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 .ALLUVIUM 
 BRICK -EARTH 
 
 GRAVEL. 
 
FIELD GEOLOGY. 
 
 BY 
 
 W. HENEY PENNING, F.G.S., 
 
 Geologist, 
 
 H.M. GEOLOGICAL SURVEY OF ENGLAND AND WALES. 
 
 WITH A SECTION 
 
 PALAEONTOLOGY. 
 
 BY 
 
 A. J. JUKES-BEOWNE, B.A., E.G.S, 
 
 H.M. GEOLOGICAL SURVEY. 
 
 LI p> ii \ n \ 
 
 UN1\ KKS1TY OF 
 
 CALIFORNIA. 
 
 LONDON :z 
 BAILLIEEE, TINDALL, AND COX, 
 
 20, KING WILLIAM STREET, STRAND. 
 PARIS: BAILLIERE. MADRID: BAILLY-BAILLIERE. 
 
 (All Eights reserved.) 
 
Q E 4 5 
 
THIS WORK 
 
 3E0 Qfttciionzttl 
 
 TO 
 
 MAEIANNE, 
 
 THE WIFE OF THE AUTHOR. 
 
PREFACE. 
 
 THE first idea that suggested itself to me, in regard to a 
 work of this kind, was to publish a few plain instructions 
 for drawing geological boundary-lines, a practical matter 
 which seemed to have been somewhat neglected, although 
 it is of considerable importance. 
 
 But there is an almost imperceptible transition from 
 mapping rocks, which appear at the surface of the earth, 
 to tracing those that are beneath, and from defining the 
 extent of a formation to the determination of its history, 
 as expressed in its lithological character and fossil re- 
 mains. 
 
 The idea, therefore, while being realised, expanded 
 to much beyond its original dimensions, still there is 
 scarcely any portion of the book in which the matter 
 might not, with advantage, be enlarged. It has, how- 
 ever, been thought advisable to issue, as it is, this first 
 edition, and leave for a second (should it ever be re- 
 quired) any further extension. 
 
 There are so many subjects of which a knowledge is 
 -an advantage in geological surveying, that it is difficult 
 
VI PEEFACE. 
 
 to say what ought not to be included in a book on Field 
 Geology. The object aimed at has been to include herein 
 those that are absolutely necessary, in as small a com- 
 pass as is consistent with the purpose in view. 
 
 My colleague, Mr. Jukes-Browne, was good enough 
 to undertake the section on Palaeontology, at a time 
 when, unfortunately, his state of health was not as good 
 as could be desired. For this reason the list of charac- 
 teristic fossils following his work was not prepared by 
 him, and it is, perhaps, far from being as complete, and 
 probably as accurate, as it would otherwise have been. 
 
 The new rules for finding direction of true dip, when 
 first published in the Geological Magazine for May 
 1876, gave rise to some useful criticism; it was then too 
 late to make any alteration in the text or the figures,, 
 but a footnote has been inserted to give the resulting 
 modification. 
 
 W. HENBY PENNING. 
 
 CALDECOTE, GAMES. 
 August, 1876. 
 
CONTENTS. 
 
 PACK 
 
 INTRODUCTION 1 
 
 PAET 1. 
 
 GEOLOGICAL MAPPING. 
 
 CHAPTER I. 
 
 MAPPING AND INSTRUMENTS. 
 
 Maps Contour Maps Compass and Protractor Ham- 
 mer, Pick, Spud, &c. Scales Tracing Boundaries 
 General Propositions - 5- 
 
 CHAPTER II. 
 
 MAPPING {continued). 
 
 Examples of Tracing Boundaries Memoranda Travers- 
 ing Symbols Drift Deposits - II 
 
 PAET II. 
 
 SECTIONS. 
 
 CHAPTER I. 
 
 GEOLOGICAL SECTIONS. 
 
 Dip Strike Clinometer To find Direction of Dip To 
 find Amount of Dip Table of Dip, Depth and Thick- 
 nessExposed Sections Notes - - 38 
 
Vlll CONTENTS. 
 
 CHAPTER II. 
 
 HORIZONTAL SECTIONS. 
 
 Datum-level Bench-marks Levelling, ly Aneroid, by 
 Level Level-book Plotting, from Heights Levelling, 
 lyy Theodolite Level-book Plotting, from Angles 
 Filling in Geology Apparent Dip 61 
 
 PART III. 
 
 LlTHOLOGY. 
 
 CHAPTER I. 
 
 DETERMINATION or ROCKS AND MINERALS.. 
 Texture Structure Fracture Lustre Hardness and 
 Effervescence Specific Gravity Reactions in the 
 Wet Way Blowpipe - 87 
 
 CHAPTER II. 
 
 DETERMINATION OF ROCKS AND MINERALS (continued). 
 
 Table of Tests, in the Field, at Home Metals Tests- 
 Microscope Chemical Analysis List of Books of 
 Reference Peculiarities of Structure, Concretions, 
 Sliclcensides Note on Metamorphic Rocks Cabinet 
 Specimens 100 
 
 PART IV. 
 
 PALAEONTOLOGY. 
 
 CHAPTER I. 
 
 Introduction Nature of Fossil Remains Review of Ani- 
 mal Kingdom Mode of occurrence of Fossil Remains 
 Petrifaction - 122 
 
 CHAPTER II. 
 
 Method of Collecting Fossils Examples - - - 133 
 
CONTENTS. IX 
 
 CHAPTER III. 
 
 Preservation, Naming, and Arrangement of Fossils Value 
 of Paleeontological Evidence Evidence of Physical 
 Conditions - - 144 
 
 CHAPTER IV. 
 
 Characteristic Fossils Table of Fossils - - 157 
 
 PART V. 
 
 CHAPTER I. 
 
 Survey of Older Rocks Boundaries and Faults Down- 
 throw Vertical Section Eruptive RocksVeins - 202 
 
 CHAPTER II. 
 
 Geological Generalisation and Practical Results "Water- 
 supply Soils - -214 
 
ILLUSTRATIONS. 
 
 GEOLOGICAL MAP coloured - Frontispiece. 
 
 PAGE 
 
 Figure 1. Compass and Clinometer 7 
 
 2. Protractor, upper side - 9 
 
 3. Hammer, Pick, and Spud, combined - 11 
 
 4. Protractor, under side, as Scale - 12 
 
 , 5. Area Surveyed, First Slip 10 
 
 6. Second Slip 22 
 
 7. Third Slip - 24 
 
 8. Fourth Slip 20 
 
 9. Methods of Traversing - - 30 
 
 10. Clinometer 40 
 
 " I Diagrams for finding Direction of Dip - 43 
 ., 12. 3 
 
 -jo 44 
 
 1) id' 55 55 55 55 
 
 14. Example of finding Direction of Dip, by Dia- 
 
 gram - 45 
 
 " ' | Diagrams for finding Amount of Dip 
 
 17. Diagram for finding Amount of Dip and its 
 
 Direction - 48 
 
 18. Inaccessible Cliff, to find the height of - 80 
 . 19. Horizontal Section - 83 
 
 20. Diagram for finding Apparent Dip - 85 
 
 20cr. Cast and Impression - - 132 
 
 . 21. Area Surveyed Palccozoic Rocks - 204 
 
 22. Section across Fig. 22 210 
 
 23. Vertical Section - - 212 
 
 
LIBRARY 
 
 UNIVERSITY OF 
 
 CALIFOUXIA. 
 
 FIELD GEOLOGY. 
 
 INTRODUCTION. 
 
 IT may fairly be claimed for Geology that its advance 
 has been more rapid than that of any other science. 
 From the time of William Smith the Father of English 
 Geology until now the number of those who take 
 interest in the subject has been steadily increasing. 
 Every year sees the birth of some new periodical 
 devoted to Geological Science ; every list of new books 
 is sure to contain the name of one or more bearing 
 directly or indirectly on the questions with which it 
 deals, and it possesses already a most comprehensive 
 literature. It plays a prominent part in University and 
 and other public examinations, where, until recently, it 
 was all but unknown; and it guides, as it ought to guide, 
 the direction of mining and other practical operations. 
 "With many the study is taken up as an amusement or 
 a pastime, and is found to possess a fascination pecu- 
 liarly its own ; it opens up to the more philosophical 
 student a fair field of investigation ; and presents to all 
 many interesting physical problems for thought and 
 speculation 
 
 As the number of geological students increases, the 
 
 1 
 
FIELD GEOLOGY. 
 
 greater is felt to be the need of a Manual which shall 
 teach the practical procedure in the field and elsewhere. 
 A great majority of the manuals of Geology, although 
 excellent as guides to a theoretical knowledge of the 
 science, do not sufficiently describe the methods of obser- 
 vation in the field. Without such proper method much 
 time is wasted, many results that otherwise would have 
 been valuable are entirely lost, and the student finds 
 that his labours do not yield to him a proportionate 
 amount of beneficial knowledge. 
 
 To facilitate the acquirement of such knowledge, this 
 work has been published not as containing very much 
 that is original, but as embodying in a small compass 
 practical directions and suggestions which are to be 
 found here and there only in more important works. 
 The object has been to bring them with some additions 
 which are the result of practical experience into a form 
 which shall be at once portable and adapted to special 
 reference. 
 
 If we would make a series of drawings that shall shew 
 the geological structure of any district, it is not sufficient 
 that we are versed in theoretical geology, nor even that 
 we can walk into a quarry and say, " This is a Lime- 
 stone," or a "Sandstone" as the case may be and 
 "it belongs to this or that Formation." We must be 
 able to trace out its boundary, to shew the area that it 
 occupies, and to ascertain the angle at which it dips be- 
 neath the surface. When these points are determined 
 in regard to a series of strata, we have a geological Map, 
 or surface projection and aided by our notes, we can 
 construct therefrom a geological Section, which shall 
 shew the underground extension of the rocks, their thick- 
 
INTRODUCTION. 
 
 ness and their relative positions. By its general appear- 
 ance, and by the aid of simple tests in the field, or if 
 necessary, more complicated ones applied to detached 
 specimens at home, we ascertain the kind of rock of 
 which any bed or series of beds consists. By this means, 
 and by the determination of the Fossils collected from 
 such bed or series of beds, we are enabled to assign to it 
 its position as belonging to a certain formation, or 
 possibly even to a definite horizon in such formation. 
 
 Thus we see that, to obtain an accurate knowledge 
 of the structure of a district, to represent and describe 
 its geological features, and to be able to generalise there- 
 from, four distinct and different, although intimately 
 connected, operations have to be performed. The strata 
 which crop out at its surface must be traced, and their 
 boundary laid down upon the map. The dip (if any) 
 and the underground continuation of the beds worked 
 out the character, peculiarities, and geological age of 
 the rocks ascertained, and their fossil contents discovered, 
 determined, and classified. Each will be treated of 
 separately as far as possible, under one of the following 
 heads 
 
 1. Geological Mapping. 
 
 2. Sections. 
 
 3. Lithology (Determination of Rocks). 
 
 4. Palaeontology ( Fossils). 
 
 The directions given in each Part will be simple and 
 elementary, assuming the student to possess a fair book- 
 knowledge of the science, of its theory, of the sequence 
 of the various systems, formations and groups, and of 
 the general succession and range of fossil plants and 
 animals. By giving examples of the method in. its 
 
 12 
 
FIELD GEOLOGY. 
 
 simpler applications, the chances of confusion or mis- 
 apprehension are greatly lessened at the same time 
 suggestive hints are inserted, which indicate, rather than 
 describe, the more detailed and complicated operations 
 and calculations. 
 
 Additional notes are given on the more common 
 Minerals, Metals and their Ores their mode of occur- 
 rence, and the methods adopted for their discovery and 
 utilisation. Also on the Rocks which do not follow the 
 general laws of stratification and arrangement, requiring 
 therefore a somewhat different method of ascertaining 
 and shewing their extent and their relations these are 
 the eruptive and intrusive rocks and the glacial deposits. 
 A short sketch is added of the practical application of 
 geological surveying, in the important question of water- 
 supply from deep-seated springs. 
 
L I B R A R Y 
 
 UNIVERSITY OF 
 
 v CALIFORNIA. 
 
 x jy 
 
 PART I. 
 
 GEOLOGICAL MAPPING. 
 
 CHAPTER I. 
 
 MAPPING AND INSTRUMENTS. 
 
 Maps Contour Maps Compass and Protractor Hammer, Pick, 
 Spud, &c. Scales Tracing Boundaries General Propositions. 
 
 Maps. In tracing and mapping geological boundary 
 lines, it is very essential to have as good as possible a 
 map of the district to be surveyed. One that is not 
 tinted and not closely covered with the names of places, 
 for the fewer these are in reason the better but on 
 which such prominent objects as churches, windmills, 
 and so on are shewn with fair typographical accuracy. 
 The physical features should be rendered as distinct as 
 may be, by the insertion of all rivers, brooks, and water- 
 courses ; and if there be hill-shading, drawn with even 
 an approach to accuracy, it will be an improvement; and 
 heights above the sea-level given in figures here and 
 there are a great advantage. Maps drawn to a scale of 
 one inch to a mile will generally be found the best for the 
 purpose ; they are sufficiently large to admit of the main 
 features being correctly shewn, and a sheet representing 
 many square miles can be carried and referred to without 
 inconvenience. If great accuracy be required as in the 
 
6 FIELD GEOLOGY. 
 
 out-crop of Coal-seams, for instance it is well to go at 
 once to maps drawn on a six inch scale, although they 
 may be in some respects inconveniently large. For the 
 plain spaces thereon between roads and hedges admit of 
 the frequent notes necessary in such cases being written 
 on the map itself, instead of in a book specially provided 
 no trifling advantage when the size of the map to be 
 carried is taken into consideration. The maps of the 
 Ordnance Survey, especially those issued during the 
 last few years, are as good as any ; in choosing copies, 
 those should be selected which are clear and distinct as 
 regards the engraved lines, but which are light rather 
 than dark impressions. 
 
 Contour Maps. Some maps have marked on them 
 certain lines, the meaning of which it is well clearly to 
 understand ; these are called " contour lines." To the 
 eye accustomed to them, these lines convey at a glance 
 the physical geography or the actual " shape " of a tract 
 of country its hills and valleys, its precipices and 
 ravines and not only in a sketchy or approximate form, 
 but with heights and depths taken from actual ad- 
 measurement. A contour line runs through all the 
 points at which a perfectly horizontal plane at any given 
 height would intersect the surface of the ground ; in 
 other words, if the land were covered with water to a 
 certain height, the margin of the water would be exactly 
 represented by a contour line drawn at that same eleva- 
 tion. These lines are shewn for every 10, 25, 50, or 100 
 feet, according to the scale of the map and the degree of 
 accuracy required. In geological surveying they are of 
 assistance in the drawing of boundary lines, ascertaining 
 heights and making various calculations. 
 
GEOLOGICAL MAPPING. 
 
 Note. All maps are laid down on the paper with 
 reference to the true meridian, the proper allow- 
 ance having been made in their compass bearings for 
 the magnetic variation at the present time in these 
 Islands the needle points about 22 West of due 
 North. 
 
 Compass and Protractor. It frequently happens that 
 it is necessary to identify on the map one's exact locality, 
 when the roads, fences, &c., shewn thereon do not afford 
 sufficient indication. For this purpose a Compass is 
 used ; an ordinary pocket compass of fair size will suffice 
 in most instances, and will give very nearly the position of 
 the place at which it is used ; but for greater exactness 
 -a prismatic compass is necessary. The latter is not quite 
 so easily carried as the pocket compass, although the 
 small prismatics now made and fitted in sling-cases are 
 very portable, and a Protractor also is required to plot 
 .the^result of an observation. 
 
 Fig. 1. Compass and Clinometer. 
 
 The pocket compass (fig. 1) generally has its circum- 
 ference divided into 16 parts the 4 cardinal points, the 
 4 intermediate, which divide the cardinals, as KW., &c., 
 
FIELD GEOLOGY. 
 
 and 8 others sub-dividing the spaces between the car- 
 dinal and intermediate points, as KKE., and so on. To 
 determine a locality, the needle must be set free, and 
 the instrument held perfectly level in front of the 
 observer, and between him and the distant object on 
 which he takes a bearing. It must then be turned 
 steadily round, until the needle comes to rest 22 to 
 the left or West of North. At the same instant tho 
 eye, being carried from the centre of the compass to the 
 object and back again, will detect the point in the cir- 
 cumference on a line from the object to the observer. 
 This reads off perhaps N.E., or half-way between N". and 
 E. ; this would be represented on the map by a line, in 
 such a position as to lie mid-way between two others, 
 one vertical for N'. and S., the other horizontal for E. and 
 W. direction. A scale or pencil laid across the object 
 on the map in such mid-way position affords a means 
 of drawing a pencil line that corresponds with the bear- 
 ing taken. The observer is situated at some point along 
 this line, and by repetition of the observation on another 
 object (as nearly as may be at right angles to the first) 
 he gets a second line crossing it at a point which repre- 
 sents the required position. If E.N.E. had been read off, 
 half-way again between N.E. and due E. would give the 
 direction, and the same method of course applies to all 
 the other points in the compass. 
 
 The prismatic varies from the pocket compass in 
 having its circumference divided into 360 degrees, 
 instead of into cardinal and intermediate points ; and 
 in being provided with sights for taking more accurate 
 observations. The needle carries with it a nicely 
 balanced card on which the divisions are marked, the 
 
GEOLOGICAL MAPPING. 9' 
 
 figures thereon being reversed so that the prism (which 
 inverts the rays passing through it) presents them to 
 the eye in their proper position. The card is, or ought 
 to be, so attached to the needle that proper allowance 
 has been made for magnetic variation. To take a bear- 
 ing, the needle must be liberated, the vertical sight 
 erected, and the prism pulled up to suit the eye of the 
 observer. The instrument is then held up to the eye, 
 being kept as level as possible in the hand, and directed 
 to the object from which the bearing is being taken, 
 until the card shall have gradually ceased to revolve. 
 
 4-0 SO 60 TO 80 3 
 
 D 106 "t rtG <.30 1*0 
 
 
 o 
 
 
 
 i 
 
 I I M I I I I II I I I I I I I Ijfc I I I I .1 I I I I I I I I I I I LJ 
 
 Fig. 2. Protractor, upper side (half size). 
 
 The division then seen immediately beneath the vertical 
 wire records the number of degrees subtending the 
 angle contained between the line of bearing and the 
 true N". and S. meridian. The number of degrees count 
 to the right of due N. ; thus E. reads 90, S. 180, W. 
 270, and 1ST. itself 360, the complete circle. In plotting 
 the line of bearing therefore the protractor (fig. 2) must 
 be laid on the map to the right of the object, the centre 
 of the semi-circle which it represents resting directly 
 thereupon and its inner edge parallel (as near as the 
 eye can judge) with the margin of the map that is, 
 due N". and S. A point is now marked on the paper 
 
10 FIELD GEOLOGY. 
 
 at the number of degrees corresponding with that read 
 off in the compass and a line drawn through this point 
 and the object gives the first bearing. A second line is 
 then found to cross the first, the nearer the angle be- 
 tween them is to a right angle the greater the accuracy 
 of the result. 
 
 Note. As the protractor represents but one half 
 of the circle it will be necessary when the number 
 of degrees read off exceeds 180 (the total shewn 
 thereon) to plot that number and begin again or, 
 what is the same thing, to deduct 180 from the 
 degrees indicated and commence from the other 
 end, that is, with the protractor placed on the left- 
 hand side of the object. 
 
 It sometimes occurs that one bearing is sufficient for 
 the purpose : e.g. when the spot is situated someivhere 
 on a road or fence-line shewn on the map, but with 
 nothing to shew its more exact position. Another and 
 a ready method of spotting one's locality where there is 
 no lack of known landmarks is to place on the ground 
 a stick, or a hammer, directed to an object ; then to 
 look along the stick from its other end and note the 
 object with which, or near to which, it is in line. This 
 gives a fair bearing in one direction, and if it be crossed 
 by another, as with the compass, the position found on 
 the map is not far wrong. 
 
 Hammer, Pick, Spud, &c. To draw a geological 
 line, it is necessary to have at hand some means of 
 ascertaining what strata run up to the surface in any 
 locality that is to be geologically mapped. There is 
 always with very rare exceptions a depth of surface 
 soil varying from 2 or 3 inches to 2 feet or even more, 
 
GEOLOGICAL MAPPING. 
 
 11 
 
 beneath this is frequently found a subsoil consisting of 
 the'disintegrated upper portion of the rock on which it 
 
 rests. To ascertain the kind 
 of rock, these, or at all events 
 the former, must be pene- 
 trated. 
 
 Almost every one who 
 follows geological pursuits 
 has a hammer to suit his in- 
 dividual fancy, and so long- 
 as it is capable of breaking 
 up a good-sized stone its 
 fashion is immaterial. But 
 for the purpose of drawing- 
 lines it will be found con- 
 venient to have the tail of 
 the hammer drawn out into 
 a chisel-pointed pick, 3 or 
 4 inches in length, with a 
 slight downward curve 
 
 (fig- 3). 
 
 With such a pick one can 
 easily dig down through a 
 foot of surface soil, or cut 
 away the face of clay and 
 sand in pits, banks, and cut- 
 tings. Its outer side should 
 
 be bent into a curve de- 
 Fig. 3. Hammer, Pick, and _. 
 
 Spud combined. scribed by a radius, 1 foot 
 
 in length for a pocket ham- 
 mer, and 18 inches for one with a long handle such as 
 would answer also for a walking-stick. Some prefer 
 
12 FIELD GEOLOGY. 
 
 boring to digging through the soil this is done by a 
 gouge-like spud attached to the lower end of a stick or 
 a long hammer-handle ; it can be either removable or 
 permanently fixed. This, when pressed into the earth 
 and screwed round, will make a hole from a foot to 2 
 or 3 feet deep, according to the hardness of the mate- 
 rial, and bring up cores as specimens from the bottom. 
 In figure 3 is represented a combined hammer, pick, and 
 spud ; with the latter unscrewed the hammer does duty 
 for a walking-stick, and altogether it is as useful and por- 
 table a set of implements as can be carried by a Geologist. 
 
 10 
 
 CHAINS 
 
 20 30 4-0 SO 60 MJ 
 6 INCHES TO ] MILE 
 
 s 
 
 t 31IW | 01 HONl | 
 
 SliM 
 
 fr C Z I 
 
 Fig. 4. Protractor, underside as scale (half size). 
 
 Scales. For the purpose of measuring distances on 
 the map a scale is required, the most useful size being 
 6 inches long. The carrying another instrument may 
 be saved by having the reverse side of the protractor 
 divided (fig. 4), on the one edge into 80 parts for use 
 with the six-inch maps, each part representing a chain. 
 The other edge, for use with the one-inch maps, must 
 be divided into inches, and each inch into 40 parts re- 
 presenting 2 chains : smaller sub-divisions would be too 
 minute. The otherwise plain edge (on the degrees side) 
 of the protractor may with advantage be divided for a 
 
GEOLOGICAL MAPPING, 13 
 
 part of its length into feet, on the scale of 6 inches to 
 a mile it will be serviceable for plotting or measuring 
 from sections (fig. 2). 
 
 Tracing Boundaries. A geological ma*p is one which 
 defines the area occupied by the denuded edge, or upper 
 surface of each formation, where it comes to the level of 
 the ground. To accurately construct such a map, therefore, 
 every part of the ground must be more or less minutely 
 examined. If by any means, as by boring or otherwise, 
 the surface of an area were to be proved at say every 
 100 yards and the varying results shewn by different 
 colours, a geological map would be roughly presented. 
 But it would be a,n approximation only, for there would 
 still remain to be shewn the exact position between the 
 borings where the lines of division run. In Chapter II. 
 it is intended to explain how such lines may be traced 
 and represented on the map to be geologically tinted. 
 
 Note. In speaking of "boundary lines," those 
 are meant which bound a formation, which describe 
 its lower margin, and, in fact, indicate its extreme 
 occurrence in any direction. Its upper edge, where 
 it first appears at the surface, is called its " line of 
 outcrop," and this of course corresponds to the 
 boundary line of the overlying formation. 
 If a certain set of fields on one side of a road, fence, 
 or brook, shewn on the map, were entirely on one forma- 
 tion, and another set of fields on the opposite side were 
 entirely on another formation, then the engraved line 
 would answer also for that of the geological division. 
 But it rarely happens that the arbitrary lines of a road 
 or fence follow the intricate windings of a natural divi- 
 sion of the rocks. With a brook the case is somewhat 
 
14 FIELD GEOLOGY. 
 
 different, it being frequently found that brooks and 
 water-courses work their way back along such planes of 
 separation. 
 
 For the sake of constant reference it is best to have 
 the plain copy of the map, which is to be geologically 
 coloured, cut up into slips of convenient size, say 6 by 
 4J inches. They may be secured by bands within the 
 pages of a note-book or pocket map-case. Six-inch 
 maps must be used in larger sheets carried in cases slung 
 from the shoulder. If the slips are cut all to one size, 
 they can afterwards be mounted on linen to fold in the 
 usual manner. 
 
 General Propositions. The following three proposi- 
 tions, if remembered, will be of material assistance : 
 
 1. The boundary lines of horizontal strata exactly 
 coincide with the contours. 
 
 This must be the case, however uneven the 
 surface of the ground where the outcrop occurs. 
 
 2. The boundary lines of strata dipping towards a 
 hill are less winding than the contours. 
 
 This is evident if we consider that were the 
 dip to be gradually increased until the strata were 
 vertical, the lines of outcrop would gradually ap- 
 proach, and finally become parallel straight lines. 
 Therefore, as the dip into a hill, so the line varies 
 from a contour towards a straight line. 
 
 3. The boundary lines of strata dipping from a hill 
 are more winding than the contours. 
 
 This is just the reverse of Prop. 2, for were 
 the dip increased until equal to that of the sur- 
 face slope, the boundaries would run in parallel 
 lines down the flanks, and until the slope varied 
 
GEOLOGICAL MAPPING. 15 
 
 could not meet. But the proposition is true to a 
 certain point only when the dip, in this direc- 
 tion, exceeds that of the slope, the boundary lines, 
 in this case also, begin to draw in towards a 
 straight line, which they must eventually attain 
 to if the dip increased until the strata were vertical. 
 Strata sometimes occur in a horizontal or nearly hori- 
 zontal position. It is evident from Prop. 1, that if we 
 can once fix a point through which passes the boundary 
 of such a stratum, a contour line drawn from this point 
 will accurately represent the boundary so far as its 
 horizontality is continued. 
 
 Much more frequently we find strata dipping into the 
 higher ground from beneath which they have risen to 
 the surface. Indeed, this may be considered the normal 
 position of stratified rocks now forming dry land, as 
 their dip has itself given the initial form to the hills 
 above them. In this case any points at the same level 
 on the line of strike must be on the boundary assuming 
 its passing through one of them to have been ascertained. 
 A line following the curves of the contours, but flat- 
 tened in proportion to the dip (Prop. 2), represents 
 accurately the line required. 
 
 It is an exceptional occurrence for strata, at their out- 
 crop as opposed to ' dip-slope,' to dip with the slope of 
 the ground. When this does occur, the line of junction 
 must be ascertained in several places, and the points 
 united by exaggeration of the contour (Prop. 3). 
 
 Contours run in a V-like shape up the valleys, in 
 straight lines on flanks and ridges, and sweep round the 
 outline of the hills their variations are as numerous as 
 the hills themselves, but this kind of form prevails in 
 
16 
 
 FIELD GEOLOGY. 
 
 Fig. 5. First Slip. 
 
MAPPING. 17 
 
 all. (See some excellent remarks on, and illustrations 
 of, this subject in Sir Charles Lyell's " Students' Ele- 
 ments of Geology," p. 60 [1871].) 
 
 The above are general ideas which it will be well to 
 have impressed on the mind, as in tracing a boundary 
 their principle will yield immense assistance. Of course 
 in practice the ground must be gone over, and the actual 
 line followed, for dip may change anywhere, and it often 
 does so in places where it is least expected. Faults also 
 may occur, and these interrupt suddenly the continuity 
 of a line, and involve a fresh one of their own. 
 
 i) M J* K A H 
 
 CHAPTER II. .! 
 MAPPING (continued). C A 1 ^ j {< \ ) ] > \ T f 
 
 Examples of Tracing Boundaries Mem 
 
 Symbols Drift Deposits. 
 
 Examples of Tracing Boundaries. Having then pro- 
 cured a map of the district to be surveyed, cut it into 
 two slips to fit the map-case, and provided ourselves with 
 compass, scale, hammer, and so 'on, we will proceed to the 
 actual work before us. The slip represented by fig. 5 
 (but of course without the geological lines thereon) is to 
 "be the scene of our operations, and we start, in imagina- 
 tion, from the church, which, we are inclined to think 
 from the white appearance of the soil hereabouts, stands 
 on the Chalk formation. By an examination of the 
 pond on the other side of the road this supposition is con- 
 firmed, for the excavation has been made three or four feet 
 deep, and its sides here and there exhibit sections of that 
 well-known rock. We note this fact by a symbol of 
 
18 FIELD GEOLOGY. 
 
 some kind a small x will do marked on the map 
 where the rock is exposed, that is, at the pond. 
 
 Proceeding along the road to the N". we find an old 
 pit, nearly overgrown, which turns out to have been 
 formerly worked for sand. By picking about in all 
 likely places we discover that sand is not the only thing 
 in the pit, for its upper part on the S. side is really in 
 chalk. We clear away the soil with our pick, making 
 a clean-cut trench, and soon get an actual junction of 
 chalk and sand, the former overlying the latter. This 
 is a grand find, and one that will not frequently be made 
 in practice as sand-pits are made for the sake of sand 
 only, and chalk-pits for the chalk it happens rarely, 
 and tlien by accident, that pits and quarries are opened 
 on the line of junction. On the map we indicate the 
 occurrence here of chalk over sand, by the chalk sym- 
 bol x over another (for instance e) for sand, with a short 
 line between : thus -. 
 
 Note. The method of observation, and the notes 
 made of this and other exposures of the rocks, and 
 of facts relating thereto and otherwise obtained, are 
 described in Part II. 
 
 The boundary of the chalk of course passes through 
 this pit ; accordingly we draw a short line across the road 
 in that position, and which will be presently prolonged. 
 We now continue our walk in the same direction, but 
 see nothing worthy of remark except that clay is visible 
 in a newly-cut ditch about half-way down to the brook 
 this is indicated by another symbol, x, at the spot 
 where it is observed. Evidently we have come off the 
 sand, but nothing as yet points out the line of boun- 
 dary, and its discovery may be for the moment deferred. 
 
MAPPING. 19 
 
 We should expect to find below the Chalk, the Upper 
 Green-sand, and below this the Gault clay ; probably we 
 are now on the latter formation, but of this we cannot 
 be certain without further evidence. There is a brick- 
 yard on the other side of the brook, and the pit there 
 from which the clay is taken affords ample material to 
 justify our coming to that conclusion.* Looking north- 
 wards the gault clay forms a nearly level flat of rich 
 pasture land extending apparently beyond the margin 
 of our map. 
 
 On retracing our steps we observe in the distance an 
 excavation of some kind, a good way off on the W. side 
 of the road, .and thereto we make our way. It proves 
 to be a trench dug for a drain, at one part of which clean 
 gault is turned out, and a little higher up, sand. The 
 junction is close by, not exactly visible anywhere, but 
 it must be between the two places, and we can here 
 commence our line. But where are we ? Away from 
 the road, the brook, and everything else on the map. 
 Now the compass comes into requisition, and we at 
 once take a bearing on the church, it reads S.E., and 
 we draw a pencil line accordingly.f Taking a second 
 bearing on the barn away to the northward, we get 
 another line crossing the first at our exact position. 
 Here then begins the line, and here also seems to be a 
 slight alteration in the slope of the ground, the gault 
 makes almost a flat to the N., the sand rises more 
 rapidly to the S., the change of feature due evidently to 
 the difference in the strata.^ Our line must be drawn 
 as nearly as may be where this change occurs, which 
 seems to very nearly follow the contour of the ground, 
 
 * Post, p. 55. t Ante, p. 8. $ Post, p. 28. 
 
 22 
 
20 FIELD GEOLOGY. 
 
 it crosses the road between the sand-pit and where clay 
 was observed in the ditch. Beyond the road this feature 
 becomes less distinct, but we draw the line as a contour 
 from the shape of the ground, of course it sweeps round 
 to the right up the other valley, and just where it crosses 
 the footpath there is a pond. Here we can get no 
 direct evidence, but may fairly assume that thus far our 
 line is correct, for the pond would be about on the 
 junction dug through the sand which yields water into 
 the clay by which that water is upheld. Continuing 
 the contour it takes us across the road, which offers no 
 evidence other than a slight change in inclination, and 
 on to the lane beyond ; here, by picking in the banks T 
 we get sand in one place, clay in another just below, 
 and between the two runs the line of boundary. 
 
 So far this is satisfactory, and we return to follow the 
 chalk line, the commencement of which was afforded by 
 the sand-pit near the church, but in passing up the 
 lane we find out by aid of the pick, and we mark on 
 the map, where it will be crossed by the chalk boundary. 
 From the sand-pit we draw a contour as before, getting 
 here and there in the ditches a little evidence to check 
 our work, round the point, across the footpath and the 
 main road, through the spot marked in the lane, and on 
 by the form of the ground. Here the line would seem to 
 turn back as it were upon itself, and to end where it 
 began, in the sand-pit ; it really does so, and the chalk 
 we have mapped thus is proved to be an " outlier." We 
 walk over the ground on the S. side of the brook, but 
 find no open sections, in all the ditches clay is visible 
 except at the extreme S.E. corner, where the soil is 
 very sandy. A well has been sunk at a spot which 
 
MAPPING. 21 
 
 we mark on the map, and is stated to be 110 feet in 
 depth. 
 
 Note. Almost every bank where the road is in 
 cutting and every ditch of even moderate depth 
 will yield evidence of the kind required, when the 
 fallen soil and rubbish have been cleared away. 
 But in picking into a bank, in spudding at the side 
 of a ditch, or in cutting at the face of an exposed 
 section, care must be taken to get at the actual 
 stratum beneath the vegetable soil. In the absence 
 of ditches, trenches, and banks (and there are many 
 bleak spots bare of all such aids), we must pick or 
 bore through the surface soil here and there on 
 either side of the probable line of boundary, look 
 out for the heaps of stuff thrown out from their 
 holes by moles, rats, and rabbits these often afford 
 useful hints in an obscure area and last, but not 
 least, we must accustom our eye to judge from the 
 soil itself what is the rock which lies beneath, in 
 other words, from which it has been derived. 
 At home the lines should be permanently drawn with 
 Indian or other ink that will not run with wash of 
 colour; the brickyard, the sand-pit, and the section- 
 symbols inked in, and the pencil lines of bearing, &c., 
 erased ; the spaces between the lines may then be tinted 
 in any colours selected for the different formations. 
 
 Let us now take in hand another slip, fig. 6. Here 
 -we start perhaps at the S.E. corner, which is on chalk, 
 for that rock is seen in a small pit at the back of the 
 farm, and the ditches by the roadside. The ground is 
 comparatively high here and overlooks a broad flat to 
 the 1ST. which is traversed by a fair-sized brook. In 
 
22 
 
 FIELD GEOLOGY. 
 
 Fig. 6. (Second Slip.) 
 
MAPPING. 23 
 
 passing along the road, and after losing the whitish soil 
 of the chalk, we find, first sand, then a little farther on 
 gault clay ; no good sections, but still sufficient to enable 
 us to draw short lines where the road is probably crossed 
 by the boundaries. Once on the clay, we see nothing 
 else until we approach the stream, which runs through 
 flat marshy ground that appears to be quite level. This 
 flat marshy ground is " river alluvium," and as such 
 must be mapped a very easy matter, which consists 
 mainly in drawing a line where the slightly sloping 
 surface of the gault is lost in the level of the alluvium. 
 A contour line it is in fact, and necessarily so, seeing 
 that this alluvial deposit is the result of deposition from 
 the flood waters of the river which has occasionally 
 overflowed its banks. This line is best drawn in walk- 
 ing along it, or nearly so, down one side of the stream 
 and up the other ; it is found to run a little way up the 
 smaller streams and to die out just before we reach the 
 "W. margin of the slip. 
 
 A clean section of the gault is seen in a pit by the 
 roadside, on the N. side of the river, but no other 
 evidence, although we walk over the flat at the N.W. 
 corner and down the W. side, until we strike the foot- 
 path when gault is again visible. Following the foot- 
 path, at the rising ground we come upon sand, note 
 approximately the junction, and a little higher up find 
 by digging that the sand passes in under the chalk. It 
 is now a matter simply of continuing to draw these two 
 boundaries, the lower one passes through a spring, by 
 which the general accuracy of the work is proved, and 
 both cross the road where we had drawn the short pro- 
 visional lines soon after starting. 
 
24 
 
 FIELD GEOLOGY. 
 
 Fig. 7. (Third Slip.) 
 
MAPPING. 25 
 
 We have heard that a chalk pit may be seen by the 
 road that crosses our third slip, fig. 7, and we will com- 
 mence our survey there or thereabouts. On the way 
 and near the S. margin of the map, clear grey sand has 
 been thrown out from a hole newly-dug for a gate-post ; 
 this is very different from the sand seen in the first and 
 second slips surveyed, and we conclude, from the level 
 and general run of the country, that it can hardly pass 
 beneath the chalk. However, no other good section is 
 obtainable, and there seems no chance of getting at the 
 junction, for the soil is so deep and there are no ditches 
 worthy of the name. We can simply dot in a line where 
 the sandy soil appears to end, and so for the present leave 
 it and get on to the chalk pit. 
 
 This is a fine excavation on the very highest point 
 in the map, and to the N". commands a view down and 
 beyond the chalk escarpment, which at once indicates 
 that the mapping of this slip will give but little trouble 
 chalk, bare chalk in rounded hills and hollow, every- 
 where is visible. Having made our notes in the pit 
 (Part II.), we descend the road which winds down the steep 
 slope, and has been cut through the higher ridges, fre- 
 quently exposing the chalk in the first part with layers 
 of flint, in the lower portion without any flints at all. 
 Here is. an exposure of sand, and where the roads meet 
 a small pond in clay the same kind of thing exactly 
 that was met with in our first and second slips and on 
 turning up the road to the left we make out a junction 
 of the beds. These are then easily traced to the margin 
 of the map, by feature in the usual way, the lower line 
 running by a pond that is shewn thereon. 
 
26 
 
 FIELD GEOLOGY. 
 
 Wocd 
 
 Cottages 
 
 V^ 
 
 
 Fig. 8. (Fourth Slip.) 
 
MAPPING. 27 
 
 In making another expedition to survey the fourth 
 slip, fig. 8, we enter upon its area, let us suppose, near 
 the top of the chalk escarpment, which is completely 
 overlooked from the road. We pass on by the windmill, 
 not troubling to search for sections as chalk everywhere 
 abounds, turn to the left at the branch roads, and 
 presently observe in a road cutting some mottled loam, 
 yellow, red, and brown. In slip 3 we found grey sand 
 apparently resting on the chalk this is something very 
 different, and we dig a trench down the side of the 
 cutting to ascertain if the grey sand be here beneath 
 the loam. It is not, but we come upon a bed of dark 
 brown clay enclosing green-coated flint pebbles, and below 
 this the chalk itself. We make our notes of these facts 
 (Part II.), find our exact position on the road by a 
 bearing (N.) on the windmill, and draw a line across the 
 road at the boundary. Nothing more worthy of note 
 occurs until we come to a small pit near the corner of 
 the map, dug into clean grey sand similar to that in 
 slip 3. This is put down* on the map by aid of a bear- 
 ing (N.E.) on the farmhouse and pacing the distance 
 therefrom, as no other object is visible on which to take 
 a second line of bearing. 
 
 On the other road in the slip is a brick-yard, where 
 the junction of the chalk and overlying mottled loam, 
 including the brown clay with green pebbles, is visible 
 and we ascertain that sand occurs just to the S. of 
 this spot. From this we conclude that the sand here 
 rests on the loam, and getting occasional hints from the 
 drains and ditches, we draw our lines, and the mapping 
 of slip 4 is completed. 
 
 The four slips which we have surveyed form parts of 
 
28 FIELD GEOLOGY. 
 
 one map, although for the sake of clearness they have 
 been hitherto treated as distinct : on placing them to- 
 gether in proper position they would be found the same, 
 but on a larger scale, as the coloured map in the frontis- 
 piece. The former may be considered as one's working 
 or field copies, the latter as completed for reference or 
 for publication. 
 
 One slip or one area will frequently elucidate what is 
 .somewhat obscure in another ; as the Upper Green-sand, 
 mapped in either figure 6 or 7, prove that the sandy soil 
 at the S.E. corner of figure 5 is due to that formation, 
 although in the slip itself no sections were obtainable. 
 
 Note. The process of mapping the older and 
 more disturbed rocks is somewhat different, and 
 is much facilitated by an acquaintance with the 
 methods of observing their inclination and litho- 
 logical characters. An example of this kind of 
 work will be given, but is deferred until after 
 those methods have been considered in Parts II. 
 and III. 
 
 Memoranda. We have now constructed a geological 
 map on which are shewn (with, let us hope, a reasonable 
 approach to accuracy) the outcrops of four formations 
 the mottled Loams, the Chalk, the Upper Green-sand, and 
 the Gault. We have proved their relation to each other, 
 and with the data obtained in the pits shall be able to 
 draw therefrom a section also, perhaps several hundred 
 feet in thickness. But, as this will be considered in the 
 second portion of the work, we will now proceed to no- 
 tice several things which should be borne in mind while 
 mapping geological boundaries. 
 
 It frequently happens that lines have to be drawn 
 
MAPPING. 
 
 through large parks, woods, moors, and marshes, where, 
 perhaps, no evidence whatever can be obtained. In 
 these cases the difficulty may be considerably lessened, 
 by first mapping for a good distance all round such ob- 
 scure areas. With the data and the ideas thereupon 
 thus gained, the lines may then be run by feature alone 
 with every chance of accuracy. 
 
 Where there is but little or no change of feature, the 
 line being traced should be kept well up above where 
 it would at first seem to run for this reason, not only 
 is the debris of the upper rock constantly falling upon 
 the outcrop of the lower, but the soil also which properly 
 belongs to it is continually being washed down to a 
 lower level. This for some distance down gives a decep- 
 tive indication of the upper rock, where the lower only 
 would be found on making an excavation. 
 
 The varying hardness and the dip of the rocks give 
 the form to the district in which they come to the sur- 
 face. For, precisely in inverse proportion to these con- 
 ditions, have the agents of denudation worn them away ; 
 or, to put the proposition in another form, the promi- 
 nent minor features of a district are in exact proportion 
 to the power its rocks possess of resisting denudation. 
 As dissimilar rocks thus make a change of feature 
 along their junction, a knowledge of the fact is, as we 
 have seen, of great service in drawing their lines of 
 boundary. 
 
 But denudation will also obscure the minor features 
 that it has made, for the rain- wash which is the immedi- 
 ate result of sub-aerial erosion will lodge on projections 
 and fill up hollows. The eye will, however, by practice, 
 get accustomed to look and to make allowance for this 
 
30 
 
 FIELD GEOLOGY. 
 
 condition of things, and assign its proper place to the 
 line of division. 
 
 Traversing. In surveying a district of which it is 
 necessary or desirable to map very accurately the out- 
 crop of the strata, the ground must be gone over much 
 more closely than is indicated by the preceding exam- 
 ples. It then is well to follow the lines of ditch and 
 fence by which the area is intersected, as these serve to 
 guide one in traversing all the ground without going 
 twice over any portion. Such lines are, as a rule, some- 
 what irregular, and occasionally too far apart for the 
 purpose, when they must be left and the intervening 
 
 Fig. 9. Showing Two Methods of Traversing Ground. 
 
 spaces walked over. The above diagram (fig. 9) shews 
 two very useful methods of traversing ground one on 
 each side of the main road the dotted line, starting 
 from the church, traces the path along which the walk is 
 taken. It will be seen that these dotted lines cover the 
 
MAPPING. 31 
 
 area at about the width of one field apart ; if a pond, or 
 the chance of any other section offers, a divergence 
 thereto must be made. By walking over the ground in 
 this way, all the details of the strata, however numerous 
 they may be, are collected as it were at once, and a por- 
 tion, first of one line, then of another, is drawn, as we 
 cross and re-cross the boundaries. But sometimes it is 
 found more convenient to commence and follow out one 
 line this is best done by walking along a ditch or fence 
 until we cross the line, then along the bottom of the 
 field to the next fence, up this until the line is again 
 crossed, and so on. 
 
 When walking over and geologically mapping any 
 area, it may seem almost impossible to, as it were, con- 
 vert oneself into a surveying machine to simply dig 
 out certain physical facts to put down on paper what 
 one actually sees or discovers, and for the time do no- 
 thing more yet this is the best plan that could be 
 adopted. The occupation itself affords much ground for 
 speculation, as to the extent of this rock, and the thick- 
 ness of that, the relation of the one to the other, the age 
 of each, and the amount of denudation to which it may 
 have been subjected. This is pleasant amusement enough, 
 and in one sense profitable also, but a geologist thus 
 reasoning in his own mind before he has obtained suffi- 
 cient data on which to base his ideas is really theorising ; 
 and it is astonishing to find how readily the facts 
 afterwards ascertained may seem to support a theory 
 thus pre-conceived. The machine-like method of pro- 
 cedure should be as far as possible followed, until a 
 considerable area has been accurately mapped, and all 
 available data obtained and correlated, then a theory, or 
 
32 
 
 FIELD GEOLOGY. 
 
 it may be a generalisation can be based thereon, with a 
 reasonable faith in its soundness and truth. 
 
 Symbols. Three sets of symbols are here appended,, 
 and may be found useful, but of course any other letters, 
 figures, or devices, would answer the same purpose. 
 Those in the first column (Greek letters) can be recom- 
 mended for simplicity and convenience, as the tail 
 possessed by each letter when prolonged, is serviceable 
 in marking the exact spot at which a section is visible. 
 
 Limestone A L , D 
 
 Sandstone. Sand 
 
 Gault 
 
 Chalk 
 
 Thanet beds 
 
 Eeading beds 
 
 London clay 
 
 Boulder clay 
 
 Brickearth. Loam 
 
 Gravel 
 
 Clay 
 
 Two or more symbols may be so arranged as to indi- 
 cate at a glance the relative position in which the beds 
 are seen in section, by a line between them indicating 
 the inclination (if any) of the divisional planes of strati- 
 fication or of a fault. Thus a section of gravel, over 
 Thanet beds faulted against chalk, would be shewn - r - 
 and a bed of Limestone resting on Sandstone, and dip- 
 ping in the same direction . (WhitaJcer.) 
 
 The following table gives the symbols or signs en- 
 graved on the published maps of the Government Geo- 
 logical Survey, to indicate the occurrence at the points 
 
 A 
 
 L 
 
 <7 
 
 s 
 
 r 
 
 G 
 
 X 
 
 ch 
 
 T 
 
 t 
 
 P 
 
 r 
 
 \ 
 
 I 
 
 ft 
 
 B 
 
 e 
 
 b 
 
 7 
 
 9 
 
 K 
 
 d 
 
MAPPING. 33 
 
 where they are shewn of certain phenomena that have 
 been ascertained either from actual observation or au- 
 thentic information. 
 
 * STRATIFICATION. 
 
 Horizontal 
 
 H~~ Vertical (longest line on the strike) 
 X Undulating 
 JiA> Contorted 
 
 t Highly inclined ^ __.,. , ,. ,. 
 
 f . TT , : , A . f With general dip in the 
 
 // Undulating >,. * /.^ 
 
 , ~ ( direction of the arrow. 
 
 f Contorted ) 
 
 Anticlinal axis 
 . Synclinal axis 
 / Dip from observation (with No. of degrees, 
 
 thus ^5) 
 
 Dip from information 
 / Cleavage 
 *> Limestone quarries 
 White Lines=Fau\.ts at the surface 
 Yellow Faults underground 
 
 GLACIAL DRIFT. 
 
 Roches montonnees 
 
 , . , -, \ Direction of Ice- 
 striated I 
 
 -CM t. _n , , -, r flow not appa- 
 
 Flat surface striated ( 
 
 ) rent. 
 
 Roches montonnees striated ) Shewing direction 
 < Q Flat surface striated ) of Ice-flow. 
 
 ORES OF THE METALS. 
 o Gold ]> Silver 
 
 V Copper I/ Tin 
 
 ^2 Lead # Manganese 
 
 $ Iron ^ Zinc 
 
 3 
 
34 FIELD GEOLOGY. 
 
 Drift Deposits. There are certain deposits of gravel 
 and clay to which the methods of mapping previously 
 described are scarcely applicable without additional sug- 
 gestions for the student's guidance. He will have made 
 himself acquainted theoretically with the phenomena of 
 the " Glacial Period," but the relics thereof which he will 
 come across in his field expeditions are sometimes very 
 puzzling in their nature and relations. The products of 
 the climatic and physical conditions that then prevailed 
 are, generally speaking, a series of clay beds, sometimes 
 contorted succeeded in places by gravels and sands, 
 as a rule false-bedded and very irregular in their distri- 
 bution and mode of occurrence ; these are in turn over- 
 lain by unstratified clay, enclosing fragments of many 
 kinds of older rocks, and known as " Boulder-clay." 
 
 These glacial deposits may and do occur singly or 
 together, sometimes one may be absent, sometimes 
 another ; but the peculiarity of them all is, not being con- 
 fined to any definite level, having indeed neither true 
 dip nor horizontality. They spread indiscriminately 
 over an old denuded surface, high and low ground alike, 
 capping the hills and filling the valleys, so that over 
 large areas the underlying older formations are com- 
 pletely hidden and this perhaps by a sheet of material 
 which, compared with the older formations, is compara- 
 tively thin and unimportant. Still the " Drifts," as 
 they in common with more recent deposits are called, 
 may be classified, and no geological map can be con- 
 sidered complete from which they have been omitted. 
 
 As these beds, except in rare instances, contain but 
 few, if any, fossils, the frequently scanty items of evi- 
 dence to be obtained from sections, and the inferences 
 
MAPPING. 
 
 from feature must generally be depended on for deter- 
 mining the order of their super-position. Where no 
 sections shewing junctions are met with, the form of the 
 ground may afford some hints as to which of two beds 
 is the upper, and which the lower, for a gravel overlying 
 clay will not make quite the same kind of feature as it 
 does when passing beneath. Assuming of course that 
 " Drift " of some kind is in question, it will generally be 
 found that a rounded hill consists of clay ; if the lower 
 part of its flank be gravel or sand and comparatively 
 steep, such gravel or sand may reasonably be supposed 
 to pass imder the clay but if, on the contrary, it forms 
 a flat or sloping plain, it probably rests upon it. ;; For 
 the lower part of a bed of gravel or sand, protected above 
 by a more tenacious bed of clay, is cut back at a rate dis- 
 proportionate to that of its upper part, and a more or less 
 abrupt rise is the result. Gravels frequently make flats 
 and sometimes long ridges, cut off as it were from the 
 land at similar heights around them. 
 
 The boundary lines of drift must be closely followed, 
 if an accurate map of the beds be desired contour is of 
 but little -use except as a guide to the eye in drawing 
 lines between the points through which they have been 
 found to run, and these points should be at no great dis- 
 tance from each other. A drift clay may be found in 
 one place on the top of a ML, and not on its flank or at 
 its foot, but a few hundred yards away it may perhaps 
 be discovered trailing down the slope, and even crossing 
 the valley, with none on the high ground whatever- 
 This must necessarily be the case, as we see on reflection, 
 for the drifts repose on an irregular surface, and those 
 portions which occupy the old hollows and channels 
 
 32 
 
36 FIELD GEOLOGY. 
 
 have been able for the longest time to resist erosion. 
 Were it otherwise, we should probably now find the older 
 hills only capped with drift, and the valleys again cleared 
 out by the agents of denudation but in all rocks hard 
 or soft, old or recent, the anticlinal line is the most 
 readily denuded. Partly, it may be, from the bend 
 having somewhat opened out its particles by tension, 
 thus producing in some cases fractures, and in others 
 weakening its power of resistance. Partly, or it may be 
 entirely, to the inward and downward dip of the beds 
 on each side of an anticline, which would make them 
 relatively stronger than the intervening flat part to re- 
 sist the attacks of erosion. Another and not unimpor- 
 tant reason may be, that a considerable portion of the 
 rain falling thereon percolates down into the rocks with 
 such inclination and is thrown out elsewhere, while along 
 the axis of elevation it all flows over the rock and re- 
 moves a proportionately larger share of its material. 
 
 It may be well here* to remind the student, that in 
 "drifts," the lower as regards level is not necessarily 
 the older of two or more deposits ; take, for instance, the 
 gravels occurring in a large drainage area. In past time 
 the river has spread a large sheet of gravel, through 
 which, as denudation went on, its course was again cut 
 with a lowering of its level, perhaps 20 feet. It de- 
 posited more gravel, which was in turn cut through and 
 the river's course was again lowered, it may be other 20 
 feet. In such a case the gravel at the higher level is 
 the older, and the various deposits form terraces at 
 heights 20 feet apart, marking as many stages in the 
 formation of the valley. Such are the higher, lower, and 
 intermediate terraces of gravel in the Thames and other 
 
MAPPING. 37 
 
 valleys the higher and older enclosing the remains of 
 extinct animals and of paloeolithic man, each succeeding 
 lower terrace more nearly approaching to the existing 
 state of things, and the last deposits having been formed 
 within quite recent periods. 
 
 These old valley gravels are now reduced to mere 
 patches in comparison with their former extension, but 
 from their consistency are much more easily mapped 
 than are the glacial drifts so also are the latest deposits 
 of all, such as brick- earth, gravel, and sand, at about the 
 same level as the rivers. The recent beds are frequently 
 found first on one side, then on the other of existing 
 streams, the present channel running along one edge, 
 then cutting across to follow for a distance the other 
 side, as shown by the stippled area in the frontispiece. 
 The lines of alluvium or marsh-land are as we have seen 
 (p. 23) readily drawn, and it is a good plan in making a 
 geological survey for this deposit to be the first mapped. 
 One thus gets a chance of seeing sections in the lowest 
 beds, and obtains also an idea of the physical geography, 
 or at all events of the valley-system, of the district. 
 
PART II. 
 
 SECTIONS. 
 
 CHAPTER I. 
 
 i 
 
 GEOLOGICAL SECTIONS. 
 
 Dip Strike Clinometer To find direction of Dip To find 
 amount of Dip Table of Dip, depth and thickness Exposed 
 Sections Notes. 
 
 Dip. Strata are but rarely found in an absolutely hori- 
 zontal position; it is indeed mainly owing to their 
 deviation therefrom that so many formations are now 
 seen outcropping at the surface of the earth. A know- 
 ledge of the angle at which they are inclined is of great 
 service to the geologist when drawing horizontal sections 
 to show the beds of a district, and in enabling him to 
 afrlrm, within reasonable bounds, the thickness of a 
 deposit and the depth at which it will be found in any 
 specified locality. The angle at which a bed deviates 
 from the horizontal is its " angle of dip," generally and 
 for sake of brevity called simply its " dip." A line passing 
 from any point on the surface of a bed through another 
 point which is the lowest possible at that distance from 
 the first in other words, the line of greatest steepness 
 represents the dip's direction. 
 
GEOLOGICAL SECTIONS. 39 
 
 Strike. Another line, crossing at right angles this 
 line of dip, that is of greatest steepness, must neces- 
 sarily be horizontal it would therefore coincide with 
 the edge of a bed that might come to the surface in a 
 perfectly level tract of country. This seldom occurs, 
 and owing to the general unevenness of the surface an 
 outcrop can rarely be represented by a straight line, 
 although the dip may for a long distance continue the 
 same. But a line through all points, situated at the 
 same level on a boundary, will always be found to lie at 
 right angles to the " dip ;" this line is called the " line 
 of strike," or shortly " strike," of a bed or a formation. 
 
 From a consideration of the above, it will be seen 
 that as the " direction of dip " varies, so also will the 
 " line of strike," which is roughly the outcrop of a for- 
 mation : inversely, as the " line of strike " or outcrop 
 varies, so also will the "direction of dip" in equal pro- 
 portion. Of this we may at all times be certain, even 
 although no ocular evidence be forthcoming, and the 
 fact will frequently be found to aid us in our geological 
 investigations. 
 
 It is a self-evident proposition, that as the amount of 
 " dip " varies, so does the horizontal breadth that the 
 outcrop of a bed of constant thickness, will occupy at 
 the surface. But it is a very useful thing to remember 
 in geological surveying, also in drawing sections where 
 the evidence is scanty, especially as for the latter pur- 
 pose the actual slope of the ground is ascertained. It 
 follows, that the value of any two of the three factors 
 tabulated below being known, that of the third can 
 easily be ascertained. 
 
 1. The thickness of a formation. 
 
40 FIELD GEOLOGY. 
 
 2. The dip. 
 
 3. The horizontal breadth of outcrop. 
 
 Clinometer. It matters little by what kind of in- 
 strument the dip of strata is ascertained, so long as it 
 indicates with a fair approach to accuracy the amount 
 of inclination. All clinometers must possess a gradu- 
 ated arc, and either a pendant that hanging perpendicu- 
 larly, or a spirit-level lying horizontally, shall show the 
 number of degrees that its base deviates to either hand 
 from a horizontal plane. A simple form of clinometer 
 
 Fig. 10. 
 
 is shown in fig. 10 ; but as portability is a great deside- 
 ratum, and as the pocket compass, which should be the 
 geologist's constant companion, possesses a graduated 
 circle, the one instrument may well be made to answer 
 the two purposes. This is effected by the addition of 
 the parts shown by the dotted lines in fig. 1, and of a 
 small pendant swung from the point which carries also 
 the magnetic needle. When the two instruments are 
 thus combined, the circumference must be divided not 
 only into cardinal and intermediate points, but also into- 
 degrees numbered to the right and left of zero. This 
 point is just over the centre of the clinometer base, the 
 figures run up to 90 on either side, and then back to 
 
GEOLOGICAL SECTIONS. 41 
 
 zero at the top, so that the instrument can be used 
 inverted, and placed to the under-side of a bed if 
 required. 
 
 To take the dip of a bed in a pit, quarry, or elsewhere, 
 clear away the material from its upper surface in a part 
 as flat as can be found, and which follows as nearly as 
 the eye can detect the general line of the whole mass 
 exposed. Place the clinometer on this, or what is a 
 better plan, on a stick, or hammer-handle, first laid on the 
 rock ; this being of greater length than the instrument 
 is less liable to error from an undulating surface. See that 
 the clinometer is directed along the steepest part of the 
 cleared surface, which is probably not in a line with the 
 face of the pit also that the pendant is swinging freely 
 at the time ; when it comes to rest, read off the number of 
 degrees and make a note of the result. In some cases, 
 as beneath a ledge of rock, in a mine, or in a cavern, it 
 is more convenient to take the dip from the under-sur- 
 face of a bed, when, by the upper edge of an ordinary 
 clinometer, or by the inversion of the compass-form of 
 instrument, the same result may be obtained. In other 
 cases neither the upper- nor under-surface of a bed can 
 be got at without much labour, when the hammer- 
 handle or stick should be held along the exposed face, 
 as nearly as may be in the line of the bed, and the 
 clinometer placed thereon. Again, beds may be ex- 
 posed in cliffs or deep pits, at such a height or in such 
 a position as to be not readily accessible ; under these 
 circumstances, the observer should take his stand at a 
 good distance from the face of the cliff or quarry, at 
 right angles, or thereabouts, to the spot where he wishes 
 the dip to be determined. Holding the instrument 
 
42 FIELD GEOLOGY. 
 
 steadily before his eye, lie inclines it until its edge coin- 
 cides with the bed being observed, and then reads off 
 as quickly as possible the angle indicated, and before 
 the position of the clinometer is shifted; to ensure 
 accuracy by this method, two or more observations 
 should be made and the results compared. 
 
 In the two last-named instances the exposed face, 
 accessible and inaccessible the apparent dip is taken; 
 this may or may not be the true dip, which can be 
 greater, but cannot be less than that of the exposure. 
 Wherever possible, and unless the observer be certain 
 that he is getting the true dip, he should make two ob- 
 servations, the direction of one at a considerable angle 
 from that of the other, and work out the true dip by 
 one of the methods given in the following pages. 
 
 The final results of observations taken with the cli- 
 nometer the amount and direction of the dip (if any) 
 of a bed or formation are shown on the map by the 
 symbols given in the table at page 33, drawn in vacant 
 spaces as near as possible to the spot where the sections 
 are exposed. 
 
 To find direction of Dip, by diagram. When the 
 amount and direction of two lines of apparent dip are 
 known, the direction of the true dip may readily be 
 found by one of the following Kules, A or B. 
 
 EULE A. When both the observed dips incline from 
 or towards the angle enclosed by their lines, fig. 11, the 
 true dip is at right angles to a line (a b) laid down by 
 the following method: 
 
 Set off from the angle on each of the two lines of ap- 
 parent dip a number of units corresponding to the 
 
GEOLOGICAL SECTIONS. 43 
 
 number of degrees of dip observed along the other line, 
 and connect the two points by a line a b. 
 
 Fig. 11. 
 
 (This line coincides with the strike, and is conse- 
 quently at right angles to the true dip's direction.) 
 
 EULE B. When one observed dip inclines from, and 
 
 Fig. 12. 
 
 the other towards the angle enclosed by their lines, 
 fig. 12, the true dip follows a line (c d) laid down by the 
 following method : 
 
 Set off from the angle on each of the two lines of 
 apparent dip a number of units corresponding to the 
 number of degrees of dip observed along that line, and 
 connect the two points by a line c d. 
 
 (This line coincides with the true dip's direction.) 
 
44 FIELD GEOLOGY. 
 
 Note. These rules will not apply, unaltered, to 
 lines of apparent dip, enclosing acute angles which 
 in practice are rarely found, but to right angles and 
 all beyond they are applicable. In such cases, a 
 horizontal triangle constructed by the reverse rule, 
 i.e., on the opposite side of either line of observed 
 dip, will give the result required. (See the N.E.. 
 corner of quarry, fig. 14, as an illustration.) 
 
 Fig. 13. 
 
 From the preceding two rules a general one may be 
 drawn, and which as an aid to memory of the others 
 may be of service. When the apparent dips cross each 
 other, as in a (fig. 13), the dip crosses the line which 
 will be drawn by Eule A. When all run in the same- 
 direction, 6, the dip coincides with the line drawn by 
 Eule B. 
 
 Note. When any part of the section-face shows 
 the beds in a horizontal position, the true dip (if 
 any) is of course at right angles thereto, and no> 
 further trouble need be taken. 
 
 The quarry represented in fig. 14 may be taken as an 
 example of obtaining the true dip by these method s, 
 the operation being repeated, and in each case with the 
 same result. 
 
GEOLOGICAL SECTIONS. 
 
 45 
 
 Fig. 14. 
 
 To find amount of Dip, by diagram. For examples 
 of this, the cases in which the direction of dip was 
 
 NOTE. The foregoing Rules were first published by the 
 Author in a communication to the " Geological Magazine " for 
 May, 1876 (p. 236). Mr. O. Fisher, after a careful examination 
 of the methods suggested, wrote to say that " Rule A is correct 
 for small dips for all practical purposes. It is not necessary that 
 the angle between the faces of the quarry should be obtuse. The 
 rule is equally true whatever be the angle. But Rule B, I am 
 afraid, is not correct. I should suggest the following mode of 
 applying the rule in case B." 
 
46 FIELD GEOLOGY. 
 
 found by Eules A and B may be taken figs. 11 and 
 12. 
 
 Construct (fig. 15) a right-angled triangle, which shall 
 
 Fig. 15. 
 represent the apparent dip on the part of an exposed 
 
 " Draw from any point M in the 
 quarry, M N parallel to the face OB, 
 and set off M N so that dip in O B : 
 dip in O A : : O M : M N. Then 
 O N is the direction of the strike" 
 
 In the "Geol. Magazine" for June* 
 1876, Mr. H. G. Day suggests, "In 
 the first rule (A), instead of 'the 
 number of degrees of dip/ write * the 
 tangent of the angle of apparent 
 dip.' In the second rule (B), proceed 
 as before, but measure the length 
 along one of the lines produced backwards." 
 
 There is a slight error arising from the difference between the 
 circular measure of the angle and the tangent of that angle but 
 in most cases it may be disregarded. And instead of adopting 
 Eule B when " one observed dip inclines from, and the other to- 
 wards the angle enclosed by their lines/' it will be well to work 
 out the dip from a horizontal triangle constructed on the other 
 side of one of the lines. Both apparent dips will then run either 
 from or towards the angle, and Eule A can be applied ; as, for 
 instance, B C in the figure, instead of BOA, the angle of the 
 quarry. 
 
GEOLOGICAL SECTIONS. 47 
 
 face, where it has been observed (in this case 20), and 
 the direction of true dip found, by Eule A. Let the 
 face-line itself form the base (a e, fig. 15, or c e, 
 fig. 16) of the triangle, thus saving trouble, and making 
 the method, perhaps, more readily understood. It is 
 found that in the distance a e (or c e, fig. 16) the 
 bed rises a certain number of feet or inches, but along 
 the line of true dip, e / (or c d, fig. 16), it of course 
 rises the same number of feet or inches. Set off this 
 amount of rise then at right angles to the true dip as 
 in the other case it is at right angles to the apparent 
 dip and draw a line from the point g, thus marked 
 off, to the point e (or c, fig. 16), where the rise com- 
 mences, the angle enclosed (25, fig. 15, and 21, fig. 16) 
 is the measure of the true dip. It must necessarily be 
 
 Fig. 16. 
 
 a greater angle than that of the apparent dips observed, 
 because the bed rises to the same height in a shorter 
 distance. 
 
48 
 
 FIELD GEOLOGY. 
 
 The same method applies whether the line of true 
 dip has been found by Eule A or B, and the angle re- 
 
 33 
 
 \ 
 
 4! 
 
 N\!8?W. 
 
 B 
 
 Fig. 17.* 
 
 quired can be found from either of the apparent dips, or 
 it can be worked out from both as a check upon the 
 result. 
 
 * For the loan of this woodcut, and another (fig. 20), the author 
 is indebted to the Editors of the " Geological Magazine." 
 
GEOLOGICAL SECTIONS. 49 
 
 The following method of finding by diagram, " from 
 two apparent dips the full dip and, its direction," was 
 published by Mr. W. H. Dalton, of H.M. Geol. Survey, 
 in the " Geological Magazine."* 
 
 Problem. From two apparent dips to find the full 
 dip and its direction (fig. 17). 
 
 Suppose two apparent dips, 41 N.W. and 33 N". 
 30 E. 
 
 Eesult, 44 J K 18W. 
 
 Draw B A, B c in the directions of the apparent dips ; 
 erect B D, B E vertical to B A, B c respectively, and equal 
 to each other. From D, E, draw D A, E c, making BAD, 
 B c E equal to the apparent angles whose direction is 
 shown by B A, B c respectively. Join A c, and draw B F 
 vertical to it. Draw B G parallel to A c, and equal to 
 B E ; join F G. 
 
 Then B F is the direction of the full dip, and G F B 
 its amount. 
 
 Proof. If A B c be placed horizontally and A B D, 
 B c E, B F G vertically, D G and E will coincide, and D A, 
 <2 F, E c and A c will be in the plane of stratification, 
 giving the apparent angles at A and c and the full dip 
 at F. In practice, the triangle B G F might be more 
 cxpeditiously constructed between B F and A c. 
 
 From any two observed dips the amount and direc- 
 tion of the true dip may be ascertained by calculation ; 
 but for all practical purposes the results obtained by 
 diagram are sufficiently accurate and much more expe- 
 ditious. 
 
 * Vol. x., No. 7, p. 332. 
 
50 
 
 FIELD GEOLOGY. 
 
 TABLE OF DIP, DEPTH, AND THICKNESS. 
 
 Proportionate 
 Incline. 
 
 Yards of 
 Rise or Fall 
 in 1 mile. 
 
 Amount of 
 Dip. 
 
 Degrees. 
 
 Depth from 
 Surface. 
 Distance=100. 
 
 Thickness of 
 Beds at 
 right angles. 
 
 1 in 57' 
 
 30 
 
 1 
 
 1-75 
 
 1-75 
 
 1 in 29- 
 
 60 
 
 2 
 
 3-45 
 
 3-45 
 
 1 in 19- 
 
 90 
 
 00 
 
 O 
 
 5-25 
 
 5-25 
 
 1 in 15- 
 
 118 
 
 4 
 
 6-75 
 
 G-75 
 
 1 in 12- 
 
 147 
 
 5 
 
 8-75 
 
 8-75 
 
 1 in 10- 
 
 176 
 
 6 
 
 10-5 
 
 10-5 
 
 1 in 8-5 
 
 208 
 
 7 
 
 12-5 
 
 12-25 
 
 1 in 7'3 
 
 240 
 
 8 
 
 14-5 
 
 14-25 
 
 1 in 6-5 
 
 270 
 
 9 
 
 16-5 
 
 16-25 
 
 1 in 5-8 
 
 300 
 
 10 
 
 17-75 
 
 17-5 
 
 1 in 5-25 
 
 333 
 
 11 
 
 19-75 
 
 19-25 
 
 1 in 5- 
 
 365 
 
 12 
 
 21-25 
 
 20-75 
 
 1 in 4-5 
 
 397 
 
 13 
 
 23-25 
 
 22-5 
 
 Iin4- 
 
 430 
 
 14 
 
 25- 
 
 24-25 
 
 1 in 3-8 
 
 463 
 
 15 
 
 26-75 
 
 26- 
 
 1 in 3-5 
 
 495 
 
 16 
 
 28-5 
 
 27'75 
 
 1 in 3-3 
 
 528 
 
 17 
 
 30- 
 
 29-25 
 
 1 in 31 
 
 560 
 
 18 
 
 32-3 
 
 31-3 
 
 1 in 3- 
 
 594 
 
 19 
 
 33-5 
 
 32-5 
 
 1 in 2-8 
 
 630 
 
 20 
 
 35-7 
 
 34-25 
 
 1 in 2-6 
 
 665 
 
 21 
 
 38-25 
 
 36-0 
 
 1 in 2-5 
 
 700 
 
 22 
 
 40- 
 
 37-75 
 
 1 in 2-4 
 
 735 
 
 23 
 
 417 
 
 39-5 
 
 1 in 2-3 
 
 770 
 
 24 
 
 43-5 
 
 41- 
 
 1 in 2-2 
 
 805 
 
 25 
 
 45-5 
 
 42-25 
 
 1 in 21 
 
 842 
 
 26 
 
 48- 
 
 43-75 
 
 Iin2- 
 
 880 
 
 27 
 
 50- 
 
 45-25 
 
 1 in 1-9 
 
 925 
 
 28 
 
 52-5 
 
 47- 
 
 1 in 1-8 
 
 970 
 
 29 
 
 55-5 
 
 48-25 
 
GEOLOGICAL SECTIONS. 
 
 51 
 
 TABLE OF DIP, DEPTH, AND THICKNESS continued. 
 
 Proportionate 
 Incline. 
 
 Yards of 
 Rise or Fall 
 in 1 mile. 
 
 i Amount of 
 Dip. 
 Degrees. 
 
 Depth from 
 Surface. 
 Distance=100 
 
 Thickness of 
 Beds at 
 right angles. 
 
 
 fl 
 
 
 
 1 in 17 
 
 1015 
 
 30 
 
 59' 
 
 50- 
 
 1 in 1'65 
 
 1060 
 
 31 
 
 60-6 
 
 51-25 
 
 1 in 1-6 
 
 1105 
 
 32 
 
 62- 
 
 5275 
 
 1 in 1-54 
 
 1150 
 
 33 
 
 65- 
 
 54-25 
 
 1 in 1-48 
 
 1195 
 
 34 
 
 67-5 
 
 56- 
 
 1 in 1-43 
 
 1240 
 
 35 
 
 70- 
 
 57-5 
 
 1 in 1-37 
 
 1285 
 
 36 
 
 73- 
 
 58-75 
 
 1 in 1-33 
 
 1335 
 
 37 
 
 75-2 
 
 60- 
 
 1 in 1-28 
 
 1385 
 
 38 
 
 78- 
 
 61-25 
 
 1 in 1-22 
 
 1435 
 
 39 
 
 81-6 
 
 6275 
 
 1 in 118 
 
 1490 
 
 40 
 
 84-8 
 
 64-5 
 
 linl- 
 
 1760 
 
 45 
 
 100- 
 
 71- 
 
 
 2095 
 
 50 
 
 119- 
 
 77- 
 
 
 2515 
 
 55 
 
 143- 
 
 82- 
 
 1 in -67=| 
 
 2640 
 
 56 
 
 150: 
 
 83- 
 
 
 3060 
 
 60 
 
 174- 
 
 86-5 
 
 1 in -5-i 
 
 3520 
 
 63 
 
 200- 
 
 89- 
 
 
 3765 
 
 65 
 
 214- 
 
 90-5 
 
 
 4840 
 
 70 
 
 275- 
 
 94- 
 
 1 in -33 = 1 
 
 5280 
 
 71 
 
 300- 
 
 94-5 
 
 
 6475 
 
 75 
 
 368- 
 
 96-5 
 
 1 in-25=rj 
 
 7040 
 
 76 
 
 400- 
 
 97' 
 
 1 in '20=^ 
 
 8800 
 
 79 C 
 
 500- 
 
 98- 
 
 
 10120 
 
 80 
 
 575- 
 
 98-5 
 
 lin-l= T V 
 
 17600 
 
 84 
 
 1000- 
 
 99-5 
 
 
 20115 
 
 85 
 
 1140- 
 
 100- 
 
 Not-. Messrs. Troughton and Simms, of Fleet Street, London, prepared (at 
 the suggestion of the late Mr. Jukes) a little ivory protractor (p 9) 011 which 
 portions of similar Tables to the above are engraved, together with the scales^of 
 the six-inch and one-inch maps, and which the observer will find very useful "to 
 have in his note-book or map-case. Its price is 10s. 
 
 42 
 
52 FIELD GEOLOGY. 
 
 The foregoing table has been prepared for the pur- 
 pose of getting an approximate idea of the rise or fall 
 of the ground in a certain distance, or of the depth to 
 which a bed with ascertained dip may have descended 
 at any particular spot, and the consequent thickness of 
 the beds above it. The centre column gives the angle 
 of inclination of the beds or of the surface, the columns 
 on the left hand the proportion of rise or fall, as the 
 case may be ; those on the right the vertical depth to a 
 bed at 100 units from its outcrop, and the actual thick- 
 ness of the beds above, supposing them to have been in 
 their original plane of stratification. These 100 units 
 are measured along a horizontal surface in the direc- 
 tion of its dip, and allowance has of course to be made 
 for rise or fall of the ground, if uneven between the 
 points. 
 
 Exposed Sections. In the examination of the rocks 
 exposed in quarries, pits, and so on, we make a definite 
 series of observations. On entering we should probably 
 have in our mind a general idea of what we are going to 
 see (except in a district quite new to us), from former 
 experience of the rocks in the neighbourhood, or from 
 what might otherwise be reasonably expected. We 
 should also infer from the kind of excavation in what 
 material it had been made as, for instance, a brick-yard, 
 which would be in clay or loam of some kind ; a lime- 
 kiln in limestone, whether of compact nature as the 
 41 Lias," or earthy as the " Chalk." In a glance round 
 the excavation we get further ideas of the general 
 character and lie of the beds, and we then proceed to 
 make more detailed examination. 
 
 Note. Eailway cuttings often afford excellent 
 
GEOLOGICAL SECTIONS. 53 
 
 means of observing the strata ; although perhaps not 
 of great depth, their length is sufficient to bring on, 
 it may be, several beds that are slightly out of hori- 
 zontal position, and to show them in their actual 
 superposition. 
 
 The points of which special notes have to be made 
 are, the kind of rock of which the bed or series of beds 
 consists ; the number, thickness, and sequence of those 
 beds, their apparent dip and its .bearing ; also the true 
 dip if it can be obtained. All peculiarities must be 
 sought out and noted, such as false- or current-bedding, 
 cleavage, concretions, signs of fracture, slickensides, and 
 so on the lines of bedding and jointing observed, and, 
 in short, anything and everything that can be detected 
 and described. (The modes of determining the nature of 
 the rocks are described in Part III. ; and of finding, col- 
 lecting, and preserving the included fossils, in Part IV.) 
 Notes. As illustrations of the manner in which pit 
 sections are observed and noted, we may select those that 
 occur in the area supposed to have been surveyed, and 
 which is represented in figs. 5, 6, 7, and 8. In the first 
 slip, fig. 5, soon after starting, we came upon an old pit, 
 nearly overgrown, but of which some notes must be taken, 
 (a.) In the lowest part of this pit we find, after re- 
 moval of the fallen soil, a fair section of fine light sand, 
 with many green-looking grains scattered amongst its 
 other component particles. Some lines of bedding can 
 just be made out, and these appear to be horizcfntal or 
 nearly so, but they are not defined sufficiently for a dip 
 to be taken from them, and in one place a thin broken- 
 up seam of harder sand, almost a stone, occurs. Some 
 elongated lumps of whitish material are imbedded in the 
 
54 FIELD GEOLOGY. 
 
 harder sand, and which, on being broken across, present 
 a sponge-like appearance. These evidently are, or were, 
 organisms of some kind, and are transferred to the fossil 
 bag for future investigation. 
 
 The top part of the S. side of the pit is in soft marly 
 chalk, and as we dig down the slope this chalk gets 
 darker in colour, owing, it would seem, to the number 
 of green grains enclosed in it. Presently we come down 
 to the grey sand with green grains, but without having 
 noticed any sudden change where the one rock rests 
 upon the other. There is in fact a gradual passage from 
 the chalk into the sand, representing an equally gradual 
 change in the conditions of deposit. Still there is clean 
 chalk above, and clean sand below, therefore this pas- 
 sage portion represents the junction, and the line is con- 
 sequently drawn through that part of the map where 
 the pit is situated. These observations may be noted 
 in the following manner : 
 Date 187 . 
 
 (Old) Sand-pit J furlong K of church. 
 
 (About) 10 feet, fine light-coloured sand, with 
 
 green grains, apparently horizontal, including a 
 
 thin seam of broken sandstone (with ? sponges). 
 Chalk marl, with green grains, comes on at the 
 
 S. side, and passes down into the sand. 
 
 FOSSILS (determined in Part IV. Chap. iii.). 
 ( Terebratula 
 
 Uiropr 
 Upper 
 
 Green-sand. .,. , 7 
 Phcatula 
 
 {^Ammonites 
 
GEOLOGICAL SECTIONS. 
 
 c Terebratula 
 Olialk-maii. -j Inoceramus 
 v Belemnites 
 
 (6.) The brick-yard beyond the stream (fig. 5) was 
 found to be situated on a clay ; this on examination 
 proves to be Gault. It is a tenacious clay, in colour 
 dark blue where freshly cut, but weathering to a light 
 grey on exposure. No traces of bedding are visible, 
 unless a thin horizontal layer of rounded grey nodules 
 which occurs in one part, and is tolerably persistent 
 throughout the pit, affords such indication. 
 
 Date ........ 187 . 
 
 Brick-yard J mile N. of 
 
 church. 
 
 17 feet, dark blue tenacious clay (weathers grey), 
 ? horizontal about 7 feet from bottom 1 layer of 
 phosphatic nodules, shells, and casts. 
 
 Gault. 
 
 FOSSILS. 
 
 'Ammonites varicosus splendens ros- 
 -tratus 
 
 Hamites 
 
 Belemnites attenuatus 
 Rostellaria 
 Solarium ornatum 
 Plicatula pectenoides 
 Avicula gryphceoides 
 Inoceramus sulcatus 
 Nucula pectinata 
 Pentacrinus Fittoni 
 
56 FIELD GEOLOGY. 
 
 (c.) Date 187 . 
 
 New Well J mile S.E. of church. 
 
 (Information obtained from the well-sinker.) 
 
 C 107 feet, dark blue Gault, with some 
 Gault. -J seams of nodules. 
 
 1 foot hard bed 
 Lower Green-sand 2 feet running sand 
 
 110 feet=Dug 50 feet, bored 60 feet. 
 
 Water stands 30 feet from surface. 
 
 (d.) No pit sections occurred in the second slip, but 
 in the third was a large chalk-pit, just on the highest 
 point of the escarpment. Here we see that a great deal 
 of the rock is being daily removed, most of it converted 
 into lime at the kiln within the pit, some portions carted 
 away for road-making, others for building purposes. 
 The vertical face of this chalk section presents a pleas- 
 ing picture, and is in itself quite a study ; it would 
 afford ample materials for a geological lecture. The 
 rock itself, of snowy whiteness, made up apparently, 
 but only to the naked eye, of minute grains of inorganic 
 dust; the even bands of flint nodules, which, being broken 
 across in the quarrying, look like black lines ruled across 
 the chalk ; the " slicken-sided " joints and the little 
 faults and fractures which here and there occur. Above 
 are two funnel-shaped masses of sandy gravel, running 
 down several feet into the chalk ; lower down a circular 
 patch quite surrounded by it. This latter proves to be 
 only an offshoot from one of the others, but which 
 having deviated from the perpendicular has been cut 
 directly across. These are " pipes " of gravel, filling. 
 
GEOLOGICAL SECTIONS. 57 
 
 hollows in the chalk that have been made by rain-water 
 holding in solution carbonic acid, and which, percolating 
 through into a fissure, has increased the size of its pas- 
 sage by removal, as a bi-carbonate, of a portion of the 
 rock. At some former time the surface must have been 
 covered with a gravel ; these are its only relics here, 
 the bulk of the deposit having been removed by subse- 
 quent denudation. 
 
 We are informed that the pit is forty feet deep, and 
 we approximately verify the statement by counting the 
 spaces between the layers of flint, which are, as nearly 
 as may be, six feet apart ; also that the lower part of 
 the chalk in the pit is that which is used for building. 
 On examination this proves to be somewhat harder 
 than the other portions, and it breaks up into larger 
 blocks; but, with the exception of a slightly yellow 
 tinge that it possesses, it is just the same in appearance. 
 Specimens of each kind are chipped out, to be taken 
 away with us, that they may be submitted to test and 
 experiment. 
 
 The next proceeding is to select a suitable part of 
 one of the flint layers (in this case on the E. side of the 
 pit), to place our hammer-handle thereon in the same 
 line, and on this again the clinometer the angle of dip 
 reads 3, somewhere in a S. direction. Then we try to 
 get another observation at right angles, or nearly so, to 
 the first at the N. end without success, but on the S. 
 we are enabled to do so by removing some fallen rub- 
 bish. This reads 0, consequently the first observation 
 has given us the true dip of the beds, and the E. side 
 of the pit happens to have been cut in its direction. 
 We take this direction by compass-bearing, it proves to 
 
58 FIELD GEOLOGY. 
 
 be S. 7 E., and we draw on the map, and near the posi- 
 tion of the pit, an arrow pointing S. 7 E., with the 
 number of degrees of dip also shewn (p. 33). 
 
 We observe that the chalk is jointed in every direc- 
 tion, and that the surfaces of some of the joints, diagonal 
 and vertical, are of a dirty yellow colour, and covered 
 with small strise, as though one face of the jointed rock 
 had slipped over the opposing face, both getting smoothed 
 and striated in the process. This is what has happened, 
 the resulting appearance being known as " slickenside " 
 the chalk has been at some period subjected to slight 
 disturbance this is further evidenced by the small 
 fractures and faults. In the S.E. corner one of the 
 latter is plainly shewn on a small scale, the downthrow 
 not exceeding 1 foot the continuity of the lines of flint 
 being broken, all of them suddenly rising to that extent. 
 
 All the flints are black but have a thin white coating 
 the majority occur in nodules of varying size, from 
 that of a hen's egg to a quartern loaf, but one seam is 
 tabular, that is, it consists of an almost continuous stratum 
 of flint about 1J inches in thickness. Similar flint in 
 tabular form occasionally is seen running away from 
 this seam down the diagonal or vertical joints, and 
 sometimes even cutting directly across a layer of flint 
 nodules. 
 
 Date 187 . 
 
 Chalk pit (and lime-kiln) mile of 
 
 (at junction of the road with old Eoman way). 
 40 feet chalk with flints in layers about 6 feet apart 
 
 dipping 3 to S. 7 E. slightly faulted and broken up 
 
 into blocks of small size. One layer of flint, near the 
 
 bottom, tabular and running off into the joints, which 
 
GEOLOGICAL SECTIONS. 59 
 
 are occasionally slicken-sided. The lowest part of the 
 chalk is harder, in large blocks, and of a yellowish 
 tint (used for building). 
 
 Pipes of a ferruginous sandy gravel at the top. 
 
 FOSSILS. 
 
 Ananchytes Marsupites Mulleri 
 
 Micraster Crania 
 
 Cidaris (spines) Plicatula 
 
 Belemnites Thecidium Wetherellii 
 
 Inoceramus Serpula 
 
 Spondylus Polyzoa 
 
 Magas pumila 
 
 Terebratula carnea 
 
 Terebratulina striata 
 
 Rliynconella octoplicata 
 
 The sections observed during the survey of the fourth 
 
 slip are given below as noted in the book at the time, 
 
 no additional remarks being considered necessary. 
 
 Date 187 . 
 
 (e.) Eoad cutting J mile S. of Windmill. 
 
 Loam, mottled, yellow, red and brown. 
 
 (thin bed) Dark clay, with green-coated flint pebbles. 
 Chalk. 
 
 No measurements of thickness obtainable. 
 
 {Memo :* This loam is evidently a lenticular mass be- 
 tween the chalk and the grey sand which come to- 
 gether a short distance off to the W. (see p. 27), 
 and probably to the E. also. See map, and notes 
 farther on. 
 
 * Made at a later date. 
 
60 FIELD GEOLOGY. 
 
 Date 187 . 
 
 (/.) Brick-yard f mile S. of junction with the 
 
 Eoman road. 
 
 13 feet Loam, mottled, yellow red and brown (similar 
 to that seen in road cutting about 2 miles E.) with 
 intercalated patches of white and yellow sand ; pas- 
 sing down into 
 
 1 foot, dark brown very tenacious Clay, which encloses 
 many angular and rolled flints with green-coating, 
 and rests on an uneven surface of (exposed about 9 feet) 
 Chalk with flints, in layers 5 or 6 feet apart, and 
 dipping 3 to S. 7 E. 
 
 Grey sand occurs just S. of this pit (p. 27) and overlies 
 the loam. 
 
 FOSSILS (from the mottled loam), 
 Ostrea 
 
 Cyrena cordata 
 Ostrea bellovacina (in basement bed). 
 
 (g.) Sand pit (small) near S.E. corner of the sheet. 
 About 4 feet (not bottomed). Pale grey sand, very clean 
 and evidently dug for purposes of building, rather darker 
 in the lower portion. (There is a pond close by which 
 probably indicates a change' at no great depth to a de- 
 posit of loam or clay.) 
 
HORIZONTAL SECTIONS. 61 
 
 '-J JVUA Jil 
 
 UNIVERSITY < 
 
 CHAPTER IIJl 
 
 CALIFORNIA 
 
 HORIZONTAL ~ 
 
 Datum-level Bench-marks Levelling, by Aneroid, by Level 
 Level-book Plotting, from heights Levelling, by Theodolite 
 Level-book Plotting, from angles Filling in Geology 
 Apparent dip. 
 
 IN constructing a geological section it is most important 
 to have the surface of the ground along the line of such 
 section accurately represented ; for if not, error is sure 
 to creep in, where perhaps least expected, as might easily 
 happen in such an instance as this. A road runs along 
 the line of a proposed section at one part A, a pit by 
 the roadside exposes a limestone 1 foot thick, with shale 
 above and below; by the clinometer it is found that this 
 bed is perfectly horizontal. The road appears to the 
 eye to be horizontal also, but in reality it rises at the 
 slight angle of half a degree. A mile farther on another 
 pit, similar to the first, shews a limestone 1 foot thick, 
 with shales above and below, just the same as at A, also 
 horizontal. The beds seen in the two pits are surely 
 identical, at least it seems natural to come to that con- 
 clusion ; but in reality the bed seen at A is here at B, 
 owing to the slight rise, actually from 40 to 50 feet 
 beneath the surface. It might even happen that the 
 higher of two beds would be shewn passing under the 
 other were the surface judged merely by the eye ; there- 
 fore, if error is to be avoided, the section must be drawn 
 from ascertained data or by the aid of some instrument. 
 There are many means by which a line can be drawn 
 
62 FIELD GEOLOGY. 
 
 that shall represent the surface through any number of 
 given points by some approximately and in a sketchy 
 manner, by others every detail is shewn with the greatest 
 accuracy. Among the former are the methods employed 
 in drawing section lines from the published " heights 
 above the sea," from contour maps, and from heights 
 taken by aneroid barometer; the latter, from levels 
 ascertained by the Y, the dumpy or any other level, 
 and from a series of vertical angles observed by means 
 of the theodolite. All proceed on the same principle of 
 ascertaining the heights at various points, near to or 
 distant from each other, according to the degree of 
 accuracy required, and sketching in the line between 
 those points to correspond as nearly as may be with the 
 surface form of the ground. A few brief remarks will 
 follow on the use of the level and theodolite, for geolo- 
 gical purposes. Before the levels for a geological section 
 are run, the beds have generally been mapped, and the 
 line should be laid out as nearly as can be conveniently 
 arranged at right angles to the strike. For approximate 
 levelling the distances apart of the points where heights 
 are taken can be scaled from the map ; for accurate 
 work, measurements by chain are required. 
 
 Datum-level. By whatever means the heights or 
 levels for a section are taken, it is necessary to have a 
 fixed or standard level to commence from, to which 
 reference can at any time be made, and in regard to 
 which all the other heights are calculated. It is usual, 
 as it is most convenient, to refer all heights to the stand- 
 ard, or as it is called, the " datum-level " adopted for this 
 country, that is, the " level of the sea." By this term 
 is understood the level of mean tide at Liverpool, a datum 
 
HORIZONTAL SECTIONS. 63 
 
 from which all the heights marked on the ordnance maps 
 have been calculated. But in some instances it is found 
 more convenient to work from an imaginary horizontal 
 line, as datum, so many feet above or below this stand- 
 ard ; in others, to take a fixed point on some permanent 
 structure, as a church, or a bridge, and to commence 
 therefrom an imaginary datum. In geological sections, 
 which frequently shew the strata far beneath the sea- level, 
 it is usual, as in those published by the Government 
 Survey, to assume a datum, " 1000 feet below the level 
 of the sea." 
 
 Bench marks. Here and there along a line of section, 
 or elsewhere, a series of intermediate points are selected, 
 as " bench marks," for the sake of more convenient local 
 reference at any future time. The heights of these 
 points above or below datum are known from the ord- 
 nance levelling, from our own observations, or otherwise, 
 and their positions are indicated or described. All the 
 points on the ordnance maps, where heights are figured, 
 are so many bench marks, the levels of each having been 
 carefully ascertained, and the result checked by re- 
 petition and calculation. 
 
 It is not always necessary, nor is it always possible, 
 to obtain a B. M. of known height above, the sea, from 
 which to commence a proposed line of geological section ; 
 in such cases a" fixed local starting-point must be selected. 
 If near home, as good a B. M. as any is the step of one's 
 front door, and for aneroid observations, perhaps frequently 
 taken for other purposes than a continuous section, none 
 could be better. While running a section line, started 
 from a local B. M., we may possibly come across one of 
 the ordnance heights ; this will enable us, if desired, to 
 
64 FIELD GEOLOGY. 
 
 reduce our results to " sea-level," even from the com- 
 mencement. 
 
 LEVELLING. 
 
 By Aneroid. The possibility of taking heights by 
 this instrument is, of course, based on the weight, gener- 
 ally termed pressure, of the atmosphere, which varies as 
 the height above the surface of the earth. B ut this pressure 
 is subject to almost constant change, at the same place, 
 and at the same height, owing to varying atmospheric 
 conditions of wind, moisture, and so on. Therefore 
 some means must be adopted, when levelling by the 
 aneroid, to compensate for any change that may occur 
 during the time of making the observations, and by 
 which cause, in addition to the difference of height, the 
 needle would be deflected. 
 
 The circumference of the aneroid barometer is grad- 
 uated to inches and hundredths, and on this scale the 
 needle indicates the varying measure of a column of 
 mercury, that would be sustained or counter-balanced 
 by the changing weight of the atmosphere. Generally 
 it has also a movable circumference, divided into parts, 
 about 950 of which correspond with 1 inch on the 
 pressure scale ; because a column of air, about 950 feet 
 high, is equal in weight to a similar column of mercury, 
 which measures 1 inch in height. Therefore, as the 
 mercury in an ordinary barometer would "fall 1 inch for 
 every 950 feet higher, or rise for 950 feet lower, the 
 needle of an aneroid gives equivalent indications on this 
 outer circumference, which thus saves the labour of cal- 
 culation. 
 
 At starting, the zero point of the circumference must 
 be brought round to a position exactly opposite the point 
 
HORIZONTAL SECTIONS. 65 
 
 of the needle, the observer standing at the time on the 
 selected bench mark ; the instrument should have been 
 previously carried about the person for a few minutes, so 
 that the difference of temperature may take effect, if at 
 all, before and not after this adjustment. 
 
 On arrival at each point where an observation should 
 be made, as the summit of a hill, the bottom of a valley, 
 the site of an exposed section, and so on, note is made of 
 the variation of the needle-point as a rise or fall of 
 pressure, if the instrument is graduated for pressure 
 only ; as so many feet higher or lower, if also for eleva- 
 tion. The indicator is not to be shifted at each station, 
 but the height of every one taken as so much above or 
 below the B. M. chosen for a starting-point as stated 
 before, these heights will not be correct if the atmo- 
 spheric pressure has changed in the meantime. Three 
 methods are given for the rectification of error arising 
 from this cause ; a and 6, being of the simpler kind, 
 will give fair results ; should greater accuracy be required, 
 c must be adopted. 
 
 (a.) If the observer can return home along the route 
 by which he came out, and has the time at command for 
 making a second series of observations at each point, the 
 error arising from atmospheric change may be to some 
 extent eliminated. The indicator must remain in the 
 same position as at starting, and the heights on return- 
 ing be again taken in reference to the primary bench 
 mark. For example, suppose four points on a line, at 
 which the two series of observations are as given below 
 (the sign + indicating that the instrument registers so 
 many feet above the starting-point, when below the sign 
 being prefixed). 
 
 5 
 
66 
 
 FIELD GEOLOGY. 
 
 1st series . . 
 2nd series . . 
 
 B.M. 
 
 o 
 
 + 30 
 
 1st (station) 
 
 2nd 
 
 Last 
 
 + 200 
 + 225 
 
 + 80 
 
 + 100 
 
 + 100 
 + 100 
 
 The barometer has evidently fallen during the time 
 through a space equal to 30 feet, making the B. M. ap- 
 pear to be 30 feet higher than at starting, and, as a 
 matter of course, the other stations too high also in due 
 proportion. We assume that the fall was gradual, and 
 equally distributed over every portion of the two 
 journeys ; therefore half 30 feet (i.e. 15 feet) must be 
 deducted from the mean of the two observations at each 
 place, the result gives the required elevation. 
 
 B.M. 1st 2nd Last 
 
 o +200 +80 + 100 
 
 + 30 + 225 + 100 + 100 
 
 J/ 30 y 425 y 180 |/ 200 
 
 Mean of two 1 .. - 
 
 observations j 
 
 Deduct error 15 
 
 Elevation 
 
 (6.) A somewhat similar method is to note the time 
 of starting (with the indicator at zero), and of making 
 each observation; then, on again reaching the home 
 B. M., without having gone more than once to each station, 
 to observe the time, and the rise or fall of the barometer. 
 This rise or fall must be distributed, in proportion to the 
 time that elapsed before each was taken, over the station 
 
HORIZONTAL SECTIONS. 67 
 
 heights, as additions to, or deductions from, the registered 
 elevation. 
 
 It will be seen that the foregoing methods a and b 
 are founded upon the assumption, that the atmospheric 
 rise or fall of the barometer has been consistent through- 
 out the time occupied in making the observations ; but 
 this probably has not been the case, for the pressure 
 may be increasing at one part of the day, and steady or 
 falling at another. The following method (c) is free 
 from this defect, and the accuracy of its results depends- 
 solely on the perfection of the instruments employed. 
 
 (c.) An assistant and two aneroids are required by 
 this method, the instruments of sufficient accuracy for 
 no perceptible difference between their indications to 
 arise under varying pressure. The readings are taken 
 at each station at some definite time, such as at the 
 hour, half-hour, or quarter; and the assistant, at home or 
 wherever the starting-point may have been, observes 
 and records the reading of the second instrument at the 
 same intervals. The two sets of observations are after- 
 wards compared, and those taken at the stations corrected 
 for variations, if any, of the atmospheric pressure. 
 
 By Level. The principle on which all levels are 
 constructed is that of a perfectly horizontal visual line 
 intersecting a graduated vertical staff, the difference of 
 readings in two observations corresponding to the 
 difference in level of the two places. If the height of 
 one of these be known, that of the other is readily 
 ascertained in relation thereto, and is called a " reduced 
 level." The difference between the heights of any 
 number of places may be thus determined, and the level 
 
 52 
 
68 FIELD GEOLOGY. 
 
 taken at each " reduced," by addition or subtraction, to 
 its height above or below the B. M. the height of this 
 being known, the levels are at once reduced to " datum- 
 level." 
 
 The level consists of a telescope supported on three 
 legs, and having a fine cross-wire placed horizontally in 
 the line of sight. A spirit-level is fixed on it parallel 
 to its axis, by means of which, and three (or four) plate 
 screws, the telescope can be adjusted so as to be perfectly 
 horizontal in whatever direction it may be turned. The 
 line of sight thus represents a horizontal plane, and the 
 cross-wire must necessarily, within certain limits, be 
 seen to intersect a distant object in the same plane with 
 itself. The observations are taken by means of a staff 
 placed on the stations in turn this staff is capable of 
 being extended to 14 feet in height and has one side 
 divided into feet and hundredths. Through the telescope 
 with the ordinary eye-piece it is seen inverted, but the 
 ye soon gets accustomed to reading it in this position ; 
 and being magnified the point cut by the cross-wire can 
 be accurately read off. 
 
 The distances apart of the various stations can be 
 measured by chain, or scaled from the map on which 
 the line of section has been laid down the correctness 
 of the height at each station is not affected by want of 
 accuracy in this respect, as it is when taken by the 
 theodolite. The instrument should always be placed 
 about mid-way between the two places at which back- 
 and fore-sights are being taken, to minimise the slight 
 error arising from " curvature " and " refraction." 
 
 As an example of levelling by this instrument we 
 may take the line of section running across the area 
 
HORIZONTAL SECTIONS. 69 
 
 surveyed (Part I.), commencing at a milestone in the 
 S.E. corner (fig. 8). On this the "broad-arrow" has 
 been cut and it is shewn thereby to be an Ordnance 
 Bench-mark, the height of which, above the sea, is 
 ascertained to be 365 feet. We may take the distances, 
 where our line crosses roads, brooks, and so on, from 
 the map, reserving the example of measuring by chain 
 for the theodolite illustration. But these points are too 
 far apart and at too great a difference of level for the 
 instrument to be placed once only between each two, 
 we must therefore take intermediate observations. 
 
 Note. In running a set of levels by this instru- 
 ment and scaling the distances of definite points 
 from the map (the intervening surface line being 
 sketched in by eye and hand), it is immaterial 
 whether the intermediate levels be taken along the 
 line or by a more convenient route, so that each of 
 these points be made a station for an observation. 
 The Bench-mark, that is, the milestone of which the 
 reduced level is known, must be the starting-point, and 
 having drawn on the map our proposed line therefrom 
 and passing by the church, we proceed in the following 
 manner. The instrument is set up on the road a few 
 chains from the B. M., and the plate-screws turned until 
 the spirit- tube indicates that its position is in every 
 direction horizontal. The assistant holds up the staff 
 upon the milestone, so that its base coincides with the 
 upper line of the " broad-arrow " and a reading is then 
 taken therefrom. This must be entered in the level- 
 book as a " back-sight" (10*90), and a second look taken 
 through the telescope for the purpose of checking the 
 accuracy of the first reading. The man then takes the 
 
'0 FIELD GEOLOGY. 
 
 staff on along the road, which runs about in the right 
 direction, to a distance roughly equal to that of the 
 instrument from the milestone. A reading is taken 
 upon it (210), entered as a "fore-sight," checked by a 
 second reading, and the level carried forward some chains 
 beyond the staff when all the operations are repeated. 
 The staff will then be turned round to face the instru- 
 ment in its new position, but care must be taken that 
 the back- and fore-sights are read off without other 
 alteration in its position. 
 
 The levelling is thus carried on by the road, just off 
 the real line, to the cross- ways, when it must be managed 
 for the staff to be placed on the road where it is cut by 
 the section line, this being one of the points to be scaled 
 from the map. Then the line is followed, or nearly so, 
 in the direction of the cottages by which it passes, down 
 the escarpment (where shorter sights will be necessary 
 owing to the rapid fall), by the well, across the brook, 
 past the church, and ends by the stream on the W. side 
 of the map. 
 
HORIZONTAL SECTIONS. 
 
 71 
 
 The level-book will best explain the manner in which 
 the details are observed and entered, as they come under 
 notice or require specification. 
 
 From . . . Milestone, 1ST. 35 W. passing by ... Church. 
 
 Back- 
 sight. 
 
 Inter- 
 me- 
 diate. 
 
 Fore- 
 sight. 
 
 Rise. 
 
 Fall. 
 
 Reduced 
 Level. 
 
 Dis- 
 tance. 
 
 Remarks. 
 
 
 
 
 
 
 365-00 
 
 
 B. M. Milestone. 
 
 10-90 
 
 
 2-10 8*80 
 
 
 
 
 
 12-17 
 
 
 1-50 
 
 10-67 
 
 
 
 
 
 33-00 
 
 
 40 
 
 12-60 
 
 
 
 
 
 12-08 
 
 
 i-oo 
 
 11-08 
 
 
 
 
 
 13-10 
 
 
 1-15 
 
 11-95 
 
 
 
 
 
 
 
 
 55-10 
 
 
 420-10 
 
 
 Boundary of 
 
 
 
 
 
 
 
 
 
 T i oflin 
 
 9-94 
 
 
 "74 
 
 9-20 
 
 
 
 
 J-j Ucij.il* 
 
 14-00 
 
 
 I'OO 
 
 13-00 
 
 
 
 
 
 12-50 
 
 
 40 
 
 12-10 
 
 
 
 
 
 11-60 
 
 
 66 
 
 10-94 
 
 
 
 
 
 9-90 
 
 
 no 
 
 8-80 
 
 
 
 
 
 9-10 
 
 
 73 
 
 8-37 
 
 
 
 
 
 9-63 
 
 
 2-00 
 
 7'63 
 
 
 
 
 
 
 
 
 
 70-04 
 
 
 490-14 
 
 
 Road. 
 
 12-08 
 
 
 40 
 
 11-68 
 
 
 
 
 
 14-00 
 
 
 08 
 
 13-92 
 
 
 
 
 
 13-4J 
 
 
 1-04 
 
 12-37 
 
 
 
 
 
 12-90 
 
 
 3-11 
 
 979 
 
 
 
 
 
 11*17 
 
 
 78 
 
 10-39 
 
 
 
 
 
 9-87 
 
 
 1-17 
 
 8-70 
 
 
 
 
 
 13-93 
 
 
 90 
 
 13-03 
 
 
 
 
 
 
 
 
 79-89 
 
 
 570-03 
 
 
 Top of Church 
 Escarpment. 
 
 5-03 
 
 
 718 
 
 
 215 
 
 
 
 370 
 
 
 8'10 
 
 
 4'40 
 
 
 
 2-40 
 
 
 10-90 
 
 
 8'50 
 
 _ 
 
 
 1-09 
 
 
 12-87 
 
 
 11-78 
 
 
 
 18 
 
 
 13-86 
 
 
 13-68 
 
 
 
 1-03 
 
 
 12-90 
 
 
 11-87 
 
 
 
FIELD GEOLOGY. 
 
 Back- j 
 sight. 
 
 Inter- 
 me- 
 diate. 
 
 Fore- 
 sight. 
 
 Rise. 
 
 Fall. 
 
 Deduced 
 Level. 
 
 Dis- 
 
 ance. 
 
 Remarks. 
 
 
 
 
 
 570-03 
 
 
 Top of Ck.Escarp. 
 
 1-10 
 
 
 13-00 
 
 
 11-90 
 
 
 
 
 04 
 
 
 1375 
 
 
 13-71 
 
 
 
 
 17 
 
 
 12-81 
 
 
 12-64 
 
 
 
 
 i-oo 
 
 
 13-80 
 
 
 12'80 
 
 
 
 
 2-25 
 
 
 10-70 
 
 
 8'45 
 
 
 
 
 
 
 
 
 111-88 
 
 458-15 
 
 
 Top of Lower Es- 
 
 370 
 
 
 8'05 
 
 
 4-35 
 
 
 
 carp incnt. 
 
 2-10 
 
 
 12-14 
 
 
 10-04 
 
 
 
 
 173 
 
 
 12-80 
 
 
 10-07 
 
 
 
 
 03 
 
 
 13-91 
 
 
 13-88 
 
 
 
 
 1-18 
 
 
 1276 
 
 
 11-58 
 
 
 
 
 93 
 
 
 13-01 
 
 
 12-08 
 
 
 
 
 10-08 
 
 
 371 
 
 6'37 
 
 
 
 
 
 3'18 
 
 
 8-20 
 
 
 5-02 
 
 
 
 . 
 
 I'll 
 
 
 1171 
 
 
 10-60 
 
 
 
 
 roo 
 
 
 12-90 
 
 
 11-90 
 
 
 
 
 2-11 
 
 
 13-11 
 
 
 ll'OO 
 
 
 
 
 19 
 
 
 13-21 
 
 
 13-02 
 
 
 
 
 1-30 
 
 
 11-40 
 
 
 10-10 
 
 
 
 
 2'00 
 
 
 12-10 
 
 
 10-10 
 
 
 
 
 
 
 
 6'37 
 
 13374 
 
 
 
 
 
 
 
 
 6-37 
 
 
 
 
 
 
 
 
 127-37 
 
 330-78 
 
 
 Boundary of 
 
 
 
 
 
 
 
 
 Plinllr 
 
 3'17 
 
 
 1275 
 
 
 9'58 
 
 
 
 V^ildlK.. 
 
 1-14 
 
 
 13-80 
 
 
 12-66 
 
 
 
 
 19 
 
 
 13-10 
 
 
 12-91 
 
 
 
 
 1'02 
 
 
 13-70 
 
 
 12-68 
 
 
 
 
 2-00 
 
 10-40 
 
 
 
 8-40 
 
 274-55 
 
 
 Boundary of U. 
 vTreGn-sand. 
 
 
 
 11-90 
 
 
 9-90 
 
 
 
 
 5'80 
 
 
 4-20 
 
 1-60 
 
 
 
 
 
 3-20 
 
 
 8-90 
 
 
 5-70 
 
 
 
 
 I'OO 
 
 
 12-81 
 
 
 11-81 
 
 
 
 
 I'll 
 
 
 13-00 
 
 
 11-89 
 
 
 
 
 03 
 
 
 13-41 
 
 
 13-38 
 
 
 
 
 1-08 
 
 
 13-85 
 
 
 12-77 
 
 
 
 
 1-17 
 
 
 1274 
 
 
 11-57 
 
 
 
 
HOBIZONTAL SECTIONS. 
 
 Back- 
 sight. 
 
 Inter- 
 me- 
 diate. 
 
 Fore- 
 sight. 
 
 Rise. 
 
 Fall. 
 
 Reduced 
 Level. 
 
 Dis- 
 tance 
 
 Remarks. 
 
 19 
 3-76 
 
 2-20 
 3-00 
 2-17 
 2'40 
 
 
 13-40 
 12-84 
 
 10-10 
 
 12-84 
 8-41 
 13-19 
 
 
 13-21 
 
 9-08 
 7-90 
 9'84 
 6-24 
 10-79 
 
 330-78 
 
 
 Boundary of 
 Chalk. 
 
 By Well (110 .feet 
 deep). 
 
 Stream. 
 
 1-08 
 
 2-68 
 
 197-00 
 
 
 
 150-27 
 
 1-60 
 
 182-11 
 1-60 
 
 180-51 
 
 The levelling is carried on in the same manner over 
 the chalk outlier, care "being taken to obtain the heights 
 at, or as nearly as possible upon, the geological boundaries. 
 
 It will be seen from the above example of a level- 
 book that the heights of certain definite stations only 
 are worked out those of the others being unnecessary, 
 and probably off the line. The method of procedure is, 
 to add up the " rises " and " falls," to subtract the smaller 
 sum from the larger the remainder to be added to or 
 deducted from the height of the last, station where it 
 was calculated, according to the predominance of " rise" 
 or " fall," as the case may be. In making the additions, 
 all " intermediate " sights are to be disregarded, the cal- 
 culations at those places being enclosed between two 
 lines to indicate that they are not to -be included. The 
 final result may be checked by adding together all the 
 " back- and fore-sights," deducting the one amount from 
 the other, and the result from, or adding it to, the last 
 height obtained. 
 
74 FIELD GEOLOGY. 
 
 Plotting from heights. Before considering a dif- 
 ferent style of taking surface levels, it will be well to 
 see how the results of the proceeding and similar obser- 
 vations are plotted ; that is, reduced to the form of a 
 representative drawing. The method in all of them is 
 the same, a straight line is drawn on the long slip of 
 paper usually employed, to represent the datum-level, 
 whether it be the sea-level, 1000 feet below it, or any 
 other that may be adopted. Along this line are set off 
 by scale the distances of each station in succession 
 and at right angles to it lines in pencil are drawn 
 through all these points. The reduced level of each 
 station is then scaled off along its vertical line and 
 another line is sketched in, running through all these 
 reduced level points, and as nearly as may be conform- 
 ing to the shape of the ground between. This last 
 operation will be facilitated and greater approach to 
 accuracy secured by sketch lines made in the field on 
 the plain side of the level-book. 
 
 If the section is being made from ordnance bench- 
 marks, the proceeding is exactly the same if from 
 contour maps, with this difference only, that every point 
 where the line crosses a contour is considered a station, 
 the distance scaled off and the height inserted accord- 
 ingly. 
 
 By Theodolite. The method of taking levels by the 
 theodolite differs from that by the level, in the former 
 having its visual line not in a horizontal plane, but 
 inclined at various- angles to the horizon according to 
 the slope of the ground between the stations. The 
 telescope, cross- wire, and spirit-level are the same, and 
 the instrument may be used as a level if desired. But 
 
HORIZONTAL SECTIONS. 75 
 
 the telescope is swung to move vertically, and the angle 
 at which its line of sight coincides with the object to 
 which it is directed is indicated on the graduated arc 
 attached to and which moves with the telescope the 
 amount of inclination being read off with the greatest 
 accuracy by means of a vernier scale. 
 
 Tor levelling by theodolite it is necessary that the 
 instrument be placed on the line of section (unless 
 correct heights at definite points only are required), and 
 that correct measurement be made of the distance be- 
 tween the instrument and the places at which observa- 
 tions are taken for it is evident that an inclined plane 
 gets to a greater or lesser height at every additional 
 portion of distance. 
 
 The instrument is placed on the line by compass- 
 bearing, not necessarily ascertained every time it is set 
 up, for it will frequently happen that an object at 
 considerable distance is seen to be in the correct line, 
 and by chaining straight towards such object the desired 
 end may be attained with much less trouble. When, 
 to get the proper line of direction, a bearing has to be 
 taken, the needle beneath the telescope is set free and 
 the instrument revolved on its horizontal plates until 
 the needle comes to rest at the proper angle allowance 
 of course being made for magnetic variation.* In this, 
 and all other manipulations of the theodolite, the process 
 is commenced by bringing it nearly into the required 
 position and then fixing it by the " clamping screws," 
 the operation being completed to the greatest nicety by 
 means of finely-cut " tangent screws " provided for the 
 purpose. The divisions of the arc, plates, and verniers 
 Ante, p. 9. 
 
76 FIELD GEOLOGY. 
 
 are so minute that a pocket-lens must be used in read- 
 ing off the indications. 
 
 The measurements are made along the surface, flat or 
 inclined as the case may be, with a chain 22 yards 
 (= ^- Q of a mile) in length, divided into 100 links. The 
 chain, made with strong wire, has a handle at each end 
 and a brass or other mark every ten links to aid in 
 counting the odd parts of each admeasurement. Ten 
 iron arrows, with pieces of red cloth on each, are carried 
 by the leading chain-man, who puts down one at the 
 end of every chain measured when the extent of ten 
 chains is reached the arrows, picked up in passing by 
 the chain-man at the rear-end, are restored to him, and 
 a note is made of every such ten chains passed over. 
 
 "We must secure the services of three men, or boys, 
 two being required for chaining, and the third for 
 assistance in the taking of our observations. The work 
 can be done with two only, but with a third it is gotten 
 over much more expeditiously of the three men, he 
 who is most to be relied on for care and accuracy, or is 
 accustomed to the work, should be put in the rear of 
 the chain. 
 
 As every spot where the instrument is placed will be 
 constituted a " station," the height from the ground of 
 the objects on which sights are taken should be about 
 the same as that of itself, viz. 5 feet the visual line 
 will then be carried from end to end at a uniform 
 distance of 5 feet from the surface. A light staff of 
 that height, with a cross-piece at top painted white, is a 
 good thing to be carried by the assistant and placed by 
 him on each place in turn where the observations are- 
 taken or without this staff the sight may be taken on 
 
HORIZONTAL SECTIONS. 77 
 
 the assistant himself, as on the top of his head or the 
 line of his eyes. 
 
 But the fore- and back-sights at an object must always 
 be taken on it when at the same level ; if this be done it 
 does not matter about its being a little too high or a 
 little too low relatively to the surface. For instance, it 
 may sometimes be convenient to place the man, with or 
 without the staff, on the top of a bank or on a gate 
 this will cause a local error of a few feet, but if both 
 fore- and back-sights be taken on it without alteration in 
 its position a constant error is avoided, which would 
 otherwise be carried on to the end of the section. 
 
 If the line of section, across the map (figs. 5 and 8), 
 were to be run by theodolite, the proceedings would be 
 somewhat as given below. Assuming that the start be 
 made from the milestone, which is also an ordnance 
 B. M. 365 feet, the first thing to be done is to find the 
 line (N. 35 W.) along which the section has to be run. 
 The instrument is set up and manipulated by the plate- 
 screws until the spirit-levels indicate that it is in a 
 horizontal position, then turned round, with the needle 
 free, until the latter comes to rest at 13 (35 W. 22 
 variation =13), the final adjustment having been made 
 by the tangent screws. The telescope being undamped 
 is free to move vertically (only), and as it now points 
 directly along the line of section, any objects in the 
 centre of its field are also in the line and may be pointed 
 out to the chain-man for his guidance. We may assume 
 that a tree in this instance comes in, and beyond that 
 the line passes just between two cottages seen at a long 
 distance. After seeing that the leading man has his ten 
 arrows, and that the chaining has been started in the 
 
78 FIELD GEOLOGY. 
 
 direction of the tree, we place our assistant at the mile- 
 stone with the staff on the B. M., and walk on to where 
 a rise in the ground begins. In doing so we may 
 observe whether the chain-man is directing his leader 
 properly along the line he should do this by looking 
 along the chain and by a wave of the hand to either 
 side, getting it ranged properly before the arrow is stuck 
 in the ground. Having set up the instrument and 
 booked the length, ten chains, in the level-book, we 
 send on the chain-men to measure to the next fence. 
 Adjustment for horizontality having been made, we 
 direct the -telescope back to the head of the staff on the 
 B, M., clamp it, and by turning the tangent-screw get 
 the cross-wire exactly to coincide therewith. We read 
 off the result as a depression of '50', and enter it in 
 its proper column, making a little cross also in the 
 column headed "Back-sight" to indicate that this is 
 such, take another look through the telescope and at the 
 reading to see that there is no mistake, and beckon the 
 assistant to come on. He is sent on immediately to 
 stand in the fence to which the chain-men have mea- 
 sured, in such a position that he can be seen both from 
 the instrument and from the ground beyond. Another 
 sight is now taken on the staff and entered, this time 
 as a " fore-sight " again checked by repetition, and we 
 walk on to find that the measurement from the instru- 
 ment to the fence was 4 chains 33 links. We go on 
 again with the chain- men, set up the instrument, take 
 a back-sight, and, in fact, repeat exactly the former 
 operations. As stations for the instrument and for the 
 staff, the spots on the line where changes occur in the 
 shape of the ground should be selected, the smaller 
 
HORIZONTAL SECTIONS. 
 
 features being sketched in as we proceed of this, the 
 copy of the level-book given below will afford an illus- 
 tration. 
 
 From Milestone 1ST. 35 W. passing by Church. 
 
 Station 
 No. 
 
 For- 
 ward. 
 
 Back. 
 
 Station 
 No. 
 
 Eleva- 
 tion. 
 
 De- 
 pres- 
 sion. 
 
 Dis- 
 tance. 
 
 Remarks. 
 
 1 
 
 
 
 
 
 
 O'OO 
 
 B. M. Milestone, 365'. 
 
 
 
 X 
 
 2 
 
 
 50 
 
 10 '00 
 
 
 3 
 
 X 
 
 
 
 1-5 
 
 
 4-33 
 
 
 
 
 
 
 
 
 
 ( Slight rise between. 
 
 
 
 X 
 
 4 
 
 
 6'20 
 
 6-33 
 
 j Boundary of Loam 
 
 
 
 
 
 
 
 
 ( about midway. 
 
 5 
 
 X 
 
 
 
 8'0 
 
 
 6*20 
 
 Road. 
 
 
 
 X 
 
 6 
 
 
 4'0 
 
 7'00 
 
 
 7 
 
 X 
 
 
 
 4-0 
 
 
 650 
 
 
 
 
 X 
 
 8 
 
 1-30 
 
 
 3-00 
 
 Rise between. 
 
 9 
 
 X 
 
 
 
 
 16-30 
 
 4-33 
 
 
 
 
 X 
 
 10 
 
 45 
 
 
 5'50 
 
 Hollow between. 
 
 11 
 
 X 
 
 
 
 
 5- 
 
 1-80 
 
 
 
 
 X 
 
 12 
 
 11-10 
 
 
 4'30 
 
 
 13 
 
 X 
 
 
 
 
 5'30 
 
 4-00 
 
 
 
 
 X 
 
 14 
 
 9-0 
 
 
 3-50 
 
 Boundary of Chalk. 
 
 15 
 
 X 
 
 
 
 
 9'35 
 
 5-50 
 
 Green-sand. 
 
 
 
 X 
 
 16 
 
 6'28 
 
 
 4-00 
 
 
 17 
 
 X 
 
 
 
 
 7'30 
 
 4-40 
 
 Well, 110' deep. 
 
 
 
 X 
 
 18 
 
 7-30 
 
 
 6'30 
 
 Stream. 
 
 19 
 
 X 
 
 
 
 16-30 
 
 
 7'80 
 
 ( Boundary of Green- 
 ) sand. 
 
 
 
 X 
 
 20 
 
 
 17-10 
 
 3-80 
 
 Boundary of Chalk. 
 
 21 
 
 X 
 
 
 
 11'5 
 
 
 4-00 
 
 . . . By Church. 
 
 
 
 X 
 
 22 
 
 5-30 
 
 
 7-00 
 
 Boundary of Chalk. 
 
 23 
 
 X 
 
 
 
 
 5-55 
 
 4-50 
 
 
 
 
 X 
 
 24 
 
 20-30 
 
 
 1'30 
 
 ( (Rise between) Boun- 
 ) dary of Green-sand. 
 
 25 
 
 X 
 
 
 
 
 8-10 
 
 8-00 
 
 
 
 
 X 
 
 26 
 
 5'5 
 
 
 7-70 
 
 Slight hollow between. 
 
 27 
 
 X 
 
 
 
 
 7-10 
 
 3-30 
 
 Stream. 
 
 It will sometimes occur that the face of a cliff or 
 quarry, of a sharp or rugged slope, is such that it cannot 
 possibly be measured with the chain. The height must 
 
80 FIELD GEOLOGY. 
 
 then be ascertained by means of two (or more) observations 
 with the theodolite ; one at some distance from the 
 base, and the other nearer thereto by a few chains the 
 length and the fall of the ground between the points 
 must of course be accurately determined. One of the 
 observations can be made from the last station, and the 
 other in advance of it, the sights being taken on the staff 
 or other object upon the summit. These with the length 
 and fall between the points being plotted as a diagram, 
 and with reference to a temporary datum line, will 
 give at the intersection of the angles the height and 
 position of the object relatively to such datum (see fig. 18). 
 
 Fig. 13. 
 
 Various expedients may with advantage be occasion- 
 ally adopted tinder exceptional circumstances, as for 
 instance, in coming to a field of standing corn, which 
 would be injured by the chain-men measuring through 
 it, or a tract of marsh land flooded so as to be impassable. 
 In the former case the exact level of an accessible object 
 on or near the line may be transferred across the field, 
 by clamping the instrument at zero, and noting where 
 the cross-wire cuts some object on the other side ; the 
 distance must be judged, or it may perhaps be scaled 
 
HORIZONTAL SECTIONS. 81 
 
 from the map. In the other supposed case, the staff or 
 man should be placed at a station by the edge of the 
 water on the near side of the marsh, and in a similar 
 position when starting again from the other side ; the 
 space between the two points will of course be level and 
 the distance must be obtained as before. 
 
 Sometimes also a great deal of useless labour may be 
 saved by going somewhat off the line, as round a wood 
 or a village, care being taken to note the horizontal 
 angles at which the line is left and rejoined, also those 
 and the distances between all the intermediate stations. 
 These being afterwards laid clown shew the line actually 
 levelled, and the distance between the points of de- 
 parture and return can be scaled off the ascertained 
 difference in height will require no alteration. 
 
 Plotting from Angles. The method of plotting the- 
 odolite observations varies somewhat from that de- 
 scribed, and must be performed with great care for the 
 result to be satisfactory. A straight line is drawn on 
 the long strip of paper to represent the "datum line," 
 sea-level or otherwise, and another line vertical thereto, 
 near the left-hand end of the paper, which should be also 
 the most southernly end of the section. On the vertical 
 line, which corresponds to station 1, set off the height 
 above datum of the B. M., in the case supposed, 365 feet. 
 Then with a protractor of circular or semi-circular shape, 
 and made in horn or other transparent material, lay 
 down a line inclined to the datum line as many degrees 
 and minutes as are recorded in the first observation. 
 This being a " back-sight " and " depression " means of 
 course " elevation " in a forward direction, the line must 
 therefore rise from the bench-mark. The angle is best 
 
 6 
 
82 FIELD GEOLOGY. 
 
 laid down, or at all events pricked off, by the datum line, 
 from the point where crossed by the vertical line (on 
 which point the centre of the protractor would be placed), 
 and then transferred to its proper position as starting 
 from the bench-mark. The measured distance is then 
 scaled off along the inclined line, and another vertical 
 line in pencil drawn through the measured point and 
 through the datum line. This point is the second 
 station, and a figure 2 is made below it for the conveni- 
 ence of future reference. Another line is now laid down 
 in a similar manner for the " fore-sight ;" this being an 
 " elevation " forwards rises in the same direction as the 
 one already plotted, is laid down, measured off, and 
 numbered. The succeeding observation is a " back- 
 sight " and " elevation," therefore " depression " forwards, 
 and will be laid down with a different inclination from 
 those previously drawn. 
 
 These lines of course do not accurately represent the 
 curved parts of the surface, but give correct heights at 
 the points selected for stations ; the line, when inked in 
 between, must sweep naturally through these points, and 
 the sketch lines in the level-book supply the shape of 
 the intervening ground. Wherever a station is on a 
 road, or by a stream, a pit, and so on, the fact must be 
 recorded on the section ; and wherever the line crosses or 
 passes by such points between the stations, note must 
 be made of the intermediate measurement to them that 
 their position may be correctly indicated. The section, 
 fig. 19, has some working lines dotted at the left hand ; 
 these represent the stations, and in practice would be 
 drawn in pencil, to be erased when the surface line with 
 the roads, &c., had been drawn in Indian ink. 
 
HORIZONTAL SECTIONS. 
 
 83. 
 
 g 30 
 
 4 
 
 62 
 
84 FIELD GEOLOGY. 
 
 Filling in Geology. The geological details are filled 
 in by aid of the boundary lines on the map, of the par- 
 ticulars observed in exposed sections and ascertained 
 from wells or borings, and to a great extent by inference 
 from such evidence. The lines of boundary and outcrop 
 are scaled off from the map, or their position noted in 
 the measurements along the line of section levelled, the 
 beds drawn with the proper inclination, true or apparent 
 dip as the case may be, and with all known faults, flex- 
 ures, and contortions dotted lines only being used 
 where the details are uncertain. In this operation the 
 table given at page 50 will be found of service, but care 
 must be taken to allow for unevenness of the 
 ground, by drawing a horizontal line to work from 
 through the point at which the calculations are to be 
 applied. 
 
 Apparent Dip. Frequently the line of section will 
 run not in the direction of the dip, in such cases the in- 
 clination of the beds must be shewn as it would appear 
 in a section cut through them along that line. The 
 difference can be found by calculation, but is more 
 readily ascertained by diagram, or on reference to a table 
 constructed by the late Mr. J. B. Jukes, and published 
 by him in the Appendix to the " Geology of the South 
 Staffordshire Coal-field." Mems. Geol. Survey. It is 
 given also in an abridged form in his " Manual of 
 Geology," with the addition of some valuable hints on the 
 construction of geological sections. 
 
 In the article previously quoted (p. 49) Mr. Dalton 
 gives a method of finding the apparent inclination in a 
 direction oblique to that of the true dip. 
 
 "Problem. To find the apparent angle in any re- 
 
HORIZONTAL SECTIONS. 
 
 85 
 
 quired section, from the Ml dip and deviation of its 
 direction from that of the section (fig. 20). 
 
 Fig. 20. 
 
 " Construct the right-angled triangle ABC, with ABC 
 equal to the full dip ; also the right-angled triangle BCD 
 with BCD equal to the deviation ; lastly the right- 
 angled triangle c D E, in which c E is equal to A c. 
 
 " Then c D E is the required apparent angle. 
 
 " Proof. If A B c be- a vertical plane along the full 
 dip, and c D E the vertical plane of section, BCD will be 
 a horizontal plane, and A c, c E will coincide, so that B D, 
 A E will be the plane of stratification, giving the ap- 
 parent angle c D E along the section." 
 
 In the section, fig. 19, illustrating the geological 
 structure of the area surveyed, the boundary lines of the 
 chalk and upper green-sand would be scaled from the 
 map, or their position ascertained while chaining as the 
 
86 FIELD GEOLOGY. 
 
 heights were taken by aneroid, level, or theodolite. The 
 N". and S. boundaries of ea;ch, so far as the outlier is 
 concerned, would be united by straight lines, or the act- 
 ual lines of division would perhaps be more accurately 
 represented by being slightly depressed in the centre. 
 Dotted lines across the valley between the outlier and 
 the main mass, passing through the points of boundary, 
 will give the inclination at which they commence to dip 
 beneath the surface ; farther S. the chalk is shewn dip- 
 ping at an angle of 2 30'; the true dip is 3 but the sec- 
 tion line is oblique thereto, the deviation being 28, and 
 the apparent dip of 2 30' is found either by table or dia- 
 gram. The thickness of the Gault at the well being 
 known, 108 feet, the base of the deposit can be shewn 
 there and prolonged by dotted lines, as provisional only 
 until the section shall have been extended northwards 
 to the boundary of the formation. 
 
LI BRAKY 
 
 UNIVERSITY OF 
 
 CALIFORNIA. 
 V= 
 
 PART III. 
 
 LITHOLOGT. 
 
 CHAPTER I 
 
 DETERMINATION OF ROCKS. 
 
 Texture Structure Fracture Lustre Hardness and Efferves- 
 cence Specific Gravity Eeactions in the Wet Way Blow- 
 pipe. 
 
 General Remarks. The kinds of rock of which the crust 
 of the earth is composed are as various almost as the 
 rocks themselves. Eocks coming under the same de- 
 nomination, such as clay, sand, and so on, have been 
 formed during all geological periods, but vary more or 
 less in their minor characteristics. This is owing mainly, 
 .as regards sedimentary deposits, to differences in the 
 kind of the rocks (and the relative quantities of each 
 kind) from which they have been derived that is, in 
 any area, and at any time subject to denudation. The 
 resulting deposits differ accordingly, perhaps not so much 
 .that it shall always be possible to -examine a specimen 
 and say at once, " This belongs to such and such a for- 
 mation," but it can be done in very many instances; and 
 when it cannot, Palaeontology must furnish the additional 
 .evidence. The eruptive and intrusive rocks vary also 
 
FIELD GEOLOGY. 
 
 according to their age, although not to so great an extent, 
 and from causes that are not so well understood. 
 
 But in consequence of the changes which rocks have 
 undergone subsequent to their formation, it is not at all 
 times easy to decide off-hand even to what class a speci- 
 men belongs it must then be subjected to certain tests 
 for its determination. There are simple tests for appli- 
 cation in the field to ascertain the class of rock that is 
 under examination ; and more delicate tests, involving 
 the use of apparatus at home, by which the field results 
 may be checked and extended. In many cases the sim- 
 ple directions given below will not go far enough to- 
 wards accurate solution, but it will then be found advis- 
 able to consult such works as are devoted to the subject, 
 or to obtain the assistance of a professed mineralogist 
 for the ultimate determination of a difficult specimen. 
 
 In the many valuable works on Petrology and Miner- 
 alogy that have been published, the usual plan adopted, 
 and in such works the only one possible, has been to 
 name a rock or a mineral, and then to describe the re- 
 sults obtained by subjecting it to certain processes. But 
 to the geologist, who goes into the field and encounters an 
 unknown rock, this method of its determination involves 
 a vast amount of labour and perseverance. The object 
 aimed at in the compilation of the following Tables is 
 to save much of this labour by reversing the process,, 
 tabulating the results obtainable, and deriving therefrom 
 the kind of the rock subjected to experiment. This 
 must necessarily be done within confined limits ; but a 
 fair approximation to the desired result may be thereby 
 obtained, with indications for more detailed operation. 
 It should be unnecessary to insist upon what all text- 
 
LITHOLOGY. 89 s 
 
 books recommend, that an acquaintance with the appear- 
 ance and characteristics of all ordinary rocks and 
 minerals should be formed by careful study of cabinet 
 specimens. 
 
 All the stratified rocks, except those organically and 
 chemically formed, were deposited as clay, pure or im- 
 pure as sand or gravel, which differ from each other 
 only in the size of their particles or as an admixture 
 of the two, sometimes with the addition of lime or other 
 secondary ingredient. 
 
 Clay is simply mud derived from the waste of pre- 
 existing rocks. Generally, it consists of finely-com- 
 minuted silica, with about one-fourth of alumina, 
 and as a rule may be considered a deep-sea deposit. 
 When indurated by pressure more or less verti- 
 cal to the lines of bedding, it becomes divisible into 
 laminae, and is termed Shale. 
 
 When indurated by pressure in any other direc- 
 tion, it is cleaved, or becomes divisible into laminae 
 at right angles to the pressure, and is termed Slate. 
 (See note below.) 
 
 In whatever form clay occurs, whether unaltered, 
 as shale, or as clay-slate, it gives off when breathed 
 on an earthy or slaty odour which is unmistakable. 
 Sand, also derived from the waste of existing 
 rocks, consists mainly of silica, with a slight admix- 
 ture of other minerals. When finely-bedded, it has 
 been deposited in tranquil water ;* when the lines of 
 stratification intersect each other at various angles, 
 it is false-bedded, and has been formed in a current, 
 
 * Except in the case of " blown sand " see Jukes' " Manual,'* 
 p. 378. 
 
FIELD GEOLOGY. 
 
 fluviatile or marine. When exhibiting "ripple- 
 marks,"*' it indicates a shore-line ; when bound to- 
 gether by a cementing material, it becomes Sand- 
 stone, or, if coarse-grained, Grit. 
 
 Gravel consists of pebbles derived from neigh- 
 bouring rocks, angular or rounded according to the 
 degree of trituration to which they have been sub- 
 jected. It is formed by rivers, or by marine cur- 
 rents at no great distance from the shore. 
 
 When bound together by a cementing material, 
 it becomes, if the pebbles be more or less rounded, 
 a Conglomerate, or Pudding-stone; if the frag- 
 ments be perfectly angular, a Breccia in either 
 case representing a shore-line. 
 
 Clay and sand mixed, in varying proportions, 
 form Loam, or Brick-earth. 
 
 Clay, with the addition of Lime, one-tenth or 
 more of its substance, becomes Marl, and in a dry 
 .state breaks up into cubical fragments. 
 
 Marl, when indurated, becomes divisible into 
 laminae, and is termed Marl-slate. 
 
 Note. " Bands of colour may sometimes be ob- 
 served on the sides of Slates, often coinciding with 
 slight changes of grain or texture ; these mark its 
 original stratification. But care must be taken in 
 field observations not to rely too implicitly on mere 
 bands of colour in slate rocks, unless they coincide 
 with bands of various texture, which may always be 
 trusted to show the original layers of deposition/'f 
 To ascertain the kind of any rock exposed in a quarry 
 
 * Lyell's " Students' Elements/' p. 21. 
 
 f Jukes' " Manual of Geology," p. 220. See also an excellent cut 
 
LITHOLOGY. 91 
 
 or elsewhere, a fragment should "be detached from a part 
 that has been least subjected to the action of the 
 weather ; for the composition of a " weathered " surface 
 may have been very materially modified. Some rocks 
 will be thus changed into a substance totally different 
 from their original state, and all are in colour and hard- 
 ness more or less thereby affected. 
 
 Having selected a suitable portion of the rock, let a 
 good-sized piece be broken off by chisel or hammer ; this 
 can afterwards be reduced its most characteristic-look- 
 ing part being chosen into a fair hand specimen. In 
 using the hammer for "stone-breaking," it should be 
 borne in mind that the fracture will follow, as nearly as is 
 possible, the line of the blow, the force of the descending 
 implement (itself stopped by contact) passing on in the 
 same direction, unless turned aside by the mass being 
 too rigid to be broken through. A fissile rock may thus 
 be split up into slabs by blows on the edge ; a piece 
 broken off at right angles to the bedding by a direct 
 blow on the surface ; and a projecting corner may be 
 chipped off a very hard and solid rock by well-directed 
 blows, when otherwise fragments are unobtainable. It 
 is also worthy of remembrance that one good swinging 
 blow is worth a dozen minor taps, and the risk is no 
 greater of a resulting fracture to the hammer-handle. 
 
 The rock to be determined should be broken, with as 
 little chipping as may be, into a square fragment, not a 
 rounded lump, the larger surfaces representing the lines 
 of bedding, with the others at right angles or there- 
 at p. 221, representing the planes of cleavage and original stratifi- 
 cation. 
 
92 FIELD GEOLOGY. 
 
 abouts. The best observable edge is thus obtained ; 
 and if the specimen is to be preserved, it may with ad- 
 vantage shew one weathered side, and should not be too 
 large for portability. 
 
 Texture. The rock or mineral is first examined for 
 " texture ;" this may be very apparent, but if not readily 
 decided, it must be observed with a pocket lens of one, 
 two, or three powers as may be found requisite. This 
 point should if possible be settled ; but when doubtful 
 under the lens, look for lines of varying colour as signs 
 of stratification. The texture may be either 
 
 CRYSTALLINE in which the crystals are uniform 
 
 and apparent, as in Quartz 
 Confusedly-crystalline as in Granite 
 Sub-crystalline as in some Limestones 
 GLASSY resembling Glass as in Obsidian. 
 COMPACT or homogeneous as in Flint 
 GRANULAR made up of distinct and somewhat 
 
 rounded grains as in Sandstone 
 LAMELLAR \ consisting of thin plates or layers, the 
 LAMINATED > laminae being in the lines of bedding 
 FOLIATED ) as in Mica, Schist, &c. 
 CLEAVED consisting of thin plates or layers, the 
 laminae being transverse to the lines of bedding 
 as in Clay-slate 
 
 FIBROUS resembling fibres as in Fibrous Gypsum 
 EARTHY soft and friable as in Shale 
 PORPHYRITIC enclosing larger embedded crystals. 
 
 as in some of the Cornish Granites. 
 VESICULAR full of little cells or versicles as 
 
 in Pumice. 
 Structure. The " structure " also of rocks must be 
 
LITHOLOGY. 93 
 
 noticed, some being distinctly Bedded, others Massive 
 or in large masses broken in varying directions. Some 
 are Jointed, divided by joints into blocks, or Columnar, 
 when the blocks resemble columns ; others are Amor- 
 phous, where no bedding or other structure is presented. 
 Some rocks are termed Slaggy, these are like furnace- 
 slag, others Scoriaceous, which are cinder-like in appear- 
 ance. 
 
 Fracture. The character of the broken surface or 
 " fracture" affords useful indication of the kind of the 
 rock or mineral under examination, when taken in con- 
 nection with other peculiarities. The usual forms of 
 fracture are : 
 
 Conchoidal Shell-like, as that of Flint 
 Even Flat Felstone 
 
 Uneven = Eough Serpentine 
 
 Splintery = Jagged Graphite 1 
 
 Earthy = Irregular Chalk 
 
 Lustre. After the texture of a specimen has been 
 determined, and its fracture noted, the " lustre " of its 
 freshly-broken surface requires observation. This char- 
 acter distinguishes a rock, whether it possess a crystalline 
 'or any other texture ; for instance, it does not at all follow 
 that because a rock is crystalline, its lustre must be 
 vitreous, or that it should not be such when the texture 
 is compact or granular. There are many kinds and de- 
 grees of each kind of lustre, the most usual being : 
 Vitreous, like glass 
 Sub-vitreous 
 Kesinous, like resin 
 Pearly, like that of a pearl 
 Silky, like silk 
 
94 FIELD GEOLOGY. 
 
 Metallic, like the ordinary lustre of metals 
 
 Sub-metallic 
 
 Adamantine, like that of a diamond. 
 Hardness and Effervescence. The tests by which, 
 in the field, the nearest approach can be made to the de- 
 sired result are its "hardness" and "effervescence." 
 The former is roughly determined by means of the steel 
 blade of a pocket-knife, the latter by application of 
 dilute nitric, sulphuric, or hydro-chloric acid (usually 
 about one part acid to five water). A rock or mineral 
 soft as Talc or Bock-salt may be scratched by the finger- 
 nail ; between those and Apatite, by the knife with ease ; 
 be} r ond that, and including Orthoclase Felspar, with 
 some degree of force ; while those of greater hardness 
 are not marked at all by the steel. A drop of dilute 
 acid applied to the fresh fracture will cause effervescence 
 rapid, if the specimen consist of pure carbonate (of lime 
 or otherwise) ; slow, if only partly composed of carbonate , 
 and none whatever if it be a sulphate or a silicate. The 
 following table is easily remembered, and applies in 
 nearly all ordinary cases. The exceptions are not nu- 
 merous, and they present well-marked characteristics of 
 their own ; in such cases further tests if necessary must 
 be applied at home. In practice, so many slight varia- 
 tions are found, that they are incapable of simple classi- 
 fication ; but then judgment must guide the observer, 
 and an acquaintance with cabinet specimens will be 
 found of great service, surpassed only by actual field ex- 
 perience. 
 
 If a rock or mineral : 
 
 Scratch with ease and effervesce freely, it consists of 
 
 Calcite or Limestone. 
 
LITHOLOGY. 95 
 
 Scratch with ease and effervesce slowly, it consists of 
 Magnesite or Dolomite. 
 
 Scratch with ease and effervesce not at all, it consists 
 of Sulphates or Silicates. 
 
 Scratch with difficulty and effervesce not at all f it 
 consists of Silicates. 
 
 Scratch not at all and effervesce not at all, it is a 
 pure Silicate when crystalline, and Siliceous when 
 compact. 
 
 Scratch not at all and effervesce slowly, it is calca- 
 reous Sandstone when granular. 
 
 Actual determination at home of the hardness of a 
 mineral is made by comparison of the specimen with 
 others of which it is known, the scale arranged by Moll 
 being the one generally adopted. 
 
 HARDNESS. 
 
 ( 1. Talc. 
 Scratched by the nail. rt _. , ,. 
 
 I 2. Eock-Salt. 
 
 , ( 3. Gale-Spar. 
 
 Scratched by the knife with 1 A ^ 
 
 J < 4. Fluor-Spar. 
 
 ease. i K . ... 
 
 V. 5. Apatite. 
 
 Scratched by the knife with ) , 
 
 difficulty. | 6 ' Felspar ( rthoclase )- 
 
 / 7. Quartz. 
 Cannot be scratched byj 8. Topaz. 
 
 knife or file. "1 9. Sapphire. d^^^Ju^ 
 
 \ 10. Diamond. 
 
 The test is made by " rubbing the specimen over a 
 tolerably fine-cut file, and noting the amount of powder, 
 and the degree of noise produced by so doing. The less 
 the powder and the greater the noise the harder will 
 be the mineral. On the other hand, a soft mineral will 
 
96 FIELD GEOLOGY. 
 
 yield much powder, and but little noise. The noise 
 and amount of powder should be compared with that 
 produced by minerals which are used as standard 
 examples. The trial may also be made by endeavour- 
 ing to scratch the specimens enumerated in the list 
 with the mineral under examination. If, for example, 
 the mineral will scratch Felspar and will not scratch 
 Quartz, it will have a hardness between 6 and 7. 
 
 " During these trials the ' colour ' and ' lustre ' of the 
 streak should also be noticed."* " "When a mineral is 
 scratched, the colour of the scratched surface frequently 
 differs from that of the original surface, and if the 
 abraded powder be rubbed on paper, it leaves a mark 
 of # peculiar colour. This is called the streak, and in 
 some of the metallic minerals it is very characteristic."^ 
 Note. In all the Tables here given only an ap- 
 proximation is intended, the averages of hardness 
 and specific gravity inserted and the more simple 
 of the tests for solubility and blow-pipe analysis. 
 For more accurate and for ultimate determination 
 of any particular specimen recourse should be had 
 to some of the works specially devoted to the 
 , subject or to the professed mineralogist. A list is 
 given at page 11*7 of some of the works which may 
 with advantage be consulted. 
 
 Specific Gravity. The " specific gravity " of a body 
 being the proportion that its weight bears to that of 
 an equal bulk of distilled water (the latter being taken 
 as unity), it is evident that if such body be weighed, 
 first in air, then in distilled water, the resulting loss 
 
 * " Mineralogy." Kutley. Murby's Series, 1874, p. 39. 
 t " Mineralogical Tables." Jewesbury. Murby's Series, 1873, 
 p. 9. 
 
LITHOLOGY. 
 
 97 
 
 of weight represents that of an equal volume of the 
 water, displaced by immersion. Therefore the weight 
 of the substance in air is to the loss of weight (i.e. 
 the weight of the water) as the specific gravity is to 
 unity consequently the weight in air, divided by the 
 loss, will give the required specific gravity. 
 
 A delicate balance on a stand with minute weights 
 is required for the operation, one pan having a small 
 hook beneath from which the specimen to be tested' 
 is suspended by a fine platinum wire a few grains 
 of sand, added after the thread is attached, will 
 bring the scales into equilibrium. The actual weight 
 of the suspended object is first to be ascertained, then 
 there is placed beneath it a small vessel containing the 
 water in such position that it shall be completely im- 
 mersed during the second weighing operation. 
 
 Reactions in the Wet Way. As a very useful addi- 
 tion to the particulars given under the head of " solu- 
 bility " in the table of tests, the foUowing list of " Ee- 
 actions in the wet way " has been copied from Paitley's 
 " Mineralogy," p. 22. 
 
 Substances. 
 Carbonates. 
 
 Sulphates. 
 
 Reaction. 
 
 Effervesce when treated with dilute 
 acids (either hydrochloric, nitric, or 
 sulphuric), owing to disengagement 
 of carbonic acid gas. 
 
 Do not effervesce on the application of 
 acids, but when in solution, a drop 
 of chloride of barium will produce a 
 dense white precipitate of sulphate 
 of baryta. 
 
 7 
 
98 
 
 FIELD GEOLOGY. 
 
 Substances. Reaction. 
 
 Nitrates. Give off fumes of nitric acid when con- 
 
 centrated sulphuric acid is added. 
 
 Phosphates. j In solution give yellow precipitates on 
 the addition of nitrate of silver or 
 molybdate of ammonium. These 
 reactions usually take some time. 
 
 Chlorides. Give a white curdy precipitate when 
 
 nitrate of silver is added to their so- 
 lutions. 
 
 Fluorides. When treated with strong sulphuric 
 
 acid, give off fumes of hydro-fluoric 
 acid, which roughen or etch glass. 
 
 Silicates. Many silicates gelatinise when heated 
 
 in concentrated acids. The silicate 
 should be finely pulverised. 
 
 Bloiv-pipe. "The student ought to accustom him- 
 self to the use of the blow-pipe, as an instrument to aid 
 him in the determination of rocks much assistance 
 may be obtained in this way. No field geologist should 
 consider his outfit complete if it does -not include a 
 blow-pipe, with the requisite reagents."*" For the 
 simple experiments, the results of which are given in 
 the last column of the table, much apparatus is not re- 
 quired. " A blow-pipe of brass or German silver with 
 platinum point, an oil-lamp with a broad rectangular 
 wick, a piece of platinum wire, and a flat lump of wood- 
 charcoal about six inches long for a support. 
 
 "The blow-pipe flame is produced by forcing a small 
 continuous stream of air through the flame of the lamp 
 * " Student's Manual of Geology." Jukes and Geikie. 1872. 
 
L1THOLOGY. 99 
 
 in a more or less inclined direction. The stream of air 
 must be constant and regular, also properly directed 
 and applied. It is in the power of the operator to 
 direct either an oxydising or a reducing flame upon 
 the body he subjects to its action. 
 
 " In order to obtain a reducing flame (for depriving a 
 substance of its oxygen) the nozzle of the blow-pipe is 
 held in an inclined direction parallel to the surface of 
 the wick and just touching the exterior surface of the 
 flame, a bright yellow flame will be thus produced. An 
 oxydising flame (for bringing about the oxydation of a 
 substance) is obtained by keeping the nozzle at the 
 same inclination, introducing it into the flame to about 
 one-third the breadth of the wick, and blowing a some- 
 what stronger blast the flame so produced is of a pale 
 blue colour and almost invisible by daylight. 
 
 " If a small fragment of an oxydisable substance be 
 held just beyond the point of the oxydising flame it 
 becomes intensely heated, and, being exposed freely to 
 the action of the surrounding atmosphere, it is rapidly 
 oxydised. This flame, on account of its great heating 
 power, is also employed in order to ascertain the fusi- 
 bility of various substances, and for effecting fusions in 
 all cases in which a reducing action is not essential. 
 
 " When any substance is submitted to the action of 
 the reducing flame it should be so held as to be entirely 
 surrounded by the yellow flame, and protected from the 
 oxydising action of the air; but this condition being 
 fulfilled, it should be held as near as possible to the 
 point of the flame in order to gain the greatest amount 
 of heat."* 
 
 * " Scheerer and Blandford on the Blow-pipe." 1864. 
 
 72 
 
100 
 
 FIELD GEOLOGY. 
 
 CHAPTEE II. 
 
 DETERMINATION OF EOCKS AND MINERALS Continued. 
 
 Table of Tests, in the Field at Home Metals Tests Micro- 
 scope Chemical Analysis List of Books of Reference Pe- 
 culiarities of Structure, Concretions, Slickensides Note on 
 Metamorphic Rocks Cabinet Specimens. 
 
 TABLE OF TESTS, for application in the field. 
 
 Texture. 
 
 Fracture. 
 
 Lustre. 
 
 cratch- 
 ecl by 
 knife. 
 
 Effer- 
 
 ves - Colour, 
 cence. 
 
 Streak. 
 
 Crystalline 
 
 Conchoi- 
 
 Vitreous 
 
 With 
 
 Rapid 
 
 White 
 
 White 
 
 
 dal 
 
 
 ease 
 
 
 or 
 
 or 
 
 occurs also 
 
 
 
 
 
 tinted 
 
 greyish 
 
 Compact 
 
 
 jj 
 
 v 
 
 J> 
 
 55 
 
 55 
 
 Earthy 
 
 
 Earthy 
 
 55 
 
 55 
 
 55 
 
 55 
 
 Granular 
 
 Flat 
 
 Dull 
 
 55 
 
 55 
 
 55 
 
 55 
 
 Fibrous 
 
 Splin- 
 
 Silky 
 
 55 
 
 55 
 
 55 
 
 55 
 
 
 tery 
 
 
 
 
 
 
 Vesicular 
 
 
 
 55 
 
 55 
 
 55 
 
 55 
 
 Crystalline 
 
 ?lat con- 
 
 Vitreous 
 
 55 
 
 Slow i White 
 
 White 
 
 
 choidal 
 
 
 
 
 or 
 
 occurs also 
 
 
 
 
 
 greyish 
 
 
 Comp. and 
 
 
 Dull 
 
 
 
 
 
 Gran. 
 
 
 
 
 
 
 
 Crystalline 
 
 Conchoi- 
 
 Vit. inclin 
 
 55 
 
 55 
 
 White 
 
 White 
 
 
 dal or 
 
 ing to 
 
 
 i or or grey 
 
 
 uneven 
 
 Pearly 
 
 
 
 tinted 
 
 
 occurs also 
 
 
 
 
 
 
 
 Comp. anc 
 
 
 Dull 
 
 5) 
 
 55 55 
 
 55 
 
 Gran. 
 
 
 
 
 
 
 
 
 
 
 
 i 
 
 
 Compact 
 
 
 Glistening 
 
 55 
 
 None 
 
 White 
 
 White 
 
 
 
 
 
 
 or 
 
 
 occurs als 
 
 
 
 
 
 slightly 
 tinted 
 
 
 Granular 
 
 
 Dull 
 
 55 
 
 55 
 
 55 
 
 55 
 
 Crystallin 
 
 
 Sub- vitre- 
 
 55 
 
 55 
 
 | 
 55 | 55 
 
 
 
 ous 
 
 
 
 
 ?> 
 
 
 Silky 
 
 55 
 
 5 
 
 55 55 
 
LITHOLOGY. 
 
 101 
 
 TESTS, for further determination at home. 
 
 The Substance probably is 
 
 Hard- 
 ness. 
 
 Specific 
 Gravity. 
 
 Solubility. 
 
 Behaviour before tho 
 Blow-pipe. 
 
 CALCITE (Carbonate 
 of Lime) 
 Varieties : 
 Limestone (Marble) 
 Chalk 
 Oolitic Limestone 
 Satin Spar 
 
 3 
 
 2'6 
 
 Soluble in 
 acid 
 
 Infusible,becomes 
 luminous, and 
 is reduced to 
 quicklime 
 
 Gale-Tuff 
 
 
 (light) 
 
 
 
 MAGNESITE (Carbo- 
 nate of Magnesia) 
 
 4 
 
 3- 
 
 Soluble 
 slowly in 
 cold, ra- 
 pidly in 
 warm acid 
 
 Infusible,crackles 
 and hardens 
 
 DOLOMITE (Carbo- 
 nate of Lime and 
 Magnesia) 
 Variety : 
 Magnesian Lime- 
 stone 
 
 4 
 
 2'8 
 
 Soluble in 
 warm acid 
 
 Infusible 
 
 GYPSUM (Sulphate 
 of Lime) 
 
 Varieties : 
 Gypsum 
 Selenite 
 
 2 
 
 2'3 
 
 Insoluble 
 
 Exfoliates and 
 crumbles, be- 
 coming white 
 and opaque 
 
 Satin Spar 
 
 
 
 
 
102 
 
 FIELD GEOLOGY. 
 
 TABLE OF TESTS, for application in the field continued. 
 
 Texture. 
 
 Fracture. 
 
 Lustre. 
 
 Scratch- 
 ed by 
 knife. 
 
 Effer- 
 ves- 
 cence. 
 
 Colour. 
 
 Streak. 
 
 Compact 
 
 Flat con- 
 
 Resinous 
 
 With 
 
 
 White 
 
 
 
 choidal 
 
 
 ease 
 
 
 and 
 
 
 
 
 
 
 
 amber 
 
 
 Earthy 
 
 
 
 ?> 
 
 
 Green- 
 
 Shining 
 
 
 
 
 
 
 ish 
 
 
 
 
 
 
 
 brown 
 
 
 Crystalline 
 
 Conchoi- 
 
 Vitreous or 
 
 With 
 
 None 
 
 Vari- 
 
 White 
 
 
 dal or 
 
 sub -resi- 
 
 diffi- 
 
 
 ous. 
 
 
 occurs also 
 
 uneven 
 
 nous 
 
 culty 
 
 
 
 
 Comp. 
 
 
 
 5J 
 
 ? 
 
 (Brown) 
 
 
 Concre- 
 
 
 
 ?) 
 
 5) 
 
 ( ,, ) 
 
 
 tionary 
 
 
 
 
 
 
 
 Crystalline 
 
 5? 
 
 Vitreous 
 
 With 
 
 None 
 
 White, 
 
 White 
 
 Comp.or 
 
 
 
 ease 
 
 
 some- 
 
 
 Gran. 
 
 
 
 
 
 times 
 
 
 
 
 
 
 
 tinted 
 
 
 
 
 
 
 
 purple, 
 
 
 
 
 
 
 
 &c. 
 
 
 Crystalline 
 
 Conchoi- 
 
 5) 
 
 JJ 
 
 None 
 
 White, 
 
 White 
 
 
 dal 
 
 
 
 
 tinted 
 
 
 )> 
 
 
 Vitreous, 
 
 5J 
 
 jj 
 
 White 
 
 
 
 
 inclining 
 
 
 
 or 
 
 
 
 
 to resi- 
 
 
 
 tinted 
 
 
 
 
 nous 
 
 
 
 
 
 Crystalline 
 
 Splin- 
 
 Metallic 
 
 5* 
 
 )) 
 
 Black 
 
 Black 
 
 Comp. or 
 Foliated 
 
 tery 
 
 
 
 
 
 and 
 shining 
 
 
 
 
 
 
 
 (charac- 
 
 
 
 
 
 
 
 teristic) 
 
 
 
 / 
 
 Not at 
 
 
 
 
 Crystalline 
 
 
 ( 
 
 all or 
 
 ) 
 
 
 
 Compact 
 
 
 
 with 
 
 
 
 
 
 
 
 
 diffi- 
 
 
 
 
 
 
 
 culty 
 
 / 
 
 
 
LITHOLOGY. 
 
 103 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard 
 ness. 
 
 Specific 
 Gravity 
 
 Solubility. 
 
 Behaviour before the 
 Blow-pipe. 
 
 FULLER'S j - u 
 EARTH / mma 
 
 3 
 2 
 
 
 Gelatinizes 
 in hydro- 
 chloric 
 acid 
 
 Loses colour and 
 becomes pulve- 
 rulent 
 Fuses to porous 
 slag 
 
 APATITE (Phosphate 
 of Lime) 
 Varieties : 
 Phosphorite 
 Coprolite 
 
 5 
 
 3' 
 
 Soluble in 
 nitric acid 
 
 Infusible 
 
 FLUOR SPAR (Fluo- 
 ride of Calcium 
 
 4 
 
 3' 
 
 
 Decrepitates and 
 fuses to a clear 
 bead, which be- 
 comes opaque 
 
 KOCK SALT (Chlo- 
 ride of Sodium) 
 
 2 
 
 2 '2 
 
 Soluble in 
 water 
 
 Decrepitates, and 
 tinges the flame 
 yellow 
 
 BARYTES (Sulphate 
 of Baryta) 
 
 GRAPHITE (Carbon) 
 
 3 
 
 2 
 
 4'5 
 
 2 
 
 Insoluble 
 Insoluble 
 
 Decrepitates and 
 fuses with diffi- 
 culty ; colours 
 the flame yel- 
 lowish-green 
 [nfusible alone 
 
 
 
 
 I 
 
 LI BRA if ; 
 
 SILI- ^ f some 
 
 
 
 Insoluble^ 
 
 VI VEKSiTY , 
 
 \_termined 
 
 
 
 I < 
 
 'ALIFoKXJU 
 
104 
 
 FIELD GEOLOGY. 
 
 TABLE or TESTS, for application in the field continued. 
 
 Texture. 
 
 Fracture. 
 
 ' Lustre. 
 
 Scratch- 
 ed by 
 knife. 
 
 Effer- 
 ves- 
 cence 
 
 Colour. 
 
 Streak. 
 
 Crystalline 
 (sometimes 
 
 Conch.to 
 uneven 
 
 Vitreous,to 
 Pearly 
 
 With 
 
 diffi- 
 
 None 
 
 White, 
 pink 
 
 Grey- 
 ish- 
 
 Compact) 
 
 and 
 
 
 culty 
 
 
 
 white 
 
 
 splintery 
 
 
 
 
 
 
 
 
 Dull 
 
 
 
 
 
 
 
 
 
 
 Colour- 
 
 
 
 
 
 
 
 less 
 
 
 
 
 Vitreous 
 
 
 
 
 
 Compact 
 
 Even 
 
 55 
 
 
 
 
 
 Compact 
 
 Conchoi- 
 
 Kesinous 
 
 M 
 
 7J 
 
 White, 
 
 Colour- 
 
 (sometimes 
 
 dal, un- 
 
 
 
 
 tinted 
 
 less 
 
 Crystal- 
 
 even 
 
 
 
 
 
 
 line) 
 
 
 
 
 
 
 
 Crystalline 
 
 Imper- 
 
 Vit. or sub- 
 
 }J 
 
 
 Green- 
 
 
 
 fectly 
 
 resinous 
 
 
 
 ish, 
 
 
 
 con- 
 
 
 
 
 brown, 
 
 
 
 choidal 
 
 
 
 
 &c. 
 
 
 Crystalline 
 
 
 Vit. inclin- 
 
 n 
 
 
 Green- 
 
 White 
 
 
 
 ing to re- 
 
 
 
 ish- 
 
 or grey- 
 
 
 
 sinous 
 
 
 
 black 
 
 ish 
 
 99 
 
 
 Pearly- 
 
 M 
 
 
 Green 
 
 Green- 
 
 (foliated) 
 
 
 metallic 
 
 
 
 
 ish 
 
 
 Un- 
 
 Pseudo- 
 
 - 
 
 
 Brown- 
 
 
 
 even 
 
 metallic 
 
 
 
 ish 
 
 
 
 
 
 
 
 green 
 
 
 
 
 Pearly- 
 
 
 
 Bronze 
 
 
 
 
 metallic 
 
 
 
 
 
 Crystalline 
 
 
 Vit., horn- 
 
 9J 
 
 
 Green, 
 
 Colour- 
 
 
 
 like 
 
 
 brown, 
 
 less 
 
 
 
 
 
 
 or black 
 
 
 Compact 
 
 
 
 
 n 
 
 
 n 
 
 
 
 Crystalline 
 
 Conchoi- 
 
 Vitreous 
 
 Not at 
 
 None 
 
 White 
 
 
 
 dal 
 
 
 all 
 
 
 or 
 
 
 occurs also 
 
 
 
 
 
 tinted 
 
 
 Compact 
 
 
 
 
 
 
 Black 
 
 
 
 
 
 
 1 or grey 
 
 
 
 
 Flat 
 
 
 jj 
 
 
 
 
 
 
 
 
 
 (or very 
 
 
 
 
 
 
 
 slight) 
 
 
 
LITHOLOGY. 
 
 105 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard- 
 ness. 
 
 Specific 
 Gravity. 
 
 Solubility. 
 
 Behaviour before the 
 Blow-pipe. 
 
 FELSPAR. Orthoclase 
 
 6 
 
 2'5 
 
 Insoluble 
 
 Fuses on edge 
 
 (Silicate of Alu- 
 mina and Potash) 
 
 
 to 
 2'6 
 
 
 onlyinto awhite 
 enamel ; with 
 
 
 
 
 
 borax forms a 
 
 Varieties : 
 
 
 
 
 transparent 
 
 Common Felspar 
 
 
 
 
 glass 
 
 Adularia 
 
 
 
 
 
 Glassy (Sanidine) 
 
 
 
 
 
 Felstone 
 
 
 
 
 
 FELSPAR. Oligoclase 
 
 6 
 
 2'6 
 
 Insoluble 
 
 Fuses with diffi- 
 
 (Silicate of Alu- 
 
 
 to 
 
 
 culty to a clear 
 
 mina, Soda, and 
 
 
 27 
 
 . 
 
 glass 
 
 Lime) 
 
 
 
 
 
 FELSPAR, Labrado- 
 
 6 
 
 2-7 
 
 Soluble in 
 
 Fuses easily to a 
 
 rite (Silicate of 
 
 
 
 hydro- 
 
 clear glass 
 
 Alumina, Lime, 
 
 
 
 chloric 
 
 
 and Soda) 
 
 
 
 acid 
 
 
 AUGITE (Silicate of 
 
 56 
 
 3'2 
 
 
 Some varieties 
 
 Lime,Magnesia,&c.) 
 
 Varieties : 
 
 
 to 
 3'5 
 
 
 fuse easily into 
 grey glass, others 
 
 Diallage 
 
 
 
 
 almost infusible 
 
 Hypersthene 
 
 
 
 
 
 Fuses easily to a 
 
 
 
 
 
 grey or black 
 
 
 
 
 * 
 
 enamel 
 
 Bronzite 
 
 
 
 
 Slightly fusible on 
 
 
 
 
 
 thin edges 
 
 HORNBLENDE (Sili- 
 
 ) 6 
 
 2'9 
 
 
 Some varieties 
 
 cate of Lime, Mag- 
 
 
 to 
 
 
 fuse easily into 
 
 nesia, &c.) 
 
 
 3'4 
 
 
 grey glass, others 
 
 Hornblende Eock 
 
 
 
 
 almost infusible 
 
 QUARTZ. Eock 
 
 7 
 
 2'6 
 
 Soluble in 
 
 Unaltered 
 
 Crystal (Silica) 
 
 
 
 hydro- 
 
 
 Varieties : 
 
 
 
 fluoric 
 
 
 Flint 
 
 
 
 acid 
 
 
 Hornstone, Chert. 
 
 
 
 
 
 
 i 
 
 
 
 
106 
 
 FIELD GEOLOGY. 
 
 TABLE OF TESTS, for application in the field continued. 
 
 Texture. 
 
 Fracture. 
 
 Lustre. 
 
 Scratch- 
 ed by 
 knife. 
 
 Effer- 
 ves- 
 cence. 
 
 Colour. 
 
 Streak. 
 
 Granular 
 
 
 
 
 None 
 
 
 
 
 
 
 
 (or very 
 
 
 
 
 
 
 
 slight) 
 
 
 
 Crystalline 
 
 Uneven 
 
 Vitreous 
 
 Not at 
 
 None 
 
 Black 
 
 Colour- 
 
 
 
 
 all 
 
 
 
 less 
 
 Crystalline 
 (foliated) 
 
 5> 
 
 Pearly 
 
 With 
 ease 
 
 
 Various 
 
 >j 
 
 Compact 
 (foliated) 
 
 ?> 
 
 JJ 
 
 J5 
 
 
 White, 
 or green 
 
 
 
 
 Resinous 
 
 5? 
 
 
 Grey 
 
 
 Crystalline 
 
 }| 
 
 Rather 
 
 32 
 
 
 Dark 
 
 
 (foliated) 
 
 
 pearly 
 
 
 
 olive- 
 
 
 
 
 
 
 
 green 
 
 
 Compact 
 
 57 
 
 Resinous 
 
 )J 
 
 
 j 
 
 
 Crystalline 
 
 
 
 Not at 
 
 tfone 
 
 White 
 
 
 Comp. or 
 
 
 
 all 
 
 
 
 
 Gran. 
 
 
 
 
 
 
 
 
 
 
 
 Slow 
 
 Various 
 
 
 Laminated, 
 
 Laminae 
 soft and 
 
 Glistening 
 
 With 
 ease 
 
 
 
 
 
 
 earthy- 
 
 
 
 
 
 
 
 looking 
 
 
 
 
 
 
 
 
 Do. 
 
 hard and 
 
 Earthy 
 
 ?> 
 
 
 Dark 
 grey 
 
 
 
 earthy- 
 
 
 
 
 
 
 
 looking 
 
 
 
 
 
 
 j> 
 
 Do. 
 
 
 
 
 55 
 
 
 
 hard and 
 
 
 
 
 
 
 
 glisten- 
 
 
 
 
 
 
 
 ing 
 
 
 
 
 
 
 5> 
 
 
 
 
 jj 
 
 
 Black 
 
 
 JJ 
 
 
 
 
 5 
 
 
 Green 
 
 
LITHOLOGY. 
 
 107 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard- 
 ness. 
 
 Specific 
 Gravity. 
 
 Solubility. 
 
 Behaviour before the 
 Blow-pipe. 
 
 Quartzite (altered 
 
 
 
 
 
 Quartz Sandstone) 
 
 
 
 
 
 TOURMALINE 
 
 7 
 
 3' 
 
 
 Fuses with diffi- 
 
 
 
 
 
 culty 
 
 MICA (Silicate of 
 
 2'5 
 
 2-9 
 
 Insoluble 
 
 Whitens,and fuses 
 
 Alumina) 
 
 
 
 
 only on thin 
 
 
 
 
 
 edges 
 
 TALC (Bisilicate of 
 
 1*5 
 
 2-65 
 
 
 Whitens and ex- 
 
 Magnesia) 
 
 
 
 
 foliates, fusing 
 
 Variety : 
 
 
 
 
 with difficulty 
 
 Steatite 
 
 
 
 
 on thin edges 
 
 
 
 
 
 to a white ena- 
 
 
 
 
 
 mel 
 
 CHLORITE (Silicate 
 
 1-5 
 
 27 
 
 
 Fuses with diffi- 
 
 of Magnesia, Alu- 
 
 
 
 
 culty on thin 
 
 mina, and Iron) 
 
 
 
 
 edges 
 
 SERPENTINE ROCK 
 
 3'5 
 
 2-55 
 
 
 J> 5) 
 
 (Silicate of Mag- 
 
 
 
 
 into enamel 
 
 nesia) 
 
 
 
 
 
 
 
 
 Consisting of 
 
 SANDSTONE, pure 
 
 
 
 Quartz grains 
 
 calcareous 
 
 
 
 ,, in calcs. matrix 
 
 micaceous 
 
 
 
 with scales of Mica 
 
 SLATE, cleaved 
 
 
 
 Clay, metamorphosed 
 
 MICA SCHIST 
 
 
 
 Quartz and Mica (varies) 
 
 HORNBLENDE do. 
 
 
 
 Hornblende chiefly 
 
 CHLORITE do. 
 
 
 
 Chlorite, with a little Quartz, 
 
 
 
 
 
 Mica, &c. 
 
108 
 
 FIELD GEOLOGY. 
 
 TABLE OF TESTS, for application in the field continued. 
 
 Texture. Fracture. 
 
 Lustre. 
 
 Scratch- 
 ed by 
 knife. 
 
 Effer- 
 ves- 
 cence. 
 
 Colour. 
 
 Streak. 
 
 CrystallineLaminsB 
 
 
 
 Not at 
 
 None 
 
 
 more or 
 
 
 
 all 
 
 
 
 less ap- 
 
 
 
 
 
 
 parent 
 
 
 
 
 
 
 Comp. to 
 Crystalline 
 
 
 Along 
 the 
 
 Green, 
 wea- 
 
 
 
 
 inner 
 
 thers 
 
 
 
 
 border 
 
 brown 
 
 
 
 
 of wea- 
 
 
 
 
 
 
 thered 
 
 
 
 
 
 
 portion 
 
 
 
 Crystalline 
 
 
 
 J) 
 
 Green- 
 
 
 
 
 
 
 ish 
 
 
 
 
 
 
 ?) 
 
 Green- 
 
 
 
 
 
 
 ish- 
 
 
 
 
 
 
 black 
 
 
 Crystalline 
 
 | 
 
 
 Dark 
 
 
 Granular 
 
 
 
 
 grey 
 
 
 Compact 
 Conchoi- 
 
 
 
 
 Black 
 
 
 dal 
 
 
 , 
 
 
 
 
 Even 
 
 Vitreous 
 
 
 
 Grey, 
 
 
 
 
 
 
 wea- 
 
 
 
 
 
 
 thers 
 
 
 
 
 
 
 white 
 
 
 JSub-con- 
 
 " 
 
 
 Black, 
 
 
 choidal 
 
 
 
 varies 
 
 
 3} 
 
 
 
 
 Pink, 
 
 
 
 
 
 
 brown 
 
 
 Even 
 
 
 
 
 Grey 
 
 
 (or Splin- 
 schistose) tery 
 
 
 
 
 Grey, 
 wea- 
 
 
 
 
 
 
 thers 
 
 
 
 
 
 
 white 
 
 
 Glassy Conchoi- 
 
 5> 
 
 
 
 Brown 
 
 
 dal 
 
 
 
 
 or grey 
 
 
 Vesicular 
 
 
 
 
 
 
LITHOLOGY. 
 
 109 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard- 
 ness. 
 
 Specific 
 Gravity. 
 
 Consisting of 
 
 GNEISS 
 
 1 
 
 
 
 Quartz, Felspar, and Mica, in 
 layers more or less apparent 
 
 DIORITE (Green- 
 stone) 
 
 
 2*6 
 to 
 2-9. 
 
 Felspar (not orthoclase), and 
 Hornblende 
 
 GABBRO (Green- 
 stone) 
 HYPERSTHENE 
 ROCK (Greenstone) 
 
 
 2'8 
 to3' 
 2'95 
 
 Labradorite and Diallage 
 and Hypersthene 
 
 DOLERITE 
 
 Varieties : 
 Anamesite 
 Basalt 
 
 
 3' 
 
 2'80 
 2'95 
 
 and Augite (with 
 some titanif erous Iron) 
 
 J - 3> 5> 
 JJ )) 3? 
 
 FELSTONE 
 
 
 2'6 
 
 Felspar and Quartz (ortho- 
 clase) 
 
 Variety : 
 Pitchstone 
 
 
 2-35 
 
 5) >) f> 
 
 PORPHYRITE 
 
 TRACHYTE 
 
 Varieties : 
 Clinkstone (Phono- 
 lite) (partly sol. in 
 Hydro Chi. Acid) 
 
 
 2'65 
 2'65 
 2'6 
 
 Felspar (oligoclase or ortho- 
 clase), with Hornblende, 
 Mica, &c. (rarely Quartz) 
 Felspar (orthoclase), some- 
 times with Sanidine (no 
 Quartz) 
 Felspar (orthoclase), with Ne- 
 pheline and sometimes with 
 Hornblende, &c. 
 
 Obsidian 
 Pumice (Lava froth^ 
 
 
 2'4 
 2'3 
 
 Felspar (orthoclase), in a com- 
 pletely vitreous condition 
 Felspar (orthoclase), in a cel- 
 lular form 
 
110 
 
 FIELD GEOLOGY. 
 
 TABLE OF TESTS, for application in the field continued. 
 
 Texture. 
 
 Fracture. 
 
 Lustre. 
 
 Scratch 
 edby 
 knife. 
 
 Effer- 
 ves- 
 cence. 
 
 Colour. 
 
 Streak. 
 
 Crystalline 
 
 
 
 
 
 Various 
 
 
 Compact, 
 &c. 
 
 Fibrous 
 
 Metallic, 
 dull 
 
 With 
 ease 
 
 None 
 
 Black, 
 grey 
 
 Black 
 
 5) 
 
 Uneven 
 
 Vit., inclin- 
 ing to 
 Pearly 
 
 With 
 diffi- 
 culty 
 
 Rapid 
 
 Greyish 
 
 White 
 
 Crystalline 
 &c. 
 
 ?? 
 
 Conchoi- 
 dal 
 
 Uneven 
 
 Resinous 
 Vitreous 
 
 With 
 ease 
 
 With 
 diffi- 
 culty 
 
 ^"one 
 
 5) 
 
 Black 
 or 
 brown 
 
 White, 
 tinted 
 
 ?? 
 to red- 
 dish 
 brown 
 White 
 
 5> 
 
 Flat, 
 even 
 
 Metallic 
 
 With 
 
 ease 
 
 ilapid 
 
 liead- 
 grey 
 
 Lead- 
 grey 
 
 Compact 
 
 
 Dull or glis- 
 tening 
 
 j> 
 
 
 Olive- 
 green 
 
 
 Radiating, 
 &c. 
 
 
 Pearly to 
 Vitreous 
 
 ? 
 
 
 Blue 
 
 31ueish 
 white 
 
 Compact, 
 <fcc. 
 
 Conchoi- 
 dal 
 
 Vitreous 
 
 *.> 
 
 ^one 
 
 Green 
 
 Colour- 
 less 
 
 Crystalline 
 &c. 
 
 Jneven 
 
 Pearly 
 
 5) 
 
 ?iapid 
 
 Brown- 
 ish 
 
 White 
 
 Concretionary 
 
 
 
 
 
 
 
LITHOLOGY. 
 
 Ill 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard- 
 ness. 
 
 Specific 
 Gravity. 
 
 Consisting of 
 
 GRANITE 
 
 
 2-6 
 
 Quartz, Felspar, and Mica 
 
 Syenite 
 
 
 
 Quartz, Felspar, and Horn- 
 
 
 
 
 blende 
 
 
 
 
 Solubility. 
 
 Blow-pipe. 
 
 PYEOLUSITE (Binox- 
 
 2 
 
 4'9 
 
 Soluble in 
 
 Infusible alone. 
 
 ide of Manganese) 
 
 
 
 hydro- 
 
 With borax, in 
 
 
 
 
 chloric 
 
 outer flame gives 
 
 
 
 
 acid 
 
 an amethyst-co- 
 
 
 
 
 
 loured bead 
 
 CALAMINE (Garb, of 
 
 5 
 
 4'25 
 
 Soluble in 
 
 Infusible alone 
 
 Zinc) 
 
 
 
 hydrochlo- 
 
 
 
 
 
 ric acid 
 
 
 BLENDE (Sulphide 
 
 4 
 
 4- 
 
 
 
 of Zinc) 
 
 
 
 
 (Evolves sulphu- 
 
 
 
 
 
 rous acid) 
 
 SMITHSONITE (Sili- 
 
 5 
 
 3'35 
 
 Soluble in 
 
 Almost infusible 
 
 cate of Zinc) 
 
 
 
 strong so- 
 
 alone 
 
 
 
 
 lution of 
 
 
 
 
 
 caustic 
 
 
 
 
 
 potash 
 
 
 GALENA. Lead ore 
 
 2'5 
 
 7'6 
 
 Soluble in 
 
 Evolves sulph. 
 
 (Sulphide of Lead) 
 
 
 
 nitric acid 
 
 acid, and yields 
 
 
 
 
 
 on charcoal a 
 
 
 
 
 
 metallic globule 
 
 GLAUCONITE (Sili- 
 
 2 
 
 2-3 
 
 
 Fuses easily to a 
 
 cate of Iron and 
 
 
 
 
 dark magnetic 
 
 Potash) 
 
 
 
 
 glass 
 
 VIVIANITE (Phos- 
 
 2 
 
 2-66 
 
 Soluble in 
 
 Fuses, loses co- 
 
 phate of Iron) 
 
 
 
 hydrochlo- 
 
 lour, and forms 
 
 
 
 
 ric acid 
 
 magnetic glo- 
 
 
 
 
 
 bule 
 
 COPPEEAS (Sulphate 
 
 2 
 
 1'83 
 
 Soluble in 
 
 Becomes magne- 
 
 of Iron) 
 
 
 
 water 
 
 tic: gives green 
 glass with borax 
 
 CHALYBITE (Garb. 
 
 4 
 
 3'8 
 
 Soluble in 
 
 Blackens, and be- 
 
 of Iron) 
 
 
 
 hot hydro- 
 
 comes magnetic 
 
 
 
 
 chloric acid 
 
 
 Clay Ironstone 
 
 
 
 
 
112 
 
 FIELD GEOLOGY. 
 
 TABLE OF TESTS, for application at home continued. 
 
 Texture. 
 
 Fracture. 
 
 Lustre. 
 
 Scratch 
 ed by 
 knife. 
 
 p;ffer- 
 ves- 
 cerice. 
 
 Colour. 
 
 Streak. 
 
 Reniform 
 
 Fibrous 
 
 Sub-metal 
 
 With 
 
 Red 
 
 Red 
 
 &c. 
 
 
 lie 
 
 diffi- 
 
 
 
 
 
 
 
 culty 
 
 
 
 Crystalline 
 
 Sub-con- 
 
 Metallic 
 
 jj 
 
 
 Steel- 
 
 5? 
 
 &c. 
 
 choida 
 
 
 
 
 grey 
 
 
 Compact 
 
 Fibrous 
 
 Sub-metal- 
 
 55 
 
 
 Brown 
 
 Yellow- 
 
 
 
 lic 
 
 
 
 
 ish 
 
 
 
 
 
 
 
 brown 
 
 Crystalline 
 
 Conchoi- 
 
 55 
 
 Not at 
 
 None 
 
 Bronze- 
 
 Green- 
 
 
 dal, un- 
 
 
 all 
 
 
 yellow 
 
 ish 
 
 
 even 
 
 
 
 
 
 
 jj 
 
 Sub-con- 
 
 55 
 
 55 
 
 
 Iron- 
 
 Black 
 
 
 choidal 
 
 
 
 
 black 
 
 
 55 
 
 55 
 
 Adaman- 
 
 59 
 
 
 Black 
 
 White 
 
 
 or un- 
 
 tine or re- 
 
 
 
 or 
 
 
 
 even 
 
 sinous 
 
 
 
 brown 
 
 
 55 
 
 
 Vit., metal- 
 
 With 
 
 55 
 
 Sky- 
 
 Dark 
 
 
 
 lic 
 
 ease 
 
 
 blue 
 
 grey 
 
 35 
 
 Conchoi- 
 
 Metallic, 
 
 55 
 
 55 
 
 Lead- 
 
 Lead- 
 
 
 dal, un- 
 
 dull 
 
 
 
 grey 
 
 grey 
 
 
 even 
 
 
 
 
 
 
 Compact 
 (or fibrous) 
 
 
 Silky, dull 
 
 5) 
 
 Rapid 
 
 Bright- 
 green 
 
 Pale 
 green 
 
 55 
 
 
 Metallic 
 
 55 
 
 None 
 
 Brass- 
 
 Green- 
 
 
 
 
 
 
 yellow 
 
 ish 
 
 
 
 
 
 
 
 black 
 
LITHOLOGY. 
 
 113 
 
 TESTS, for further determination at home continued. 
 
 The Substance probably is 
 
 Hard 
 
 ness. 
 
 Specific 
 Gravity. 
 
 Solubility. 
 
 Blow-pipe. 
 
 HAEMATITE (Perox- 
 
 5'5 
 
 4'5 
 
 Soluble in 
 
 
 ide of Iron) 
 
 to 
 
 to 
 
 acid 
 
 
 
 6'5 
 
 5' 
 
 
 
 Impure varieties: 
 SPECULAR IRON 
 
 
 5' 
 
 
 Infusible alone. 
 
 (peroxide of Iron) 
 
 
 
 
 
 LIMONITE 
 
 6- 
 
 3'6 
 
 
 
 variety, 
 
 to 
 
 to 
 
 
 
 Bog Iron-ore 
 
 5'5 
 
 4' 
 
 
 
 PYRiTEs(Bisulphide 
 of Iron) 
 
 6 
 
 5' 
 
 
 Fuses to metallic 
 globule 
 
 MAGNETITE. Mag- 
 
 6 
 
 5' 
 
 Soluble in 
 
 Infusible alone 
 
 netic Iron ore. 
 
 
 
 hydrochlo- 
 
 
 (Proto-peroxide 
 
 
 
 ric acid 
 
 
 of iron) 
 
 
 
 
 
 CASSITERITE. Tin 
 
 6'5 
 
 67 
 
 Almost in- 
 
 )> 3> 
 
 ore (Binoxide of 
 
 
 
 soluble 
 
 
 Tin) 
 
 
 
 
 
 BLUE VITRIOL (Sul- 
 
 2'5 
 
 2'2 
 
 Soluble in 
 
 With soda on 
 
 phate of Copper) 
 
 
 
 water 
 
 charcoal yields a 
 
 
 
 
 
 bead of copper. 
 
 COPPER GLANCE 
 
 3' 
 
 5'6 
 
 Soluble in 
 
 Fuses to globule 
 
 (Sulphide of Copper) 
 
 
 
 hot nitric 
 
 of copper 
 
 
 
 
 acid 
 
 
 MALACHITE (Carb. 
 
 4 
 
 37 
 
 Soluble in 
 
 Decrepitates, 
 
 of Copper) 
 
 
 to 
 
 acids 
 
 fuses, and co- 
 
 
 
 4' 
 
 
 lours flame green 
 
 COPPER PYRITES 
 
 3'5 
 
 4-2 
 
 
 Fuses to a mag- 
 
 (Sulphide of Cop- 
 
 
 
 
 netic globule 
 
 per and Iron) 
 
 
 
 
 
 ii .A { V 
 UNIVERSITY OF 
 
 CALIFORNIA. | 
 
114 FIELD GEOLOGY. 
 
 THE MORE COMMON METALS, 
 
 their usual modes of occurrence, and tests* for approxi- 
 mate determination. 
 
 Metals are characterised by their peculiar (metallic) 
 lustre and great specific gravity. Some are found 
 " native/' but they usually occur in the state of ores, 
 that is, in chemical combination with other substances, 
 generally in veins in the older rocks, or as concretions 
 in interstratified beds. 
 
 The following Metals occur in a Native State : 
 p , , /-In plates, nuggets, grains, and threads among 
 
 '' -< the older rocks, or alluvial deposits de- 
 Silver, J ,,! P 
 
 V rived tnereirom. 
 Platinum, in grains. 
 Copper, in plates and threads. 
 
 The following Metals occur as Ores, in Veins : 
 Silver. 
 
 Copper, as Blue Vitriol, Glance, &c. 
 Lead, as Galena. 
 Iron, as Vivianite, Copperas, &c. 
 Tin, as Cassiterite. 
 Zinc, as Calamine, Blende. 
 
 The following Metals occur as Ores, in Beds : 
 
 Copper, as Malachite, Pyrites, &c. 
 
 Lead, as Galena. 
 
 Iron, as Clay-iron ore, Pyrites, Glauconite (dissemi- 
 nated grains), Chalybite, Haematite, Magnetite, &c. 
 
 Manganese, as Pyrolusite, Wad. 
 
 Zinc, as Calamine, Blende. 
 
 See Preceding Tables. 
 
LITHOLOGY. 115 
 
 Microscope. " It often happens that neither the naked 
 eye nor a good lens will help us to get at the composi- 
 tion and textural arrangement of fine-grained rocks, 
 while the rough forms of analysis mentioned in the 
 foregoing paragraphs are equally unavailing. In such 
 cases much may be learnt by examining the rocks under 
 a microscope. For this purpose a thin slice of any rock 
 which it is proposed to examine is taken, ground smooth, 
 and polished on one side."^ The polished surface is then 
 securely fastened with Canada balsam to a piece of plate- 
 glass, and the other side is ground down until the section 
 is of the required thinness and transparency. The pre- 
 paration may be covered with a plate of very thin glass 
 mounted with balsam on the slide, care being taken to 
 exclude all air-bells, and to remove all traces of the 
 emery powder and other substances used in the grinding 
 and polishing process. 
 
 " A rock-section prepared in this way enables us to 
 ascertain with precision the manner in which the dif- 
 ferent minerals are built into each other, and often 
 throws a flood of light on the origin of a rock, and on. 
 the subsequent changes which it has undergone. It 
 furnishes an opportunity of applying the delicate analysis 
 of polarised light, and thus reveals points of structure 
 in the composition of a rock which could not be ascer- 
 tained in any other way."^ 
 
 " When prepared slices are examined under the mi- 
 croscope, it is often surprising to see how minerals which 
 
 * Mr. Jordan (of the Mining Eecord Office) has invented an 
 ingenious rock-slicing machine, which may be obtained from 
 Messrs. Cotton and Co., Graf ton Street, Soho, London. 
 
 t " Students' Manual of Geology." Jukes and Geikie. 1872. 
 
 82 
 
116 FIELD GEOLOGY. 
 
 have previously been regarded, and even analysed, as 
 perfectly homogeneous substances, envelop vast quanti- 
 ties of minute crystals of other minerals."* Here comes 
 in the use of the microscope ; by its means we also "learn 
 whether a rock, whose structure is too minute to be un- 
 derstood without it, is to be classed amongst the aqueous 
 or the igneous series," and we discover "minute or- 
 ganisms, such as foramenifera, diatomaceae, or faint 
 vegetable traces in rocks, in which, without its help, 
 nothing can be detected. The broken and often water- 
 worn fragments of the aqueous rock, derived it may be 
 in the first instance from the breaking up of igneous 
 rocks, will at once reveal its origin. 
 
 " Igneous rocks are for the most part crystalline in 
 their structure, although we must at the same time re- 
 member that many crystalline rocks have been formed 
 directly from watery solution. Gypsum, calcite, rock- 
 salt, and some forms of quartz are examples of such, 
 but those that have been thus formed may be readily 
 distinguished. In his valuable paper ' On the Micro- 
 scopic Character of some Crystals,' Mr. Sorby calls par- 
 ticular attention to certain minute cavities, in even the 
 smallest crystals, which he shows to be the key to the 
 history of the crystal.''^ 
 
 Those who have the opportunity of making for them- 
 selves microscopical examination of rocks will find much 
 valuable assistance in the monographs enumerated below 
 (p. 118), there being at the present time no work specially 
 devoted to the subject. 
 
 * "Mineralogy." Rutley. 
 
 t Microscopical Structure of Rocks. Mello. " Pop. Sc. Re- 
 view," Jan. 1875. 
 
LITHOLOGY. 117 
 
 The microscope, with the apparatus required in its 
 use, is well described in Chap. i. of " Half-hours with 
 the Microscope," by E. Lankester, M.D. ; the use of the 
 polariscope in Chap. vii. ; and the " preparation and 
 mounting of objects" in an Appendix to the same work. 
 
 Chemical Analysis. Few remarks only will be made 
 on this subject, for (as Mr. Jukes has said*) " proper 
 detailed chemical analysis is not possible, as a rule, to a 
 geologist at work in the field, but he should apply for 
 this assistance not unfrequently." It is the only way 
 of ascertaining the ultimate composition of a rock, but 
 the process is generally a tedious one and requires much 
 experience. 
 
 There are some rocks and ores of the metals which 
 may be analysed without much trouble ; the method of 
 procedure is plainly given in the little work by Pro- 
 fessor Johnston mentioned in the following list, and 
 the subject is more fully treated in Bischoff's " Chemical 
 Geology." 
 
 LIST OF BOOKS OF EEFEEENCE. 
 
 MINERALOGY. Glossary of Mineralogy. Bristow. (Longmans.} 
 Mineralogy. Kutley. } (Murby's 
 
 Mineralogical Tables. Jewsberry. ) series.) 
 Manual of Geology. Jukes and Geikie. (Slack.) 
 Geology and Mineralogy. Trimmer. (Parker.) 
 Ansted's Geology. (Van Voorst.) 
 Dana's System of Mineralogy. (Tritbnerand Co.) 
 Determinative Mineralogy. Brush. (Triibner 
 
 and Co.) 
 BLOW- PIPE. Scheerer and Blandford on the Blowpipe. 
 
 Determination of Minerals by the Blowpipe. 
 Fuchs. Translated by Danby. (Field and Tuer.) 
 
 * Op. cit. p. 96. 
 
118 FIELD GEOLOGY. 
 
 MICROSCOPE. On the Microscopic Character of some Crystals. 
 Sorby, Quart. Jour. Geol. Soc. vol. xiv. pp. 453 
 500. 
 The Microscope in Geology. Forbes, Pop. Science 
 
 Review, Oct. 1867. 
 On the Microscopical Structure of Eocks. Mello, 
 
 Pop. Science Review, Jan. 1875. 
 Communications to the Geological Society. Ward, 
 
 Rutley, and others. Quart. Jour. Geol. Soc. 
 Articles by Hull, Allport, and others in the Geo- 
 logical Magazine. 
 
 Half-hours with the Microscope. Lankester. 
 (Hardwicke.) 
 
 LEVELLING, &c. Civil Engineering. P.ankine. (Griffin and Co.) 
 Mathematical Instruments. Heather. (Virtue 
 
 and Co.) 
 CHEMICAL ANALYSIS. Bischoff's Chemical Geology. 
 
 Analysis of Soils, &c. Prof. Johnston. (Slack- 
 wood.) 
 PALEONTOLOGY. Seepage 146. 
 
 PECULIARITIES OF STRUCTURE OBSERVABLE IN CERTAIN 
 BOCKS. 
 
 Concretions. Within the substance of a rock en- 
 closed nodules may frequently be found, of all sizes and 
 varying in shape from flat and angular to perfectly 
 spheroidal. These are " concretions," which sometimes 
 consist of exactly the same material as the rock itself, 
 the form only of the future nodule being indicated by a 
 slight separation of the particles, or by a faint band of 
 colour. Such indications extend not o'nly as a matter 
 of course through many successive laminae of a bed, but 
 frequently (as do the fully formed concretions) through 
 two or more beds of similar character. In other cases 
 
LITHOLOGY. 119 
 
 'the nodule is more advanced in its formation, a con- 
 siderable portion of one ingredient of the rock having 
 been by chemical action removed and aggregated around 
 the concretion. Again it may be seen in its complete 
 state when all such ingredient has been segregated from 
 the surrounding matrix and from the enclosed nucleus 
 also, in some instances entirely altering their composi- 
 tion and appearance. And at a still later stage concre- 
 tions may be noticed either wholly or partially decom- 
 posed, or they may have been dissolved by water 
 percolating through the mass which has carried away 
 their substance in solution. The cast only then remains, 
 and this also may be modified by similar action and to 
 any extent enlarged, or it may even be again filled with 
 mineral matter by a process of crystallisation. 
 
 These concretionary nodules occur in rocks of all ages, 
 and as a rule consist of some substance which has formed 
 a minor ingredient of the enclosing mass. Notable 
 examples are the flints of the Chalk and the iron-stones 
 in Carboniferous clay and of decomposed concretions, 
 the iron pyrites found in Chalk, many clays and other 
 deposits as a ball of rusty-looking powder. 
 
 Concretions may be formed within concretions by 
 further segregation of one particular substance, as, for 
 instance, of sulphide of lead or of zinc in clay-iron ore. 
 As throwing light upon the composition and origin of 
 the rock in which they are found, and on account of 
 their commercial value, concretions are of considerable 
 importance, therefore note should always be made of 
 their occurrence.* 
 
 Slickensides. The walls of a fault or of a joint may 
 
 * Ante, p. 53. 
 
120 FIELD GEOLOGY. 
 
 often be seen somewhat smoothed and finely striated in 
 a direction generally almost vertical to the bedding; 
 this is the result of one portion of the rock sliding down 
 over the other during the progress of the fracture. But 
 a similar appearance is sometimes observable which 
 evidently is not due to friction, as the striae (or rather 
 fibres) are continued into the substance of the rock ; this 
 may be due to " crystallisation in parallel fibres," or to 
 recrystallisation as pseudomorphs after fibrous aragonite. 
 The reality may easily be determined by removing a 
 portion of the striated surface ; if the striated structure 
 be apparent within, the striae are due to crystallisation 
 if not, to friction ; and the fact should then be noted 
 as evidence of some movement of disturbance. 
 
 Note on Metamorpliic Rocks. It is generally a diffi- 
 cult matter to decide whether or not a rock owes its 
 present character to the agencies of metamorphism. 
 Hocks originally deposited as sedimentary strata, and 
 having afterwards been altered, behave on a large scale 
 as do the unaltered deposits ; , e.g. " they never, like 
 (eruptive) Granite or Trap, send veins into contiguous 
 formations. In Great Britain those members of the 
 series which approach most nearly to Granite in their 
 composition, as Gneiss, Mica-schist, and Hornblende- 
 schist, are confined to the country north of the rivers 
 Forth and Clyde" (Lyell). 
 
 Eounded water-worn grains will be found in most 
 metamorphic rocks, and distinguish them from igneous, 
 when not too compact for the grains to be visible under 
 a lens ; and whatever they may at one time have en- 
 closed, they will now be found " wholly devoid of or- 
 ganic remains." 
 
LITHOLOGY. 121 
 
 CABINET SPECIMENS. 
 
 For future reference specimens should be taken from 
 a part of the rock observed in a quarry or elsewhere 
 which presents in a typical manner its noteworthy 
 features. They should represent the average colour, 
 show distinctly the crystals, grains, or laminae, and, if 
 practicable, on one side a weathered surface. Pieces 
 about one and a half inches in length by one inch in 
 width and thickness are of convenient size, but these 
 must be as nearly as possible straight-sided and rect- 
 angular. When first detached and chipped into form 
 each specimen must be wrapped in paper with the 
 locality and formation (if possible the very bed) whence 
 derived written thereon. A collection of rocks or fossils, 
 simply as such and without their original locality being 
 known, is for scientific purposes utterly valueless. 
 
 After all necessary tests have been applied for deter- 
 mination at home, each specimen should be labelled, or 
 numbered with reference to a list the label or reference 
 setting forth the kind of rock, the formation (or bed) 
 from which it came, and the locality, in this or other 
 convenient form. 
 
 Eock. Oolitic Limestone. 
 Formation. Great Oolite. 
 Locality. Box Tunnel. 
 
LI. iJ \.l A It Y 
 
 ! UNIVERSITY OF 
 
 CALIFORNIA. 
 
 PART IV. 
 
 PALAEONTOLOGY. 
 
 CHAPTER I. 
 
 Introduction Nature of Fossil Remains Review of Animal 
 Kingdom Mode of occurrence of Fossil Remains. 
 
 Introduction. Palaeontology may be defined as the 
 ^knowledge of fossil organisms, and of the laws which 
 regulate their occurrence in the earth's crust; an 
 acquaintance with these is of very great service to the 
 geologist, whether he be concerned with questions of 
 theoretical interest, or considering such as are of more 
 practical importance. 
 
 No treatise on geology or geological surveying would 
 be complete without some chapters on palaeontology, for 
 It assists the observer in ascertaining the conditions 
 tinder which any bed or series of beds were deposited, 
 and in deciding many questions regarding their age and 
 mode of formation which would otherwise remain ob- 
 scure or unknown. 
 
 As a preliminary to such investigations, it is of course 
 necessary that the palaeontologist should be well 
 acquainted with the structure and habits of the various 
 tribes, genera, and species now existing upon the globe, 
 
 * The first three Chapters of Palaeontology are from the pen of 
 Mr. A. J. Jukes Browne, B.A., F.G.S., of H.M. Geological 
 Survey. 
 
PALEONTOLOGY. 123 
 
 especially such as are most nearly allied to those occur- 
 ring in the fossil state. When in the possession of such 
 knowledge, a study of the fossil contents of a bed, pre- 
 suming them to exist in sufficient abundance, tells him 
 at once whether the formation was marine, estuarine, 
 lacustrine, or terrestrial ; in the three former cases the 
 fossils will be for the most part remains of invertebrate 
 aquatic animals, and an examination of the number and 
 forms of these will greatly help him to form an opinion 
 as to whether the rate of deposition was slow or rapid, 
 whether the water was deep or shallow, near shore or 
 far from land. 
 
 Finally, an acquaintance with the different faunas and 
 floras, which have at different times inhabited the world 
 and formed part of the general succession of life upon. 
 the earth, enables the palseontologist to estimate the 
 .relative age of any particular group of fossils, and to 
 assign them to their probable place in the geological 
 series. In the absence of organic remains, indeed, there 
 is often only slight evidence towards the solution of such 
 problems, and, except where the relative position and 
 lithological characters of the rocks are very marked, the 
 fossil evidence is of great use in confirming the conclusions 
 derived from an examination of the strata themselves. 
 
 The important doctrine that strata may be identified 
 by their fossil contents was first taught by William 
 Smith, and is thus expressed in a sentence extracted 
 from his " Stratigraphical System :" " Organised fossils 
 are to the naturalist as coins to the antiquary ; they are 
 the antiquities of the earth, and very distinctly shew 
 its gradual regular formation with the various changes 
 of inhabitants in the watery element." 
 
124 FIELD GEOLOGY. 
 
 Now obviously before we can apply this highly useful 
 doctrine to any particular series of beds, and before we 
 consider any further the ultimate use of such investiga- 
 tions, we must become thoroughly conversant with the 
 nature and mode of occurrence of fossils, and with the 
 ways and means of collecting them. The following ob- 
 servations therefore are offered for the purpose of giving 
 some information on these several points, and of shewing 
 how, by a regular and systematic method of procedure, 
 the field-geologist may furnish properly-collected ma- 
 terials for subsequent study, whether he works out such 
 results for himself, or leaves them to be dealt with by a 
 professed palaeontologist. But we must here remark, 
 that palaeontological results, however carefully and 
 thoroughly worked out, should never be taken as con- 
 clusive by themselves, and without being confirmed by 
 the facts or probabilities of stratigraphical evidence, as 
 far as these can be ascertained ; it is only in such cases 
 as those of outlying deposits that, in the absence of any 
 such confirmatory evidence, the character of the fauna 
 may be held sufficient to decide the questions of relative 
 age or contemporaneity with other distant formations. 
 The geologist therefore should be careful as far as 
 possible to make his palasontological enquiries proceed 
 hand in hand with those regarding the relations of the 
 strata which contain the fossil relics. 
 
 Again, he must not only collect the fossils from 
 localities and beds where they happen to exist in an 
 exceptionally good state of preservation, but take care 
 to secure all the specimens he can from every bed in the 
 series, even where these are in an obscure or fragmentary 
 condition. In this way he will obtain knowledge which 
 
PALAEONTOLOGY. 125 
 
 will lead to a thorough and philosophic description of 
 the rocks composing the area upon which he is engaged, 
 and will enable him to understand aright its physical, 
 stratigraphical, and palseontological peculiarities. 
 
 I. NATURE OF FOSSIL KEMAINS. 
 
 Fossils have been denned as " organic remains buried 
 in the earth," the operations of natural causes being of 
 course understood, and no limitation as to the subsequent 
 lapse of time nor any reference to their present state 
 being allowed to enter into the definition ; since, as Mr. 
 Jukes has well observed, "any accumulation of shells, or 
 bones, or plants, which could be said to be buried in 
 the earth by any other than human agency, even if that 
 burial took place last year, would be well worth the at- 
 tention of the palaeontologist." Our first enquiry must 
 have reference to the nature of these remains, the par- 
 ticular organic forms which are likely to occur fossil, 
 and the various states of preservation in which they are 
 severally and collectively found. 
 
 It is not every buried organism that leaves behind it 
 a permanent record of its previous existence, and only 
 those animals which contain a bony skeleton, or are en- 
 closed in a hard shell or test, can as a rule become 
 definitely fossilized; while plants and those animals 
 which do not possess any such hard structures are rarely 
 found, except in the form of impressions or tracks on the 
 surface of beds the peculiar mineralization which 
 woody matter undergoes being of course an exception to 
 this statement. 
 
 Again, the nature of the remains or records of past 
 
126 FIELD GEOLOGY. 
 
 existences will naturally vary according to the class of 
 animals by which they were originated, and setting 
 plants aside for the present, it will be worth while 
 reviewing the animal kingdom for the purpose of seeing 
 what groups are likely to be met with at all in the fossil 
 state, and which of them so occur in greatest frequency 
 and abundance. 
 
 EEVIEW OF ANIMAL KINGDOM. 
 
 VERTEBRATA. 
 
 Mammalia occur rarely, except in recent fluviatile 
 deposits, and then generally in the shape of 
 separate bones and teeth. 
 
 Birds from their aerial existence, are still rarer as 
 fossils, bones seldom occurring ; but their foot- 
 prints and even impressions of their feathers 
 are known. 
 
 Reptilia. Eemains of all recent and extinct orders, 
 except the Ophidia and Lacertilia, are tolerably 
 abundant ; their bones, teeth, scutes, and in some 
 cases their eggs and coprolites being found. 
 
 Amphibia are represented in certain formations by 
 their bones and teeth, as well as their tracks or 
 footprints. 
 
 Pisces. The bones, teeth, and scales of fishes are com- 
 mon in almost every formation, from the Silurian 
 upwards. 
 
PALAEONTOLOGY. 12T 
 
 INVERTEBKATA. 
 
 Mollusca. Eemains of all those classes possessing in- 
 ternal or external shells are very abundant ; the 
 Tunicates being soft-bodied are alone unrepre- 
 sented. 
 
 Annulosa. Of Insects, the skins, limbs, and wings 
 are occasionally found ; of Myriapoda and 
 Arachinda remains are very rare ; of Crustacea,. 
 the limbs and carapaces are found in abundance, 
 and from the earliest times. 
 
 The Annelids are only known by the shells of 
 Tubicola, and by the tracks and burrows of other 
 orders. 
 
 Annuloida. Echinoderms are frequent fossils, leaving 
 remains of their tests, stems, arms, or spines. 
 
 Scolecida, having no hard parts, are quite un- 
 known. 
 
 Ccelenterata. The Actinozoa present abundant remains 
 of their hard skeletons or corals ; but the Hy- 
 drozoa, being mostly soft-bodied, have left few 
 traces. 
 
 Protozoa are chiefly represented by the spicules of 
 Sponge and the minute shells or tests of Fo- 
 raminifera. 
 
 Since the majority of rocks composing the crust of 
 the earth are of aqueous and principally marine origin, 
 we should naturally expect the fossils which they con- 
 tain to be the remains of aquatic and principally marine 
 beings ; this at once accounts for the preponderance of 
 such forms in the above list as are commonly met with 
 in the fossil state. 
 
128 FIELD GEOLOGY. 
 
 Thus, in the Vertebrata, the remains of mammals and 
 birds are among the rarest of geological relics, even in 
 beds of littoral or terrestrial origin, save those of very 
 recent date ; on the other hand, marine reptiles and 
 fishes are found in almost all the later fossiliferous 
 deposits, their vertebrae, scales, and teeth being occasion- 
 ally very abundant ; they seldom occur, however, in 
 anything like a perfect condition, except in certain 
 strata which have been formed quietly and rapidly 
 enough to envelop them before dismemberment. 
 
 Among the Invertebrates the group that is by far the 
 most useful and important to geologists is that of the 
 Mollusca ; they usually present us with a complete 
 enveloping shell or test, instead of the fragmentary 
 remains which are generally left to represent the indi- 
 viduals of the Vertebrate classes ; and from their con- 
 stant occurrence in almost every fossiliferous bed they 
 form an excellent standard of reference in considering 
 questions of relative age and position. William Smith 
 has happily likened fossil organisms to coins and an- 
 tiquities, and the remains of rnollusca are to geologists 
 as the numismatic relics of a kingdom which has lasted 
 from the earliest dawn of life upon the earth down to 
 the present day. 
 
 Corals and Echinoderms occasionally occur in con- 
 siderable profusion, and sometimes form great thick- 
 nesses of rock. Eoraminifera too are of very general 
 distribution, but from their small size and low place in 
 the animal scale, they are not of much practical use to 
 the geologist. Crustacea are of more limited occurrence, 
 most abundant in beds of littoral origin, but rare in 
 sandy strata, and often absent in deep-sea deposits. 
 
PAL/EON TOLOGY. 129 
 
 II. Mode of Occurrence of Fossil Remains : Petri- 
 faction. When organisms have once become buried 
 in deposits formed at the bottoms of seas, lakes, or 
 rivers, and their soft parts have decayed away, it might 
 be thought that the hard portions would remain then 
 unchanged, until disentombed by the hands of the geolo- 
 gical excavator. This, however, is not the case ; on the 
 contrary, they have in most instances been subjected 
 either to contemporaneous or subsequent mineralizing 
 processes, by means of which they are more or less 
 hardened and petrified. 
 
 It often happens that the animal matter in decom- 
 posing has given rise to various chemical reactions, 
 which have resulted in the formation of fresh mineral 
 matter and its concentration round the body of the de- 
 caying organism ; in such a case the animal becomes 
 included within the mass, and its harder parts, being 
 usually preserved from further change, are disclosed on 
 the splitting open of the nodule or concretion which is 
 thus formed. 
 
 Where, however, this does not take place, and the 
 fossil is simply enclosed in the ordinary matrix of the 
 rock, it is always liable to more or less subsequent 
 .alteration ; in pure clays this change is generally very 
 slight, simply consisting in the complete abstraction of 
 the organic constituents, and if the test or skeleton is 
 siliceous little alteration is effected ; but in other rocks, 
 and where the shell or test is of a calcareous nature, it 
 frequently happens that the whole of it has disappeared, 
 and has either been replaced by other mineral matter, 
 or else the space which the shell once occupied is left 
 open, and nothing remains but the external impression 
 
 9 
 
130 FIELD GEOLOGY. 
 
 and the internal cast formed of the material which filled 
 up the empty shell. 
 
 Fossils therefore may be considered as occurring 
 chiefly in four different states or conditions, viz. : 
 
 1. As unchanged shells or tests. 
 
 2. As replaced shells or " pseudomorphs." 
 
 3. As internal casts. 
 
 4. As external impressions. 
 
 1. Unchanged Fossils. These may at once be distin- 
 guished from those that have been replaced by their 
 mode of disintegration ; they peel off in concentric 
 layers, and disclose the original lamellar or cellular 
 structure of the shell. Crag fossils and those of many 
 sands and clays occur in this state of preservation, and 
 are quite unaltered save by the abstraction of all the 
 organic matter, for which reason they fall to pieces very 
 easily. 
 
 2. Replaced Fossils. Those that have undergone re- 
 placement split with a definite angular cleavage quite 
 through the shell. The fossils of the chalk, for instance, 
 though still calcareous, split in this way, and the bivalves 
 have moreover entirely lost their internal nacreous layer, 
 so that no traces of the hinge or muscular impressions 
 are, as a rule, visible. In other limestones this calcitic 
 cleavage is still more marked, rhombohedral fragments 
 may be chipped out of the thicker shells or from the 
 tests and spines of Echinoderms, while inside perfect 
 crystals may often be found. This is the case even 
 with the" fossils of some argillaceous beds, and every 
 one is familiar with Lias Ammonites which have been 
 cut and polished to show the chambers full of calcite 
 
PALAEONTOLOGY. 131 
 
 spar; in other cases the replacing material is Iron- 
 pyrites, Selenite, or Silica.] 
 
 The agency which produces such changes is simply 
 water charged with carbonic acid and holding in solution 
 the various mineral substances above mentioned ; this 
 acidulated water, percolating through the rocks, slowly 
 and gradually dissolves away the carbonate of lime com- 
 posing the shell, and in many cases replaces it particle 
 by particle with the other mineral which it happens to 
 contain in solution, and which is thus exchanged for the 
 carbonate of lime ; in other cases the material of the 
 shell may have been entirely removed without any con- 
 comitant replacement, the calcite, silica, or other mine- 
 ral having been subsequently introduced into the vacant 
 space thus left, and filling it up as it would any other 
 cavity in the rock. 
 
 But to explain the change of structure in some cal- 
 careous shells which are not wholly replaced, it seems 
 necessary to suppose that the percolating water con- 
 tained a saturated solution of carbonate of lime, some 
 of which crystallized out in the cellular interspaces of 
 the shell, binding the whole and imparting to it a crys- 
 talline structure, just as the sand of Montmartre, being 
 infiltrated by carbonate of lime, is gathered together by 
 crystalline action into rhombohedral prisms, taking the' 
 form of calcite crystals. 
 
 Sand 4. Casts and Impressions. The internal cast and 
 external impression may be considered together, as they 
 nearly always exist, whether the shell be unaltered, re- 
 placed, or removed ; they are of course very much better 
 seen a"nd realized in the latter case, when the cast is 
 loose or nearly so, and may be taken out of the cavity,. 
 
 92 
 
132 
 
 FIELD GEOLOGY. 
 
 thus revealing the impression or reversed facsimile of 
 the external form of the organism that once filled the 
 empty space. 
 
 Suppose, for instance, we are dealing with the remains 
 of a bivalve shell, such as a Trigonia in the figure, 
 
 Fig. 20a. Trigonia clavellata, Kimmeridge Clay. 
 Cast and Impression. 
 
 Tve find that the cast exhibits two raised ledges occupy- 
 ing the position of the muscular impressions, connected 
 by a slightly raised ridge, corresponding to the pallial 
 line which marks the attachment of the animal's mantle ; 
 the interspaces between the teeth will also appear, and 
 sometimes concentric or radiating ridges answering to 
 those of the shell itself. In the same way the internal 
 structure of any hollow body, whether coral, univalve 
 shell, or^echinoderm, is faithfully represented by its cast, 
 and where opportunities for comparison exist, its genus 
 and even its species may in many cases be ascertained. 
 
PALEONTOLOGY. 133 
 
 While the internal cast thus exhibits in relief all the 
 markings and irregularities which existed on the inner 
 surface of the shell or test, the external cast or impres- 
 sion is indented by all the markings which ornamented 
 its outer surface. Where the shell is absent, therefore, 
 and we wish to gain .an idea of its appearance in relief, 
 we can effect this by taking an artificial cast from the 
 external impression, and thus obtain an accurate repre- 
 sentation of the pre-existing shell. Occasionally even, 
 but very rarely, this is effected by natural means, and 
 we then get an internal cast, showing all the characters 
 of the external shell ; this seems to be only produced 
 in soft sandy marls or muds, where a thin shell having 
 been dissolved and never replaced, the impression of its 
 exterior has been gradually and equally squeezed on to 
 the still soft mud inside ; this, on the desiccation and 
 consolidation of the rock, would present every appear- 
 ance of the original fossil, though the closest examina- 
 tion would reveal no traces of shell structure; in- 
 stances are found in some fossils from the chalk marl 
 and from the Bracklesham beds in the Isle 
 
 L I B R A li V 
 
 CHAPTER If. UNIVE liSITy <; 
 
 PALAEONTOLOGY (continued). 
 Method of Collecting Fossils EiailipleV * f ^ - N 1 A 
 
 I. Method of Collecting Fossils. In Part II. p. 53, 
 the mode of procedure in examining any natural or 
 artificial section, whether cliff, cutting, pit, or quarry, 
 was described, and it was pointed out that notes should 
 be taken of the nature and contents of the rocks therein 
 
134 FIELD GEOLOGY. 
 
 exposed ; also that these open cuttings and sections 
 must be closely searched for the fossil remains which 
 the several beds may contain. 
 
 Although it is not often that every separate bed or 
 layer contains definite remains of fossil organisms, yet 
 there are few without some traces of animal life, and 
 even in a limited series of strata there is usually one 
 at least which contains them in greater or less abun- 
 dance. These remains must be diligently collected, 
 whether they be large or small, common or rare, in a 
 good or bad state of preservation ; for this object cer- 
 tain tools and apparatus are necessary, and these are 
 different according to the nature of the rocks that are 
 likely to be met with in the area surveyed. For in- 
 stance, among hard rocks, or even those of moderate 
 compactness, a hammer and chisel will of course be 
 required, and indeed the geologist should rarely be 
 without the hammer and pick in some form or other ; 
 on the other hand, where only soft clays or marly sands 
 are to be explored, a good strong clasp-knife will be 
 found a more effective instrument for extracting the 
 fossils that they may contain. 
 
 Large and strong specimens may be simply wrapped 
 in paper, with a note of the bed and locality written on 
 it ; while the smaller and more delicate specimens are 
 best stowed in small boxes, with wool or soft paper, 
 common chip-boxes are perhaps as serviceable as any 
 for this purpose. 
 
 All this apparatus may be carried in a bag slung across 
 the shoulders, but where large and heavy " takes " are 
 expected, and especially among the older rocks, a fisher- 
 man's basket will be found admirably suited for such 
 service, since in this the various fossils and rock-frag- 
 
PALAEONTOLOGY. 135 
 
 ments can be firmly and securely packed as they are 
 collected, thus preventing their tendency to shake about 
 and scratch one another during further exploration. 
 
 When fossils are extracted from hard rocks, and are 
 detached in lumps or fragments of considerable size, they 
 should only be reduced and roughly trimmed according 
 to the dimensions of the enclosed organism, leaving 
 further manipulation until the specimen arrives at its 
 destination, whether this be in a private or public col- 
 lection, for the final chipping and trimming often 
 requires to be done carefully and leisurely, so as not 
 to break or damage the fossil. A deft and skilful 
 handling of the hammer and chisel is indeed only to be 
 attained by much practice, and the ultimate development 
 of a specimen is always a more or less delicate operation, 
 from which it does not always escape uninjured. 
 
 In chiselling anything out of a soft rock like chalk 
 care should be taken to direct the chisel away from 
 the fossil, and to extract a larger lump than may at 
 first sight seem necessary, otherwise the rock may flake 
 up and destroy the specimen ; when safely extracted, it 
 should then be slightly trimmed, wrapped in plenty of 
 paper, and stowed in the bag or basket. 
 
 With still softer rocks, such as shales, clays, and clayey 
 sands, the specimens can at once be reduced to the 
 proper size and shape by means of the knife ; and then, 
 if carefully conveyed, will need little further attention, 
 unless some preservative, such as gum or gelatine, be 
 required for their ultimate conservation. 
 
 For fossils that are found in loose sands, whether 
 freshwater or marine, and that may be extracted whole 
 and free from the matrix, more care is needed ; they 
 are almost always in a tender and perishable condition, 
 
136 FIELD GEOLOGY. 
 
 and should be immediately packed in boxes with wool or 
 bran. 
 
 Note. Where these materials are unattainable, 
 or have been forgotten, clean sand from the shore 
 or pit itself may be used as a fair substitute, though 
 it has, of course, the disadvantage of being much 
 heavier. 
 
 Ordinary chip-boxes have already been mentioned as 
 useful for this purpose, and are easily stowed and car- 
 ried, but they are sometimes hardly strong enough, and: 
 such small wooden cases as those in which baking- 
 powder is sometimes sold will be found serviceable. 
 
 We have hitherto spoken of the fossil remains which 
 are actually included in the matrix of the bed or stratum, 
 and were deposited there in most cases after the death 
 of the animal, and during the accumulation or deposition 
 of the materials which form the matrix. But since 
 every bed or layer of a sedimentary rock once formed 
 the bottom of a river, lake, or sea, we should naturally 
 expect to find some fossils resting on their surface more 
 or less in the position of growth, as well as the tracks or 
 marks of animals which also come under the category 
 of fossils. These, of course, will be seen by separating 
 the layers which compose the series of strata under 
 examination, or may be found on the surface of beds 
 already exposed. The Dudley slabs are good examples 
 of this, and other instances are often found in the shales 
 and limestones of the Oolitic series. 
 
 Nodule beds, bone beds, and layers of flint or chert 
 all also mark pauses in deposition of greater or less 
 length, and are often very rich in organic remains. In- 
 deed, the nodular concretionary masses which usually 
 characterize such beds owe their origin mainly to the- 
 
PALEONTOLOGY. 137 
 
 presence of organic matter, the decomposition of which 
 has resulted in their production. Those containing 
 phosphate of lime or other materials of commercial 
 value are often extensively worked by pits or trenches ; 
 admirable opportunities are thus afforded for collecting 
 the fauna they exhibit, both in the pits themselves and 
 among the washed heaps of these products.* 
 
 For the same reason all concretionary nodules, 
 whether accumulated in layers or not, should always 
 be examined and broken open, since many excellent 
 fossils are frequently obtained therefrom ; such as those 
 enclosed in the ironstone nodules of the Carboniferous 
 series, and in the Septarice of many clays. 
 
 II. Examples. In illustration of the previous re- 
 marks let us refer to the diagrams, figs. 5, 6, 7, and 8, 
 and the descriptions contained in Parts I. and II. of 
 this work. 
 
 (a.) It will be remembered that the first quarry we 
 entered, in imagination, was a sand-pit near the church, 
 in fig. 5 ; in the light grey sand at the bottom of this 
 pit a few fossils were noticed ; these should be^ex- 
 tracted from the matrix or detached with portions of 
 the rock, some being in the state of buff-coloured casts, 
 others retaining their shelly covering, some are frag- 
 mentary, others in a fairly perfect state. After a dili- 
 gent search among these friable beds we collect some 
 twenty or thirty specimens, which we recognise to be 
 various species of Ammonites, Terebratula, Ehynconella, 
 Ostrea, and Plicatula, &c., &c. These are carefully 
 
 * The so-called "coprolite-pits" in the neighbourhood of Cam- 
 bridge form an example of this mode of occurrence, and the con- 
 sequent method of collection. 
 
138 FIELD GEOLOGY. 
 
 wrapped in paper, or stowed in chip-boxes, according 
 to their size and fragility. The small sponge-like 
 nodules are also taken for future examination with the 
 lens and microscope. 
 
 In the marly or sandy chalk above we notice that but 
 few fossil remains occur; we extract, however, one or two 
 Belemnites, a few obscure Terebratulse, and fragments 
 of Inoceramus shell. These, though apparently worth- 
 less and not easily identified, should nevertheless be 
 kept, and their occurrence noted, since in other pits on 
 the same horizon better specimens may be obtained with 
 which these may be compared. 
 
 If we are not able to name at once the species which 
 have thus been collected, we can leave spaces in the 
 note-book and fill in the names after consulting palrc- 
 ontological authorities. 
 
 (6.) Passing down the road to the brickyard or gault- 
 pit, which was next examined, and searching over the 
 clay which is thrown aside, as well as in the vertical 
 cutting of the pit itself, we find that fossils are not un- 
 common. They mostly retain their shells or tests in 
 very fair condition, and only contain the dark mud or 
 gault in which they lie ; some, however, which we ob- 
 serve to occur mainly along one definite line or horizon, 
 are filled with iron pyrites or with impure phosphate of 
 lime, many of these being merely casts in one or other 
 of the above minerals. 
 
 From the workmen we also buy what fossils they have 
 found and laid aside when digging the clay in the win- 
 ter ; these are generally only the finer and larger species, 
 while for the smaller and less conspicuous fossils we 
 must search the pit ourselves. We may note the fol- 
 
PALAEONTOLOGY. 139 
 
 lowing as among those obtained, reserving the more 
 doubtful forms for future identification : 
 
 Ammonites varicosus. Solarium ornatum. 
 
 splendens. Plicatula pectenoides. 
 
 rostratus. Avicula gryphseoides. 
 
 Hamites sp. ? Inoceramus sulcatus. 
 
 Belemnites attenuatus. Nucula pectinata. 
 
 Eostellaria sp. ? Pentacrinus Fittoni. 
 
 We also secure a few of the different forms of the 
 phosphate nodules from the seam or band in which they 
 were noticed to occur. 
 
 It is not always, however, that a clay-pit is so fossil- 
 iferous as that described above ; indeed, if the workmen 
 happen not to have any specimens on hand, as is often 
 the case in summer-time, little else may be obtained 
 from such gault-pits than a few Ammonites, Belemnites, 
 Plicatulse, and phosphate nodules, though a regular seam 
 of the last is tolerably sure to afford a more or less 
 abundant and well-preserved fauna. 
 
 (c.) At the well we are not likely to obtain any fossils 
 unless some of the clay which was extracted still remains 
 near the mouth, or the well-sinkers happen to have kept 
 any specimens from the beds passed through. 
 
 (d.) The chalk-pit must be examined carefully, for it 
 is not so easy to detect fossils in the upper chalk as it 
 is in most other secondary rocks ; the remains are nearly 
 of the same colour as the rock itself, and this is of such 
 dazzling whiteness that looking closely at it in bright 
 sunshine is very trying to the eyes ; however, we must 
 first betake ourselves to a shady part, and get gradually 
 accustomed to the glare. 
 
140 FIELD GEOLOGY. 
 
 We may begin by turning our attention to the flint - 
 bands which have been remarked upon before, and by 
 examining the nodules in place, and the heaps of those 
 which we see by their white exterior to have been in 
 place, we soon collect several Echinoderms : Ananchy- 
 tes, Micraster, and the spines of Cidaris, together with 
 a few specimens of Inoceramus and Spondylus, all im- 
 bedded in the flint. These must be trimmed as well as 
 possible, although flint is very intractable, and just as 
 likely to split through the fossil as along the plane in- 
 tended. Flint is perhaps best manipulated by holding 
 the lump in the left hand, and chipping it by well-aimed 
 blows of the hammer, each one directed away from the 
 enclosed fossil. 
 
 The flints having been well looked over, we turn to- 
 the beds of chalk themselves, and when our eyes become 
 used to its appearance we soon extract, by means of 
 hammer and chisel, specimens of the same species just 
 found, with the addition, perhaps, of some smaller 
 fossils, such as Magas pumilus, Terebratula carnea, 
 Ehynconella octoplicata, Crinoid stems, and plates of 
 Marsupites Milleri. 
 
 We examine also the tests of the large and smooth 
 Echinoderms, such as Ananchytes and Galerites, which 
 are often the resting-places of Crania, Plicatula, and the 
 minute Thecidium Wetherellii, as well as various species 
 of elegant Polyzoa and Serpulce. A chalk-pit is very 
 frequently a lime-kiln also, and the men at work almost 
 invariably preserve some of the more striking fossils 
 they meet with in quarrying the rock ; these, therefore,, 
 may generally be obtained " for a consideration." 
 
 (e and /.) In the loam at the brickyard few fossils are 
 likely to be found, except perhaps some fragments of 
 
PALEONTOLOGY. 141 
 
 Cstrea Bellovacina among the green- coated flints at 
 the base. In the sands above we find only a few speci- 
 mens of Ostrea and Cyrena cordata, which are readily 
 separated from the matrix, but in a very friable condition, 
 so that careful handling and packing are required ; but 
 these afford sufficient evidence (in addition to that of 
 stratigraphical position) to identify the beds as belong- 
 ing to the Woolwich and Eeading group of the Eocene 
 series. 
 
 An example of surveying among the older rocks is 
 also given in fig. 21, and our palseontological explora- 
 tions are here even more useful and necessary to con- 
 firm the conclusions drawn from the stratigraphical 
 evidence. 
 
 In the sandstone quarry, No. 2, it will be noted 
 that some fragments of a substance resembling wood 
 were found ; these, when subsequently sliced and 
 subjected to a microscopic examination, show the cha- 
 racteristic structure of coniferous wood, but at the time 
 of collecting they could only be entered as " fragments 
 of wood, coniferous ?" In the shales forming the upper- 
 most part of the quarried cliff fish scales were noticed 
 to be tolerably abundant, and portions of the crushed 
 skeletons may also be detected, belonging to the Lepi- 
 dostean fish Palceoniscus comptus, which is characte- 
 ristic of the Permian marl-slate ; we are sure, therefore, 
 that the shales belong to this division of the series. 
 
 In the limestone quarry to the south-west fossils are 
 much more abundant, though confined to the grey lime- 
 stone in the upper part of the quarry. Some parts of 
 this may not be accessible, but numerous blocks of it 
 are lying about, and we find that the fossils are readily 
 extracted from the rock ; at the same time they are 
 
142 FIELD GEOLOGY. 
 
 tolerably hard and strong, and need little care beyond 
 the protective power of old newspapers. 
 
 The character of the rock and its stratigraphical 
 position are almost sufficient to prove that it be- 
 longs to the lower part of the Magnesian limestone, 
 and the fossils abundantly confirm this surmise, being 
 those which are characteristic of the second member of 
 this series, the " fossiliferous limestone" of Prof. King. 
 Among them are, Fenestella retiformis, Producta Jior- 
 rida, Gamarophoria crumena, Monotis speluncaria, 
 Sckizodus obscurus, and Bakevellia antiqua. 
 
 Eound the mouth of the coal-mine there are scattered 
 portions of the various measures passed through in 
 sinking the shaft; among the fragments of sandstone 
 and fireclay thus brought to light we may find remains 
 of Calamites, Stigmaria, and Sigillaria ; in the shales 
 and shaly sandstones we detect impressions of Lepi- 
 dodendron stems, together with the broken fronds of 
 Neuropteris, Sphenopteris, and other ferns, all black 
 and carbonized. 
 
 In the dark shales also Unio-like shells occur, belong- 
 ing to the genera Anthracosia and Anthracoptera, but 
 they are often more or less crushed ; the best specimens 
 are obtained from the dark-grey ironstone nodules which 
 are scattered about, and which we ascertain to have been 
 derived from the shales below the first coal-seam (see 
 section on p. 212). Besides the bivalve shells, these 
 nodules contain beautiful fragments of fern leaves, as 
 well as Lepidostrobi, or the cones of the Lepidoden- 
 dron, and sometimes the scales or coprolites of fish ; it 
 was indeed the decomposition of the animal or vegetable 
 matter that determined their formation. 
 
PALEONTOLOGY. 
 
 The above-mentioned organic remains stamp the beds 
 containing them as being of terrestrial, freshwater, or at 
 most estuarine origin ; but amongst the debris we notice 
 slabs and pieces of impure limestone which yield speci- 
 mens of more marine forms of life, such as Goniatites 
 Listeri and Aviculopecten papyraceus, and possibly a 
 closer view may disclose the presence of smaller organ- 
 isms, such as the minute annelid, Microconchus carbo- 
 narius. We subsequently ascertain that the fragments 
 disclosing those remains have come from the bed marked 
 limestone in the section on p. 212. 
 
 Now, descending the pit, we explore some of the 
 main passages or gate-roads, under the guidance of 
 the foreman, or " butty-collier ;" in some places we 
 find the roof above us to be crowded with splendid 
 impressions of ferns and other plants, the shales im- 
 mediately above the coal being often extremely rich 
 in such remains ; and we thence obtain better and 
 more perfect specimens than we could at the mouth 
 of the pit, with the additional advantage of knowing 
 the precise horizon or band in which they occur. 
 
 From the information thus obtained we learn that 
 frequent oscillations of level took place in the area 
 where these beds were deposited; for instance, the 
 shales above the third coal-seam mark a slight de- 
 pression of the low-lying land on which the vegetation 
 grew, and its temporary submergence under the waves 
 of the neighbouring lake or estuary; after a slight 
 upheaval which allowed the growth of the thin coal, 
 it again sank under the water and was covered up by 
 the overlying shales, the depression reaching its farthest 
 extent when the impure marine limestones were formed ; 
 
144 FIELD GEOLOGY. 
 
 but that this depth was not very great, is evidenced by 
 their muddy and shaly character, caused by the admix- 
 ture of sediment brought down from higher land. A 
 reverse movement soon set in, the area slowly rose 
 again and the shales with ironstone nodules were ac- 
 cumulated ; finally, the bay or estuary must have been 
 silted up by the deposition of such sediment and again 
 became a land surface at the time when the plants 
 forming the uppermost coal-seam grew and nourished in 
 their rank luxuriance. 
 
 CHAPTER III. 
 
 Preservation, Naming, and Arrangement of Fossils Value of 
 Palaeontological Evidence Evidence of Physical Conditions. 
 
 Preservation of Fossils. Having collected and brought 
 away our fossils in the manner described in the preced- 
 ing pages, it behoves us to say a few words regarding 
 their further treatment and mode of preservation. 
 
 We have already recommended that a note of the 
 locality and the bed from which they were obtained 
 should be written on the paper or box in which they 
 are enclosed, and if this is done at the time, they may 
 be deposited at headquarters and left till winter or 
 wet weather affords leisure for dealing with them. 
 
 They should then be taken out, carefully inspected 
 and sorted, only the very worthless duplicates from the 
 same bed and place being put on one side ; attention 
 must then be paid to the more delicate specimens, such 
 as those obtained from the loam-pit in fig. 8, from Crag- 
 sands or from River-gravels ; these will require thorough 
 
PALEONTOLOGY. 145 
 
 soaking in a solution of gum or gelatine (the latter 
 being of such strength as just to set on cooling). Speci- 
 mens that have been cut out of soft sandy clays will 
 also be benefited by such soaking, since they are apt to 
 crack and crumble in drying ; such treatment may in 
 many cases be deferred until the specimens have 
 arrived at their ultimate destination, wherever that 
 may be. 
 
 Chalk fossils and those that have been obtained from 
 any similar porous limestone along the sea-shore should 
 be soaked in fresh water for several weeks, the water 
 being changed at least once a week ; this is the only 
 way we know of to prevent the efflorescence of the salt 
 in such cases, and the consequent splitting up of fossils 
 which have cost time and pains to extract. We have 
 now in our collection Chalk Echinoderms and other 
 fossils which were thus treated seven or eight years ago, 
 only one or two of them having "gone" probably in con- 
 sequence of insufficient soaking. 
 
 Naming and Nomenclature. Having thus prepared 
 our fossils for their final packing on the completion of 
 the geological survey of the district, every specimen 
 ought to be numbered, and the numbers entered in a 
 special book, the name, locality, and " location " of each 
 being entered opposite every one. With regard to the 
 naming, it will probably be impossible to name all, 
 without reference to other authorities than are then at 
 command; in these cases the numbers will show the- 
 specimens which remain for future identification. 
 
 We will now suppose that the whole collection has 
 arrived at its ultimate resting-place, whether this be a 
 private or public museum. 
 
 10 
 
146 FIELD GEOLOGY. 
 
 In the latter case further trouble is probably taken off 
 our hands by the staff of palaeontologists and assistants, 
 and from them we obtain a full account of the fossils 
 obtained in the several beds and localities of the district 
 explored. 
 
 It may be well, however, to give a few hints for the 
 furtherance of private work in this department, and 
 firstly to give a list of the principal books of reference 
 necessary for the identification of fossils, those for 
 England and France alone being mentioned. 
 
 The Publications of the Palccontographical Society, 
 in which 4000 species of British fossils have already 
 been figured and described. 
 
 Decades of the Geological Survey of England. 
 
 McCoy's Palaeozoic Fossils, published by Prof* 
 Sedgwick. 
 
 Sowerby's Mineral Conchology. 
 
 Mantell's Medals of Creation. 
 
 Owen's Palaeontology and Nicholson's Manual of 
 Palaeontology will also be found useful. 
 
 Baily's Figures of Characteristic British Fossils. 
 (Van Voorst.) 
 
 D'Orbigny's Paleontologie Francaise. 
 
 Pictet's MaUriaux pour la Paleontologie Suisse. 
 
 For the fossils of particular formations, such works 
 as Dixon's " Geology of Sussex," Murchison's " Siluria," 
 Eamsay's " North Wales," and other Survey Memoirs 
 must be consulted, as well as papers in the Journals and 
 Transactions of the Geological Societies of London 
 and Paris. 
 
PALEONTOLOGY. 147 
 
 In identifying the various species by means of these 
 volumes we shall probably find some which are ap- 
 parently intermediate in their characters between two 
 nearly allied forms, and are thus difficult of certain de- 
 termination, since they might belong to either of the 
 figured species ; others, again, may vary more or less 
 from the particular type which happens to be figured. 
 Now it is often the practice in such cases to put these 
 -aside for duplicates, or even to throw them away alto- 
 gether, only inserting in the collection what are termed 
 -" typical specimens ;" but this mode of procedure is 
 reprehensible in the highest degree, since it tends to 
 confirm the old superstition that species are definite 
 -abstractions, and to draw hard L and fast lines between 
 -cognate forms which are unnatural and nonexistent 
 in reality. 
 
 These forms ought, on the contrary, to be placed with 
 the species to which they are allied, and to be labelled 
 as a variety of that which they most closely resemble. 
 Had this always been done in private and public collec- 
 tions, we should now be in possession of many more 
 facts regarding the life-history of such forms than we 
 have knowledge of at the present time.* 
 
 Besides these intermediate and somewhat indetermm- 
 .able forms, we may also discover some that do not 
 
 * It will frequently be found that such intermediate forms 
 have been collected from intermediate beds, one of the allied 
 species being mainly found above, and the other below, the 
 horizon in which such middle varieties occur. It is unnecessary 
 to point out the bearing of this on Darwin's Theory of Evolution 
 {by descent with modification) ; every one who has read the 
 "Origin of Species" will understand it, and every one who has 
 not read that work should do so without delay. 
 
 102 
 
148 FIELD GEOLOGY. 
 
 appear to be figured or described at all in any of the 
 books we can consult ; these should be put on one side, 
 and if possible shown to some palaeontologist who makes 
 a special study of the groups to which they severally 
 belong : should they prove to be entirely new species 
 or definite varieties, they may be described as such when 
 an account of the district comes to be written. 
 
 The whole subject of scientific nomenclature is at 
 present in confusion ; but, without going into the matter, 
 we may briefly point out the main causes of this un- 
 satisfactory state of things, and suggest some means of 
 remedy. 
 
 In the first place, the illusory ideas regarding the 
 definiteness of species have greatly contributed to it, for 
 different authorities have had different estimates of 
 specific differences, and many so-called species are after 
 all mere arbitrary creations of individual opinion. 
 
 Secondly, there exists the great desire of finding some- 
 thing new to Science, which too often takes the form of 
 <c species-making " instead of discovery. 
 
 Thirdly, the difficulty in many cases of finding out 
 whether a species has been previously described, either 
 by British or foreign writers, has operated in the same 
 direction. All, in fact, are fruitful causes of the multi- 
 plication of synonyms. 
 
 The first of them opens a difficult question, for a 
 name is undoubtedly required even for varieties, if 
 they are tolerably definite and constant; the only 
 way out of the difficulty appears to lie in the more 
 general use of subgeneric titles, grouping species to- 
 gether under their respective genera, and using in fact 
 a trinomial instead of a binomial nomenclature. 
 
PAL/EONTOLOGY. 149 
 
 The only cure for the second tendency is to read 
 Darwin's " Origin of Species," and persons who will not 
 -do that may be given up as hopeless. 
 
 The last and most direct cause of the production of 
 synonyms is only to be avoided by greater industry and 
 carefulness, and by making fuller acquaintance with 
 the work done in foreign countries ; in this endeavour 
 palaeontologists will be greatly assisted by the annual 
 publication of the " Geological Record," their only regret 
 probably being that it had not an earlier commencement. 
 Arrangement of Collections. We have often been 
 questioned as to the best mode of displaying and 
 arranging fossils. With regard to the mode of arrange- 
 ment, whether according to their place in the succes- 
 sion of life or in the succession of strata, there can be 
 only one answer : the latter is always preferable for 
 geological purposes, however much the former may 
 commend itself to the pure biologist. 
 
 Nevertheless, in collections of any size, it is always 
 possible to have zoological arrangement, by placing to- 
 gether those of the same natural group and cla.ss, and 
 pursuing the same order of classes throughout all the 
 formations. 
 
 Secondly, regarding the method of displaying the 
 fossils themselves : in museums, where the collections 
 are supposed to be perfected, and to remain as arranged 
 for many years, the specimens are generally fastened 
 down on tablets ; but in private collections, which are 
 used for constant reference, and to which frequent ad- 
 ditions are made, such a plan is attended with many 
 disadvantages. The simpler and better way is to place 
 them in small card-board trays, made of multiple sizes 
 
150 FIELD GEOLOGY. 
 
 like the tablets ; every fossil may then be fully ex- 
 amined and handled, while the labour and time ex- 
 pended in the process of gumming them down is 
 thereby avoided, and the additional advantage of space 
 is gained at the same time. The names may be written 
 on separate pieces of card-board, and either placed loose 
 in the tray or pinned on to its edge. 
 
 Value of Palceontological Evidence. Having now 
 explained the method in which the fauna and flora of 
 a district should be collected and worked out, we are 
 in a position to estimate the full importance and use- 
 fulness of the information thus obtained, and the light 
 which is often thrown by this knowledge upon such 
 questions as the relative and comparative age of beds, 
 and the physical conditions under which they were 
 deposited. 
 
 The insight afforded by Paleontology into these sub- 
 jects' was briefly pointed out at the commencement of 
 Chapter i, but may now be more fully explained. 
 
 First, as regards the various conditions under which 
 rocks may have been formed, we find that our know- 
 ledge is chiefly derived from the evidence furnished by 
 the organic remains they contain. It is clear that the 
 terrestrial, fluviatile, lacustrine, estuarine, or marine 
 origin of the fossils may generally be ascertained by a 
 comparison with the habits of the living species belong- 
 ing to the same or nearly allied genera. 
 
 But we may go farther than this, and even obtain 
 some idea of the probable climate of past periods ; when 
 we find in certain beds the bones of crocodiles, snakes, 
 and turtles, together with palm-fruits and remains of 
 other plants which now live only in tropical regions, 
 
PALEONTOLOGY. 151 
 
 we are forced to believe that the climate of the British 
 islands must then have had a more tropical character. 
 Again, when in more recent deposits we discover re- 
 mains of the reindeer, musk-ox, and mammoth, and in 
 other beds of the same age certain species of mollusca 
 which now only inhabit the seas of more northern 
 regions, we have good evidence for concluding that 
 the climate of Britain was then very much colder than 
 it is at present. 
 
 From a consideration of the character and abundance 
 of the fossil remains we may sometimes gain an idea of 
 the :ime that elapsed during their accumulation. The 
 formation of a bed of limestone crowded with organisms 
 of various kinds, many of the corals and crinoids being 
 still in their upright position of growth and surrounded 
 by the broken debris of others, together with the shells 
 of numerous species of mollusca, the formation of such 
 a bed must have occupied a long series of years. 
 
 A bed of sand or sandstone will, on the other hand, 
 enclose a very different class of relics, if it contain any at 
 all, bivalve shells, mostly with separated valves, the 
 waterworn fragments of some corals and gasteropods, and 
 possibly a few drifted bones of some terrestrial animal, 
 may be found ; such remains indicate the rapid accumu- 
 lation of the materials composing the stratum, which in- 
 deed, although of the same thickness, may only have 
 occupied in its formation as many weeks as the bed of 
 limeston e did years. 
 
 Other facts are also elicited by such a comparison ; 
 for many of the fossils occurring in the limestone belong 
 to genera which exist only in deep water, and the very 
 mode in which they occur shows that the water above 
 
152 FIELD GEOLOGY. 
 
 was still and quiet ; we conclude, therefore, that it was 
 deposited at the bottom of a deep and quiet sea. 
 
 In the sandstone, on the contrary, the presence of 
 terrestrial remains and the drifted and waterworn con- 
 dition of the other fossils found therein plainly indicate 
 their connection with a shallow sea, the action of cur- 
 rents, and the neighbourhood of land. 
 
 Again, such indications as sun-cracks and the impres- 
 sions of rain-drops tell us of parching heat, of passing 
 showers, and even show us the direction from which 
 the wind blew in those old days of the earth's histoiy. 
 
 We will turn now from such evidence of the sur- 
 rounding conditions at the time when the beds vere 
 formed, and approach the more difficult questions con- 
 nected with the comparative age of the different beds 
 which are found in different localities, and make up the 
 crust of the earth. 
 
 It has been observed, that every group of strata in 
 the geological series, and frequently even the minor 
 beds composing the several formations, have each their 
 own peculiar assemblage of fossils; it often happens that 
 a particular species, or an assemblage of species, are 
 only found in a particular bed or stratum, or if found 
 at all elsewhere it is so rarely in comparison with their 
 abundance in this particular stratum, that they still 
 merit the name of characteristic species. Still more 
 is it the case when a considerable formation or group of 
 beds is examined, for these invariably contain a greater 
 or less number of species which are absolutely peculiar 
 to the group, and are never found in the rocks above or 
 below. 
 
PALEONTOLOGY. 153 
 
 This generalization first made by the " Father of 
 English Geology/' William Smith leads directly to 
 the doctrine that " strata may be identified by fossils," 
 for if these groups of characteristic species have been 
 changing throughout all time, and were different in 
 every geological period, we see at once that the relative 
 age and position of beds may be known from their em- 
 bedded fossils. 
 
 To take a simple instance : Ammonite shells and the 
 bones of an Ichthyosaurus have been discovered in some 
 of the Arctic Islands, and we at once conclude that the 
 rocks containing them belong to some member of the 
 Secondary system ; moreover, we guess that they belong 
 to the Jurassic formation, since the Ammonite more re- 
 sembles an Oolitic form than any known in Cretaceous 
 rocks. 
 
 Another more detailed instance may be given : It is 
 known that there are among the Upper Silurian rocks 
 three distinct beds of limestone ; where these occur in 
 a disturbed and faulted district, we- might discover a 
 -quarry in limestone, forming part of an area which had 
 been faulted up or down, and thus separated from beds 
 with which it was originally continuous. In such a case 
 the stratigraphical evidence might be very obscure, but 
 the palaeontological evidence would at once decide the 
 matter, for on finding among the fossils which had been 
 collected from the limestone specimens of the large 
 Brachiopod, Pentamerus Knightii, we should recognize 
 in it a fossil characteristic of the Aymestry limestone, 
 .and have little hesitation in referring the beds to that 
 formation ; if, on the other hand, we found such forms 
 as Acervularia luxurians, Euomphalus discors, and 
 
154 FIELD GEOLOGY. 
 
 Orthis rustica, we should be sure that the rock be- 
 longed to the Wenlock group, and was the second of 
 the three limestones above mentioned. 
 
 As the application of fossil evidence has often a very 
 practical bearing, we may take even another instance 
 from the history of coal-mining : it has frequently hap- 
 pened that much labour and money have been fruitlessly 
 wasted in the search for coal, which would have been 
 prevented by the slightest acquaintance with the laws 
 of palaeontology, the beds through which shafts have 
 been sunk yielding fossils, not of the species mentioned 
 on p. 142, but such as are characteristic of Silurian 
 shales or Kimmeridge clay. 
 
 The late Mr. J. B. Jukes says : " I have known, even 
 in the rich coal district of South Staffordshire, shafts 
 continued down below the Coal-measures, deep into the 
 Silurian shales, with crowds of fossils brought up in 
 every bucket, and the sinker still expecting to find coal 
 in beds below those Silurian fossils. I have known 
 deep and expensive shafts sunk in beds too far above 
 the coal-measures for their ever being reached, and 
 similar expensive shafts sunk in black shales and slates 
 in the lower rocks far below the coal-measures, where a 
 pit might be sunk to the centre of the earth without 
 ever meeting with coal. Nor are these fruitless enter- 
 prises a thing of the past. They are still going on in 
 spite of the silent warnings of the fossils in the rocks 
 around, and in spite of the loudly-expressed warnings 
 of the geologists, who understand them, but who are 
 supposed still to be vain theorists, and not to know so- 
 much as the ' practical man.' Within my own expe- 
 rience large sums of money have been absolutely thrown 
 
PALEONTOLOGY. 155- 
 
 away, which would have been saved by the slightest ac- 
 quaintance with palaeontology."* 
 
 The mode of procedure, however, indicated in the 
 above examples necessarily presupposes that the strati- 
 grapliical succession has first been established in some 
 other locality where the relative position of the beds is 
 clearly seen, so that there can be no doubt about the 
 comparative t age of the faunas they contain ; in other 
 words, the successional order of the faunas must first 
 be clearly ascertained before a knowledge of them can 
 assist in elucidation of faulted or outlying districts; 
 while these conditions have not been fulfilled palseon- 
 tological reasoning is very likely to lead the observer 
 astray. 
 
 Another caution must also be given, viz. : that the 
 knowledge thus obtained will only apply to a limited 
 area ; this is a natural result of the distribution of life 
 in " provinces," during past as well as present time ; 
 consequently in comparing districts which are wide 
 apart we cannot be sure of the absolute contempo- 
 raneity of deposits which may contain similar fossils, 
 we can only say that the relative order of succession is 
 the same in both regions. Mr. Jukes says, " It is yet 
 doubtful whether these specific differences, existing to- 
 gether with generic identities, be due to a want of exact 
 synchronism in the age of the beds or to the geographi- 
 cal distribution and limitation of the life of the period, 
 whether in fact they are the result of time or space." 
 Where, however, the areas are widely separated, the for- 
 mer is the more probable cause, and in correlating the 
 
 * " Manual of Geology," Jukes and Geikie, p. 512. 
 
156 FIELD GEOLOGY. 
 
 series of beds in each, we should be careful to speak of 
 them only as homotaxial and not contemporaneous. 
 
 For instance, rocks in Bohemia and Scandinavia, con- 
 taining the same genera of trelobites as are found in our 
 lingula flags, have been correlated with them and with 
 one another, as if they were absolutely contemporane- 
 ous ; owing, however, to the above considerations this 
 cannot be regarded as accurately true, though it is cer- 
 tain that they occupy the same place in the geological 
 series of the several countries. 
 
 From the preceding considerations we learn that 
 palseontological science, although so useful a hand- 
 maiden to that of geology, is not always to be implicitly 
 trusted in her guidings and indications. Geognosy, 
 though a more reticent, is perhaps a safer guide, when 
 her counsel is obtainable; but we should constantly 
 avail ourselves of the assistance offered by both on our 
 geological ways, and never lose sight of either except 
 where the exigencies of the road oblige us. 
 
PALEONTOLOGY. 157" 
 
 L I IJ K A U 1 
 
 UNIVERSITY < 
 
 CALIFORNIA 
 
 CHAPTER 
 
 Characteristic Fossils Table of Fossils. 
 
 Characteristic Fossils. The interruptions of continuity 
 in the conditions under which the rocks were formed,, 
 and the resulting variations in their enclosed life-remains,, 
 afford a means for their classification. They are thus 
 divided into great groups or systems, representing life- 
 periods and eras, corresponding to such divisions and 
 sub-divisions. 
 
 "Each of the great groups has an assemblage of 
 fossils peculiar to it, so that the general assemblage 
 of fossils found in one group is not found in any other 
 group, either above or below. As minor exceptions to 
 this rule, particular species of fossils seem occasionally 
 to range in to two, or perhaps even three, adjacent groups, 
 occurring perhaps in the upper part of one group, rang- 
 ing through the whole of the group above it, and appear- 
 ing in the lower part of the group above that. Some 
 species, on the other hand, are found only in a very small 
 part of one group, either throughout the lateral extension, 
 of the beds wherever they occur, or sometimes limited 
 to some small locality in those beds. 
 
 " When a single species or an assemblage of several 
 species occurs in a group of rocks, whether large or 
 small, and has never been found except in that group- 
 
158 FIELD GEOLOGY. 
 
 of rocks, and is almost always found wherever the group 
 extends, we may speak of these as the characteristic 
 species of the group. It occasionally happens that the 
 fossils of such a group are so nearly allied biologically 
 that naturalists form them into a genus, or into one or 
 two genera, which may then be spoken of as equally 
 characteristic."* 
 
 A list of the more common characteristic fossils has 
 been compiled from various sources, f and is given below, 
 arranged not in the order of succession of the rock for- 
 mations, but alphabetically, so that if a fossil be known 
 the approximate (if not exact) geological position of the 
 rock from which it has been derived can readily be de- 
 termined. 
 
 * " Manual of Geology," Jukes and Geikie, p. 502. 
 t Murchison's Siluria. 
 
 Lyell's Manual, Students' Elements, &c. 
 
 Jukes and Geikie's Manual. 
 
 Buckland's Bridgewater Treatise. 
 
 Man te IPs Medals, Wonders of Geology, &c. 
 
 Phillips' Manual, Palceozoic Fossils, &c. 
 
 M'Coy, Palceozoic Fossils. 
 
 Portlock, Geological Reports. 
 
 Owen, Palaeontology. 
 
 Wright, Brit. Foss. Echinodermata. 
 
 King, Permian Fossils. 
 
 Geological Magazine. 
 
 Tabular View of British Fossils stratigraphically arranged. 
 
 Publications of H. M. Geological Survey. 
 the Geological Society. 
 
 Palceontographical Society. 
 
PALAEONTOLOGY. 
 
 159 
 
 LIST OF CHAKACTEEISTIC FOSSILS. 
 
 ACTINOZOA. 
 
 GENUS. 
 
 Acervularia 
 
 SPECIES. 
 
 - luxurians 
 
 U. Silurian. Wenlock. 
 
 Alveolites - 
 
 - Labechei 
 
 U. Silurian. Wenlock. 
 
 
 repens 
 
 4 
 
 
 suborbicularis 
 (characteristic) 
 
 ^ 
 
 > L. Devonian. 
 
 Amplexus - 
 
 - coralloides 
 
 Carboniferous. 
 
 Anabacia 
 
 - heinispherica - 
 
 L. Oolite. Inf. Oo. 
 
 Aracl i nophy Hum. 
 
 - Hennakii 
 
 Devonian. 
 
 Balanophyllia 
 Calamophyllia 
 
 - calyculus 
 radiata 
 
 O. Pliocene. R. Crag. 
 L. Oolite. Gt. Oo. 
 
 Eunomia 
 
 - Stokesii 
 
 M. Oolite. Cor. Oo. 
 
 Caryophillia 
 
 - annularis 
 
 M. Oolite. Cor. Oo. 
 
 Thecosmilia 
 
 
 
 Clisiophyllum 
 
 -sp. 
 
 Carboniferous. 
 
 Crelosmilia 
 
 - laxa 
 
 U. Cretaceous. U. Chalk. 
 
 Cyathaxonia 
 
 - Siluriensis 
 
 U. Silurian. Ludlow. 
 
 Oyathina 
 
 - Bowerbankii - 
 
 U. Cretaceous. Gault. 
 
 <Jyathophyllum 
 
 - angustum 
 
 Silurian. Llandovery. 
 
 
 coespitosum, 
 
 } 
 
 
 peculiar to 
 
 > M. and U. Devonian. 
 
 
 Devonian - 
 
 ) ' 
 
 
 sp. 
 
 Carboniferous. 
 
 Cyclocyathus 
 
 - Fittoni 
 
 U. Cretaceous. Gault. 
 
 Cystiphylluni 
 
 - vesiculosum - 
 
 Devonian. 
 
 Dasmia 
 
 - Sowerbyi 
 
 L. Eocene. 
 
 Favosites 
 
 - cervicornis 
 
 L. and M. Devonian. 
 
 
 fibrosus 
 
 Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 Gotlandicus - 
 
 Silurian. Bald (Caradoc) to 
 
 
 
 Ludlow. 
 
 Flabellum - 
 
 - Woodii - 
 
 O. Pliocene. Wh. Crag. 
 
 Halysites 
 
 - catenularius - 
 
 U. and L. Silurian. Llandeilo 
 
 
 
 to Ludlow. 
 
 Heliolites - 
 
 - Grayi 
 
 U. Silurian. Wenlock. 
 
 
 W wlia^to P ~- 
 
 Devonian. 
 
 Holocyatis - 
 
 - elegans - 
 
 L. Cretaceous. U. Neocomian. 
 
160 
 
 FIELD GEOLOGY. 
 
 Isastrea 
 
 - Conybeari 
 
 L. Oolite. Gt. Oo. 
 
 
 explanata 
 
 M. Oolite. Cor. Oo. 
 
 
 Murchisoni 
 
 Lias. 
 
 
 oblonga - 
 
 U. Oolite. Portland. 
 
 Litharea 
 
 - Webster! 
 
 M. Eocene. 
 
 Lithostrotion 
 
 - affine 
 
 Carboniferous. 
 
 
 basaltiforme - 
 
 M 
 
 Lonsdaleia - 
 
 - floriformis 
 
 Carboniferous. 
 
 Micheliriia - 
 
 - favosa 
 
 Carboniferous. 
 
 Micrabacia - 
 
 - coronula 
 
 U. Cretaceous. U. Gr. 
 
 Monticnlipora 
 
 - favulosa 
 
 L. Silurian. Llandeilo. 
 
 Monti valtia 
 
 - cuneata 
 
 M. Lias. Marlstone. 
 
 
 trochoides 
 
 L. Oolite. Inf. Oo. 
 
 Omphyma - 
 
 - turbinatum 
 
 Silurian, lia'la to WenlocTc. 
 
 Paracyathus 
 Parastrcea 
 
 - caryophillus - 
 - striata 
 
 L. Eocene. 
 U. Cretaceous. U. Gr. 
 
 Petraia 
 
 - bina 
 
 Silurian. U. Llandovery and 
 
 
 
 Wenlock. 
 
 
 Celtica - 
 
 L. M. and U. Devonian. 
 
 
 elongata 
 
 Silurian. U. Llandovery. 
 
 Pleurodictyum 
 
 - problematicum 
 
 L. and M. Devonian. 
 
 Poly celi a 
 
 - profunda(cAa- 
 racteristic) - 
 
 > M. Permian. Mag. L. 
 
 Protoseris - 
 
 - sp. 
 
 M. Oolite. Cor. Oo. 
 
 Solenastrcea 
 
 - cellulosa 
 
 U. Eocene. 
 
 Stenopora - 
 
 - fibrosa - 
 
 Silurian. Llandeilo to Lud- 
 loiv. 
 
 Stephanophyllia 
 
 - Bowerbankii - 
 
 U. Cietaceous. L. Cli. 
 
 Stromatopora 
 Stylina 
 
 - placenta 
 - tubulifera 
 
 Devonian. 
 M. Oolite. Cor. Oo. 
 
 Syringopora 
 
 - bifurcata 
 
 Silurian. Llandovery to Lud- 
 
 
 
 loiv. 
 
 
 ramnlosa 
 
 Carboniferous. 
 
 Thamnastrrea 
 
 - arachnoides 
 
 M. Oolite. Cor. Oo. 
 
 
 concinna 
 
 L. and M. Gt. and Cor. Oo. 
 
 Theococyathns 
 
 - Moorei 
 
 L. Lias. 
 
 Trochocyathus 
 
 - conulus 
 
 U. Cretaceous. Gault. 
 
 Trochosmilia 
 
 - sulcata 
 
 U. Cretaceous. Gault. 
 
 Turbinolia 
 
 - Bowerbankii - 
 
 M. Eocene. 
 
 Zaphrentis - 
 
 -sp. 
 
 Carboniferous. 
 
 ANNELIDA. 
 
 Arenicolites 
 
 - didyma 
 
 Cambrian. 
 
 
 linearis 
 
 L. Silurian. Stiver Stones. 
 
 Chondrites 
 
 - acutangulus - 
 informis 
 
 L. Silurian. Llandeilo. 
 
PALAEONTOLOGY. 161 
 
 Cornulites - 
 
 - serpularius 
 
 - Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 Orosaopodia 
 
 - lata 
 
 - U. Silurian. Ludlow. 
 
 
 Scotica - 
 
 - L. Silurian. Bala. 
 
 Histioderma 
 
 - Hibernica 
 
 - L. Cambrian. Longmynd. 
 
 Nerites 
 
 - Cambrensis 
 
 - L. Silurian. LlandeUo. 
 
 
 Sedgwickii 
 
 LlandeUo < Bala. 
 
 Palaeochorda 
 
 - major 
 
 - L. Silurian. LlandeUo. 
 
 
 minor 
 
 jj J5 
 
 Serpula 
 
 - amphisboana 
 articulata 
 
 - U. Cretaceous. L. Chalk. 
 Gault. 
 
 
 coacervites 
 
 - U. Oolite. Purbeck. 
 
 
 tetragona 
 
 - L. Oolite. For. Marl. 
 
 
 vertebralis 
 
 - M. Oolite. Oxf. Clay. 
 
 Serpulites 
 
 - dispar - 
 
 - U. Silurian. Ludlow. 
 
 
 longissinms 
 
 Wenlock and 
 
 
 
 Ludlow. 
 
 Spirorbis 
 
 - carbonarius 
 
 - Carboniferous. 
 
 Tentaculites 
 
 - annulatus 
 
 - M. Devonian. 
 
 
 ornatus 
 
 - Silurian. Bala to Wenlock. 
 
 
 tenuis 
 
 - U. Silurian. Ludlow. 
 
 Trachyderma 
 
 - coriaceum 
 
 ?) 
 
 
 laeve 
 
 - L. Silurian. Bala. 
 
 
 squamosum 
 
 - U. Silurian. Ludlow. 
 
 Vermicularia 
 
 - Bognoriensis 
 
 - L. Eocene. 
 
 
 concava 
 
 - U. Cretaceous. U. Gr. 
 
 AVES. 
 
 Haley ornis - - toliapicus - L. Eocene. 
 Lithornis - - vulturensis - L. Eocene. 
 Palaeornis - - Cliftii - L. Cretaceous. Wealden. 
 
 Athyris 
 Atrypa 
 
 BRACHIOPODA. 
 
 plaiiosulcata 
 
 desquamata 
 
 hemispherica 
 
 marginalis 
 
 reticularis 
 
 Carboniferous. 
 
 L. M. and U. Devonian. 
 
 Silurian. Llandovery. 
 
 Llandovery to De- 
 
 vonian. 
 
 Calceola 
 Camarophoria 
 
 culiar to - ) 
 - crumena= ^ 
 Schlotheimi 
 (characteristic) ) 
 
 Dev onian. 
 
 M. Permian. Mag. L. 
 11 
 
162 
 
 FIELD GEOLOGY. 
 
 Chonetes 
 
 Crania 
 
 - Hardrensis 
 lata 
 
 - Ignabergensis 
 Parisiensis 
 
 Discina (Orbicula) nitida 
 
 punctata 
 rugata - 
 
 striata 
 Leptrena (Silurian 
 
 to Lias) - Moorei - 
 
 Lingula 
 
 Lingiillela - 
 
 Meristella - 
 Obolus 
 Orbiculoidea 
 Orthis 
 
 sp. 
 
 " attemiata 
 cornea 
 
 Crednerii 
 
 crumena 
 Dumortieri 
 lata 
 
 Lewisii - 
 mytiloides 
 (characteristic) 
 ovalis 
 parallela 
 striata - 
 tennis ' - 
 Davisii - 
 lepis 
 
 pumila - 
 plebeia - 
 transversus 
 Forbesii 
 Actonise - 
 
 alata 
 
 arcuata (cha- 
 racteristic} - 
 caligramma 
 elegantula 
 
 flabellum 
 granulosa 
 insularis 
 lata 
 
 L. M. and U. Devonian. 
 U. Silurian. Downton. 
 U. Cretaceous. U. Chalk. 
 
 '.' " 
 
 Carboniferous and M. Per- 
 mian. 
 
 U. Silurian. Bala. 
 
 Silurian. Wenlock and Lud- 
 low. 
 
 Silurian. Ludloiv. 
 
 U. Lias. 
 
 Silurian. U. Llandovery. 
 
 L. Silurian. Llandeilo. 
 
 U. Silurian. Ludlow and 
 Downton. 
 
 Carboniferous and M. Per- 
 mian. 
 
 U. Silurian. U. Llandovery- 
 
 O. Pliocene. Wh. Crag. 
 
 U. Silurian. Ludlow. 
 
 " 
 > M. Permian. Marl-Slate. 
 
 M. and U. Oolite. 
 
 U. Silurian. U. Llandovery. 
 
 Ludlow. 
 
 L. Eocene. 
 U. Cambrian. Lingula flags. 
 
 U. Cretaceous. V. Chalk. 
 M. Devonian. 
 U. Silurian. Wenlock. 
 U. Silurian. Wenlock. 
 L. Silurian. % Bala and Llan- 
 dovery. 
 L. Silurian. Llandeilo. 
 
 > L. Devonian. 
 
 Silurian. L. Llandovery. 
 
 Llandeilo to Lud- 
 
 loiu. 
 
 L. Silurian. Llandeilo. 
 L. and M. Devonian. 
 L. Silurian. Llandeilo. 
 Silurian. U. Llandovery. 
 
PALEONTOLOGY. 
 
 163 
 
 Orthis 
 
 Pentamerus 
 
 Productus 
 
 Eetzia 
 Rhynconella 
 
 lenticularis 
 
 lunata 
 
 orbicularis 
 
 resupinata 
 
 reversa 
 
 rustica 
 
 vespertilio 
 
 galeatus 
 
 globosus 
 Knightii 
 
 lens 
 
 U. Cambrian. Lingula flags. 
 U. Silurian. Ludlow. 
 
 ". 
 
 Carboniferous. 
 
 Silurian. U. Llandovery. 
 U. Silurian. Wenlock. 
 L. Silurian. Llandeilo. 
 U. Silurian. Wenlock and 
 
 Ludlow. 
 
 Silurian. U. Llandovery. 
 Wenlock and 
 
 Ludlow. 
 Silurian. U. Llandovery. 
 
 lirata 
 
 U. Llandovery. 
 Silurian. I 
 
 undatus - 
 
 Silurian. 
 
 aculeatus 
 
 Carboniferous. 
 
 giganteus 
 
 
 
 hemisphaericus 
 horridus (cha- 
 
 j> 
 
 prselongus 
 
 U. Devonian. 
 
 scabriculus 
 
 Carboniferous. 
 
 semireticulatus 
 
 j> 
 
 sp. 
 
 M. Permian. Marl-slate. 
 
 Baylei 
 
 U. Silurian. Wenlock. 
 
 acuminata 
 
 Carboniferous. 
 
 augustifrons - 
 
 Silurian. U. Llandovery. 
 
 concinna 
 
 L. Oolite. Gt. Oo. 
 
 crassa 
 
 Silurian. L. Llandovery. 
 
 Cuvieri - 
 
 U. Cretaceous. L. Chalk. 
 
 Gibbsii - 
 
 L. Cretaceous. L. Gr. 
 
 inconstans 
 
 U. Oolite. Kim. Clay. 
 
 latissima - 
 
 U. Cretaceous. U. Gr. 
 
 navicula - 
 
 U. Silurian. Wenlock and 
 
 
 Ludlow. 
 
 neglecta 
 
 Silurian. U. Llandovery. 
 
 nucula 
 
 Llandovery to- 
 
 
 Ludlow. 
 
 obsoleta 
 
 L. to U. Oolite. 
 
 octoplicata 
 
 U. Cretaceous. U. Chalk. 
 
 pleurodon 
 
 Carbon if erous. 
 
 psittacea 
 
 Newer Pliocene. 
 
 
 112 
 
164 
 
 FIELD GEOLOGY. 
 
 Khynconella 
 
 - rimosa 
 
 L. and M. Lias. 
 
 
 spinosa 
 
 L. Oolite. Inf. Oo. 
 
 
 tetahedra 
 
 M. Lias. 
 
 
 varians 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 
 Wilsoni - 
 
 Silurian. Llandovery to Lud- 
 
 
 
 low. 
 
 Siphonotreta 
 
 - Anglica - 
 
 U. Silurian. Wenlock. 
 
 S infer (M ' 
 
 micula 
 
 L. Silurian. Llan deilo flags. 
 
 to Lias) 
 
 tti 
 
 - alata 
 
 M. Permian. Mag. L. 
 
 
 cuspidata 
 disjuncta=- 
 Verneuillii - 
 
 Carboniferous. 
 [ U. Devonian. 
 
 
 glabra 
 
 Carboniferous. 
 
 
 lineata 
 
 M. and U. Devonian. 
 
 
 Isevicosta 
 
 L. and M. Devonian. 
 
 
 pinguis - 
 
 Carboniferous. 
 
 
 plicatella 
 
 Silurian. Llandovery to Lad- 
 
 
 
 low. 
 
 
 rotundata 
 
 Carboniferous. 
 
 
 speciosa - 
 
 L. and M. Devonian. 
 
 
 striata 
 
 Carboniferous. 
 
 
 trigonalis 
 
 
 
 
 undulata 
 
 Permian. 
 
 
 Walcottii 
 
 L. and M. Lias. 
 
 Spiriferina 
 
 - cristata (cha- 
 racteristic) - 
 
 M. Permian. Mag. L. 
 
 Stringocephalus 
 
 - Burtini exclu- 
 
 > M. Devonian. 
 
 Strophalosia 
 
 - caperata - 
 
 U. Devonian. 
 
 
 Goldfussii 
 (characteristic] 
 
 j- M. Permian. Mag. L. 
 
 Strophomena 
 
 - complanata 
 compressa 
 
 L. Silurian. Bala. 
 Silurian. U. Llandovery. 
 
 
 depressa 
 
 Bala to Ludlow. 
 
 
 englypha 
 
 Llandovery to 
 
 
 
 Ludloiv. 
 
 
 grandis 
 
 L. Silurian. Bala. 
 
 
 imbrex 
 
 U. Silurian. Wenlock. 
 
 
 rhomboidalis - 
 
 Silurian and Devonian. 
 
 Terebratella 
 
 - pectita - 
 
 U. Cretaceous. U. Gr. 
 
 Terebratula 
 
 - biplicata 
 
 5 
 
 
 bisinuata 
 
 M. Eocene. 
 
 
 carinata - 
 
 L. Oolite. Inf. Oo. 
 
 , 
 
 carnea - 
 
 U. Cretaceous. U. Chalk. 
 
PALAEONTOLOGY. 
 
 165 
 
 Terebratula 
 
 Terebratulina 
 
 Terebrirostra 
 Thecidium 
 
 Uncites 
 
 Actinoceras 
 Ammonites 
 
 - coarctata 
 digona - 
 fimbria - 
 grandis - 
 
 hastata - 
 impressa 
 
 intermedia 
 
 maxillata 
 
 numismalis 
 
 obovata 
 
 ornithocep^ala 
 
 perovalis 
 
 sella 
 
 striata=caput 
 
 serpentis 
 striatula 
 lyra 
 triangulare 
 
 L. Oolite. Gt. Oo. 
 Oolite 
 
 Inf. Oo. 
 Older Pliocene. Wh. and R. 
 
 Crag. 
 
 Carboniferous. 
 L. and M. Oolite. Gt. and 
 
 Cor. Oo. 
 L. Oolite. For. Marb. 
 
 Gt. Oo. 
 
 L. and M. Lias. 
 L. Oolite. For. Marb. 
 L. and M. Oolite. Inf. Gt. 
 
 and Cor. Oo. 
 L. Oolite. Inf. Oo. 
 L. Cretaceous. L. Gr. 
 I U. Cretaceous. U. Chalk, 
 j and still living. 
 L. Eocene. 
 
 U. Cretaceous. U. Gr. 
 U. Lias and L. Oolite to For. 
 
 Marb. 
 
 [. Devonian. 
 
 CEPHALOPODA. 
 
 - giganteum 
 
 - angulatus 
 auritus 
 bifrons 
 biplex 
 
 Braikenridgii 
 Brocchii 
 Brodici 
 Brongniartii 
 Bucklandi 
 Calloviensis 
 capricornis 
 communis 
 complanatus 
 
 cordatus - 
 
 dentatus 
 
 Deshayesii 
 
 Carboniferous. 
 
 L. Lias. 
 
 U. Cretaceous. U. Gr. 
 
 U. Lias. 
 
 U. Oolite. Kim. Clay. 
 
 L. Oolite. Inf. Oo. 
 
 J> 5> 
 
 J> 
 
 T T " " 
 
 L. Lias. 
 
 M. Oolite. Oxf. Clay. 
 
 1VT. Lias. 
 
 U. Lias. 
 
 U. Cretaceous. L. Ch. and 
 
 Marl 
 
 M . Oolite. Oxf. Clay. 
 U. Cretaceous. Gault. 
 L. Cretaceous. Punfield and 
 
 Speeton. 
 
166 
 
 FIELD GEOLOGY. 
 
 Ammonites - 
 
 - discus 
 
 L. Oolite. For. Marb. 
 
 
 excavatus 
 
 M. Oolite. Oxf. Clay. 
 
 
 giganteus 
 
 U. Oolite. Portland. 
 
 
 gracilis - 
 
 L. Oolite. Gt. Oo. 
 
 
 heterophillus - 
 
 U. Lias. 
 
 
 Humphresianu s 
 
 L. Oolite. Inf. Oo. 
 
 
 interruptus 
 
 U. Cretaceous. Gault. 
 
 
 Jason 
 
 M. Oolite. Oxf. Clay. 
 
 
 Lamberti 
 
 57 J 
 
 
 lautus 
 
 U. Cretaceous. Gault. 
 
 
 macrocephalus- 
 
 L. and M. Oolite. 6ft. Oo. and 
 
 
 
 Oxf. Clay. 
 
 
 margaritatus - 
 
 M. Lias. 
 
 
 Martini - 
 
 L. Cretaceous. L. Gr. 
 
 
 m sublivL^ 
 
 i M. Oolite. Oxf. Clay. 
 
 
 Murchisonse - 
 
 L. Oolite. Inf. Oo. 
 
 
 Noricus - 
 
 L. Cretaceous. Speeton Clay. 
 
 
 obtusis - 
 
 L. Lias. 
 
 
 Parkinsoni 
 
 L. Oolite. Inf. Oo. 
 
 
 perarmatus 
 
 M. Oolite. Cor. Oo. 
 
 
 planorbis 
 
 L. Lias. 
 
 
 Ehotomagensis 
 (characteristic) 
 
 [ TJ. Cretaceous. Ch. Marl. 
 
 
 rostratus 
 
 17. Gr. 
 
 
 rotundus 
 
 U. Oolite. Kim. Clay. 
 
 
 serpentinus 
 
 U. Lias. 
 
 
 spinatus 
 
 M. Lias. 
 
 
 splendens 
 
 U. Cretaceous. Gault. 
 
 
 triplicatus 
 
 M. Oolite. Kim. Clay. 
 
 
 varians - 
 
 U. Cretaceous. L. Ch. & Marl. 
 
 
 varicosus 
 
 U. Cretaceous. Gault. 
 
 
 vertebralis 
 
 M. Oolite. Cor. Oo. 
 
 Ancyloceras= 
 
 
 
 Crioceras= 
 
 
 
 Scaphites 
 
 - Calloviense 
 
 M. Oolite. Oxf. Clay. 
 
 
 Duvallei 
 
 L. Cretaceous. L. M. and U. 
 
 
 
 Neo. 
 
 
 equalis - 
 
 U. Cretaceous. L. Chalk and 
 
 
 
 Marl. 
 
 
 gigas 
 
 L. Cretaceous. L. Gr. 
 
 
 spinigerum 
 
 U. Cretaceous. Gault. 
 
 Ascoceras - 
 
 - Barrandii 
 
 U. Silurian. Ludlow. 
 
 Baculites (never in 
 rocks newer than 
 Cretaceous} - anceps 
 
 - U. Cretaceous. L. Chalk. 
 
PALEONTOLOGY. 167 
 
 Belemuitella 
 
 mucronata 
 
 U. Cretaceous. U. Chalk. 
 
 
 plena 
 
 L. Chalk. 
 
 Belemnites 
 
 abbreviatus - 
 
 M. Oolite. Cor. 0. 
 
 
 dilatatus 
 
 L. Cretaceous. L. Gr. 
 
 
 ellipticus 
 
 L. Oolite. Inf. Oo. 
 
 
 elongatus 
 
 M. Lias. 
 
 
 
 fusiformis 
 
 L. Oolite. Gt. Oo. 
 
 
 hastatus 
 
 M. Oolite. Oxf.Clay. 
 
 
 
 minimus 
 
 U. Cretaceous. Gault. 
 
 
 Puzosianus 
 
 M. Oolite. Oxf. Clay. 
 
 
 tubularis 
 
 U. Lias. 
 
 
 Waterhousei - 
 
 L. Oolite. Gt. Oo. 
 
 Beloptera - 
 
 belemnitoidea - 
 
 M. Eocene. 
 
 Belosepia 
 
 sepioidea 
 
 L. Eocene. 
 
 Clymenia 
 
 linearis - 
 
 U. Devonian. 
 
 
 Isevigata - 
 
 M. and U. Devonian. 
 
 
 striata 
 
 U. Devonian. 
 
 
 undulata- 
 
 j> 
 
 Cyrtoceras - 
 
 approximatum- 
 Gesneri - 
 
 Silurian. U. Llandovery. 
 Carboniferous. 
 
 
 tredecimale 
 
 M. Devonian. 
 
 
 Vernuillianum 
 
 Carboniferous. 
 
 Geoteuthis - 
 
 sp. 
 Boltensis 
 
 L. Silurian. Llandeilo flays. 
 Lias. 
 
 Goniatites 
 
 crenistria 
 
 Carboniferous. 
 
 
 Listeri - 
 
 )j 
 
 
 sphsericus 
 
 jj 
 
 
 subsulcatus 
 
 U. Devonian. 
 
 Gyroceras - 
 
 sp. 
 
 M. Devonian. 
 
 Hamites (never in 
 
 
 
 rocks newer than 
 
 
 
 Cretaceous) 
 
 attenuatus 
 
 U. Cretaceous. Gault. 
 
 
 rotundus 
 
 99 99 
 
 
 simplex - 
 
 L. Chalk. 
 
 
 spiniger=An- 
 
 \ 
 
 
 cyloceras 
 
 } Gault. 
 
 
 spinigerum - 
 
 ) 
 
 Lituites=Tro- 
 
 
 
 choceras - 
 
 articulatus 
 
 U. Silurian. Ludlow. 
 
 
 giganteus 
 
 Wenlock and 
 
 
 
 Ludlow. 
 
 
 Hibernicus 
 
 L. Silurian. Bala. 
 
 
 undosus 
 
 Silurian. U. Llandovery. 
 
 Nautilus 
 
 Baberi - 
 
 L. Oolite. Gt. Oo. 
 
 
 b Sjr- 
 
 > Carboniferous. 
 
168 
 
 FIELD GEOLOGY. 
 
 Nautilus 
 
 - Bowerbanki- 
 
 ) 
 
 
 anus (cha- 
 
 > M. Permian. Mag. L. 
 
 
 racteristic} - 
 
 \ 
 
 
 centralis 
 
 L. Eocene. 
 
 
 elegans - 
 
 U. Cretaceous. L. Chalk. 
 
 
 Frieslebeni 
 (characteristic) 
 
 > M. Permian. Mag. L. 
 
 
 hexagonus 
 
 M. Oolite. Oxf. Clay. 
 
 
 imperialis 
 
 L. Eocene. 
 
 
 plica tus 
 
 L. Cretaceous. U. Neo. 
 
 
 sinuatus 
 
 L. Oolite. Inf. Oo. 
 
 
 truncatus 
 
 L. Lias. 
 
 
 zic-zac 
 
 L. Eocene. 
 
 Orthoceras - 
 
 - annulatum 
 
 Silurian. Bala to Wenlock. 
 
 
 Avelinii 
 
 L. Silurian. Llandeilo flags- 
 
 
 Barrandii 
 
 U. Llandovery. 
 
 
 bullatum 
 
 U. Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 duplex 
 
 L. Silurian. Llandeilo flags. 
 
 
 laterale 
 
 Carboniferous. 
 
 
 Ludense 
 
 U. Silurian. Ludlow. 
 
 
 Maclareni 
 
 Wenlock. 
 
 
 Steinhaueri 
 
 Carboniferous. 
 
 I 
 
 tenuicinctum - 
 
 L. Silurian. 
 
 
 vagans 
 sp. 
 
 Bala. 
 Cambrian. Tremadoe. 
 
 
 sp. 
 
 M. Devonian. 
 
 Pbragmoceras 
 
 - ventricosus, 
 and 5 other 
 
 !TJ. Silurian. Wenlock and 
 Ludlow. 
 
 
 species 
 
 
 Poterioceras 
 
 - approximatum 
 
 L. Silurian. Bala. 
 
 
 fusiforme 
 
 Carboniferous. 
 
 Tretoceras 
 
 - bisiphonatum - 
 
 Silurian. U. Llandovery. 
 
 Trigonellites 
 Turrilites - 
 
 - latus 
 - costatus - 
 
 U. Oolite. ^?7i. Clay. 
 U. Cretaceous. L. Chalk. 
 
 CEUSTACEA. 
 
 Acidaspis 
 
 - Barrandii 
 
 U. Silurian. Wenlock. 
 
 
 callipareos 
 
 Silurian. U. Llandovery. 
 
 
 core-Data 
 
 U. Silurian. Ludlow. 
 
 V 
 
 Jamesii 
 
 L. Silurian. Bala. 
 
 JEglina 
 
 mirabilis 
 
 Bala. 
 
PALEONTOLOGY. 169 
 
 Agnostus 
 
 - princeps - 
 
 Cambrian. Lingula flags. 
 
 
 trinodus 
 
 L. Silurian. Bala. 
 
 Ampyx 
 
 - nudus 
 
 L. Silurian. Llandeilo flags. 
 
 
 parvulus 
 
 U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 Angelina 
 
 - sp. 
 
 U. Cambrian. Tremadoe. 
 
 Anoplenus - 
 Archaeoniscus 
 
 -sp. 
 - Edwardsii 
 
 L. Cambrian. Menevian. 
 U. Oolite. Purbeck. 
 
 Asaphus 
 
 - lat^costatus 
 
 L. Silurian. Llandeilo flags.^ 
 
 
 Powisii 
 
 Llandeilo and 
 
 
 
 Bala. 
 
 
 tyrannus 
 
 L. Silurian. Llandeilo. 
 
 Astacoderma 
 
 - 9 species 
 
 U. Silurian. Downton. 
 
 Balanus 
 
 - baJanoides 
 
 Post-Pliocene. 
 
 
 crenatus 
 
 
 
 porchatus 
 
 
 Beliiiurus 
 
 - Eegina - 
 
 Carboniferous. 
 
 
 rotundatus 
 
 
 
 
 trilobitoides 
 
 
 Beyrichia 
 
 - complicata 
 
 L. Silurian. Llandeilo and 
 
 
 
 Bala. 
 
 
 Kloedeni 
 
 Silurian. Bala to Downton. 
 
 
 siliqua - 
 
 U. Silurian. Ludlow. 
 
 Brachymetopus= 
 Phillipsia 
 
 - Ouralicus 
 
 Carboniferous. 
 
 
 pustulata 
 
 
 Bronteus 
 Calymene 
 
 - flabellifer 
 (characteristic) 
 . Blumenbachii - 
 
 ? M. Devonian. 
 Silurian. Bala to Ludlow. "" 
 
 
 brevicapitata - 
 
 L. Silurian. Llandeilo and" 
 
 
 
 Bala. 
 
 
 parvifrons 
 
 L. Silurian. Llandeilo. 
 
 Ceratiocaris 
 
 - Murchisonii, 
 
 \ 
 
 
 and 10 other 
 
 > U. Silurian. Ludloiu. 
 
 
 species 
 
 i 
 
 Cheirurus - 
 
 - clavifrons 
 
 L. Silurian. Bala. 
 
 Conocoryphe 
 
 - depressa 
 in vita 
 
 Cambrian. Lingula flags. 
 
 Cyphaspis - 
 
 - pygmaeus 
 
 U. Silurian. Wenlock. 
 
 Cypridea=Cypris 
 
 fasiculata 
 
 U. Oolite. M. Purbeck. 
 
 
 gibbosa 
 
 U. Purbeck. 
 
 
 granulata 
 
 M. Purbeck. 
 
 
 leguminella - 
 
 U. Purbeck. 
 
 
 punctata 
 
 L. Purbeck. 
 
 
 Purbeckensis - 
 
 
 
 spinigera 
 
 L. Cretaceous. Wealden. 
 
170 
 
 FIELD GEOLOGY. 
 
 Cypridea 
 
 - striata-pimc- 
 tata 
 
 1 U. Oolite. M. Purbeck. 
 
 
 tuberculata 
 
 U. Purbeck. 
 
 
 Valdensis 
 
 - L. Cretaceous. Wealden. 
 
 
 sp. 
 
 - U. Eocene. 
 
 
 sp. 
 
 - L. Miocene. 
 
 Cypridina 
 
 - serrato-striata 
 
 - U. Devonian. 
 
 Cythere 
 
 - inflata - 
 
 - Carboniferous. 
 
 Dikelocephalus 
 Dithyocaris 
 
 -sp. 
 - Colei - 
 
 - U. Cambrian. Tremadore. 
 - Carboniferous. 
 
 Encrinurus 
 
 - punctatus 
 
 - Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 variolaris 
 
 - U. Silurian. Wenlock. 
 
 Errinnys 
 
 - venulosa 
 
 - L. Cambrian. Menevian. 
 
 Eryon 
 
 - antiquns 
 
 - Lias. 
 
 
 Barrovensis 
 
 _ 
 
 Estheria 
 
 - elliptica 
 
 - L. Cretaceous. Wealden. 
 
 
 minuta (cha- 
 
 ) Trias. ? Keuper and 
 
 
 racteristic) 
 
 $ Penarth. 
 
 
 sp. 
 
 - M. Old Eed. 
 
 Eurypterus - 
 
 sp. 
 - abbreviatus, 
 and 6 other 
 species 
 
 - L. Oolite. Inf. Oo. 
 j-U. Silurian. Ludlow. 
 
 
 linearis - 
 
 Ludlow & Doionton. 
 
 
 megalops, pe- 
 culiar to 
 
 _ } 
 
 > U. Silurian. Downton. 
 
 
 pygmseus 
 
 Ludlow and 
 
 
 
 Downton. 
 
 
 sp. 
 
 - L. Old Eed. 
 
 dyphcea 
 
 - Liassica - 
 
 - Lias. 
 
 
 rostrata - 
 
 - L. and M. Oolite. Gt.Oo.and 
 
 
 
 Cor. Oo. 
 
 
 scabrosa 
 
 - M. Oolite. Cor. Oo. 
 
 Griffithides - 
 
 - globiceps 
 
 - Carboniferous. 
 
 Harpes 
 
 - Flanagan! 
 
 - L. Silurian. Bala. 
 
 Homalonotus 
 
 - arcuatus ) T TA 
 (characteristic) ^.Devonian. 
 
 
 bisulcatus 
 
 - Silurian. Bala and Llan- 
 
 
 
 dovery. 
 
 
 delphinoce- 
 phalus 
 Herschellii 
 
 \ U. Silurian. Wenlock. 
 - L. Devonian. 
 
 
 Knightii 
 
 - U. Silurian. Ludlow. 
 
 
 Ludensis 
 
 
 
 Hoploparia - 
 
 - Belli! - 
 
 - L. Eocene. 
 
PALAEONTOLOGY. 171 
 
 Hymenocaris 
 
 - vermicauda 
 (characteristic) 
 
 ) U. Cambrian. Lingula 
 
 > flags- 
 
 Ilisenus 
 
 - Barriensis 
 
 Silurian. Llandovery and 
 
 
 
 Wenlock. 
 
 
 Bowmanni 
 
 Silurian. Llandeilo^ Bala, 
 
 
 
 and Llandovery. 
 
 
 Davisii - 
 
 L. Silurian. Bala. 
 
 
 perovalis 
 
 Llandeilo. 
 
 Leperdita 
 
 -sp. 
 
 U. Silurian. Ludlow and 
 
 
 
 Downton. 
 
 Lichas 
 
 - Anglicus 
 
 U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 Hibernicns 
 
 L. Silurian. Bala. 
 
 
 
 laxatus - 
 
 Silurian. Bala, and Llan- 
 
 
 
 dovery. 
 
 Megacheirus 
 
 - Pearcei - 
 
 M. Oolite. Oxf. Clay. 
 
 Meyeria 
 
 - Vectensis 
 
 L. Cretaceous. L. Gr. 
 
 Microdiscus 
 
 - sp. 
 
 L. Cambrian. Menevian. 
 
 Notopocorystes 
 
 - Beachei 
 
 U. Cretaceous. Gault. 
 
 Ogygia 
 
 Stokesii - 
 - Buchii - 
 
 L. Silurian. Llandeilo. 
 
 
 ^ e ^actelist^c)~- 
 
 t L. Silurian. Stiper-Stones. 
 
 Olenus 
 
 - alatus 
 
 U. Cambrian. Lingula flags. 
 
 
 micrurus 
 
 ?> 
 
 Paradoxides 
 
 - Davidis, pe- 
 culiar to 
 
 > L. Cambrian. Menevian. 
 
 
 Hicksii - 
 
 U. Cambrian. Lingula flags. 
 
 Phacops 
 
 - apiculatus 
 
 L. Silurian. Llandeilo and 
 
 
 
 Bala. 
 
 
 caudatus 
 
 Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 Downingise 
 
 U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 longicaudatus - 
 
 U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 Stokesii - 
 
 Silurian. L. and U. Llan- 
 
 
 
 dovery. 
 
 Plutonia 
 Pollicipes 
 
 - Sedgwickii 
 - concinnus 
 
 L. Cambrian. Longmynd. 
 M. Oolite. Oxf. Clay. 
 
 Proetus 
 
 - latifrons 
 
 Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 Pterygotus - 
 
 - eggs of= 
 
 \ 
 
 
 Parka de- 
 
 [ U. Silurian and L. Old Eed. 
 
 
 cipiens 
 
 ) 
 
 
 Auglicus 
 
 L. Old Eed. 
 
172 
 
 FIELD GEOLOGY. 
 
 
 Pterygotus - 
 
 - Banksii - - U. Silurian. 
 
 Downton. 
 
 
 bilobus - 
 
 Ludlow. 
 
 Eemopleurides 
 
 culiar to - j " 
 problematicus ~\ 
 and several 
 other species j 
 - dorso-spinifer - L. Silurian. 
 
 Ludlow. 
 Bala. 
 
 granulatus - M. and U. Devonian. 
 
 
 iatifrons (cha- } 
 
 
 
 racteristic of > 
 
 jj 
 
 
 Devonian) - ) 
 
 
 
 laciniatus - L. M. and U. 
 
 Devonian. 
 
 Sphcerexochus 
 
 - minis - - Silurian. Bala and Wedlock*. 
 
 Staurocephalus 
 
 - globiceps - L. Silurian. Bala. 
 Murchisonii - Silurian. Bala to WenlocL 
 
 Trinucleus - 
 
 - Caractaci - L. Silurian. 
 
 Bala. 
 
 
 fimbriatus - 
 
 Llandeilo. 
 
 
 Lloydii - 
 
 j 
 
 
 seticornis 
 
 Bala. 
 
 Zanthopsis - 
 
 - tuberculata - L. Eocene. 
 
 
 ECHINODEKMATA. 
 
 Acrosalenia 
 
 Actinocrinus 
 
 Agelacrinus 
 Ananchytes (genus 
 Cre- 
 
 - decorata - 
 hemicidaroides 
 minuta 
 
 - pulcher 
 triacontadac- 
 
 tylus 
 
 - Buchianus 
 
 M. Oolite. 
 L. Oolite, 
 L. Lias. 
 U. Silurian. 
 
 Cor. Oo. 
 for Marb. 
 
 Wenlock. 
 
 j Carboniferous. 
 - L. Silurian. Bala. 
 
 taceous) - 
 
 - ovatus 
 
 - U. Cretaceous. L. and U^ 
 
 
 
 Chalk. 
 
 
 subglobosus 
 
 - U. Cretaceous. L. and U. 
 
 
 
 Chalk. 
 
 Apiocrinus - 
 
 - Parkinsoni= 
 rotundus 
 
 \ L. Oolite. For. Marb. 
 
 Archseocidaris 
 
 - Urii 
 
 - Carboniferous. 
 
 Astropecten 
 
 - crispatus 
 
 - L. Eocene. 
 
 Cardiaster 
 
 - granulosus 
 
 - U. Cretaceous. U. Chalk. 
 
 
 Benstedi 
 
 - L. Cretaceous. L. Gr. 
 
 Catopygus - 
 Cidaris 
 
 - carinatus 
 - coronata 
 
 - U. Cretaceous. U. Gr. 
 - M. Oolite. Cor. Oo. 
 
 
 Edwardsii 
 
 - M. Lias. 
 
PALAEONTOLOGY. 173 
 
 Oidaris 
 
 florigemma 
 
 M. Oolite. Cor. Oo. 
 
 
 perornata 
 
 U. Cretaceous. U. Chalk. 
 
 Codonaster - 
 
 genus pecu- 
 liar to 
 
 [ Carboniferous. 
 
 Collyrites 
 
 ringens 
 
 L. Oolite. Inf. Oo. 
 
 Comatula - 
 
 Brownii 
 
 O. Pliocene. Wh. Crag. 
 
 Crotalocrinus 
 
 rugosus - 
 
 U. Silurian. WenlocL, 
 
 Cupressocrinites - 
 
 sp. 
 
 Devonian. 
 
 Cyathocrinus 
 
 calcaratus 
 
 Carboniferous. 
 
 
 caryocrinoides- 
 
 v 
 
 
 goniodactylus - 
 
 U. Silurian. WenlocL 
 
 
 planus 
 
 Carboniferous. 
 
 Diadema 
 
 Bennettioe 
 
 U. Cretaceous. U. Gr. 
 
 Discoidea - 
 
 cylindrica 
 
 L. Chalk. 
 
 
 subuculus 
 
 U. Gr. 
 
 Echinocyamus 
 Echino-encrinites - 
 
 pusillus - 
 armatus - 
 
 O. Pliocene. Wh. Crag. 
 U. Silurian. WenlocL 
 
 E chino-sphoerites- 
 
 aurantium 
 
 L. Silurian. Eala. 
 
 
 Balticus (cha- 
 racteristic) - 
 
 \ . . 
 
 Echinus 
 
 Drobachiensis - 
 
 Post-Pliocene. 
 
 
 granulosus 
 
 U. Cretaceous. U. Gr. 
 
 
 perlatus - 
 
 L. and M. Oolite. Inf. Gt. 
 
 
 
 and Cor. Oo. 
 
 
 Woodwardii - 
 
 O. Pliocene. Wh. Crag. 
 
 Encrinites - 
 
 sp. 
 
 L. Devonian and Trias. 
 
 Eucalyptocrinus - 
 
 decorus - 
 
 U. Silurian. WenlocL 
 
 Eupatagus - 
 
 Hastingsise 
 
 M. Eocene. 
 
 Extracrinus= 
 
 
 
 (Pentacrinus) - 
 
 Briareus 
 
 L. Lias. 
 
 Galerites 
 Gouiaster 
 
 albo-galerus - 
 Parkinson! 
 
 U. Cretaceous. U. ChalL 
 )) 
 
 
 Stokesii 
 
 L. Eocene. 
 
 Haploaster - 
 
 gracilis 
 
 Post-Pliocene. 
 
 Hemiaster - 
 
 Bailyi 
 
 U. Cretaceous. Gault. 
 
 Hemicidaris 
 
 
 
 (genus Oolitic) - 
 
 Davidsoni 
 
 U. Oolite. Portland. 
 
 
 intermedia 
 
 L. and M. Oolite. Gt. and 
 
 minor 
 
 Purbeckensis 
 Hemicosmites - sp. 
 
 Hemipneustes - Fittoni - 
 
 Marsupiocrinus - coelatus - 
 
 Marsupites - - Milleri - 
 
 ornatus - 
 
 Cor. Oo. 
 
 L. Oolite. Gt. Oo. 
 U. Oolite. PurbecL 
 L. Silurian. Sola. 
 L. Cretaceous. L. Gr. 
 U. Silurian. WenlocL 
 U. Cretaceous. Chalk. 
 
 U. ChalL 
 
174 
 
 FIELD GEOLOGY. 
 
 Micraster 
 
 cor-anguinum- U. Cretaceous. U. Chalk. 
 
 Nucleolites - 
 
 Agassizii - L. Oolite. Inf. Oo. 
 
 
 clunicularis Cornbrash. 
 
 
 dimidiatus = \ L. and M. Oolite. Gt. and 
 sculatus $ Cor. Oo. 
 orbicularis - L. and M. Oolite. Gt. and 
 
 
 Cor. Oo. 
 
 
 sinuatus- - L. and M. Oolite. Gt. and 
 
 
 Cor. Oo. 
 
 Ophioderma 
 
 Egertoni - M. Lias. 
 
 
 tenuibranchi- ) 
 ata f ' 
 
 Ophiura 
 
 Wetherellii - L. Eocene. 
 
 Palaeaster - 
 
 asperrimus - L. Silurian. Bala. 
 
 
 coronella - Silurian. U. Llandovery. 
 
 
 obtusus - - L. Silurian. Bala. 
 
 
 Ruthveni - U. Silurian. Ludlou: 
 
 Palsechinus - 
 
 gigas - - Carboniferous. 
 
 
 sphaericus 
 
 Palseocoma - 
 
 Colvini,and3 1 n Silurian. Ludhw. 
 other species- j 
 
 Pentacrinus {Lias 
 
 
 to London clay)- 
 
 Fittoni - - U. Cretaceous. Gault. 
 
 
 several species Lias. 
 
 Pentremites 
 
 genus peculiar 1 Carbonif erous . 
 to - $ 
 
 
 Derbiensis, ) 
 
 
 &c.,&c. - J 
 
 Periechocrinus - 
 
 moniliformis - Silurian. Llandovery and 
 
 
 Wenlock. 
 
 Platycrinus 
 
 genus charac- 1 Carbon i fer ous. 
 tenstic of - $ 
 
 
 laevis, &c. &c. - 
 
 Pleurocystites 
 
 Rugeri - - Silurian. U. Llandovery. 
 
 Poteriocrinus 
 
 genus charac- | Carboniferous . 
 
 
 tenstic of - ) 
 
 
 granulosus, 7 
 
 
 &c., &c. - j 
 
 Protaster 
 
 Miltoni,and3 | n Si i urian . Ludlow. 
 
 
 other species- f 
 
 
 sp. - L. Silurian. Bala^W 
 
 Pseudocrinites - 
 
 bifasciatus - U. Silurian. Wenlock. 
 
 
 quadrifascia- > 
 
 
 tus - - C " 
 
PALEONTOLOGY. 175 
 
 Pseudodiadema 
 
 - pentagonum - 
 
 L. Oolite. Gt. Oo. 
 
 Pygaster 
 
 - semisulcatus - 
 
 L. and M. Oolite. Gt. and 
 
 
 
 . Cor. Oo. 
 
 Pygurus 
 
 - pentagonalis - 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 Rhodocrinus 
 
 - bursa 
 
 Carboniferous. 
 
 Salenia 
 
 - Austeni - 
 
 U. Cretaceous. L. Chalk. 
 
 
 personata 
 
 U. GT. 
 
 
 punctata 
 
 L. Cretaceous. L. Gr. 
 
 Spatangus - 
 
 - radiatus - 
 
 U. Cretaceous. U. Chalk. 
 
 Sphaeronites = 
 
 
 
 Cystidae - 
 
 - Litchi - 
 
 L. Silurian. Bala. 
 
 Taxocrinus - 
 
 - tesseraconta- 
 dactylus 
 
 \ U. Silurian. WenlocTc. 
 
 
 Orbignyi 
 
 Ludlow. 
 
 Temnechinus 
 
 - excavatus 
 
 O. Pliocene. Wh. and R. 
 
 
 
 Crag. 
 
 Uraster 
 
 - Gaveyi - 
 
 M. Lias. 
 
 GASTEROPODA. 
 
 Achatina 
 
 - costellata 
 
 U. Eocene. 
 
 Acroculia 
 
 - euomphaloides 
 haliotis - 
 
 U. Silurian. Ludlow. 
 Silurian. Llandovery and 
 
 
 
 Wenlock. 
 
 
 sp. 
 
 M. Devonian. 
 
 
 sp. 
 
 Carboniferous. 
 
 Actason 
 
 - affinis - 
 
 U. Cretaceous. U. Gr. 
 
 Alaria 
 
 - atractoides 
 
 L. Oolite. Gt. Oo. 
 
 
 composita 
 
 M. Oolite. Oxf. Claij. 
 
 
 trifida - 
 
 L. and M. Oolite. ' Gt. and 
 
 
 
 Cor. Oo. 
 
 Ancillaria 
 
 - buccinoides 
 
 M. Eocene. 
 
 Aporrhais - 
 
 - Sowerbyi 
 
 L. Eocene. 
 
 Avellana 
 
 - cassis 
 
 U. Cretaceous. L. Chalk. 
 
 Buccinum - 
 
 - GrEenlandicum 
 
 Post-Pliocene. 
 
 
 sp. 
 
 L. Oolite. Gt. Oo. 
 
 Bulimus 
 
 - ellipticus 
 
 U. Eocene. 
 
 Bulla - 
 
 - elongata 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 Bullsea 
 
 - sculpta - 
 
 O. Pliocene. Wh. Crag. 
 
 Cancellaria - 
 
 - evulsa 
 
 M. Eocene. 
 
 
 muricata 
 
 U. Eocene. 
 
 
 sp. 
 
 L. Eocene. 
 
 Cassidaria - 
 
 - bicatenata 
 
 O. Pliocene. Wh. Crag. 
 
 
 Smithii - 
 
 L. Eocene. 
 
176 
 
 FIELD GEOLOGY. 
 
 Cerithium - 
 
 - carbonarium - 
 
 L. Cretaceous. Wealden. 
 
 
 elegans - 
 
 U. Eocene and L. Miocene. 
 
 
 funatum 
 
 L. Eocene. 
 
 
 giganteum 
 
 M. Eocene. 
 
 
 muricatum 
 
 M. Oolite. Cor. Oo. 
 
 
 mutabile 
 
 U. Eocene. 
 
 
 plicatum 
 
 U. Eocene and L. Miocene. 
 
 
 Portlandicum - 
 
 U. Oolite. Portland. 
 
 
 tricinctum 
 
 L. Miocene. 
 
 Chemnitzia-=- 
 
 
 
 Phasianella 
 
 - gigantea 
 
 U. Oolite. Kim. Clay. 
 
 
 lineata - 
 
 L. Oolite. Inf. Oo. 
 
 
 Heddington- 
 ensis - 
 
 i M. Oolite. Cor. Oo. 
 
 
 striata - 
 
 M ?? 
 
 
 vittata - 
 
 L. Oolite. For. Marl. 
 
 Chiton 
 
 - Grayanus 
 
 U. Silurian. Wenlock. 
 
 
 Griffith!! 
 
 Silurian. U. Llandovery. 
 
 Columella - 
 
 - sulcata - 
 
 O. Pliocene. R. Crag. 
 
 Conovulus - 
 
 - pyramidalis - 
 
 N". Pliocene. 
 
 Conus 
 
 - deperditus 
 
 M. Eocene. 
 
 
 dormitor 
 
 jy 
 
 
 sp. 
 
 L. Eocene. 
 
 Cyclonema - 
 
 - quadristriata - 
 
 Silurian. U. Llandovery. 
 
 
 rupestris 
 
 L. Silurian. Bala. 
 
 Cylindrites - 
 
 - acutus 
 
 L. Oolite. Gt. Oo. 
 
 Cypraea 
 
 - Europaea 
 
 O. Pliocene. R. Crag. 
 
 
 lucida 
 
 N. Pliocene. 
 
 
 oviformis 
 
 L. Eocene. 
 
 Dentalium - 
 
 - ellipticum 
 striatum 
 
 U. Cretaceous. Gault. 
 M. Eocene. 
 
 Euomphalus 
 
 - annulatus 
 
 M. Devonian. 
 
 
 carinatus 
 
 U. Silurian. Wenlock. 
 
 
 Corndensis 
 
 L. Silurian. Llandeilo. 
 
 
 discors - 
 
 U. Silurian. Wenlock. 
 
 
 funatus - 
 
 Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 pentangulatus 
 
 -) 
 
 
 (characteris- 
 
 > Carboniferous. 
 
 
 tic) 
 
 j 
 
 
 Permianus 
 
 
 
 (characteris- 
 
 > M. Devonian. Mag. L. 
 
 
 tic) 
 
 J 
 
 
 prsenuntius 
 
 Silurian. U. Llandovery. 
 
 
 rugosus - 
 
 U. Silurian. Wenlock. 
 
PALEONTOLOGY'. 177 
 
 Fusus 
 
 - antiquus - O. 1ST. and Post-Pliocene. 
 
 
 contrarius= ^ 
 
 
 Trophon V O. Pliocene. 7?. Crag. 
 
 
 antiquum - J 
 
 
 labiatus - - U. Eocene. 
 
 
 longevus - M. Eocene. 
 
 
 striatus - U. Pliocene. N. Crag. 
 
 Helix 
 
 - D'Urbani - U. Eocene. 
 
 
 labyrinthica - U. Eocene. 
 
 
 nemoralis - Post-Pliocene. 
 
 
 occlusa - - U. Eocene. 
 
 Holopcea - 
 
 - concinna - L. Silurian. Bala. 
 
 
 corallii - - U. Silurian. Ludlow. 
 
 Holopella - 
 
 - cancellata - U. Silurian. Bala to Lud- 
 
 
 loiv. 
 
 
 plana - - U. Silurian. U. Llandovery. 
 
 
 tenuicincta - 
 
 Hydrobia - 
 Littorina - 
 
 - Chastellii - U. Eocene. 
 - littorea - - N. and Post-Pliocene. 
 
 
 rudis - - Post-Pliocene. 
 
 Loxonema - 
 
 - fasciatum 1 M. Permian. Mag. L. 
 
 
 Lefebvrei - Carboniferous. 
 
 JLymnea 
 
 - caudata - - U. Eocene. 
 
 
 longiscata - M. Eocene. 
 
 
 sp. - L. Miocene. Hempstead. 
 
 
 sp. - - U. Oolite. Purbeck. 
 
 Macrocheilus 
 
 - f usifonnis - Silurian. U. Llandovery. 
 
 
 ovalis - - Carboniferous. 
 
 
 pusillus - 
 
 
 symmetricus ~) 
 (characteris- >M. Permian. Mag. L. 
 tic) J 
 sp. M. Devonian. 
 
 Melania 
 
 - costata - - L. Miocene. Hempstead. 
 
 
 fasciata - - ,, 
 
 
 inquinata - L. Eocene. 
 
 
 muricata M. Eocene. 
 
 
 turritissima - U. Eocene. 
 
 
 sp. - - U. Oolite. P-urbecl;. 
 
 
 sp. - - L. Cretaceous. Wealden. 
 
 Melanopsis - 
 
 - harpjEformis - U. Oolite. Purbeclc. 
 
 
 sub-fusiformis M. Eocene. 
 
 
 tricarinata - L. Cretaceous. Wealden. 
 
 
 carinata - - L. Miocene. Hempstead. 
 
 Mitra 
 
 > scabra - - M. and U. Eocene. 
 
 
 12 
 
178 
 
 FIELD GEOLOGY. 
 
 Murchisonia 
 
 - angulata 
 
 U. Devonian. 
 
 
 articulata 
 
 Silurian. Llandovery and 
 
 
 
 Ludlow. 
 
 
 Lloydii - - 
 
 U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 simplex 
 
 Silurian. Bala and L* 
 
 
 
 Llandovery. 
 
 
 spinosa 
 
 Devonian. 
 
 
 sp. 
 
 Carboniferous. 
 
 Mtirex 
 
 - asper 
 
 M. Eocene. 
 
 Nassa 
 
 - monensis 
 
 N. Pliocene. 
 
 
 reticosa 
 
 O. Pliocene. 7?. Crag. 
 
 Natica 
 
 ~ affinis 
 
 Post-Pliocene. 
 
 
 ambulacrum - 
 
 M. Eocene. 
 
 
 clausa 
 
 Post-Pliocene. 
 
 
 elegans - 
 
 U. Oolite. Portland.* 
 
 
 elliptica - 
 
 Carboniferous. 
 
 
 Gaultina 
 
 U. Cretaceous. Gcvult* 
 
 
 Gentii 
 
 U.Gr. 
 
 
 helicoides 
 
 N. Pliocene. 
 
 
 hemiclausa 
 
 (). Pliocene. P. Cray. 
 
 
 Leibnitziana 
 (characteristic) 
 
 > M. Permian. Mag. L.. 
 
 
 parva 
 
 U. Silurian. Ludlow. 
 
 Nerinea 
 
 - Goodhallii 
 
 M. Oolite. Cor. Oo. 
 
 
 hieroglyphica - 
 
 5' 91 
 
 
 Voltzii 
 
 L. Oolite. Gt. Oo. 
 
 Nerita 
 
 - costulata 
 
 L. Oolite. Gt. Oo. 
 
 Neritina 
 
 - concava 
 
 U. Eocene. 
 
 
 Fittoni - 
 
 L Cretaceous. Wealden. 
 
 Neritoma 
 
 " sinuosa - 
 
 U. Oolite. Portland. 
 
 Oliva 
 
 - Branderi 
 
 M. Eocene. 
 
 Ophileta 
 
 - compacta 
 
 L. Silurian. Llandeilo. 
 
 Paludina 
 
 - carinifera 
 
 U. Oolite. PurbecL 
 
 
 fluviorum 
 
 L. Cretaceous. Wealden. 
 
 
 lenta 
 
 U. Eocene, L. Miocene, and 
 
 
 
 N. Pliocene. 
 
 
 orbicularis 
 
 U. Eocene. 
 
 
 Sussexensis 
 
 L. Cretaceous. Weald fn. 
 
 Patella 
 
 - latissima 
 
 U. Oolite. Kim. Clay. 
 
 
 nracronata 
 
 Carboniferous. 
 
 
 rugosa - 
 
 L. Oolite. Gt. Oo. 
 
 
 sp. 
 
 O. Pliocene. Wh. Crag. 
 
 Phorus 
 
 - agglutinans 
 
 M. Eocene. 
 
 
 canal iculatus - 
 
 U. Cretaceous. L. Chalk. 
 
 
 extensus 
 
 L. Eocene. 
 
PALEONTOLOGY. 179 
 
 Physa 
 
 - Bristovii 
 
 - U. Oolite- Purbeck. 
 
 Planorbis 
 
 - discus 
 
 - U. Eocene. 
 
 
 euomphalus 
 
 - M. Eocene. 
 
 
 lens 
 
 - L. Miocene. Hempstead. 
 
 
 obtustis - 
 
 - U. Eocene. 
 
 Platyschisma 
 
 - helicites 
 
 - U. Silurian. Ludlow and 
 
 
 
 Downton. 
 
 Pleurotoma 
 
 - attenuata 
 
 - M. Eocene. 
 
 
 plebeia - 
 
 - U. Eocene. 
 
 Pleurotomaria 
 
 - Anglica - 
 
 - L. and M. Lias. 
 
 
 antrina (cha- 
 racteristic} 
 
 > M. Permian. Mag. L. 
 
 
 aspera - 
 
 - M. and U. Devonian. 
 
 
 carinata - 
 
 - Carboniferous. 
 
 
 elongata - 
 
 - L. Oolite. Inf. Oo. 
 
 
 fissicarina 
 
 - Silurian. U. Llandovery. 
 
 
 gigantea 
 
 - L. Cretaceous. L. Gr. 
 
 
 granulata 
 
 - L. and M. Oolite. Inf. Gt.. 
 
 
 
 and Cor. Oo. 
 
 
 ornata - 
 
 - L. Oolite. Inf. Oo. 
 
 
 pallium - 
 
 '> j> 
 
 
 perspectiva 
 
 - U. Cretaceous. U. Chalk. 
 
 
 reticulata 
 
 - U. Oolite. Kim. Clay. 
 
 
 Khodani 
 
 - U. Cretaceous. Gault andr 
 
 
 
 U. Gr. 
 
 
 rugata - 
 
 - U. Oolite. Portland. 
 
 
 undata - 
 
 - U. Silurian. Ludlow. 
 
 Potamides - 
 
 - concavus 
 
 - M. Eocene. 
 
 
 cinctus - 
 
 - U. Eocene. 
 
 Pteroceas 
 
 - Fittoni - 
 
 - L. Cretaceous. L. Gr. 
 
 Pupa - 
 
 - muscorum 
 
 - Post-Pliocene. 
 
 Purpura 
 Purpurina - 
 
 - tetragona 
 - nodulata 
 
 - O. Pliocene. R. Crag. 
 - L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 Purpuroidea 
 
 - Morrissii 
 
 - L. Oolite. Gt. Oo. 
 
 Pyrula 
 
 - reticulata 
 
 - O. Pliocene. Wh. Crag. 
 
 
 Smithii - 
 
 - L. Eocene. 
 
 Eaphistoma 
 
 - equale 
 
 - L. Silurian. Eala. 
 
 
 lenticularis 
 
 U. Llandovery. 
 
 Kimula=Emargi- 
 
 nula - - clathrata 
 Eissoa - - Chastellii 
 
 Rostellaria 
 
 parva 
 - ampla 
 
 L. Oolite. Gt. Oo. 
 
 U. Eocene and L. Miocene. 
 
 Post- Pliocene. 
 
 L. and U. Eocene. 
 
 122 
 
180 
 
 FIELD GEOLOGY. 
 
 Kostellaria - 
 
 - carinata - 
 
 - U. Cretaceous. Gault. 
 
 
 Parkiusoni 
 
 - U. Cretaceous. Gault and 
 
 
 
 Blackdown. 
 
 
 rimosa - 
 
 - M. Eocene. 
 
 Scalaria 
 
 - Bowerbankii 
 
 - L. Eocene. 
 
 
 Gaultina 
 
 - U. Cretaceous. Gault. 
 
 
 Graenlandica 
 
 - O. N. and Post-Pliocene 
 
 
 
 (living). 
 
 Solarium 
 
 - conoidenm 
 
 - U. Cretaceous. Gault. 
 
 
 canaliculatum 
 
 . M. Eocene. 
 
 
 ornatum 
 
 - U. Cretaceous. Gault and 
 
 
 
 U. Gr. 
 
 Strombus - 
 
 - Bartonensis 
 
 . M. Eocene. 
 
 Succinea 
 
 - elongata 
 
 - Post-Pliocene. 
 
 Terebelluin - 
 
 - fusiform e 
 
 - M. and U. Eocene. 
 
 
 sopita 
 
 - U. Eocene. 
 
 Tritonium 
 
 - carinatum 
 
 - N. Pliocene. 
 
 Trochella - 
 
 - prisca 
 
 - Carboniferous. 
 
 Trochee ema 
 
 - tricincta - 
 
 . Silurian. U. Llandovery. 
 
 Trochotoma 
 
 - annuloides 
 
 . L. Oolite. Gt. Oo. 
 
 Trochus 
 
 - monilifer 
 
 - M. Eocene. 
 
 Trophon 
 
 - antiquum= 
 Fusus con- 
 
 }O. Pliocene. R. Crag. 
 
 
 trarius- 
 
 
 
 clathratum 
 
 . Post-Pliocene. 
 
 
 subnodosum 
 
 _ L. Eocene. 
 
 Turritella - 
 
 - communis 
 
 _ N. Pliocene. JV. Crag. 
 
 
 concava 
 
 - U. Oolite. Portland. 
 
 
 granulata 
 incrassata 
 
 . U. Cretaceous. U. Gr. 
 - N. Pliocene. 
 
 
 imbiicataria 
 
 _ M. Eocene. 
 
 Typhis 
 Valvata 
 
 - pungens - 
 - sp. 
 
 _ M. and U. Eocene. 
 _ U. Oolite. Purbeck. 
 
 Vicarya 
 
 - Lujani - 
 
 _ L. Cretaceous. PunfiehL 
 
 Yoluta 
 
 - ambigua - 
 
 _ U. Eocene. 
 
 
 athleta - 
 
 _ M. and U. Eocene. 
 
 
 Lamberti 
 
 . O. Pliocene. Wh. and 7?. 
 
 
 
 Crag. 
 
 
 luctatrix - 
 
 _ M. Eocene. 
 
 
 nodosa - 
 
 _ L. Eocene. 
 
 
 Eathieri 
 
 _ L. Miocene. 
 
 
 scabricula 
 
 _ M. Eocene. 
 
 
 Selseiensis 
 
 
 
 
 Wetherellii 
 
 - L. Eocene. 
 
PALEONTOLOGY. 
 
 181 
 
 HETEROPODA = NUCLEOBRANCHIATA. 
 
 Bellerophon (Ge- 
 nus occurs only 
 up to Carbo- 
 niferous) - - acutus - 
 bilobatus 
 bisulcatus 
 costatus - 
 dilatatus 
 expansus 
 
 hiulcus - 
 nodosus - 
 subglobatus 
 tangentialis 
 trilobatus 
 
 Wenlockensis 
 sp. 
 
 Maclurea 
 Porcellia 
 
 Logani - 
 Peach ii - 
 Puzio 
 
 - L. Silurian. Llandeilo. 
 
 ?> 
 
 - L. M. and U. Devonian. 
 
 - Carboniferous. 
 
 - Silurian. Bala to Wenlock. 
 
 - Silurian. Llandovery and 
 
 Ludlow. 
 
 - Carboniferous. 
 
 - L. Silurian. Bala. 
 
 - M. and U. Devonian. 
 
 - Carboniferous. 
 
 - U. Silurian. Ludlow and 
 
 Downton. 
 U. Silurian. Wenlock. 
 
 - U. Cambrian. 2'remadoc. 
 
 slates. 
 
 - L. Silurian. Llandeilo. 
 
 >7 
 
 - Carboniferous. 
 
 HYDROZOA. 
 
 Didymograpsus 
 
 Diplograpsus 
 
 Graptolithus 
 
 Kastrites 
 
 - caduceus 
 geminus 
 Murchisonii 
 
 - bullatus 
 folium - 
 pristis 
 
 - Conybeari 
 Flemingii, and 
 
 4 other species 
 Hisingeri= 
 
 sagittariius - 
 priodon - 
 
 - peregrinus 
 
 - L. Silurian. Bala. 
 
 titiper-Stones. 
 
 Llandeilo. 
 
 L. Silurian. Bala. 
 
 Llandeilo. 
 
 L. Silurian. Bala. 
 1 U. Silurian. Wenlock. 
 
 j- L. Silurian. Llandeilo. 
 
 Silurian. Bala to Ludlow. 
 L. Silurian. Llandeilo and 
 Bala. 
 
182 
 
 FIELD GEOLOGY. 
 
 INSECTA. 
 
 Bupreston - 
 Oarabus 
 
 Corydalis 
 
 Elater 
 
 Ephemera 
 
 Gryllus 
 
 Hemerobius 
 
 Libullela 
 
 - perarapla 
 
 - stygnus 
 
 - elongatus 
 sp. 
 
 -sp. 
 -sp. 
 -sp. 
 -sp. 
 -sp. 
 
 - Hopei 
 
 U. Oolite. PurbecL 
 
 U. Oolite. Purbeck. 
 
 U. Oolite. Purbeck. 
 
 Lias. 
 
 Carboniferous. 
 
 Lias. 
 
 Lias. 
 
 Lias. 
 
 Lias. 
 
 Lias. 
 
 LAMELLIBKANCHIATA=CONCHIFERA. 
 
 Anatina 
 
 Anodonta - 
 Anodontopsis 
 Area - 
 
 Artemis 
 Astarte 
 
 Avicula 
 
 undata - 
 
 L. and M. Oolite. Gt. and 
 
 
 Cor. Oo. 
 
 undulata 
 
 M. Oolite. Oxf. Clay. 
 
 Jukesii - 
 
 U. Old Red. 
 
 several species- 
 
 U. Silurian. Ludlow. 
 
 semula - 
 
 L. and M. Oolite. Gt. and 
 
 
 Cor. Oo. 
 
 Branderi 
 
 M. Eocene. 
 
 carinata 
 
 U. Cretaceous. U. Gr. 
 
 Hirsonensis 
 
 L. Oolite. Gt. Oo. 
 
 sp. 
 
 M. Permian. Mag. L. 
 
 lentiformis 
 
 O. Pliocene, li. Crag. 
 
 Beanmoutii - 
 
 L. Cretaceous. L. Gr. 
 
 borealis= 
 
 [ N. and Post-Pliocene. 
 
 compressa - 
 
 } 
 
 cuneata 
 
 U. Oolite. Portland. 
 
 elegans 
 
 L. Oolite. Inf. Oo. 
 
 Hartwelliensis 
 
 U. Oolite. Kim. Clay. 
 
 lurida 
 
 M. Oolite. Oxf. Clay. 
 
 mutabilis 
 
 N. Pliocene. 
 
 obliquata 
 
 O. Pliocene. 
 
 Omalii 
 
 > 
 
 ovata 
 
 M. and U. Oolite. 
 
 sulcata - 
 
 Post-Pliocene. 
 
 contcrta (cha- 
 racteristic) - 
 
 i Trias. Penarth. 
 
 cygnipes 
 
 L. and M. Lias. 
 
 Damuoniensis - 
 
 U. Devonian. 
 
 Danbyi 
 
 U. Silurian. Ludlow. 
 
PALEONTOLOGY. 183 
 
 Avicula 
 
 decorate eta. 1^ pmga ^ 
 
 
 echinata - L. Oolite. Cornbrash. 
 
 
 gryphseoides - U. Cretaceous. Gault to Ch. 
 
 
 Marl 
 
 
 inseq[uivalvis - L. Lias. 
 
 
 speluncaria ) AT -r> * r 
 (characteristic) } ^ Penman. Mag. L. 
 
 
 subradiata - M. and U. Devonian. 
 
 
 sp. - - Carboniferous. 
 
 
 sp. - - U. Oolite. Purbeck. 
 
 Aviculopecten 
 
 papyraceus - Carboniferous. 
 
 
 sublobatus - 
 
 Axinus 
 
 obscurus (cha- 1 AT TX, M- r 
 racteristic) - > M> Permian - Mag. L. 
 
 
 truncatus ) 
 
 
 (characteristic) ) " " 
 
 Bakevellia - 
 
 3,11 tlQ 113. \CiLd,- i -* - TV i r -r 
 
 racteristic)- j M. Permian. Mag. L. 
 
 Cardinia 
 
 Listeri - - L. and M. Lias. 
 
 Cardiola 
 
 fibrosa - - U. Silurian. Wenlock and 
 
 
 Ludlow. 
 
 Oardiomorpha 
 
 }*. * Ma g . L. 
 
 
 oblonga - - Carboniferous. 
 
 Cardita=Veneri- 
 
 
 cardia 
 
 analis - - N. Pliocene. 
 
 
 planicosta - M. Eocene. 
 
 
 senilis - - O. Pliocene. Wh. and H. 
 
 
 Crag. 
 
 
 sulcata - - U. Eocene. 
 
 Oardium 
 
 augustatum - O. Pliocene. R. Crag. 
 
 
 dissimile - U. Oolite. Portland. 
 
 
 edule - - N. Pliocene. N. Crag. 
 
 
 f asciatum - Post-Pliocene . 
 
 
 Grsenlandicuni N. Pliocene. 
 
 
 Hillanum - U. Cretaceous. U. Gr. 
 
 
 sphaeroidium - L. Cretaceous. L. Gr. 
 
 
 striatulum - L. and U. Oolite. Gt. Oo. 
 
 
 and Kim. Clay. 
 
 Ceromya 
 
 concentrica - L. Oolite. For. Marb. 
 
 Ohama 
 
 squamosa - M. and U. Eocene. 
 
 Coralliophaga 
 Corbula 
 
 cyprinoides - O. Pliocene. Wh. Crag. 
 alata - - L. Cretaceous. Weald en. 
 
184 
 
 FIELD GEOLOGY. 
 
 Corbula 
 
 - longirostris 
 
 - L. Eocene. 
 
 
 pisum 
 
 - M. and U. Eocene and L. 
 
 
 
 Miocene. 
 
 
 Vectensis 
 
 - U. Eocene. 
 
 
 sp. 
 
 - U. Oolite. Purleck. 
 
 
 sp. 
 
 - L. Cretaceous. Pirn field. 
 
 Crassatella - 
 
 - sulcata - 
 
 - M. and U. Eocene. 
 
 Crenella 
 
 - Isevigata 
 
 - Post-Pliocene. 
 
 
 nigra - 
 
 >5 
 
 Cryptodon - 
 Ctenodonta - 
 
 - aDgulatum 
 - Anglica 
 
 - L. Eocene. 
 - Silurian. Llandovery to 
 
 
 
 Ludlow. 
 
 
 deltoid ea 
 
 - Silurian. U. Llandovery. 
 
 
 Eastnori 
 
 M D 
 
 
 lingualis 
 
 ? M 
 
 
 semitruncata 
 
 - L. Silurian. Bala. 
 
 Cucullella - 
 
 - amygdalina 
 
 - M. and U. Devonian. 
 
 
 Cawdori 
 
 - U. Silurian. Ludlow. 
 
 
 Hardringii 
 
 - U. Devonian. 
 
 Cucullsea 
 
 - costellata 
 
 - L. Cretaceous. L. Gr. 
 
 s 
 
 elongata 
 
 - L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 
 fibrosa 
 
 - U. Cretaceous. U. Gr. 
 
 
 oblonga 
 
 - L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 Cyclas 
 
 - e'orgata 
 
 - L. Cretaceous. Wealden. 
 
 
 media - 
 
 ?> ?) 
 
 
 parva 
 
 - U. Oolite. Purleck. 
 
 Cyrena 
 
 - cuneiformis 
 
 - L. Eocene. 
 
 
 elongata 
 
 - U. Oolite. Purleck. 
 
 
 flurainalis 
 
 - Post-Pliocene. 
 
 
 major 
 
 - L. Cretaceous. Wealden. 
 
 
 media 
 
 5> } 
 
 
 obovata 
 
 - U. Eocene. 
 
 
 pulchra 
 
 j 
 
 
 semistriata 
 
 - U. Eocene and L. Miocene^ 
 
 
 tellinella 
 
 - L. Eocene. 
 
 Cyprina 
 
 - Island ica 
 
 - N. and Post-Pliocene. 
 
 
 Morrisii 
 
 - L. Eocene. 
 
 
 planata 
 
 ?> 
 
 
 rustica 
 
 - O. Pliocene. 
 
 Cytherea 
 
 - parva 
 
 - L. Cretaceous. L. Gr. 
 
 
 iucrassata 
 
 - M. and U. Eocene. 
 
 Exogyra 
 
 - columba 
 
 - U. Cretaceous. U. Gr. 
 
 
 con ica 
 
 U. Chalk. 
 
 
 sinuata 
 
 - L. Cretaceous. L. Gr. 
 
PALEONTOLOGY. 185- 
 
 Gervillia 
 
 - anceps - 
 
 L. Cretaceous. L. Gr. 
 
 
 aviculoides 
 
 M. and U. Oolite. 
 
 
 lanceolata 
 
 L. Oolite. Gt. Go. 
 
 
 siliqua - 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Go. 
 
 Goniomya - 
 
 - literata - 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Go. 
 
 
 scripta - 
 
 L. and M. Oolite. Gt. and' 
 
 
 - 
 
 Cor. Go. 
 
 Grammysia - 
 Gresslya 
 
 - cingulata 
 
 - abducta 
 
 U. Silurian. U. Ludloiv. 
 L. Oolite. Inf. Go. 
 
 
 peregrina 
 
 For. Marb. 
 
 Giyphaea 
 
 - convexa= 
 
 ) 
 
 
 Ostrea vesi- 
 
 VU. Cretaceous. U. Chalk. 
 
 
 cularis 
 
 ) 
 
 
 dilatata 
 
 M. Oolite. Oscf.Clay. 
 
 
 incurva 
 
 L. Lias. 
 
 
 nana 
 
 M. and U. Oolite. 
 
 
 vesiculosa 
 
 U. Cretaceous. U. Gr. 
 
 
 virgula 
 
 U. Oolite. Kim. Clay. 
 
 Hippopodium 
 
 - ponderosum - 
 
 L. Lias. 
 
 Inoceramus 
 
 - Brongniarti 
 
 U. Cretaceous. U. Chalk. 
 
 
 concentricus - 
 
 Gault. 
 
 
 Lamarckii 
 
 U. Chalk. 
 
 
 mytiloides 
 
 L. Chalk. J . 
 
 
 sulcatus 
 
 Gault. 
 
 Lsocardia 
 
 - minima - 
 
 L. Oolite. For. Marb. 
 
 
 tenera 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Go. 
 
 Isodonta 
 
 - triangularis - 
 
 L. and M. Oolite. Gt. and" 
 
 
 
 Cor. Go. 
 
 Leda 
 
 - amygdaloides - 
 
 L. Eocene. 
 
 
 limatula - 
 
 N. Pliocene. 
 
 
 pernula - 
 
 Post-Pliocene. 
 
 
 pygmea - 
 
 3> 
 
 
 truncata 
 
 J> 
 
 Lima=Plagios- 
 toma 
 
 - card iif or mis - 
 
 L. Oolite. Gt. Go. 
 
 
 duplicata 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Go. 
 
 
 gigantea 
 
 L. Lias. 
 
 
 globosa - 
 
 U. Cretaceous. L. Chalk 
 
 
 
 and Marl. 
 
 
 Hoperi - 
 
 U. Cretaceous. U. Chalk. 
 
186 
 
 FIELD GEOLOGY. 
 
 Lima=Plagios- 
 
 
 
 toma 
 
 - obliquata 
 
 U. Oolite. Portland, 
 
 
 pectiniformis - 
 
 L. Oolite. Inf. Oo. 
 
 
 rigida 
 
 Cor. Oo. 
 
 
 rigid ula 
 
 For. Marb. 
 
 
 rustica 
 
 M. and U. Oolite. 
 
 Lithodomus, 
 
 
 
 sub-genus of 
 
 
 
 Modiola - 
 
 - inclusus 
 
 L. to U. Oolite. 
 
 
 sp. 
 
 Carboniferous. 
 
 Lucina 
 
 - crassa 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 
 Portland ica - 
 
 U. Oolite. Portland. 
 
 
 tenera - 
 
 U. Cretaceous. Gault. 
 
 Lyrodeama 
 
 - cuneata - 
 
 Silurian. U. Llandovery. 
 
 Megalodon 
 
 - cucullatus 
 
 M. Devonian. 
 
 Modiola 
 
 - bipartita 
 
 L. and M. Oolite. For. Marb. 
 
 
 
 and Oxf. Clay. 
 
 
 cuneata - 
 
 Lias to M. Oolite. 
 
 
 minima (cha- 
 racteristic] - 
 
 i Trias. Penarth. 
 
 
 pallida 
 
 U. Oolite. Portland. 
 
 
 sp. 
 
 Purbeck. 
 
 
 scalprum 
 
 M. Lias. 
 
 Modiolopsis 
 
 - antiqua 
 
 U. Silurian. Wenlock. 
 
 
 complanata 
 
 Ludlow. 
 
 
 expansa - 
 
 L. Silurian. JSala. 
 
 
 platyphilla 
 
 U. Silurian. Ludlow. 
 
 Monotis 
 
 - decussata 
 
 L. Lias. 
 
 Mya 
 
 - arenaria 
 
 N. Pliocene. 
 
 
 truucata 
 
 Post-Pliocene. 
 
 Myacites 
 
 - calceif ormis 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 
 decurtata 
 
 L. Oolite. For. Marb. 
 
 
 mandibula 
 
 L. Cretaceous. L. Gr. 
 
 
 recurva 
 
 M. Oolite. Oxf. Clay. 
 
 
 securiformis - 
 
 L. Oolite. For. Marb. 
 
 Mytilus 
 
 - affinis 
 
 U. Eocene. 
 
 
 Cliemungensis- 
 
 U. Silurian. Wenlock. 
 
 
 edulis 
 
 Post-Pliocene. 
 
 
 Lyellii - 
 
 L. Cretaceous. Wealden. 
 
 
 septifer (cha- 
 racteristic) - 
 
 > M. Permian. 
 
 Nucula 
 
 - Bowerbankii - 
 
 L. Eocene. 
 
 
 Cobboldioe 
 
 O. and N. Pliocene. 
 
PALAEONTOLOGY. 187 
 
 Nucula 
 
 - nucleus - 
 
 - Post-Pliocene. 
 
 
 pectinata 
 
 - U. Cretaceous. Gault. 
 
 
 similis 
 
 - U. Eocene. 
 
 
 sp. 
 
 - Carboniferous. 
 
 Orthonota 
 
 - nasuta - 
 
 - L. Silurian. ala. 
 
 several species- U. Silurian. Ludlow. 
 
 Ostrea 
 
 - acnminata 
 
 - L. Oolite. Fuller's Earth. 
 
 
 Bellovacina 
 
 - L. Eocene. 
 
 
 carinata 
 
 L. Cretaceous. L. Gr. 
 
 
 cyatbula 
 
 - L. Miocene. 
 
 
 deltoid ea 
 
 - U. Oolite. Kim. Clay. 
 
 
 distorta 
 
 Purbeck. 
 
 
 expansa 
 
 Portland. 
 
 
 flabelloides 
 
 - L. Oolite. Inf. Oo. 
 
 
 flabellula 
 
 - M. Eocene. 
 
 
 frons 
 
 - U. Cretaceous. L. Chalk. 
 
 
 gregaria 
 intusstriata 
 (characteristic 
 
 - M. Oolite. Cor. Oo. 
 ") I naS ' 
 
 
 racteristic) 
 Marshii 
 
 - L. and M. Oolite. 
 
 
 princeps 
 
 - O. Pliocene. Wh. and R 
 
 
 
 Crag. 
 
 
 solitaria 
 
 - M. and U. Oolite. Cor. ana 
 
 
 
 Portland Oo. 
 
 
 undosa 
 
 - M. Oolite. Oxf. Clay. 
 
 
 Vectensis 
 
 - U. Eocene. 
 
 Pachyrisma 
 
 vesicularis= 
 Grypheea 
 convexa 
 - grande 
 
 1 U. Cretaceous. U. Chalk. 
 - L. Oolite. Gt. Oo. 
 
 Palaearca 
 
 _ amygdalis 
 
 - L. Silurian. Llandeilo. 
 
 
 socialis 
 
 ~ ?> 
 
 
 sp. 
 
 - U. Silurian. Ludlow. 
 
 Panopaea 
 
 - Norwegica 
 
 - N. and Post-Pliocene. 
 
 Peeten 
 
 _ annulatus 
 
 - L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 
 arcuatus 
 
 - L. and U. Oolite. Gt. and 
 
 
 
 Portland Oo. 
 
 
 asper 
 
 - U. Cretaceous. U. Gr. 
 
 
 Beaveri 
 
 - U. Cretaceous. L. Ch. and 
 
 
 
 Marl. 
 
 
 cinctua = 
 
 > L. Cretaceous. L. and M 
 
 
 crassitesta 
 
 - 5 Neocomian. 
 
188 
 
 FIELD GEOLOGY. 
 
 Pecten - - demissus 
 
 dentatus 
 
 fibrosus 
 
 Gerardi 
 
 Graenlandicus - 
 
 Island icus 
 
 lainellosus 
 
 Liassicus 
 
 nitidus 
 
 orbicularis 
 
 plebeius 
 quinquecos- 
 
 tatus 
 
 Valoniensis 
 (characteristic) 
 vimineus 
 
 Pectunculus - sublaevis 
 variabilis 
 
 Perna - - Mulleti 
 
 quadrata 
 
 Pholadomya - acuticosta 
 ambigua 
 cuneata 
 decussata 
 deltoid ea 
 equalis 
 fidicula 
 lyrata 
 
 margaritacea - 
 ovalis 
 
 Pholas - - crispata 
 
 Pinna - - affinis 
 
 granulata 
 lanceolata 
 
 mitis 
 
 Pleurophorus - costatus (cha- 
 racteristic) - 
 Pleurorhynchus= 
 
 Conocardium - equicostatus - 
 Hibernicus 
 
 Plicatula 
 
 pristis 
 - inflata 
 
 L. and M. Oolite. Gt. and 
 
 Cor. Go. 
 
 L. Oolite. Inf. Oo. 
 L. Oolite. For. Marb. 
 O. Pliocene. Wh. Crag. 
 Post- Pliocene. 
 
 U. Oolite. Portland. 
 M. Lias. 
 
 U. Cretaceous. U. Chalk. 
 IT. Cretaceous. Gault to Ch. 
 
 Marl. 
 O. Pliocene. E. Crag. 
 
 ( U. Cretaceous. U. Or. 
 
 > Trias. Penarth. 
 
 M. Oolite. Cor. Oo. 
 
 U. Cretaceous. U. Gr. 
 
 O. Pliocene. R. Crag. 
 
 L. Cretaceous. L. Gr. 
 
 U. Oolite. 
 
 L. Oolite. Gt. Oo. 
 
 L. M. and IT. Lias. 
 
 L. Eocene. 
 
 IT. Cretaceous. L. Chalk. 
 
 L. Oolite. For. Marb. 
 
 M. Oolite. Cor. Oo. 
 
 L. Oolite. Inf. Oo. 
 
 For. Marb. 
 L. Eocene. 
 L. to IT. Oolite. 
 N. Pliocene. 
 L. Eocene. 
 
 U. Oolite. Kim. Clay. 
 L. and M. Oolite. Gt. Oo. and 
 
 Cor. Oo. 
 L. and M. Oolite. Gt. Oo. and 
 
 Cor. Oo. 
 
 > M. Permian. Mag. L. 
 
 IT. Silurian. Wenlock. 
 Carboniferous. 
 Silurian. U. Llandovery. 
 U. Cretaceous. L. Chalk. 
 
PALEONTOLOGY. 189 
 
 Plicatula 
 
 - pectinoides 
 
 U. Cretaceous. Gault. 
 
 Posidonomya 
 
 - Becheri 
 
 Carboniferous. 
 
 Potamomya 
 
 - gregaria 
 
 M. Eocene. 
 
 
 plana 
 
 U. Eocene. 
 
 Pterinea 
 
 - bullata 
 
 Silurian. U. Llandovery. 
 
 
 retroflexa 
 
 Silurian. L. Llandovery to 
 
 
 
 Ludlow. 
 
 
 sublaevis 
 
 Silurian. U. Llandovery. 
 
 Pteroperna 
 
 - costatula 
 
 L. Oolite. Gt. Go. 
 
 Pullastra 
 
 - arenicola (cha- 
 racteristic) - 
 
 1 Trias. Penarth. 
 
 Quenstedtia - 
 
 - laevigata 
 
 L. and M. Oolite. Gt. and 
 
 
 
 Cor. Oo. 
 
 Eadiolites 
 
 - Mortoni 
 
 U. Cretaceous. L. Chalk. 
 
 Saxicava 
 
 - Arctica 
 
 Post-Pliocene. 
 
 
 rugosa 
 
 5) 
 
 Schizodus 
 
 - Schlotheimi 
 (characteristic} 
 
 f- M. Permian. Mag. L. 
 
 
 truncatus 
 
 5) 
 
 Sphaera 
 
 - corrugata 
 
 L. Cretaceous. L. Gr. 
 
 Spondylus - 
 
 - spinosus 
 gibbosus 
 
 U. Cretaceous. U. Chalk. 
 U. Cretaceous. Gault. 
 
 
 striatus - 
 
 L. Chalk. 
 
 Syndosmya - 
 
 - splendens 
 
 L. Eocene. 
 
 Tellina 
 
 - balthica= 
 solidula 
 
 t N. Pliocene. 
 
 
 calcarea= 
 
 t Post-Pliocene. 
 
 
 proxima 
 
 
 
 obliqua 
 
 N. Pliocene. 
 
 Tellinites - 
 
 - affinis 
 
 U. Silurian. Downton. 
 
 Teredo 
 
 - antenautse 
 
 L. Eocene. 
 
 Thetis 
 
 - major 
 
 L. and U. Cretaceous. L. and 
 
 
 
 U.Gr. 
 
 
 minor - 
 
 L. Cretaceous. L. Gr. 
 
 Thracia 
 
 - depressa 
 
 U. Oolite. Kim. Clay. 
 
 
 myopsis 
 
 Post-Pliocene. 
 
 Trigonia 
 
 - caudata 
 
 L. Cretaceous. L. Gr. 
 
 
 clavellata 
 
 M. and U. Oolite. Cor. Oo. 
 
 
 
 and Kim. Clay. 
 
 
 costata 
 
 L. to U. Oolite. 
 
 
 doedalia 
 
 L. and U. Cretaceous. L. and 
 
 
 
 U. Gr. 
 
 
 gibbosa 
 
 U. Oolite. Portland. 
 
 
 Goldfussii 
 
 L. Oolite. Gt. Oo. 
 
 
 impressa 
 
 U 5J 
 
 
 iucurva 
 
 - U. Oolite. Portland. 
 
190 
 
 FIELD GEOLOGY. 
 
 Unio - 
 
 compressus 
 
 U. Oolite. PurbecJc. 
 
 
 Gibbsii - 
 
 L. Miocene. 
 
 
 littoralis 
 
 Post-Pliocene. 
 
 
 Mantellii 
 
 L. Cretaceous. Wealden. 
 
 
 solandri 
 
 U. Eocene. 
 
 
 Valdensis 
 
 L. Cretaceous. Wealden. 
 
 Venus 
 
 incrassata 
 
 U. Eocene. 
 
 MAMMALIA. 
 
 Amphitherium - 
 
 Broderipii 
 
 L. Oolite. Stonesfield Slate. 
 
 
 Prevostii 
 
 V J? 
 
 Anoplotherium - 
 
 commune 
 
 U. Eocene. 
 
 
 secundarium - 
 
 )) 
 
 Anthracotherium- 
 
 sp. 
 
 U. Eocene. 
 
 Arvicola - - 
 
 pratensis 
 
 Post-Pliocene. 
 
 
 sp. 
 
 N. Pliocene. 
 
 Balaenodon - 
 
 emarginatus 
 (ear-bones) - 
 
 | O. Pliocene. R. Cray. 
 
 Bos 
 
 primigenius - 
 
 Post-Pliocene. 
 
 Cervus 
 
 anoceros 
 
 O. Pliocene. R. Crag. 
 
 
 megaceros = 
 
 ) 
 
 
 Megaceros 
 
 > N. and Post-Pliocene. 
 
 
 Hibernicus - 
 
 J 
 
 
 tarandus 
 
 Post-Pliocene. 
 
 Chaeropotamus - 
 
 Cuvieri - 
 
 U. Eocene. 
 
 Coryphodon 
 
 Eocenus- 
 
 L. Eocene. 
 
 Dichobune - 
 
 cervinum 
 
 U. Eocene. 
 
 Dichodon - 
 
 cuspidatus 
 
 M. and U. Eocene. 
 
 Didelphys - 
 
 Colchester! 
 
 L. Eocene. 
 
 Elephas 
 
 antiquus 
 
 N. Pliocene. 
 
 
 meridionalis - 
 
 
 
 grimigenius - 
 
 Post-Pliocene. 
 
 Equus 
 Felis - 
 
 Dssilis - 
 pardoides 
 
 N. Pliocene. 
 O. Pliocene. R. Crag. 
 
 
 spelaea - 
 
 Post-Pliocene. 
 
 Galestes 
 
 sp. 
 
 U. Oolite. Purbeclc. 
 
 Hippopotamus - 
 
 major 
 
 N. Pliocene. 
 
 Hyaena 
 
 spelaea - 
 
 Post-Pliocene. 
 
 Hyaenodon - 
 
 sp. 
 
 U. Eocene. 
 
 Hyracotherium - 
 Hyopatmus - 
 
 leporinum 
 bovinus - 
 
 L. Eocene. 
 U. Eocene and L. Miocene. 
 
 
 Vectensis 
 
 U. Eocene. 
 
 Lophiodon 
 
 minimus 
 
 M. Eocene. 
 
 
 sp. 
 
 L. Eocene. 
 
PALAEONTOLOGY. * 191 
 
 Macacus 
 
 Eocenus 
 
 L. Eocene. 
 
 Mastodon - 
 Microchserus 
 
 Arvernensis= 
 angustidens- 
 erinaceus 
 
 > O. and 1ST. Pliocene. 
 M. Eocene. 
 
 Microlestes - 
 Ovibos 
 
 antiquus 
 moschatus 
 
 Trias. Penarth. 
 Post-Pliocene. 
 
 Paloplotherium - 
 Palaeotherium 
 
 annectens 
 crassum - 
 
 M. Eocene. 
 U. Eocene. 
 
 
 curtum - 
 
 )> 
 
 
 magnum- 
 medium - 
 
 ?) 
 it 
 
 
 minimum 
 
 ij 
 
 
 minus 
 
 
 Phascolotherium - 
 Plagiaulax - 
 Pliolophus 
 Rhinoceros - 
 
 Bucklandi 
 Becklesii 
 vulpiceps 
 etruscus 
 leptorhinus = 
 
 L. Oolite. Stonesfield Slate. 
 U. Oolite. Purbeck. 
 L. Eocene. 
 N. Pliocene. 
 
 
 
 megarhinus - 
 Schleiermach- 
 eri 
 tichorhinus - 
 
 > O. Pliocene. R. Crag. 
 Post-Pliocene. 
 
 Spalacodon - 
 Spalacotherium - 
 Stereognathus 
 Tapirus 
 Triconodon - 
 Ursus 
 
 sp. 
 Brodiei - 
 Ooliticus 
 priscus - 
 sp. 
 Arvenensis 
 
 U. Eocene. 
 U. Oolite. Purbeck. 
 L. Oolite. Stonesfield Slate. 
 O. Pliocene. M. Crag. 
 U. Oolite. Purbeck. 
 N". Pliocene. 
 
 
 spelseus - 
 
 Post-Pliocene. 
 
 PISCES. 
 
 Acanthoides 
 Acrodus 
 
 sp. 
 
 M. Old Red. 
 
 Acrolepis 
 
 JEchmodus (Ge- 
 
 nus Liassic) 
 Aspidorhynchus 
 
 Asteracanthus 
 
 minimus (cha ) 
 
 racteristic - j " " 
 
 nobilis - - L. Lias. 
 
 Sedgwickii ") 
 
 (characte- >M. Permian. 
 
 r is tic) - - ) 
 
 Marl-Slate. 
 
 Leachii - 
 
 euodus - 
 
 Fisheri - 
 
 acutus - 
 
 - L. Lias. 
 
 - M. Oolite. 
 
 - U. Oolite. 
 
 - L. Oolite. 
 
 Oaf. Clay. 
 Purbeck. 
 For. Marl). 
 
192 
 
 1 FIELD GEOLOGY. 
 
 Asteracanthus 
 
 - granulosus 
 
 L. Cretaceous. Wealden. 
 
 
 ornatissimus - 
 
 U. Oolite. Kim. Clay. 
 
 
 semisulcatus - 
 
 L. Oolite. Gt. Oo. 
 
 Asterolepis - 
 
 - sp. 
 
 U. Old Red. 
 
 Auchenaspis 
 
 - ornatus - 
 
 U. Silurian. Downton. 
 
 
 Salteri - 
 
 
 Beryx- 
 
 - Lewesiensis - 
 
 U. Cretaceous. U. Chalk. 
 
 Carcharodon 
 
 - angustidens - 
 
 M. Eocene. 
 
 Cardiodon - 
 
 - rugulosus 
 
 L. Oolite. For. Marl. 
 
 Caturus 
 
 - angustus 
 
 U. Oolite. Portland. 
 
 Cephalaspis 
 
 - Lyelli - 
 
 L. Old Red. 
 
 
 Murchisonii - 
 
 U. Silurian. Downton. 
 
 Ceratodus - 
 
 - altus (charac- 
 
 \ Trias. Penarth. 
 
 
 teristic) 
 
 } 
 
 'Cheiracanthus 
 
 - sp. 
 
 M. Old Red. 
 
 Cheirolepis 
 
 - sp.^ 
 
 M. Old Red. 
 
 Cladodus 
 
 - striatus - 
 
 Carboniferous. 
 
 Cochliodus - 
 
 - contortus 
 
 Carboniferous. 
 
 Cocosteus - 
 
 - decipiens 
 
 U. Old Red. 
 
 
 sp. 
 
 M. Old Red. 
 
 Ccelacanthus 
 
 - granulatus 
 
 ) 
 
 
 (characte- 
 ristic - 
 
 >M. Permian. Marl-Slate. 
 
 'Coelopoma - 
 
 - Colei - 
 
 L. Eocene. 
 
 Ctenacanthus 
 
 - brevis - 
 
 Carboniferous. 
 
 Ctenodus 
 
 - sp. 
 
 M. Old Red. 
 
 Dapedius - 
 
 - monilifer 
 
 Lias. 
 
 
 politus - 
 
 L. Lias. 
 
 Dendrodus - 
 
 - sp. 
 
 M. Old Red. 
 
 Diplacanthus 
 
 - sp. 
 
 M. Old Red. 
 
 Diplodus 
 
 - gibbosus 
 
 C arb onif erous. 
 
 Diplopterus 
 
 - sp. 
 
 M. Old Red. 
 
 Dipteronotus 
 
 - cyphus - 
 
 Trias. 
 
 Dipterus 
 
 - sp. 
 
 M. Old Red. 
 
 Edaphodon - 
 
 - Bucklandi 
 
 M. Eocene. 
 
 
 Sedgwickii 
 
 U. Cretaceous. U. Gr. 
 
 Galeocerdo - 
 
 - latidens - 
 
 M. Eocene. 
 
 Glyptolepis - 
 
 - sp. 
 
 M. and U. Old Red. 
 
 Glyptopomus 
 
 - sp. 
 
 U. Old Red. 
 
 Gyrodus 
 
 - Cuvieri - 
 
 M. Oolite. Cor. Oo. 
 
 
 Mantellii 
 
 L. Cretaceous. Wealden. 
 
 Gyrolepis - 
 
 - tenuistriatus - 
 
 Trias. Penarth. 
 
 Holoptychius 
 
 - nobilissimus - 
 
 U. Old Red. 
 
 
 Portlockii 
 
 Carboniferous. 
 
 Hybodus 
 
 - acutus - 
 
 U. Oolite. Kim. Clay. 
 
 
 Keuperinus - 
 
 Trias. 
 
PALAEONTOLOGY. 193 
 
 Hybodus 
 
 - minor (cha- 7m- r> ji 
 . , ? Trias. Penarth. 
 ractenstic - \ 
 
 obtusus - - M. Oolite. Oxf. Clay. 
 
 plicatilis - Trias. Penarth. 
 
 reticulatus - L. Lias. 
 
 strictus - - U. Oolite. Portland. 
 
 subcarinatus - L. Cretaceous. Wealden. 
 
 Ischyodus - 
 
 - Townshendi - U. Oolite. Portland. 
 
 Lamna 
 
 - acuminata - U. Cretaceous. U. Chalk. 
 
 elegans - - L. and M. Eocene. 
 
 Lepidosteus 
 
 - sp. - - U. Eocene. 
 
 Lepidotus - 
 
 - Fittoni - - L. Cretaceous. Wealden. 
 
 gigas - - Lias. 
 
 macrocheirus - M. Oolite. Oxf. Clay. 
 
 Mantellii - U. Oolite and L. Cretaceous. 
 
 Leptolepis - 
 
 Macropoma - 
 Megalichthys 
 
 ~ m ^ s ph * hal ~ | M. Oolite. Oxf. Clay. 
 - Mantellii - U. Cretaceous. U. Chalk. 
 
 Microdon - 
 
 - radiatus- - U. Oolite. Purbeck. 
 
 Myliobates - 
 
 - Edwardsii - M. Eocene. 
 
 Nemacanthus 
 
 - monilifer(ca- ] 
 
 - Trias. Penarth. 
 
 Odontacanthus 
 
 - sp - M. Old Red. 
 
 Onchus 
 
 - Murchisonii - U. Silurian. Ludlow and 
 
 
 
 Downton. 
 
 tenuistriatus - U. Silurian. Ludlow. 
 
 arcuatus - M. Old Red. 
 
 sp. - - Carboniferous. 
 
 Ophiopsis - 
 
 - breviceps - U. Oolite. Purbeck. 
 
 Orocanthus - 
 
 - sp. - - Carboniferous. 
 
 Orodus 
 
 - ramosus- - Carboniferous. 
 
 Osmeroides - 
 
 - Lewesiensis - U. Cretaceous. U. Chalk. 
 
 Osteolepis - 
 
 - major - - M. Old Red. 
 
 Ostraceon - 
 
 - sp. - - M. Eocene. 
 
 Otodus 
 
 - appendicula- { U. Cretaceous. Gault to 
 
 tus - - y U. Chalk. 
 
 obliquus - L. and M. Eocene. 
 
 Palseoniscus 
 
 - comptus (cha- ' 
 racteristic) - 
 
 M. Permian. Marl-slate. 
 
 
 elegans (cha- 
 
 
 
 racteristic - 
 
 11 11 
 
 
 glaphyrus 
 
 
 
 (characte- 
 
 11 11 
 
 
 ristic) - 
 
 
 
 
 13 
 
194 
 
 FIELD GEOLOGY. 
 
 Petalodus - 
 
 - Hastingsiae - Carboniferous. 
 
 Pholidophorus 
 
 - Flesheri - - L. Oolite. Inf. Oo. 
 
 
 minor - Gt. Oo. 
 
 
 ornatus - -. U. Oolite. Purbeck. 
 
 Platygnathus 
 
 - sp. - M. Old Red. 
 
 Platysomus- 
 
 - macrurus ~i 
 (charade- V M. Permian. Marl-slate, 
 r is tic - - J 
 
 Plectrodus - 
 
 striatus (cha- ) -n/r T 
 . . .. x > .. Mag. L. 
 raderistic) - ) 
 
 - mirabilis - U. Silurian. Ludlow and 
 
 
 Downton. 
 
 
 pustuliferus - U. Silurian. Ludlow. 
 
 Paecilodus - 
 
 - Jonesii - - Carboniferous. 
 
 Pristis 
 
 - bisulcatus - L. Eocene. 
 
 Psammodus 
 
 - porosus - - Carboniferous. 
 
 Pteraspis - 
 
 - Banksii - - U. Silurian. Ludlow and 
 
 
 Dmvnton. 
 
 
 Ludensis - U. Silurian. Ludlow and 
 
 
 Downton. 
 
 
 truncatus - U. Silurian. Ludlow and 
 
 
 Downton. 
 
 
 Lloydii - - L. Old Red. 
 
 Pterichthys 
 
 - latus - - Old Red. 
 
 
 major - - M. Old Red. 
 
 Ptychodus - 
 
 - decurrens - U. Cretaceous. L. Chalk. 
 
 Pycnodus - 
 
 - Mantellii - L. Cretaceous. Wealden. 
 
 Pygopterus - 
 
 - mandibularis ^ 
 
 
 (charade- > M. Permian. Marl-slate- 
 
 
 ristic - - ) 
 
 Rhizodus - 
 
 - Hibberti - Carboniferous. 
 
 
 Portlockii - 
 
 Saurichthys 
 
 ~ apicans \cfia~ i rp _ z>~* // 
 ju x f J- rias. Jrcnartn. 
 
 Sphagodus - 
 Sphaerodus - 
 
 - pristodontus - U. Silurian. Ludlow. 
 - gigas - - U. Oolite. Kim. Clay. 
 
 Strophodus - 
 
 - magnus - L. Oolite. Gt. Oo. 
 
 
 subreticulatus Inf. Oo. 
 
 Tetrapterus 
 
 - priscus - - L. Eocene. 
 
 
 PLANTS. 
 
 Abietites 
 
 - Benstedi - L. Cretaceous. L. Gr. 
 
 Adiantites - 
 
 - Hibernicus - U. Devonian. 
 
 Alethopteris 
 
 - lonchitica - Carboniferous. 
 
 
 sp. - - Permian. 
 
PALEONTOLOGY. 195 
 
 Alnites 
 
 - Macquarii - L. Miocene. 
 
 Andromeda 
 
 - reticulata - L. Miocene. 
 
 Annularia - 
 
 " BP lS hyl " - } Carboniferous. 
 
 Aralia 
 
 - primigenia - M. Eocene. 
 
 Araucaria - 
 
 - sphaerocarpa - L. Oolite. Inf. Oo.' 
 
 Aroides 
 
 - Stutterdi - Stonesfteld Slate. 
 
 Asterophyllites 
 
 - foliosus - - Carboniferous. 
 
 
 grandis - 
 
 Betula 
 
 - nana - - Post-Pliocene. 
 
 Calami tes - 
 
 - cannaeformis - Carboniferous. 
 
 
 Sucowii - - Permian 
 
 Cardiocarpum 
 
 - anomalum - Carboniferous. 
 
 Carpolithes 
 
 - Bucklandi - M. Oolite. Cor. Oo. 
 
 
 conicus 
 
 
 Websteri - L. Miocene. 
 
 Caulerpites 
 
 - selaginoides ~| 
 (characte- >M. Permian. Marl-slate, 
 ristic) - J 
 
 Chara 
 
 - helicteres - L. Miocene. 
 
 
 Lyellii - - M. Eocene. 
 
 
 medicaginula - L. Miocene. 
 
 
 tuberculata - U. Eocene. 
 
 Clathraria - 
 
 - Lyellii - - L. and U. Cretaceous. 
 
 
 Weald, and Ch. M. 
 
 Comptonia - 
 
 - dryandrifolia - M. Eocene. 
 
 Corylus 
 
 - grosse-dentata Miocene. 
 
 Cruziana 
 
 - semiplicata - U. Cambrian. Lingula flags. 
 
 Cycadeoidea 
 
 - megaphylla - U. Oolite. Purbeck. 
 
 
 microphylla - 
 
 Cyclopteris - 
 
 - Hibernica - U. Oid Red. 
 
 
 dilatata - - Carboniferous. 
 
 Cyclostigma 
 Dammarites 
 
 - (sub- genus of ^ 
 Lepidoden- VU. Old Red. 
 dron) - - J 
 - Fittoni - - U. Oolite. Purbeck. 
 
 Dadoxylon - 
 
 - medullare - Carboniferous. 
 
 Daphnogene 
 
 - Yeronensis - M. Eocene. 
 
 Endogenites 
 
 - erosa - - L. Cretaceous. Wealden. 
 
 Equisetites - 
 
 - Brodiei - - L. Lias. 
 
 
 sp. - - Carboniferous. 
 
 Equisetum - 
 
 - columnare - L. Oolite. Inf. Oo. and Gt~ 
 
 
 Oo. and Trias. Keuper. 
 
 
 Lyellii - - L. Cretaceous. Wealden. 
 
 Ficus - 
 
 - granadilla - M. Eocene. 
 
 Fillicites - 
 
 - Hebridica - Miocene. 
 
 
 132 
 
196 
 
 FIELD GEOLOGY. 
 
 Flabellaria - 
 
 - Lamanonis - U. Eocene. 
 
 Glossopteris= 
 
 
 Sagenopteris 
 Hemitelites 
 
 - genus - - Oolitic. 
 - Brownii= "J 
 
 
 Phlebopteris > Carboniferous to Oolite. 
 
 
 contigua - J 
 
 Hightia 
 
 - elegans - - L. Eocene. 
 
 Kaidacarpum 
 
 - Ooliticum - L. Oolite. Gt. Oo. 
 
 Knorria 
 
 - dichotoma - U. Devonian. 
 
 Leguminosites 
 Lepidodendron 
 
 - several species L. Eocene. 
 - elegans - - Carboniferous. 
 
 
 elongatum - Permian. 
 
 
 Sternbergii - Carboniferous. 
 
 Lepidostrobus 
 
 - ornatus - - Carboniferous. 
 
 
 variabilis - ,, 
 
 Lonchopteris 
 
 - Mantellii - L. Cretaceous. Wealden. 
 
 Lycopodites 
 
 - sp. - Old Red. 
 
 Mantellia - 
 
 - nidiformis - U. Oolite. L. Purbeck. 
 
 Nelumbium 
 
 - Doris - - L. Miocene. 
 
 Neuropteris 
 
 - gigantea - Carboniferous. 
 
 Uipadites - 
 
 Huttoniana ^ 
 (characte- VM. Permian. Marl-slate, 
 ristic -- - j 
 - ellipticus - L. "Eocene. 
 
 
 umbonatus - ,, 
 
 Nullipora - 
 
 - polymorpha - Post-Pliocene. 
 
 Otopteris - 
 
 - genus - - Oolitic. 
 
 
 obtusa - - L. Lias. 
 
 Pachypteris 
 
 - genus - - Oolitic. 
 
 Palseozamia 
 
 - genus - - Oolitic. 
 
 
 Bechei - - L Lias. 
 
 Pecopteris - 
 
 Bucklandi - ,, 
 - aquilina - Carboniferous. 
 
 Petrophiloides 
 
 - Richardsoni - L. Eocene. 
 
 Phlebopteris 
 
 - contigua= 1 
 Hemitelites > Carboniferous to Oolite. 
 
 
 Brownii - j 
 
 Pinites 
 
 - Dunkeri - L. Cretaceous. Wealden. 
 
 
 elongatus - L. Oolite. Lias. 
 
 
 Eggensis - Miocene. 
 
 Podocarya - 
 
 - Bucklandi - L. Oolite. Inf. Oo. 
 
 .Pothocites - 
 
 - Grantonii - Carboniferous. 
 
 Pterophyllum 
 
 - genus - - Mesozoic. 
 
 
 comptum - L. Oolite. Gt. Oo. 
 
 Rhamnites 
 
 - multinervatus- Miocene. 
 
 Sagenopteris= 
 
 
 Glossopteris 
 
 - genus - - Oolitic. 
 
PALEONTOLOGY. 197 
 
 Sequoiea 
 
 - Couttsise 
 
 L. Miocene. 
 
 t 
 
 Langsdorfii 
 
 Miocene. 
 
 Sigillaria 
 
 - Isevigata 
 
 Carboniferous. 
 
 
 renit'ormis 
 
 
 Sphenophyllum 
 Sphenopteris 
 
 - erosum - 
 - gracilis - 
 
 Carboniferous. 
 
 L. Cretaceous. Wealden. 
 
 
 latifolia - 
 
 Carboniferous. 
 
 
 sp. 
 
 L. Oolite. 
 
 Stigrnaria - 
 
 - ficoides - 
 
 Carboniferous. 
 
 Thuytes 
 
 - genus 
 
 Mesozoic. 
 
 
 expansus 
 
 L. Oolite. Gt. Oo. 
 
 
 Kurrianus 
 
 L. Cretaceous. Wealden. 
 
 Taeniopteris 
 
 - genus 
 
 Oolitic. 
 
 
 latifolia 
 
 L. Oolite. Gt. Oo. 
 
 
 vittata 
 
 
 Trigonocarpum 
 
 - olivseforme 
 
 Carboniferous. 
 
 
 ovatum 
 
 
 TJllmania 
 
 -sp. 
 
 Carboniferous. 
 
 
 
 Permian. 
 
 Voltzia 
 
 - Phillipsii(cAa- 
 racteristic) - 
 
 | M. Permian. Mag. L. 
 
 Walchia 
 
 - piniformis 
 
 Permian. 
 
 Wetherellia 
 
 - variabilis 
 
 L. Eocene. 
 
 Zamia - 
 
 - genus 
 
 Oolitic. 
 
 
 gigas 
 
 L. Oolite. Inf. Oo. 
 
 POLYZOA. 
 
 Cellepora 
 
 - celluldsa 
 
 O. Pliocene. Wh. Crag. 
 
 
 favosa - 
 
 U. Silurian. Wenlock. 
 
 Ceriopora 
 
 - affinis 
 
 U. Silurian. Wenlock. 
 
 Crisia 
 
 - eburnea 
 
 Post-Pliocene. 
 
 Diastopora - 
 
 - diluviana 
 
 L. Oolite. For. Marb. 
 
 Discopora - 
 
 - antiqua - 
 
 U". Silurian. Wenlock. 
 
 Eschara 
 
 - Brongniarti 
 
 L. Eocene. 
 
 
 disticha - 
 
 U. Cretaceous. Chalk. 
 
 Escharina - 
 
 - oceani 
 
 U. Cretaceous. Chalk. 
 
 Fasicularia - 
 
 - aurantium 
 
 O. Pliocene. Wh. Crag. 
 
 FenesteUa - 
 
 - antiqua - 
 
 Carboniferous. 
 
 
 Lonsdalei 
 
 U. Silurian. Wenlock. 
 
 
 membranacea - 
 
 Carboniferous. 
 
 
 plebeia=reti- 
 
 ) 
 
 
 f ormis (cha- 
 
 > M. Permian. Mag. L. 
 
 
 racteristic) - 
 
 ) 
 
 
 sociale 
 
 U. Cambrian. Lingula flags. 
 
 Flustra 
 
 - crassa 
 
 L. Eocene. 
 
198 
 
 FIELD GEOLOGY. 
 
 Heteropora - 
 
 - cryptopora 
 
 - U. Cretaceous. U. Chalk. 
 
 
 raniosa - 
 
 - L. and M. Oolite. Gt. and 
 
 
 
 Cor. Go. 
 
 Hippothoa 
 
 - catenularia 
 
 - Post-Pliocene. 
 
 Lepralia 
 
 - Peachii 
 
 - Post-Pliocene. 
 
 Lunulites - 
 
 - cretaceus 
 
 - U. Cretaceous. U. Chalk. 
 
 Oldhamia - 
 
 - antiqua 
 
 - L. Cambrian. Longmynd. 
 
 
 radiata 
 
 5J 3) 
 
 Polypora 
 
 - sp. 
 
 - Carboniferous. 
 
 Ptilodictya 
 
 - acuta 
 
 - L. Silurian. Bala. 
 
 
 scalpellum 
 
 - Silurian. Llandovery and 
 
 
 
 Wenlock. 
 
 Synocladia 
 
 - virgulacea 
 (characteristi 
 
 . ^ > M. Permian. Mag. L. 
 
 Thamniscus 
 
 
 }M. Permian. Mag. L. 
 
 Theonoa 
 
 racteristic) 
 - fflobosa - 
 
 - O. Pliocene. Wh. Crag. 
 
 PTEROPODA. 
 
 Conularia - 
 
 - corium - 
 
 - L. Silurian. Llandeilo. 
 
 
 ornata 
 
 - M. Devonian. 
 
 
 Sowerbyi 
 
 - Silurian. Bala -to Ludlow. 
 
 
 subtilis - 
 
 - U. Silurian. Ludlow. 
 
 Ecculiomphalus 
 
 - Isevis 
 
 - Silurian. Llandovery and 
 
 
 
 Ludlow. 
 
 Theca 
 
 - anceps - 
 
 - U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 Forbesii 
 
 - U. Silurian. Wenlock and 
 
 
 
 Ludlow. 
 
 
 operculata 
 
 - U. Cambrian. Tremadoc. 
 
 
 c~rrugata 
 
 - L. Cambrian. 
 
 
 triangularis 
 
 - L. Silurian. 
 
 KEPTILIA. 
 
 Anthracosaurus 
 Alligator 
 
 Cetiosaurus 
 CJhelone 
 
 - Russelli - 
 - Hantoniensis 
 ,sp. - 
 -'brevis 
 longus - 
 - Bellii - 
 Benstedi 
 breviceps 
 
 Carbon if erous. 
 M. Eocene. 
 U. Eocene. 
 
 L. Cretaceous. Wealden. 
 U. Oolite. Portland. 
 L. Cretaceous. Wealden. 
 U. Cretaceous. L. Chalk. 
 L. Eocene. 
 
PALAEONTOLOGY. 199 
 
 Crocodilus - 
 
 - champsoides - 
 
 L. Eocene. 
 
 
 Hastingsise 
 
 M. Eocene. 
 
 
 toliapicus 
 
 L. Eocene. 
 
 
 sp. 
 
 TJ. Eocene. 
 
 Dimorphodon 
 
 - macronyx 
 
 L. Lias. 
 
 Dolichosaurus 
 
 - lougicollus 
 
 U. Cretaceous. L. Chalk. 
 
 Dolichosoma 
 
 - Emmersoni 
 
 Carboniferous. 
 
 Erpetocephalus 
 
 - rugosus - 
 
 Carboniferous. 
 
 Emys 
 
 -sp. 
 
 L. Cretaceous. Wealden. 
 
 
 testudiniformis 
 
 U. Eocene. 
 
 Oavialis 
 
 - Dixoni - 
 
 M. Eocene. 
 
 <*oniopholis 
 
 - crassidens 
 
 U. Oolite and L. Cretaceous. 
 
 
 
 Purbeck and Wealden. 
 
 Heraterpeton 
 
 - Galvani 
 
 Carboniferous. 
 
 Hylseosaurus 
 
 - Owenii - 
 
 L. Cretaceous. Wealden. 
 
 Hyperodapedon 
 Ichthyerpeton 
 
 - Gordon! 
 - Bradleyse 
 
 Trias. Keuper. 
 Carboniferous. 
 
 Ichthyosaurus 
 
 - genus 
 
 Trias to U. Cretaceous. 
 
 
 campylodon - 
 
 U. Cretaceous. L. Chalk. 
 
 
 communis 
 
 L. Lias. 
 
 
 platyodon 
 
 > 
 
 
 trigonus 
 
 U. Oolite. Kim. Clay. 
 
 Iguanodon 
 
 - Mantellii(#er^ 
 characteristic) 
 
 ! L. Cretaceous. Wealden. 
 
 Labyrinthodon 
 
 - (Amphibian) - 
 
 Devonian to Trias. 
 
 
 giganteum 
 
 Trias. 
 
 Lepterpeton 
 
 - Dobbsii 
 
 Carboniferous. 
 
 Loxomma 
 
 - Allmanni 
 
 Carboniferous. 
 
 Macellodus 
 
 - Brodiei 
 
 U. Oolite. Purbeck. 
 
 Macrorhynchus 
 
 -sp. 
 
 U. Oolite. Purbeck. 
 
 Megalosaurus 
 
 - Bucklandi 
 
 L. Oolite. Gt. Oo. 
 
 
 sp. 
 
 L. Cretaceous. Wealden. 
 
 Mosasaurus 
 
 - gracilis - 
 
 U. Cretaceous. U . Gludk. 
 
 Nothetes 
 
 - destructor 
 
 U. Oolite. Purbeck. 
 
 Ophiderpeton 
 
 - Brownriggii - 
 
 Carboniferous. 
 
 Paleryx 
 
 -sp. 
 
 U. Eocene. 
 
 Palaeophis - 
 
 - toliapicus 
 
 L. Eocene. 
 
 
 typhaeus 
 
 M. Eocene. 
 
 Pholidogaster 
 
 - pisciformis 
 
 Carboniferous. 
 
 Plesiosaurus 
 
 - affinis 
 Bernard! 
 
 U. Oolite. Kim. Clay. 
 U. Cretaceous. L. Chalk. 
 
 
 dolichodeirus - 
 
 L. Lias 
 
 
 sp. 
 
 Trias. Penarth 
 
 Pleurosternon 
 
 - ovatum - 
 
 U. Oolite. Purbeck. 
 
 Pliosaurus 
 
 - grandis - - 
 
 U. Oolite. Kim. Clay. 
 
 Polyptychodon 
 
 - interruptus 
 
 U. Cretaceous. Gault and 
 
 
 
 L. Chalk. 
 
200 
 
 FIELD GEOLOGY. 
 
 Polyptychodon 
 
 continuus 
 
 L. Cretaceous. L. Gr. 
 
 Protemys 
 
 serrata - 
 
 L. Cretaceous. L. Gr. 
 
 Protosaurus 
 
 Speneri - 
 
 M. Permian. Marl-slate. 
 
 Pterodactylus 
 
 Cliftii - 
 
 L. Cretaceous. Wealden. 
 
 
 Cuvieri - 
 
 U. Cretaceous, L. Chalk. 
 
 Rhynchosanrus 
 
 sp. 
 
 Trias. Keuper. 
 
 Steneosaurus 
 
 rostro-minor - 
 
 U. Oolite. Kim. Clay. 
 
 Streptospondylus - 
 Thecodontosaurus- 
 
 major 
 sp. 
 
 L. Cretaceous. Wealden. 
 Trias. Bunter. 
 
 Teleosaiirus 
 
 asthenodeirus 
 
 U. Oolite. Kim. Clay. 
 
 
 Chapmanui 
 
 L. Lias. 
 
 
 sp. 
 
 L. Cretaceous. L. Gr. 
 
 Tretosternon 
 
 Bakevillii 
 
 L. Cretaceous. Wealden. 
 
 Trionyx 
 
 sp. 
 
 L. Cretaceous. Wealden. 
 
 
 incrassatus 
 
 U. Eocene. 
 
 Urocordylus 
 
 Wandesfordii - 
 
 Carboniferous. 
 
 EHIZOPODA (FOKAMINIFERA). 
 
 Bulimina 
 
 - obliqua - 
 
 U. Cretaceous. U. Chalk. 
 
 Cornuspira 
 
 - foliacea - 
 
 Post-Pliocene. 
 
 Cristellaria 
 
 - rotulata - 
 
 U. Cretaceous. V. Chalk. 
 
 
 Wetherellii - 
 
 L. Eocene. 
 
 Dentalina - 
 
 - acuta 
 
 L. Eocene. 
 
 
 communis 
 
 L. Silurian. Bala. 
 
 
 gracilis - 
 
 U. Cretaceous. U. C/ialk. 
 
 Endothyra - 
 
 -sp. 
 
 U. Silurian. 
 
 
 sp. 
 
 Carboniferous. 
 
 Eozoon 
 
 - Canadense 
 
 L. Laurentian. 
 
 Pusulina 
 
 - cylindrica 
 
 Carboniferous and Permian, 
 
 Globigerina - 
 
 - bulloides 
 
 Post-Pliocene. 
 
 Lagena 
 
 - ieyis 
 
 Post-Pliocene. 
 
 Nodosaria 
 
 - upwards from- 
 
 Carboniferous. 
 
 Nummulites 
 
 - Isevigata 
 
 M. Eocene. 
 
 
 radiata' - 
 
 
 
 scabra 
 
 
 Operculina 
 
 - complanata 
 
 0. Pliocene. Wh. Crag. 
 
 Polymorphina 
 
 - communis 
 
 O. Pliocene. R. Crag. 
 
 
 Liassica 
 
 L. and M. Lias. 
 
 Polystomella 
 
 - striato-punc- 
 
 i Post-Pliocene. 
 
 
 tata - 
 
 ) 
 
 Quinqueloculina 
 
 - Hauerina 
 
 M. Eocene. 
 
 
 seminulum 
 
 Post-Pliocene. 
 

 PALAEONTOLOGY. 
 
 201 
 
 Kotalina 
 
 Spirilina 
 Textularia - 
 Triloculina - 
 
 - caracolla - U. Cretaceous, 
 obscura - M. Eocene, 
 ornata - - U. Cretaceous. 
 - infima - - L. Lias. 
 - upwards from- Carboniferous. 
 - cor-anguinum - M. Eocene. 
 
 Gault. 
 U. Chalk. 
 
 
 SPONGID^E. 
 
 * 
 
 Chenendopora 
 Choaaites - 
 Siphonia 
 Ventriculites 
 
 - fungiformis - U. Cretaceous. 
 - Konigi - - U. Cretaceous. 
 - pyriformis - U. Cretaceous. 
 - decurrens - U. Cretaceous, 
 radiatus 
 
 U.Gr. 
 U. Ctialk. 
 U. Gr. 
 U. Chalk. 
 
 
 Verticillites 
 
 - anastomosans - U. Cretaceous. 
 
 U"&r. 
 
PART V. 
 
 CHAPTER I. 
 
 Survey of Older Eocks Boundaries and Faults Downthrow 
 Vertical Section Eruptive Eocks Veins. 
 
 Survey of Older Rocks. As an example of geological 
 mapping which involves the application of nearly all 
 the methods and operations described in the preceding 
 pages, we may now take a district supposed to consist 
 of palaeozoic rocks. These being much older than 
 those previously mapped (pp. 17 to 27, and figs. 5 8) are 
 consequently much more likely to have been disturbed, 
 faulted, and contorted. In mapping such rocks it is a 
 good plan first to make oneself well acquainted with 
 the physical geography of the district to be surveyed 
 to find out the watershed of the area, the system of its 
 valleys, the highest points of its hills, and the amount 
 of their elevation. We get therefrom a general idea of 
 how the rocks, if not eruptive, will probably be found 
 to run, for, as stated in Part I. (p. 15), beds almost in- 
 variably dip towards higher ground to the form of 
 which their inclination has indeed greatly contributed ; 
 therefore the contour of a hill approximately indicates 
 
FIELD GEOLOGY. 203 
 
 the local strike, or rather outcrop, of the beds of which 
 it is composed. In a country abounding in continuous 
 escarpments, long ridges, and sweeping valleys we might 
 naturally expect to find a tolerable consistency in the 
 inclination of the strata; in a rugged broken surface 
 we should see indications of sudden changes of dip, 
 both in amount and direction, of faults, fractures, and 
 contortions. 
 
 The next step would be to visit all the quarries, lime- 
 kilns, brick-yards, or coal-mines, the existence of which 
 we have been able to ascertain, and in all of them, 
 by inspection and inquiry, obtain some useful infor- 
 mation. By this means we get a good general idea of 
 what the rocks of the district are, of the formation to 
 which they belong, of their local nature and charac- 
 teristics. 
 
 Assume all this to have been done, and that we 
 are about to map in detail an area, the rocks of which 
 consist of a Red Sandstone and a series of Limestones 
 (? Permian) overlying the " Upper Coal-measures." We 
 have visited the three quarries in the Sand and Lime- 
 stones shown on the map, fig. 21, ascertained that in 
 two instances the dip is due S. 10 and 14 respectively, 
 due N. 5 in the third. This evidently indicates an 
 anticline (or possibly a series of faults) which has 
 brought up the underlying Carboniferous rocks nearer 
 to the surface, and given origin to the valley by which 
 they have been exposed (p. 36). To avoid confusion, the 
 roads, &c., are omitted from the map, and the quarries 
 numbered in the absence of other means of identifi- 
 cation. 
 
204 
 
 FIELD GEOLOGY. 
 
 Fig. 21. Scale 3 inches to 1 mile. 
 
FIELD GEOLOGY. 205 
 
 REFERENCE 
 TO "PTO 91 
 
 LOWER TRIAS ^\-'/'-\BU HTSH SANDSTONE. 
 
 MIDDLE PERHIAN. ^=[ HA6NESIAH LIMESTONE 
 
 LOWER PERU IAN*.... 
 
 UPPER 
 CARBONIFEROUS. 
 
 ..} ^3$ LIMESTONE 
 
 OYKC 
 
 In Quarries No. 1 and 2 we found sandstones, sand, 
 and marl, with thin partings of shale, the latter slightly 
 effervescent. The former were of a reddish-brown 
 colour, very micaceous, and small patches of a whitish- 
 looking rock, soft and minutely crystalline, were ob- 
 served. This substance did not effervesce upon appli- 
 cation of acid, and was scratched even by the nail ; it 
 is therefore Gypsum. Quarry No. 3 was being worked 
 on an extensive scale for building purposes ; the stone 
 derived from it varied considerably in texture, might be 
 readily scratched with a knife, effervesced slowly, and 
 was of a grey colour. The compact beds were very fos- 
 siliferous, broke evenly with a dull lustre, and those of 
 crystalline texture presented a conchoidal fracture and 
 possessed a vitreous lustre. The rock is almost certainly 
 Magnesian Limestone passing gradually into Dolomite, 
 but the evidence derived from the fossils will be con- 
 clusive. 
 
 The notes taken in the quarries are recorded below : 
 
206 FIELD GEOLOGY. 
 
 Quarry (No. 1). Date 187 . 
 
 10 feet, brown and red sandstone or freestone, 
 with red marl below; the surfaces of some 
 of the beds are plainly ripple-marked. 
 Dip. K 5. 
 
 Quarry (No. 2). Date 187 . 
 
 30 feet, alternating and varying beds of mica- 
 ceous sandstone and sand, indistinctly bedded, 
 with shaley divisions and patches of gypsum. 
 The uppermost part of this section is in a cal- 
 careous shale, with detached and weathered 
 pieces of limestone (? Magnesian). Few fossils 
 only occur; these are occasional pieces of a 
 substance presenting a woody structure (? Co- 
 niferous), and in the shales above some fishes* 
 scales. Dip S. 10. 
 
 FOSSILS. 
 
 (In the Sand.) Coniferous Wood. 
 (In the Shales.) Palceoniscus comptus. 
 
 Quarry (No. 3). Date 187 . 
 
 40 feet, magnesian limestone, tabular and 
 jointed, in beds from 2 to 4 feet thick, with 
 thin earthy layers between. The upper beds 
 are light-grey in colour, with many fossils and 
 some concretions, also traces of ripple-marks. 
 Lower down the stone gets harder and in 
 some cases granular ; the lowest beds are of 
 
FIELD GEOLOGY. 207 
 
 darker colour, more gritty texture, and in 
 some parts distinctly crystalline. 
 Dip S. 14. 
 
 FOSSILS. 
 
 Fenestella retiformis. Monotis speluncaria. 
 
 Producta horrida. Schizodus obscurus. 
 
 Camarophoria crumena. Bakevellia antiqua. 
 
 Boundaries and Faults. The boundary of the 
 limestone is readily traced by indications here and 
 there, and by rather sudden change of feature; the 
 line runs just S. of Quarry No. 2 ; the shale and pieces 
 of weathered limestone observed there are consequently 
 the last remaining traces of the lower part of the Mag- 
 nesian Limestone. But in walking over the S.E. corner 
 of the sheet it was found to consist of a red or mottled 
 sand ; and in the only open section, the coal-pit shown 
 on the map, the beds were seen to lie in a horizontal 
 position. They must therefore rest unconformably on 
 the limestone which dips S. at a high angle, and the 
 direction of the boundary of the sand when drawn 
 affords a similar indication. For instead of running 
 even approximately parallel to that of the limestone, as 
 it would if the two were conformable, it gradually ap- 
 proaches and would probably overlap it at a short dis- 
 tance farther to the E. 
 
 The line of the sand is next traced in the usual 
 manner, and without difficulty, from the E. side of the 
 sheet nearly to the "W., where it seems to take a sudden 
 and unexpected turn towards the N. Following this 
 new line somewhat dubiously, and with no feature to 
 
208 FIELD GEOLOGY. 
 
 guide us, we find that ere long the boundary resumes 
 its old direction. There is something here to be ac- 
 counted for, but drawing a dotted line to represent the 
 uncertain portion, we leave it for the present and await 
 further evidence. A small pit near the extremity of 
 the sand shows the amount of dip there to be 6 only, 
 but it is the same as the others in direction. 
 
 We now proceed to trace the outcrop of any coal- 
 seams that may occur in the area, and, beginning on the 
 W. side, follow one such line for a short distance, when 
 the evidence of its course entirely ceases. But another 
 line of outcrop commences from the north and south 
 portion of the limestone boundary, and (where traceable) 
 runs nearly in the same direction. When drawn, these 
 two lines of coal-crop, in their direction and (where one 
 ends and the other begins) in their distance from the 
 limestone, look remarkably like two portions of one and 
 the same seam. If they be so, the seam must have 
 been dislocated by a fault, which would account also 
 for the sudden deflection in the limestone boundary 
 and the return to its ordinary direction. A line is drawn 
 to represent provisionally such a fault, running through 
 the ascertained ends of the coal-crops, and coinciding 
 as nearly as may be with the doubtful limestone line 
 previously dotted on the map. Further evidence may 
 or may not be forthcoming. 
 
 In traversing the Coal-measures area, between that 
 now surveyed and the river, we came across a mass of 
 rock quite different in character. The notes of this and 
 the mode of procedure connected therewith are deferred 
 for the present, and will be found at p. 213. 
 
FIELD GEOLOGY. 209 
 
 On the N. side of the river the limestone does not 
 come within the area ; the line of the sand is run as 
 before, but after tracing it for about half its length we 
 meet with a break in it similar in every respect to that 
 on the other side of the river. It seems also to be in 
 the same direction or thereabouts ; indeed it fits in with 
 the provisional line of fault when the latter is suffi- 
 ciently extended there can now be no doubt of the 
 existence of a dislocation. This fact is further corrobo- 
 rated by the coal-crops on the K, which behave exactly 
 in a similar manner to those on the S., except that one 
 portion of the line has been thrown back somewhat 
 towards its former position. When the outcrop has 
 been carefully mapped, it is found that this second 
 throw can be explained in one way only that is, by 
 another fault, nearly at right angles to the first, passing 
 through the broken ends of the coal-seam, as shown in 
 the drawing, fig. 21. 
 
 Downthrow. The amount of downthrow at any part 
 of the fault can be easily calculated from the known dip 
 .and the lateral shift of the beds where crossed by the 
 line of section, at * fig. 22, it is 107 feet the following 
 being one method of its calculation. From * (in this case 
 on the end of the unshifted part of the coal-seam) to the 
 nearest part of the shifted portion (i.e. in the direction 
 of the rise) the distance is 200 yards the fall of the 
 ground between, as ascertained by aneroid or otherwise, 
 being 20 feet. By Table, Part II. p. 50, the depth below 
 the surface attained by the coal-seam, with a dip of 8 
 in 200 yards (-600 feet), is 87 feet, which added to 
 the 20 feet fall=107 feet, the amount of downthrow at 
 the point *. The result would be arrived at, if the 
 
 14 
 
210 
 
 FIELD GEOLOGY. 
 
 section crossed the fault at any other point, by ascertain- 
 ing the depth beneath the surface, at such point, of each 
 part of the broken coal-seam, or each part of the under 
 surface of the sandstone calculated from its boundary. 
 
 The dip of the beds 
 in the section, fig. 22, 
 is shown much less 
 than it would be if the 
 line of section coincided 
 with that of the dip; 
 in this case it deviates 
 therefrom as much as 
 45 degrees. The varia- 
 tion and the method of 
 determination of the dif- 
 ference are explained in 
 Part II. In this example 
 the dip of the limestone 
 at its boundary is about 
 10 30', judging from that 
 ^ observed in the quarries 
 on either side. By dia- 
 gram the apparent angle, 
 corresponding to 10 30', 
 with 45 deviation, is- 
 7 30' only, as drawn on 
 the section; where the 
 line of section first 
 crosses the boundary of 
 the sand the dip is 
 
 8 30', and this angle 
 with the same variation shows 6 only, as represented. 
 
FIELD GEOLOGY. 211 
 
 The dip of the coal-seam, where first crossed has not 
 been ascertained, but beyond the fault its dip is greater 
 by 2 than that of the sand ; on this side they must 
 have the same difference in inclination, the seam 
 therefore dips at 10 30' its apparent angle will be 
 7 30' where crossed by the section. The extremity of 
 the sand where the line again crosses it is dipping 6, 
 apparent dip 4, and the coal-seam 8, which will be 
 shown 5 30' only, on account of the deviation. 
 
 Vertical Section. The beds shown in the section, 
 fig. 22, could not have been continued to so great a 
 depth from their outcrop (nor could the lower ones 
 have been inserted at all) on the evidence obtained 
 only on the surface, although even that would have 
 furnished an approximation to the depth of the Coal- 
 measures beneath the Bunter Sandstone ; the additional 
 particulars were obtained from the proprietor of the 
 coal-mine, and are as given below. 
 
 ; . Coal Mine, North Shaft. 
 
 To 100 feet. Soft sandy stone, red and yellow. Level. 
 460 Hard rock. 
 740 Freestone. 
 
 Shales. 
 
 At 800 " Three-foot " Coal, rising N., 3' 3" thick. 
 Shales and Ironstone layer in the middle.. 
 920 Bed of hard blue stone, 8' thick. 
 
 Shales. 
 1080 " Thin Coal," rising North, 1' 6" thick. 
 
 Shales. 
 
 1400 " Lower three-foot " Coal, 3' thick. 
 Shales. 
 
 142 
 
212 
 
 FIELD GEOLOGY. 
 
 At 1280 feet. Fire-clay, 4' thick. 
 
 Shales. 
 1560 " Bottom Coal," rising North, 1' 3" thick. 
 
 Shales. 
 ,,1640 Grit " Farewell Eock." 
 
 All the layers below the Freestone rise North at about 
 15. 
 
 ( Bunter 
 JH < Sandstone, 
 I 100'. 
 
 r Middle 
 Permian, 
 360'. 
 
 Lower 
 Permian 
 
 Coal- 
 measures, 
 900'. 
 
 Millstone 
 L Grit. 
 
 Mottled Sandstone. 
 
 Magnesian Limestone. 
 
 Brown and Red Micaceous 
 Sandstone. 
 
 " Three-foot" Coal, 3 7 3 r/ . 
 Layer of Iron-stones. 
 Limestone, 8' 0". 
 
 " Thin Coal," 1' 6". 
 
 " Lower Three-foot" Coal, 3' 0". 
 Fire-clay. 4' O' 7 . 
 
 " Bottom" Coal, 1' 3". 
 
 Fig. 23. 
 
FIELD GEOLOGY. 
 
 Note. The particulars of the coal shaft when drawn 
 to scale, and with the beds assigned to their 
 proper formations, constitute what is called 
 a " Vertical Section" (fig. 23). 
 
 By drawing the section (fig. 22) at the surface, from all 
 the dips and particulars obtained, then inserting the data 
 from the coal-shaft in their proper position (with the 
 dips reduced for deviation of the line), we have no 
 difficulty in correlating the beds and uniting the ascer- 
 tained points in their planes of stratification. The coal- 
 seam which comes to the surface where the section 
 crosses the fault is thus shown to be the "Thin-coal " at 
 1080 feet; the one above it, at 800, is doubtless the 
 seam that crops out on the E. side of the area. 
 
 Eruptive Rocks. The rock of different character met 
 with in traversing the Coal-measures area, p. 208, was first 
 seen in a wall-like terrace running in a N.W. direction ; 
 all its outer surface was weathered almost to whiteness. 
 With some trouble a specimen is detached which shows 
 the rock beneath the weathering ; this is grey in colour, 
 does not effervesce under acid, and can be scratched by 
 a knife with difficulty, therefore it consists of silicates. 
 It is compact in texture, even in fracture, and has a 
 vitreous lustre ; it is probably Felstone, and the mass is 
 either eruptive or intrusive. 
 
 There is no difficulty in mapping the mass, as it 
 makes quite a feature standing out from the softer and 
 more easily-denuded Coal-measures ; on one side only 
 are there recent accumulations of rain-wash, but by 
 these the feature is not obliterated. The rock proves 
 
214 FIELD GEOLOGY. 
 
 to be not interbedded with the coal and shales, but an 
 eruptive dyke breaking through the strata without the 
 slightest conformity to their lines of stratification. In 
 mapping the eruptive rocks (and intrusive also until 
 proved to be interbedded) it should be borne in mind 
 that they behave at the surface in an irregular manner, 
 very similar to that of the glacial drifts ; their boun- 
 dary must be closely followed, while the remarks upon 
 the drifts (at pp. 34 et seq.) may in these cases also be 
 found of some advantage. 
 
 Veins. The mapping of lodes or metallic veins is 
 very similar, as these follow an irregular course ; but it 
 will usually be found that they make a surface feature, 
 as an elevation or depression according to the varying 
 hardness and dip of the beds or masses in which they 
 occur. 
 
 CHAPTER II. 
 
 Geological Generalisation and Practical Results Water-supply 
 
 Soils. 
 
 Generalisation. A geological examination of a quarry 
 may seem a trifling matter, and one from which no very 
 grand results can be expected. But the knowledge thus 
 obtained, as pointed out in p. 2, is not simply and 
 strictly a local knowledge, for it extends a long way into 
 and beneath the surface of the earth. We see, there- 
 fore, that examination of several such quarries must 
 make us acquainted with the nature and position of 
 the rocks a long way down over all the intervening 
 area. 
 
FIELD GEOLOGY. 215 
 
 The geologist having, by careful and accurate obser- 
 vation of all available data, attained this knowledge of 
 a district, and, viewing the whole tract at once, as 
 upon a map, can in his mind lift up, as it were, formation 
 after formation, and see those beneath as plainly as 
 though they had never been covered. In imagination 
 removing one series of deposits he sees beneath it the 
 surface of another, which may or may not have been 
 eroded previous to the deposition of the one thus re- 
 moved. If it has not, he views its full extension, marks 
 its gradually thinning boundaries, defined probably by 
 lines of cliffs and of conglomerates, the ancient beaches ; 
 if denuded, he sees the exposed edges of the eroded 
 strata, cut through by ancient valleys, and in places 
 outliers only remaining to mark its former extension. 
 Some parts of the old surface may be covered by sheets 
 of lava, intersected by volcanic dykes, or perhaps dislo- 
 cated by faults in every direction. He notes also the 
 gradual approach of those variations in the conditions 
 of sea, land and climate which ultimately lead to the 
 deposition of the succeeding formation, and which drive 
 before them, slowly but inevitably, the existing forms of 
 life and bring in new races of inhabitants. 
 
 When the mind has grasped such facts as these, facts 
 supported it may be by strongest evidence, the aim and 
 end of our geological research has been mainly achieved. 
 We can not always hope to carry our inductions to the 
 extent here indicated, but it may done with very fair 
 probability of accuracy within reasonable limits. And 
 it is to this kind of knowledge that Geology must look 
 for its practical result, in the assistance that it affords 
 to mining, engineering, quarrying, and well-boring ope- 
 
216 FIELD GEOLOGY. 
 
 rations, although it cannot be denied that the scientific 
 gain in itself possesses the greatest attraction. 
 
 To work out a very simple problem of the kind, let 
 us take the small tract surveyed in Part I., showing 
 Reading-beds, Chalk, Upper Greensand, and Gault ; the 
 last being, within the area, the lowest formation. Ke- 
 move all the others and we shall see a tract of sea- 
 bottom, on which "stone-lilies" grow and Nucula 
 pectenata flourishes; their remains being eventually 
 entombed in the increasing sediment. But the area 
 is slowly rising, and as the water decreases in depth 
 the animals migrate seawards, and others whose habitat 
 is shallow water gradually come in. One part of the clay, 
 beyond the map, is already well above the water, and the 
 new kind of sediment, sand, thins out against the some- 
 what denuded barrier the animal remains washed from 
 out the Gault being reburied with those belonging to the 
 Upper Greensand. 
 
 The land again goes down, and continues sinking 
 for a lengthened period, during which the Chalk, with 
 its deep-sea fauna was slowly deposited. The Chalk was 
 formed in two divisions, upper and lower, with pro- 
 bably a denudation between; the upper part had de- 
 posited w r ith it and disseminated through its mass a 
 large amount of silica ; this afterwards segregated 
 itself and closed in as ifc were upon any organic frag- 
 ments containing silica, and thus formed the flint 
 concretions. Then began a long period of denudation 
 which wasted the Chalk, and left many flints upon its 
 surface embedded in the resulting stratum of clay, 
 noted at the base of the Eeading-beds in the sections. 
 This was succeeded by the deposition of the shallow 
 
FIELD GEOLOGY. 217 
 
 water and fluviatile Eeading-beds, which thin out 
 against the higher part of the Chalk, and rest uncon- 
 formably upon that formation. 
 
 Very great and important generalisations in geology have 
 been made from scientific observation of the character 
 and mode of occurrence of beds at distant points, bringing 
 all apparently discordant features into one harmonious 
 whole, with sometimes grand and unexpected results. 
 As an example may be cited Professor Prestwich's 
 arguments in favour of obtaining a supply of water 
 for London from the Lower Greensand.* These affirm 
 the probable existence of that formation beneath the 
 metropolis, in a water-bearing condition, and are based 
 upon the physical conditions of its outcrop many miles 
 away from the point in question. The conclusions 
 have been amply justified so far as the reasoning is 
 concerned, and although the Lower Greensand has not 
 been found under London, it is owing to what may be 
 called an accidental circumstance, which has, however, 
 given rise to another important generalisation. That is 
 the underground extension of a ridge of Palaeozoic 
 rocks which rise up sufficiently high to reach the Gault, 
 and thus to cut out the Lower Greensand, that other- 
 wise must have been there.*f- 
 
 The Secondary rocks were, of course, deposited in a 
 fairly level position, and in this area have not since 
 been subjected to much disturbance. They should 
 consequently be found, when not thinned out, in regular 
 sequence ; and if a tract of high ground existed in the 
 
 " Water-bearing Strata of the London Basin." 
 
 f " Account of the Kentish-town Well-section." Prestwich : 
 Quart. Jour. Geol Soc. vol. xii. p. 9. 
 
218 FIELD GEOLOGY. 
 
 area of their deposition, the beds must abut on the 
 flanks of such elevation. Also if such high ground 
 consists of the lower part of any series, the upper 
 members should also be found on either flank, with 
 their denuded edges covered by the newer formations. 
 Mr. Godwin-Austen has shown that if the rock under- 
 lying the Gault beneath London be, as it probably is, 
 Old Eed Sandstone, then the Coal-measures, the New 
 Eed Sandstone, &c., must occur on either flank of the 
 anticlinal that has brought it up to that position. That, 
 in fact, the ridge is part of an extension of the South 
 Wales anticlinal to that of Belgium, therefore the Coal- 
 measures must occur on either flank, and will probably 
 be found, as in those areas, at a moderate depth, unless 
 removed by an ancient denudation. 
 
 The way in which geological knowledge and reasoning 
 may be turned to practical account is shown also in the 
 two following sections on Water-supply and Soils 
 selected from many subjects upon which their bearing 
 is of great importance. 
 
 WATER-SUPPLY, &c. 
 
 An improvement in the water-supply of a district is 
 one of the practical results that may be expected to 
 arise from the working out of its geological structure 
 that is, from the knowledge obtained of its rocks and of 
 their relation to each other. The phenomena of springs 
 and the sources of supply to artesian wells are so 
 entirely dependent on stratigraphical and physical 
 features that an acquaintance with their principles can 
 not fail to be of use to the student of " Field Geology." 
 
FIELD GEOLOGY. 219 
 
 The subject may "be advantageously divided into 
 three sections : 
 
 1. Origin of the supply. 
 
 2. Streams and springs. (Natural founts.) 
 
 3. Wells. (Artificial founts.) 
 
 1. Origin of the Supply. The original source whence 
 is derived all our supply of water whether it come to 
 our hand through natural or artificial founts is, of 
 course, the " Eainfall." This varies every year and in 
 every locality, but is always and everywhere (with rare 
 exceptions) much in excess of what is actually neces- 
 sary to the population. Then, it may be asked, " how 
 is it that our supply ever seems likely to be unequal 
 to the demand ?" The answer is simple. We do not 
 economise that derived from the natural founts, and we 
 do not sufficiently avail ourselves of the artificial founts, 
 which are at all seasons practically inexhaustible. The 
 following statistics, concerning England, will help to 
 elucidate the matter. 
 
 Thirty gallons per day or 50 tons per year is the 
 average quantity required for each head of the 
 population. One inch of rainfall to one acre is 
 equal to 100 tons. There are 1J acres to each 
 head of population. 
 
 Therefore a quantity equal to a rainfall of only one- 
 third of an inch is sufficient for the requirements of 
 the population. 
 
 The minimum Eainfall is about 27 J inches. The 
 average Eainfall is about 34 inches. In dry 
 years (in some localities) it has been but 16 
 inches. In wet years (in other localities) it has 
 been even so high as 20 feet. This excessive 
 
220 FIELD GEOLOGY. 
 
 rainfall occurred in the Lake District, in 1872 ; 
 in the Southern and Eastern counties, in the 
 same year, it was 27 inches. The rainfall of 
 1872 was 36 per cent, above, and of 1870 18 per 
 cent, below the average. 
 
 One very large portion of the rainfall runs away in 
 rivers to the sea ; another is given back again by evapo- 
 ration. But in every year and in every locality there 
 remains, as stated above, a quantity which, economised 
 and utilised, would be much in excess of our require- 
 ments. And this quantity finds its way into the hidden 
 recesses of the earth, to be given or drawn forth from 
 the natural and artificial founts described in the follow- 
 ing sections (2 and 3). In proportion to the size of the 
 collecting area will be the quantity, and according to 
 the nature of the strata through which it passes will be 
 the quality of the water supplied. 
 
 2. Streams and Springs. The water-supply of a 
 district is not, by any means, necessarily proportionate 
 to its rainfall. So much depends upon its physical 
 geography, its height above the seaj and especially upon 
 the nature of its soils, subsoils, and underlying strata. 
 So far as natural founts are concerned, the valleys will 
 be better off than the hills, and the low-lying districts 
 than those of greater elevation ; while permeable soils 
 and subsoils receive, and for a while retain, a much 
 larger quantity of water than do those that are imper- 
 meable. For, as the rain falls on the ground, it is 
 drawn by the law of gravitation to a lower level ; if the 
 surface be impervious, it runs off by the ditches and 
 rivulets to the larger rivers, and thence to the sea. If 
 the surface be wholly or partly pervious, a portion only 
 
FIELD GEOLOGY. 221 
 
 runs to the rivers, the rest being absorbed by the water- 
 bearing strata, and again thrown out at a lower level, in 
 the form of springs, on the hill-sides ; or, the conditions 
 being favourable, it is retained by those strata at various 
 depths, which thus are constituted huge underground 
 reservoirs. (Section 3.) 
 
 The supply from the natural founts will vary as the 
 seasons ; in periods of drought the streams run dry, and 
 the springs fall off, while shallow wells, which derive 
 their water either by soakage from a stream or from a 
 so-called land-spring, become exhausted in consequence. 
 Neither streams nor springs should be depended on for 
 a supply of water, not only on account of their inter- 
 mittent nature, but because of their liability to pollu- 
 tion. 
 
 The strata that now throw out springs would, if 
 occurring at a different level or if inclined at a suitable 
 angle, become the means of draining water from the 
 surface, and the springs of one locality are, in fact, but 
 the natural drainage of another. 
 
 3. Wells. This section involves the " theory of 
 springs," and relates to artesian or deep wells and 
 borings, and it may be illustrated by performing in 
 imagination a simple experiment. Take two shallow 
 dishes and place one on the other with a thin layer of 
 sand between them ; pour in water at one edge of this 
 layer, and it will be found that in a very short time the 
 sand is saturated alike throughout. A portion of the 
 water has, in fact, first descended by gravitation under 
 the centre of the upper dish, then risen to the other 
 edge of the sand, through the force of hydrostatic pres- 
 sure, to the same level as that at which it entered. A 
 
222 FIELD GEOLOGY. 
 
 hole being bored in any part of the upper dish the water 
 will rise through that hole until it stands at the same 
 level. If the upper dish were filled with clay or any 
 other impervious material, and a hole were bored 
 through, the water, of course, would rise in the hole in 
 a similar manner. 
 
 Here are all the phenomena of deep-seated springs 
 and artesian wells. For what occurs on a small scale 
 in the sand confined between the dishes occurs in 
 nature in pervious strata confined between those that 
 are impervious, and the water rising in the hole re- 
 presents exactly an artesian well. The water-bearing 
 bed may be not absolutely continuous, but the same 
 results will follow so far as the continuity be unbroken; 
 or there may be outlets at a lower level than the out- 
 crop, when perennial springs are the result. These 
 springs affect the main supply in the same proportion 
 only as the discharge from them bears to the amount of 
 rainfall received at the outcrop. 
 
 When a boring is made at a place situated at a level 
 lower than that of the outcrop of the water-bearing 
 stratum, the water rises above the surface ; this is the 
 case at several deep wells in the valley of the Lea, sunk 
 down to beds of sand and pebbles which come to the 
 surface at a higher level several miles to the north- 
 ward. 
 
 It follows that when all the conditions of dip, permea- 
 bility, and continuity are known, it becomes a matter 
 not of speculation but of certainty to estimate the depth 
 at which water will be found, and the height to which 
 it will rise in the well. 
 
 It may be repeated that the water-supply of a district 
 
FIELD GEOLOGY. 223 
 
 is not by any means proportionate to its rainfall. The 
 water-bearing beds are great distributors, and by them 
 the supply is to a great extent equalised. The supply 
 to be obtained by boring down to deep-seated springs 
 is practically inexhaustible > being scarcely, if at all, 
 affected by drought, and these springs form the only 
 source on which can be placed a full reliance. 
 
 SOILS. 
 
 All soil or mould has been produced during the lapse 
 of many ages by the disintegration arising chiefly from 
 the action of rain, frost, and other atmospheric influences 
 of the exposed surface of the strata which form the 
 base or subsoil. It has been increased in depth by the 
 annual growth and decay of vegetable matter, assisted 
 by the apparently trifling, but still ceaseless, action of 
 earthworms, working into and turning up the subsoil. 
 It is thus evident that the nature of the soil of a district 
 must strictly depend on that of the subsoil from which 
 it is directly derived, and as the strata, or rocks, forming 
 the subsoil, present many varieties, they give rise to 
 subsoils and soils that differ in a corresponding degree. 
 
 The composition of soil is very variable is greatly 
 dependent on that of the subsoil, by the decomposition 
 of which it has been formed and bears to the subsoil 
 a nearly constant relation. An average soil consists of 
 silica, alumina, lime, magnesia, oxide of iron, small 
 quantities of ammonia, carbonic acid, and alkaline and 
 earthy salts, with a portion of decaying organic matter. 
 The nature and fertility of the soil varies as these con- 
 stituents are present in a greater or less degree, all 
 being to some extent necessary for the proper develop- 
 
224 FIELD GEOLOGY. 
 
 ment of plants, but some, in excess, are injurious to 
 vegetable growth ; for instance, soils containing much 
 sulphate of iron are invariably unproductive. 
 
 A base of gravel produces a light soil abounding in 
 silica that substance not unfrequently forming more 
 than four-fifths of its whole weight and which varies 
 from a fine sandy mould to a stony soil as the particles 
 of the gravel beneath are in size fine and uniform or 
 coarse and irregular. Sand makes a similar but some- 
 what finer soil. Clay gives rise to a stiff, heavy, and 
 sometimes tenacious soil, consisting mainly of alumina, 
 varying in quality and appearance perhaps more than 
 any other kind, but being generally more productive. 
 
 The nature of the subsoil itself also bears to the 
 geology of a district a relation equally constant. The 
 subsoil of any locality situated on a formation of reason- 
 able thickness must partake of the nature of that for- 
 mation, whether it be Lime, Sand, Clay, or any other 
 rock. And this applies not merely regarding those 
 substances as generally understood, but also when they 
 occur in a compact state, as Lime stone, Sandstone, Shale, 
 &c. Therefore, the geology of a place being known, the 
 subsoils and soils are more or less understood. 
 
 There are certain other natural causes which modify ? 
 to some extent the nature of soil ; the results of the 
 influence exerted by these causes being comparatively 
 small, but economically important. They are 1. The 
 rain-wash, which removes the particles of soil from 
 higher to lower ground. In a flair country the effects 
 of this action are not very perceptible; but where 
 the surface is broken by hills ' and small valleys, accu- 
 mulations, several feet thick, may often be seen. Also, 
 
FIELD GEOLOGY. 225 
 
 where the downward progress of rain-wash on a hill- 
 side has been arrested by a fence, its result is after a 
 few years very evident, in the ground being unduly 
 higher on the upper than on the lower side. 2. The 
 annual growth and decay of vegetation, which is the 
 most important of the modifying causes. The plants 
 that have lived and died upon the soil, from the time 
 when the first thin layer was formed on the exposed 
 surface of the subsoil, have all (minute as they are in 
 many instances) performed a useful part, by absorbing 
 from the air carbonic-acid, water, and ammonia. They 
 yielded to the soil, by their own decay, these substances 
 which form its organic constituents. The proportion of 
 decaying vegetable matter in soils is usually small 
 about one-fiftieth but sometimes it is excessive as in 
 peat and the soil rendered thereby almost worthless 
 for purposes of cultivation. 3. The matter derived 
 from animals living on, above, and beneath the surface, 
 and from their ultimate decomposition. All wild 
 creatures birds included thus naturally contribute to 
 the fertility of soil, to an extent perhaps much larger 
 than is generally appreciated. 
 
INDEX. 
 
 ALLUVIUM, mapping, 23, 27 
 Animal kingdom, re view of, 126 
 Arrangement of collections, 149 
 
 BAROMETER, aneroid, 64 
 Bench-marks, 63 
 Blow-pipe, 98 
 
 Books of reference, 117, 146 
 Boundaries, tracing, 13 
 
 , examples of, 17 
 
 Boundary lines, 13 
 Breaking stones, 91 
 Breccia, 90 
 Brick-earth, 90 
 
 CABINET specimens, 121 
 Casts of fossils, 131 
 Chain, 76 
 Characteristic fossils, 157 
 
 1 H s t of, 159 
 
 , species, 152 
 
 Chemical analysis, 117 
 
 Clay, 89 
 
 Clinometer, 40 
 
 Collecting fossils, method of, 133 
 
 Collections, arrangement of, 149 
 
 Compass, pocket, 7 
 
 , prismatic, 8 
 
 , use of, 8 
 
 Concretions, 118 
 Conglomerate, 90 
 Contour lines, 6, 15 
 maps, 6 
 
 DATUM-LEVEL, 62 
 Denudation, remarks on, 35 
 Determination of rocks, 94 
 
 , table of 
 
 tests for, 100 
 Dip, 38 
 
 , to ascertain, 41 
 
 , to find amount of, 45, 49 
 
 , to find direction of, 42, 49 
 
 Dip, apparent, 42, 84 
 
 , example of, 210 
 
 , to find, 84 
 
 , depth and thickness, table 
 
 of, 50 
 
 Downthrow, 209 
 Drift deposits, 34, 36, 37 
 , mapping, 35 
 
 EFFERVESCENCE, 94 
 Eruptive rocks, 213 
 
 FALSE-BEDDING, 89 
 Fault, mapping, 207 
 Fossils, casts, 131 
 
 , characteristic, 157 
 
 , list of, 159 
 
 , impressions, 131 
 
 , method of collecting, 133 
 , mode of occurrence, 129 
 
 , naming of, 145 
 
 , nature of, 125 
 
 , preservation of, 144 
 
 , replaced, 130 
 
 , unchanged, 130 
 
 Fracture, 93 
 
 GENERALISATION, 214 
 General propositions, 14 
 Geological mapping, 5 
 
 sections, 38 
 
 Geology, filling in to sections, 84 
 Glacial deposits, 34 
 
 , mapping, 35 
 
 Gravel, 36, 90 
 
 , pipes of, 56 
 Grit, 90 
 
 HAMMER, 10 
 Hardness, 94 
 
 , scale of, 95 
 
 Height of cliff, to ascertain, 79 
 Heights above the sea, 62 
 
INDEX. 
 
 227 
 
 Homotaxis, 152 
 IMPRESSIONS of fossils, 131 
 
 LABELS, 121 
 Level and staff, 68 
 Level-book, 71, 79 
 Levelling, 64 
 
 , by aneroid barometer, 64 
 
 , by level, 67 
 
 , by theodolite, 74 
 
 Lines of boundary, 13 
 
 of out-crop, 13 
 
 Lithology, 87 
 Loam, 90 
 
 Lodes, mapping of, 214 
 Lustre, 93 
 
 MAGNETIC variation, 7 
 Maps, 5 
 
 , contour, 6 
 
 Mapping drifts, 35 
 
 eruptive rocks, 213 
 
 fault, 207 
 
 , geological, 5 
 
 older rocks, 202 
 
 example of, 203 
 
 Marl, 90 
 Marl-slate, 90 
 Memoranda, 28 
 Metals, 114 
 
 Metamorphic rocks, 120 
 Microscope, 115 
 
 NAMING of fossils, 145 
 Nomenclature, 145 
 Notes of sections, 53, 206 
 
 ORES of the metals, 114 
 
 PAL.EONTOLOGICAL evidence, 
 practical bearing of, 154 
 
 , value 
 
 of, 150 
 
 Palaeontology, 122 
 
 Pick, 10 
 
 Pipes, 56 
 
 Plotting from angles, 81 
 
 from heights, 74 
 
 Pocket compass, 7 
 
 Preservation of fossils, 144 
 
 Prismatic compass, 8 
 
 Propositions, general, 14 
 Protractor, 9 
 Pudding-stone, 90 
 
 REACTIONS in the wet way, 97 
 Reference, books of, 117, 146 
 Review of Animal Kingdom, 12G 
 Ripple-mark, 90 
 River-alluvium, mapping of, 23, 
 
 37 
 Rocks, determination of, 91 
 
 -, table of tests for, 100 
 
 -, eruptive, 213 
 
 -, metamorphic, 120 
 
 -, older, survey of, 202 
 
 SAND, 89 
 Sandstone, 90 
 Scales, 12 
 
 Sections, exposed, 52 
 , geological, 38 
 
 , horizontal, 61 
 
 , notes of, 53 
 
 , vertical, 211 
 
 Shale, 89 
 
 Slate, 89 
 
 Slickenside, 58, 119 
 
 Soils, 223 
 
 Species, characteristic, 152 
 
 Specific gravity, 96 
 
 Specimens, 91, 121 
 
 Spud, 10 
 
 Springs, theory of, 221 
 
 Streak, 96 
 
 Streams and springs, 220 
 
 Strike, 39 
 
 Structure, 92 
 
 Supply of water, 218 
 
 Symbols, 32 
 
 of Geol. Survey, 33 
 
 TESTS, table of, for determination 
 
 of Rocks and Minerals, 100 
 Texture, 92 
 
 Theodolite, levelling by, 74 
 Tracing boundaries, 13 
 Traversing, modes of, 30 
 
 VEINS, mapping of, 214 
 Vertical section, 211 
 
 WATER-SUPPLY, 218 
 Wells, 221 
 
ERKATA. 
 
 Page 15, line 18, for any read all. 
 
 ,, 17, ,, 18, for two slips read slips. 
 24, (fig. 7), for T read 3. 
 ,, 25, line 19, for hollow read hollows. 
 ,, 28, ,, 10, for prove read proves. 
 ,, 33, lines 22, 25, for moiitonnees read moutonnees. 
 ,, 70, line 7, for will then be read will have been. 
 71, for Top of Church Escarpment read Top of Chalk Escarp- 
 ment. 
 
 ,, 82, line 4, after transferred insert by parallel rule. 
 ,, 87, insert footnote :* Metals and Minerals, as constituents of 
 Rocks, are, for convenience sake, included under this. 
 . heading, Lithology. 
 ,, 94, line 6, omit its. 
 
 ,, 155, ,, 12, insert if between the words while and these. 
 ,, 156, ,, 4, for trelobites read trilobites. 
 5> for lingula flags read Lingula flags. 
 
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