheth-doors are those which purposely allow a certain degree of
leakage ; and sham-doors are a kind of trellis- work, only intended to check the current
of air. Su'ing-doors are sometimes placed between two main doors.
The air-course is a general name for the air traversing workings where ventilation
is going on. The fresh air descending into the mine is called the " zw-fae,"and that
which ascends, after having passed through the workings, is the " return"
A crossing is where a current of air crosses another current by means of an arch or
small tunnel.
That part of a mine which is not included in the principal ventilation is called the
waste.
1112. There are various modes of inducing the current of air by
which the ventilation of mines is to be effected, but the most com-
mon is by rarefaction, a powerful furnace being placed at the bottom
of the upcast pit. In some cases, indeed, it is not considered safe to
resort to such an expedient for the whole of the air, in consequence
of the quantity of gas poured out in the workings ; and when, owing
to this or any other reason, the furnace cannot be used, a hot cylinder
has been substituted, or a current of air produced by throwing a
column of water into the downcast shaft, or by pumping out the air
by means of an air-pump or steam-jet from the upcast ; but all these
are partial and imperfect contrivances, and have many great disad-
vantages. The simple furnace has been proved by experience to be
the most convenient method of producing the required current ; and
the portion of the air in a dangerous state may be conveyed into the
upper part of the shaft by a contrivance called the dumb furnace.
1113. The effect of a large fire at the bottom either of a shaft, or
490 PRACTICAL GEOLOGY.
of a division of the shaft, is to add considerably to the rarefaction of
the air as it passes out of the mine, and in this way to produce a rapid
ascending column of hot air, whose place is immediately supplied by
a rush of cold air from the surface, and this cold air, passing down
the other pit, or another compartment of the shaft, and through the
workings, is gradually warmed, until at last it reaches the furnace,
and itself becomes the ascending column.
1 114. The quantity of air passing into a mine varies very considerably, according
to the magnitude of the workings, and the extent to which the down-current is distri-
buted into different divisions or panels of the mine. As an example sufficient to give a
clear idea of the principle of ventilation by splitting the air when underground, we may
mention the case of the Hetton Colliery, one of the most extensive in the county of
Durham, where experiments have lately been made which are recorded by Mr. N.
Wood, in his evidence before the House of Lords. (See Report of Lords' Committee
on Accidents in Coal Mines, 1849. Qu. 1816, et seq.) In this mine there are two
seams now worked and one that has been formerly worked two downcast shafts
and one upcast, the former about twelve feet and the latter fourteen feet diameter ;
and three furnaces at the bottom of the upcast, each about nine feet wide and about
four feet length of grate-bars. The depth of the upcast and one downcast, 150 fathoms,
and of the other downcast, 176 fathoms.
The quantity of air introduced into the mine by the action of these furnaces was
1 68,850 cubic feet per minute, at a cost of about eight tons of coal per day. The rate
of motion of the air was 1097 feet per minute.
This whole current is divided by splitting into sixteen currents of above 11,000
cubic feet per minute, having, on an average, a course of four miles and a quarter each.
The distance is, however, irregular, the greatest length of course being nine miles and
one-tenth. The effective velocity of the current in the actual workings of the mine is
much checked by the multiplication of passages, the friction and other causes, and is
thus reduced to from three to fiye feet per second ; the smaller quantity being about
the maximum rate attainable by the natural current in a small mine, where there will
generally be from one to three feet. It has been estimated that the minimum quantity
of fresh air required for the support of life in a mine is about fifteen or eighteen cubic
feet per minute for each man employed.
1115. The current of air once obtained, is conducted through
the passages of the mine by various contrivances, consisting of
permanent stoppings of brick and rubbish, temporary doors and brat-
tices, or partitions, and partial orifices or scalings. The arrangement
of these is a matter of detail, varying in each mine and often in dif-
ferent parts of the mine : it depends also considerably on the mode
of working adopted.
1116. Having said so much on the methods of ventilating coal-
mines, we may conclude with a few words descriptive of the process
actually followed by the miner in extracting the coal from its bed.
The working tools of the collier are few and simple, and consist
chiefly of diiferent forms of the pick, the most useful of which is a
kind of mattock, with both ends of the head pointed. Besides this,
chisels of various kinds, crowbars, hammers, and wedges, make up
almost the whole list.
1117. The coal is in almost all cases readily detached by blasting,
and is then easily broken up into cubical masses by taking advan-
EXPLOSIVE GAS IN COAL. 491
tage of the natural joints or vertical crocks which traverse it, and
which occur generally in sets parallel, and at right-angles to one an-
other. Besides these the coal is also characterised by what are called
partings, parallel to the stratification of the beds. The usual method
of getting the coal is by blasting, and this is effected by piercing the
lower part of the seam with a hole about an inch in diameter and a
yard deep, into which the charge is inserted in cartridges, and the
hole is afterwards plugged with coal-dust. When the blast has been
fired, the coal is broken up by the hewer, who is usually paid
according to the number of tubs, or corves, he is able to fill.
These corves are conveyed on tram-roads through the mine, and ulti-
mately lifted by machinery to the surface. The men employed in
actually getting the coal, are called hewers, the loaded waggons, or
corves, are conveyed along the tram by lads called putters, as far as
the principal galleries, or headways, and are there received into wag-
gons called rolleys, several of which being attached together, they are
drawn by a horse to the bottom of the shaft.
1118. Miners are generally lighted by candles, which they carry
with them and attach to the wall of coal near their work, by a frag-
ment of soft clay. Since however it happens that all bituminous
coal contains a certain proportion of inflammable gas, usually carbu-
retted hydrogen (or fire- damp}, which is given off on the exposure of
a fresh surface of the coal, and is often pent up in crevices and set
free by ordinary workings, or by an accidental arrival at a fault,
and since, too, this gas is explosive in certain states of mixture with
atmospheric air, a considerable risk is thus incurred which has too
often resulted in accidents, amongst the most frightful that can be
imagined. Attempts have been made at various times to remedy
the evil by the introduction of lights which should not explode the
gas ; and of all contrivances of this kind the lamp invented by Sir
Humphrey Davy, and thence called " the Davy-Lamp," is the most
generally adopted, and on the whole the most effectual.
1119. The composition of the inflammable gas exuded from coal and present in coal-
mines, is a matter too important to be passed over without notice. We append the
latest and most careful analysis of specimens of this gas, collected by Mr. J. Hutchin-
son, from Gateshead and Killing-worth colliery (Newcastle coal-field), the former
from the five-quarter, and the latter from the Bensham, seam. The analyses are by
Professor Graham/
Gateshead.
0-5802
Killingworth.
0-6406
94-2
82-5
5-5
16-5
1-3
1-0
100-0
100-0
* Mem. of Chem. Soc. of London, Vol. iii. p. 7-
492 PRACTICAL GEOLOGY.
1120. The proportion of carburetted hydrogen gas, or fire-damp, necessary to be
mixed with atmospheric air, in order to render it explosible, is about one- fourteenth
part. With this admixture there is danger, and the danger increases as more fire-
damp is added, until the mixture reaches its maximum of explosibility, at which time
the proportion varies from one-ninth to one-eighth. The risk of explosion is not so
great when there is a larger quantity of the noxious gas, and when as much as one-
fourth part of the mixture is composed of it, it will no longer explode, but begins
to be inflammable.
1121. The principles involved in the construction of the Davy-
lamp are simple, being first, that no mixture of the fire-damp with
common air, however dangerous, conveys an explosion through tubes,
the diameter of which is less than about one-eighth of an inch ; and,
secondly, that these explosive mixtures need a much stronger heat
for their explosion than mixtures of common inflammable gas, since
neither charcoal nor iron at a red heat will produce this effect,
which requires, indeed, that iron be raised to a white-heat. Pur-
suing this discovery, Sir H. Davy found that the length of the small
tubes, in which it was impossible to explode dangerous gases, was a
matter of indifference, and that a metallic gauze, in which this
length was merely the thickness of a fine wire, was quite sufficient
for the purpose.
1122. It will be evident, therefore, that by surrounding the light
of a lamp entirely by wire gauze whose meshes are sufficiently small,
any explosion that may take place within the lamp will not be com-
municated to the outside, and the lamp may be safely carried
where, otherwise, approach would be impossible. The size of the
mesh for this purpose is from one-fortieth to one-sixtieth of an
inch, and twenty-eight wires, or 784 apertures to the square-inch,
are found a defence perfectly sufficient. It should, however, be dis-
tinctly understood that even such a lamp ought not to be used
carelessly in any dangerous atmosphere j for, although perfectly
secure when at rest, it seems certain that a rapid motion such as
would be communicated by the swing of the arm during a hurried
transit through the mine, might produce, and possibly has produced,
an explosion. The main fault of the Davy-lamp, and indeed of all
the other safety-lamps, arises from the small quantity of light
diffused, and the consequent dislike acquired by the miners to its use.
No contrivance, however perfect, can by possibility exclude the
chance of accident, and the gross and almost inconceivable careless-
ness of men whose daily occupation leads them into the most immi-
nent danger cannot be overcome, and can with great difficulty be
understood by those not in the habit of constant communication
with them.
1123. The quantity of carburetted hydrogen gas poured out into
the workings of some mines is very considerable and constantly
varying. Some seams of coal are much more full of gas than others,
IRON MINES. 493
and in working these, which are technically called fiery seams, it is
not uncommon for a jet of inflammable air to issue out at every hole
made for the reception of the gunpowder previously to blasting. In
the celebrated Wallsend Colliery, in an attempt made to work the
Bensham seam (an attempt terminated by a fearful accident), Mr.
Buddie says, in evidence before a Committee of the House of Com-
mons/' 4 " 1 simply drilled a hole into the solid coal and stuck a tin
pipe into the aperture, surrounded it with clay and lighted it, and I
had immediately a gas light ; the quantity evolved from the coal
was such that in every one of those places I had nothing to do but to
set a candle and then could set a thousand fissures on fire ; the whole
face of the working was a gas pipe from every pore of the coal."
After a mine has been for some time opened, the gas drains off, at
least partially, and the danger from this cause diminishes.
1124. But besides the gas thus steadily and constantly forced into
the workings of a mine by a fiery seam of coal, there is always dan-
ger of sudden discharges as if from great reservoirs, rushing out
from some fissure or small opening in large quantity and with
considerable noise.
These jets are met with in mines perfectly ventilated, and they
occur sometimes from the roof, sometimes from the floor of the mine,
and still more frequently when small faults are reached in the course
of working. Several collieries in the North of England are remark-
able for constant discharges of this kind, which are collected and
conveyed by a tube the nearest way to the upcast shaft.
2. Iron Mines.
1125. The vast preponderance in the value of the iron above that
of every other metal obtained in England, and even above all of them
taken together, renders it necessary to devote some space to describe
the working of those ores from which the supply is chiefly derived.
The principal districts in the British Isles from which iron is
obtained are three, the South Welsh, the South Staffordshire, and
the West of Scotland.
The beds of ironstone being interstratified with the coal, and
the sandstones and shales of the coal-measures, they are usually
raised from the same pit as that by which the coal is extracted. The
thickness of the ore, however, being generally only a few inches, it
is worked in a manner somewhat different.
1 126. Near Bilston, in the South Staffordshire district, there are as
many as seven seams containing ironstone, all distinguished by tech-
nical names, but many of them not more than five or six inches in
thickness, and alternating with claystones not containing iron. Two
of the ironstone bands are thicker and more valuable than the rest,
* Parliamentary Report. Accidents in Mines, 1835; Minutes of Evidence, Qu. 20Q5.
494 PRACTICAL GEOLOGY.
and they, as well as all the others that are worked, lie beneath the
ten-yard seam of coal in the district. The seams are, if possible,
worked two together, the intermediate stuff being of no value, but
removed to form a gallery, and afterwards piled up to support the
roof when the ore has been obtained. The nature of the work is
sufficiently simple ; the miner usually lying on his right side, and
striking with the pick to remove the ore and the intermediate clay.
This method may seem a disagreeable one ; but the galleries are
cooler than the coal-mines at the same level, although they are also
wetter and dirtier. The ironstone is of a dull brown or yellowish
colour; it very often occurs in the shape of flattened spheroidal balls,
and is traversed by cracks and fissures which have become filled
with carbonate of lime. The centres of the spheroids often exhibit
an organic nucleus.
There is considerable danger in working these mines from the
occasional falling in of a portion of the roof, but they are usually
almost entirely free from noxious gases.
1127. The iron district of South Wales supplies a large propor-
tion of the whole amount of iron made in the British Islands. It is
identical with the great coal-field of that district, the ironstone bands
being always associated with the various beds which make up the
carboniferous series.
The bands of iron-stone there, as in Staffordshire, are usually not
more than a few inches thick, and the workings are, therefore, as
narrow and low as possible. They are often inclined at a consider-
able angle, and this position is taken advantage of by working in
levels which communicate with the lower part of the shaft by gal-
leries run on the dip of the vein.
1128. " The distribution of the ore among the limestone, which
in the Forest of Dean forms its matrix, is sometimes very remarkable.
It lies in ' churns', or ' pockets? as the miners term these deposits ;
and as the ore is cut away, natural pillars and arches of limestone
are left supporting the roof in a variety of grotesque forms and com-
binations. The contents of the churns vary both in quality and
quantity, producing a picturesque irregularity in the mine-works,
strongly contrasting with the even courses of the coal strata."* Ac-
cidents are said to happen very frequently in these mines, from the
miners neglecting to prop up the roof with timbers as they
proceed.
The iron works in Glamorganshire and Pembrokeshire are some-
times so near the surface as to be obtained without a shaft or
regular galleries. In other cases, they are worked from an adit level,
which comes out to day on the side of a hill.
1129. The iron district of Scotland contains a vein of ore called
* First Report of Commissioners on Mines. Appendix, pt. ii. p. 4.
SALT MINES. 495
the Hack land, much richer than those ordinarily met with in South
Wales or Staffordshire. This valuable stratum is extremely local,
not being known to exist in perfection beyond a space of from eight
to ten square miles ; but similar deposits of inferior quality are suffi-
ciently abundant. Black bands have been found also in various iron
districts.
Although the true black band of Scotland is confined in its dis-
tribution, there are no less than four principal and valuable seams
of ironstone in the Lanarkshire district, three of which are of very
superior quality. These measure from fourteen to eighteen inches
each in thickness, and when roasted yield from 60 to 70 per cent,
of iron, requiring not more than six cwt. of limestone as flux, instead
of from twenty to thirty cwt. (as the poorer and less fusible ores do)
to produce the ton of metal. Some account of the statistics of the
iron trade have been given in 945, and the composition of various
clay iron-stones in 456.
3. Salt Mines.
1130. The salt-mines of Cheshire form so legitimate a branch of
the great mining operations of our country, that they well deserve
notice among the applications of mining principles now under con-
sideration. These mines and the brine-pits of Worcestershire, not
only supply sufficient salt for the consumption of almost the whole
of England, but upwards of half a million of tons, for the most part
the produce of the neighbouring county of Cheshire, are annually
exported from the port of Liverpool.
The immense deposits of rock-salt from which this great supply
is obtained, are strictly confined in England to the marls of the
New red sandstone formation, and they are not universally dis-
tributed, being only met with in two or three counties skirting the
Principality of Wales. In Cheshire the salt occurs in large quanti-
ties in the condition of an impure muriate of soda, and associated
with a peculiar marl : it is sometimes massive, and sometimes exists
in large cubical crystals, and the beds containing it usually alter-
nate with considerable quantities of gypsum or sulphate of lime,
although this latter mineral is not worked to profit.
1131. The appearance of the rock-salt is by no means of that
brilliant character, nor has it the delicate transparency, and bright
reflecting surface, which the reader may perhaps suppose character-
istic of it. It is usually of a dull red tint, and associated with red and
palish green marls ; but it is still not without many features of great
interest, and when lighted up with numerous candles, the vast sub-
terranean halls that have been excavated present an appearance
richly repaying any trouble that may have been incurred in visiting
them.
496 PEACT1CAL GEOLOGY.
In Nantwich and the other places in Cheshire where the salt
is worked, the beds containing it are reached at a depth of from
fifty to 150 yards below the surface. The number of saliferous
beds in the district is five, the thinnest of them being only six
inches, but the thickest nearly forty feet thick, and a considerable
quantity of salt is also mixed with the marls associated with the
purer beds.
1132. The method of working the thick beds is not much unlike
that already described in speaking of the thick coal-seams of Staf-
fordshire and Shropshire. The roof, however, being more tough,
and not so liable to fall, and the noxious gases with the excep-
tion of carbonic acid gas totally absent, the works are more simple,
and are far more pleasant to visit. Large pillars of various dimen-
sions are left to support the roof at irregular intervals, but these
bear only a small ratio to the portion of the bed excavated, and
rather add to the picturesque effect in relieving the deep shadows
and giving the eye an object on which to rest. The intervening
portions are loosened from the rock by blasting, and it may be
readily understood that the effect of the explosions heard from time
to time, and re-echoing through the wide spaces, and from the dist-
ant w r alls of rock, give a grandeur and impressiveness to the scene
not often surpassed. The great charm, indeed, on the occasion of a
visit to these mines, even when they are illuminated by thousands of
lights, is chiefly owing to the gloomy and cavernous appearance, the
dim endless perspective, broken by the numerous pillars, and the
lights, half-disclosing and half-concealing the deep recesses whick
are formed and terminated by these monstrous and solid projec-
tions.
1133. The descent to the mines is by a shaft, used for the gene-
ral purposes of drainage, ventilation, and lifting the miners and the
produce of the mine. The shafts are of large size in the more im-
portant works, and the excavations very considerable, the part of the
bed excavated amounting in some cases to as much as several acres.
Over this great space the roof, which is twenty feet above the floor,
is supported by pillars, which are not less than fifteen feet thick.
The Wilton mine, one of the largest of them, is worked 330 feet
below the surface, and from it, and one or two adjacent mines, up-
wards of 60,000 tons of rock-salt are annually obtained, two-thirds
of which are immediately exported, and the rest is dissolved in water,
and afterwards reduced to a crystalline state by evaporating the
solution.
The mines, however, are not the only sources from which salt
is obtained, and it is only since the year 1670, when the beds
were discovered during an unsuccessful sinking for coal, that the
actual rock-salt, as a mineral, has been dug out from the mine. Be-
METALLIFEROUS VEINS. 497
fore that time, the chief supply was obtained from the brine-springs
of Droitwich, near Worcester.
1134. Among the most remarkable of the rock-salt mines in Eu-
rope, are those of Altemonte in Calabria, Halle in the Tyrol, Car-
dona in the Pyrenees, and Wieliczka in Poland. These are all interest-
ing, and each exhibits phenomena peculiar to itself, but I must not
detain the reader with an account of individual mines.
The deposit of salt in the valley of Cardona, in the Pyrenees,
is, however, too remarkable to be passed over. In this spot, two
thick masses of rock-salt, apparently united at their bases, make
their appearance on one of the slopes of the hill of Cardona. One
of the beds, or rather masses, has been worked, and measures about
13 yards by 250, but its depth has not been determined. It con-
sists of salt in a laminated condition, and with confused crystalli-
sation. That part which is exposed is composed of eight beds,
nearly horizontal, and having a total thickness of fifteen feet, but
the beds are separated from one another by red and variegated marls
and gypsum. The second mass, not worked, appears to be unstrati-
fied, but in other respects resembles the former, and this portion,
where it has been exposed to the action of the weather, is steeply
scarped, and bristles with needle-like points, so that its appearance
has been compared to that of a glacier.
4. Metalliferous veins, or lodes.
1135. The nature and many of the phenomena of mineral veins
have already been considered (see 629, et seq.), and we do not pro-
pose in this place to recur to that part of the subject. We shall
here only give a brief outline of mining operations so far as they
are in any way dependent on Geological structure.
With regard to that department of Practical Geology which we
are now considering, it must be confessed that at present the indi-
cations furnished of the existence of metalliferous ores by a conside-
ration of the general order of superposition and age of the rocks of a
district, are rather negative than positive, and scarcely do more than
enable the Geologist to assert, that in such or such a spot there is no
probability of the existence of productive veins. Still even this
amount of knowledge is useful, and a more minute acquaintance with
the disturbances and dislocations of the strata in a district already
known to be metalliferous, is calculated to afford indications of the
utmost value, and form a branch of Practical Geology, from the care-
ful pursuit of which the most interesting results may be anticipated.
1136. By examining the beds of mountain streams, and the gravel
or loose stones brought down into the plain country, a knowledge of
the existence of metalliferous veins in a district may often be at-
tained. By following up the indications thus afforded, an idea of
K K
498 PRACTICAL GEOLOGY.
the actual position of the veins, and even of their extent and value,
may also be acquired. This simple method was. no doubt, the one
by which many of the richest veins were originally discovered, and
it is still so far pursued, that sifting the gravel and sand of many
rivers in metalliferous districts is to this day a profitable under-
taking, and in some cases is the only kind of research pursued.
1137. " Stream-works," as undertakings are called in which this
method of obtaining ore is pursued, are in our own country chiefly
or entirely confined to the ores of tin, which, from their great specific
gravity, are readily separated by the action of running water from
the lighter sands and gravel with which they are associated. The
ores of tin worked in the Island of Banca, in the eastern Archipe-
lago, are entirely obtained in this way, and the quantity of ore brought
down by the mountain torrents may be imagined when it is men-
tioned, that as much as 3,500 tons of tin have been exported annu-
ally from that island alone.
1138. In other cases, gold, platinum, and other metals, in a
virgin state, are distributed in small grains in the sand, and this is,
in fact, the chief source of the precious metals from many districts
in Europe, Asia, Africa, and even some parts of America.
Some interesting observations have been recorded by the Russian mining engineers
with regard to these auriferous sands. It has been remarked, that they rarely repose
on granite or syenite, but usually on schistose rocks, near serpentines and hornblende
rocks. They are also found, not in the recesses of the mountains, but principally
forming plateaux parallel with and terminating the chain, or exhibited in the lower
and broader part of the valleys. They are not continuous, and in certain localities
the gold is more abundantly distributed than in others.
Generally the gold obtained by washings, and coming under the denomination of
alluvial gold, is distributed in comparatively small proportion throughout the quart-
zose sand covering very extensive areas. But this is not always the case. In Siberia
there appears to be a distinct epoch to which the auriferous alluvium belongs, and
over such beds are others forming a capping often of clay and shingle containing no
gold. It may easily happen in any other country as in Siberia, that there are
alluvia of different ages obtained from rocks at a distance, or from the decomposition
and disintegration of those in situ, some of them containing certain minerals, whilst
others are totally deprived of them. Some attention therefore is required, not
only in the selection of a spot which may be supposed to contain the proper mineral,
but in finding out whether the gold is present at all, or in greatest abundance in any
particular bed.
1139. In our own country the stanniferous gravels of Cornwall
are not usually upon the surface, but are either covered with other
gravel, or with clay, sand, or peat, which require to be removed be-
fore the fundamental rock is reached on which the tin-stones rest.
The gravel when collected is thrown upon an inclined plane, upon
which a fall of water is conducted, and then being worked about,
the tin-stones, if of sufficient volume, and provided the force of the
water is not too great, remain upon the inclined plane, while the
lighter stones and earth are washed away.
1140. It is from this method of separating the ore that such
PEOCESS OF SHODING. 499
works have been called stream-works. They are of comparatively
small importance now in reference to the general supply, but still
afford employment to a number of the poorer miners.
As, however, such a source must be, at the best, doubtful and un-
certain, and one which in most districts would soon fail, it becomes
necessary that the gravel should be gradually traced up the bed
of the stream, by whose rapid current it has been brought down,
until the metalliferous fragments of rocks, increasing in number and
volume, at last point to the spot where the outcrop of a vein at the
surface has been the origin of the supply.
1141. This method of arriving at the actual position of the vein
is called in Cornwall, shading or shoading,* and is a method of great
antiquity, being in fact an almost necessary preliminary to any regu-
lar mining operations. When the ore is thus discovered at its source,
it is not difficult to determine whether it is a thick bed of gravel, a
vein, or a mere lump of ore, and its direction and relations with the
surrounding country may be more or less clearly made out.
1142. The early history of the Cornish mines, and the nature of
mining operations in that country at the commencement of the 17th
century are recorded in a very interesting manner by Carew.f " He
first notices stream-works and lodes, and the opinion of the tinners
that the tin-stones in the stanniferous gravels were derived from the
lodes by the deluge. He next describes the process ofshoding, which
seems to have been then conducted much in the same manner in
which it is now practised, and he notices that the shode for the lodes
* either lieth open upon the grasse or is but shallowly covered.' Having
found this shode ' they next,' he says, ' sank pits of five or six foote
in length, two or three foote in breadth, and seven or eight in depth,
to prove where they may so meet with the load. If they miss the
load in one place they sincke a like shaft (pit) in another beyond
that, commonly further up towards the hill, and so a third and fourth
until they light at last upon it.' " J
1143. If the lode thus discovered offered a fair prospect of suc-
cess, the discoverer would usually associate others with him in the
working, and the company of adventurers thus formed appointed a
captain, whose duty it was to see that the men did their work pro-
perly, and who attended to the mine and to the pumps. The tools
used were extremely simple, and consisted only of a pickaxe and
shovel, but with these they would sometimes follow the lode to the
depth of 40 or 50 fathoms, the miners being let down and taken up
by a rope wound over a winch. In cases, however, where the hang
or inclination of the lode was considerable, the miners are described
* The fragments of ore which by rain or currents of water are torn off from the lodes or veins
of ore, are called shoads.
t Survey of Cornwall, by Richard Carew. (Reprinted 1769.)
J De la Beche's Report on the Geology of Cornwall, Devon, and West Somerset, p. 52J.
500 PRACTICAL GEOLOGY.
as working to a convenient depth, when they sunk a shaft from the
top " to admit a renewing vent, which notwithstanding, their work
is most by candlelight." The loose work was kept up by timber,
and the rate of progress appears to have been very slow, as we are
told, " a good workman shall hardly be able to hew three foote in the
space of as many weeks." *
1144. It will readily be imagined, that into pits thus sunk a con-
siderable quantity of water would drain, and it is clear that this was
an extremely troublesome and unmanageable difficulty, often induc-
ing the abandonment of a valuable mine. The draining machinery
is described as " composed of pumps and wheeles driven by a streame,
and interchangeably filling and emptying two buckets and such like."
In some cases, when the works were on a hill-side, canals were cut
from the lode to the nearest convenient valley, but they are described
as being " costly in charge, and long in effecting." And even where
these difficult and expensive means were resorted to, the water would
still have to be raised from such of the workings as were below the
level of the valley, and a speedy limit would be put to all workings
where the ore lay deep beneath the surface of the surrounding country.
1145. The description thus given of the superficial, and compa-
ratively simple works of a former age, is applicable in a very con-
siderable degree to more extended operations at the present day; for,
although the introduction of improved machinery has tended to
increase the facilities of working at great depths, the only difference
in principle is the establishment of an improved plan of working-
adapted to the nature of veins of different kinds, together with
that attention to ventilation necessary in all extensive underground
operations.
1146. The indications on the surface that may be presented by a
mineral vein, are not usually sufficient to attract general attention,
and would in most cases be so entirely hidden by a coating of gravel
and vegetable soil, as to exhibit scarcely any marks that would ena-
ble even the most experienced eye to recognise them. In the absence,
therefore, of metalliferous gravels which can be traced up the course
of a stream to a hill-side, and to the actual outcrop of a vein (and
even then wherever many veins intersect), the question must often
be determined more by experiment and tact, than by any distinct
indications of the spot in which it will be most advisable to com-
mence sinking, so that the greatest advantage shall be derived from
the vein, supposing one there to exist. In cases where their actual
presence is doubtful, but a probability appears of mineral veins being
discovered, a series of experiments called in Cornwall " costeaning" is
undertaken with the view of discovering the presence of a vein. This
method of experimenting is derived from the supposition that the
* Carew, ante tit., p. 10, 11.
DRIFTS AND LEVELS. 501
veins in the district follow some general law, and the operators, se-
lecting a convenient spot, commence by sinking a pit through the
soil, and to a small depth in the rock. Of course the chances are
many against immediate success, but in case they find nothing, the
next step is to drive, or cut a gallery from the pit a short distance
in opposite directions, at right angles to the direction of the lodes
found in the neighbourhood. In this way it is possible that they
may *' cut the lode ; " but if still unsuccessful, they remove a few
fathoms in the direction of the galleries, and repeat the same pro-
cess until they have either discovered the lodes, or give up the specu-
lation in despair. In matters of this kind, although experience is
often a better guide than abstract science, still there is no doubt that
the person best able to bring his experience to bear will be one who
is acquainted with the facts of Geology ; and such an one will avoid
many sources of error, because his conclusions will be founded on
rational premises. The great secret of economical mining lies in the
original adoption and proper carrying out of an uniform and well-
digested plan of working, and the student may rest assured that such
a plan can only be properly laid by an experienced mining engineer,
who is able to add an acquaintance with Geological facts to sound
practical and local knowledge.
1147. In the ordinary language of mining, pits open to the surface are called
sJiafts ; and in Cornwall those not open to the surface, but sunk from one gallery to
another, have received the name of icinzes. Horizontal galleries, excavated in metal-
liferous veins, are called levels, and those not in the metalliferous veins, cross-cuts ; but
that principal gallery, or tunnel, through which the drainage of a mine is conveyed to
the surface at the lowest convenient spot, is denominated the adit or adit-level. All ex-
cavations horizontally are called drivings, those downwards sinkings, and those upwards
risings.
1148. When the position of a mineral vein is ascertained, its
direction known, and some reasonable conjecture made concerning
its extent, thickness, and value, measures must be taken to obtain
by subterraneous excavation the buried mineral, and for this pur-
pose pits or shafts must be sunk, and galleries, or, as they are some-
times called, levels, must be driven, which prepare the way for the
convenient extraction of the ore, and at the same time carry off, so
far as may be, the water which either rises into the mine from springs
or drains into it from the surrounding strata. Of such galleries,
two sets must be driven at right angles to each other, and both hori-
zontal, one being in the direction of the strike of the vein, and the
other at right angles to that direction.
1149. The shafts sunk upon a vein are not always vertical to
meet the vein, but are occasionally commenced at the outcrop, and,
where the inclination is not very considerable, are continued in the
substance of the vein itself. This is not, however, so economical a
process as it may appear, for the difficulty of raising the ore is much
502 PRACTICAL GEOLOGY.
increased, and there are many practical reasons which often render
it expedient to sink at some distance from the outcrop so as to
meet the vein at a certain convenient depth.
1150. The act of sinking a perpendicular shaft downwards to a
depth where it is calculated the lode should be cut, may seem to re-
quire little further skill than is necessary to determine correctly the
spot on the surface where the work is to commence. But the process
in this way is exceedingly tedious, and in a mine at work where many
galleries already existing are to be traversed, much greater rapidity
is desirable. In such a case, the shaft is sunk in several pieces, or,
in other words, the sinking is commenced at the same time in seve-
ral different levels, and no small skill is required so to lay out the
work that the different portions of the shaft thus formed may exactly
fit when they are connected together. An exceedingly small error
of measurement in any one of these various and dark subterranean
passages, would, in fact, be sufficient to throw the whole into confu-
sion, but such an accident rarely happens, although works of the
kind are common in the Cornish mines.*
1151. In the same way, to drive an adit from one point to another
through many fathoms of country requires great skill, more parti-
cularly where, in order to save time, the work is commenced from
both extremities. About a quarter of a century ago (in 1824)
great complaints were made in Cornwall of the condition of these
channels ; and the necessity of attending carefully to the details of
draining was insisted on, and the proper position of the adit pointed
out by Mr. Carne. Owing to neglect in these matters, and to the
want of good surface-draining, a large quantity of water pumped up
from the deep mines, found its way back again among the work-
ings, and this happened to so great an extent that since that period,
greater attention having been paid to drainage, the quantity of water
pumped is considerably diminished, although the mines have become
deeper and more extensive ; and in many mines, where great care has
*been taken with reference to this subject, the improvement has been
very striking. Some idea may be formed of the extent of the drain-
age in mining districts from the fact that the various branches
of the principal level in Cornwall, called the " great adit" which
receives the waters of the numerous mines in Gwennap and near
Redruth, measure on the whole about 26,000 fathoms, or nearly thirty
miles in length. One branch only (at Cardrew mine) extends for
nearly five miles and a half, and penetrates ground seventy fathoms
beneath the surface. The water flows into a valley communicating
with a small inlet of the sea, and is discharged about forty feet above
high- water mark.
1152. In very extensive mines, such as are worked in Corn wall, it is
Pe la Beche's Report, ante cit, p. 563.
CROSS-CUTS AND CROSS-COURSES. 503
necessary to have many shafts and a very considerable number of levels
and cross-courses in order to carry on the general work of the mine.
In such cases there is usually a principal shaft, of considerable size,
sunk through as many lodes as possible, and communicating with all
the galleries. This shaft is often double ; one portion, called the
engine-shaft, being used only to convey the water from the deep
workings to the adit-level, and the other, the whim-shaft, to raise the
ores to the surface. The two shafts are in these cases close together,
and are united at convenient distances by short cross-cuts.
1153. It is always of importance to sink a shaft in such a way as
to communicate directly with as many as possible of the lodes worked
in a mine when, as is usually the case, several veins occur running
in the same direction, and at no great distance from one another.
In the Fowey Consols mine in Cornwall, as many as thirteen lodes
are worked, and they are so near each other that one shaft (the
Union) cuts through five of the lodes, and by means of a cross-cut
at the sixty-fathom level, communicates with all the rest. The
workings on different lodes are connected with each other by means
of cross-cuts, so that the ores may be brought to the shaft, not only
in the course of the lodes, but also at right-angles to their courses.
1154. These cross-cuts must be understood as having no reference
to cross-courses, which are unprofitable veins traversing the lodes at
right-angles. Great advantage, however, is sometimes obtained in
mining by observing the peculiar circumstances connected with the
traversing a lode by the cross-courses. Sometimes the latter are
scarcely touched, being only crossed at right-angles in working the
lode ; but they are occasionally used to drive adits upon. The cross-
courses are also generally connected with faults, and sometimes they
heave the lode, and bar the progress of the miner, while at other
times they tend to keep out the water accumulated in the old work-
ings of a neighbouring mine. It will be manifest that a considerable
amount of practical knowledge must be required to enable the miner
to venture on any speculations in a matter of so much importance,
and that an accurate notion should be had of the true mechanical
condition both of the lode and cross-courses, before any under-
taking that depends for its success on their mutual influence can be
safely commenced.
1155. The lowest part of the engine-shaft, called the sump, is
usually sunk a certain depth below the lowest workings, so that the
drainage of the mine makes its way into it. It is, however, also im-
portant that each successive level should be separately drained in
order that as little water as possible may descend to these lower
workings. The water raised is delivered at the adit-level, and so
escapes at the natural drainage-level of the district.
1156. The depth to which shafts are sometimes sunk below the
504 PRACTICAL GEOLOGY.
level of the surrounding country is sometimes, very considerable,
The Dolcoath mine, long celebrated for the depth and magnitude of
its workings, reaches to more than 210 fathoms below the adit-level,
which is itself 30 or more fathoms below some parts of the sur-
face. The main shaft of the Fowey Consols is but little inferior, and
there are several other mines both in Cornwall and elsewhere worked
to a great depth. The Tresavean, the deepest mine in Cornwall, is
now worked at a depth of upwards of 300 fathoms ; and a machine
has lately been erected there, by which the miners may be raised or
lowered as much as 240 fathoms. The advantage of this machinery
has already been greatly felt, and some contrivance of the kind would
be found useful in all deep workings.
1157. In these cases the difficulty of mining is increased by the
high temperature experienced in the workings, but the veins can
hardly be considered to exhibit any very decided and uniform change
in the value or amount of their contents, although in some cases ores
of different metals seem to abound most within certain particular
limits of depth. The increase of heat observed at considerable
depths has been already mentioned ( 37 ); but it seems to have some
reference to the nature of the rock and the contents of the veins.
1158. The underground work of a mine depends chiefly upon the
magnitude of the veins, and the value of the ore to be extracted.
A vein once reached, either by the shaft or by the cross-cut carried
horizontally from it, levels are driven at different depths (usually
about 10 fathoms apart, but depending on the nature of the mining
ground), and the whole horizontal section of the lode on each level
is excavated by galleries. In many cases the lode not being more
than a few feet in width, one such gallery is sufficient, and as it is
only necessary to leave a passage wide enough to extract the ore, the
levels at those places where the lode is narrow, or nipped in, are very
narrow and confined. Where the lode is broader, and also rich, the
open spaces are of course much larger, but there can scarcely be any
rule in a thing so variable as a mineral vein, for the portion worth
working, though small and with little ore in some places, may be
several feet across in others and extremely rich, or the vein may be
thin and rich in one place, and broad and comparatively poor in
another ; so that it may even be a question whether it is advisable
to take that part out at all.
1159. Sir H. De la Beche adds, " These are matters on which the
chief agents decide according to their skill and judgment. It is
usual in mines, particularly those worked on a large scale, and for a
continuance, not to take out all the ore which could be immediately
got at if thought necessary, but to leave it here and there, to be
worked as the general prospects of the mine may require, and to
which the miners return if less ore is raised generally in the adven-
VENTILATION OF MINES. 505
ture than could be wished. The ores thus left in various places are
called the eyes of the mine ; and when it may be necessary, in aban-
doning the mine, or from any pressing circumstances, to remove
them, it is termed ( picking out the eyes of the mine' In some mines
these eyes are very valuable, and much skill and judgment are em-
ployed in so arranging the workings that a general good supply of
ores may be obtained." *
1160. There are, however, distinct methods of proceeding when
it is required to extract very large masses of ore, and in those cases
where the horizontal section is too large to be at once excavated,
pillars are left to support a roof, and cross-galleries are driven, inter-
secting one another. In order to avoid loss as much as possible, it
is necessary in such cases to make the galleries lofty, and artificial
support is given to the roof by timbering : but accidents can hardly
He avoided when this method is carried on to a great extent.
1161. Connected with these operations of mining, and so contrived
as to effect the required purpose in the best way, are the arrange-
ments made for a proper supply of fresh air in the workings. The
means of obtaining this are simple where there is no evolution of
noxious gas, and they consist chiefly of making a proper use of the
numerous shafts, and of the communications effected from shaft to
shaft by the different levels or galleries. When these communica-
tions are properly made, currents are found to set in different direc-
tions, varying probably according to the variable temperature of the
atmosphere at the surface and the uniformly high temperature under
ground, and it is rare that any mechanical means are resorted to for
ventilating the mine, except in such cases as where a level is in
progress to communicate with a shaft. Generally speaking, the air
becomes vitiated to such an extent that candles cease to burn brightly,
long before it is sufficiently bad to destroy life ; and, in fact, it is
so impossible to continue to work a mine in this state that accidents
rarely happen.
1 1 62. The veins of copper and tin, common in Cornwall, are for
the most part not sufficiently thick to require any extraordinary
method to be employed in extracting the mineral riches, but timber-
ing is necessary to avoid the danger that would arise from the sinking
in of the upper side of the vein.t In Derbyshire and Alston Moor,
however, whence the chief supplies of lead ore in England are ob-
tained, the veins traversing the mountain limestone swell out and
become productive chiefly or entirely in one bed of limestone, and
they there attain so great a thickness as to admit of being extracted
* De la Beche's Report, p. 56 1.
t The quantity of timber used annually in the Cornish and Devon mines 18 very considerable,
and consists almost entirely of Norwegian pine. Sir Charles Lemon having counted the rings
of annual growth on several of the trees, considers that the average age of the timber employed in
the Cornish mines is about 120 years, and that it would require 140 square miles of Norwegian
forest to afford a supply for these mines. De la Beche's Report, ante cit. p. 573.
506 PRACTICAL GEOLOGY.
by methods very different from those necessary to be resorted to in
the Cornish mines.
1163. There are certain local names given to peculiar forms of
mineral veins in the North of England, which must be now explained,
while referring to the mining operations of the district. The most com-
mon of these veins is the rake vein, which is a vertical crack or fissure,
or rather a group of such fissures, parallel to each other, and fre-
quently crossed at right-angles by small pipe veins ; these pipe veins,
the most important to our present purpose, are, in fact, horizontal
expansions of the vein between certain beds of limestone, and are
filled with the mineral matter which forms the matrix of the ore
(barytes, fluor spar, calc spar, &c.).
1164. The appearance of one of the larger pipe veins is very
curious, the vein being only rich where it expands on entering a par-
ticular bed of limestone. In the Alston Moor district there are many
instances of this kind in the lead mines, and others are known in
which rich ores of iron are worked, the masses of mineral substance
being so extensive as to fill expansions of a vein, which when exca-
vated leave vast subterraneous caverns.
1165. In order to obtain the ore from the vein, and break it into
masses of convenient size, many processes have been formerly em-
ployed, which have almost all given way to that of blasting with
gunpowder. By the Saxon Geologist, Werner, rocks were divided
into five classes, according to their degree of hardness, the first being
sandy and friable, and capable of being removed with the spade, and
the second including those rocks of moderate hardness, such as coal,
the Oolitic limestones, gypsum, shales, and slates, which require to be
dislodged with the pick and removed in masses by the aid of levers
and simple machinery. The third class of rocks includes those which
are harder, but still not so hard as to strike fire with flint, and they
may be removed partly by blasting, but chiefly with common picks,
levers, and such simple machines. The fourth and fifth classes com-
prise rocks both hard and tough, and also those which are splintery,
and they cannot be at all touched except with blasting, and even then
sometimes scarcely repay the trouble and expense of working.
1166. After the ore has been detached from its matrix, it is ne-
cessary, of course, that it should be transported, in the most conve-
nient way, to the bottom of the shaft, up which it is to be brought
to the surface ; and in large and well regulated mines, tram-roads
are now commonly used, and the dimensions of the waggons, or
corves (from the German korb, a basket), very carefully calculated ;
but in many mines, more especially those in South America, human
labour is still employed, men, and even women, carrying on their
heads heavy weights up the numerous and steep ladders that com-
municate with the upper ground. In France and Germany, and in
MINING RECORDS. 507
our own country, human labour is also employed, although chiefly
in propelling, or drawing along underground galleries, the loaded
waggons charged with the mineral produce of the mine.
1167. Great improvement has been effected of late years in the
mode of transporting the ores underground, by the introduction of
such small tramroads and waggons, instead of the old practice of
wheelbarrows and planks ; and the saving of expense thus effected is
very great, amounting, in fact, to one half the former cost. Many
extensive mines are provided with miles of subterraneous rail-
road, and the advantage is greater, because for the most part there is
a slight descent from the workings to the bottom of the shaft, to
allow of a more complete system of drainage than could otherwise be
attained.
11G8. The ores are usually lifted by machinery from the bottom
of the shaft to the surface, and in all extensive mining operations
this machinery (the whim) is worked by steam-power ; but although
steam-whims are now common, horse-power is still used to some
extent. The quantity wound up at one time varies, but sometimes
amounts to half a ton, or more. In a very few instances inclined
planes assjst in raising the ore, but it is only under peculiar circum-
stances that they can be used with advantage.
1169. It is not possible to conclude this account of mining opera-
tions more appropriately than by a reference to the important subject
of mining records, the value of which is often felt in England where,
in consequence of the small interference of Government in any form,
proprietors are allowed sometimes to neglect their own best interests
to the ultimate injury of their neighbours' property.
1 1 70. With regard to mining records generally, perhaps the fol-
lowing are those most important to be attended to, and copies of them
should be preserved in some public place, with respect to every
mineral vein worked in the country.
I. Accurate underground plans of the works on each level, and
vertical sections through every vein and cross-course worked in the
mine. To these plans should be attached notes referring to every
fault and slip met with, its amount, direction, and effect on the vein,
and the changes occurring from time to time in the vein, on passing
into new ground, or traversing a dyke.
II. With regard to the veins themselves.
A. The exterior relations of the vein.
1. Its position, viz. : its distance from known points, its direction, and its
inclination.
2. Its magnitude, viz. : its length and width at various points, the manner
in which it terminates, and the way in which it ramifies.
B. The internal state of the veins.
1. The predominating ores and veinstones, and the order in which they are
found in relation to one another.
508 PRACTICAL GEOLOGY.
2. The other ores and veinstones, and the circumstances under which they
also occur, their frequency, size, richness, and the places where they are
found.
3. The remaining internal circumstances of the vein ; the fragments of rock
found mixed with the substance of the vein ; the mechanical condition of
the filling up of the vein ; the walls which separate it from the adjacent
rock ; and the nature of its adherence to the rock.
c. With regard to the adjacent rock.
1. Its nature and its Geological relations with the vein.
2. The inclination of the strata, if the rock is stratified, and the predominating
joints and divisional planes.
3. The condition of the rock near the vein, and the greater or less amount of
decomposition it has suffered ; a statement of the metallic particles with
which it is impregnated, and the fractures it has undergone.
4. The effect of the surrounding rock upon the vein, as well as that of the
vein upon it.
D. The relation of the vein under consideration with the other
veins which it meets, and reciprocally.
\. The direction and inclination of the veins at the point of meeting, the
nature of the ores and veinstones, and the change, if any, that takes
place at the intersection.
2. The peculiarities presented by smaller veins or threads, at their intersection
with the principal vein, observing the following points:
a. If, after meeting, they continue together for some time.
b. If the veins that meet the principal vein also cross it ; or,
c. If they are crossed by it.
d. If they produce ramifications, break the vein, or are broken by it ;
disturb it, or have been disturbed by it ; and the magnitude of all
these effects, if they have been produced.
e. If they intercept and stop the course of the principal vein, or
change it into mere threads, or are themselves intercepted by, and
swallowed up in it.
E. The principal works done in the vein.
Under this head should be noticed the excavations, and other trial works made in
new ground, whether successful or not in finding ore, as well as all details connected
with the regular workings. An account should also be given of the extent of each
mining property and the name of the proprietor.
1171. The above intimation of the kind of information required
concerning mineral veins is chiefly taken from Werner's " New
Theory of the Formation of Veins," a translation of which into
English was published at Edinburgh in 1809, and he adds : " Such
an account of mineral repositories requires much trouble, and a con-
siderable time, to render it complete ; but, from the very commence-
ment, every step made in the labour will be profitable and useful
of itself ; while it is only by adding, from time to time, the new
observations arising from our labour that we can hope to render it
perfect. Such a description of a mining district would indeed
form together a complete and instructive whole. If our ancestors
had left us such documents for two centuries past, or even for half a
century, of what advantage would it not have been to us ? From
MINING RECORDS. 509
what doubts would it not have relieved us ? With what anxiety
do we not turn over the leaves of ancient chronicles in search of
information, often very imperfect, obscure, and uncertain 1 With
what pleasure do we not receive the least sketch or plan of some
ancient mine 1 With what pains do we not rake up the heaps of
rubbish brought out of old excavations, to discover pieces which may
afford us some idea of the substances which were formerly worked
out ? Yet between these documents and those which we might ob-
tain in the way pointed out in the preceding paragraphs, there is
as much difference as between night and day. Ought it not to be an
obligation and a duty, for us to collect and leave to future genera-
tions as much instruction and knowledge as possible on the labours
carried on in our mines, whether it be in those that are still worked,
or in those which have been given up."*
1172. But it is no less necessary that mining records should be
preserved of those districts worked for coal and other mineral pro-
duce obtained from seams and beds, than that an account should be
kept of mineral veins. We may quote the authority of the late Mr.
Buddie, with reference to this subject, and in testimony that " the
inconvenience and unnecessary expense which have frequently been
occasioned in the Newcastle and other coal-fields, as well as the many
fatal accidents which have happened from the want.
1173. The nature of the records, and the information which it is
suggested by Mr. Buddie they might include, may be arranged under
the following heads :
1. The name of the proprietor of the surface and minerals.
2. The locality and extent of the property.
3. The number and description of the seams of coal and other minerals which it
contains.
4. The thickness and quality of the several seams of coal ; which of them have
been worked ; to what extent they have been worked ; and why the working of any
of them has been discontinued, or not commenced.
5. The winning of the colliery, viz. : The number and position of the shafts ; the
difficulties met with in sinking, and the method of overcoming those difficulties.
6. The system of working ; whether by pillars, by the long method, by panel
work, or in what other way.
7. The dip and rise of the colliery. Description of the dykes, &c.
8. An account of the accidents that have happened by explosion.
9. The other accidents that have happened in the colliery, with their causes.
10. The system of ventilation practised.
1 1 . General observations.
1174. To these may be added, in those districts where the ores of
iron are bedded with the coal, an account (1) of the number, thick-
ness, position, and extent of the seams of iron ore ; (2) their rela-
tive value, and the percentage of metal obtained from them ; and
(3), the manner in which they have been worked, whether subordi-
nately to the coal, or as a principal mineral product. Besides this,
* Werner's " New Theory of the Formation of Veins," translated by Dr. Anderson, p. 205.
510 PRACTICAL GEOLOGY.
very particular attention should be paid to the preservation of accu-
rate plans of discontinued workings, with such references as may
render it impossible to mistake the localities to which these plans refer.
This latter is the more necessary, since, up to the present time, and
even in cases where reports of the state of the underground work-
ings have been preserved, they have often been found useless, owing
to the impossibility of identifying the pits. This inconvenience was
very strikingly exhibited in the drowning of the Hetton colliery in
1815, the water breaking in from workings which had not been re-
linquished more than 70 years. It should be very carefully noted
in the description of relinquished workings, whether the pits are
filled up or only scaffolded ; and if the latter, at what depth. The
compass bearings of all the workings should also be laid down, and
the amount of magnetic variation recorded, that at any future time
the accurate position of the underground excavations might be under-
stood and ascertained at once from the plan.
It should also be remembered, that those who are desirous
of assisting in this important work, should not be deterred from
giving very full and detailed accounts from the apprehension of being
considered too prolix and tedious, as on such a subject it is more
excusable to say too much than too little.
Conclusion.
1175. The object in the preceding pages has been to offer to the
student of Geology in systematic order those facts upon which the
science is based, the deductions fairly made from them, and the more
immediate and direct applications of them to practice. Commencing
with the outlines of Chemistry, the only sure basis of natural know-
ledge and the alphabet of nature's language, I have endeavoured
to explain in a general way those combinations of elementary sub-
stances most frequently met with, the forces acting upon matter and
the laws by which the action of those forces is governed. From a
very brief review of these points I have proceeded to exemplify them
in an account of the existing condition of the earth's surface, and
the changes now in progress tending to modify the physical features
of various parts of the world, endeavouring to give a rational and
true account of the various phenomena of the surface the forms of
continents and islands, the mountain and river systems, and generally
the horizontal and vertical profile of our globe. All these facts and
descriptions, which together form one great department of Physical
Geography, are followed by a statement of atmospheric and aqueous
action, going on constantly, and tending to alter the earth's surface
by reducing inequalities ; and this again is succeeded by an account
of those subterranean movements, whose result is to add to inequali-
RECAPITULATION. 511
ties of surface already existing, or produce others in new directions.
It is shown thus that there is no repose on or within the earth's
surface, and that every day opens to a different scene from that which
closed on the previous night.
Taking then another great department of natural science, I have
endeavoured to explain arid illustrate the nature of these solid ma-
terials, or mineral substances, of which the whole superficial crust of
the earth is made up. The singular relations of form, and the
various other physical characters of these substances are first dwelt
on, and then the actual properties of the minerals themselves. This
part of Geology possesses an interest and importance which no one
can deny, and which requires special and careful study.
From the study of the materials we properly advance to that of
the order of arrangement of these materials ; but I have first enlarged
on those very important proximate elements of Geology the simple
rocks, as distinguished from, or made up of, the simple minerals.
These and their condition being explained, I have dwelt at some
length on the structure and mechanical position of rocks, endea-
vouring to illustrate the true meaning and vast importance of those
changes of condition, or phenomena of metamorphism, a knowledge
of which is the key to all the higher speculations and many applica-
tions of Geology.
Advancing next to the description of rocks, I have illustrated
this part of the subject by a brief account of the various stratified
deposits, commencing with those of most modern date ; and, while
the various rocks were brought successively under notice, in order of
the date of their formation, 1 have endeavoured to keep before the
reader constantly the fact that group after group of different forma-
tions some deposited under water, and some on land ; some indi-
cating the existence of a sea, and others of an estuary or a river have
occupied, one after another, districts now elevated high above the
waves, and exposed to our researches. The reader will, thus, have
perceived not only the fact of successive deposit, but also that the
races of animals and vegetables have changed, making it clear
that the greater portion of the earth's crust so far as it is at present
known is made up of a series of strata overlying one another in
regular order, and most of them containing abundant remains of
organised beings.
I have also, from time to time, alluded to the fact that these
beds have been disturbed and displaced by mechanical violence
acting from beneath, producing various appearances of movement
and dislocation, and connected with the more extreme cases of
metamorphism and the outpouring of crystalline rock once existing
beneath the surface in a state of igneous fusion.
Having thus completed the outline of Descriptive Geology, in
512 PRACTICAL GEOLOGY.
which, however, analyses of most of the rocks accompany the more
general descriptions of them, I have, in the last two chapters, ex-
plained more immediately the mode of application of Geological
knowledge to engineering and mining, as the natural and fit con-
clusion to the whole subject.
It only remains now to state, that in order to arrive at any useful
practical result, the student must possess clear and definite notions
concerning the fundamental facts of Geology, including under this
head the nature of simple minerals, the laws of chemical combina-
tion and affinity, the nature of simple rocks, the position of rocks,
and the nature of their disturbances, dislocations, and metamor-
phoses. Without this kind of knowledge all other is superficial and
essentially unpractical the student may be learned in what others
have done, but he can make no useful observations or deductions that
are at all to be depended on.
But let me explain what this means. I do not intend to say that
in order to become a useful observer and to be capable of applying
Geological knowledge to practical purposes the student must be a
perfect adept, or master of all details and views of the science. This
is by no means necessary. What is wanted is rather a philosophical
knowledge of general principles a knowledge obtained not merely
by reading books or listening to lectures, but by reflection and actual
observation. In this way only can the pursuit of any science be
useful, and this is the way in which I would hope the present volume
may be found available, and to some extent suggestive. I have
endeavoured not merely to describe facts and quote the observations
of Field-geologists, but rather to teach principles, leaving it to the
reader to apply these principles and digest the facts, working out
thus a sufficient education in the subject.
Geology is a science of induction derived from a multitude of
observed facts and experiments the experiments being, indeed,
those which nature has made for us, and which it is our business to
investigate. The facts observed are too numerous, too distinct, and
too nearly connected to admit of any fear that the legitimate conclu-
sions that have been drawn from them can ever be shaken. By the
study of Geology, as of every branch of Natural History, the mind
becomes stored with knowledge of the highest importance and
the deepest interest ; and in accumulating, arranging, and digesting
this knowledge, we gradually become familiar with the generalisa-
tions to which it leads, and are at length able to make use of and
apply it.
THE END.
APPENDIX.
EXAMINATION PAPERS IN GEOLOGY.
As a useful conclusion to this work, and also as illustrating the
mode by which the Author has endeavoured to discover how far
the knowledge of Geological students is satisfactory and real, a series
of papers is appended which have been employed in the examina-
tions on Geology held by him at various times at those public insti-
tutions with which he has been and is connected. The papers are
given without alteration, arranged according to date, and thus many
repetitions of questions may be observed, but this has been thought
no disadvantage, as it illustrates the points which have seemed most
important, or to which, in the course of the Author's experience,
there has been most difficulty in obtaining satisfactory replies.
KING'S COLLEGE, LONDON.
June, 1840.
GENERAL EXAMINATION IN GEOLOGY.
1. Explain shortly the nature and objects of Geology, and the three
principal branches into which, as a science, it must be divided.
2. What is stratification ? What do you understand by the
expressions stratified rocks and unstratified rocks ? Exemplify
your meaning by applying the terms to some particular
instance.
3. How are strata identified ? State the relative value and
importance of the different methods by which they may
be identified. What are fossils ? In what kinds of rocks
are they found ? What kind of remains of organised beings
are most abundant, most characteristic, and therefore most im-
portant 1
4. In what strata, or group of strata, are the remains of mamma-
lian animals most abundant 1 What ways are there of ex-
L L
514 APPENDIX.
plaining the fact that they are chiefly confined to the less
ancient deposits 1 Can you mention any instances in which
such remains do occur in strata of great relative antiquity ?
5. The remains of animals of the lizard tribe (or Saurians) are
extremely abundant in one stratum which they characterize :
mention the name of this stratum, and give some account of
the more remarkable forms of these animals.
6. Give some account of Tertiary formations generally. How are
they sub-divided, and for what reason ? What are the local
names for the principal English groups ? To which of Mr.
Lyell's sub-divisions do they respectively belong ?
7. Indicate, by means of an ideal section, the principal sub-
divisions of the Secondary system, including in that title all
fossiliferous rocks below the Tertiaries. What is the most
remarkable fresh-water group among the Secondary rocks,
and in what part of England is it chiefly developed ?
8. The Oolitic New red sandstone and Carboniferous systems
are each of them remarkable in England for some products
extremely important and useful to man. What are these pro-
ducts, and where are they respectively found in most abund-
ance and greatest excellence ?
9. Explain the following terms made use of in Geology, viz :
dip, strike, fault, anticlinal and synclinal axis, conformable
and unconformable stratification. Which of these indicate
the action of a disturbing force ? What was the probable
nature of such force 1 Mention instances of the action of
subterraneous forces at the present day.
10. Enumerate various occasions on which a knowledge of Geology
may be useful to the practical man. Explain the nature of
Artesian wells. Refer, if you are able, to the various Geo-
logical causations by means of which water rises to the surface
in natural springs.
11 What are the more abundant ores of metal worked in this
country ? Give such particulars as you can explaining the
usual conditions under which are found (1) Iron, (2) Lead
(3) Tin. Mention also the different methods of obtaining the
metals which are most common.
1.2. Explain the nature and probable origin of Coal. In what for-
mation is it most abundant in this country ? Give some
account of the method of working it of the peculiar dangers
to which the miners are exposed, and of the contrivance by
which they may secure themselves.
EXAMINATION PAPERS. 515
II.
KING'S COLLEGE.
June, 1841.
GENERAL EXAMINATION.
1. Define Geology, explaining
a. the meaning of the word ;
b. the immediate objects of research in the science of Geology ;
c. the various modes in which it may become useful to prac-
tical men.
2. a. Distinguish between alluvium and diluvium.
b. Under what circumstances do either of them occur ?
c. To which of them is the gravel of England referred ?
d. Mention any observations by which various beds of gravel,
may be identified, and shown to have proceeded from one
spot or one point of the compass.
e. What kind of fossils are chiefly met with in gravel ?
3. a . What do you understand by stratification ?
b. Mention instances of stratified and unstratified rocks.
c. What is the nature *of the evidence on the strength of which
it is assumed that stratified rocks are for the most part of
aqueous and unstratified rocks of igneous origin ?
d. In what part of England are unstratified rocks more com-
mon than stratified ?
e. Explain the meaning of dip and strike.
4 State, shortly, the steps in the argument by which it may be
proved to a person ignorant of Geology, that each well-de-
fined fossiliferous stratum occurring in England was formed
with comparative slowness at the bottom of water : that
it is utterly impossible that any two, as, for instance, the
mountain limestone and lias, should have been formed con-
temporaneously, but that each was deposited in its place
successively, in many cases long after those beds found be-
low it, and long before those seen lying above it.
5. a. What beds are included under the denomination, Tertiary
formations 1
b. How have they been subdivided
1. with reference to their fossil contents ?
2. with regard to local differences of appearance ?
c. Mention the names that have been given to British Tertia-
ries, and the Geological period to which each is referred.
d. Mention, also, the kinds of fossils most remarkable and most
abundant in each.
516 APPENDIX.
e. I . With which of the English Tertiaries are the beds in the
neighbourhood of Paris contemporaneous 1
2. For what fossils are the Paris beds most remarkable 1
6. a. Express by means of an ideal section, the principal subdivi-
sions of the Cretaceous and Oolite systems, as they are
known in England.
b. What peculiar genera of fossil shells are most remarkable in
these beds, and in what do they differ from the shells of
animals living in the present seas ?
c. Are you aware of any general fact with regard to the extinc-
tion of species that first attracts attention in examining
the fossils of the Cretaceous system 1
7. a . In what respect does the group of strata, denominated Weal-
den, differ from the other groups of the Oolitic and Cre-
taceous systems 1
b. Mention a few of the more remarkable fossils characteristic
of the Wealden beds.
8. a. 1. In what formations is Coal found, and
2. With what mineral is it associated ?
6. What are the chief fossils of the Coal 1
c. Give some account of the probable origin of Coal.
9. a . What is meant by the term mdamorphic rocks ?
b. 1. Quote some examples of rocks of this kind.
2. Show in what way, and
3. To what extent they form a link between fossiliferous and
non-fossiliferous rocks 1
10. a. It is concluded by Geologists that there have been disturb-
ances caused by, or connected immediately with, volcanic
eruptions and earthquakes at all periods of the earth's his-
tory. State some of the more striking facts from a consi-
deration of which this conclusion is warranted.
b. Are you aware of any actual experiments which identify
ancient basalt with recent volcanic products ?
11. a. Explain clearly the difference between stratification, joints
and cleavage, under the following heads :
Stratification and joints.
Stratification and cleavage.
Joints and cleavage.
b. In what way can joints and cleavage be accounted for, when
they occur in metamorphic rocks 1
12. a. Explain the meaning of the word fault.
b. Show that in the case of the coal strata, the existence of
faults is of great economical importance.
c. What do you understand by anticlinal and synclinal axes ?
EXAMINATION PAPERS. 517
13. a. What are the different kinds of stone used in building ?
b. State some of the advantages and disadvantages of each.
c. By what methods of examination may the value of a stone
for building purposes be best discovered ?
d. 1. Mention a few of the principal building stones in Eng-
land, and
2. The geological position of each.
14. a. What is a mineral vein ?
b. What proof is there that mineral veins are of various ages ?
c. Are you aware of any very general law with regard to the
direction of mineral veins 1
d. In what direction are metalliferous veins most likely to be
met with 1
e. Mention the principal metals found in England.
/. Mention, also, the formation in which each most usually
occurs.
15. a. Explain fully the nature of Artesian wells.
b. In what way can the existence of springs be explained, where
it is impossible that the principle of Artesian wells could
apply 1
c. Under what circumstances is the drainage of land likely to
be most effective 1 ?
d. What are the usual Geological phenomena of Fen districts 1
III.
KING'S COLLEGE,
June, 1842.
GENERAL EXAMINATION.
1. State fully what you suppose to be the meaning of the word
Geology. Explain what are the objects of research when a
person endeavours to make himself acquainted with the geo-
logy of a district and mention the general results which the
study of Geology as a science may be expected to realise.
2. Explain the origin of Valleys : viz. (1) Valleys of Elevation,
(2) Valleys of Denudation.
3. Mention the causes that have been assigned to account for the
accumulations of gravel in various parts of England and
Northern Europe. Enumerate also a few of the animals whose
remains have been found most commonly in this deposit.
4. What do you understand by stratified and unsiratified rocks?
In what way do the latter usually make their appearance ?
518 APPENDIX.
5. Explain the cause of the trough or basin-shape of Tertiary for-
mations. Give some account of the older Tertiary rocks of
England and France.
6. In what respect do the calcareous beds of the Cretaceous group
differ from those of the Oolites ? Mention the most valuable
economic products of the Oolite, New red sandstone, and Car-
boniferous formations respectively.
7. What are the usual limits of the thickness of workable beds of
Coal in England 1 Explain the different methods employed to
obtain coal known as the long-wall and the pillar and stall
method. What are the advantages of each, and the local cir-
cumstances which prevent the most economic from being made
use of in some districts 1
8. State clearly the distinction between a bed containing mineral
produce and a mineral vein, and illustrate your explanation by
referring to examples in various parts of England.
What are the most important Metals found in England, and
where do they chiefly occur 1
9. Explain the Geological use of the word fault, and show in what
way the occurrence of faults is connected with the phenomena
of springs. If a well be dug through clay into sand, state
clearly the conditions that are necessary in order that water
may rise through the clay and form an Artesian spring.
IV.
KING'S COLLEGE.
June, 1843.
GENERAL EXAMINATION.
1. Define and illustrate the following terms used in Geology, dip,
strike, fault, anticlinal axis said, fossil.
2. Write down the principal subdivisions of the Secondary rocks
in England beginning with the New red sandstone group, and
mention any remarkable organic remains that you consider to
characterise the successive groups.
3. What are the principal Tertiary strata met with in England
and where do they occur ?
4. To what cause do you attribute the fact that almost all the Sedi-
mentary rocks are in a position inclined more or less to the
horizon? Are you acquainted with any recent phenomena
which assist in explaining the nature of the disturbances met
EXAMINATION PAPERS. 519
with in the older rocks 1 Mention any effects similar to those
observed in the older rocks, but which are due to the action of
modern causes,
5. What is the nature of mineral veins ? Give such account as
you are able of the theories that have been proposed to account
for the phenomena of metallic lodes.
6. Explain fully the difference between a metallic vein and a bed
of coal. Which are the principal Coal-fields in England ? To
what accidents are coal-fields more particularly liable, and how
has it been attempted to avoid them ?
7. What are the principal building-stones used in England, and
in what Geological formations do they respectively occur 1
8. Explain the nature of land-springs, fault- springs, and inter-
mittent springs, giving an example of each.
V.
KING'S COLLEGE.
June, 1845.
GENERAL EXAMINATION.
1. Give a general account of the nature and objects of Geology
and the different ways in which it has been applied to practical
purposes.
2. Define stratification. Explain what is meant by conformable
and unconformable stratification. What is a fault, and what
an anticlinal axis ?
3. Explain the meaning and present use of the term fossil. What
kinds of fossils are most abundant, and in what way are they
especially useful in Geology 1
4. Mention any fossils that you may know which are character-
istic of particular formations.
5. Write down in order a list of the chief groups of strata, and
the name by which each is distinguished.
6. What are the principal rocks not usually found stratified 1
Distinguish between granitic, basaltic, and metamorphic rocks.
1. Explain the difference in principle between mining for metallic
ores in veins and mining for coal.
8. How is salt found in nature ? where are there extensive salt-
mines ? and what is the geological nature of the associated
rock?
520 APPENDIX.
VI.
COLLEGE FOR CIVIL ENGINEERS, PUTNEY, SURREY.
May, 1845.
GENERAL EXAMINATION. ELEMENTARY GEOLOGY.
1. What is the object of Geology, and of what nature are the ob-
servations and facts on which the science of Geology is founded.
2. What is the meaning of the following terms used in Geology,
namely : dip, strike, anticlinal axis, and fault,
3. What are the principal groups of strata, and the order in
which they are arranged on the earth's surface.
4. Mention, so far as you are able, the chief characteristic pecu-
liarities of the mountain limestone, the oolitic limestones and
the chalk.
5. What is meant by a river delta 1 and what proof is there of
accumulations of mud formed at the mouths of rivers where
no delta occurs ?
VII.
HONORABLE EAST INDIA COMPANY'S MILITARY
SEMINARY AT ADDISCOMBE.
September, 1845.
GENERAL EXAMINATION.
1. Of what nature are the materials of which the earth's crust
is made up, and in what condition are they generally found ;
distinguishing between crystalline minerals and rocks, and
using the latter term in its Geological sense ?
2. What are the principles of Geological classification 1 Write
down the Geological sequence of rocks in England, and the
most remarkable fossils of each group.
3. Under what circumstances of association with other rocks is coal
generally found ? How is its presence generally known on the
surface 1
4. What kind of rock is basalt ? Is the presence of basalt any
guide in determining the age of other rocks 1
5 Of what Geological age are the laterite, kunkur, and regur, or
cotton soil of India, and what is the general character of each
of these rocks ?
6. Explain the nature of Artesian springs, and the Geological
condition of the districts in which such springs may be ex-
pected to occur.
EXAMINATION PAPERS. 523
VIII.
KING'S COLLEGE.
March, 1840.
SCHOLARSHIP EXAMINATION. MINERALOGY AND GEOLOGY.
1. What are the physical characters of a mineral ?
2. Describe a simple mineral.
3. State the component minerals of granite.
4. Define the terms" dip, strike, and fault.
r ). Explain what is meant by a geological section.
'. Mention the kind of fossils most characteristic of the Coal-
measures.
IX.
KING'S COLLEGE.
June, 1846.
GENERAL EXAMINATION.
1 What do you understand by the term stratification ? Mention
an example of a distinctly stratified rock, and of some unstra-
tified rock. Explain the nature of the changes which have
affected stratified rocks since their first formation. Define the
terms dip and strike, fault and anticlinal axis.
2. What are fossils ? Mention in what formations fossil reptiles
are most remarkable and most abundant*. What parts of
animals and vegetables are found fossil ; and in what condition
are fossils found 1
3. Write down the main sub-divisions of the Palaeozoic period.
4. Distinguish between stratification and cleavage, and give some
account of metamorphic action, mentioning both its nature and
some of the results.
5. Explain the difference between Land springs and Artesian wells.
Explain the cause of the latter.
G. In what Geological formation do we find beds of Coal I State
the practical difference between working coal and obtaining
metallic ores from mineral veins.
7. What are the most important Metals found in England, and
where do they occur ?
8. State some of the facts that have been adduced in proof of the
hypothesis of the central heat of the globe.
522 APPENDIX.
X.
H.E.I.C. MILITARY SEMINARY, ADDISCOMBE.
Sept. 1846.
GENERAL EXAMINATION. MINERALOGY AND GEOLOGY.
1. Explain the general structure of the earth's crust as made
known by the study of Geology. Explain the meaning of a
Geological map and Geological sections.
2. What do you understand by the terms dip and strike ? If a
bed dips to the east, what is the direction of the strike ?
3. Under what circumstances is it likely that water will be ob-
tained in a district whose Geology is known, by sinking on the
Artesian method. Show in what way a knowledge of the
Geological structure of the district assists in arriving at this
conclusion.
4. Mention the most remarkable coal-districts at present known
in India.
5. In what way is a knowledge of fossils useful in Geology ?
What kind of fossil remains must be considered most generally
useful for such purpose ?
6. What is meant by cleavage in Mineralogy and Geology ? Ex-
plain also the nature of isomorphism, and mention any groups
of isomorphic minerals.
7. What is basalt ? and where is there to be met with the most
remarkable development of tabular basalt ? Has the presence
of basalt any influence on the industrial resources of a country ?
8. Under what circumstances are diamonds obtained in India 1
XL
KING'S COLLEGE.
June, 1847.
GENERAL EXAMINATION.
1. Illustrate the nature of those modifications of the earth's crust
produced by the action of water in motion. Mention the most
remarkable river Deltas in the world.
2. What is an earthquake 1 How are earthquakes connected with
volcanoes and volcanic disturbance ?
EXAMINATION PAPERS. 523
3. What is the ordinary condition of the materials of the earth's
crust ? Distinguish between igneous rocks, aqueous rocks, and
metamorphic rocks ; mentioning examples of each.
4. Explain the terms used in Geology with regard to the position
of rocks, namely : dip, strike, anticlinal and synclinal axes,
conformable and unconformdble superposition, fault.
5. Write down the general sequence of stratified rocks in England.
6. What are fossils ? Of what use are they in Geology 1 And
what do you understand by the statement that " fossils are
characteristic of formations ?"
7. Explain the phenomena of Artesian springs. Give an example
of some successful sinking for water by the Artesian method ?
XII.
PUTNEY COLLEGE.
July, 1847.
GENERAL EXAMINATION. MINERALOGY AND GEOLOGY.
1. What are the principal characters of quartz ? How do you
determine quartz from carbonate of lime ?
2. What minerals represent the scale of hardness 1 ?
3. What is meant by cleavage in Mineralogy and Geology 1 Ex-
plain the nature of isomorphism, and mention any groups of
isomorphic minerals.
4. Define the terms dip, strike, fault, and anticlinal axis. Explain
the meaning and use of Geological maps and sections.
5 Write down the various groups of stratified rocks found in
England in their order of superposition.
0. Give a general account of the Oolitic series of rocks, mentioning
some of the localities where valuable building stones are
obtained ?
7 .What is Granite ? In what does granite differ from basalt ?
and what are the characters common to the two 1
8. Explain the nature of intermittent springs, and the mode in
which they are supposed to originate 1
9. What is Coal 1 Where are deposits of coal chiefly found ? What
is the difference between a bed or seam of coal and a mineral
vein ?
10. Under what Geological conditions may drainage be effected for
works erected on stratified rocks ?
524 APPENDIX.
XIII.
H.B.I.O. MILITARY SEMINARY, ADDISCOMBE.
September ; 1847.
GENERAL EXAMINATION. MINERALOGY AND GEOLOGY.
1. What are the mineral substances which chiefly compose the
earth's crust ? What are the elementary substances from
which they are derived 1 What are the methods that have
been suggested as most useful in classifying minerals ?
2. What is the composition of Granite 1 and what are the essential
points of difference between granite and basalt 1
3. Explain the nature of stratification. What do you understand
by the expressions dip and strike of beds 1 Define the terms
conformable and unconformable superposition. How does
cleavage differ from ordinary stratification ?
4. Give some account of the geographical position of the Coal-beds
of India. Mention also the most important Coal-districts in
other parts of the East.
5. Explain the nature and use of Geological maps and sections,
stating the advantage of colours and the general geological
meaning of certain colours ?
6. Under what circumstances may Land springs be expected in a
district ? What are the Geological conditions requisite for
the existence of intermittent springs 1
XIV.
KING'S COLLEGE.
March, 1848.
SCHOLARSHIP EXAMINATION.
1. What are the principal characters of quartz ?
(a) General form of the crystal.
(b) Fracture.
(c) Hardness.
(d) Action of acids.
(e) Action of blowpipe per se.
2. Name some of the substances which quartz will readily
scratch.
3. Name the principal combustible minerals, and any properties
peculiar to them, such as easy fusibility, odour, &c.
EXAMINATION PAPEES. 525
4. What minerals resemble Gold? How is gold distinguished
from such minerals in crystalline form, hardness, or specific
gravity, or when acted upon by the blowpipe or by acids ?
5. What are the chief mineral components of stratified rocks 1
6. How are rocks classified 1 Write down the sequence of fossili-
ferous rocks in England.
7. Under what circumstances may a steady supply of water be
obtained in a gravel district ? What are the Geological con-
ditions favourable for the existence of Artesian wells ?
\ 8. Explain the origin of valleys, viz. :
(1.) Valleys of elevation.
(2.) Fault valleys.
(3.) Valleys of denudation.
XV.
KING'S COLLEGE,
June, 1848.
EXAMINATION IN DESCRIPTIVE GEOLOGY.
1. Explain simply the nature of Geological inquiries and the means
by which Geological facts are determined.
2. How are the materials which compose the earth's crust usually
arranged ? Explain the nature of stratification and the struc-
ture of unstratified rocks.
3. What is cleavage ? Explain the difference between cleavage
and stratification. What is jointed structure ?
4. Describe the characteristic peculiarities and most remarkable
groups of fossils of the Oolitic series of rocks as met with in
England.
5. Write down the complete series of fossiliferous strata as far as
English Geology is concerned, mentioning characteristic spe-
cies or groups of fossils.
6. Where are the chief Tertiary rocks of England found ? What
is the mineral ingredient that chiefly prevails in the Older ter-
tiary rocks of England ?
7. What deposits, or groups of deposits in England are remark-
ably important (1) for building material, (2) for mineral fuel
(3) for salt 1
8. Give a general section across England, from the coast of Suffolk
to the Welch mountains ?
526 APPENDIX.
XVI.
KING'S COLLEGE.
June, 1848.
EXAMINATION IN PRACTICAL GEOLOGY.
1. In what way are soils of various kinds obtained in different
parts of the earth ? Explain the relation between a soil and
the subjacent rock.
2. Explain the advantage of deep draining and the Geological con-
ditions under which it is likely to be useful.
3. Explain the Geological structure upon which depends the exist-
ence of water at moderate depths beneath the earth's surface,
and show when and how far water is capable of being obtained
for the use of man by sinking wells.
4. What are the qualities valuable in Limestones required for
building purposes'? Mention the chief limestones found in
England, their Geological position, peculiarities of structure,
and relative value.
5. In coal-mining explain the action of faulted structure in dam-
ming back water.
6. Explain fully the theory and construction of the Davy Lamp,
and the circumstances under which its use is desirable or neces-
sary ?
7. Show in what way and to what extent the timbering that will
be required in a mine depends on the Geological conditions of
the surrounding and adjacent rocks.
8. Define what is meant by a mineral vein, or lode. What
is the prevailing direction of right-running tin and copper
lodes in Cornwall 1 What is a cross course ?
XVII.
PUTNEY COLLEGE.
July, 1848.
GENERAL EXAMINATION, MINERALOGY AND GEOLOGY.
1. What are the most abundant of the mineral substances which
make up the solid portions of the earth's crust ? Are they
simple or compound bodies 1 Are any of the supposed ele-
mentary substances more widely distributed than others?
Mention the elementary substance most universally present.
EXAMINATION PAPERS. 527
2. What are the relations of form presented in the case of ordi-
nary minerals 1- Explain the nature and limits of those regu-
lar forms called crystals. State how far crystalline action on
a large scale is supposed to affect masses of mineral matter
important from their large dimensions and great abundance.
3. Give examples of minerals in which hardness, colour, odour, and
electricity respectively are known to be characteristic. In
what way may iron pyrites be easily distinguished from cop-
per pyrites ?
4. Explain that peculiarity of structure called cleavage. Explain
the difference between stratification and cleavage, and define
also the expression, jointed structure.
5. Define the following terms used in Geology, viz., dip, strike,
anticlinal axis } dome, fault, valley of elevation, valley of denu-
dation.
6. What are the subdivisions of the stratified rocks in England ?
Explain the nature of fossil organic remains, and the use of
fossils in the identification of rocks.
7. For what mineral substances of economic value are the follow-
ing groups of rocks remarkable in England, viz., the Carboni-
ferous series ; the New red sandstone series; the Oolitic series 1
8. What are the chief facts observed that prove the deposited
rocks to have been exposed to the action of disturbing
forces.
9. How and whence are soils derived? Explain the relation
existing between soils and the subjacent rock.
10. What are the two great subdivisions of mining, and how do
they relate to Geological structure 1 State distinctly the
difference between a stratum, or bed and a mineral vein.
1 1 . Whence are the ores of the following metals chiefly obtained,
viz., copper, tin, lead, zinc, gold, silver 1 Mention the most
common ores of these metals, and the localities in England
where they are chiefly worked ?
12. Under what Geological conditions is it possible to obtain water
from the earth by sinking wells ? What is the essential dif-
ference between land springs, fault springs, and Artesian
springs 1
13. Describe the principal points to be noticed by a Geologist
between Hythe and Folkestone.
14. Draw a rough section of England from east to west, naming
the different strata in the order of their occurrence.
528 APPENDIX.
XVIII.
KING'S COLLEGE.
March, 1849.
SCHOLAKSHIP EXAMINATION MINERALOGY AND GEOLOGY.
] . What are the physical characters of minerals ? Explain the
difference between colour and streak.
2. What minerals represent the scale of hardness ? Are inter-
mediate degrees used ? Give an example.
3. What is the common crystalline form of ftuor spar, and what
different crystalline forms can be obtained from fluor spar by
4. What are the principal characters of calcareous spar ?
a. Primitive form.
b. Fracture.
c. Hardness.
, d. Action of acids.
e. Action of blowpipe.
5. What minerals resemble the diamond, and how can they be
distinguished 1
6. What are the materials of which the great mass of the earth's
crust is made up ? Is there evidence of order in their arrange-
ment 1 and if so, give some proof. Are there found mixed up
with the mineral substances any remains of animals and vege-
tables 1 and if so, mention the usual mineral condition of such
bodies.
7. Are there any marks of mechanical disturbances traceable
amongst the masses of matter which form the greater part of
the earth's crust ? and if there are, mention some of them.
What marks of change of other kinds (not strictly mechanical)
can be traced in the rocks in any part of the British Islands
that you may be familiar with ?
8. Explain the phenomena of springs of various kinds, as depen-
dent on the Geological structure of the district in which they
occur.
9. Mention some of the advantages of Geological knowledge to
the engineer.
10. Prepare an ideal section, illustrating the sequence and position
of the various rocks occurring in England between London
and Brighton.
EXAMINATION PAPERS. 529
XIX.
KING'S COLLEGE.
June, 1849.
EXAMINATION IN DESCRIPTIVE GEOLOGY.
1. Explain the nature and use of Geological map and sections in
illustrating the structure of the earth in a given district.
2. Mention the chief Mineral substances of which the stratified
portion of the earth's crust is made up, and the state of me-
chanical aggregation in which they are usually found.
3. Describe fully the development of the cretaceous series of rocks
in England, and the relations they exhibit to the underlying
and overlying series.
4. Explain and illustrate the use of fossils in Geology.
5. Mention the principal facts concerning the distribution of
basaltic and other volcanic rocks in England.
6. What do you understand by the term metamorphic rocks. Il-
lustrate the phenomena of metamorpliism in the case of common
roofing slate 1
XX.
KING'S COLLEGE.
June, 1849.
EXAMINATION IN PRACTICAL GEOLOGY.
1. Give as complete an account as you are able of the Geological
position, mineral character, economic use and qualities of the
Bath and Portland Oolites.
2. Describe the mineral character and usual position of roofing
Slate, and the mode of working adopted in slate-quarries.
3. Explain the derivation of soils, mentioning the way in which
the depth, texture, and fertility of a soil is dependent on the
parent rock.
4. In coal-mining explain the method of ventilation by splitting
the air, according to the practice in the Newcastle coal-field,
and the extent to which the splitting may be carried.
5. What is the Geological position of the lead and zinc ores com-
monly worked in Great Britain, and state where these ores
chiefly abound.
6. Explain the usual conditions under which Gold is found in
various parts of the world.
7. Describe the nature of surface-drainage and the phenomena of
land-springs.
M M
530 APPENDIX.
XXL
PUTNEY COLLEGE.
July, 1849.
GENERAL EXAMINATION IN MINERALOGY AND GEOLOGY.
1. Describe the general nature of the materials which make up the
, earth's crust. Give the usual names of those which are
most abundant ; their strict natural history definition ; the
proximate and the ultimate elements of which they are
composed.
2. Mention the Metals which are most abundant, the form in
which each is most usually present, the places whence the
ores are chiefly obtained, the nature of the ore most frequently
found in each locality, and the usual yield of each common
ore.
3. Explain the nature of the Diamond, the Ruby, and the Topaz.
Mention the chief physical qualities of each, and the localities
in which each substance is most commonly found.
4. What is understood in Geological language by denudation ?
What is a valley of denudation ? What are the denuding
forces at present acting, and where are their chief results likely
to be found ? What is the difference between denudation ?
and erosion ?
5. Write down the list of deposits which make up the Palceozoic
series, stating the places where each division of the series is
best represented, and the characteristic fossils of each.
G. What portions of the Secondary series of rocks in England are
most important as building material 1
7. Mention the rock from which common Salt is chiefly obtained in
England, and its Geological position. Which of the salts of
lime is usually found with common salt, and in what form does
it usually appear 1
8. What method is adopted in the vicinity of Newcastle-on-Tyne
to obtain the largest quantity of round coal from a deep pair
of pits on a large estate ? Mention the chief contrivances for
ventilation, and the mode commonly adopted to obtain a strong
draught of air.
9. Explain the nature of faults and dykes, and their effect on the
practical working of any bed or vein.
10. In what parts of England are Igneous rocks of a porphyritic
character most abundant 1 What relation exists in England
between the presence of igneous rock of this kind, and the
existence, the direction, and the contents of mineral veins ?
EXAMINATION PAPERS. 531
11. What are the conditions under which Water falling from the
clouds, sinks beneath the earth at one point, and reappears at
a distant point in springs "? Explain also the circumstances
under which Artesian springs may be obtained artificially.
12. Mention some of the theories that have been suggested to ac-
count for the phenomena already distinctly observed with re-
gard to the structure of the earth.
XXII.
H. E. I. C. MILITARY SEMINARY, ADDISCOMBE.
September, 1849.
GENERAL EXAMINATION. MINERALOGY AND GEOLOGY.
1 What is a Volcano 1 Mention some facts proving a connection
between volcanic and earthquake action. Give examples of
volcanic phenomena in districts where there is now no true
volcano. Mention examples of recent alteration of level in
volcanic districts.
2. Mention some instances of aqueous action tending to modify
the existing coast line of England. Explain the nature and
cause of river Deltas.
3. Explain the nature and meaning of Crystalline structure. Give
an example of some crystalline mineral, and mention its dis-
tinguishing character.
4. What are the Minerals used in describing the relative hardness
of minerals 1 Distinguish between the Colour and Streak of
Minerals.
5. How are Rocks made up ? Mention the predominant materials
of rocks. Mention some of the rocks usually described as
igneous, and some of those called metamorphic.
6. Mention the principal divisions of stratified rocks, and the
British subdivisions of the middle part of the middle period.
7. What are/ossi7s, and what is their use in Geology ?
8. Explain the mode in which water is obtained 1. from land
springs, and 2. from Artesian borings.
9. What Minerals are chiefly obtained by mining operations from
beds, and what from mineral veins ? Explain the process of
shading.
APPENDIX II.
GENERAL OUTLINE OF THE GEOLOGY OF INDIA.
THE whole peninsula of India is a great triangular promontory,
terminated in the north by the Himalayan chain, and on the east
and west by the sea. It is connected geologically and physically
with Asia Minor by Beloochistan and southern Persia ; and on the
east it joins the northern extremity of the Burman Empire by the
province of Assam.
India is crossed by the Himalayan range, which forms the northern
boundary of the peninsula. It is also crossed by the Vindhya range,
another east and west chain placed in north latitude between 22
and 23. Between these two ranges is the valley of the Ganges, run-
ning towards the east ; and south of the Vindhya range is the val-
ley of the Nerbudda, which runs towards the west. Besides these
principal ranges there is the great range of the Western Ghauts,
forming a north and south chain on the Malabar coast, and the less
important range of the Eastern Ghauts on the Coromandel coast,
the latter being only separated from the Northern Circars by the
valleys of the Kistna and the Godavery. A number of less import-
ant secondary ranges extend in various directions through the
country, and there are also considerable tracts occupied by lofty
table- land.
India may thus be considered as divided into three portions,
each distinct from the others. The northernmost of these extends
southwards from the great Himalayan chain, and includes the whole
valley of the Ganges ; the central includes the valley of the Nerbudda,
the province of Malwa and the adjoining provinces ; and the south-
ernmost extends from about the twentieth degree north latitude to
Cape Comorin.
The grand feature of Indian Geology is the prevalence of crystal-
line and metamorphic rocks. These appear partly forced up through
the regularly deposited strata, and partly covering them up by broad
sheets that have been poured out in a melted state. They include
granite and many porphyries, and enormous masses of basalt. Be-
sides these are metamorphic rocks in yet greater profusion, gneiss
and mica schist, the former especially, occupying very extensive
tracts.
COAL-FIELDS OF INDIA. 533
The rocks and fossils of the Palaeozoic period would seem nearly
confined to the northern half of the peninsula. Secondary rocks
have been observed at Cutch, and near Pondicherry, and possibly
also exist in various other parts of the country. Their true position
and age have only been made out in the two districts mentioned.
Tertiary rocks abound in India and are probably of various pe-
riods, though many certainly come down to very recent date. The
most remarkable localities for Tertiary fossils at present known are
in the Sewalik range and in the Gulf of Cambay. The vast de-
posits called regur (the cotton soil of India), kunkur, and laterite,
cover a very large part of the district not occupied by the igneous
and metamorphic rocks. The great valleys of India are covered
with extensive and thick masses of alluvial detritus.
COAL DISTRICTS IN NORTHERN AND CENTRAL INDIA.
The coal of India hitherto described is chiefly obtained from the
northern and central portions of the peninsula.
The Himalayan range, which forms a perfect barrier, continuous
with greater or less regularity, separating India from Northern Asia,
is itself chiefly composed of gneissose rocks, highly crystalline, and
penetrated by numerous veins of granite. On the south flanks of
the principal chain there may be traced a well-defined sub-range of
mountains, rising often to a considerable height, and in the western
part distinguished by the name of the Sewalik range. These are of
tertiary origin, and composed of hard sandstones, extremely fossili-
ferous ( 755 758). Then succeed the great plains of India, the
vast alluvial district through which the Ganges runs, and which
near the mouths of that river spread out to an enormous area, re-
ceiving also the waters of the Burhampooter, and forming the joint
delta one of the most remarkable in the world on which Calcutta
and a multitude of important towns are placed.
On the right or south bank of the Ganges, and on the left (also
the south) bank of the Burhampooter, the granitic and gneissose
rocks which are covered up to a considerable distance by the allu-
vial mud of the two great rivers reappear. They form the range of
the Garrow and Caissar mountains, commencing near Silhet and
extending eastwards, and by a number of inferior ranges running at
last into the Vindhya range and passing towards the west.
It appears to be chiefly in hollows or basin-shaped depressions in
these granitic rocks that the coal of northern and central India
exists.
Before proceeding to give an account of the various districts that
have been described as presenting coal, it may be as well first to
allude to the rocks ordinarily associated with it.
534 APPENDIX.
These are limestones, often poor and argillaceous ; sandstones of
various kinds ; clayey and shaly beds, and bands of ironstone. The
coal is in layers of various thickness, sometimes very considerable,
but more frequently poor and unequal.
The limestone is said generally to underlie the coal ; but its thick-
ness is not known nor are there any clear and distinct accounts by
which it can be identified. It is barren of fossils for the most part,
but certainly not always, and careful investigation might discover
some specimens which would be useful in determining its age, and
identifying distant beds.
The coal and shale appear to be associated much as in the other
coal-districts, and there can be no doubt that the shale contains
fossils. It is of the greatest importance that these should be for-
warded to England for examination and comparison.
The shale appears to become gritty in its upper members and
, passes into a gritty micaceous brownish-grey sandstone, sometimes
becoming flaggy. This sandstone is said to form the surface rock
generally in the coal-districts, and to be presented in low round-
topped hills and undulated ground.
The coal that has been found of the greatest value in point of
quality in India is considered to be that lowest in position ; and
the varieties occurring east of Bengal in Assam is said to be better
than that met with in the western district. The Silhet and Ner-
budda are accounted the best of all, and according to present ap-
pearances will prove the most available and lasting sources of supply.
The coal-districts of India may be considered as five in number,
three in Northern India and one in Cutch, while the fifth includes
the province of Arracan and the coast of the Burman Empire near
Tenasserim. Of these the Cutch coal is certainly not of the car-
boniferous epoch, and it appears to be of little importance at present
and unpromising.
The whole district, extending from the neighbourhood of Hoosun-
gabad on the Nerbudda river (lat. 23 N. long. 78 E.), on the left or
south bank of the river, and extending in a north-easterly direction
for a distance of about 400 miles to Palamow, thence eastward for
250 miles to Burdwan, near Calcutta, and running northward for 150
miles to Rajmahal, exhibits, it would appear, at intervals by no
means distant, a continually repeated outcrop of rocks, consisting of
sandstones and shales, with occasional limestone. Throughout this
wide tract a number of beds of coal have been recognised, of variable
thickness and value, but all appearing to exhibit evidence of the
existence there of a great coal-district.
On the flanks of the Garrow Mountains near the Burhampooter,
and on both banks of that vast river, we find another, perhaps a con-
tinued outcrop of similar beds, also containing coal, and reaching in
COAL-FIELDS OF INDIA. 535
a north-easterly direction for nearly 400 miles. The intermediate
plains, whose breadth between Rajmahal and Jumalpore is about
100 miles, are chiefly alluvial, and thus it is possible that there
exists a vast range of carboniferous strata, reaching for upwards of
1000 miles along the flanks of the Himalaya mountains, the dis-
tance from the mountain chain gradually increasing as we advance
westward, the mountains trending northwards and the outcrop of the
carboniferous bed southwards, until finally, the distance between them
being upwards of 500 miles, the relation is not easily recognised.
I. Commencing with the neighbourhood of Calcutta, we have first
to consider the Burdwan coal-district, with which may be grouped the
Adji and the Rajmahal fields, all these being on the banks of either
the Hooghley or Ganges, or on the tributaries of these rivers. The
Burdwan district has been long known, and a good deal worked.
The workable beds of coal are nine and seven feet thick respectively.
They are associated with sandstone, shale, and a little clay-ironstone,
and about six other thinner seams of coal, while other thick beds are
mentioned, but their real existence as separate beds is doubtful.
(See 943.) There are thirteen spots at which this coal is mined,
but most of them are surface workings. The deepest sinking is 190
feet. The distance to Calcutta is about 90 miles, but the actual
transit of coal is nearly 200 miles. There would seem to be a con-
tinuous outcrop of the same kind of rocks from Burdwan up the
Adji river, and northwards to Rajmahal. On the Adji river the
coal has been worked in more than one spot, and is found to be of
about the same quality as that of Burdwan ; but neither of them is
considered of nearly so good quality as the English coal. Further
on, at Rajmahal, coal is known to exist, but has not yet been much
worked. The quality of that which has been obtained does not
appear good.
II. The Burdwan coal-field appears to be directly connected with
a district at Palamow, in which coal has been worked in no fewer
than four places. The coal here apparently reposes in a valley en-
closed by hills of granite, and is associated with a good deal of iron.
There are several beds that are of workable size, but a good deal of
the coal is heavy and of inferior quality, and some of it appears to
be anthracitic. These coal-beds are not far from the Soane river,
and about 100 miles from its confluence with the Ganges a little
above Dinapoor and Patna ; but the Soane is not at present navi-
gable. To the west of Palamow the carboniferous beds are described
as appearing along two irregular lines, the one towards the south-
west for 150 miles, reaching beyond Koorbah, and the other more
westward, by Sohagepoor, to the Nerbudda. These beds appear to
connect themselves with the Burdwan coal-field ; and near Ramurgh
coal has been obtained in two or three places. This coal is said to
536 APPENDIX.
be of very good quality, and the seam is of very considerable thick-
ness. Westwards, again, from Palamow, and at a distance of about
50 miles, coal has been found in several places in Singrowli, but the
beds at present known are thin ; and again, to the south-west, the
same mineral occurs at Sirgoojah, where fine coal has been seen, but
is not used at present. Between the Singrowli coal and Jubbul-
pore excellent coal has been found in several places, indicating an
extensive coal-field ; but the nature and thickness of the beds are not
stated.
The Nerbudda district, although from the drainage of the country
it belongs to the Bombay side of India, is manifestly more related, so
far as the old rocks are concerned, to the Bengal territory. The
coal is about 350 miles from Bombay, and the Nerbudda river is at
present not navigable. There seem to be three districts in the Ner-
budda valley in which coal is found, but the most important of them
is that near Gurrawarra, about midway between Hoosungabad and
Jubbulpore. The coal here, indeed, appears to be perhaps the best
hitherto found in India, and exists in beds three in number, whose
thickness respectively is said to be 20 feet, 40 feet, and 25| feet.
There are also other beds, one of which is four feet.
The discovery of this, the Benar coal-field, promises to be of great
importance. It is also very near another basin, where there are beds
also of excellent quality, one of them six feet in thickness. At Jub-
bulpore itself coal has been found at a depth of 70 feet, one bed
being nearly twelve feet thick.
III. Let us consider now the district east of Calcutta. We there
find true carboniferous rocks on both flanks of the Garrow moun-
tains, commencing near Jumalpore, and thence continuing north-
eastwards, for a distance amounting on the whole to nearly 400 miles,
through Lower and Upper Assam. The district nearest Calcutta is
Silhet, on the south flanks of the Garrow, where eleven beds of coal
have been determined, whose total thickness as already ascertained
amounts to 85 feet. This coal is of excellent quality, and can as
readily be conveyed to the Upper Ganges as the Burdwan coal. The
most remarkable beds occur at Cherra Ponji ; but these appear irre-
gular, although they are undoubtedly of great thickness in several
spots, amounting sometimes to nearly 30 feet. There are also other
important beds. They have been known for more than ten years,
but have not been worked ; and since their first discovery large
quantities of iron have been smelted with charcoal.
After passing the districts in which the coal has been thus clearly
exhibited, we proceed next to the Assam districts, also more or less
continuous, and extending for about 350 miles chiefly along the
south side of the Burhampooter \ the whole being divided into the two
groups of Lower and Upper Assam, separated at Bishenath, 170 miles
COAL-FIELDS OF INDIA. 537
above Calcutta. Six coal-fields are enumerated in the Upper dis-
trict, and three in the Lower ; but the latter, although it would
seem not so promising, are looked on as scarcely less important in
consequence of their greater accessibility.
So far as details are concerned, the Lower Assam coal offers little
positive information ; the indications consisting rather of rolled frag-
ments drifted, than of distinct and well-marked beds. It is called
lignite in a report from Lieut. Vetch ; but both coal and lignite are
terms frequently used without reference to any peculiar character of
the mineral, or any geological position. Similar beds of coal or lig-
nite to those found in Lower Assam, south of the Burhampooter, are
also mentioned as occurring on the north in three of the streams
flowing into that river from the Bootan range. The Upper Assam
coal is manifestly of great interest, and likely to prove very impor-
tant. It is associated with abundance of clay ironstone.
About 80 miles above Bishenath, other beds, stated to be 6 feet
thick, have been worked for the sake of trying the economic value
of the coal. It is described by the commander of one of the Assam
Company's steamers, in a letter dated 24th January, 1845, as far the
best he ever had on board a steamer, and far superior to any coal in
Calcutta. From the growing importance of the tea-trade from
Assam, this is likely, therefore, to be of great value. Still further
up the country there are several important beds, dipping, it would
appear, at so high an angle, and placed so unfavourably with regard
to present means of transport, that it would be difficult to work
them. The other beds that appear in this district are exposed to the
same difficulty ; and the coal throughout Northern India appears to
be in this respect unfavourably placed.
Passing on now to the other districts in India and the East, in
which carboniferous rocks and beds of coal have been met with,
we have to consider two, the Tennaserim and the Arracan districts,
which, from their vicinity to India and their geographical position,
are of very marked importance. The former has been known for some
years, and there are said to be four localities at which coal appears ;
but of these only one seems likely to prove of economic value. From
the accounts given of this coal there is every reason to conclude, that
one of the beds is not of the carboniferous period ; and although
another (on the Thian Khan) has been the subject of a far more fa-
vourable report, being called cannel coal, and stated by Mr. Prinsep
to be an admirable coal for gas, there is yet much probability of the
whole being of the tertiary period. These beds have been described
in the "Journal of the Asiatic Society" for 1838.
In Arracan there are 1 1 beds of coal, but all of them are thin, and
their position nearly vertical. They are said to be associated with
sandstones, limestones, and shales ; but it is clear that they can at
538 APPENDIX.
present be looked at only as indications, and not of any practical
importance.
Such is a general account of the coal-districts of .India, so far as
evidence can be obtained from the report of the committee for the in-
vestigation of the coal and mineral resources of India for May, 1845.
The true age of these beds is a matter of great interest, but un-
fortunately the evidence is imperfect in a most important point. The
beds of coal, occurring chiefly in granitic basins, and often detached,
may be, and some of them most likely are, of the Devonian or.
Carboniferous age ; they may, however, be Oolitic, like the imper-
fect coal of Cutch and of some parts of our own country, or they may
be tertiary lignites. Now it may seem of little importance to the
mere surveyor what the geological position of these beds may be,
provided there is the material he needs ; but experience renders it
probable that on the mere question of age does, in fact, depend much
of their true economic value. Could it be satisfactorily shown that
throughout the wide district of Northern India there is a true out-
crop of carboniferous beds such as occur in England, in America,
and even in Eastern Australia the value of a very large part of the
possessions of England in the East might be considered much in-
creased ; for if the beds should prove steady and permanent, the
application of the resources in knowledge and wealth of a rich and
an enterprising people, would very soon bring into operation, in all
those districts, manufactures and commerce on the grandest scale.
The navigation of the rivers, the . state of the roads, the means of
communication by railroads, would be immediately established or
permanently improved ; and the result must be improvement in the
condition of the country.
The result of the inquiry already made being incomplete, it must
be considered unsatisfactory, though no doubt highly suggestive for
future investigation. Little value can be attached to mere statements
of the existence of carbonaceous, matter in beds, because many of the
important practical conditions are independent of the appearance
and experiments on detached fragments, and are learned only when
such an amount of detail is given with regard to the geological con-
ditions under which the coal appears, that we may fairly judge of the
probable extent of the deposit.
A series of observations, then, connecting any .of these apparently
detached deposits by uniformity of association, or still more by an
identity in the species of fossils obtained from them, would be of the
greatest practical benefit, and would assist in enabling us to form
sound conclusions with regard to their value. To make such obser-
vations should be the object of every one who has the opportunity of
travelling across Northern India. It will be long before a matter
which involves so much detailed personal investigation, and . the
COAL-FIELDS OF INDIA,
539
grouping together of so many facts, is fully accomplished ; but mean-
while every accurate observation of dip and strike ; every section
across a district.; every map, however rough, of one of the detached
basins ; every specimen of fossil which will give only a few leaves of
ferns or characteristic portions of a shell, will be a step in advance,
and will bring us nearer the time when we shall have a clear and
distinct idea of the true mineral riches in India in this important
respect.
Table
the position and quality of the most important
Coal-fields of India.
j
Inalysi
\,
Province.
.-
District.
Beds.
Quality.
i
J
II
I. Bengal. .
Burdwan . .
Several, 9 & 7 ft
Good
36
60
A
2. Lower Assam
3. Silhet
Adji-river..
Rajmahal . .
Kurribari . .
Garrow-hills
6 to 13^ feet.
Not worked.
Not traced ....
Undefined ....
Like Burdwan . .
Brown coal . . /
Excellent
50
70
34
40-6
25-4
65'4
9'4
4-6
l.K
Cherra Ponji
Several 2 to 28 ft
Slaty
36
41'0
4. Upper Assam
Namsong
6 feet
Very good.
Suffry .. .
Boorhath .
Jeypore
Up to 12 yards..
6 to 8 feet
2 to 9 feet
Caking coal ....
Superior
45
48
52-7
46*2
2-3
,5. Behar
Namroop
Kosiah hills
Palamow . .
Up to 20 feet.
Undescribed ....
Several beds to ^
6 feet> '. f
Very few ashes
c Slate coal
\ Slaty crop ....
38-5
44
32
60-7
50
58
o 05 o c
CO C
-
6. Central dis- 1
Ramgurh . .
3 feet . . .
* Ditto ditto ....
Promising ....-[
25
31
6' 3
53
12
16
tricts .. *
Ruttenpore
r Immense thick-
27
b'l
12
Su'rgooja . .
Singrowlie
Many yards ....
Thin
Fine
Middling '......
54
32-2
13'8
Sohajepore
Not described*
Up to 40 feet
Excellent
Valley.. /
Shawpore . .
Jubbulpore
2 to 6 feet.
Undescribed ....
Excellent .
50
47*1
00
R T
Mergue. . . .
About 6 feet
55
40
5"
9. Arracan ....
Ramree ....
Cheduba
Thin seams ....
Thin seams . . {
Caking coal ....
Inferior Cannel-i
coal . /
36
46-8
49
41-2
15
12
10. Guzerat ....
Cutch
Many thin seams.
Doubtful ....
1 1 . Borneo ....
Labuan . /
Several beds up i
Good
to 12 feet .. /
540 APPENDIX.
In the following Notes some information is given of the more
remarkable facts with regard to each district.
1. Burdwan Coal. Although this coal-field has been known for
thirty years there is yet much to be learned, not merely of its rela-
tion with other neighbouring coal-fields, but even of the geological
age of the coal and associated beds, and the probable extent and
value of the deposit.
As many as thirteen collieries are described as having been under-
taken. The supply seems increasing. It seems however quite clear
that without railway communication there will always be difficulties
and expenses in the transit, greatly interfering with the development
of the mineral wealth of this district, whatever it may be. The
association of the beds here does not seem to differ greatly from that
in the Assam districts, but as the sinkings are deeper there is greater
regularity and uniformity in the arrangement.
Adji River. An extensive area on both sides the banks of this
river is occupied by the coal-field. It is not quite equal to the Burd-
wan, but is more readily available. It requires careful working out
to connect it with the adjacent similar deposits.
Rajmahal. The coal hitherto obtained and experimented on
from these mines is considered very inferior in quality.
2. Kurribari. The brown coal here is apparently in small basins j
it is of inferior value, and its thickness is not considerable. It must
not be confounded with the bituminous coal in the neighbourhood.
There seems to be a considerable quantity of drifted coal in the
rivers, and the tracing of this to its source might perhaps lead to
useful results.
3. Silhet. This coal is described as being of excellent quality and
is even better situated for supplying some parts of the Ganges than
the Burdwan field. By far the most remarkable of the different lo-
calities in this province is that of Cherra Ponji, situated on a table-
land composed of horizontal beds of sandstone rising abruptly from
3000 to 4000 feet above the plains of Silhet. The beds of coal are
seen in precipices thirty or forty feet high, consisting of coal, lime-
stone and shale. The thickness of the coal is very variable, from
two feet eight inches to twenty-eight feet. The lowest bed described
is a compact dark bluish or blackish-grey limestone, containing fos-
sils ; this is covered by a few thin beds of dull dark-coloured gritty
limestone, which are succeeded by thin beds of sandstone, and these
by beds of blackish shale, upon which the coal reposes. Above the
coal are usually a few beds of soft sandstone, loose sharp sand, and clay.
These rocks are considered to be the lower beds of the coal formation.
Specimens of the fossils from the limestone would be of great interest.
The manufacture of iron is carried on in the neighbourhood to
great extent, but charcoal alone is used as fuel.
COAL-FIELDS OF INDIA. 541
It appears not unlikely that the Cherra beds of coal are very local
in every respect. The quality of the coal is said to be excellent.
4. Upper Assam. On the Suffry, at one spot, the dip is de-
scribed as about 40. Limestone probably underlies the coal ; the
upper bed of coal is six feet high (thick 1), with clay roof. The
quality of this coal is said to be excellent ; the thickness is certainly
considerable and the beds seem workable, but at present communica-
tion with Calcutta is difficult. Abundance of clay ironstone is
found with the coal. The coal has been tried in steamers.
5. Behar. The valley of Palamow in this province contains im-
portant beds of coal, but they are not at present readily available
for want of means of communication. The quality is described as
good and bituminous. The coal occurs in shale and sandstone with
ironstone and is in the immediate neighbourhood of granite. Fossils
occur in the shales, but they are not described.
These beds promise to be of great importance, being situated in
very favourable lines of communication. The coal also is of good
quality, and the habits of the people favourable to its use.
6. Ramgurh. The beds are of moderate thickness, and the coal
resembles that of Burdwan.
Ruttenpore. The thickness of the coal here is described as amount-
ing to 200 yards. It is laid open by the side of the river Hutsoo.
There is no evidence to show how far this account, deduced from a
sketch by Col. Ouseley, may be correct. The quality of the coal is
described as good, and the beds associated include a black marble.
It would be interesting to obtain further information concerning this
bed, which is situated not far from the sources of the Nerbudda.
Suryooja The coal here is simply described as of good quality
and abundant. There are two localities named, one of them on the
Kehar river, said to be easily accessible.
Singrowlie. This locality is on the table-land at the head of the
Soane, 50 miles west of Palamow. There are several beds ; most of
them, as at present described, appear to be very thin.
Sohajepore. This is between Singrowlie and Jubbulpore, and con-
ducts us to the Nerbudda fields. There are several places referred to
as exhibiting coal and associated shales and ironstone, but there is
much uncertainty in the accounts.
7. This district (the Nerbudda Valley) is of great importance,
since the supply for Bombay must be derived hence. It is of the
greatest importance that the true value of the coal-fields should be
clearly and distinctly made out.
Gurrawarra. Seventy miles above Hoosungabad. This is said to
be the most important coal in the district, and even, according to Col.
Ouseley, in India. Occurring near Benar, it may be called the Benar
coal-field. On the Seeta Rewar river there appear to be three beds,
542 APPENDIX.
whose thickness is 20, 40 and 25J feet respectively; these are covered
with a thin bed of sandstone, and repose on and amongst quartz sand-
stones. The important inquiry in this case would be the probable
extent of the bed. The quality is said to be superior to imported
Scotch coal. There is limestone and iron in the neighbourhood.
As this spot is in the line of one of the projected railways, it be-
comes of very great importance that its true value should be deter-
mined as speedily and as certainly as possible. At present there
appears to be no information with regard to the dip or the probable
superficial limits of the outcrop.
Shawpore. This is the Baitool district, and is situated at Hoo-
sungabad, 30 or 40 miles from the Nerbudda, without convenient
means of transport ; the beds are said to be numerous, extensive and
near the surface. No account is given of limestone.
Jubbulpore. There is said to be much very excellent coal from
this neighbourhood. At nine miles from the station there is a large
bed of first-rate quality, many yards thick, crossing the bed of the
Soane ; and in the station itself, at the depth of 70 feet, coal is also
met with.
8. There are four coal-fields in the Tenasserim provinces. The
quality in one appears anthracitic, in another highly bituminous.
Considerable expense has been incurred in this district, but appa-
rently without any favourable result.
9. There are many indications of coal in Arracan, but the beds are
all so nearly vertical that it seems unlikely they can be worked with
profit. They are associated with limestones, sandstones, and shales,
and are considered very good in point of quality. The limestones
are fossiliferous, but the fossils are not described.
10. The two thin seams of coal at Bhooj in Cutch belong to the
Oolitic period. They have been worked at considerable cost, but do
not promise much chance of success.
11. The island of Borneo appears to contain very extensive and
valuable deposits of coal coming out to the surface near some parts
of the coast. The small island of Labuan, near Borneo, also pre-
sents very large and valuable resources, several seams of coal having
been described highly inclined and disturbed, but of tolerably good
quality. The following analysis of specimens forwarded to the Ad-
miralty is taken from the anniversary address of Sir H. T. de
la Beche, to the Geological Society, in 1848. The specimens were
obtained from the crop of the bed, and are, probably, not equal in
quality to the mass. The Labuan coal is from a nine foot bed,
which has been traced four miles and a half in a WSW. direction,
dipping about 24 to SSE., and reposes on a clay-bed. The Kiangi
specimens were from the main land of Borneo. An ample supply
appears to be obtainable from either locality.
GEOLOGY OF SOUTHERN INDIA. 543
Labuan. Kiangi.
lift. bed. 3ft. bed.
Carbon 64'52 70'30 54-31
Oxygen 2075 20'38 25-23
Hydrogen 474 5'41 5'03
Nitrogen 0'80 0'67 0'98
Sulphur 1'45
Ash 774 3-24 14-45
ACCOUNT OF THE GEOLOGY OF SOUTHERN INDIA.
This part of the peninsula presents two mountain ranges, known
as the Eastern and Western Ghauts, and the intervening table-lands
have an elevation varying from 500 to 3,000 feet above the sea. A
tract varying from one to seventy miles in breadth extends at the
foot of these ghauts between the hills and the sea. The mean eleva-
tion of the Western Ghauts is about 4,000 feet, and of the Eastern,
1,500 feet.
Almost the whole of Southern India is occupied by crystalline
and metamorphic rocks, the latter constituting by far the larger
part. They are for the most part schistose beds penetrated and
broken up by crystalline masses, and are partially capped and fringed
on the Western side by laterite, and on the Eastern by sandstone,
limestone, and laterite. The sequence of metamorphic rocks is not
invariable, but gneiss is described as usually lowest, and next to it
occur mica and hornblende schists, actinolite, chlorite, talcose and
argillaceous schist and crystalline limestone. The strata are often
violently contorted, and not inclined with any regular dip.
The beds overlying the metamorphic rocks consist of various argil-
laceous, arenaceous and siliceous schists, in which no fossils have yet
been found, and whose age is uncertain. The limestones are consi-
dered to be generally lowest, and after them come calcareous shales,
argillaceous shales and slates, and then sandstones and conglomerates,
the latter containing diamonds. This diamond rock is considered
by Capt. Newbold as of Palaeozoic age, and certainly appears very
ancient. An account of the working of diamonds from diamond
gravel, is inserted in a previous chapter ( 775). The diamond sand-
stone is described as not very dissimilar to some Devonian rocks of
England.*
The only Secondary deposits in Southern India appear to be the
lower cretaceous fossiliferous limestones of Pondicherry and Trichi-
nopoly : these have been already alluded to.
The Tertiaries of this district, of most importance, are those called
laterite, regur, and kunkur. The latter two have been described, but
the laterite now requires notice.
* See Summary of the Geology of Southern India. Journal of the Royal Asiatic Society, vols.
via. ix. and xii.
544 APPENDIX.
Laterite varies much in colour and composition, but generally pre-
sents a reddish brown or brick-coloured cellular clay, more or less
indurated and used by the natives as bricks when cut square, whence
its name Laterites, or brick-stone. It often passes into a hard com-
pact jaspideous reckon the one hand, or into loosely aggregated grits
or sandstones on the other. It is also, sometimes, a red or yellow
ochre or lithomarge, and occasionally becomes a conglomerate con-
taining fragments of quartz and crystalline rock embedded in ferru-
ginous clay. The cavities or cells are occasionally empty, but some-
times filled by various substances. The iron prevails to such an
extent as to constitute some portions of a true ore of that metal. It
hardens greatly and permanently on exposure, and is well adapted
for buildings and fortifications. Many extensive caverns occur in
the rock. Laterite has been supposed to be weathered igneous rock,
but this is not probable : it is, however, of aqueous origin, and of
older date than the regur and kunkur which it underlies.
The crystalline rocks of Southern India are considered by Capt.
Newbold to be of several ages, and there are, at least, three distinct
varieties, consisting of granites, basaltic greenstone, and overlying
traps or recent basalt. The granites include two principal varie-
ties, dykes of the one intersecting the other. The basaltic green-
stone penetrates all rocks older than the laterite, and the overlying
trap or basalt, which is yet more modern, covers a vast extent of sur-
face, and conceals a large amount of rocks of different origin.
The following scheme of the stratified rocks of Southern India,
taken from Capt. Newbold's paper in the Journal of the Asiatic So-
ciety, already quoted, will properly conclude this notice. The views
may possibly admit of modification in some matters of nomenclature.
TERTIARY ROCKS. CORRESPONDING EUROPEAN PERIODS.
1 . Sandstone of Coromandel, and Paumbum, and > R
Cape Comorin, with recent sea-shells.
2. Coromandel black clay, underlying Madras...
3. Ancient Kunkur and gravel, with remains of ? Newer Tertiary.
Mastodon '
4. Silicified wood-deposit of Pondicherry, and \ j^j^jg Tertiary
older Laterite * ' ^'
5. Freshwater limestone of Nirmul, Hydrabad, > Q^J Tertiar T
and Rajahmundry * ' ^*
SECONDARY ROCKS.
6. Limestone beds of Trichinopoly,Verdachellum, i Lower Cretaceous.
and Pondicherry '
PALEOZOIC ROCKS.
7. Diamond sandstone \
8. Limestone f Carboniferous, or Devonian.
9. Lower diamond sandstone '
GLOSSARY OF SCIENTIFIC TERMS.
ABRASION. The removal of particles by rubbing.
ABSORBENT. Capable of sucking up fluids. Thus chalk is said to be absorbent of
water.
ACCLIMATIZE. To accustom to a climate different from that which is natural :
applied both to plants and animals.
ACCRETION. Increase of size or growth by the mechanical addition of new particles.
ACICULAR. Needle-shaped.
ACIDULOUS. Slightly acid.
ACLINIC LINE. The magnetic equator. See 31.
ADHESION. See 18.
ADIT. The name given in mining to an underground horizontal gallery or tunnel used
in carrying water out of a mine to the lowest convenient level ( 1151).
AEROLITES. Stones which appear to have fallen from the higher parts of the atmo-
sphere. They are sometimes called Meteorites. See 449.
AFFINITY (in Chemistry). The tendency of various substances to combine. See $ 21.
AFFINITY (in Zoology and Botany). The condition of similarity in essential characters,
and not merely by similarity of form or use, as in analogy.
AFTER -DAMP. The gas (carbonic acid gas) produced in mines after an explosion of
fire-damp.
AIGUILLE (a needle). Used in ; Physical Geography to designate the peaks of mountains.
ALBUM-GR^CUM. The name given to the calcareous excrement of some of the car-
nivora.
ALGJE. A division of plants including the common sea- weeds.
ALKALI (in Chemistry). That which in combination with an acid produces a neu-
tral salt.
ALLOTROPY. See $ 291.
ALLUVIUM. Earth, sand, gravel, stones, and other substances transported by water,
and not permanently buried beneath the waters of lakes and seas. The adjective
alluvial is often used. Alluvion is a synonym.
ALUMINOUS. Containing alumina, or rather silicate of alumina, which is the base of
pure clay. Thus, aluminous means clayey. The word is, however, sometimes
used in the sense of containing alum, a sulphate of alumina and potash.
ALVEOLUS. Literally a socket, or small cavity or cell. Used in Palaeontology to
signify the chamber of a belemnite.
AMALGAM. A compound of any metal with mercury.
N N
546 GLOSSARY OF TERMS.
AMMONITE. A fossil genus of many-chambered shells allied to the Nautilus, named
from their resemblance to the horns on the statues of Jupiter Ammon.
AMORPHOUS. Without regular form.
AMORPHOZOA. Animals without definite form sponges.
AMYGDALOID, Almond-shaped. Any rock is called by this name which contains
rounded or elongated minerals embedded in some simple mineral or base.
ANALOGY. A relation of resemblance as distinguished from that of affinity. See Affi-
nity. An analogue is a body that corresponds with and represents another, as a
fossil species frequently does a recent one.
ANALYSIS (in Chemistry). The separation of a substance into its component elements.
ANEMOMETER. An instrument for measuring the force and velocity of the wind.
ANGLE. The inclination of two lines, or more than two planes, meeting at a point;
or the inclination between two planes. See Solid angle.
ANHYDROUS. Without water. Simple minerals, not containing water as an ingre-
dient, are called anhydrous.
ANIMALCULES. The name given in Zoology to exceedingly small animals which
cannot be studied without the assistance of the microscope.
ANOMALY. An exception to a law.
ANOPLOTHERIUM. The name given to a characteristic genus of a group of extinct
quadrupeds found fossil in the older Tertiary deposits, and nearly allied to the tapir
and pig. The Palaeotherium is another genus also characteristic and nearly allied.
ANTAGONIST FORCES. Two powers in nature, one counteracting the other and pre-
serving a general equilibrium in appearance on the earth's surface.
ANTARCTIC. Opposite the Arctic. The name given to the southern as distinguished
from the northern or arctic region of the earth.
ANTEDILUVIAN. Before the deluge a term generally employed in reference to
periods of great but indefinite antiquity.
ANTHRACITE. A kind of coal. See 353.
ANTICLINAL. Or ^Anticlinal axis. A saddle-shaped position of rocks, the result of
disturbance. See CIO.
ANTIPODES. The inhabitants of that district of the earth diametrically opposite to the
one in which the person using the term may happen to be at the time or may refer to.
AQUA-FORTIS. Nitric acid.
AQUA-REGIA. A mixture of nitric and muriatic acids capable of dissolving gold.
AQUEOUS. That which is dependent on water. Aqueous rocks are those produced
by deposit from water.
ARCHIPELAGO (in Geography). An important sea containing numerous islands.
ARCTIC. Northern. Thus we speak of the Arctic circle, the Arctic pole, &c.
AREA. A space. Any limited district is sometimes called an area.
ARENACEOUS. Sandy.
ARGENTIFEROUS. Containing silver.
ARGILLACEOUS. Clayey.
ARTESIAN SPRINGS AND WELLS. See 1049.
ARTICULATA. A natural division of animals, having their limbs articulated or
jointed together, like the lobster.
GLOSSARY OF TERMS. 547
ASHLER. The name given to freestone when squared for building purposes.
ASSAY. The determination of the quantity of a metal contained in a metalliferous ore.
ATMOSPHERE. The whole body of the air floating above the solid and fluid matter on
the earth.
ATOLL. A coral island of a ring-shape, consisting of a circular strip of coral surround-
ing a central lake of salt water.
ATOM. The name given to the ideal ultimate particles of elementary bodies.
ATTRACTION. The force which tends to bring one mass of matter in contact with
another. See 1 6.
AURIFEROUS. Containing gold.
AURORA. An appearance of light in the heavens, probably connected with the
disturbance of magnetic equilibrium. When proceeding from the neighbourhood
of the North Pole it is called aurora borealis, when from the south, the aurora
australis.
AVALANCHE. A mass of snow detached from great heights in many lofty mountain
districts, and falling into valleys below, causing great destruction.
Axis. See Anticlinal and Synclinal Axis.
AZOTE. Nitrogen gas.
BACULITE. A straight, many-chambered shell, somewhat resembling an ammonite
unwound.
BAROMETER. An instrument for measuring the weight or pressure of the air by com-
paring it with that of a column of mercury or water. The Aneroid barometer is a
modification. See 87.
BARRIER-REEF. A. reef or bank of coral parallel and forming a barrier to an island
or coast-line, and at some distance from the coast.
BASALT. An igneous rock, often columnar and supposed to be ancient volcanic lava.
It is the most common of the group called Trap-rocks.
BASIN (in Physical Geography). An area of drainage including the whole space
drained by a river and all its tributaries.
BASIN (in Geology). The name applied when deposits lie in a hollow or trough, like
the bed of a lake.
BASSETT. See Outcrop of strata.
BEACH. The shore of the sea.
BKD or STRATUM. A layer of material the whole of which exhibits some common
character. A bed may or may not exhibit stratification or lamination.
BELEMNITE. A dart-shaped shell, probably the ancient representative of some of our
cuttle-fish. The shell is conical and chambered.
BEVELMENT (in Crystallography). See $ 253.
BIND. The name given in mining to argillaceous or clayey shale. It is a bed often
associated with coal.
BLUFF. A high bank presenting a precipitous front to the sea or a river.
BOTRYOIDAL (in Mineralogy). Clustered like a bunch of grapes.
BOULDERS. Large rounded or angular blocks of stone, unlike the underlying rocks,
embedded in loose soil or gravel, and brought from a distance.
548 GLOSSARY OF TERMS.
BR ACHIOPODA. A group of shell-bearing animals having two long spiral arms serving
to assist in locomotion and for other purposes.
BRECCIA. A rock made up of angular fragments of various materials cemented together
by lime or other substance.
BROWN-COAL. Tertiary coal or lignite only partially mineralised.
BUFONITE. A name sometimes given to the teeth and palatal bones of some fishes
found fossil.
BUHR-STONE. A siliceous rock full of cavities, found in America, and used as a mill-
stone. Sometimes spelt Burr-stone.
BYSSUS. A tuft of hairs or beard attached to certain bivalve shells, and fastening the
animal to a rock.
CAIRNGORUM. A variety of quartz crystal.
CALAMINE. The common ore of zinc.
CALAMITE. A fossil from the coal-measures resembling a gigantic reed (calamos).
CALC SINTER. The calcareous deposit from springs holding carbonate of lime in solution.
CALCAIRE GROSSIER. A coarse limestone of the Older Tertiary period, found in the
Paris basin.
CALCAIRE SILICEUX. A compact siliceous limestone sometimes replacing the calcaire
grossier.
CALCAREOUS. Containing lime.
CALCINE. To burn to a calx or friable earthy residuum.
CALP. An impure limestone belonging to the Carboniferous and Devonian series.
CAMBRIAN. Belonging to Wales. The " Cambrian system " in Geology, is a name
suggested by Professor Sedgwick, to designate part of the Silurian series of North
Wales.
CANNEL COAL. A compact clean coal burning freely like a candle. It greatly
resembles jet.
CAPILLARY. Hair-like.
CARAPACE. The upper shell of reptiles.
CARBONIFEROUS. Containing carbon. The " Carboniferous system" in Geology is
that which contains the coal-measures and the carboniferous or mountain limestone.
CARNIVOROUS. Flesh-eating. The " Carnivora " in Zoology consist of a group of
animals eminently carnivorous.
CATARACT. A waterfall.
CAUDAL. Connected with the tail.
CEMENT. The matter by which two solids are made to adhere.
CEPHALOPODA. A group of animals of which the Nautilus and Cuttle-fish are ex-
amples, having the locomotive apparatus immediate over the head and stomach.
CETACEANS. The whale tribe.
CHALYBEATE. Water holding iron in solution.
CHAMBERED. The term applied to those shells regularly divided by natural equidis-
tant partitions. Many-chambered or multilocular is a name given to the group of
shells inhabited by the cephalopoda.
CHERT. A siliceous mineral, resembling common flint, but of coarser texture.
GLOSSARY OF TERMS. 549
CHOKE-DAMP. The name given to the carbonic acid gas found in wells and mines.
CILIATED. Fringed with very short hair-like appendages.
CLAY. An impure, unctuous and tenacious earth.
CLEAVAGE (in Mineralogy). See 249.
CLEAVAGE (in Geology). See 597.
CLIMATE. See 104.
CLINOMETER. An instrument for measuring the dip and determining the strike of
beds or strata.
CLUNCH. The hard beds of the lower chalk.
COAL-MEASURES. The whole group of deposits, consisting chiefly of sands and shales,
with which coal is usually found.
COBBLE. A pebble.
COHESION. A force of attraction acting only at very small distances, and when sub-
stances are apparently in actual contact. See $ 18.
COLUMNAR. Arranged in columns.
COMBINATION, CHEMICAL. See $ 19.
CONCHOIDAL. Resembling a shell. Used in Mineralogy to designate a particular
kind of fracture. See 305.
CONCHOLOGY. The study of shells.
CONFLUENCE. The point of junction where two streams meet.
CONFORMABLE. When the planes of bedding of two successive beds or strata are
parallel to each other they are said to be conformable ; when not parallel they
are unconformable. See 607.
CONGENERS. Species belonging to the same genus.
CONGLOMERATE or PUDDINGSTONE. A rock made up of rounded water-worn frag-
ments of rock or pebbles cemented together by another mineral substance.
CONTEMPORANEOUS. Formed at the same time.
COOMBE. A hollow unwatered valley on the declivity of a hill.
COPROLITE. The fossil remains of excrement.
CORNU AMMONIS. See Ammonite.
COSMICAL. Relating to the universe.
COSMOGONY. The word formerly applied to speculations concerning the earth's age
and history.
COSTEANING. A mining term. See 1146.
COUNTER-CURRENT. A current running in an opposite direction to some other.
CRAG. The name given to certain Tertiary deposits in Norfolk and Suffolk. See
735,745.
CRAG AND TAIL. The condition of a hill, as of gravel, when one side is steep and
the other a gradual slope.
CRANIUM. The skull.
CRATER. The cup-shaped cavity usually distinguishable at the summit of a volcano.
CREEP (in Mining). See 1104.
CRETACEOUS. Belonging to the chalk. The " Cretaceous series 1 ' of rocks is that
which includes the chalk.
CROPPING OUT. The out-crop of a bed is its first appearance at the surface.
550 GLOSSARY OF TERMS.
THE EARTH. The external film of the earth exposed to view or in any
way available for examination.
CRYSTAL. The regular form in which a mineral is presented when that form can be
described mathematically. A mineral is said to be crystalline when its atoms are
arranged with reference to some definite form.
CULM. An impure kind of coal. See 930.
CUMBRIAN. Occurring in Cumberland. The " Cumbrian System" of Prof. Sedgwick
is a part of the Silurian series of the Lake district of Cumberland and Westmore-
land.
CURRENTS, MARINE. See $ 122.
DEBACLE. A sudden rush of waters breaking down obstacles and removing detritus.
DEBRIS. The fragments of rocks removed by the action of weathering or by water.
DEFLECTION. Deviation from a straight course.
DEGRADATION. The wearing away of rocks, generally effected by aqueous action.
DELIQUESCENT. Becoming fluid by the attraction of water from the atmosphere.
DKLTA. The alluvial land formed by a river at its mouth, usually expanded in a fan
shape like the fourth letter of the Greek alphabet (A), and thence called Delta.
DENUDATION. The act of laying bare some rocks formerly covered up, the removal
of the overlying masses being effected by water. See 608.
DEPOSIT. Matter laid or thrown down.
DESICCATION. The act of drying up.
DETRITUS. Matter rubbed off by mechanical action from other rocks.
DIKE. See DYKE.
DILUVIUM. Accumulations of gravel and fragments of rocks removed from a distance,
supposed by some to have been the result of a violent rush of water, but more
probably left by icebergs that have melted on the spot.
DIMORPHISM. See 291.
DIP (in Geology). The angle of inclination which the plane of a bed makes with the
plane of the horizon.
DIP OF NEEDLE. The depression from horizontally of a magnetic needle not in the
magnetic equator.
DISRUPTION or DISLOCATION. A forcible rending asunder.
DOLOMITE. Crystalline carbonate of lime and magnesia.
DRUSE. A cavity in a mineral containing crystals.
DUNES. Low hills of blown sand.
DYKE. A rock, generally crystalline, occupying a rent or fissure in some other and
older rock. A dyke differs from a mineral vein chiefly in its greater magnitude
and in the absence of ramifications. The word is sometimes written Dike.
EARTH'S CRUST. See Crust of the Earth.
EARTHQUAKE. An undulation of the earth's crust. See $ 1 95.
EFFLORESCENCE. The term used to describe the falling to powder of certain minerals
on exposure.
EMBOUCHURE. The mouth of a great river.
GLOSSARY OF TERMS. 551
EOCENE. The name given by Sir C. Lyell to the lowest and oldest division of the
Tertiary series of rocks.
EPOCH. A fixed point in time from which a new period is measured. The term is
also used to designate the period.
EQUATOR. An ideal great circle on the globe, everywhere equidistant from both the
poles.
EQUIVALENT (Chemical). A number representing the relative weight of elementary
substances, and used for them, as being equivalent to them. See 10.
EROSION. The gradual wearing of an exposed rock as if by eating away.
ERRATIC BLOCKS. See Boulders.
ERUPTION (Volcanic). See 218.
ESCARPMENT. The steep face of a mountain chain or a ridge of high land.
ESTUARY. An inlet of the land entered by the sea, but having a stream of fresh water
coming in from the land.
EXOTIC. Foreign.
EXUVLE. A name sometimes given to all fossil remains found in the earth's crust.
FACE (in crystallography). The surface of a regular solid.
FALUN. A French provincial name for the strata found in the Touraine, correspond-
ing to the Suffolk crag.
FAULT. The interruption of continuity of strata, accompanied by a displacement of
one or both sides of the fissure (see 615).
FAUNA. The whole group of animals peculiar to a country or natural region at some
one period.
FERRUGINOUS. Irony, or containing iron.
FILAMENT. A thread or fibre.
FIORD, or FJORD. A deep narrow inlet.
FIRE-CLAY. A kind of clay not containing much alkaline earth, and therefore resist-
ing fusion at high temperatures.
FIRE-DAMP. Light carburetted hydrogen gas evolved from coal in mines, and be-
coming explosive on mixture with common air (see 1119).
FIRE-STONE. A stone that resists fusion at ordinary high temperatures. The Upper
greensand deposits, between the lowest chalk and the Gault, are sometimes called
by this name.
FISSILE. Capable of being split asunder.
FISSURK. A crack or open crevice in rocks.
FIXED AIR. Carbonic acid gas.
FLINT. A peculiar form of silex, dispersed either in regular beds or at irregular inter-
vals through chalk.
FLOETZ ROCKS. The name given by Werner, and sometimes employed by the earlier
English geologists, to distinguish the comparatively horizontal beds of the Secondary
period. The term, being altogether inapplicable in the sense originally intended?
is now rarely used.
FLORA. The group of vegetables of all kinds belonging to a natural district, and
existing at a given time.
552 GLOSSARY OF TERMS.
FLUVIATILE. Belonging to a river.
FLUX. A substance added to render certain minerals more fusible.
FORAMINIFERA. The name given to a group of many-chambered shells, generally
microscopic, the chambers communicating by a small open orifice (foramen).
FORELAND. A promontory or tract of high land jutting into the sea.
FORMATION (in Descriptive Geology). A group of deposits, of whatever kind, referred
to a common origin, or belonging to the same period.
FOSSIL. A word originally applied to all substances dug out of theearth, including
therefore all minerals, but now limited in its application to the remains of organic
beings, whether vegetable or animal, buried beneath the surface.
FOSSILIFEROUS. Containing fossils or organic remains.
FREE- STONE. A stone capable of being readily worked for purposes of construction-
FRESHET. A periodical flood.
FRINGING REEF. A reef or bank of coral of inconsiderable depth, and close to a coast
line.
FRITH. A deep and comparatively narrow arm of the sea.
FUCOID. That which resembles a fucus, or sea- weed: fossil remains of fuci are
called fucoids.
FULGORITE. Sand-tubes produced by the fusion of loose sand during the passage
of lightning through it.
FULLER'S EARTH. A kind of clay containing much water, and used in some parts
of the manufacture of cloth.
FUMAROLE. An eruption of smoke.
FUSIBLE. Capable of being fused or melted.
FUSIFORM. Spindle-shaped.
GANOID. A group of fishes having enamelled scales.
GASTEROPODA. A group of shell-bearing animals covered by one valve, and having
a fleshy foot attached to the belly.
GAULT. A bluish clay underlying the Chalk and Upper greensand in England.
GEM (in Mineralogy). Any precious stone.
GENUS. A group of species having certain important characters in common.
GEODE. A stone having a hollow in the interior lined with crystals.
GEOGNOSY. A term used in Germany to distinguish the historical sequence of
events in the earth's history in contradistinction to GEOLOGY, by which is meant
an account of the actual condition of the earth's crust. The distinction, however,
is not admitted by English Geologists, and the word is not introduced into our
scientific language.
GLACIER. A mass of frozen snow and ice formed in the upper gorges of mountains
above the limit of perpetual snow, and proceeding down into the lower parts of
valleys or into the sea, in the latter case ultimately breaking off and becoming
ice-bergs*
GLACIS. A moderately sloping bank or gentle and smooth declivity.
GLANCE (in Mineralogy). A peculiar kind of lustre commonly presented in some
sulphurets, as Blende.
GLOSSARY OF TERMS. 553
GNEISS. The name given to mixtures of quartz, felspar, and mica, in which there is
a laminated arrangement of the different ingredients.
GONIOMETER. An instrument, of which there are several varieties, for the purpose
of measuring the angles between the plane faces of crystals.
GRANITE. A rock consisting generally of crystals of felspar and mica embedded in
a quartzy base.
GRANULAR. Consisting of small grains.
GRAUWACKE or GREYWACKE. The name given by German geologists to some of the
older fossiliferous rocks, and generally of a grey colour, sandy composition, and
fissile nature.
GRAVEL. An accumulation of small pebbles more or less rounded, occurring with
sand and sometimes clay.
GRIT. A coarse-grained sandstone.
GYRATORY. Having a revolving motion.
HABITAT. The natural district to which a species of animals or vegetables is
confined in its distribution.
HADE. The dip or inclination of a mineral vein.
HEMI-HEDRAL (in Mineralogy). See 260.
HEMITROPY (in Mineralogy). See 287.
HORNBLENDE. An important mineral in the composition of some rocks.
HORNITOS. Small hills in volcanic districts from which hot smoke issues.
HORNSTONE. A variety of quartz found in volcanic districts.
HORSE (in coal mining). A mass of earthy matter intervening between the upper
and lower parts of a bed of coal.
HYALINE. Transparent like glass.
HYDROUS. Containing water.
HYDROGRAPHY. The description of the sea, lakes, rivers, and other aqueous portions
of the earth's surface.
HYDROLOGY. The science of the distribution and phenomena of water on the earth's
surface.
HYGROMETER. An instrumentfor measuring the degree of moisture of the atmosphere.
HYPOGENE ROCKS. Rocks formed beneath others or which are assumed to have ob-
tained their present aspect underneath the earth's surface.
HYPOTHESIS. A general view founded upon certain known facts of limited range.
ICEBERG. A floating mass of ice, often of great magnitude and always of consi-
derable depth, first produced in cold seas, and conveyed thence into warmer latitudes
by marine currents. Ice-fields and Ice-floes are flat shallow islands of nearly pure
ice formed by the freezing of ocean water, but icebergs have generally been detached
from glaciers, and are often loaded with gravel, blocks of stone, and earth.
ICHTHYODORULITE. The fossil spine of certain fishes resembling sharks.
ICHTHYOLOGY. The study and description of fishes.
ICHTHYOSAURUS. A marine reptile (fish-lizard), whose remains are very abundant
in rocks of the Secondary period.
554 GLOSSARY OF TERMS.
IGNEOUS ROCKS. Rocks, such as lava, trap, and some others which have been fused
by volcanic heat. Granite and other porphyritic rocks are sometimes called crystal-
line.
IMBRICATED. Covered with scales overlapping each other like tiles on the roof of a
house.
IMPERMEABLE. Not admitting the passage of water.
INCRUSTATION. An adherent coating. A crust formed on the surface of any sub-
stance.
INDURATED. Hardened.
INFUSORIAL ANIMALCULES. See Animalcules. Minute animals found in vegetable
infusions, or in stagnant water containing organic matter in a state of decomposition.
INORGANIC. Not produced by vital action.
INVERTEBRATA. Animals not furnished with a back bone.
IRIDESCENCE. Shining with the colours of the rainbow.
ISOCHIMENAL. Having the same mean winter temperature.
ISOCHRONOUS. Occurring at equal times, or equal intervals of time.
ISODYNAMIC. Having the same force.
ISOMERISM. See 300.
ISOMORPHISM (in Mineralogy). The condition of similar crystalline forms occurring
in different chemical combinations.
ISOTHERAL. Having the same mean summer temperature.
ISOTHERMAL. Having the same mean annual temperature.
JOINTS. Natural fissures in rocks, or lines of parting, having definite compass
bearings and generally arranged in groups or sets.
KAOLIN. The Chinese name of the fine, pure clay used in the manufacture of
porcelain.
KILLAS. A Cornish name for a coarse clayslate, but generally confined to varieties
that are not very schistose.
LACUSTRINE. Belonging to a lake.
LAGOON. A salt-water lake, or part of a sea nearly enclosed by a strip of land.
LAMINATED. Arranged in thin plates or laminae.
LANDSLIP. A portion of land that has slid down in consequence of some disturbing
or undermining action.
LAPILLI. Small volcanic cinders.
LATERITE. A peculiar rock found in India cut into the form of bricks and used for
the same purpose. See p. 544.
LAVA. The melted rock which flows sometimes from a volcano. It consists of a
large proportion of felspar, and is often very cellular.
LENTICULAR. Lens-shaped.
LIAS. A provincial name now generally adopted to designate the calcareous clay or
clayey limestone occurring between the Upper new red sandstone and the Oolite.
LIGNEOUS. Woody.
GLOSSARY OF TEEMS. 555
LIGNITE. Wood converted into an imperfect kind of coal.
LITHOLOGICAL. A terra used to express the stony character of a rock in contradis-
tinction to its zoological or even mineralogical character.
LITTORAL. Belonging to the shore.
LLANOS. The treeless plains of the banks of the Orinoco in South America.
LOAM. A mixture of sand and clay.
LODE. A metalliferous vein.
MACIGNO. An Italian name for a peculiar siliceous sandstone with calcareous
grains. See 791.
MACLE (in Mineralogy). A twin crystal. See 287.
MALLEABLE. Capable of being beaten out into a thin plate under the hammer.
MAMMALIA. Animals that suckle their young.
MAMMOTH. An extinct and northern species of elephant, the carcase of one indi-
vidual of which was found buried in icy cliffs on the shores of the Arctic ocean.
MARL. A mixture of clay and lime.
MATRIX. The earthy or stony matter in which a mineral or fossil is embedded.
MECHANICAL ROCKS. Rocks formed by deposition from water.
METAMORPHIC ROCKS. Rocks that have undergone change or metamorphosis since
their original formation.
METEORITE. See Aerolite.
METEOROLOGY. The science of the phenomena of the atmosphere.
MINERAL VEIN. A crevice in the earth filled with mineral substances, often metalli-
ferous.
MIOCENE. The middle of the three divisions of tertiary rocks, according to Sir C.
Lyell.
MIRAGE. An effect of refraction by which distant objects are apparently brought
near, or are seen in an inverted position, or of different form from that which truly
belongs to them.
MOLASSE. A provincial name for a sandstone associated with marl and conglome-
rates, found abundantly in the great valley of Switzerland. It belongs to the
middle tertiary period.
MOLECULES. The ultimate particles or atoms of bodies. See $ 5.
MONSOONS. Periodical winds, occurring chiefly in the Indian ocean. See $ 101.
MORAINE. A Swiss term for the debris of rocks brought down into valleys by
glaciers.
MULTILOCULAR. Many- chambered.
NEPTUNIAN. A supporter of the theory of aqueous action in the formation of
rocks, in opposition to the Vulcanists.
NODULE. A rounded irregular-shaped mass.
NUCLEUS. The solid centre, about which matter is often collected to form solids.
NUMMULITES. A group of foraminiferous jshells, some of them of large size and very
abundant, occurring in rocks chiefly of the oldest tertiary period.
556 GLOSSARY OF TERMS.
OASIS. A fertile spot in a desert.
OBLATE. Flattened at the poles.
OOLITE. A limestone composed of rounded particles like the roe of a fish. The
name Oolitic is applied to a considerable group of deposits in which this limestone
occurs.
OPALESCENT. Exhibiting a play of colours like noble opal.
OPALIZED WOOD. Wood penetrated by silica, and acquiring the structure of opal.
OPERCULUM. A kind of lid closing the mouth of univalve shells ; also, the lid or
flap covering the gills of fishes.
OPHITE. A rock nearly allied to serpentine.
ORE. The mineral compounds in which metals occur, and from which they are
usually obtained.
ORGANIC. Exhibiting organization, or the results of vital force. Organic remains,
or fossils^ are the remains of the animals and vegetables of a former state of exist-
ence found buried in rocks.
ORYCTOLOGY. A term now entirely disused, meaning an account of all bodies
whether organic or inorganic, found buried in the earth.
OSSEOUS. Bony : Osseous breccia is a conglomerate made up of bones cemented to-
gether by lime, and mixed with earthy matter.
OUTCROP. The line at which a stratum first shows itself at the surface in inclined
deposits.
OUTLIER. A portion of a stratum detached from the principal mass. (See figs.
113119.)
OXIDATION. The combination of a substance with oxygen the film generally pro-
duced on the surface of metals and many earths by this process is called an oxide.
In some cases, as in that of iron, it is called rust.
PACHYDERMATA. A group of animals so called from the thickness of their skin.
The elephant and pig are well known examples.
PALEONTOLOGY. The science which treats of fossil organic remains : it is the
zoology and botany of the ancient conditions of the earth.
PALEOTHERIUM. A genus of Pachydermata, allied to the Tapir. (See AnoplotJie-
rium.)
PAMPAS. Treeless plains of Patagonia in South America. ( 64.)
PAPER COAL. A thinly laminated lignite, or bituminous shale, splitting into leaves.
PARTING (in mining). The name given to a thin seam between two beds.
PEAT. A vegetable accumulation produced in moist situations, and presented in a
spongy mass.
PEGMATITE. A granite in which the three component minerals form distinct masses,
united and cemented together.
PELAGIAN. Belonging to the sea.
PEPERINO. An Italian name for a particular kind of volcanic rock, formed by the
cementing together of volcanic sand and ashes.
PERCOLATION. The filtering through of water.
PETRIFACTION. The act of turning into stone. (See $ 298.)
GLOSSARY OF TEEMS. 557
PETROLEUM. Mineral pitch.
PH^ENOGAMOUS, or PHANEROGAMIC PLANTS. Those in which the reproductive or-
gans are apparent.
PHYSICAL. Literally natural, but used in scientific language in treating of the higher
and wider views of various departments with reference to the whole external world,
and not to mere human objects. Thus Physical Geography includes the description
of all the natural phenomena of the globe. Physical Geology, that part of Geology
in which the history of all Nature, from all time, is discussed. So also by PHYSICS
we understand the department of science which treats of the various properties of
natural bodies, the laws of their motion, and the results of their mutual action in a
mechanical sense.
PHYTOLOGY. The department of Natural History which relates to plants. Botany.
PIPE CLAY. A plastic clay used in making pipes.
PISIFORM. Pea- shaped.
PISOLITE. A stone made up of rounded concretions like peas. The word pisolitic is
used to express an approximation to this structure.
PIT-COAL. The name often given to common coal, from its being dug out of pits.
PLACOID. A group of fishes, so called from the structure of their scales.
PLASTIC. Capable of being moulded into form. Thus, plastic clay is so called from
its use in pottery. The Plastic clay formation is the lower part of the older Ter-
tiary series, containing in some places clay used in pottery.
PLATEAU (in Physical Geography). A plain or expanse of land considerably above
the level of the ocean.
PLESIOSAURUS. An extinct genus of reptiles. (See 846.)
PLICATED. Arranged in folds or contortions.
PLIOCENE, OLDER AND NEWER. The upper part of the Tertiary series, so called by
Sir C. Lyell from the preponderance of recent shells in them.
PLUMBAGO (Black lead). The name commonly given to graphite, a form of carbon.
PLUTONIC ROCKS. Rocks supposed to be due to igneous action at great depths below
the earth's surface, have been thus named by older geologists. The igneous action
is not manifest in such rocks, but presumed, as in the case of granite.
PCECILITIC. From a Greek word signifying variegated the name given to the upper
part of the New red sandstone series of England.
POLAR FORCES. (See 29.)
POLYPARIA. A group of animals of which the coral animal is a well known example.
POLYTHALAMOUS. Many chambered.
PORPHYRY. A name originally given to *a red rock with small crystals of felspar,
found in Egypt, and so called from its usually red colour ; although our present
purple (also derived from the same word), is very different. The word is now used
to denote any rock having crystals, embedded in a base of other mineral composition.
Thus granite is a porphyritic rock, having crystals of felspar and mica embedded
in a quartz base.
POZZUOLANA. Volcanic ashes used in Italian buildings instead of mortar, and
answering the purpose of Roman cement. It is so called because shipped from
Puzzuoli.
558 GLOSSAEI OF TEEMS.
PRAIRIES. The level plains of some of the great river valleys of North America, are
thus denominated.
PRECIPITATE. The deposit obtained when substances that have been dissolved in a
fluid are thrown down by further chemical combination, and in consequence of new
affinities produced.
PRIMARY, or PRIMITIVE. This name is commonly applied to the rocks which un-
derlie those that are manifestly of mechanical origin and contain fossils. The use
of the term, however, involves an hypothesis which is by no means to be admitted
namely, that such unfossiliferous and crystalline rocks were earlier formed than
any deposits containing organic remains. It is desirable that no such expressions
should be employed ; and Sir C. Lyell has suggested the word Hypogene as
adapted to replace Primary. Perhaps merely descriptive names, as Crystalline^ are
yet more satisfactory. Almost all these rocks are Metamorphic.
PTERODACTYL. A remarkable genus of reptiles adapted for flight : its remains have
been found in a fossil state throughout the Secondary rocks.
PUDDING STONE. The name often given to coarse conglomerates in which the frag-
ments or pebbles are rounded.
PUMICE. Volcanic ashes.
PYRITES. A name given to the combinations of certain metals with sulphur. Iron
and copper pyrites are the most common ; the former is often found in chalk, slate,
and other stratified rocks, the latter only in mineral veins.
PYROMETER. An instrument for measuring intense heat.
QUA-QUA-VERSAL. The dip of beds in every direction from an elevated
central point. The beds on the flanks of a volcanic cone dip in this way.
QUARTZ. The common form of silica ; rock-crystal and flint are examples.
QUARTZITE. A rock composed of quartz grains, passing into compact quartz.
RADIATA. A division of the animal kingdom so called because the body is fre-
quently presented in a radiated form like the common star fish.
RADIATION (in Chemistry). The mode in which heat is thrown out into space from
the surface of any substance.
RAG. A stone of coarse texture ; the name is given indifferently to aqueous and
igneous rocks.
RAKE VEIN (in mining). A group of vertical veins.
RAVINE. A deep, hollow, narrow excavation.
RECENT. The name given in Geology to the period immediately past or still in pro-
gress ; the limit of existence of some races of animals and vegetables is generally
taken as that of the recent period.
RED MARL. A name for the New red sandstone.
REFRACTION. The bending aside of light when it passes from one transparent sub-
stance into another of different density. Double Refraction is the separation into
two rays that occurs when light enters certain crystals, as Iceland spar.
RETICULATED. A structure of crossed fibres, like a net, is said to be reticulated.
ROCK (in Geology). Any mass of mineral matter of considerable or indefinite ex-
GLOSSARY OF TEEMS. 559
tent and nearly uniform character, is called in geological language a rock, without
regard to its hardness or compactness: thus, loose sand and clay, as well as
sandstone and limestone, are spoken of under this name.
ROCK SALT. Common salt occurring in a crystalline state in rocks.
ROE-STONE. The name sometimes given to Oolite.
ROTHE-TODTE-LIEGENDE. The German synonym for the lower part of the Magne-
sian limestone, or Permian series.
RUBBLE. A term applied by quarry-men to the fragmentary and decomposed parts
of stone generally surmounting each bed.
RUMINANTIA. An important group of quadrupeds including those which chew the
cud, as the ox, deer, &c.
SACCHAROID. Having the texture of loaf sugar.
SALIFEROUS SYSTEM. The New red sandstone system, so called from the salt with
which it is associated in parts of England.
SALSES. Eruptions of mud from small orifices, generally in volcanic districts.
SAURIAN (Reptilian). Any animal of the lizard tribe, and many extinct reptiles
only distantly allied to these.
SAVANNAHS. The low plains of North America, generally covered with wood.
SCAGLIA. An Italian rock, contemporaneous with our chalk.
SCARPED. Having a steep face.
SCHIST. A name often used as synonymous with slate, but more commonly and
very conveniently limited to those rocks which do not admit of indefinite splitting
like slate, but are only capable of a less perfect separation into layers or laminae.
Of this kind are gneiss, mica-schist, &c., often more or less crystalline.
SCORIAE. The name given to volcanic ashes. The word means any kind of cinders,
but its scientific use is thus limited.
SEAMS. A name sometimes given to any thin beds, but more usually applied to thin
layers separating two strata of greater magnitude.
SECONDARY STRATA. An extensive and important series of stratified rocks, having
certain characters in common distinguishing them from the overlying rocks called
" Tertiary," and the underlying group known as the '* Palaeozoic."
SELENITE. A name often given to crystalline sulphate of lime.
SEPTARIA. Flattened nodules often found in clay, and consisting chiefly of argilla-
ceous limestone, traversed by numerous cracks proceeding from the centre, and often
filled with calc spar.
SEPTUM. A partition ; the plates separating the chambers in the Nautilus and other
allied genera are called septa.
SERPENTINE. A rock generally more or less crystalline, and often of green and
variegated colour ; it is abundant in the Alps, and is found also in Cornwall.
SPIALE. See Schist and Slate. An indurated clay, less fissile than schist, but splitting
with tolerable facility in plates parallel to each other, and to the original planes of
bedding.
SHANKI.IN SAND. A name given to the Lower green-sand from its being found at
Shanklin, in the Isle of Wight.
560 GLOSSARY OF TERMS.
SHELL MARL. A deposit of clay, peat, and silt, mixed with shells, which collects at
the bottom of fresh water lakes.
SHINGLE. The loose rounded water-worn fragments of stone or gravel found on the
sea shore, or where the sea has once been.
SHOOT (in mining). A vein parallel to the stratification.
SILEX, SILICA. The name given by Mineralogists to a pure earth, more commonly
spoken of as Jlint, and, when crystallized, called rock crystal. (See 359.) Sili-
ceous means flinty, and silieified a substance mineralised by siliceous earth. /Siliceous
sinter is a siliceous deposit from springs.
SILT. The name usually given to the muddy deposit found at the bottom of running
streams. Rivers and creeks are often said to be silted up when this deposit accu-
mulates at their mouths.
SILURIAN. The name given by Sir R. Murchison to an important series of fossili-
ferous rocks \vell developed in, and first described from, a district in Wales and
Shropshire formerly inhabited by the Siluri, a tribe of Ancient Britons.
SILVAS. The wooded plains of the Amazons River in South America.
SIMPLE MINERALS. Minerals that admit of definite description as consisting of defi-
nite chemical compounds occurring in nature.
SIMPLE ROCKS. Rocks containing some very predominant mineral and developed
to a great extent in nature. Thus limestone, sandstone, clay, granite, &c., are
simple rocks.
SINTER. A rock precipitated from mineral water. Calcareous and siliceous sinters
are those only that are generally described.
SIPH UNCLE. A small tube passing through an orifice in the septum of a chambered
shell.
SLATE. The most perfectly fissile form in which clay exists in nature. See Schist
and Shale, where the less perfectly cleaving rocks of this kind are described.
SLICKENSIDES. The smooth striated surface of a fault ; also one of the ores of lead
found in Derbyshire.
SLIDE. A miner's name for a small fault.
SOIL. The name given to the disintegrated and decomposed rock at the surface of
the earth when this has become mixed with carbon and other substances so as to
enable plants to grow and obtain their required mineral constituents.
SOLFATARA. A volcanic vent from which sulphur and sulphurous, watery, and acid
vapours and gases are emitted.
SOLID ANGLE. The inclination of three or more planes meeting in a point.
SPAR. A name given to many crystalline minerals which usually afford clean and
ready fracture.
SPECIES (in Natural History). This term, the true application of which is most im-
portant in Natural History, is understood to mean in the higher forms of animal
existence a group of all the individuals which, under ordinary conditions and in a
natural state, breed together and produce like individuals. When offspring is
obtained from a male and female of distinct species (which is not usual), this is
either absolutely barren, or at least becomes barren in one or two generations, so
that no new form or species is thus perpetuated. The differences of specific
GLOSSARY OF TERMS. 561
character are apparently preserved in almost all details of structure in these cases
but the term species must often be applied doubtfully and hypothetically in animals
of lower organisation, in plants, and above all in minerals.
SPHEROID. Having a shape nearly resembling that of a sphere or globe.
SPRINGS OF WATER. See 1049.
SQUALOID. Resembling a shark.
STALACTITE AND STALAGMITE. Concretions of carbonate of lime and sometimes of
other minerals, as quartz or even malachite, deposited by water dropping from the
roof of a cavern or other vacant space. When the mineral is deposited in columns
pendant from the roof of the cavity the name Stalactite is given. When the
columns or heaps rise from the floor after the water has dropped they are said to be
Stalagmites.
STANNIFEROUS. Containing tin.
STEPPE (in Physical Geography). A low plain.
STOCK- WORK. A vein of very great magnitude, requiring to be worked with special
reference to this unusual condition.
STRATIFICATION. The condition of rocks or accumulated minerals deposited in
layers, beds, or strata. A single bed is called a stratum. A large proportion of
the masses constituting the earth's crust are thus arranged or stratified, and the
planes of stratification are generally parallel to each other, though often much
removed from their original condition of horizontality.
STREAM-WORK. A place where metalliferous ores are obtained and worked by
the mechanical use of water in separating the ore from gravel with which it is
found.
STRIKE. The line of bearing of strata, or the direction of any horizontal line on a
stratum.
STUFA. A jet of steam issuing from fissures in volcanic regions at a temperature
often much above the boiling point of water.
STRUCTURE. A term often used technically in Geology and Mineralogy to denote
the condition in which the component parts are arranged.
SUB-APENNINE BEDS. The name of a deposit found in a low chain of hills at the
foot of the Apennines in Italy.
SUBLIMATION. The deposit of a solid from a state of vapour.
SUBSIDENCE. The act of sinking, often traceable over extensive areas and connected
with great geological changes.
SUBSOIL. The decomposed rock often underlying vegetable soils, and not exposed
at the surface except by denudation or deep ploughing.
SULCATED. Furrowed
SUPERPOSITION. An expression very commonly employed by Geologists to describe
the order of arrangement when one bed or stratum reposes upon another. See
Conformable and Unconformalle superposition.
SUPRA-CRETACEOUS. A term applied by Sir H. de la Beche to the rpcks overlying
the chalk. The term Tertiary is now universally adopted for this group.
SURTURBRAND. A name sometimes given to varieties of lignite.
SYENITE. The granite of the quarries of Syene in Egypt. It is usual to call by
562 GLOSSARY OF TERMS.
this name any combination of quartz, felspar and hornblende ; but the quartz is
sometimes absent and sometimes accompanied by mica.
SYNCHRONOUS. Occurring at the same time. Contemporaneous.
SYNCLINAL AXIS. The line of depression between two anticlinal axes. See 611.
TABLE LAND (in Physical Geography). Land elevated much above the level of
the sea and generally offering no considerable irregularities of surface.
TALUS. The accumulation at the foot of a steep rock, produced by fragments broken
oft', fallen down, and formed into a sloping heap.
TERMINOLOGY. The technical classification of a science, and the terms used in it in a
technical or special sense.
TERTIARY STRATA. The series of sedimentary rocks overlying the chalk, or other
representative of the Secondary period, and extending thence to the rocks of the
Recent period.
TESTACEA. Molluscous or soft animals having a shelly covering.
THERMAL. Hot. Thermal Springs are springs whose temperature is above the mean
annual temperature of the place where they break out.
THERMOMETER. An instrument for measuring differences of temperature by com-
paring them with the expansion and contraction of a fluid having a graduated scale
attached to it.
THINNING OUT of strata. When a stratum gradually diminishes in thickness as it
is traced in any particular direction, and ultimately disappears, it is said to thin out.
TOAD-STONE. The name given by miners to beds of basalt, occurring in Derbyshire.
It is probably derived from the German Todt-sttin, or dead-stone, as being without
the ores found in the neighbouring limestone.
TORNADO. A violent stonn or hurricane.
TRANSITION. The name formerly given to certain rocks, now called Palaeozoic, under
the impression that they afford a passage from the crystalline state of gneis, mica
schist, clay-slate, c., to what was considered the more mechanical condition of
Newer or Secondary rocks. Since, however, it appears that such transition be-
longs to no particular geological period, but occurs in all, the term has ceased to be
applicable and has fallen into disuse.
TRADE-WINDS. Winds, chiefly from the east, blowing constantly in particular
latitudes and useful in navigation. See 99.
TRAP. Crystalline rocks, composed chiefly of felspar, augite, and hornblende, com-
bined in many ways, and exhibiting great varieties of aspect, are frequently
called by this name. The word is derived from the Swedish trappa, a stair or step,
because such rocks are often found in large tabular masses, rising one above
another in steps. Trap, or Trappean-rock, is supposed to have been lava formerly
ejected from fissures or craters, and often poured out under water. Basalt is the
most common synonym for trap rock.
TRAVERTIN. A white concretionary stone, usually hard and semi-crystalline, deposit-
ed by water containing lime in solution, and very abundant in some parts of Italy.
TRIAS. The name given on the continent to the beds of the New red sandstone
series.
GLOSSABr OF TERMS. 563
TRILOBITE. A common fossil in the Dudley limestone, so named from the character-
istic species having the body divided into three lobes. Trilobites are the remains of
a remarkable extinct family of Crustaceans, of which the crab, lobster, &c., are
modern representatives.
TRIPOLI. A powdery, siliceous rock, used in polishing metals and stones, and derived
from the siliceous cases of infusorial animalcules.
TRUNCATED. Cut off or shortened. A crystal is said to be truncated when a solid
angle or edge is removed symmetrically.
TROUGH (in Geology). A basin-shaped or oblong depression.
TUBBING, METAL (in mining). The cast-iron fame work fitted to a shaft in order to
keep out springs of water from the works.
TUFA, TUFF. An Italian name for a variety of volcanic rock of earthy texture, and
made up chiefly, or entirely, of fragments of volcanic ashes.
TURBINATED. Shells which have a spiral or screw-like structure are thus named.
TURRILITE. An extinct genus of chambered shells, resembling an Ammonite wound
into a turbinated form.
TYFOON, or TYPHOON. A violent periodical hurricane occurring in the China Seas.
TYPE (in Natural History). A representative form.
UNCONFORMABLE SUPERPOSITION (in stratification). The condition of strata
when one has been deposited horizontally upon the upturned edges of those imme-
diately below.
UNDERCLIFF. The name applied to a cliff when the upper part has fallen down along
a considerable line of coast, and forms a subordinate terrace between the sea and
the original shore.
UNDERCLAY. The fine tenacious and tolerably pure clay, containing frequently roots
of Stigmaria, and very often found below beds of coal in the coal-measures.
UNDERLAY, or UNDERLIE. The dip or inclination of a mineral vein.
UNIVALVE. An animal provided with a shell in one piece.
UNSTRATIFIED. Rocks have sometimes been divided into two principal groups,
Stratified and Unstratified, and these have been assumed as synonymous with
Aqueous and Igneous. Granite and many of the rocks usually regarded as of igne-
ous origin, are, however, sometimes found in beds or strata.
VEINS, MINERAL. Crevices in rocks filled up with mineral substances often crystal-
line.
VEINSTONE. The earthy minerals occupying veins when these are associated with
metalliferous ores.
VERTEBRATA, or Vertebrated Animals. A large and most important division of the
animal kingdom, including all those animals provided with a back bone.
Each separate bone of the back is called a vertebra.
VERTEX. The summit or upper part of a solid.
VITREOUS. Glassy. Used in Mineralogy to designate a peculiar lustre.
VOLCANO. A mountain or hill of conical shape, having at or near the summit a cup-
shaped depression called the " crater." From this proceed vapours of sulphurous
564 GLOSSARY OF TERMS.
and acid gases with jets of steam, and from time to time ashes are thrown up high
into the air : or currents of melted rock or lava burst forth and pour down the sides.
Volcanic bombs are detached masses ejected into the air, and assuming a pear shape
as they fall. Volcanic foci are subterranean centres of igneous action.
VULCANIST. A supporter of the theory of igneous action in the formation of rocks
as opposed to the Neptunians, who believed in aqueous action only. A term of
reproach belonging now only to the history of Geology.
WACKE. A barbarous name, formerly much employed by German geologists, and
thence introduced into English descriptions of the same date. It is regarded as a
soft and earthy basalt, but has been used in other senses and rather indefinitely.
WARP. The deposit of muddy waters artificially introduced into low lands.
WASTE (in mining). That part of a coal-mine out of the course of the principal
ventilation.
WATER-SHED. The line between two river basins. The water-shed is not necessa-
rily a mountain-chain, and in some rare instances it is broken by a water commu-
nication connecting two great river systems.
WEALDEN. The name given to an important fresh- water formation, occurring be-
tween the Cretaceous and Oolitic rocks, chiefly in the Wealds of Kent and Sussex.
WEATHERING. The wearing away of rocks consequent on atmospheric exposure.
WHET-STONE. A very hard and fine-grained slate containing much quartz.
WHIN-STONE. A provincial term applied to some trap rocks.
WIND-ROSE. An account of the mean pressure of the air under different winds.
See 89.
ZAFFRE. The impure oxide of cobalt, which, when melted with silica and potash
and reduced to powder, becomes powder-blue.
ZECHSTEIN. The German synonym for our magnesian limestone.
ZEOLITE. A group of minerals which swell and boil up when exposed to the blow-
pipe flame. See $ 417.
ZOOPHYTE. The term applied to some animals of low organisation, which, during
the greater part of their lives, are attatched to some foreign substance, and are inca-
pable of locomotion.
ALPHABETICAL INDEX.
ABSENCE of organic bodies in old rocks
explained, 317.
Absorbent power of various rocks, 468.
Acicular crystals, 149,
Acids, effect of, on minerals, 165.
Aclinic line, 20.
Adhesion, force of, 13.
Adige, delta of, 84.
Adit level, 502.
Advance of river deltas, 84.
Aerolites, 203.
Affinity, 13, 14.
African desert, 41.
Age of rocks containing veins, 308.
of coal, 481.
of the India coal, 538.
Aggregation, state of, in minerals, 155.
Agricultural Geology, 455.
Agriculturist, advantage of drainage to
the, 462.
Air phenomena of, 49 53.
Alabama coal-field, 419.
Alabaster, 258.
Alberese, 374.
Albian formation, 376.
Alkaline bases, importance of, in soils,
457.
Alkalis, use of, in determining minerals,
165.
Alleghany coal-field, 419.
Allotropy, 151.
Alluvial deposits of the Ural, 348.
Alps, age of, 388.
, considerations concerning their ele-
vation, 368.
, height of, 45.
Alterations of level by earthquakes, 107.
in consequence of
volcanic disturbances, 121.
Alum, 187.
crystals, group of, 1 32.
of Friesdorf, 353.
shale, 389.
Aluminous silicates, analysis of, 230.
Amazons, plains of, 41.
Amber, account of, 175.
mode of searching for, 366.
America, Drift of, 349.
, Recent deposits of, 343.
, Miocene tertiaries of, 357.
-, Eocene rocks of, 365.
, Upper cretaceous beds in, 377.
--, Oolites of, 388.
-, coal-fields of, 418.
-, Lower carboniferous rocks of,
428.
, Devonian beds of, 435.
, Silurian rocks of, 442.
, earthquakes in, 104.
, volcanoes of, 118.
American coast, temperature of, 59.
Ammonites Sucfdandi, 330.
catena, 391.
nodosus, 395.
Rhotomagensis, 376.
striatulus, 387.
Amorphous forms, 153,
minerals, the most useful to
the geologist, 246.
Amorphozoa, fossil remains of, 321.
Amplexus coralloides^ 323.
Ampullaria acuta, 363.
Amygdatoidal rocks, 286.-
Analysis by blow-pipe, 166.
of chalk, 372.
of clay iron stones, 207.
of clays, 260.
of coals, 174, 41 1, 422, 543.
of coloured marls, 265.
of fire-damp, 491.
of limestones, 256.
of magnesian limestones, 259.
of metamorphic rocks, 266.
of mud of the Nile, 86.
of porphyritic rocks, 270,
of red marl and cornstone, 28 1 .
of residuum in corals, 324.
of sandstones, 252.
of Tchornozem andRegur, 343.
of various minerals, 230.
566
ALPHABETICAL INDEX,
Analyses of simple minerals forming
rocks, 268.
Ananchytes ovatus, 372.
Andes, earthquakes in, 104.
, height of, 45.
, snow-line on the, 52.
Aneroid barometer, 51.
Angles and solid angles, 133.
Animalcules, infusorial, 115, 322.
Animals, distribution of marine, 94.
, kind of remains in various rocks,
313.
Antarctic currents, 67.
ocean, 32.
Anticlinal axes, 292.
Antimony, 213.
Antrim, basalt of, 125.
Apennines, elevation of, 368.
Apiocrinite bed, 386.
Aporrliais pes-pelicani, 355.
Appalachian coal-field, 419.
Application of fossils to the determina-
tion of rocks, 332.
of Geology to practical pur-
poses, 453.
Aptian formation, 378.
Aqueous action, reproductive effects of,
84.
and atmospheric action, 69.
meteors, 48.
or mechanical rocks, 249.
Arab-Caspian plain, 40.
, black earth of, 342.
Arctic current, 67.
, its effect on icebergs and
drift, 82.
land, Silurian rocks of, 443.
ocean, 32.
Ardwick limestone, 412.
Area, relative, of land and water, 23.
Argile de Dives, 384.
Argillaceous schist, 262.
Arkose, account of a rock so called, 391.
Arracan coal district, 536.
Arrangement of deposited material, 89.
Arsenic, 214.
Artesian springs, account of 466.
, temperature of, 24.
Asaphus caudatus, 438.
Asbestos, 198.
Ashby coal-field, 413.
Ashes, eruption of, 1 16.
Asia, earthquakes in, 103.
, extinct volcanoes of, 124.
, Newer tertiaries of, 352.
, Mountains of, 43.
Asia, volcanoes of, ] 1 8.
Assam coal-district, 536.
Astarte Basteroti, 352.
ekgans, 328, 384.
Asturias, coal-field of, 418.
Atlantic ocean, 28.
, action of waves on its coast, 76.
, tides of, 63.
, trade winds of, 56.
Atmosphere, chemical action of, in pro-
ducing decomposition of rocks, 479.
, limit of 24.
, phenomena of, 49 53.
Atmospheric and aqueous action, 69.
Atolls, structure of, 9 1 .
Atomic theory, 15.
weights, 6.
, their nature, 5.
Atoms, compound, 168.
Attraction, forces of, 12.
Augite, 197.
Aurora borealis, 21.
Austbeds (Lias), 390.
Australia, caverns of, 350.
, recent deposits of, 344.
, coal-fields of, 421, 428.
Axes of crystals, 135.
Axmouth, landslip at, 78.
Aymestry limestone, 437.
BACULITES Faujasii, 330.
Baffin's Bay, 30.
Bagshot sands, 361.
Baikal Lake, 38.
Baku, eruptions of, 97.
Ballons (Vosges) system of elevation of,
446.
Baltic sea, 29.
, accumulations of mud in, 85.
, raised beaches on the shores of,
126,
Banded structure, 279.
Barometer, account of, 51.
aneroid, 51.
Barometric change, 51.
wind-rose, 52.
Barrier (coral) reef, 91.
Barren soils, how corrected, 458.
Barrow, Lias of, 390.
Barton clay, 361.
Basalt, 267, 214^275.
of Fingal's Cave, 125.
, protruded through mechanical
rocks, 297.
underlying lignite, 353.
Basaltic dykes, 298.
ALPHABETICAL INDEX.
567
Basaltic platform of the Rhine, 123.
Bas Boulonnais, Wealden beds in, 380.
Basset, or outcrop, 291.
Bath oolite, 385.
Beaches, raised, 340.
Beaumont, Elie de, his theory of syn-
chronous elevations, 368.
Beds passed through in sinking wells,
476.
Bedding of rocks, 287.
Belemnites mucronatus, 330.
pistiliformis, 391.
Belgium, Lias of, 391.
, coal-fields of, 416.
, Devonian beds, 434.
Belts of high land in the earth, 43.
Benar coal-field, 536.
Bevelment in crystals, 134.
Binary compounds, essential elements
in/169.
Bismuth, 219.
Bitumen, where found, 97.
Bituminous eruptions, 96.
schist, 404.
Bivalve shells, extinct species of, 326.
Black ironstone band, 206.
Black-band of Scotland, 495.
Blackdown hills, beds of, 375.
Black-gang chine, 375.
Black sea, 29.
Blasting coal, 490.
Blocks, erratic, 345.
of stone removed by floods, 74.
, ridges of, on river banks, 82.
Blow-pipe, nature and use of, 166.
Board and pillar working 489.
Boase, Dr., his account of mineral and
other veins, 303.
Bocage (Calvados) system of elevation
of, 456.
Bog and peat moss, 342.
Bognor beds, 362.
Bohemia, coal-fields of, 417.
Bolsover stone, 259.
Bombay, Tertiaries of, 357.
Bordeaux, Miocene beds of, 356.
Boring for coal, 484.
Borneo coal, 542.
Boulder formation, 345.
Boulders, conveyed by ice, 82.
Brachiopoda, fossil remains of, 326.
Bracklesham sands, 361.
Bradford clay, 385.
Bramahpootra, delta of, 87.
Brard's process for determining the de-
composability of stones, 477.
Brattices in coal-mines, 489.
Brazil, caverns of, 350.
current, 67.
Breadth of veins, 305.
Breakwater, natural, formed by falling
rocks, 77.
Breccia marble, 258.
Brick clay, 189.
Bridlington beds, 345.
Brine-springs, 393.
Bristol coal-field, 413.
marble, 257.
Bronn, his account of recent and extinct
mollusca, articulata and vertebra ta,
331.
, his account of extinct species of
vegetables, 320.
Brora coal, 399.
Brown-coal of Germany, 353.
, flora of, 357.
Buddie, Mr. his account of records de-
sirable in coal-mines, 509.
, his method of panel-work-
ing, 488.
Building material, best kinds, 479.
, method of determin-
ing the relative value of, 479.
stones, 251, 256, 259.
Bunter sandstein, 396.
Burdwan coal, 428, 535.
CADMIUM, 213.
Caen limestone, 387-
Calamites cannceformis^ 407.
Calcaire a polypiers, 385.
de Blangy, 382.
grossier, 359, 360.
Calcareous veins, 304.
Calc grits, 383.
Calcutta, coal near, 535.
Cambay, Tertiaries near the gulf of, 358.
Cambrian rocks, 440.
Canal making, use of knowledge of
Geology in, 463.
Cape Breton coal-field, 421.
Capillary waves, 62.
Caradoc sandstone, 440.
Carbon, 173.
Carbonate of lime, quantity of, in a given
area of salt water, 324.
Carbonates, metallic, analysis of, 232.
Carboniferous limestone, 423.
system, 406.
Cardiglio marble, 257.
Cardium porulosum, 328, 363.
Cardona, salt of, 497.
568
ALPHABETICAL INDEX.
Carew's account of Cornish mines in
ancient times, 499.
Caribbean sea, 30.
Carpathians, elevation of the, 368.
Carrara marble, 258.
Caspian sea, 38.
Casts of organic bodies, account of, 311,
319.
Catalonia, extinct volcanoes of, 1 24.
Catenipora escJiaroides, 438.
Caverns, filling of, 341, 350.
Cement stones, 182, 362.
Central volcanoes, 121.
Cephalopoda, extinct, 328.
Ceratites nodosus, 395.
CeritUum giganteum, 361.
mutabile, 329.
Chalk, account of, 253, 372.
rate of percolation of water through,
467.
its condition as a water-containing
bed, 471.
needles on the coast of France, 77
Chalk-marl, 374.
Change, agents of, 16.
in structure of rocks, 286.
mechanical, produced on rocks
by water and air, 48.
of climate indicated by fossils,
312.
of material in deposits, 299.
of volume of rocks effected by
change of position, 302.
undergone in the process of fos-
silization, 311.
Changes occurring in basalt from slow
cooling when fused, 275.
observed in the earth's crust,
127.
produced in minerals by electric
action, 247.
Characteristics of minerals, 130.
Charnwood Forest, crystalline rocks of,
397.
Chasms produced by earthquakes, 107.
Chemical affinity, 1 3.
change in rocks, 69.
combination, 13.
equivalents, 7, 8.
language explained, 7.
Cheshire, account of New red sandstone
of, 393.
, salt-mines of, 495.
China, coal of, 421.
sea, storms of, 57.
Chirotfierium, 396.
Chlorite, 1 95.
Chlorite-schist, 266.
Chrome and its ores, 209.
Cipolin marble, 257.
Classes of rocks, 333.
Classification, importance of, in Minera-
logy, 129.
of minerals, table of, 171.
of rocks, principles of, 309,
333.
of rocks, table of, 336.
Clay, account of, 1 88.
, effect of an electric current passing
through, 247.
used in manufacture, 477.
Clay-group of rocks, 259.
Clay-ironstone, 206.
Clay-slate, 260.
Clay-soils, improvement of, 458.
Clays impermeable to water, 465.
Cleavage (in Mineralogy), 132.
of rocks, 277, 285.
Cliffs, action of the waves on, 76.
Climate, change of, indicated by fossils,
312, 316.
, general features of, 50.
, nature of, 57.
Clouds, 53.
Chinch, description of, 373.
Clymenia linear is, 330, 431.
Coal, general account of, 1 74.
, analyses of, 174, 400, 411, 422,
543.
, its derivation from vegetables, 248.
, formation of, 321.
Coal-fields of Oolitic system, 388, 399.
of Carboniferous system, 408.
in British Islands, 409.
in Belgium, 416.
in France, 417.
in Germany, 417.
in Spain, 418.
in America, 418.
in China, 421.
in India, 533.
Coal-measures, 407.
Coal-mining, account of, 481.
records, 509.
Coal-plants, 320.
Coast-line of the Atlantic, 28.
of the Pacific, 31.
Coast-lines, their relation to axes of ele-
vation, 47.
Cobalt, 209.
Cohesion, force of, 12.
Cold, poles of, 21, 60.
ALPHABETICAL INDEX.
509
Colder climate preceded the existing con-
ditions in Northern Europe, 316.
Colley-Weston slate, 386.
Colour of granite, 272.
of minerals (table), 156.
Coloured marls, 265.
Columnar structure of rocks, 282.
texture of minerals, 154.
Combination, chemical, nature of, 10, 13.
, representation of the law
of, 7.
Combinations, binary and ternary, 169.
, mode of expressing, 7.
of minerals, limit of, in
nature, 130.
of simple rocks, 264.
Combining measures of various elements.
Como, delta in the Lake of, 85.
Compact limestone, 255, 257.
Compass, mariner's, 18.
Compass-needle, lines of no variation of,
20.
Composition of clay-rocks, 261.
of limestone-rocks, 254.
of sand-rocks, 252.
of minerals, how deter-
mined, 164.
-, distinction between essen-
tial and accidental ingredients in, 1 67.
Compression of the earth, 23.
Compound atoms, 168.
Concretionary structure, 278.
veins, 304.
Condition of the earth during successive
periods, 449.
Configuration of land, 25.
Conformable stratification, 288.
Congelation, limit of perpetual, 52.
Conglomerates, 252.
Constance, newer Tertiary beds near the
lake of, 354.
Continental islands, 46.
Continents, form of, 25.
Contorted strata, 300.
Convulsions, no evidence of, afforded by
fossils, 313.
Cooling, effect of, when slow, on melted
basalt, 275.
Copper and copper ores, 221.
Coral, effect of, in deposits, 89.
islands and reefs, 90.
rag, 383.
sea, 92.
, areas of depression in, 127.
Coralline crag, 355.
Corals, fossil remains of, 323.
Cornbrash, 385.
Cornstone, 432.
, nodules in, 281.
Cornwall, systems of veins in, 305.
Corpuscular waves, 62.
Costeaning, 500.
Cote d'Or, system of elevation so called,
397.
Cotentin, beds of, 356.
Coursing the air in coal-mines, 490.
Crag, Coralline, 355.
, Norwich, 350.
, Red, 352.
Craigleith stone, account of, 251.
Crater of a volcano, 112.
of elevation, 114, 291.
Creep in coal-mines, 488.
Cretaceous system, upper, 371.
lower, 377.
Cropping out of beds, 291, 483.
Cross-courses, nature of, 306.
use of, 503.
Crushing of coal, 486.
Crust of the earth, its meaning, 3.
changes in, 69.
Crustaceans, fossil remains of, 331.
Cube, 135, 136.
Cube-octahedron, 134.
Culley, Mr., his account of floods in
Scotland, 74.
Culm, 423.
Culmiferous series, 424.
Culminating points of mountain chains,
45.
Cumbrian rocks, 440.
Currents of air, 55.
of water, effect of, 74.
, marine, account of, 64.
, produced by tidal action, 75.
Curved crystals, 149.
Cutch (India), oolites of, 388.
, oolitic coal-fields of, 399.
Crystalline form, 131.
- limestones, generally the best
for building, 479.
rocks of Southern India, 544.
or igneous rocks, account of,
249.
, views of, 447.
, protruded through others,
296.
, of Tertiary epoch, 367.
, of Secondary epoch, 397.
, Palaeozoic (of Devonian pe-
riod), 435.
570
ALPHABETICAL INDEX.
Crystallography, 130.
Crystals, general notice of, ] 30.
, modified forms of, 148, 149.
, unsymmetrical, 150.
Cyathocrinites planus, 424.
DAILY oscillations of the baromer, 5 1 .
Dana, Mr., his Manual of Mineralogy re-
ferred to, 166.
, his analyses of corals, 324.
, his account of marbles, 257.
Danube, delta of, 86.
, Miocene beds of the valley of,
357.
Darley-dale stone, account of, 251.
Darwin,Mr., his account of coral reefs,
90.
, on depression in coral areas, 127.
Davy lamp, 491.
Dax, Miocene beds of, 356.
Dead Sea, depression of, 38.
Dean forest, its ironstone, 494.
Debacles, effects of, 75.
Declination of the magnetic needle, 20.
Decomposition by heat, 18.
by light, 17.
of building stones, 478.
Deep draining, 461.
Degradation of granite by weathering, 71.
De la Beche's, 6ir H. T., account of con-
cretionary structure, 280.
Deltas, 8487.
Density of the atmosphere, 49.
, of the earth, 23.
, of water, when greatest, 17.
Denudation, effects of, 290.
, valley of, filled
up
with
horizontal deposits, 295.
Depressed areas, 38.
Depression in coral districts, 127.
Deposits, their relation to the circum-
stances of accumulation, 312.
, of matter held in solution by
water, 88.
Depth of the Atlantic, 29.
of the Pacific, 31 .
of Cornish mines, 504.
of currents, 68.
of shafts, 485.
of soils, 457.
of veins, 305.
Derivation of chemical terms, 7.
of soils from the rock, 456.
Descriptive Geology, 245.
Deserts, 41.
Destructive action of atmosphere, 70.
Destructive force of waves, 77.
Detritus, distribution of, 88.
removal of, by freshets, 74.
Devonian series, 430, 433.
Devonshire, culm-measures of, 424.
, middle palaeozoic rocks of,
433.
Dew, deposit of, 54.
Diadema seriale, 390.
Dia-magnetic bodies, 19.
Diamond rock of India, 543.
Diamonds, account of, 173.
, mode of exploring for, 366.
Dichroism, 159.
Dieppe, water obtained at, 469.
Diluvial action, want of evidence of any
extensive deluge, 344.
Diluvium, 345.
Dimetric system (Mineralogy), 135,139.
Dimorphism, 131, 150.
Dinotkerium, lower jaw of, 355.
Diorite, 274.
Dip of the magnetic needle, 20.
of beds, 291.
, reversal of, 298.
Direction of veins in Cornwall, 306.
Dirt-bed of Portland, 381.
Displacements of rocks, 291.
Distribution of coal, 409.
of earthquakes, 102.
of fossils, laws of, 315.
of land, its influence on
temperature, 58.
of land and water, 23.
of oceans during the Terti-
ary epoch, 369.
-of oceans during Secondary
epoch, 398.
of oceans during the Palaeo-
zoic epoch, 447.
of organic beings, very diffe-
rent in ancient times, 317.
of species, less limited
at
earlier periods, 316.
of mineral veins, 306.
of marine animals, 94.
of volcanoes, 117.
Divisibility of matter, 6.
Disturbance, systems of, during the Ter-
tiary epoch, 368.
, during the Se-
condary epoch, 397.
during the Pa-
laeozoic epoch, 445.
Disturbing forces usually manifest where
mineral veins occur, 307.
ALPHABETICAL TABLE.
571
Dodecahedron, 137.
Dolomite, 183,259, 402.
Forchhammer's theory of, 404.
Donetz, coal-field of, 418.
Doubtful stratification, 298.
Downton castle, Silurian rocks of, 436.
Drainage, nature of, 460.
' : , areas of, 33.
of mines, 502.
Drift, accounts of, 486.
, transported, 346.
currents, 64.
period, notice of, 345.
, fossils of, 351.
Dudley limestone, 438.
Dufrenoy,M., his method of classification
of minerals chiefly adopted, 170.
Dumb furnace, 489.
Dundry, Inferior oolite of, 387.
Dunes'(sand) 71.
Duration of coal in various districts, 411.
Dwina, blocks on the banks of, 82.
Dykes and faults, 294.
EARTH, form of, 23.
Earthquakes, nature of, 101.
Earth- wave, its rate of progress, 109.
Earthy minerals used in construction,
477.
Edges of crystals, 133.
Effervescence, minerals determined by,
165.
Ehrenberg, M., his account of infusorial
animalcules in river mud, 92.
, on infusorial animalcules
in volcanic ash, 115.
Elasticity of various rocks, 108.
Elbe, infusorial mud at the mouth of, 93.
Elective affinity, 13, 14.
Electric discharge, destruction of rocks
by, 71.
Electricity, nature of, 19, 160.
Electric tension of the atmosphere, 54.
Electro-negative and electro-positive ele-
ments in minerals, 169.
Elementary substances, table of, 8.
Elements, number that combine in simple
minerals, 168.
Elevated plains, 42.
Elevation, valleys of, 292.
-, system of, during the Tertiary
epoch, 368.
ary epoch, 397.
zoic epoch, 442.
-, during the Second-
-, during the Palseo-
Encircling (coral) reefs, 91.
Encrinital stems, 325.
Encrinites moniliformis , 395.
Endogenous rocks, 274.
England, earthquakes in, 103.
, system of elevation of the north
of, 456.
Eocene period, 339, 358.
363.
Equatorial current of the Pacific,65.
Equator, magnetic, 20.
of heat, 60.
Equivalents, chemical, 7, 8.
Eroding action of water, 73.
Erratic blocks, 345.
Erupted rocks, 274.
Eruptions of hot water, 97.
of mud, 96.
, volcanic, of Sumbawa, 116.
Essential minerals in rocks, 246.
Estuaries, tidal influence in, 78.
Etna, view and profile of, 115.
Euomphalus pentangulatus, 329, 424.
Euphotide, 274.
Europe, volcanoes of, 118.
European coast, temperature of, 59.
Euxine, or Black Sea, 29.
Evidence of fossils in Geology, 310.
Examination papers in Geology, 513.
Expansion of freezing water, 80.
produced by heat, 17, 302.
of water on cooling down below
a certain temperature, 18.
Explosive atmosphere, nature of, 492.
Extension of land, 25.
Extent of earthquake disturbance, 104.
Extinct species of animals and vegetables,
law of, 315.
vegetables, account of, 320.
volcanoes, 123.
FACTS of Geology most important to be
known, 454.
Falls of Niagara, 73.
False stratification, 299.
Faults, general account of, 294.
in coal-measures, 408, 482.
, results of in drainage, 462.
Fault-springs, 465.
Fauna, British carboniferous, 424.
Felspar, 192.
Fens, drainage of, 461.
Ferns, the fossil fronds of, 320.
Fertility of soils, 457.
Fibrous structure of schists, 263.
Fingal's Cave, Staffa, 125.
572
ALPHABETICAL INDEX.
Finisterre, Cape, rapid advance of dunes
at, 71.
Fire in coal-mine, use of faults to stop
it, 483.
Fire-clay, 260, 414.
Fire-damp, 491.
Fish, fossil, from Eocene deposits, 364.
Fishes, fossil, of Lias, 392.
Fissile character of schists, 262.
Fissures in clay, 261.
resulting from earthquakes, 108.
Flames issuing from the earth, 95.
Flenu coal, 416.
Flint, 176.
Floods, mechanical action of, 74.
Flora of the brown coal, 357.
Fluid condition of matter, 6.
Fluxes, use of, in blow-pipe analysis, 167.
Foliation resembling stratification, 288.
Folkstone, Gault of, 376.
Fontainebleau sand, 359.
Footsteps, fossil, 318.
Foraminifera, fossil remains of, 322.
Foraminiferous limestones of the Newer
cretaceous period, 373.
Forbes, Prof. E., his account of the dis-
tribution of marine animals, 94.
Forbes, Prof. J., his account of glaciers,
80.
Force of the tide- wave, 63.
Forest-marble, 385.
Formation of soils, 455.
Formations, geological, their relative value
in agriculture, 459.
Form, importance of, in minerals, 1 30.
of atoms, 6.
of the earth, 23.
Forms of matter, 6.
Fossiliferous and unfossiliferous rocks,
333.
rocks, subdivisions of, 336.
Fossilization, process of, 153, 311.
Fossil remains of vegetables, 319.
Fossils in clay-rocks, 264.
necessary in classification, 310.
, nature of, 31 1.
, value of, in Geology, 313, 314.
, laws of distribution of, 315.
, presence of, indicates a lapse of
time, 309.
rare in sand-rocks, 253.
of the Recent period, 345.
of the Drift period, 351.
of Newer tertiary period, 352.
of lignite, 353.
of Middle tertiary period, 355.
Fossils of Middle tertiaries in India, 358.
of the Eocene period, 363.
of the Chalk, 372.
of Upper greensand and gault,
376.
of Lower greensand, 378.
of Weald, 380.
of Upper oolites, 382.
of Great oolite, 387.
of Lias, 391.
of Trias, 395.
of Magnesian limestone, 404.
of Coal-measures, 407.
of Carboniferous limestone, 424.
of Devonian period, 431.
, Silurian, 438, 443.
Fox, Mr. R. Were, his experiments on
the lamination of clay, 247.
Fracture of minerals, different kinds,
155.
of beds on elevation, 293.
France, Tertiaries of, 356, 360.
, Chalk needles on coast of, 77.
, Cretaceous rocks of, 373, 376,
378.
, Upper oolites of, 382.
, Lower oolites of, 387.
, Permian deposits of, 405.
, Carboniferous deposits of, 417.
, Central, volcanoes of, 124.
Freezing water, expansion of, 80.
Freshets, mechanical effects of, 74.
Freyberg, systems of veins in, 305.
Friction, a means of producing electricity
in minerals, 161.
Frigid zones, rain-fall in, 54.
Fringing (coral) reefs, 91.
Frostburg coal-field (America), 420.
Fulgurites, nature of, 72.
Fuller's earth, 189,260,386.
Furnaroles, 96, 110.
Funzie, fulgurites at, 72.
Furnace ventilation, 489.
Fusion of rocks Tby lightning, 71.
GALVANISM, 18.
Ganges, delta of, 87.
Garnet, 189.
Garonne, beds of the basin of, 356.
Gaseous condition of matter, 6.
exhalations, 96.
Gases, important in the composition of the
earth, 10.
Gas, explosive, 492.
Gault, 375.
Geneva, delta in the Lake of, 85.
ALPHABETICAL INDEX.
573
Geognosy, definition of, 2.
Geographical distribution of veins, 306.
Geographical position, influence of, on
climate, 52.
Geography, definition of, 2.
Geologist, essential knowledge required
by, 333.
Geology, definition of, 2.
, descriptive, 245.
, practical, 453.
of India, 532.
Germany, Tertiaries of, 353, 357.
J Lower oolites of, 388.
, Central, coal-fields of, 417.
Geysirs of Iceland, 97.
Giallo antico, 257.
Gibraltar stone, 258.
Glacial beds, 346.
Glaciers, account of, 80.
Glacio-fluviatile action, 83.
Gneiss, 267.
Gold, 226.
deposits, 498.
Goniometers, 146.
Grain of rocks, defined, 282.
Granite, account of, 269.
, weathering of, 71.
, veins of, 273.
Granular texture of minerals, 154.
Graphite, 1/3.
Grauwacke or Greywacke, meaning of the
term, 335.
schists, 262.
Gravel, account of, 345.
, large quantities removed by
floods, 74.
, conveyed by ice, 82.
Gravitation, force of, 12.
Great Oolite, 385.
Greece, Newer tertiaries of, 352.
Greensand series, upper, 374.
, lower, 377.
Greenstone, 266, 274.
Crenelle, Paris, sinkings of the deep
well there, 4 7 6.
, temperature of the water in the
well at, 24.
Gres bigarre, 396.
de Vosges, 396, 397.
Greywacke. See Grauwacke.
Grind of the Navir, 78.
Groups of rocks, best mode of studying,
249.
Gryplnea arcuata^ 328.
virgula, 382.
Guadaloupe, human remains at, 394.
Gulf-stream, 66.
Gypseous beds of Paris Basin, 360.
Gypsum, 258.
HAINAULT coal-field, 416.
, system of elevation of, 447.
Hampshire basin, 359.
Hardness of minerals, 162.
of veinstone, 506.
Harwich, cement stones in London clay
of, 362.
Hastings sand, 379.
Headon Hill sands, 361.
Heat, account of, 1 7.
, development of electricity by,
161.
, equator of, 60.
, effect of, in modifying mineral sub-
stances, 248.
, effect of on sand, 250.
, quantity of, received in the earth,
58.
, use of, in determining minerals,
166.
Heddon stone, account of, 251.
Height, influence of, on the pressure of
the atmosphere, 50.
of continents, 43.
of mountains, 44.
of the snow line, 52.
of waves, 63.
Hemi-hedral forms, 137, 14], 142, 143.
Hemitropes, 149.
Henry, T. H., Esq., his analyses of
American Oolitic coal, 400.
Herefordshire, Old red sandstone series
of, 431.
Hexagonal dodecahedron, 141.
system in Mineralogy, 135,
141.
Hexahedron, 136.
Hills, 39.
Himalayan mountains, height of the
chain, 45.
-, elevation of, 369.
Hippurites bi-oculata^ 327.
organisans^ 372.
History of successive periods, 449.
Hornblende, 197.
rock, 266.
schist, 266.
Hornitos, 96, 110.
Hot springs, 99.
Huddlestone, stone of, 259.
Hudson's Bay, 30.
Human remains found fossil, 344.
574
ALPHABETICAL INDEX.
Humboldt's account of crystalline rocks,
274.
Hundsruck, system of elevation of, 455.
Hungary, earthquakes in, 103.
Hunt, Mr., his experiments on the lami-
nation of clay, 247.
Hurricanes, 56.
Hydrogen gas as a material of the earth's
crust, 10.
Hypersthene rock, 274.
Hypogene rocks, 274.
Hythe, lower greensand of, 377.
ICE, density of, 1 7.
Ice-bergs, account of, 81 , 82.
Iceland, account of a great volcanic erup-
tion in, 116.
, geysirs of, 97.
spar, its double refraction, 160.
Ideal crystal, 134.
Igneous, or crystalline rocks, 249,^
Illinois coal-field, 420.
Imitative shapes of minerals, 154.
Impressions of animals found fossil, 311.
Improvement of barren soils, 458.
of land by drainage, 462.
Inclined strata exhibited by denudation,
291.
not necessarily disturbed,
299.
Index of minerals, 237.
India, drift of, 349.
, general account of the geology of,
532.
, cotton soil of, 343.
, kunkur of, 349.
, Miocene tertiaries of, 359.
,lateriteof, 544.
, diamond deposits in, 366.
, Oolitic coal-fields of, 399.
, coal-fields of, 428, 533.
Indian Ocean, account of, 32.
, depression of its bed, 127.
, storms of, 57.
Indiana, U.S., coal-field, 420.
Induration of dunes, 71.
Inferior oolite, 386.
Influence of minute animals on rocks, 92.
Infusorial animalcules, fossil remains of,
321.
, their influence on
rocks, 92.
-, found v\ith vol-
canic products, 1 15.
Inland seas of the Atlantic, 29.
of the Pacific, 32.
Intensity, magnetic, 20.
Invariable temperature, stratum of, 60.
Ireland, mud torrents in, 75.
, carboniferous rocks of, 426.
, coal-fields of, 415.
, Devonian rocks of, 433.
Iridiscence, 159.
Iron and iron ores, 203.
Iron mines, 493.
, production of, in various countries,
429.
Ironstone of Carboniferous rocks, 429.
Irrawaddi river, Tertiaries of, 357.
Islands, 46.
Isle of Wight, Eocene Tertiaries of, 361.
, chalk needles of, 77.
Isochimenal lines, 59.
Isodynamic lines, 20.
Isomerism, 153.
Isomorphism, account of, 131, 151.
-, its importance in classifica-
tion, 170.
its importance in geological
metamorphoses, 276.
-, polymeric, 152.
Isotheral lines, 59.
Isothermal lines, 59.
Itacolumite, 252.
Italy, earthquakes in, 103.
JAMAICA, changes of level at, 122.
Jet, 389. [462.
Johnston, Mr., his remarks on drainage,
Joints, account of, 300.
in prismatic masses, 284.
in schists, 263.
Jorullo, volcano of, 109.
Julian Alps, elevation of, 368.
Jupiter Serapis, changes of level of, 121.
Jura mountains, elevation of, 368.
valleys of elevation in, 292.
Jurassic series, 380.
KAOLIN, 188, 260.
Kelloway rock, 384.
Kentish rag, 377.
Kenton stone, account of, 252.
Kentucky coal-field, 419.
Keuper, account of, 394.
Kiesel-shiefer, 426.
Kilkenny marble, 257.
Kimmeridge clay, 382.
coal, 399.
Kirghis steppe, 40.
Kunkur, of India, 349.
Kupfer-schiefer, 404.
ALPHABETICAL INDEX.
575
LABYRINTHODON, account of, 396.
Lagoons in coral islands, 91.
Lake, bursting of a, 75.
Lakes, account of, 37.
and rivers, area covered by, 27.
Laminated structure, 279.
texture of minerals, 154.
Lamination, 277, 287-
of schists, 262.
produced in clay by electric
action, 247.
Lancashire coal-field, 412.
Land and sea breezes, 55.
, phenomena of, 22, et seq.
, form of continental masses of,
25.
, condition of, during the Tertiary
epoch, 367.
, its value estimated with reference
to geological structure, 460.
springs, 465.
Landslips, destroying effect of, 78.
Lapis-lazuli, 200.
Laterite, account of, 544.
Lauder, Sir T. D., his account of floods
in Scotland, 74.
Lava, nature of, 111
, current of, in Nassau, 123.
, eruption of, 116.
Laws of distribution of fossils, 315.
of representation and grouping of
animals and vegetables, 312.
Lead, 216.
Leaves, fossil remains of, 320.
Lehm, or loess, of the Rhine, 342.
Length of mineral veins, 305.
Letten, 403.
Lias, 388.
Liassic system, 388.
Liege coal-field, 416.
Light, nature of, 16.
, action of, on minerals, 248.
Lighting, methods of in mines, 491.
Lightning, fusion of rocks by, 71.
Lignite, account of, 174.
, formation of, 321.
of Germany, 353.
Lime-group of rocks, 253.
Limestone, account of, 182.
, analyses of, 256.
deposited from springs, 88.
9 abundance of coral remaini
in, 324.
-, liassic, 39.
, percolation of water through
467.
imestone, magnesian, 183, 259.
soils on, 459.
jimestones, texture of, 253.
used in building, 477.
Limitation of the number of mineral spe-
cies, 168.
of coal to Palaeozoic period, 481.
Limits of the atmosphere, 49.
of original forms in minerals, 130.
of mining districts, 308.
Limnea longiscata, 356.
Lisbon earthquake, account of, 104.
Llandeilo flags, 441.
Llanos, 41.
Lodes, or metalliferous veins, 497.
Loess of the Rhine, 342.
Loire, beds of the basin of, 356.
, coal-field of the basin of, 417.
London clay, 361.
, supply of water in rocks near,
470.
Long-wall method of coal-working, 482.
Lower greensand series, 377.
lias shale, 390.
new red sandstone, 405.
Ludlow rocks, 436.
Ludus Helmontii, 280.
Lusitanian character of the Coralline crag,
355.
Lustre of minerals, 158.
Luxemburg, lias of, 39 1 .
Lyme Regis, lias of, 389.
MACIGNO, 374.
Macles, 149.
Macculloch, Dr., his account of concre-
tionary structure, 278.
account of prismatic
structure, 28 .
account of schists, 262.
account of gneiss, 269.
his account of primary
limestone, 255.
, his account of quartz
rock, 251.
account of granite, 271.
Magnesia, a constituent of soils, 459.
Magnesian limestone, 183, 259.
system, 401.
Magnetic equator, 20..
force, its action on light, 16.
metals, list of, 18.
poles, 20.
storms, 22.
Magnetism, nature of, 18.
, metals acted on by, 161.
576
ALPHABETICAL INDEX.
Mallet, Mr., his account of the order of
earthquake phenomena, 108.
Malm rock, 375.
Mammaliferous crag, 350.
Manchester, coal of, 412.
Mandelato marble, 257.
Manganese 202.
Mansfield stone, account of, 252.
Mantell, Dr., his account of Wealden
formations, 380.
Manures, mineral, 457.
Maps, geological, their use to the agricul-
turist, 455.
Marbles, account of, 182,253, 257.
Marine animals, distribution of, 94.
currents, account of, 64.
produced by tidal action, 75.
Mariner's compass,! 8.
Marls, account of, 265.
of the Isle of Man, 342.
Marlstone, 390.
Marnes irisees, account of, 394.
Maryland coal-field, 420.
Massive marbles, 255.
Mastodon, tooth of, 331 .
Measure, combining, 7.
Mean direction of the wind, 56.
height of continents, 43.
Mechanical action of rocks, 72.
displacements of rocks, 291.
force of the tide wave, 64.
or aqueous rocks, 249.
position, importance of, in
geological classification, 310.
Mediterranean sea, 29.
, Newer tertiary beds of,
352.
Megalichthys Hibberti. 407.
Megalodon cucullutus, 328.
Melaphyre, 274.
Mercury, 215.
Metallic oxides, analyses of, 233.
, their use in vegetation,
457.
silicates and carbonates, analyses
of, 232.
sulphurets, analyses of, 234.
Metalliferous veins, 497.
Metals found in sand-rocks, 252.
in Devonian rocks, 435.
Metal tubbing, 485.
Metamorphic* rocks, 249.
structure, 286.
Metamorphosis of rocks, 276.
assisted by the removal
of water from rocks, 303.
Meteoric action on rocks, 71.
Meteorites, 203.
Meteorology, nature of, 49.
Meteors, aqueous, 48.
Mexico, Gulf of, 30.
Mica, 198.
Mica-schist, 266.
Millstone grit, 423.
Minchinhampton oolites, 387.
Mineral character, importance of in geo-
logical classification, 310.
contents of soils, 457.
species, causes of the limitation
of, 168.
springs, 99.
veins, account of, 301.
-, systems of, in Cornwall
and Freyberg, 305.
Mineralogical character of granite, 272.
Mineralogy, object of, 129.
Minerals, their characteristics, 130.
, alphabetical index of, 237-
, most abundant species of, 169.
essential in natural combina-
tions, 246.
analyses of those forming rocks,
268.
from Tertiary deposits, 365.
in clay rocks, 264.
in limestone rock, 258.
in granite, 273.
in gneiss, 269.
Mines, as distinguished from quarries,
480.
, depth of, 504.
, temperature of, 24.
of coal, 481.
of salt, 495.
of iron, 493.
of metallic ores, 497.
Mining districts, limits of, 308.
operations, 480.
for coal, 481.
records, 505.
Miocene, or Middle tertiary period, 339.
deposits, account of, 354.
Mississippi, changes of level in the ral-
leyof, 122.
-. , delta of, 87.
, deposits in the valley of, 343.
, mud deposits on the banks
of, 85.
Missouri coal-field, 421.
Mitscherlich,his experiments on changes
in minerals, 248.
Mixture, nature of, 10, 14.
ALPHABETICAL INDEX.
577
Modifications of land, affecting marine
currents, 68.
of marine currents, G7.
Modifying minerals in rocks, 247.
Moisture of the air, 53.
Molasse, of Switzerland, 356.
Molecules, their nature, 5.
Mollusca, fossil remains of, 325.
Molybdenum, 221.
Monk-Wearmouth pit, 485.
Monoclinic system (Mineralogy), 135,
144.
Monometric system (Mineralogy), 135.
Monsoons, 56.
Monte Bolca, fossiliferous Eocene lime-
stone of, 362.
Monte Viso, system of elevation so called,
397.
Monthly oscillations of the barometer,51.
Montpellier, Miocene beds near, 356.
Moraines, or gravel heaps on ice, 81,82.
Motion of water and waves, 61.
Mountain chains, 43.
Mountain limestone, 423.
Moving water, mechanical effect of, 76.
Mud, deposition of, 89.
deposited by floods, 84.
, eruptions of, 96.
of the Nile, analyses of, 8 6.
, rate of sinking in moving water,
68.
Mudstones, Silurian, 437, 438.
Mud-torrents, 75.
Mud- volcanoes, 97.
Murex cdveolatus, 329, 352.
Muschelkalk, 395.
NASSAU lignites of 353.
Navir, grind of the, 78.
Neacomian beds, 378.
Needle, magnetic, 19.
Needles of chalk on the French coast, 77.
Nerbudda coal district, 536.
Nerinaea Goodhallii, 329.
Nerinaean limestone, 384.
Nero-antico marble, 257.
New Brunswick coal-field, 421.
Newbold, Capt., his notices of the geo-
logy of India, 543.
Newcastle, analyses of coal of, 41 1.
, account of coal-field, 410.
, coal-workings at, 488.
Newer tertiary period, 351.
Newfoundland, carboniferous system of,
428.
New red-sandstone system, 393.
New Zealand, recent deposits of, 344.
coal-fields, 421,428.
Niagara, falls of, 73.
Nice, Eocene nummulitic rock near,362.
Nickel and its ores, 210.
Nile, delta of, 85.
Nismes, natural spring at, 469.
Nitrogen gas, as a material of the earth's
crust, 10.
Nodules, structure of, 280.
Noise accompanying earthquakes, 102.
Non-aluminous silicates, analyses of, 231.
Normandy, needles on coast of, 77.
, Oolites of, 387.
North Pole, temperature of, 59.
Norway, pierced rock in, 469.
, Silurian rocks of, 442.
Norwich crag, 350.
Notation, chemical, 7, 15.
Nova Scotia coal-field, 421.
Nticulapectinata, 376.
Nummulite limestone, 362.
Nummulites, account of, 374.
OASES of the desert, 41.
Oblique prismatic system (Mineralogy),
135, 144.
Oceanic deltas, 86.
Oceans, area of, 27.
, distribution of, during the Ter-
tiary period, 369.
, distribution of during the Secon-
dary period, 398.
-, distribution of, during the Palaa-
ozoic period, 447.
Octahedral system (Mineralogy), 135.
Odour of minerals, 161.
Oeningen beds, 353.
Ohio coal-field, 420.
Old red sandstone series, account of, 430.
9 analyses of marls
from, 281.
Older Tertiary period, 358.
Oolite, account of, 255.
Oolites used in building, 477.
Oolitic series, 380, 385.
coal-fields, 388, 399.
magnesian limestone, 403.
marble, 258.
Opalescence, 159.
Optical properties of minerals, 1 55.
Ores, mode of extracting, 505.
Organic contents of lime rocks, 254.
influence in deposits, 89.
in the formation of rocks,
248.
P P
578
ALPHABETICAL INDEX.
Organic remains, value of, 94.
-, nature of" found fossil,
310,318.
presence of, indicates
lapse of time, 309.
rare in sand rocks, 253.
Organisation, greater simplicity at early
periods assumed, 317.
Orthis orbicularis, 326 .
Orthoceras conica, 330.
lateralis; 424.
Oscillating waves, 62.
Oscillations of the barometer, 51 .
Os, or gravel hill, 347.
Ostrea carinata, 376.
Marshii, 328.
Outcrop of beds, 291.
of coal, 483.
Outlier from double anticlinal axes, 293.
Outliers, 295.
Oxford clay, 384.
Oxides, abundance of in nature, 169.
, metallic, analyses of, 233.
Oxygen gas, its importance as a material
of the earth, 10."
PACIFIC OCEAN, accounts of, 30.
, currents of, 65.
, depression of its bed, 1 27
-, trade winds of, 56.
Paleontology, its object, 332.
Palteotkerium, skeleton of, 360.
Palaeozoic series, definition of, 335.
period, account of, 449.
deposits, general account of,
443.
system, subdivisions of, 401.
epoch, newer, 401.
, middle, 430.
, older, 4 35.
Palma, Isle of, 113.
Palmacites Lamanonis, 357.
Palamow, coal of, 536.
Pampas, 41.
Panel working, 488.
Paper coal, 353.
Paragone marble, 257.
Parian marble, 258.
Paris basin, deposits of, 359.
Parknook stone, 259.
Patagonia, recent deposits there, 343.
, recent elevations on the shores
of, 126.
Peat moss, 342.
Pecopteris aquilina, 320.
Pecten Lugdunensis, 391.
Pennsylvania coal-field, 420.
Periodical floods, effects of, 74.
winds, 55.
Periods, account of the principal, 449.
Permanent result of earthquake action,
107.
Permian system, 401.
Pentagonal dodecahedron, 137.
Pentamerus Knightii, 437.
Petrifaction, 153.
Phascolotkerium, jaw of, 386.
Phenomena of an earthquake, 108.
Phosphorescence, 160.
Phosphorite, 1 84.
Physical features of a volcanic district,
113.
Pictou coal district, 421.
Pipe-clay, account of, 260.
at base of lignites, 353.
Planer limestones of Germany, 374.
Plagiostoma giganteum, 39 1 ."
spinosum, 372.
Plains, elevated, 42.
, low, 39.
Plastic clay, 189,362.
Plaster of Paris beds, 360.
Plateaux, elevated, 42.
Platinum, 228.
Pleistocene rocks, 339.
Plesiomorphism, 150.
Plesiosaurus, outline of, 393.
Pleurotomaria conoidea, 387.
Plicatula spinosa, 391.
Pliocene period and deposits, 339, 351 .
Plumbago, 173.
Plutonic rocks, 274.
Plymouth limestone, 433.
Po, Delta of, 84.
Polar force, nature of, 19.
of magnetism, 18.
Polar seas, 32.
Polarization of light, 16, 160.
Poles of cold, 60.
, magnetic, 20.
Polychroism, 159.
Polymeric isomorphism, 152.
Polymorphism, 150.
Polzivera di Genoa, a marble, 257.
Pondicherry beds, 378.
Porcelain clay, 188, 260.
Porphyritic rocks, composition of, 270.
structure, 286.
veins, 273.
Porphyry, 267.
Portland stone, 381.
Portlandian group, 38 1 .
ALPHABETICAL INDEX.
579
Portor marble, 257.
Position of rocks, phenomena of, 287.
Post-tertiary deposits, 340.
Potter's clay, 260.
Practical geology, 453.
Prairies, 42.
Pressure, atmospheric, 51.
Prevalent winds, 56.
Primary formations, 335.
limestone, 255.
Primitive rocks, 274.
Principles of classification explained, 333.
of mining, 480.
Prismatic structure, 28L
system (Mineralogy), 135,142.
Prisms, nature of, 283.
Productive capacity of coal-fields, 411 et
seq.
Prodiictus aculeatus, 404.
Protogine, 271.
Proximate elements, 168.
Psammite, 434.
Pseudo-bedding, 283.
Pseudomorphism, 152.
Pseudo-volcanoes, 97.
Pterodactyl, figure of, 392.
Pudding-stones, 252.
Puddingstone marble, 258.
Purbeck beds, 380.
Purity, relative, of water, 475.
Pyrenees, height of, 45.
, period of elevation of, 368.
Pyritous clay in lignite, 353.
QUADER SANDSTONE of Germany, 373,
378.
Quality of water, 474.
Quantitative affinity, 15.
Quantity of air introduced in to coal-mines,
490.
of carbonate of lime in salt water,
254.
of coal in various coal-fields,
411,412,413.
of water in chalk, estimate of,
473.
Quaquaversal dip, 291.
Quartz, 176.
crystal, measurement of, 131.
rock, 251.
veins, universal, 304.
Quartzite, 251.
Quartzose conglomerate of Old red sand-
stone, 431.
Qtiartzosc porphyry, 274.
RADIATKD animals, fosil remains of, 325.
Rain, the source of water in rocks, 468.
proportion of, reaching the sea by
rivers, 464.
Rain fall, amount of, 54.
, greatest in mountain districts,
459.
Rainless districts, 36, 41.
Rain water, supply of alkalies to soils by
means of, 447.
Raised beaches, 126, 340.
Range of barometric pressure, 52.
of earthquake action, 107.
Rapid advance of sand hills, 71.
streams, slope of their bed, 75.
Rauwacke, 403.
Reaction of the interior of the earth on
its exterior, 95.
Records, mining, 505.
Red crag, 352.
Reflecting goniometer, 1 46.
Refraction of light in minerals, 1 59.
Regular system (Mineralogy ), 1 35, 136.
Regur, or cotton-soil of India, 343.
RennelPs current, 67.
Replacement in crystals, 134.
Representation of species explains the
absence of certain genera, 317.
Reproductive effects of aqueous action, 84.
Reptilian remains of the Eocene period,
364.
of lias, 393.
Repulsion, force of, 12, 17.
Result of earthquake action, 107.
Reversion of dip, 298.
Rhine, delta of, 86.
, slope of its stream, 75.
, lehm or loess (silt) of, 342.
, system of elevation so called,
397.
, volcanic district of, 123.
Rhombic system (Mineralogy), 135,
142.
Rhombohedron, 141.
Rhone, delta of, 86.
, its slope, 75.
Richmond, Virginia, U.S., oolitic coal-
field of, 388.
Ridges, principal, 45.
River basins, 33.
River courses, swept out by floods, 73.
River deltas, 84.
River drainage of the Atlantic, 29.
River systems, 32, 34.
Rivers and lakes, area covered by, 27.
Roach Abbev stone, 259.
580
ALPHABETICAL INDEX.
Road-making, necessity of drainage in,
463.
Rock, its meaning in Geology, 245.
Rock-salt, mines of, 495.
Rocks, how grouped, 250.
, general principles of the classifi-
cation of, 309.
, table of classification of, 336.
, kinds of, that contain fossils, 314.
, absorbent power of, 468.
, degradation of, to form soils, 456.
, their retentive powers with regard
to water, 465.
Rossberg, fall of the, 80.
Rosso- antico marble, 257.
Rostellaria pes-pelicani, 355.
Rothe-todte-liegende, 405.
Rowley rag, experiments on, 275.
Rudistes, extinct species of, 327.
Ruhr, coal-field of the, 418.
Running water, action of, 72, 74.
, arrangement of material
in, 88.
Russia, Pliocene deposits of, 354.
, coal-fields of, 4 18.
-, Carboniferous rocks, 426.
, Permian deposits, 405.
, Devonian beds, 434.
, Silurian rocks, 441.
Saare-bruck, coal-field of, 417.
Safety lamps, 491.
Sahara, of Africa, 41.
Saline ingredients in the ocean, 27.
in the Dead Sea, 38.
Salts required in soils. 458.
Salt deposits in Cheshire, 393.
Salt mines, account of, 495.
Salt, rock, description of, 179.
Salses, 96.
Sand, way in which it becomes a rock,
i 250.
dunes, advance of, 71.
group of rocks, 250.
pipes fused by electricity, 71.
, barren soils on, 458.
, percolation of water through, 466.
Sandstones, analyses of, 252.
-, causes of decomposition of,
478.
considered with reference
to water, 475.
Santorin, map and section of, 114.
Saturation of rocks by water, 468.
Savannahs, 42.
Scaglia, 374.
Scandinavia, earthquakes in, 1 03.
, elevated beaches on
coast of, 126.
-, raised beaches in, 340.
the
Scar limestone, 426.
Schist, 261, 266.
Schuylkill coal-field, 420.
Scotch coal-fields, 414.
Scotland, floods in 1829, 74.
, earthquakes in, 1 03.
, ironstone of, 494.
, Oolitic rocks of, 384.
, Old red sandstone series of, 432.
Sea, solid contents of, 27.
, undermining action of, 75.
Sea-eggs, fossil remains of, 325.
Sea-urchins, extinct species of, 325.
Seas, greater extent in ancient times in
northern hemisphere, 317.
Season, influence of, on earthquakes, 102.
Secondary coal-fields, 899.
series defined, 335.
Secondary epoch, general account of, 397,
450.
, rocks and fossils of, 371.
Sections, geological, their use to the agri-
culturist, 456.
Sedgwick, Prof., his account of the sys-
tems of Silurian elevation, 445.
Selenite, account of, 258.
Semicrystalline structure, producing stra-
tification, 288.
Serpentine, 196.
Serpula, figure of, 363.
Sewalik tertiaries of India, 357.
Shaft-sinking for coal, 484.
Shale, account of the rock so called, 260,
261.
, Lower lias, 390.
Shales of coal measures, 407.
Sheets of water in rocks, 468.
Shells, casts of, found fossil, 319.
, effect of, in deposits, 89.
Shetland Isles, action of waves on, 77.
Shoals, effect of tidal action in disturb-
ing, 76.
Solvent power of water, 72.
Shoding, process of, 499.
Shores of the Pacific, 31.
Shropshire coal-field, 413.
Siberia, gold alluvia of, 498.
Sicily, great limestone of, 352.
, salses of, 97.
Sigillaria pacfii/derma, 320.
Silesia, coal-fields of, 417.
Silex, use of, in grasses, 458.
ALPHABETICAL INDEX.
581
Silica, account of, 176.
Silicates, analyses of, 230.
Silt of the valley of the Rhine, 342.
Silurian series, Upper, 435.
, Lower, 440.
Silvas, 39.
Silver and its ores, 224.
Simeto, eroding action of water at, 73.
Simms, Mr., his admeasurement of a
section of Upper cretaceous beds, 376.
Simooms, 57.
Simpler organisation of ancient species
assumed, 317.
Skaptaa Jokul, eruption of, 116.
Slate, 260.
Sline of coal denned, 282.
Slip, or fault, 294.
Slope of running water, 75, 86.
Smalts, 209.
Smith, Mr. W., on canal making, 463.
Snow line, position of, 52.
Soils, formation of, 455.
, improvement of, 458.
Solfataras, 96.
Solid angles, 1 33.
Solid condition of matter, 6.
Solid contents of the sea, 27.
of fresh water, 474.
Solid matter, or mud, contained in the
water of various rivers, 87.
Solnhofen beds, 383.
Sounds heard during earthquakes, 102.
Soundings in the Atlantic, 29.
South America, recent elevations of the
shores of, 126.
Wales coal-field of, 414.
South pole, temperature of, 59.
Southern India, geology of, 543.
Southern connecting current, 66.
Spain, coal-fields of, 418.
, earthquakes in, 103.
Spatangus cor-anguinum^ 326.
retusus, 378.
Species of animals and vegetables, group-
ing of, 312.
of minerals, number of, 170.
Specific gravity of minerals, 163.
Speed of Lisbon earth- wave, 109.
Speeton clay, 378.
Sphenopteris HoBnighausi^ 407.
Spheroidal concretion in rocks, 277.
Spirifer glabra, 326.
undulatus, 404.
Walcotii, 391.
Splitting the air in coal mines, 490.
Sponges, fossil remains of, 321.
Springs, interception of, 463.
, natural, 465.
of hot water, 99.
Square prismatic system (Mineralogy)
135, 139.
Staffa, volcanic rocks of, 125.
Staffordshire coal-fields, 413.
ironstone mines, 493.
, South, coal workings, 488.
Stalactites and stalagmites, 254, 258.
Statuary marble, 258.
State of aggregation of minerals, 155.
Steam coal, 414.
Steppes, 39.
St. Etienne, coal-field of, 417.
Stigmaria ficoides, 407.
Stinkstein, 403.
Stone for building, best kind, 477.
, analyses of, 252, 256,259.
Stonesfield slate, 386.
Stoppings in coal mines, 489.
Storms, 54, 56.
, magnetic, 22.
Stourbridge clay, 260.
Strata, mode of formation of, 288.
Stratification, 249, 287.
, doubtful, 298.
, false, 299.
of schists, 262.
-, its influence on drainage,
461.
Stratified rocks, subdivisions of, 336.
Stratum of invariable temperature, 60.
Streak of minerals, 158.
Stream-currents, 64.
Stream ores, common in some tertiary
deposits, 365.
Stream works, 498.
Striation and polishing of rocks by drift,
348.
Strike of beds, 291.
Structural condition of rocks, its influ-
ence on the condition of mineral veins,
308.
Structure,itsmeaningin Mineralogy, 1 30.
, concretionary, 278.
, prismatic, 281.
, laminated, 285.
, porphyritic, 286.
of minerals, condition of, 154.
of rocks, 277.
observed in accumulations from
running streams, 88.
of a volcanic district, 114.
of granite, 271.
Sub-apennine deposits, 352.
582
ALPHABETICAL INDEX.
Subdivisions of fossiliferous rocks, 336.
of Tertiary epoch, 339.
of Secondary epoch, 371 .
of Palaeozoic epoch, 401.
Sub-Himalayan beds, 358.
Subsidence in volcanic districts, 122.
Subsoil, formation of, 456.
Subterranean drainage, 463.
Succession of operations requiring time in
Geology, 309.
Suffolk crag, 355.
Sulphur, 178.
Sulphurets, metallic, analysis of, 234.
Sumbawa, eruption of, 116.
Sunda island, account of a volcanic erup-
tion in, 116.
Superficial deposits, 339.
Surface beds and deposits, importance of,
339.
Surface water, its course in various for-
mations, 461.
Surveyor, use of Geology to the, 460.
Sussex marble, 379.
Sweden, drift of, 347.
, raised beaches in, 345.
Syenite, nature of, 271.
Symmetry (in Mineralogy), 133.
Synclinal axis, 293.
Systems of elevation of Tertiary epoch,
368.
of Secondary epoch,
397.
of Palaeozoic epoch, 445.
Systems of crystallization, 135.
of mineral classification, 1 70.
TALC, 196.
Talcose schist, 266.
Tarnish, 159.
Taste of minerals, 162.
Tchornozem, or black earth of Russia,
342.
Temperate zones, rain- fall in, 54.
Temperature, mean annual, 58.
of the atmosphere, 52.
of water in the Gulf Stream,
66.
of the earth's interior, 24.
of deep mines, 504.
-, stratum of invariable, 60.
Tennaserim coal district, 537.
Tenare, system of elevation of, 369.
Tension, electric, of the air, 54.
Terelratula digona, 326.
globata, 387.
octoplicata, 326.
TerebratiUa por recta, 431.
sella, 382.
Ternary combinations, 169.
Terrestrial magnetism, 19.
Tertiary series defined, 335.
epoch, rocks and fossils of, 339.
period, account of, 451.
period, elevations during, 368.
rocks of India, 544.
Tetrahedron, 138.
Tetrakis-hexahedron, 137.
Texas, recent deposits there, 343.
Texture of minerals, 154.
of soils, 457.
Thermal springs, table of, 100,
Thermometer, 58.
Thick coal workings, 489.
Thinning out of strata, 288.
Throw, or fault, 294.
Thuringian forest, system of elevation so
called, 397.
Tidal action and currents, combined effect
of, 76.
Tide wave, its mechanical action, 75.
Tides, 62.
Tilestone, 436.
Tilgate beds, 379.
Till, 346.
Timbering of mines, 505.
Time, necessity of, in geological con-
siderations, 309, 310, 313.
Tin and its ores, 218.
Tin-stones of Cornwall, 498.
Torrents produced by floods, 74.
, rapid passage worn by, 73.
Torrents of mud, 75.
Touraine, beds of, 356. '
Tourmaline, 199.
, its electrical peculiarities, 161.
Trachyte, 267.
Trachytic"rocTs of Germany, 124.
Trade wind, 55.
Trafalgar-square, sinkings of the deep
wells near, 476.
Tranquillity of the seas in which Silurian
deposits were made, 445.
Transparency of minerals, 158.
Transition rocks, meaning of the term,
335.
Trap, 267.
Travertin, 254.
Trees, fossil remains of, 320, 321.
Triassic system, 393.
Triclinic system (Mineralogy), 136, 145.
Trigonia alm
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