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I— Development of Chr^sotile, from the incipient (a) to the completed state (rf); showing the origin of the "proper wall "of "Eozoon '.(Dicigram). Y\c.2.-£o:ioon Canadense" from Ottawa, Canada, showing the following changes ! chrysotile(b)into"properwaH"(d),and floo- cilent serpentine (c)into"canal sjrstem' (cx). Fig. s-Lamellar graphic granite from Tarbert, Hebrides : its lamellar and fibrous structures are considered tc be organic by £oBoorusts . PinxW.K Hauhart Iith. IX , i • ! Ui \VrFH ilrCORI) V. \i - ( , 1 V ^HM^ !n SM 'N \^'i\.S \S . \\ < N'^' -.]A ■ I'. Vit : ' 'rv'[t>:»K-rt'- i.->w ith Pit s ' ' ' , ' i~\„ c > 1 * 'J j ^' .. '^■-^:*' .;," ',-? • V .T ^, - ^. . "r^;- .' . s ; -•e' /> ^=' ^^"7^^^■''^; .^ . . ^ , , , , c'l AN OLD CHAPTER OP THE GEOLOGICAL RECORD WITH A NEW INTERPRETATION: OB. 11 OCK-MET AMOR PHIS M (ESPECIALLY THE METHYL08ED KIND) AND ITS RESULTANT IMITATIONS OF ORGANISMS. WITH AN INTRODUCTION GIVING AN ANNOTATED HISTORY OF THE CONTROVERSY ON THE SO-(JALLED EOZOON CANADENSE," AND AN APPENDIX. (( BY Professors W. KING, Sc.D. etc., AND T. H. ROWNEY, Ph.D. etc., OP THE queen's college, GALWAY, and the queen's UNIVBBSITV in IRELAND. • N * , • • I • • • • I • •■*•• • ••• • * # * ■ ' • • •*. . • • •. ■ ■ • • ; • • . ■ '• ' \ .». • ••• • '•- ' ; ::.LOTSrD5&:N'i : .• JOEN van'Voorst,*! 'paternoster row. MDCCCLXXXI. ALERE I FLAMMAM. PRIJTTED BY TAYLOR AND FRANCIS, RED LION COUKT, FLEET STREET. - t. I '« « » o I ( « • « ff • • I I t :'■..• CONTENTS. Pages Preface v-viii Introduction ix-lvii Chapter I. The different Kinds of Kocka treated of II. The Mineral Choracters of Opliitos and related Hocks . . III. Structural Characters of Ophites and related llockg .... IV. Origin of certain of their Mineral, Structural, and Che- mical Characters V. Mineralized and Methylosed Metamorphic Rocks VI, Why some Metamorphic Rocks have been Mineralized and others Methylosed VII. Mechylotic Origin of Ophites VIII. Serpentinization effected in certain Deposits without the intervention of Mineralization IX. Many Ophites were Sediments, and others Igneous Rocks originally X. Methylotic Origin of Hcmithrencs and other related Cal- citic Rocks XI. On the Origin of the Minerals characteristic of Ophites and related Rocks— of Peridote in particular XII. On the Origin of the Archa;an " Crystalline Limestones " of Canada ... . . a 2 1-3 4-7 8-11 12-27 28-33 34,35 3G-42 43,44 45, 4G 47-5J) 60-71 72-82 :i6o \. IV CONTENTS. Chapter Fagm XIII. Why aro Limestones comparatively rare in the Forma- tions immediately succeeding the ArchsDans ? .... 83-88 XIV. Some Crystttlline Limestones have been simply Minera- lized 89, 90 XV. Dolomites and Dolomitic Hocks have undergone Mcthy- losis 91-95 XVI. Tho Chrono-Geological Range of Ophites and related llocks, ftnd tho Ago of their Methylosis 96, 97 APPENDIX. Thalassa and Xera in tho Permian Period 99-lOG Supplementary Note A. — Rock-jointing in relation to Pheno- mena in Physical Geography and Physical Geology. . . . 107-117 Supplementary Note B. — On the Crystalline Bodies of tho Sunderland Permian Magnesian Limestone 118, 119 Supplementary Note C. — Certain Limestones are of Mecha- nical Origin 120, 121 Description of tho Plates 123-126 Index 127-142 rEEFACE. Since the publication of Bischof's 'Lclir^^ucli der chemischeo mid physikalischen Geologic^ (1847-54), seldom has any thing excited more sustained interest among geologists than the ques- tion as to the nature and origin of metamorphic rocks. At the Paris Exhibition, in 1878, an International Cougres;^, comprising many eminent geologists, was convoked, one of the main objects of which was to consider the problem of metamorphism. Ee- searches having the same purpose in view have been promoted by grants from the Government Scientific Research Fund at the recommendation of the Royal Society, and from the British Association. Some sixteen years past the alleged discovery of the so-called "Eozoon Canadense " gave a marked impetus to the study of metamorphic geology ; and of late years microscopic observations on metamorphosed rocks and their component minerals have been seuulonsly pursued. The result of all this is that a vast body of evidence has been gathered together, throwing much new light on the subject in question. Nevertheless, if the latest exposition of rock-metamorphism is to be taken as correctly representing its present state, the subject, it would rather appear, has all along been stagnant, having made no progre:^^3 since LycU began to write on it — more than forty years ago ! Dr. Ramsay, in his Address lately delivered at Swansea as President of the British Association, declares, without any reservation, that in metamorphic rocks " there is little or no development of new material ;" and he I <■ VI PREFACE. accordantly maintains tliat they have been simply mineralized ' — " sandstones Lave been converted into qnartzitcs/' and so on, — using almost the same terms as Lyell did, and after the lapse of nearly lialf a century. This latter-day exposition of mctamorphism, the writers feci, affords indubitable proof that the present work is imperatively called for to meet the requirements of a large body of geological students. Having laboured at the subject for fifteen years (aided to some extent by a grant from the Government Fund) , they have determined the existence of two strongly diflPerentiated groups of metamorphic rocks — mineralized and methylosed. They are also enabled to show that the characters of the latter group have been developed by the decomposing action of carbonated solutions on siliceous minerals ', that essentially silacid rocks, which have been permeated by solvents of the kind, have be- come variously transmuted and transformed — in the one case having had their mineral silicates for the most part replaced by mineral carbonates (calcite &c.), — in the other the same siliceous minerals, where simply affected by partial erosion and replacement, having become shaped into a variety of residual configurations that have been mistaken for organic structures, as in " Eozoon Canadense." Moreover the above pheno- mena enable the writers to show that both bedded and dyke- shaped masses on a large scale exhibit corresponding chemical changes ; so that what were once essentially siliceous rocks are nou" ophites, hemithrenes, and the like, — in which it cannot be said that " there is little or no development of new material," and which, in short, clearly prove that there are numerous other metamorphic rocks besides those that are simply mine- ralized. Just before the " creature of the dawn " made its advent, mineral pseudomorphism was labouring under great bewilder- 1 PREFACE. Vll ment. The opinion on the subject, which had been founded on the researches of Blum, Bischof, Rose, and others, was encounter- ing more or less hostility from Scheerer, Naumann, Delesse, and Sterry Himt. The pseudomorphic origin of serpentine, which had been strongly contendec^ for by the first group of scientists, was uncompromisingly opposed by certain of the latter, espe- cially Sterry Hunt, who, with the fact before him that this mineral occurs, forming vast rock-masses, amongat the old strati- fied crystalline deposits (Archseans) of Canada, unhesitatingly declared it to be neither pseudomorphic, nor metamorphic, but a crystallized precipitate, chemically thrown down by the primaeval ocean. At last "Eozoon Canadense " appeared on the scene. Chiming in to some extent with Sterry Hunt's " novel doctrine," it was at once enthusiastically accepted by the highest authorities in geology as resolving the vexed question attaching to serpentine and some other Archaean problems ; at the same time it was held up before the eyes of a wondering and con- fiding world as the first-born of life on our planet — protoplasm in vast flakes invested with a calcareous covering, and rivalling coral reefs in magnitude ! It will be our object in the following pages to show that both doctrines are absolutely fallacious. r INTRODUCTION. The first announcement in connexion with the subject of " Eozoon" was made by the late Sir Wm. E. Logan, Director- General of the Geological Survey of Canada, in his Report of the year 1858. Sir Wm. E. Lngan exhibited at the Meeting of the American Association for the Advancemc. t of Science at Springfield, in August 1859, some Stromatopora-like specimens (noticed in the above Report) trora the Grand Calumet and Perth (Canada), which he was " disposed to look upon as fossils ^^*. Report of the Geology of Canada, 1863. Sir W. E. Iiogan. In this Report (pp. 48, 49) the discovery of specimens, supposed to be fossils, is noticed as having been made "by Mr. J. M'MuUen, of the Canada Geological Commission, in the crystalline limestone of the Grand Calumet (river Ottawa), which present parallel or apparently concentric layers, com.- posed of crvitalline pyroxene, while the interstices are filled with crystalline carbonate of lime. Dr. James Wilson, of Perth, found loose masses of limestone near the same place containing similar forms — the layers composed of dark green concretionary serpentine, while the interstices are filled with crystalline dolomite. If both are regarded as the results of uraidcd mineral arrangement, it would seem strange that identical forms should be deriyed from minerals of such difl'erent * Quarterly Journal of tho Geological Socioiy, vol. xxi. p. 48. 1858. 1850. 1803. X INTRODUCTION. composition. If the specimens had been obtained from the altered rocks of the Lower Silurian series, there would have been little hesitation in pronouncing them to be fossils." 18G4. American Journal of Science, March 1864?, p. 273. Sir W. E. Logan announced that Dr. Dawson had discovered in the Canadian ophite structures which it was decidedly his belief were organic and foraminiferal. 18G4. On the Occurrence of Organic Remains in the Laurentian Rocks of Canada. By Sir W. E. Logan, F.R.S., F.G.S. ; with Communications by J. W. Dawson, LL.D, P.R.S,, on the Structure, and by T. Sterry Hunt, F.R.S., on the Mineralogy of the same remains. Paper read at the Bath Meeting of the British Association, September 1864. 1864. On the Structure of certain Organic Remains in the Laurentian Limestones of Canada. Dr. J, W. Dawson. Q. J. G. S. vol. xxi. pp. 51-59. 18C4. Additional Note on the Structure and Affinities of Eozoon Canadense. Dr. W. B. Carpenter. Op. cit. pp. 59-6G. Both writers assumethatthe calcareous ordolomitic layers of the specimens brought under notice by Logan constitute the skeletal portion of "Eozoon Canadense," and that the siliceous layers, whether terpentine, white pyroxene, or loganite, are casts of its cells or chambers. Dawson, having detected branching configura- tions and rods or plates in the " skeleton," and taking them for casts of canals and sto)ons, identified them with the canal system and stolons of a foraminiferal organism ; and Carpenter, observing a fibrous lamina often si^rrounding the " chambers," pronounced its fibres to be casts of tubuli such as characterize the proper wall of a nummuline foraminifer. The serpentine layers frequently present themselves more or less excavated and divided ; but often they arc broken \i\) into short plates and detached spheroids iiMC- gularly lobulatcd. The presumed organism in the former case is INTRODUCTION. XI said to be tho " laraellated/^ and the latter the " acervuline " varietv. On the Occurrence of Organic Remains in the Laureutian Rocks of Canada. Sir W. E. Logan. Q.J.G.S. vol. xxi. pp. 45-50. On the Mineralogy of certain Organic Remains from the Lau- rentian Rocks of Canada. Dr. T. Sterry Hunt. Op. cit. pp. 67-71. On the Structure and AflSnities of Eozoon Canadense. Letter to the President of the Royal Society. Dr. W. B. Carpenter. Proc. Roy. Soc. vol. xiii. pp. 545-549. Geological Magazine. Vol. ii. pp. 87, 88, Dec. 37, 1864. Announcement by Mr.W. A.Sand£ord,F.G.S., of his discovery of "Eozoon Canadense" in Connemara marble from the Bina- bola Mountains; which "T. R. J.," at the same time, announced he had " verified by experiment." " The various formed cham- bers, the shell of varying thickness, either very thin and traversed with fine tubuli, the silicate filling which (when bared) resembles white velvet-pile, or thick and traversed with brush-like threads, representing the pseudopodian passages of the ' supplemental shell' (or 'vascular system'), are all preseni." "Appendix" to a reprint of Dr. Dawson's Memoir (a.d. 1864) in Canadian Naturalist, April 1865. Dr. Dawson, who had previously observed " traces of organic structure in the Connemara marble, but not in so far as can be made out of the character of Eozoon" declares that "it is gratifying to find in recent British publications notices to the effect that Mr. Sandford has found the structure of Eozoon in the Laurentian limestones of Ireland." On the Structure, Affinities, and Geological Position of Eozoon Canadense. Dr. W. B. Carpenter. Intellectual Observer, vol. vii. On the oldest known Fossil, Eozoon Canadense y of the Lauren- tian Rocks of Canada; its place, structure, and significance. Prof. T. Rupert Jones. Popular Science Review, vol. iv. 1864. 1864. 1864. 1864. 1866. 1805. 1866. XU INTRODUCTION. 1866. The following letter appeared in the 'Reader,' June 10, 1865, p. 660 :— " TTie Eosocn Canadense. " Queen's College, Galway, June 3, 18G5. "We beg permission to publish the following statement through the medium of your widely-circulated Journal : — " For several weeks past we have been engaged in investigating the microscopic structure of the serpentine of Connemara in comparison with that of a similar rock occurring in Canada, which has attracted so much attention of late. For a consider- able portion of the time we entertained the opinion, in common with Sir William Logan, Drs. Dawson, Sterry Hunt, Carpenter, and Professor Rupert Jones, that the Canadian serpentine is of organic origin, the result of the growth of an extinct foraminifer called Eozoon Canadense ; it was also our belief for a while that the Connemara rock had originated from a similar organism. Gradually of late, however, we have been reluctantly compelled to change our opinions. " It is now our conviction that all the parts, in serpentine, which have been taken for the skeleton-structures of a forami- nifer are nothing more than the efiFect of crystallization and segregation. "It would have given us unalloyed pleasure, had we been able to state that our investigations had confirmed those of the eminent authorities to whom reference has been made, as it was purely in this spirit that we commenced our labours ; and also, we may observe, with the desire to ascertain if the serpentine of Connemara and the other rocks with which it is interstratified, belonged to the Laurentian period, ** We purpose at an early opportunity to lay before the public all the evidences and considerations which bear us out in our present opinion. " We are. Sir, yours very truly &c., " William King, Professor of Mineralogy and Geology. "Thomas H. Rowney, Ph.D., Professor of Chemistry." INTRODUCTION. Xlll "The Eozoon Canadense." A letter, signed "William B. Car- 18G5. - penter," appeared in a following number of the ' Reader/ The writer asserts that the " conformity " between " Conne- mara serpentine " and " that of the least characteristic part of the Canadian fossil " is " so close as to leave no doubt in my mind as to the organic origin of the former." Next, he makes a characteristic personal attack on the writers of the preceding letter, " advisedly " remarking on the " audacity " of the one in presuming to dispute the organic origin of Eozoon, and impliedly charging the other with incompetency. A short reply, signed " William King," appeared in the next number of the ' Reader'^. The Cambrian Rocks of the Briti&h Islands. W. Hellier Baily. 18G5. - Geological Magazine, vol. ii. p. 388. Mr. Bailey expresses his doubt that " Eozoon," " the thing 18G5. in question, was a fossil at alP' (Joum. Geol. Soc. Dublin, vol. i. N. S.). " Eozoon " having been brought under the notice of the Geo- 1865. logical Section of the British Association, held in Birmingham of this year. Professor R. Harkness declared his disbelief in it ('Reader,' Sept. 30, 1865). On the so-called " Eozoonal Rock." Professors W. King and 18GG. T. H. Rowney. Q. J. G. S. vol. xxii. pp. 185-218. In this memoir evidences are adduced to show that the " cal- careous skeleton" and the "chamber casts" of "Eozoon Cana- dense " stand in the same relation to each other as the calcitic matrix and its included mineral silicates in a number of rocks, — that the lamellated and the acervuline varieties are strictly paral- leled, the one by a rock in Scandinavia consisting of alternating layers of calcite and a hornblendic mineral, the other by cocco- litic marbles of Tyrol, Delaware, and elsewhere, — that the ♦ Another letter, dated July 24, 18G5, on a subject arising out of our announcement, and introduced by Dr. Carpenter, was published in a suc- ceeding number. XIV INTRODUCTION. " canal system " is paralleled by ramose foliations of mctaxitc, and is analogous to the corailoids of the magnesian limestone common at Sunderland, — that the " proper wall " is a modifi- cation of chrysotile, — in short, that all the features diagnosed for Eozoon are of purely inorganic origin, resulting from chemical and structural changes in the minerals severally composing them. Previously to the publication of our paper no reference had been made by Logan, Dawson, Carpen';er, Stcrry Hunt, or Rupert Jones, in their respective writings on " Eozoon,^' to the presence of chrysotile in frequent association with this presumed fossil. In fact, serpentine in all its forms and relations was altogether ignored. At the time referred to, the subject of mineral pseudomorphism was in an extremely unsettled state. The opinion respecting it, as advocated by Blum and others, was being opposed by Scheerer, Naumann, and Delesse, and especially by Sterry Hunt, who was enthusiastically propagating his " novel doctrine " — the chemical precipitation of metaraorphic rocks ; so that the obvious facts connected with eozoonal features escaped being sufficiently examined from a mineral point of view. Moreover the origin of serpentine, one of the metamorphics in question, was equally a bone of contention — its protean character, both structural and chemical, its occurring indifferently as intrusive dykes and sedi- mentary beds, its playing a prominent part in what was taken to be the earliest sea-born organism of our planet, and the little then known with respect to chemical changes in rocks, all taken together, caused mineral pseudomorphism to be thrown into the background — to be repudiated as having any thing to do with the " creature of the dawn." In addition to other points introduced by Dr. S. Hunt in his memoir of 1864, and which are duly noticed in the following pages, he describes the mineralogy oi" Eozoon" from one of the specimens which first led Logan to suspect their organic origin. A specimen of the kind has been lately sent (April 1881) to us by Mr. R. Damon, F.G.S., who received it from Dr. I INTRODUCTION. XV fmg the lanic m) Dr. Dawson : it is labelled " Eozoon — special variety — mineralized with loganitc;" but no locality is mentioned. Hunt^s speci- mens were from Burgess, Canada. Their layers are of two kinds : one, " a somewhat ferriferous dolomite/' yielded on analysis "carbonate of magnesia 40*7, carbonate of lime, with a little per- oxide of iron, 59*0 =99" 7;" and the other, a dark green mineral silicate, called loganitc, yielded " silica 35*14, alumina 10*15, magnesia 31*47, protoxide of iron 8*60, water 14*64=100*00." It is consequently a hydrous alumino-magnesian silicate related to chlorite, and a true scrpentinous mineral (pp. 4, 5). The *" ' " ' loganite occurs in prismatic crystals, which, from ^ heir measurements, Dana does not hesitate to declare to be pseudo- morphs after hornblende. Serpentine is another mineral equally pseudomorphic after hornblende. Therefore the fact that both serpentine and loganite (which are alike pseudomorphic after the same mineral) form "chamber-casts oi Eozoon" affords no support to the presumed organic origin of these features. Besides serpentine and loganite, the mineral silicate referred to by Logan and Hunt under the name of " white pyroxene " also " occurs in immediate contact with a layer " of the former*. " White pyroxene," we have reason to consider, is another pseudomorph after either hornblende or augite ; so that, to some extent, it also invalidates the organic hypothesis. The specimen we have received from Mr. Damon does not quite agree with Sterry Hunt's. It is made up of two kinds of layers, not well defined, however, as such. The loganite, which forms one of the kinds, is in dark-green crystalloids, variously clustered together, and very seldom showing any traces of proper cleavage; as their "fracture is granular." The other layers have an opaque white colour ; but, instead of consisting of calcite or dolomite (miemitef), they are composed of what appears to be " white pyroxene :" imbedded in these layers are siliceous crystalloids of a pale-green colour, in which respect * Quart. Journ. Geol. Soc. vol. xxi. p. G7. t We find it advantageous to restrict the term dolomite to rocks, and apply that of 7niemite (one of the names in use) to their mineral representative. s; XVI INTRODUCTION. thpy appear to consist of serpentine. The crystalloids of " white pyroxene " are strongly aflPected with cleavage, which is more or less represented by open gashes — the openness of which is disclosed by an infilling of calcite : it frequently happens that the cleavage is imperfectly developed, especially when the mineral is in a translucent condition ; which is occasionally the case. The crystalloids when much gashed are reduced to plates more or less separated ; and in many instances the plates are converted into fibres, somewhat mimetic of those characteristic of the "proper wall" (see woodcut, p. Ivii). No cases have cccurred to us of typical " canal system." In numerous cases the reduction of the crystalloids has resulted in the complete removal of their substance, and its replacement by calcite. Although our specimen of " Eozoon mineralized with loga- nite " differs from those which S. Hunt had under his observa- tion, we can quite conceive the existence of specimens of the latter kind, inasmuch as the crystalloids through solvent action may have disappeared altogether, and been replaced by " ferri- ferous dolomite." The specimen closely corresponds with a rock occurring in Connemara, made up of layers of serpentine and malacolite, and which we have elsewhere (p. 2) called malacolophyte : the resemblance is so close that the crystalloids of malacolite in the latter are widely gashed with corroded cleavage, and the gashes similarly filled with calcite. This peculiarity is so much de- veloped that when it first came under our notice we were imme- diately struck with the idea that the calcite had originated from chemical changes in the malacolite. It is now fifteen years since we formed this opinion ; and it has been completely established by our observations on malacolite or a closely allied mineral from Ceylon, Aker (Finland), Isle of Skye, New Jersey, Porthlisky (Pembrokeshire), and Mont St. Philippe (Vosges). We take the specimen of " Eozoon mineralized with loganite " as another evidence in our favour. Wc now beg to call Dr. Hunt's attention to one other point in ■I INTRODUCTION. XVU ng in ^te, and the in the gashes eh de- imme- inated fifteen iletely allied ersey, •sges). ,nite" )int in the mineralogy of "Eozoon Canadense." He has brought under notice a specimen of the presumed fossil from the Calumet, which " exhibits the whole of the sarcode replaced by serpen- tine ; while, in another one from the same locality, a layer of pale green translucent serpentine occurs in immediate contact with white pyroxene." There is very little difEerence, then, between the latter speci- men and the one we have had under notice. Yes, we beg pardon, there is a difEerence : in Sterry Hunt's specimen there are " very thin " calcareous layers (" septa ") which run " transverse to the plane of contact of the two minerals ; yet they are seen to traverse both the pyroxene and the serpentine without any interruption or change.'' It is to be aj rehended that Dr. Hunt, in bringing forward this specimen with its calca- reous septa intersecting the serpentine layers, lays himself open to the doubt of his being sufl&ciently acquainted with the struc- ture of "Eozoon Canadense " as diagnosed by his colleagues. No view which contends for the inorganic origin of the diflFerent eozoonal features can be considered satisfactory unless it be consistent with facts pertaining to mineralogy, geology, or chemistry. With respect to the " chamber-casts " and the " proper wall," their origin, as products answering to these terms, will be made clear in the following pages ; but as regards the "canal system," a point in connexion therewith requires some consideration j for we freely admit that this part possesses peculiarities which seemingly do not strictly accord with ordinary mineral developments, except, it may be, in the case of certain dendritic bodies characteristic of " moss agates." But although at the commencement of our examination of "Eozoon " we felt inclined to identify the " canal system" with the latter products, it was never quite clear to us that we were in the line of the correct view, especially when there were palpable evidences at hand showing that the variety which generally presents itself in the Canadian " eozoonal " ophite had originated through a wasting or decretory process of its component sub- b I«H«1 XVUl INTRODUCTION. s; stance (flocculitc) , whereas the dendritic bodies referred to are unmistakably the indirect products of crystalline development. The point noM' introduced consists of the flocculent variety of the "canal system," which, composed of a homogeneous or structureless substance, ia uidike in its arborescent forms ordinary crystalline products ; while its branchlets resemble casts of tubes and other cavities conceivably produced by tunnel-enclosed vessels of an organism, as predicated of them by cozoonists. We must except in this connexion a variety of the " canal system "consisting of malacolite, as it is palpable beyond dispute that its branchlets have resulted from the decretion of clusters of irregularly arranged crystalloids of a mineral readily affected by solvent action along its eminent cleavage-divisions, and thus etched into shapes equally simulative of arborescent growths. But in the case of the flocculent variety of the "canal system" we are dealing with bodies possessing forms which, although we maintain that they have been equally produced by decretion, cannot be positively said to have been predetermined by cleavage- structure *. We do not propose to enter on an explanation of this point ; all we have to do is to prove the existence of examples simulative of organic features, in the elaboration of which crystal- line forces alone have been concerned, and which are apparently as unlike crystalline products as the typical examples of flocculent " canal system." We refer to the foliaceous expansions charac- teristic of the mineral silicate metaxite, also the coralloids and other configurations of the Sunderland magnesian limestone. First, the configurations in metaxite have a strikingly organic aspect J and it is undeniable that they are purely of mineral origin. It must also be remarked that this mineral, like floccu- litc, is without internal structure ; properly speaking, it has a pasty consistency. Moreover it is closely related to, if not an * Still we have already adduced the most conclusive evidence that rod-like cylindrical processes in serpentine (undergoing change into flocculite) have had their shape determined by rectangnlai' lirismatic cleavage. — See Proc. Roy. Irish Acad. vol. x. pi. xliii. tig. 8. INTRODUCTION. XlX red to are lopment. variety of eneous or iS ordinary ts of tuLes jl-enclosed onists. he '' canal md dispute of clusters ily affected s, and thus growths, al system" 1, although y decretion, )y cleavage- )lanation of if examples ich crystal- apparently f flocculent ns charac- •alloids and estone. gly organic of mineral like floccu- g, it has a , if not an that rod-like [)cculite) have 2. — See Proc. allomorph of, serpentine ; and, what is equally significant, the expansions are included in a calcareous matrix. It may there- fore be confidently assumed that the point which at first sight appears to favour organic intervention in the production of the flocculent "canal system," altogether ceases to be such in presence of the foliaceous configurations of metaxite. Respecting the magnesian limest lue coralloids, and other forms, we have on different occasions spoken of them as gigantic similitudes of the " canal system," " stolons," and " chambers " of "Eozoon." We cannot say of them, any more than it can be said of the metaxitic configurations, that they have been elabo* rated precisely in the same way as the " eozonal " structures. It is sufficient for our purpose that they strikingly resemble not only corals and other organisms, but casts of tubes, chambers, and other structures of the kind just referred to, in their external form, and have seemingly no relation in this respect to ordi- nary crystalline or mineral developments; yet every one who has studied them in situ i? compelled to admit that they are solely the products of inorganic agencies. As such, then, it may be safely asserted that in relegating* the *^caral system'* of ''Eozoon Canadense" to the inorganic kingdom, we are supported not only by evidences of the most decisive character, but by facts strictly belonging to mineralogy and the related sciences. As further justifying this step, it may be mentioned that the coralloids, &c., and their matrix, are demonstratively secondary products that have resulted from chemical changes (Chap. XV. and pp. 118, 119). Supplemental Notes on the Structure and Affinities of Eozoon Canadense. Dr. W. B. Carpenter. Q. J. G. S. vol. xxii. pp. 319-228. To which is added a note containing an extract from a com- munication, dated March 28th, from Dr. Dawson announcing his discovery of " the occurrence of Eozoon preserved simply in carbonate of lime." 62 1866. ^ X2 INTRODUCTION. 1860. 1866. 1866. 1866. In these " NotcH " Dr. Carpenter declares that he is " prepared to maintain the organic origin of Eozoon on the broad basis of cumulative evidence afforded by the combination, in every single mass, of an assemblage of features which can only be separately paralleled elsewhere, and in the repetition of the combination with the most wonderful exactness over areas of immense extent" (will be further noticed, a.d. 1869). Ueber das Vorkommen von Eozoon in dem ostbayerisches Urgebirge. Dr. C. Giimbel. Sitz. des kon. bayer. Akad. d. Wiss. 2u Miinchen, 1866. The author makes known the occurrence in beds of serpentine marble in Bavaria of cozoonal structures, certain of which he considers to represent a new species — '* Eozoon Bavaricum." We noticed in our memoir, last considered, as proving the mineral origin of " Eozoon," the presence in various ealcitic marbles (hcmithreucs) in Scandiravia, Isle of Tyree, New Jersey, of rounded crystalloids of pargasite, chondrodite, born- blende, &c. Dr. Giimbel declares ' ' there can scarcely remain a doubt that the curiously rounded grains imbedded in the crystalline limestones of Pargas represent the casts of sarcode- chambers, as in Eozoon ; and that they are consequently of organic origin." (See translation of the paper in ' Canadian Naturalist,' Dec. 1866.) This point will be further noticed hereafter. Ueber das Vorkommen von Eozoon im krystallinisehenKalke von Krummau im siidlichen Bohmen. Dr. F. von Hochstetter. Pusyrewski. Bulletin de TAcademie de 8t. Petersbourg, vol. x. On the Metamorphic and Fossiliferous Rocks of the County of Galway. Prof. R. Harkness. Q. J. G. S. vol. xxii. pp. 510, 511. " With reference to the occurrence of serpentine in connexion with the limestones of the metamorphic series of Connemara, this has of late become a matter of some interest, in conse- quence of the statement that these deposits afford the Eozoon Canadense. . . . The supposed organic portions of the serpen- tinous limestones of Connemara do not result from animal FNTRODUCTION. XXI " prepared ad basis of ivery single I separately ombiuation lE immense tbayerisches ayer. Akad. »f serpentine [)f which he faricum.'* proving the •ions calcitic Tyree, New roditc, born- rcely remain dded in the s of sarcode- sequently of .11 ' Canadian ther noticed enKalkevon Hochstetter. )om'g, vol. X. le County of txii. pp. 510, |in connexion Connemara, |st, in conse- the Eozoon the 8el*pen- Ifrom animal ■•* 1867. structure, but purely from mineral association. Had fossils of any kind presented themselves in this district, they ought to have occurred in that portion ui the limestone which has been least affected by metamorphic action." Mr. W. Waringtou Smyth, in his Anniversary Address Q. J. G. S. vol. xxiii. p. Ixiv) as President of the Geological Society, noticing the announcement made by Dr. Dawson of " the occurrence of Eozoon preserved simply in carbonate of lime," declared that this " discovery of Eozoon preserved in carbonate of lime pure and simple would appear to close the discussion," Further Observations on the Structure and Affinities of Eozoon 1867. Canadense. Dr. W. J3. Carpenter. A letter to the Presi- dent of the Royal Society. Proc. R. S. vol. xv. pp. 545-549. 15* The writer, who had previously made a similar acknowledg- ment in his "Notes" (a.d. 1866), declares: — ''Yet the very exact correspondence in age and mode of aggregation between the serpentine granules of the Connemara marble and those of the ' acervuline portion ' of the Canadian was sufficient to justify in behalf of the one the claim which has been freely conceded in regard to the other." On new Specimens of Eozoon. Sir W. E. Logan. Q. J. G. S, 1867. vol. xxiii. pp. 253-257. Notes on Fossils recently obtained from the Laurentian Rocks 1867. of Canada, and on Objections to the Organic Nature of Eozoon. Dr. J. W. Dawson. Q. J. G. S. vol. xxiii. pp. 257- 264. ^.t..,.p.. The paper is in a great measure taken up with a description of a specimen of " Eozoon " from Tudor (the one noticed by Carpenter a.d. 1866, Warington Smyth a.d. 1867, and Logan as above), stated to consist " simply of carbonate of lime." Esquisse Geologique du Canada. ? Prepared by the Officers of 1867. the " Commission Geologique du Canada." Notices the Tudor and other specimens of " Eozoon" 5-c- f( f^-^^ XXll INTEODUCTION. 18C8. On the so-called "Eozoonal" Rock. Prof. "W. King and Dr. T. H. Rowney. Abstracts of Proc. Geol. Soc. of London, No. 190. Q. J. G. S. vol. xxv. pp. 115-118. A correct abstract (not prepared by us, and all that was pub- lished by the Society) of an elaborate memoir by the writers. In the discussion which followed the reading of it, Prof. Ramsay stated he " had been struck long ago by the organic appearance of the structure now regarded as Eozoon. He had also felt a difficulty in accounting for the existerce of large masses of limestone, except by the operation of organisms living in the saa, in which such deposits had been formed. He could not imagine the sea-water so overcharged with calcareous matter as spontaneously to deposit limestone." Mr. Parker, Prof. T. R. Jones, Dr. Duncan, and Dr. Carpenter made some remarks, all favourable to eozconism. 1868, Geognostische Beschreibung des ostbayerisches Grenzgebirges. Dr. C. Gumbel. 1868. The Microscope and its Revelations. 4th ed. 1868. Dr. Vv. B. Carpenter. The beds of serpentine limestone in the Laurentian system of Canada " are found in many parts to contain masses of con- siderable size, but usually of indeterminable form, disposed after the -manner of an ancient coral reef, and consisting of alternating layers (frequently numbering more than fifty) of carboiiate of lime and serpentine (silicate of magnesia) ." 1869« Arbeiten der geologischen Section dcr Landesdurchforschung in Bohmen. Prag, I86i\ 1869. Die Gliederung der eozv^ischen Formationsgruppe Nord- America's. Halle. Hermann Credner, of Leipzig. 1869. Eo^roon from Raspenau, in Bohemia. Robert Hofftnann. Journal fiir prakt. Chemie. May 1869. ' An abstract is published in the ' American Journal of Science,' 3rd ser. vol. i. 1871 , INTRODUCTION. XXIU King and 5ol. Soc. of 15-118. lat was pub- le writers. >rof . Ramsay 3 appearance id also felt a re masses of living in the le could not reous matter Dr. Carpenter rrenzgebirges. 8. Br.W.B. tian system of lasses of con- brm, disposed consisting of than fifty) of lesia) /' urchforschung ^ppe Nord- eipzig. oaann. Journal nal of Science,' Prof. Hull. Quart, Joum. of Science, July 1869. 1869, " The researches of Sir William Logan and his colleagues of the Geological Survey of Canada, followed by other naturalists, have demonstrated that even the oldest known limestones on the surface of the globe owe their origin to Eozoon." C:i " EozomCanadense." Drs. King and Rowney. Proc. Roy. 1869. Irish Acad. vol. x. pp. 506-550. Notices the Tudor specimen, which. Dr. Dawson asserted (a.d. 1866), '^ furnishes a conclusive answer to" our ^'objec- tions." But, from the description (amply discussed in the memoir) and photograph given of it, we express 'kittle doubt of its being any thing more than the result of infiltration of carbonate of lime, which has penetrated into a parting between two layers of laminated arenaceous limestone " — an opinion which remains neither controverted, nor even invalidated, though attempts have been made to do so. The "cumulative" argument advanced, but not clearly ex- pressed, by Dr. Carpenter (a.d. 1866) is discussed. It may now be mentioned that the fact of different eozoonal structures being often found in association must be held as a proof of their mineral origin, inasmuch as the mineral silicates com- posing them are in pseudomorphio correlation ; while the calcite and miemite (either of which constitutes the "inter- mediate skeleton") are not only pseudomorphous after these silicates, but they stand in the same relation to each other. The "cumulative" argument is thus totally invalidated by purely chemico-mineralogical phenomena. Besides, Dr. Car- penter in advancing it has placed himself on the horns of a dilemma; for he is required to explain the occurrence of different eozoonal stiuctures by themselves in widely separated countries. The '^ intermediate skeleton" includes the "canal system" and "proper wall." How does it happen that the last feature is absent in the eozoonal hemithrenes of Finland, Saxony, and Ceylon, and only the former one present ? Why XXIV INTRODUCTION. I in New Jersey is it the same ? We answer, because serpentine (which is necessary to form chrysotile, and this to form the ^' tubuli " of the " proper wall ") is not present. And, next, how is it to be explained that the loganitic " Eozoon " only consists of "chambers^' and ^^ skeleton,'' and thus simulates the eal- careo-araphibolic gneisses of Norway and other places ? In a Supplement we notify the occurrence of a specimen of typical " canal system " in the chinks of a large crystal of spinel imbedded in hemithrene from New Jersey. 1870. On Laurentian Rocks in Eastern Massachusetts. Dr. T. Sterry Kunt. American Journal of Science, 3nd ser. vol. xlix. pp. 75-78. Notices the discovery, near Chelmsford, by " Mr. L. S. Bur- bank, of Lowell, a zealous and successful teacher of geology and mineralogy," of " a mixture of limestone and yellowish- green serpentine," rich in "Eozoon Canadense," the " cylindrical diverging branching tubuli" of which are "injected" with " pure carbonate of lime." On seeing this note we immediately wrote to Mr. Burbank, begging of him to supply us with speci- mens of the kind. Some t-me after we received his answer, with specimens. In the beginning he informed us that he had totally changed his views as to the nature and " origin of the presumed fossil," and with respect to " the statement by Dr. Hunt that the tubuli are injected with carbonate of lime, it is incorrect," &c. On testing with hydrochloric acid the specimens ourselves, we foimd none of the " tubuli " had been aflPected. 1870. Note on Eozoon Canadense. [In reply to Professors King and Ilown3y.] Dr. J. W. Dawson, Proc. Roy. Irish Acad, ser. 3, vol. i. pp. 117-123. We are credited with having introduced some " new features " into the discussion, most of which are met in the style of argu- mentation peculiar to eozoonism. One of the new features is the "rcnarkable case" of a spinel from Amity, New Yoric, containing in crevices calcite, which encloses perfect "canal IN':?RODXJCTION. XXV e serpentine to form the d, next, how >nly consists tes the cal- aces? In a n of typical i\ of spinel 3r. T. Sterry er. vol. xlix. '. L. S. Bur- f of geology id ycUowish- " cylindrical ected" with immediately Ls with speci- answer, with le had totally he presumed r. Hunt that s incorrect/' sns ourselves, 3rs King and Irish Acad. ew features" yle of argu- w features is New ¥ork,T rfect "canal system " preserved in malacolite " (a.d. 1869) . " I confess that until I can examine such specimens, which I have not yet met with, I cannot, after my experience of the tendencies of Messrs, Rowney and King to confound other forms with those of Eozoon, accept their determination in a matter so critical and in a case so unlikely." Brief reference is made to the occur- rence of "Eozoon" in the Connemara ophites; but as these rocks are by most geologists believed to be post-Laurentiiin, and there are considerations connected with the presence therein of the presumed fossil unfavourable to its organic origin, the fact of course must be got rid of. Dr. Dawson, although having him- self observed " traces of organic structure " in the Connemara marble (a.d. 1865), and having joyfully accepted the corrobo- rative evidences discovered by Sandford and T. R. Jones (a.d. 1864), suppported also by the testimony of Dr. Carpenter (a.d. 1867), and in presence of perfect examples made known by ourselves (a.jj. 1866, 1869), now declares, ''I have never been able to satisfy myself of the occurrence of any definite organic structure in the Connemara specimens " ! Messrs. King and Rowney on Eozoon Canadense. Dr. T. Sterry 1870. Hunt. Proc. Roy. Irish Acad. ser. 3, vol. i. pp. 123-127. The writer will " not even admit the pseudomorphous origin of serpentine itself, but believes that this, with many other related silicates, has been formed by direct chemical precipita- tion." Dr. Hunt has asserted the same of limestones : they *'owe their origin to chemical precipitation;" "the often repeated assertion that organic life has built up all the great limestone formations is based on a fallacy;" "the occurrence therein of shells, corals, and Eozoon is only accidental." These dicta on the origin of limestones having been thus dogmati- cally pronounced, notwithstanding that many geologists (Ram- say a.d. 1868, Hull A.D. 1869) had accepted the "creature of the dawn" on the faith of its explaining the origin of the calcareous masses of the Laurentians, we brought under the XXVI INTRODUCTION. notice of tlic latter the above view as being inconsistent with their belief. Doubtless, seeing that this point was not without force, Dr. Hunt, in the paper under notice, has been led to modify Itin doctrine on the origin of limestones most materially ; and we feel that some credit is due to ourselves for having contri})uted to so desirable a result. He now admits that "thousands of feet of limestones have been formed from the calcareous skeletons of marine animals;'^ also that "the cal- careous rhizopod ' Eozoon Canadense/ might, and probably did, build up pure limestone beds, like those formed in later times from the ruins of corals and crinoids " ! But he spoils a good thing in stating that our representation of his view cf the origin of limestones is a " misconception ;" — " nor is there any thing inconsistent " in the modified view with iiis original one ! In speaking of limestones " formed without the intervention of life," Dr. Hunt refers to none but some " great beds of ancient marble :" these, there can be no doubt, are the " two grdat formations of limestone beneath the Eozoon horizon, in which this fossil has never been detected." So it turns out that it is only amongst the pre-" eozoic " Ai'cha3aus that chemically pre- cipitated limestones are found ! 1870. Prof. F. Zirkel. Neues Jahrb. f. Mineralogie, 1870, p. 828. After describing the roundish grains of serpentine (which are considered to have been originally peridote) occurring in the ciystalline limestones (hemithrenes) of Aker, PargaSj, Modum (Scandinavia), the author's investigations, it is stated, "did not reveal the canal system which is called eozoonal structure." But it must be mentioned that we have detected in specimens from Aker beautiful examples of " canal system. }) 1870. Eozoon Canadense. T. Mellard Reade. A letter in ' Nature/ Dec. 1870, vol. iii. p. 146. A considerately-written communication, complaining that the replies to our objections, with few exceptions, " were literally little more than reiterations of previous statements i" that in istent with lot without een led to materially j for having dmits that d from the t " the cal- •obably did, later times poils a good view of the 8 there any riginal one ! ervention of Is of ancient "two grdat an, in which ut that it is mically pre- , p. 828. (which are [•ring in the ;as^ Modum d, " did not ture." But cimens from in 'Nature,' ling that the 'cve literally ts ;" that in i INTRODUCTION. XXVll them there is a " strange absence of any allusions to obvious objections," and a " persistent begging of the question involved in constantly speaking of the specimens as undoubted fossils." Eoroon Canadense. Dr. W. B. Carpenter. Nature, vol. iii. 1871. pp. 185, 186. A letter in answer to Mr. T. Mellard Reade. Eozoon Canadense. Dr. J. W. Dawson. Nature, vol. iii. p. 267. 1871. A short note. G. H. Kinahan. Nature, vol. iii. p. 267. 1871. The writer draws attention to the fact of its having been announced that Mr. Sandford haa "proved the existence of Eozoon" in the ophites of Connemara, which, according to Sir R. I. Murchison and Prof. Harkness, are of Lower Silurian (Cambrc ^ilurian) age. " In other parts will be found square miles upon square miles of rocks of the same geological age, often having inliers of limestone ] yet in them there is no Eozoon Canadense, it only being found in a peculiar rock (pseudomorph dolomyte) in this small tract of Lower Silurian rocks, in Yar- Connaught." Dr. J. W. Dawson. Nature, Feb. 9, 1871, vol. iii. p. 287. 1871. A letter, replying to T. Mellard Readers criticisms. T. Mellard Reade. Nature, March 9, 1371, vol. iii. pp. 367, 368. 1871. Dr. W. B. Carpenter. Nature, vol. iii. p. 386. 1871. A letter, more personal than argumentative, which, of course, closed the discussion. The author announced that " Messrs. David Forbes and H. Sorby altogether disown Eozoon as a mineral." On Eozoon. L. S. Burbank. Proc. Boston Soc. Nat. Hist. 1871. The writer's main object is to show that " Eozoon " is found in ophi-dolomites, which occur filling cavities along the line of an anticlinal axis, and are therefore not true stratified deposits laid down with the gneiss associated with them. Prof. John Phillips. Geology of Oxford and the Valley of the 1871. Thames. " Only in another part of the world among strata of gneiss as f^^" ! XXVIU INTRODUCTION. old, if not older, than these of Malvern, has one solitary organic body been found — Eozoon Canadense. This foraminifer or sponge has not obtained its certificate, * proved by the ends of being, to have been,' without protest," p. 61. 1871. On the Geok gical Age and Microscopic Structure of the Ser- pentine Marble or Ophite of Skye. Professors King and Rowney. Proc. Roy. Irish Acad. ser. 2, vol. i. pp. 137-139. This rock, which is well known to be of Jurassic age, contains all the '^ Eozoon" features — "chamber-casts," '^intermediate skeleton," "canal system," and " proper wall;" and, as in speci- mens from Canada, the " chamber-casts " are occasionally pre- served in, besides serpentine, a dark mineral resembling loganite, also white pyroxene or malacolite ! This last mineral occurs in crystalloids which frequently exhibit themselves in a decreted condition internally and externally, the interspaces between them and their hollowed-out interior being filled with calcite : this substance has clearly resulted from the carbacidization of the calci-magnesian silicate, malacolite. Some of the crystalloids are in shapes strikingly resembling the " curiously curved canal system " of Gumbel's " Eozoon Bavaricum" 1871. Addendum to paper on Eozoon. Dr. J. W. Dawson. Proc. Roy. Irish Acad, ser. 3, vol. i. pp. 129-131. Having examined specimens of the Amity rock containing spinel (a.d. 1870), Dr. Dawson admits, but with some reticences, the truth of our statement that " canal svstem " occurs in " unlikely " association with crystals of this mineral. ^' From the general structure and aspect of these specimens, however, I infer that they are portions of a bedded rock and not a vein- stone " ! Other inferences, quite as gratuitous, are added to destroy the force and significance of this " remarkable, critical, and unlikely case." 1871. On the Mineral Origin of the so-called "Eozoon Canadense" Drs. W. King and T. H. Rowney. Proc. Roy. Irish Acad, ser. 2, vol. i. pp. 140-152. The authors notice the principal arguments and evidences adduced in favour of " Eozoon " by Dawson, Carpenter, and INTRODUCTION. XXIX i^stem oncurs in Hunt in their recent memoirs, and conclude with a summary of those brought forward by themselves against the presumed fossil. The " Eozoon " Limestones of Eastern Massachusetts. John B. Perry. Proc. Boston N.H. Soc. April 19, 1871. Notices particularly the Chelmsford limestones announced, in January 1870, by Sterry Hunt to contain " Eozoon ;" the organic origin of which is repudiated by Mr. Perry. The limestones occupy '* pockets, irregular and uneven cavities, or in most cases, oven-shaped spaces, more or less lenticular," being " vein- rocks " of more recent origin than the gneisses which enclose them. The author " leaves undiscussed the question as to the mode of their origin — whether it were by infiltration, segre- gation. 1870) ,^d^ sublimation." Mr. Burbank, in his letter (a.d. Fibed the mode of occurrence of the same rocks in 1871. closely corresponding terms. A Eeview of Sir Charles Lyell's ' Student^s Elements of Geo- 18724 ^ logy.^ John B. Perry. Bibliotheca Sacra. July 1873. Notices unfavourably Sir Charles's acceptance of " Eozoon." The Microscopic Characters of a Silo-carbacid Rock from Ceylon, 1873. — and their bearing on the Methylotic Origin of the Lauren- tian " Ijimestones." Dr. W. King. Geol. Mag. vol. x. Jan. 1873. The rock noticed (hemithrene) contains fine examples of con- 1873. figurations closely resembling the " canal system " in Canadian ophites. Die mikroscopische Berschafi*. der Min. und Gesteine. Dr. 1873. Ferdinand Zirkel. Pp. 313. Eozoon Canadense. Prof. Max Schultze. Sitzungs. der nie- derrheinischen Gesell. fiir Natur- und Heilkunde. July 7, 1873. V --^ A translation is published in the ' Annals and Magazine of Natural History,' ser. 4, vol. xiii. pp. 324, 325. Prof. Schultze, having examined specimens of the presumed fossil, avers " there can be no serious doubt as to the foramini- ferous nature of Eozoon Canadense" 1873. XXX INTRODUCTION. 1873. President's Address. Dr. A. Macalister. Journ. Roy. Geol. Soc. Ireland, new ser. vol. iii. p. 101. A paragraph devoted to the " Eozoon controversy/' and pronounced from the President's Chair of the Royal Geological Society of Ireland, requires some little notice. Referring to some memoirs (not named), it is stated that they " occasioned a con- troversy which, if it did nothing else, turned some attention to the study of micro-petrography, and some at least of the Avriters displayed a very considerable practical ignorance not only of the appearance of sections of large foraminifera, but also of sections of common forms of rock and of the interpretation of rock-forms as seen by the microscope. With a larger expe- rience of micro-petrography will come, I believe, a full convic- tion of the true organic nature of Eozoon Canadense." It is now eight years since these remarks were made ; and undeniably their author had taken considerable pains to master the biblio- graphy of points connected with the subject matter he touched upon : it is therefore to be assumed that Dr. Macalister still takes a deep interest therein, also that he is perfectly aware his " full conviction " has not yet been realized ; hence we would urge on him to endeavour himself to bring about the outcome which he so confidently predicted in his " Address." 1874. On tha Structure called Eozoon Canadense in the Laurentian Limestone of Canada. (A letter to Prof. W. King, Sc.D., Galway.) H. J. Carter. Ann. & Mag. Nat. Hist. ser. 4, vol. xiii. pp. 189-193. The writer pronounces decidedly against the structure of "Eozoon Canadense " being that of a foraminifer. " In vain we seek in the so-called Eozoon Canadense for the unvarying perpendicular tubuli, the sine qud non of foraminiferous structure." 1874. Remarks on Mr. H. J. Carter's letter to Prof. King on the Struc- ture of the so-called Eozoon Canadense. Dr.W. B. Carpenter. Ann. & Mag. Nat. Hist. ser. 4, vol. xiii. pp. 277-284. After speaking of " the well-merited reputation which Mr [loy. Geol. jrsy/' and Geological ing to some tned a con- .ttention to the writers lot only of but also of jretation of arger expe- fuU convic- .se." It is undeniably • the biblio- he touched ;alister still ly aware his le we would le outcome aurentian ingj Sc.D., list. ser. 4, ructure of In vain we unvarying aminiferous the Struc- . Carpenter. 7-284. which Mr M INTRODUCTION. XXXI Carter has gained by his researches on Sponges and Foramini- fera/' and "whose additions to our knowledge of the minute structure of certain types of Foraminifera are estimated by no one more highly thaii by " himself, Dr. Carpenter enters into a long statement highly irrelevant in many respects, and contain- ing much that is given in his previously published papers. Eozoon Canadense. Prof. Max Schultzc. Ann. & Mag. Nat. 1874. Hist. ser. 4, vol. xiii. pp. 324, 325. On the Structure called Eozoon Canadense in the Laurentian 1874. Limestone of Canada. H. J. Carter. Ann. & Mag. Nat. Hist. ser. 4, vol. xiii. pp. 376-378. The writer reiterates his former statement that the "cha- racter " of the aciculae of the " proper wall " of " Eozoon " is " utterly incompatible with foraminiferal structure." Latest Observations on Eozoon Canadense by Prof. Max 1874. Schultzc. (A letter to the Editors of the 'Annals and Magazine of Natural History/ by Arthur E. Barker, Surgeon to the City-of-Dublin Hospital, and Demonstrator of Anatomy in Eoy. Coll. Surg. Ireland.) Ann. & Mag. Nat. Hist. ser. 4-, vol. xiii. pp. 379, 380. This communication contains a copy of a letter from Prof. Max Schultzc to Mr. Barker. The former, acknowledging the receipt from the latter of a copy of our paper published in the ' Proceedings of the Royal Irish Academy,^ July 1869, states that he " agrees with " us " in many important points, supported by my '^wn investigations on Eozoon Canadense," and that our *^ treatise has made a very great impression upon " him. He begs Mr. Barker to obtain some specimens of Connemara ophite ''and to 'xU Messrs. King and Rowney that, with respect to the 'proper wall' of Carpenter, I am entirely of their opinion that it is of inorganic origin." Mr. Barker concludes : — " I may state that, through the kindness of Di-. King, I was enabled to send Professor Schultze some beautiful specimens of the stones he desired, and was expecting from him a letter of acknowledgment when I received the sad news of his death." ; i n if XXXll INTRODUCTION. 1874. Further Remarks on Eozoon Canadense. Dr. W. B. Carpenter. Heport Brit. Assoc. Belfast Meeting. Additional reasons are adduced " for concluding the organic nature of the organism ''; and a contradiction is given to our " assertion " that Prof. Max Schultze had, just before his death, changed his opinion on " Eozoon." " Mr. Gwyn Jeffreys, Prof. Macalister, and Prof. Perceval Wright expressed their general concurrence in Dr. Carpenter^s views." 1874. New Observations on Eozoon Canadense. Dr. W. B. Carpenter. Ann. & Mag. Nat. Hist. ser. 4, vol. xiii. pp. 456-470. Dr. Carpenter in his usual style replies to Mr. Carter and the "two Galway Professors :" the summary of the arguments and evidences brought forward in our paper last noticed (a.d. 1871) is all but ignored ; and Taffaire Max Schultze i? +b"s disposed of: — "At any rate, there is no mention of the nummuline wall in his communication to the Wiesbaden Association — his acceptance of Eozoon as a foraminifer entirely resting on the * canal system,^ which he had minutely studied, and as to which there is no evidence whatever that he had changed his opinion, as asserted by Professors King and E-Owney. Had he lived to see what I shall presently describe, I. cannot doubt that he, in common with the numerous microscopists to whom I have recently shown it, would have accepted the ' nummuline wall ' without the slightest hesitation." What we " asserted '' was that " whatever opinion the late Prof. Schultze might hold in the autumn of last year respecting ' Eozoon/ he subse- quently changed it after reading our papers." There is not a word here about the '* canal system " ! What Dr. Carpenter was to "presently describe," which is called a " probative fact," is seen in a " section of mi nmuline layer," in which " many of the tubuli remain empty ; and they can be distinguished as tubuli under any magnifying-power that the thickness of the covering-glass allows to be used." We have on a former occasion stated our reasons for demurring to this case (Ann. & Mag. Nat. Hist. ser. 4, vol. xiv. p. 285), at the INTRODUCTION. XXXIU Carpenter. the organic iven to our e his death, n Jeffreys, ressed their . Carpenter. 6-470. rter and the nments and (a.d. 1871) ms disposed nummuline Association irely resting died, and as changed his ney. Had lannot doubt [sts to \Thoni nnmmuline " asserted " iltze might i/ he subse- icre is not a |ibe/^ which nv. nmuline |y ; and they mer that the '^ We have rring to this k85), at the same time expressing ourselves as ** not disputing that the section exhibits some structural peculiarity which gives rise to appear' ance of tubulation." In connexion with this matter, it may be mentioned that we have frequently observed in minerals a divi- sional structure which it is difficult to describe or designate. In our description of a specimen of pcridote, represented on Plate I. fig. 3, mention is made of the occurrence therein of thin fibrous or striated undulating laminae, the " striaj or fibres of which are at right angles to the surface of the laminae." A similar struc- tural character, seen on one of the two sets of eminent cleavage- planes, marks the felspar represented in fig. 4, PI. I. For want of a better name, we stated that the laminae are fibrous or striated; but we were quite aware at the time that the intersecting striae or fibres are often separated, and seemingly tubiform : thus, where a transverse section of such fibres is exposed they appear like circular dots — even more decidedly than as repre- sented in our figures. We draw attention to this peculiarity, as probably offering an explanation of the " empty tubuli." What we strongly suspect will prove to be the same are the cuts or lines forming the " first'' or incipient stage in the development of chrysotile (pp. 9, 14, &c.) ; especially as we are unable to detect any difference between them and the striae, that are thread-like, of feldspar. Seemingly confirming our suspicion is the fact that the " striation " of a feldspar in graphic granite has actually been taken for " vertical tubular structure " by Dr. Carpenter^ as will hereafter be seen. Eozoon Canadense. Dr. J. W. Dawson. A letter in ' Nature,' 1874. June 11, vol. X. p. 103. " Eozoon " examined chiefly from a Foraminiferal Standpoint. 1^74. Drs. W. King and T. H. Rowney. Ann. & Mag. Nat. Hist. ser. 4, vol. xiv. pp. 274^289. Final Note on Eozoon Canadense. Dr. W. B. Carpenter. 1874. Ann. & Mag. Nat. Hist. ser. 4, vol. xiv. pp. 371, 372. Dr. Carpenter, notwithstanding the many errors he has cam- c [' » I \ i i I, I 'li XXXIV INTWODUCTION. Xuittcd in describing the structure of the Foraminifcra (we speak a.dviscdlv), holds a position in microzoolog^y which justly entitles him to take rank as one of its very highest authorities. He docs not, however, think it unbecoming to charge us with having, in our contest against Eozoonism, " betrayed a shocking state of ignorance of foraminifcral structure " — although, on the same page, as it were, in which this charge is preferred, it is too evident, from what is stated of the "parallel tubulation" of Nummulites lavigatus in comparison with that of " Eozoon Cana- dense" that he is far from being an infallible authority in his own speciality. This must have been made palpable to himself, on reading our paper — " Eo::oon examined chiefly from a Foramini- fcral Standpoint." Hence this " Final Note." When, in his endeavours to set aside our remarks on certain " foraminifcral impossibilities," Dr. Carpenter talks about believing what he sees with his " mind's eye, rather than with " his " bodily eye," and considering his inability to comprehend that the truism ** there is no end to the possibilities of Nature " does not teach the fallacy that Nature indulges in impossibilities, it is evident he was feeling that his discussion with us was becoming a hopeless task. What we say are impossibilities of the kind are : — a " canal system " abutting directly against the under and attached side of the " proper wall," instead of passing out to the surface of the organism j and the "tubuli" of the " proper wall " frequently lying horizontally against, or parallel with, instead of standing perpendicularly on, a presumed "chamber"^. Other cases of the kincJ could be adduced. It is a folly attempting to get over these things by * Dr. Carpenter, in answer to this objection, urged by Mr. H. J. Carter (Ann. & Mag. Nat. Hist. 4th ser. vol. xiii. p. 192), states that the horizontality of the tubuli haa its " precise counterpari ' in Nummulites l>n " and " James ' Thomson,'^ announcing that they *' have recently discovered evidence of life " in the Laurentians of Harris, the specimens being " as clearly organic in their nature, and as well preserved in their minute structure, as is the case with Silurian or Devonian fossils of an analogous structure (such, for example, as Stroma- topora)." The specimens, "unequivocal organic bodies," are "little .: ' i\', the skeleton of the fossils being calcareous appare vii o' imite, and exhibiting all the minute details of its structu . . • whilst the chambers are filled, as so common in organic remains from younger deposits, with transparent silica. Pmally, though apparently differing from it in important respects, we believe that our specimens will contribute power- fully to the solution of the controversy which has been of late years carried on as to the true nature of Eozoon." ' i ■ ■ iji ! I iii; xl INTRODUCTION. Be it observed that this announcement is inserted in the same number of the ' Annals ' which contains our memoir above noticed. But more is to follow ! 187(5. -^Qy^ Laurcntian Fossil. Nature, May 4, 1876. Dr. W. B. Carpenter annovinces the discovery, in " Harris, of what is regarded by every palaeontologist who has seen the specimen as an unquestionable organism." ..." The fabric seems to have consisted of superposed layers of calcareous shell- substance," with spaces between them much thinner than the layers, " filled up with calcite.'' " Altogether I have no hesitation in concurring with Prof. H. A. Nicholson, Prof. Geikie, and Mr. Etheridge in affirming it to be so unmis- takably organic, that, if it be claimed by mineralogists as a ' rock-structure,' a large number of universally accepted fossils will have to go along with it." Our reference (preceding page) to what proves to be the same " unquestionable organism " brought out, as was to be expected, the following letters, which, though commendable in one respect, ignore altogether the brief remarks made by us respecting its being granite, consisting of layers of quartz and feldspar ! 1876, Supposed New Laurentian Fossil. Nature, May 35, 1876. Dr. W. B. Carpenter. " I lose no time in making known to the readers of ' Nature ' that the notice of a New Laurentian Fossil which I published in its columns three weeks since, was written under a complete misapprehension of the real nature of the body. So far from being calcareous, as I had been led to believe by the information I had received from the geologist who found the specimen, it proves to consist of alternating layers of felspar and quartz — the former simulating an organic structure like that of Stroma- topora, and the latter occupying what had been supposed to be cavities of that structure — together constituting what is known to petrologists as ' graphic granite ;' " " and what had seemed to be a vertical tubular structure, proving to be mere striation " (see p. xxxiii) . " The examination of numerous sections of this body, _.' INTRODUCTION. zli ^d in the p memoir " Harris, has seen . . "The calcareous nner than [ have no sou. Prof, so unmis- gists as a ted fossils e the same ; expected, ne respect, aecting its par ! 25, 1876. Nature ' iiblished in complete far from iformatiou specimen, d quartz — of Stroma- osed to be t is known 1 seemed to ition" (see : this body, and a comparison of them with sections of the 'graphic granite,' has now satisfied me that the agencies which produced the 'graphic granite ' were competent to have produced the supposed Harris fossil. Whether these agencies were entirely inorganic, or whether the ' graphic granite ' itself may not be a metamorphic form of an ancient organic structure (metamorphoses as strange have undoubtedly happened), is a question which is not at present to be decided by any one's ipse dixit"* \ Supposed Laurentian Fossil. Dr. H. A. Nicholson. Ann. & Mag. Nat. Hist. ser. 4, vol. xviii. p. 75. A letter withdrawing the statement that the specimens noticed in his former letter " were essentially calcareous in their com- position," as " upon ijivestigation, the specimens proved to be composed of alternating layers of felspar and silica." The writer concludes with a remark by which he identifies himself with Dr. Carpenter in his ipse dixit : — " Whether the peculiar arrangement of the minerals which constitute these specimens can be assigned wholly to the operation of inorganic causes or not, is a question which does not in the meanwhile admit of solution " ! We embrace the present opportunity to mention a few points connected with the Ham" . graphic granite. Fig. I, PI. I., represents a portion of the specimen presented to us by the late Prof. R. Harkness, showing lamellae of quartz and feldspar (both represented vertically) ; also the striping or "striation " (charac- teristic of plagioclases) intersecting the feldspar layers nearly at a right angle, and taken by Dr. Carpenter for " tubular structure." Fig. 3, PI. IX., represents a small portion, slightly under the natural size, of a beautiful and interesting specimen (5 inches by 2 inches) which has been kindly placed, with others, in our hands by Dr. Heddle, the mineralogist of Scotland. The inter- lamellation of the quartz (brown in the fi^re) and the feldspar (purple) is both "strictly limited" and of "definite form." The feldspar, which, from its silvery appearance, seems to be • The italics are ours. 1876. 9 i m in; xlii INTRODUCTION. of the variety called " moon-stone," is obliquely intersected by what appear to be laminae of a triclinic feldspar, inasmuch as they are crossed with striaj : similar laminae are seen in the specimens of orthoclase represented in fig. 4, PI. I. Our figure of Dr. Heddle's specimen aifords but a poor idea of its beauty and remarkable structural character. 1870. Notes on Otto Halm's Microgeological Investigation of Eozoon Canadense. Dr. William B. Carpenter. Ann. & Mag. Nat. Hist. ser. 4, vol. xvii. pp. 417-422. 1876. Eozoon Canadense according to Hahn. Dr. J. W. Dawson. Ann. & Mag. Nat. Hist. ser. 4, vol. xvii. 187G. Review of Dr. Dawson's ' Dawn of Life.' Decade II. vol. iii. April 187G. T. R. J. Geol. Mag. 1876. Note on the Geological Position of the Serpentine Limestone of Northern New York, and an Enquiry regarding the Relations of this Limestone to the £osoo«-limestones of Canada. Prof. James Hall. American Journal of Science, 3rd ser. vol. xii. pp. 298-300. Noticing the lower division of the Laurentian rocks in Northern New York, Prof. Hall states that they are " uncon- formably overlaid by massive beds of gneissic and labradoritic formations, associated with 'vhich are one or more bands of crystalline limestone : the latter " is usually and perhaps always permeated by serpentine in grains, bands, or what sometimes appear as concretionary or aggregated masses of that mineral." This serpentine limestone " has been reported as containing Eozoon." ..." The simple point which I wish to demonstrate is that this limestone" of Northern New York "does not belong to the Laurentian limestone, either Lower or Upper, that it is a formation deposited along the flanks of and within the Laurentian area, at a period subsequent to the deposition, metamorphism, and disturbance of the rocks of authentic Laurentian age, and that it apparently holds a place in the INTRODUCTION. xliii sected by ismuch as en in the I. Our iea of its of Eozoon . & Mag. Dawson. reol. Mag. aestone of Relations f Canada. , 3rd ser. rocks in " uncon- bradoritic bands of ps always ometimes mineral." ontaining nonstrate does not >r Upper, id within sposition, authentic e in the * series between the Laurcntian and Potsdam periods, but whether liuronian or otherwise I do not pretend to say ; and it may even prove of later date than this." It will hereafter (a.d. 1880) be seen that the serpentine lime- stones of Northern New York arc now held by the leading geological authorities in the United States to be of Upper Cambrian and Lower Silurian ages. On the Serpentinite of the Lizard, its original Rock-condition, 1876. Methvlotic Phenomena, and Structural Simulations of Organisms. Drs. W. King and T. H. Rowney. Phil. Mag. ser. 5, vol. i. pp. 280-293. The rock in many places has undergone a change into saponitc, and occasionally into calcite. The former contains bodies of various kinds, strikingly simulating minute corals, vermiform and foraminiferal organisms ; the latter contains cylindrical forms and clusters of spherical bodies, resembling Dawson's "Archceo- spharina," and branching configurations identical with the "canal system" of Eozoon. What appears to be tremolite contains spherical and other bodies wonderfully mimetic of perforated foraminifers, also rods consisting of saponite, serpen- tine, flocculite, or calcite. The rods, especially those com- posed of the last mineral, throw some light on the origin of the " " calcareous " examples of the " canal system," inasmuch as their component mineral carbonate is clearly the result of chemical alteration. The serpentine contains examples of chry- sotile passing into the "nummuline" or pectinated condition. New Facts relating to Eozoon. Dr. J. W. Dawson. Canadian 1876. Naturalist, vol. viii. pp. 281-285. " And though I must protest against the idea prevailing in some quarters, that there is any necessary connexion between serpentine and Eozoon, yet, as this mineral exists in connexion with many specimens of this fossil, it is time that geologists were warned against the extravagant ideas of pseudomorphism which have been promulgated in connexion with it " I Re* f \} ( 1 i. i: ''I I *[ jl It!" .' xliv INTRODUCTION. fcrcnces are made to " microscopical and palseontological evi- dences," which " completelv vindicate the theory of aqueous deposition of serpentine as maintained hy Dr. T. Sterry Hunt''! **The announcement by Prof. Karl Mtibius of a recent sessile Foraminifer from the Mauritius, not very remote from Eozoon in its general mode of growth,'' is declared " to be an important contribution towards the history of the oldest fossil." 1876. On the Serpentine and Associated Rocks of the Lizard District. Rev. T. G. Bonney. Quart. Journ. Geol. Soc. vol. xxxiii. pp. 881-934. During the discussion which followed the reading of this memoir, and in answer to a question put by the President, the writer replied that " for his own part he believed in the organic nature of Eozoon." How this reply is to be reconciled with the following statement Prof. Bonney has lately made — *' I have never myself seen a serpentine which loas not intrusive" (Geo!. Mag., Feb. 1881, p. 94)— is a puzzle to us, as it must be to eozoonists, considering that their doctrine is based on the sedimentary or *' aqueous deposition " of '^ eozoonal " serpentines (see last citation) . But is not eozoonism full of inconsistencies ? 1876. Otto Hahn. WUrttembergische naturwissensch. Jahreshefte, Jahrgang 1878. 1876. Supplement to the Second Edition of 'Acadian Geology.' Dr. J. W. Dawson. Notices the occunence of " somewhat obscure structures, which appear to indicate the presence of fragments of Eozoon" in one of the Upper Limestones, considered to be Upper Lau- rentian, near St. John's, New Brunswick. 1876.^ Dr. T. Sterry Hunt, addressing a meeting of the Natural- History Society of Montreal, after his return from Europe, announced the cheering news that " the animal structure of Eozoon was now pretty generally admitted by European scientistf." (Canadian Naturalist, vol. ix. p. 58). INTRODUCTION. xlv rical evi- aqueous rllunt'M nt sessile (I Eozoon mportant Distrint. ol. xxxiii. g of this ident, the le organic i with the -*' I have e"(Geol. LUst be to [d on the 3rpentines istencies ? .hreshefte, ^^ 'gy- Dr. tructures. Eozoon," jper Lau- Natural- i Europe, iicture of European Der Bau des Eozoon Canadense nach cigencn Untersuehungen 1878. vcrglichen mit dera Bau der Foraminifercn. Prof. Karl Mcibius. (Besonderer Abdruck aus der Paleeontographiea Eando xxv.) Abstracted in * Nature/ vol. xx. pp. 272, 297. Having " investigated more closely and described more mi- nutely its form and structure than any other naturalist,'^ the author wishes it to be understood that he has " successfully eliminated Eozoon from the domain of organic bodies." P'or obvious reasons we regret that Mobius has been led to make these remarks, especially, — (Ist) as in our opinion he has com- pletely failed in explaining the origin of the eoaonal structures, the necessity of which may be held to be of primary importance in any attempt to overthrow their asserted organic origin, — (2nd) with respect to what he says in connexion with chrysotile, we consider ourselves to have proved, in the earliest stage of the discussion, that the " nummuline layer " has resulted from struc- tural modifications of this mineral, — and (3rd) as his foraminiferal arguments are little more than an amplification of a number of vital points that were advanced by Mr. H. J. Carter and our- selves long before he became a convert to his present views. On the Microscopic Structure of Stromatoporidse, and on Palae- 1878. ozoic Fossils mineralized with Silicates, in illustration of Eozoon, Dr. J. W. Dawson. Quart. Journ. Geol. Soc. vol. XXXV. pp. 48-66. The entire memoir is interesting in connexion with one of the expressed subjects. We hold the stated facts, however, as affording no crucial evidence in favour of " Eozoon'* But we are more directly concerned with the closing section (iii.) of the memoir, treating of " Imitative Forms resembling Eozoon." Of these one is a specimen from Gouverneur, St. Lawrence Co., New York. *' It presents thick bands of a peculiar granitoid rock, containing highly crystalline felspar and mica, with grains of serpentine ; these bands are almost a quarter of an inch in thickness, and are separated by interrupted parallel bands of ealcite, much thinner than the others. The whole resembles a xlvi INTRODUCTION. ! J: J 1879. 1879. 1879. 1879. 1879. 1879. magnified specimen of Eozoon, except in the absence of the con- necting chamber-walls and of the characteristic structures. A similar rock has been obtained by Mr. Vennor on the Gatineau j but it is less coarse in texture though equally crystalline, and appears to contain hornblende and pyroxene. These are both Laurentian ; and I consider it not impossible that they may have been organic ; but they lack the evidence of minute structures, and diflfer in important details from Eozoon." These details are, pre- sumably, the " proper wall " and " canal system. '' In what do the above specimens differ from the much-cited " Burgess Eozoon " ? The mention of these two specimens is a tardy recognition of the facts, first brought forward by ourselves, but constantly pooh- poohed, notifying the occurrence in rocks of a definite lamination identical with that of ''Eozoon." But the literature of the sub- ject hereafter is to contain a new chapter — " Imitative Forms re- sembling Eozoon "\ As Dr. Dawson is now becoming acquainted with forms of the kind, there is some hope for the triumph of truth. Principal J. W. Dawson's criticism of my Memoir on the Struc- ture of Eozoon Canadense compared with that of Forami- nifera. Prof. K. Mobius American Journal of Science, 2nd ser. vol. xviii. 1879. A notice by " T. R. J.^' of Mobius's Der Bau des Eozoon, in Ann. & Mag. Nat. Hist. ser. 5, vol. iii. pp. 314-316. Zur Eozoon-Yrage. Otto Kuntze. Anti-eozoonal. Jj' Eozoon. A. Six. Soc. Geol. du Nord, Annalesj tome vi. 1878-79. Die Urzelle, nebst dem Beweis dass Granit, Gneiss, Serpentin, Talk, gewisse Sandsteine, auch Basalt, endlich Meteorstein und Meteoreisen aus pflanzen bestehen. Dr. Otto Hahn. On the Origin of the Mineral, Structural, and Chemical Cha- racters of Ophites and related Rocks. Drs. W. King and T. H. Rowney. Proo. Roy. Soc. ''To. 197. ' Nature,* No. 544. The present work is, to a great extent, based on the original INTRODUCTION. xky memoir, of which the paper imder notice is an " abstrapt." The latter notices the occurrence of ' ' beautiful examples of ' canal system/ resulting from the waste of crystalloids of malacolite, im the calcaire saccharoide (hemithrene) of St. Philippe (Vosges), rivalling those in Canadian ophite." ■ When speaking of this hemithrene (pp. 51, 52) we omitted to mention that, besides the " canal system," there are also present rounded grains or crystalloids of pyrosclerite (a serpentinous mineral), occasionally invested with an asbestiform mineral related to, if not identical with, chrysotile : the investing fibres, usually in contact, are in many places separated by interpola-t tions of calcite (PI. III. figs. 2, 3), a fact proving them to corre- spond with those of the " proper wall " of ''Eozoon Canadense" Mobius on Eozoon Canadense. Dr. J. W. Dawson. American 1879. Journal of Science, March 1879. The writer, as must have already been noticed (a.d. 1876), is evidently anxious to make out that there is no necessary connexion between serpentine and " Eozoon." This anxiousness seems to have developed itself apace ; for he now asserts that " only a few " geologists and mineralogists " have learned that Eozoon is only sometimes associated with serpentine " 1 Totally dissenting from such an assertion, we beg to draw Dr. Dawson's attention to the fact, which ought always to be uppermost in his mind, that " Eozoon " is mostly present in metamorphic rocks, especially ophicalcites and hemithrenes (the product of chemical changes), and is " best preserved in those that are highly crys- talline." And by way of invalidating Dr. Dawson's assertion, we challenge the production (allowing certain exceptions, which are explainable) of an indisputable specimen of " Eozoon " with its "chambers," "canal system, and "proper wall" ("tubuli"),- preserved otherwise than in serpentine or a serpentinous mineral. We admit occasional exceptions, because the mineral silicate forming these features is replaceable by calcite. Dr. Dawson refers to the " cumulative force " of the eozoonal structures " when taken together. In this aspect, the case of \w T. xlviii INTRODUCTION. i' II ! Eozoon may be presented thus : — (1) It occurs in certain layers of widely distributed limestones, evidently of aqueous origin, and on other grounds presumably organic/' Our two last para- graphs completely invalidate number one " force •/' but we may add that eozoonal structures also occur in intrusive serpentinyte (Cornwall). "(2) Its general form, lamination, and chambers resemble those of the Silurian Stromatopora and its allies, and of such modern sessile Foraminifera as Carpenteria and Poly- trema." Mineral developments simulate the eozoonal features mentioned, and so closely, in many cases, that Dr. DaM'son has repeatedly admitted that he cannot decide as to whether or not they are organic ! Those who have studied the organisms named repudiate the resemblance stated. " (3) It shows under the microscope a tubulated proper wall similar to that of Num- mulites, though of even finer texture." Reference to the two woodcuts of the " proper wall '' of " Eozoon Canadense " and that of Nummulites /ni;ed green in the figure, the undermost one consists — the lower nalfATi colloidal or amorphous serpentine, and the upper hair m" typical chrysotile : the uppermost layer is composed of what at iivif sight might be taken for ordinary serpentine, but which, nu close examination with powers of 25 and .40 diameters, turns out to be in the state of incipient chrysotile, being traversed by sejjarated fne filiform cuts, Avhich seem to give rise to a columnar structure. The direction (which slightly deviates from the perpendicular) of the cuts and the columns, it is noteworthy, is thfj same as that taken by the fibres of the uj\derlviiig chrysotile. On the le(t nalf^of t!he upper surface of the layer containing typical chrysotile may be clearly seen the fibres passing con- tiimou^ly jito a series of definite but closely adhering aciculse, atm «*tne right itniS into similar aciculas : here, however, they are distinctly separated by interspaces filled in with calcite. In eozoonal paviaiice the latter aeiculse are " casts of tubuli " in undisturbed relation to the " intermediate skeleton " and its ^ * ii; OPHITES AND RELATED K0CK8. 19 •ainiug g cou- ciculse, r, they calcite. iibuli " and its I integral *' iiummulinc wall/' just as would be the case when the latter was penetrated by the iormative pseudopodial pro- cesses of the animal. We cannot conceive how any impartial investigator, having an acquaintance w ith mineralogy, and in face of the evidences placed before him, can resist the conclusion that this " num- mulinc walP^ is the product of structural changes charac- teristic of chrysotilc. By way of disposing of these evidences, tlic advocates of " Eozoon " have made a leap ivorc. Scylla into Charybdis. The " nummuline wall,'^ it is argued, has been altered by crystallization and pseudomorphism, so that it, origi- nally lime, has been converted into chrysotile or its modifications. Nay, our '' complicated theory of metamorphism " has actually been adopted by Dr. Davvson to explain this " change of calcite into serpentine^^ and its allomorph, chrysotilc — Avhich change it appears, he has seen in some specimens of " Eozoon'"^ ! As to the arg!imeu*^ based on the idea that the " iiuir r^^ulinc wall " has become accidentally associated with the ehrysotiie, the fact is of such common occurrence, as are also the concomitant parallelism of the layers showing the two modifications, and the continuity both laterally and lengthwise of their respective aeiculse and fibres, as to completely destroy this and any other argument offered in support of eozoonism, based on these considerations. A few more remarks on this specimen. Mention has already been made of the serpentine often passing into the flocculent state. In the specimen which has supplied us with the portion last considered, flocculite is rather common in the layers of calcite, filling them here and tiicre (as near the bottom on the left side of the figure), or bordering the serpentine enclosing these layers — occurring therein as simple or segmented clotules, which here and there graduate into configurations varying from the simplest rods to much-divided or blanching shapes. It is necessary to mention that both the clotides and configurations enclose portions or cores of serpentine. The configurations have been taken for casts of tube pene- trating the ealcitic layers, and to represent the canal-system present in the calcareous skeleton of certain existing foraminifers. But their characteristic irregularity of form, theiv gradation into the clotules, and their agreement in composition with the • See Introduction, a.d. 187tf ^ c2 i 80 m»( K-MVIAMOurHINM, Irtttrr roniplrtrly juoxc \]\;\\ t(on» o\' owv tignrp, tho\igh not pxhihiting n poniplplc Rpnps oi' thp forniativp phangps, is npvprthph'ss of ponsiids, a\ul sphpi'oids, pansing thpir snrfapps to he irrcgn- larly porrodpil into hollows and projppting U)l)ps. Thp8p hodips arp ivgardpd as " t^sts " of the " phamhprs of poKOon ;" hut, holding tt) thp vipw ahovp givpu, wp have no hpsitation in ri^lp- gatmg them, in rpspppt of thpir origin, to thp patpgory of ininpral struptuvo!?. In some instuncos thp fiooonlite has uot hcQU rcinovpd (spc loft side of the figuiv), but rcmaius as a layer l)p of ser|Hnitim\ It will be spen lurpflfter that there is strong presumptive * Tlic cxamplo doo>. not bolong io tlu' ^Jhoo in which it is jvpix-f-enli'd. hut (o nno close hy : it is truthlulU i-oj iX'!*ontcHt in its ix^huion to ilitMitlini ciil hordvr ol tloooulito. Anollicr c xnm]lo. roprosi>ntod in n lonncr jmju'r (rice. Ihn. Irish \ci\(\. vol. X. \\], xliii, ti^. 7V is au iut«i"ui«diate modilicntion. i J OPHITKS ANI» HRF.ATEI* lUK RH. al ('vidrnrr \\\\\i Hirnmil wiilor'* iiidcd Hie iissmiinl cluMiiicjil rciiclioiiH. Iluviiifj; now iliNpoHcd ol nil llic ^crpriiliiioiiM ^ilnicfiircM ol " NozffOH ('onmicnsr '^ in Mliid (•onConiiity \viMi flKMinitniifMis known to (!'('t l,o tlir inlfr("liiinK«'H hclwcrn a niincral Hili(!(it,(i nnd a nnnnral carljonati", ol'lcn oliluinin^j; in ophite, we lind thnt lh(> cahMtc which IViMjnently holds a place in tin; liiyeiM ol' (Oii'y- solil(< is lihiMniH in eerliiin inHiances, and relainH tin; ori|/inal Ntrnetnre of the latter mineral, (ienendly, however, the ehara**- teriNtie rhoiiihohedral eh-aviif^o of raleito is developtMl. ThiH replacement of chryHolile hy a mineral ciirhonatc! retaining its typical lihroHJty, and thererore poHH(!HHinfr n lihronn Pitnieture similar to that oi' ara^onitc, has octtnrrcd to wh in speeimeiiH oi' ophi-cn|)hotide IVom tin; north of I tidy, mm idriuuly noticuid in one ol' otn' previous menntirs'^. We have mIso hecomi" iM'(|nainted with n Himiliir I'net occurring on tin' shoi'(> (>iiMt of the liizard, Cornwall, wIhm'c Hcrpentinyte, nnon hy dilute hydrochloric acid, show Iumc and there vacant spaces f)etw(;nii the tihrcs, and otlu'r evidiMiees ol" the reujoval of n mineral carhonate. Tlu! mineral silicate, malaeolito or whitf' augite, undergoes similar chang(;s. A variety of ophite occurring in (.'onnemara contains layers formed of crystalloids of this mineral. Inmost instanecis, hesides heing widely gashed, and tin; gashes filled up with ealcitc, the crystalloids are separatcid from one another hy the same mineral carhoiuitc ; an.l they exiiihit their angles and * PriH'. Hov. Irisli Arnd. vol. vx. pi. xliv. (i/^. 9. 33 ROCK-METAMORPHISM. edges more or less rounded off, evidently by corrosion. Decal- cification exposes these facts most instructively^. The origin the calcite must be obvious to any one Avho has studied pseudomorphism. The same phenomenon is displayed, though under somewhat modified circumstances, in the hemithrene ("calcaire saccha- roide,^^ Delesse) of certain localities- in the Vosges. At St. Philippe, near Ste. Marie aux Mines, this rock is filled with crystalloids of malacolite and other mineral silicates, often almost to the exclusion of calcite. Confining ourselves for the present to the malacolite, its crystalloids, or aggregations of them, are more or less affected by corrosion or decretion, beginning with the rounding-off of their angles and edges; next, reducing the aggregations, it forms them into rude, irre- gular, geniculated shapes; and next etches them into somc- Avhat definite configurations — foliaceous, dendi'itic, plumose, radiate, and often beautifully arborescent. The configurations vary much in size, some being observable with a hand mag- nifier, others so minute as to be only made out by a good microscope. Fig. 1, Plate III., represents one of the aggre- gations, wdiich has taken the shape of a branching configura- tion f: its component crystalloids, in a corroded condition, are Avell seen. Guided by a lemark made by Delesse, we expressed our suspicion some time ago that the " calcaire saccharoide" of the Vosges would yield on examination these and other structures J; but wc had no idea that it was so rich in examples rivalling, and in no way surpassed in beauty and imitativeness, the configura- tions (''canal system oi Eozoon") which at that time had become known as occurring in Canadian ophite, — though since then we have published the fact, previously unknown, that precisely the » * Ileddle mentions what appear to be similar examples, occurring at Muir and Midstrath, in which the '' lime is little more than granular malacolite with but littlo lime between the ciystals " (see Trans. Roy. Soc. Edin. vol. xxviii. p. 461). t Zirlrel has represented a portion of a crystal of mica (fig. 35, p. 87, * Die miki'osk. BeschafFenheit d. Min. u. Gesteine ') Avhich, through coiTosion or decretion, has assumed a dendritic or branching form. This example shows very well how crystals and other mineral bodies have taken the remaHmbly imitative shapes often displaj'ed by malacolite and serpentine. X Quart. Journ. Geol. Soc. vol. xxii. p. 188, footnote. The " nummuhnq wall " is also present. See Introduction, a.d. 1880. '-.■:■•S^f^-' OPHITISS 4ND HEI.ATED ROCKS. 33 same bodies are present in hemithrenes from Ceylon, Aker (Soderraanlaud in Sweden), and New Jersey*. The Vosgcs is an additional locality, which we have only of late ])ecQmc acquainted with. are The question naturally suggests itself as to how the separated acieulse in pectinated chrysolite, the arborescent configurations in flocculite and raalaeolite, and the plates, lenticuloids, and spheroids in serpentine have been produced. From the evidence, so far adduced, our view will have been to some extent antici- pated — that it is by chemical reagents involving the removal of serpentine or other mineral silicates, and their replacement by calcite or other mineral carbonates. Chemical changes of the kind, known as pseudomorphism, are not uncommon in the mineral kingdom. They may, for our purpose, be arranged under two heads — entire and partial, The first consists of cases in which all the original constituents of a mineral having been abstracted, are subs'^itutcd by other substances ; the second consists of cases in whicli the removal of certain constituents of a mineral, and their replacement by other substances, have taken place. As an example of the first, crystals arc found in Cornwall consisting of cassiterite or oxide of tin ; but, instead of repre- senting the form proper to this mineral (viz. a modification of a square prism), they occur under a /«/.ye form — the one that cha- racterizes orthoclase, which is a silicate of alumina and potash; in this instance an entire change of substance has taken place. The second may be illustrated by selenite — a hydrous sulphate of lime, well known as crystallizing in right rhomboidal tabular crystals ; but occasionally such solids are found consisting of carbonate of lime, the basic constituent remaining, but the acid and water eliminated, both having been replaced by carbonic acid. Karstenite, an anhydrous sulphate of lime, when con- verted into selenite, as it often is, is also a partial pseudomorph ; though the change has been effected simply by the admission of water t- * Qeolo?Ticftl MagnziiiP, vol. x. no, 1, January 187:3. t Because i few cases havo occurred of what appear,^ to be one mineral enveloping another without change of crystalline form {e. g. prisms of anda- lusite ferruginated into a substance having the composition of staurolite), Dr. Stervv llimt has " confidently afiiinied that the obvious facts of envelop- mont," which havo led T)elesse to limit pseudomorphism, as advocated by 24 ROCK-MKTAMORPHISM. Serpentine, wliieli has never been found in a crystalline form proper to itself, not unfrequently occure in forms eharaeteristic of other minerals, as peridote, augite, hornblende, chondrodite, phlogopite, garnet, diallage, spinel, feldspar, &c. In the case of a mineral so prone to assume false forms as serpentine is, it might be expected that some of the varieties and related species would also display the like protean character. As cases in point, loganitc and picrosmine are pseudomorphs after horn- blende ; while crystallized rensselaerite and pyrallolite occur in the form of augite. The opinion that serpentine is in all cases a chemically changed or secondary product involves the idea that its sub- stance is a soluble compound. It is commonly stated, however, that silicate of magnesia, the substance in question minus H.fi, is insoluble' — that it is one of ^Hhe most stable '* compounds''^. Hence there are some who assume that serpentine cannot be affected by ordinary chemical reagents. In denying the solubility of silicate of magnesia, it does not follow that serpentine is also insoluble : besides, in this con- nexion, there are some other considerations not to be over- looked. 1st. Serpentine is a hydrous silicate of magnesia, generally adulterated with alumina, protoxide of iron, or other acces- sories (sec ante, p. 4), the presence of which make it liable to chemical reactions. 3nd f. It has existed under conditions of pressure and tempe- rature capable of materially augmenting the potency of the weakest dissolving agent that may have been in contact with its constituents. Blum, '' are adequate to explain nil the cases of association upon which this liypothe: le glacial drift lias been broken up, and its finest materials, clay and sand, washed off — leaving a mass of pebbles, cobbles, and large erratics, consisting of granite, syenite, and other rocks, piled np into an esker. This deposit has lately yielded to our examination several pebbles and blocks of syenite, in which are veinlets and isolated patches of calcite, obviously the result of changes effected in the component hornblende and oligoclase, — these minerals, where the calcite is present, \ nng more or less corroded, and having a spongy structure. Minute patches of serpentine associated with the calcite are also occa- sionally seen. When the calcite has to some extent been removed by dilute acid, there are generally left siliceous bodies in the form of rude arborescent configurations rising out of the remaining calcitic matrix, — in one instance strikingly like those that arc common in the cases elsewhere mentioned. Later investigations on the massive diorite, which has been ex- cavated during the past year (1880) in the construction of the new dock in Galway harbour, have yielded us a number of spe- cimens containing calcite in abundance, the secondary origin of which is indisputable. We have also found very recently in situ, near Salt Hill, Gal- way, a porphyritic feldsyte more or less serpcntinous, at a spot Avhere a quarry has been opened in a fruitless search foi' copper- ore. The serpentine is generally seen lining fissures, often superficially but occasionally to a depth of a few inches : it also occurs in detached pieces of rock lying about. A loose block a cubic foot in size, and altogether serpcntinous, was taken out of an adjacent wall. The mass — greyish, brownish, and olive- green in colour, has in some parts quite a soapy feel, an oily lustre, and a coarse fibrous or slickenside-like structure, resem- bling in these respects baltimoritc and pyrosclerite. These are examples of changes eftected by chemical reactions in igneous rocks, certain of whose original mineral substances having undergone replacement by serpentine and calcite *. We are now, however, trenching on chemical changes that have taken place in rock-masses — a subject which properly belongs to the next Chapter. • Specimens of the examples referred to are depo-ited in the geological museum of the Queen's College, Galway. I i: i I) I ', 28 ROCK-METAMORPHISM. CHAPTER V. MINERALIZED AND METHYLOSED METAMOKPHIC ROOKS. Metamorphic rocks may be divided into two groups — mine- ralized and methylosed, differing from each other, the one in having had the original substance of its members crystallized into minerals of various kinds, and the other in having had the same minerals altered or replaced by chemical reactions. The name pseudomorphosis, occasionally applied to the last group, is inappropriate, as the rocks to which it has been given possess no form to be imitated, and therefore no false form is involved. Influenced by this consideration, we have of late years employed the term methylosis in the case of metamorphic rocks which have had more or less of their minerals transmuted*. Ophites, which we include in the methylosed group, are so intimately related to the mineralized metamorphic rocks, that, in treating of the origin of the latter, the same subject in regard to the former forces itself on our consideration. Passing over the various views that have been held on the origin of the mineralized metamorphics, from the remarkable one held by Leibnitz in his 'Protogaea^ (1717) to the latest, as set forth by Dr. Sterry Hunt f, we propose to consider the latter, it having been contended for with a persistency and an array of argumentation +hat have won, if not their conviction, seem- ingly the favourable consideration of many geologists. * The term methylosis (/txera-, change, and vXij, substance) was first pro- posed in my paper " On a Silo-carbacid rock from Ceylon," published in the * Geological Magazine,' vol. x., January 1873. The term metasomatosis (/xera- a-oniaraxTis), applied to the same class of rocks by Von Lasaulx and Knop, is of subsequent date, and had already been employed by inyself in a memoir " On the TrimerellidfB " (Quart. Journ. Geol. Soc.No. 118, p. 140, 1874), in which I am associated with Mr. T. Davidson. — W. K. t The principal views are given by Delesse in his memoirs on metamor- phiem in the ' Annales des Mines,' s^r. 6, t. xii. 1857, &c. MINERALIZED AND METHYLOSED HOCKS. 29 Notwithstanding tlic weight of authority ou the side of Vulcwiism, Sterrv Hunt maintains what he calls a " novel doctrine/' but which seems to be similar to the one taught by Werner, and accepted to some extent by De la Beche and others, — that the vast masses of ancient crystalline rocks known aa "Azoic," "Fundamental," " Laurentian," "Eozoic," and " Archaean," have been " directly deposited as chemical preci- pitates from the seas of the time " * ; to be particular, that the Canadian Archaians, comprising granitoid gneisses, syenites, chlorite-, talc-, mica-, and hornblende-schists, and ophites, have had their component minerals (steatite, serpentine, talc, chlorite, phlogopite, augite, hornblende, orthoclase, labradorite, quartz, epidote, and other species f) " formed, not by subsequent meta- morphism in deeply buried sediments, but by reactions " |, " by a crystallization and molecular rearrangement of chemically formed silicates, generated by chemical processes in waters at the earth's surface" §. As our reasons have been given elsewhere for decidedly rejecting this doctrine, it being altogether unsupported by ac- ceptable evidences |1, there is no necessity for us to do more on * Canadian Natiu-alist, n. a., vol. iii. p. 125 (1860), t As hemitluenes are Archaean rocks, ciilcite, miemite, and some other mineral carbonates ought to be added to the list. X Quart. Journ. Geol. Soc. vol. xxi. p. 70 (1866). § Geological Survey of Canada, Report, 1866, p. 230. Sterrv Hunt, in the preface (p. 20) of the second edition, 1879 (the latest), of hia Chemical and Geological Essays, expresses himself thus : — " The crystalline stratified rocks were originally deposited as, for the moo. part, chemically formed sediments or precipitates, in which tlie subsequent changes have been simply molecular, or at most confined to reactions, in certain cases, between the mingled elements of the sediments." !| See ' Proceedings of the Royal Irish Academy,' vol. x. p. 340. Sterry Hunt has adduced in his favour the existence of Tertiary sepiolyte in the Paris basin and at Vallecaa near Madrid, " together with the formation, at the present time, of a hydrous silicate of alumina and magnesia, named neolite, a deposit from the waters in certain mines," and probably resulting from the " decomposition of the magnesian minerals hornblende, augite, and talc." But both cases may be safely set aside an totally inappo- site. The sepiolyte, instead of being a " direct chemical precipitate," has been shown by Dr. Sullivan, President of Queen's College, Cork, and Professor J. P. O'Reilly to be a secondary product, due to chemical alteration of the original deposit ('Notes on Spanish Geology,' p. 171, 1863) ; and as IMAGE EVALUATION' TEST TARGET (MT-3) /. fe ^ ^ ^■?. :/ € 1 iil'= I.I 1.25 IS i^ IIIM 1^ 1^ 112.2 2.0 t 1^ 1.4 1.6 V] 'x^^ /Tl Photugraphic Sciences Corporation ^ iV ^\ \ \ 9) 23 WEST MAIN STREET WEBSTER, N.Y. M580 (716) 873-4503 6^ ^ ./ are we to explain the genesis of the feldspathic and hornblendic rocks which predominate in these crystalline formations? The sandstones and shales from which, on this view, they arc supposed to be formed, could never by themselves give rise to the rocks in question, since tlioy are deficient in the alkalies, and to a greater or less extent in the other bases required for the production of the constituent silicates.'^ He further remarks : — " There is no good and sufficient reason for believing in the present existence of any uncrystalline represcntativey of these crystalline formations, or of any such formation which is not pre-Silurian if not pre-Cambrian in age. There are, however, many examples of local alteration of later sediments by hydrothermal action which have developed in these many crystalline minerals identical with those found in the more ancient rocks.'' to neolite (which is a very exceptional case), if it have been formed as stated, " through the agency of infiltrating waters " holding its constituents in solu- tion, the great probability is that, so far from their having beeu precipitated in consequence of *' chemical reactions," these constituents would have been deposited, like sinters (stalactitic, calcitic, &c.), by the evaporation of the water. MINERALIZED AND METHYLOSED ROCKS. 31 We certainly cannot admit that " later sediments " are with- out alkalies ; for there are several known cases which testify to the contrary : one, the Taunus slates, contains a large amount of alkalies, " more even than some crystalline rocks, such as trachyte, syenite, granite, &c. " ^'. However, admitting for the moment that these 'Mater sediments" were originally deficient in alkalies, and that in their altered form they contain horn- olende with feldspar, mica, and other alkaliferous minerals, we may be permitted to ask What constitutes the torce of the last argument ? If such minerals can be generated in " later sedi- ments " that have i ndergone " local alteration " by " hydro- thermal action," Why cannot the same action have generated the " identical " minerals which cnaracterize the Archseaus of Canada and other regions ? As to the contention that the exauples of " later sediments " are nothing more than ** local," we do not understand how Sterry Hunt (admitting some of the examples to which he may be referring to be such) can set aside the contrary testimony of the most eminent field geologists (Elie de Beaumont, Bonnard, Froissct. Studer, Delessc, &c.) that in France and Switzerland there arc Palajozoic, Triassic, and Jurassic rocks, occupying wide regions, Avhich have been converted into arkoses, crystalline schists, and other rocks containing oligoclase, damourite, scrlcite, and some other minerals, all of which are rich in alkaline con- stituents. It may be, a;j contended by ^>astaldi, Wick, and Baretti, that there are f;neisses and various crystalline rocks of pre- Cambrian or pre-Silurian (Archsean) age in the rfjgion of the Central Alps. The same may be admitted for the " pre-Carboni- ferous " gneisses in the Mont-Cenis district. But it does not necessarily follow that there are no rocks of the kind belong- ing to the Paleeozoic and Mesozoic periods in the same areas. Because Alphouse Favre has detected a specimen pronounced to belong to " Eozoon Canadense '' in the " calcaire crys- tallise associe avec serpentine enclavee dans le gneiss " in the ravine of the Mettenbach on the flanks of the Jungfrauf, Sterry • Bischof, op. cit. vul. iii. p. 129. t Kapport sur les travaiix dc la Sociele ilc Physiqiio ut d ilistoiie ualu* relle do Geueve do Juiu 18G0 a Mai 1867, p. 282. I \- n' ■i' ^1 32 UOCk-METAMOKFHISM. Hunt assumes that the rock is Archaean*. Setting aside the question whether a specimen of the kind is of any value in determining the age of a rockt, it may be mentioned that Studer long ago discovered ammonites and belemnites in a similar but less crystalline deposit, lying between gneisses, at Mettenberg near Grindehvald, only a few miles (as the crow flies) from MettenbacbJ. Hoffmann expressed his astonishment on meeting, at Carrara, with clay-slate, mica- and talc-schists and gneiss, not only fol- lowing and alternating with saccharoid marble, but passing into and blending with it intimately §. This same marble, which in many places contains or is associated with serpen- tine, is of Carboniferous age, as is shown, from its fossils, by Coquaud and Cocchi. This is no case of " local alteration ;" nor is it even pre-Carboniferous. But what shall we say of the vast region stretching from Central Italy far into the " Dolo- mites " of Tyrol, where similar metamorphosed rocks, con- taining Triassic and Liassic fossils, are predominant ? It has long been known that in the Mont-Cenis district there are beds more or less altered — talc-schists, ophites, mi- caceous limestones and saccharoid marbles, intimately asso- ciated with bed containing belemnites and infra-Liassic fossils. To those who are wedded to the " novel doctrine,^' there is no difficulty in their squaring even this case with it. Its author states — they " may correspond to the anhydrites Avhich, with gypsum, dolomite, serpentine and chlorite slate, are met with in the primitive schists of Fahlun in SAvedcn " || Conceiving it to be " improbable " for such rocks to be " of palteozoic age," as held by Gastaldi and otherS; he contends for the correctness of his view, that they "are eozoic"11 (Laurcntian or Archajan). But even should the infra- Liassic and Jurassic fossils, referred to, be able to recover their inalienable right to stand as witnesses in this case, it would not surprise us, from what may be gathered * Chemical and Geological Essays, "j-. 342. t Stnictm-es identical with those regarded as " eozoonal " have been dis- covered by us in ophite of Jura .ic age in the Isle of Skye (see Proc. of the Royal Irish Academy, n. s. vol. i. pt. 2). I Lehrbuch der Physikal-Geographie und Geologie, vol. ii. p. 158. § Karsten's Archiv fiir Mineralogie, vol. vi. p. 258 ; Bischof, op. cit. vol. iii. p. 142. II Chemical and Geological EbSf ys, p. 336. 11 Ibid. p. 347. 1 Mineralized and methylosed rocks. 33 )} ,'ith nth dis- f the vol. from the 'Chemical and Geological Essays' (pp. 3-10^341), if an attempt should be made to set aside the crystalline cha- racter of the rocks in question by teaching that it is not due to metamorphism at all^ — in short, that these rocks are no more than the ruins of adjacent pre-existing or Archisean masses, produced by the mechanical degradation, and retaining, with little or no alteration, the original mineral constituents of the latter. But passing from European raetamorphics, we beg to draw attention for a moment to evidences which exist on Dr. Hunt's side of the Atlantic. Referring to " an array of facts," he declares they ''lead me to conclude that the whole of our crystalline schists of eastern North America are not only pre-Silurian but pre-Cambrian in age",^. Hence they can only belong to "pre- Cambrian times," when, as he has stated, " there are reasons for believing there prevailed chemical activities dependent upon greater subterranean temperatures, diflerent atmospheric condi- tions, and abundance of thermal waters"!, presumably exceeding in energy those of later periods. Noav, as the metaraorphics of Westchester and other neighbouring counties are a portion of the crystallines in question, and lie within the "eastern " region spe- cified, we may safely leave it to Dr. Hunt to uphold his conclusion against the evidences of late year>5 brought forward by Profest;ors \ J. Hall, J. Dana, and others in support of their determination , that the rocks under notice, consisting of mica- and hornblende- , schists, hemithrenes, and ophites, similar to those characteristic I of true Laurentians, belong to the Upper Cambrian and Lower ! Silurian periods J. It is obviously unnecessary to prolong these remarks ; for we have only to appeal to the zone of chlorite and mica schists, gneisses, quartzites, and subcrystalline limestones (Lower Silu- rian by their fossils), stretching from Sleat in Skye to Loch Eribol in Sutherlandshire, to make palpably ciToneous the doctrine that metamorphie rocks on a regional scale have only Veen developed during pre-Cambrian periods. * Cheui. nud Geol. Essays, 2ud edit. p. 276. t Address Brit. Assoc. Dublin, 1878. X Hall, American Journal oi' Science, s^er. 3, vol. xii. p. 300 ; Dana, op. cit. ser. y, vols. xix. & xx. .1 34 ROCK-METAMORPHISM, li CHAPTER VI. WHY SOiME METAMOltnilC KOCKS HAVE BEEN MINE15AL1ZED AND OTHERS METHYLOSED. i1 We adopt the general opinion that all stratified metamorphics have been in the f.rst instance aqueous sediments, and that heated water has been concerned in developing their present features. Moreover we assume, though without knowing whether others arc of the same opinion, that, before their meta- morphisra took place, these aqueous sediments retained more or less of the water they originally contained, and that, on their becoming buried at great depths, where necessarily an elevated temperature and other favourable conditions i)revailed, this original water played a part in mineralizing them*. Adhering to the foregoing as postulates, and limiting our- selves to a well-known case in point, Ave ofl'er it as our opinion that the Archsean argillytes, sandstones, &c. became minera- lized, when at great depths, by means of the water they Avere originally charged Avith, and in consequence of the high tem- perature and great pressm'e under Avhich they Avere placed. As the Avater in such cases must have extended over vast areas, its action has necessarily been on a regional scale. Although, on our vicAv, mineralized metamorphisni has been eftected to an important extent by the intervention of Avater, it must be admitted that the evidences are not very abundant; for the resulting minerals are Avholly anhydrous. The strongest evidence consists in the presence of liquid bubbles (aacII known from the researches of Sorby, Zirkel, Allport, and others, as occupying cavities) in the quartz, feldspar, and other minerals chai'acteristic of the mineralized metamorphics !• * It was to be expected that Sclieeier, avIio advocates the nqueous origin of gmiiite, would ninko this rock to contain its " primitive water." t Natrolite, talc, chlorite, and other hydrous uiinernls iu giunite, accord- CAUSES OF MINERALIZATION AND MLTHVLOSIS. 35 The auhydrous- character of the minerals referred to seems to favour the idea that heat and pressure, more than water, have been the agents in effecting the change Me have assumed. On this account the change may be t rmed xerothermal, parti- cularly . . the aquosity of the rocks in question seems to l)e but slightly more than would be an a(.'companimeni of dry heat. The methylosed section, there can be little or no doubt, has been largely under the influence of water ; for a great portion of the minerals composing its members arc more or less hydrous. This fact, and a number of relevant considerations, warrant us in assuming it to be extremely probable that water derived from extraneous or foreign sources, as seas and lakes, has copiously permeated mineralized rocks, — thus giving rise to various chemical reactions within them, ending in their methylosis. The change produced in methylosed rocks, compared with that which has taken place in the mineralized section, justifies the use of the generally adopted term hydrothermal*. Since the import?' ut discoveries made by Daubrec, showing that various minerals (zeolites, hyalite, calcite, diopside, &c.) have been developed among the bricks and mortar of the old concrete work of the lloman baths at Plombieres, in the Vosges, through the action of subterranean alkaline water, with a tem- ! peraturo of from 59° to 1721° Y.f, it can no longer be held as^ an unwarranted assumption that similar chemical changes have; been eft'eeted in rocks through the latter becoming saturated' with superadded heated watery solutions |. known iiig to Storry Minit, show that water was not exchuled iVoiii tho original gmnito paste (Cheni. & Geol. Essays, p. ^). We regard these minerals as o^ secondary origin, resulting from the admission of water into the granite after its formation. * We find that Buusen has designated this cliange hyihitothvnmc, and its opposite pyrocaustic. t Ann. des Mines, 18of<, &r. t Daubree has already i-nggestcd that the water mechanically contained in rocks, commonly termed qnavry-water ("eaii do carriere"), ajipears to be all that is required to develop, Avhen assisted by heat, very energef • action ((Juart. Journ. Geol, Soc. Vol. xvii. p. xlix). 1)2 36 mHK-METAMoHnilSiM. CHAPTER VII. THE MI:T11YU)T1C OKKilN OF Ol'lIITES. AVmi rcspocl to the rocks now (Mitorcd upon, we have evi- dences in the pseudoniorpliic origin of tlicir (\ssentiiil mineral, serpentine, that something more than ordinary metainorphism has heen concerned in dcveloi)ing their present cheniical cha- racters. According to Hisehot, " When pseuciomorphs sliow that a mineral, H, may originate from another mineral A, it is possihic that, under suiti'.hh' conditions, all minerals corresponding to A, may undergo such an alteration in the rock where they occur. This may he the case even where the former mineral is not in a crystalliiu^ state, hut exists in the rock as an amorphous mass"*. Hence, as serpentine is always the product of che- mical change, it follows that a rock, when it is entirely or essentially composed of this mineral, must have had a pseudo- morphic or, more properly speaking, a methylntic origin. This doctrine, applied to ophite, has been decidedly opposed by Sterry Hunt, w ho, having rejected the pseudomorphic origin of serpentine, both as a mineral and a rock, maintains that, in the latter case, it is a chemical precipitate, like the gneisses and other metamorphics usually associated witli it. On the I contrary, it is seldom that any other miiieralogical geologist 1 speuks of serpentine or ophite otherwise than as being a pro- j duct of chemical alteration. Blum considered there was good reasou for believing all ser- pentine rocks, including their contained minerals, to be of this origin. Referring to the presence of pseudomorphs after augite at Mouzoiii, in the Tyrol,' he states "it is not merely the * Cheui. i^ I'hys.A'Cokitfv, Kii;:l. cd. vol. iii. pp. Go, 6U. METHYT.OTrf ORTfllN OF OPHTTF.S. ')7 fine aiif^itc rrvNtals (riissjiito) which orfur, mixed with cnlc-spnr, ill tho (Inisy cavities and fissures, hut tiu; whole mass of the rock is eonvcM'ted into serpentine "*. The change of bedded diorite into serpentine, in tlie Saxon ^/t Voigthmd, h'(! Itreithanpt to suggest that th(! hitter is the result C^^ of* an alteration of th(? former. r,/^' * (lustaf Hose and Hiseliofeven went so far as to maintain that aerpentii\e may have originated not only from the most widely diverse minerals, ])nt from widely diO'ercjnt kinds of rookf. I'jvidencesfavonring or demonstrating this oonelnsionliave been made known by Blum, H. Miiller, Naumann, Mernard von (-otta, Fallon, Pelesse, F. Sandbergcr, Allport, Cunninghame,rJ/^*^*^ Heddle, lionney, and others. The (Jalway examples we liavc . -P cited induce us to take the same view. J Sedgwick declared that he was "disposed to consider certain varieties ol" serpentine as a modification of diallage rock, rather than a formation distinct from it''|. Sedgwick, no doubt, in- cluded the serpcntinytc of the Lizard in this view ; and we should readily have agreed with him as to the character of this rock, but for the fact that what seems to have been taken for diallage we have shown to be pseudoKiorphie after crystals of common lilack augite§. The fact, also ^itated by us, that the lizard serpentinyte closely agrees in its porphyritic structure with the dolerite (wakite or melaphyre) of Hufaurc, in the Tyrol, inclines us strongly to the view that the former was originally a rock similar to the latter. Moreover we are prevented from agreeing with the Rev. Prof. Bonney, who, though tacitly adopting our view as to the methy- lotic origin of the Lizard rock, concludes, from finditig it to contain what he regards as enstatite (which we take to be the pseudomorphs named above) and peridote, that it is an altered mass corresponding to lherzolite||. Other testimonies in favour of the methylotic origin of ophites have of late years appeared. Professor Heddle, who has lately * Bischof, Chemicftl and Physical Geology, vol. ii. p. 322. t Ibid. vol. ii. p. 417. X Trans. Cambvidgo Phil. Soc. vol. i. p. 321 (1821-22). § London and Edinburgh Phil. Mag. ser. 5, vol. i. pi. 2. fig. 2. Seo aiso concluding portion of Chapter III. and footnote f. II Quart. Journ, Geol, Soc. vol, xxxiii, p. 921, Sec, J- \jfJ' lA- mmm 38 ROCK-METAMORPIIISM, ! ; ■■ i H |)ublislio(l some important nnd rcliablo details on the pheno- mena in (Hiestion in his I'onrth cluipter on " the Mineralogy of Scotland," thus cxijiesses hiniscH': — "All the serpentines of Scotland which I have had op|)ortnnitieH of properly atndyin*^ arc nictanior|)hic nu'ks, I'ornied for the most part by a ehaugo ol' angilie and hornbh ndic rocks — as diallage, enphotidc, and diorite, "The serpentines of Unst in Shetland are derived from diallage. Of the two beds to the west of Portsoy, the first from gabl.ro, the latter apparently from cuphotide; the beds to the cast, from a rock chiefly augitic. " The peculiar structure of the serpentine of the hill of TowanricfP would lead to the conclusion that gneiss was the original ; but the nearest rock is a laminated diorite, composed of labradorite and black mica. Though tliese conclusions arc chiefly the result of geognostic observations of the district, there are many localities where the transition may be traced through a gradual change in the minerals composing the rock. Such comparatively molecular transformation may be well stu- died on the north shore of Swinaness, in T^^nst, in several places in the neighbourhood of Portsoy, on the north side of the hill of Towanrieff, and on the northern slopes of the Green Hill of Strathdon. At the last-mentioned locality there may be ob- tained unaltered, or apparently nnaltercd, diorite ; — the same with the hornblende duller in lustre and softer than normal, and the felspar dull, semi -opaque, and of a greasy lustre ; — and lastly, almost perfectly formed serpentine, in which, however, the granular structure of the altered rock is plainly visible. These three occur within the space of a few feet of each other. It is not, however, easy to select for analysis, from rocks — the several erypto-crystalline ingredients of which give way to the transmuting agent at different periods of time — specimens at once typical and sufficiently pure. I have met with more success in this direction in v/orking among the serpentinous marbles — those which contain imbedded granules or patches of serpen- tine — than I have among the larger masses of the serpentine roek itself. " One fact I would direct attention to, seeing that it has perhaps not been clearly enough considered, namely, that great beds of serpentine must have been formed by the metamorphism h METIIYLOTIC OKIOIN Ol' UPU1TE», 39 of pro-oxistcnt rorks as a whole; that altlioufjli thn rhangc took plaop stop by stop, ono iii^rnliciit f^iviiif^ way l)ofor(; another, still, ultimately, all participated more or h^ss tliorou}j;hly in the (•iiaii;;-e. The molecular or erypto-erystalliiie {ranHfonuatiou had thus as its result a litholof^ieal transmutation. To he nu)re precise, Mhero a fj;reat bed ol' diallaf;;;e roek has been converted into McrpcMitine, the I'elspar as well as the augite has ^one to t'oru) the latter. This nuigncsian nu;tamorphosis of labradorite docs not seem to have been sulllciently rocognized ; but though the general rule is that the augitie niincral is tin; first which suH'ers altcM'ation, there are localities in which the felspar would hcem to have be(Mi first adeetcd. It is true, that in many cases the felspar uvxy not have been couvert(!(l into true serpentine, but merely into an impure kaolin, which, disseminated through- out a serpcntinous basis, may defy iiwlividual recognition, from the similitude of kaolin to serpentine itself. Sucli an inter- mixture may account for the large quantity of alumina in sonui serpcntinous rocks; iruleed, any serpentine roek which contains much alumina may bo held to have originated from a jjrimary rock, of whi(;h one or other of the felspars Avas an iugre- dicht"^-. Some years ago Mr. (1. II. Kinahan, District Surveyor of the Geological Survey of Ireland, directed our att(uition to some interesting points in the geology of South Cannaver Island, in Lough ('orrib, which " show the gradual change of hornblcndic rocks into serpentine.'' Since then ho has pub- lished a brief notice of tlie island in the * Explanation to accompany Sheet 95 of the Map of the Geological Survey of Ireland/ p. 33 (1870). Having examined this island, wc fully agree with Mr. Kinahau in the view he has taken of this case. Much of it undoubtedly consists of "metamorphic irruptivo rocks;" and the one with which we are more particularly concerned was undoubtedly a hornblendic mineral en masse before it assumed its present character. Plate VII. represents a specimen, now a dark olive-green serpentine, having a well-developed crystalline structure. Plate VIII. represents a specimen of grey tremolite, a variety * Trans, lloyal Society of Edinburgh, 1878, vol. xxviii. pp. 401, 402. ,fr i> 10 KOCK-.MKTAAtORPHISM. I of lionihleiult;, iVoiu St. (iotliard*. Tlicrc is notliiii}; l)y which the eye vnw dettot a (litrercncc between these specimens, except eoh)iii't : both consist, for tlic most part, of bundles of slender radiating prisms, with frayed-out or divided terminations and a distant transverse cleavage ; and so strikingly alike are the specimens as to make the one a|)pear as if it were a facsimile of the other. No clearer proof of the pseudomorphosis of serpentine after tremolite could be adduced; nor could a more decisive case be brought forward showing a dioritic rock raethylosed into ophite J . Of late years there has been a growing disposition among geologists to look favourably on tiie view that ophite, or its essential component, serpentine, has originated from peridote or from rocks (peridolytes) rich in this mineral. ¥. Sandbergcr, (r. Tschcrraak, Zirkel, and Bonney may be classed in this school. It cannot be denied that the common occurrence at Snarum of pseudomorphs of serpentine after peridote, and the frequent association of the two minerals in other places, may be taken as good evidence in favour of this vieAv ; but it would be just as reasonable to assume that basalt, because it usually contains a large proportion of peridote, was generated out of masses of this mineral. Zirkel has noticed, in a precited memoir, the occurrence of ^' small, roundish, sharply defined crystalloids of serpentine " in the " crystalline limestone " or hemithreue of Aker and Sala in Sweden, Snariim and Modum in Norway, Pargas in Lapland, and Lough Derryelare in Connemara; and he maintains that they are the product of alteration in peridote, this mineral often being present in the crystalloids as a core. We shall endeavour to show in another Chapter that peridote is as much a secondary product as serpentine, and that, on this • According to Damour (Bischof, Chem. and Phys. Geol. vol. ii. p. 348), the St.-Gothnrd tremolite consists of SiO.. 58-07, MgO 24-46, C'aO 12-99, FeO 1-82. t In some instances tlie j)risms retain their original colour. X Mr. Frank Rutley, who takes this to he a serpentinous rock, states that some of the long radiating crystals it contains '' display magnificent variega- tions of colour under polarized light " (' The Study of Bocks,' p. 131). Sections examined by us show nothing more than the coloxu-p of ordinary serpentine : probably Mr. Rutley's case contains peridotic matter, I METIIVLOTIC ORIOIX OF OPHITES. 41 view, it has boon gcucvated out ol' minerals containing silicate of magnesia and oxide of iron, sueli as hornblende and angito : it is rooks composed of minerals of the kind, and which are frequently methylosed, that form the principal repositories of peridote. We feel certain that Zirkel will not be able to explain the origin of the " crystalline limestone " which encloses the ])seudomor- phosed crystalloids without availing himself of the aid of methylotic processes. Moreover it may be considered that the presence of peridote in rocks which have undergone chemical changes is a barrier to this mineral being regarded otherwise than as a concomitant product of such changes. For our part, we arc accjuainted with sufficient evidence to sustain us in the conclusion that serpentine, instead of origi- nating from any one mineral in particular, is polygenotic. The numerous examples we have lately found arouiul Galway (and their number increases by every fresh examination) of sorpen- tinized granite, diorite, porphyry, and feldsyte, may be safely accepted as completely confirming the view, held by Rose and Bischof, that serpentine may be generated out of widely different rocks and minerals, admitting at the same time the magnesian- (jonstituent to have been derived from foreign sources. We are even not averse to the view that serpentine or ophite, hitherto limited in its derivation to silacid rocks, has in some instances been produced from chemical changes in carbacid deposits. From what may be observed in the dolomitic lime- stone in immediate contact with the diorite of (.Wzocoli (at which junction, a few hundred feet up on the flanks of this mountain, one may sit on both rocks at the same time), near Predazzo, no doubt can prevail that the layers and patches of serpentine present in the limestone are a local development, due to dis- charges of silica, in some form or other, from the adjacent igneous rock"*^. This is the only instance that has come under our notice of a V ' i ■ -•^ 'i 4 i w -i r; 3 1 ^ J V ■ A >• * On a former occasion we made known that the Isle-of-Skve Jurassic ophite is in some places, as near Torrin, lamellated with the same mineral substances, and in a similar style, as " eozoonal "' cphite: specimens collected by one of us at the Couzocoli junction are precisely similar. It is noteworthy that the serpentine is occasionally replaced by a mineral substance, seemingly loganite (as at Bnrgess in Canada), the latter occurring interlamellated with hydrous dolomite (predazzite). I I I J 42 ROCK-METAMORPHISM. oarbacid rook liavinp^ become serpentinizf^d, unless it be the " qficakes " that han^ on to the dykes of cnphotidc, and tlie adjoi:}ing disrupted beds of alberesc limestone, in difteront places between Genoa and Spezzia. In this connexion it may bo remarked that such instances may be taken to support the view, held by J. Dana, that the West- chester hemithrenes were originally limestones, and have siince been impregnated with silicic acid. Another idea as to the origin of ophitic rocks Avas In'oached by the late Prof. 11. Harkness. It is thus expressed : — " The serpentinous limestones of Connemara arc of local occurrence ; they usually appear in such districts as exhibit the strata highly contorted and broken up. The lines of lamination in the lime- stone stra,ta have been opened, and the larainse have been frac- tured across, in consequence of the contortions to which the strata have been subjected ; and into these openings and frac- tures the serpentine has been subsequently introduced. ... In the calcareous band which lies east of Lisonghter, and which extends to near Oughterard, the laminaR have not been opened and broken by contortions ; and from it the serpentine is absent"^. This hypothe^iis, which appears to us to be more ingenious than sound, we consider is based on insufficient data obtainable in tlie field and the cabinet, * Quart. Jouru. «:}eol. 8oc. vol. xxii, pp, 50!) Sc 511. ',l:iS^'>^.K,Si^" ■!|fi;3KSf .? SERPEXTINIZATION WITHOUT MINERALIZATION. 43 CHAPTER VIIL SERPENTIXIZATION EFFECTJ^I) IX 'JEPOSFTS WITHOUT THE INTERVENTION OF MINERALIZATION. As certain fovmations, such as coal, anthracite, dolomite ■'^, &c., arc methylosed produc^^s, and nevertheless possess no evidence of their having been otherwise than in the ordinary amorphous rock-condition, it may be fairly expected that there are forma- tions, closely related to the ophites, which have undergone chemical changes without having been previously mineralized. Many argillytes arc known to contain silicate of magnesia, which makes them more or less stcatitic, talcose, chloritio, or serpcn- tinous, against which objections might be raised as to their being allocated amongst typical ophites. Mr. J. Arthur Phillips has made known several cases of Cornish " killas/' which, through a decrease of alumina and an addition of magnesia, departs from its normal condition, and passes into a substance approaching to ophite f. In these cases the rock approximately retains its original amorplious condition, having, in most cases, little more than the ordinary texture of slate or argillyte. Some of th^^ agalmatolytes have all the appearance of being similarly magnesiated formations. There .^eems to be no reason, then, why the serpentization of killas, or any other argillaceous rock, may not become so far advanced as to convert it into an ophite. We arc, accordingly, led to conclude that certain rocks of the kind, * Beds of nrgillRceoua limestone nre occasionally converted, na in Derby- shire and other places, into rottenstone (essentially aluminous) through their calcareous portioTi liaving been removed l)y water containing carbonic acid. And much of the alabaster of Nc.rthern Italy, the Tyrol, and the Tliuringer- wald may be methylosed limestone ; but in thia onm sulphuric acid and watev have replaced carbonic acid. t Philosophical Magazine, ith ser. vol. xli. pp. 87-100 (Feb. 1871). 44 ROCK-METAMORPIIISM. I I i- originally argillaceous, liavo passed directly from the earthy condition into their i)resent form. ''A very homogeneous slate, from the Villa llota, on the Po, was found hy Dclesse to have a com])ositioii so closely reseml)ling serpentine, that it might be regarded as schistose serpentine"*. But a more decisive case may bo predicated of one lately made known by Achiardi of Pisa, occurring at Podermo in Tuscany : it consists of argillaecouM schist methyloscd into a green trans- lucent serpentine by the action of subterraneous water liokling magnesia in solution, this substance having gradually replaced the alumina of the schist f. Delessc, who !»as noticed the case, mentions that he has observed a similar change at Oderu in the Vosges {. The hydrous silo-magnesiau marl, sepiolyte (classified by some writers with the minerals aphrodite, talc, spadaite, and others, but diftcring from them mainly in containing more water), which occurs as a Tertiary deposit in the Paris basin, and at Vallccas near Madrid, is another instance ot a formation which, although it has undergone a chemical change §, still re- tains its original earthy or amorphous condition. Reverting to the case made known by Achiardi, it may be mentioned that Bisehof has shown, from the presence of chlo- ride of magnesium in the water of many springs, that " the formation of silicate of magnesia may take place by the action of such water upon silicate of alumina in the form either of clay or compound silicates " ||. * Bisehof, op. cit. vol. ii. p. 410. t R, Com. Geol. d'ltalia, Bollettino, 1870, p. H. X Revue de G-Jologie, 1878, p. 191. § See footnote, p. 28. !| Chemical and Physical Geology, vol. i. p. 344, and vol. ii. p. 107. OPHITES^ SEDIMENTARY AND IGNEOUS. 45 CHAPTER IX. MANY OPITTTES WERE SEDIMENTS, AND OTHERS ILJNEOUS ROCKS ORIGINALLY. ll^NTiL the discovery ol' stratified ophites in the Laurentiaii series of Canada, tew geologists tliought otherwise than that the rocks under eonsideratioii were of igneous origin. Most of the opliitcs known on tlie Continent favoured this view ; and, not- withstanding the'r mineral and plainly bedded characters, the ophi-calcites of (Jonnemara, it was conceived, were no more sedimentary than tlu whin-sills of the north of England and other stratified dolerites. The discovery that the Canadian ophites were the products of sedimentation, it may well be imagined, greatly perturbed the opinion which had prevailed previously. It next behoves us to mention that for many years before Canada had been geologically surveyed, mineralogists, through the researches of Blum and others, had become acquainted with the fact that serpentine, the essential mineral of the rocks in question, is a product of the chemical alteration of other minerals. Still few geologists seemed to appreciate in full the bearing of this fact upon rock-masses of serpentine. Again, the discovery of the presumed organic structures in the Canadian ophites by Logan, Dhv son, and Carpenter, was generally admitted to be a fatal blow to both the igneous and the chemical -alteration tlieories. The evidences educed by our investigations connected with the last-mentioned discovery, however, liavc unexpectedly led to conclusions totally different from those which originated in the Canadian school of geologists. What has already been stated makes it quite unnecessary to dwell further on this point : suf- fice it to say, that the conclusion we have adopted as to the origin of ophites is the same as the one foreshadowed by the re- sults which attended the labours of Blum and others on mineral pseudomorphism . Having already noticed in detail the ophites of sedimentary I \ M\ HOCK-MKIAMOUI'HIhM. origin. >\r slmll moioly ni^Kr ;i \'v\\ hriiM r«'miU'Kfi on tlmsi' Mhich «riv orifiiiial!y ordinnry igurods locK'*. As srrniingly rnvouiahU^ to \hv gcnrral view fonurrly lu'M ivsporliuft \\\v origin ol llio Counrinara ophilrs, our iH of tin' Cannavi'r scrprnlinylc uml«M' cirouniNtamM's dtMnonshativc of its bring an " irrnpiivc rook" (Inii luul inulorgonc nirla- niorphisni. Wo ;»groo wilh Mr. Kinalian in (liis view ; for, Mholhov originally consisting of (r(Mno\itr (M' coininon diorilo, tho rooK, Mhioh nuisl bo rogardod as baving hvvw ignoons in ibo lirsl instanoo, bas booomo obangoil, tbrongb nictbylonis, into a mans of sorponiinc*. In \H7(\, aftor an r.vaniination of t\\v liizarti in Connvall, \\c sbo\V( d in a prooilod nionu)ir tbat tbo frrponlinylo ooourring tboix^ was originally an ignoons r«>ok, rolatod to tbo porpbyritio waokito or dolorito of Hnfanro. (\>ntinonta1 goologists bavo bivn Ir.igoly intlnrnood in tboir b( liof as to tbo origin of opliitos by tbo ooonrronoo of rooks of tbo kind, in tbo form of dykos, in Nortborn and (\'ntral Italy and otbor <'ounlrios. At Trato, Iniprnnotta, Voltcrra, &<'., in tbo Uay of »^}>07/ia and tbo adjaoont distriots, cnpbotidos, doloritcs, and otbor ornptivo niassos aro www or loss sorpontini/Anl into opbitos ; so tbat tlu^ Cbovalior .lorvis, in stating tbat tbo lattor aix* diivct ignoons prodnots, oxpix'ssos tbo opinion provalont among Itaban gx\>logists f' Allport, >vboso niioiHwoopio rosoarobos among tbo basalt i«', dykos of Kngland, Scotland, and In^land bavo dono nuiob to ostabbsb tbo psondonun'pbio origin of sorpontino as a mineral, bas brougbt forward numorons o\idoncos mImoIi oqually sliow tbat tboso niassos arc convertible into opbitos. Pr. Heddle, one of the latest writers on tbo snbjoct, bas made it clear, as previously noticed, tbat many of tbo opbitos of Scotland were originally true igneous rocks. But for tbc eozoonal scbool it would seem superfluous to add that the fact of some opbitos baving been originally cWH/u/^/^/r//, and others tgvuons, may be beld to demonstrate tbat in both kinds of rocks their mineralogiral idiniiiy can only be due to one and the eame causation, metbvlosis. * The \»&n\M orupti^"c andiguoous arc to bo l«keu iu ft couventiouftl senso, n.- applying to roclcs nof of sedimentarv ongiii. 1 Mineral Kc>ourc«?s of Central Italy, cliap, iii. 1S08. :!&.. iir-MnmuNKfl anh nmiji ( ,u,( iii« noi-Ks. 47 CHAPTER X. TiiK MirniYinnc oiadiN oi nivMrrniiKiNEs ani» OTIIKIl IM'ILATKI) i'MA'lTU' l.'OCKH. In Norvviiy thrrc am in Hcvrrul placcfl, aHROciatcd with uivin- nn)V|»lii«' I'ofkH, crvNldllino ("iilcfirrouH rnnsscM, cjillrd by Sciiiidi- iinviim {j;r()l()p;iRrp dyvcloped from the change in ([ucstion, it may be Icgitinnitely inferred that if n certain rock -forming mineral silicate, say augite, has the substance of its crystals replar!(!d by calcite, there can be no reason why a rock essentially composed of the same mineral, and occurring under suitable conditions, cannot become calcitizcd. Bisehof, it would appear, wjis not averse to this view; for in speaking of granular limestone or * 'flio 11(11110 iikorlvh' was ]iin|i(i8ed fur tlic-io lockH in uiy paper already Vi't'ciTed to; but, from whnl h stiitud in the text, iiiy collen^ni*! find I Ajel it right t'> ndnpt JiruiigaiarlV yurli«r juinio in prufwrcuco. — W. K. 48 ROCK-METAMORPIIISM. saccharoid marble when it occurs as ''subordinate beds in crystalline slates," he considers that in this case " the carbonate of lime may have originated from the decomposition of cal- careous silicates "*, which, it must be understood, are frequently present in the latter rocks. That such cases have already been made known l)y Scheerer, Delesse, and others, though their origin has not been rightly understood, seems highly probable. Leonard Horner, in his Presidential Address to the Geological Society, 18G1, remarked that '' numy instances have been met with of granular limestone occurring under circumstances that can only be explained by supposing them to have had a sub- terranean origin." Besides other instances, which Horner might have had in his recollection, probably the following, cited from MacCulloch, was not unknown to him : it consists of an " irregular or nodular mass of limestone (pink coceolite marble) enclosed in gneiss without any connexion or coiitinuity "•)-/•">''• '^^'''. Recently, Professor Heddle, referring to the "primary lime- stones " of Shetland, has stated that they are " often very obscurely or imperfectly stratified, while occasionally they show no marks of that deposition, but rather seem to form, like serpentine, large imbedded shapeless masses, or huge irregular nodules ":|:. Selwyn, speaking of the dolomites and limestones associated with the " diorites, dolerites, amygdaloids, and volcanic agglo- merates," presumed to belong to the Levis division of the Quebec rocks in Canada, has lately remarked that they " have much more the appearance of great lenticular, vein-like, cal- careous masses than of beds belonging to the stratification" i^. Putting aside a number of cases which could be adduced from different writers, we shall confine ourselves to a few with which our personal observations have made us intimately acquainted. In the summer of 1877, F. Twining, Esq., of Cleggan Tower, north of Clifden, Connemara, drew our attention to a dyke (not marked on the map of the district by the I^i^h Geological Survey, which had just been published) dii'tlie north shore of Cleggan Bay, immediately adjacent to a small rocky islet or, * Chem. & riiys. Geolojfv, vol. iii. p. 140. / /^ .i^Tlree' ■'* Westeru Islamls of Scotland, vol. i. p. 48 (1810). \ The Miuernlogical Magazine, vol. ii. p. 118 (September 1878). § Canadian Naturalist, vol. ix. p. 24 (February 24, 1870). H leerer, •ightly logical 11 met ;s that I sub- lorner :, cited of au larble) lime- very low no iitiue, iated gglo- the have cal- from hich ted. wer, dyke gieal re of or, HEMITHllKXES AND OTIIKR CALCITIC HOCKS. 4-9 3. rather, promontory (called Cjjassilhiiin), separated from the main- land by a ditch-like channcl','lc6ntaining water only at high tide. The rocks of the locality are well-bcddcd mctamorphics,; 5 slightly dcvek)ped as such, consisting of (piartzites, micaceous and hornblendic schists : they dip to the north at an angle of (50°, and strike east and west. Here and there they possess some exceptional features. Platf; IV. represents a ground-phm, and Plate V. a iiatuial vertical section of this case. The dyke, which is JiO feet wide, intersects somewhat obliipiely the metamorphics at the head of a small cove or inlet in a north and south direction. It is seen in the face of the cliff, which is about 20 feet in height; thence it passes southward into the sea. The cove is bounded on its east side by a narrow projecting mass of rock, and on its west by Glassillaun and a portion of the mainland. The dyke, of a dark grey or nearly black colour, and finely crystalline in structure, consists essentially of the mineral silicates — augite (or hornblende) — in long crystals, a granular feldspar (possibly labradorite) , and a platy one looking like ortho- chise. A little magnetite is also present. Calcite often occupies narrow interspaces between the siliceous minerals, causing the rock, on the application of a weak acid, to effervesce slightly. The metamorphics of the promontory, principally of the kind common on the adjacent mainland, are strongly bedded, with indications of lamcllation j but in certain places immediately adjoining the dyke the beds become changed into bands and intrusive-like masses, distinctly striped with green and pale brown (due to the alternation of layers respectively distin- guished by these colours) , and varying from an eighth to an inch or more in thickness. Tlie ditch-like channel was at one time entirely occupied by one of the bands ; but, owing to the softness of its component layers, the band has been in great part washed out. and an open separation has taken its place. On the east sideTif the cove the sane striped rock is also seen, but in small portions, enclosed, as it were, in the gneiss, into the bedding of which the layers pass uninterruptedly : on the west side it forms intrusive-like masses, which pass imper- ceptibly, occasionally abruptly, into the adjacent gneiss ; but their striping is in some places strikingly undulated, and appears to be independent of the lamcllation of the gneiss. E no »\0» h MK» AMOlUMn<»\l. I i>onsi«st of (1;i(ton(Ml vivlintinfj ttH'ls o( (nMuoliti^ i\\u\ lonjs; nystnln iM 1iovnM«M\(U\ bolh tnl'lx mul rvynljil'* Ixinjj Mitli \\\v\v lon^ nsi^ ^^nvnllcl to \\w liouiuntiou. Intrimnrd \nll\ tlicsr nnm'vnls nvr ^>orido1o ^hoantirtil ni n, n vjwjoty of llu' IsiHoi uMM""'''"''\ pyroHrlorilr) fonninfi xoinlols. ',\\u\ tlilovito in snuill qnnnlily ; \\\v \Miv\- \\\\\\ovn], \w\\v\'fy, is nhnndnnl in sonn> s|MMMni('Hs. nsRoi'inird witli Rro\\n hiyors oonsisi ol' nnilin'olilc, ft s1r\j>rd I'oltUpsn . inni ortloito. Tho niivlnoolilo, hanslnrrni innl 0|>nqu<\ is in di o]>fn]tn' l\n\o ns\inlly n (lo(>onlon< voni ; \\]\\\v <1ioiv angles anti o«if>-<^s a\'o nior<' ov loss nnnnlod, {livinji; i'i«(> soo1'll\o nialaoolito ; and nhoir nsisvith ^mwimiI in ral silioafos and a mineral oarhonalo ; and as snoli if nuist bo oon- sidon'Hi fo Ik-" a Irno hon\i1hivno. Mv. IVining's ohsorvalions, kindly niado M onr dosir<\ niako t^ e pmnionfory !i>(X) f«>nldei>, and heaeh-sand. An opj-vorinnify will (venr hereafter, enabling ns to acconnf for the presence of inn-idv^te it\ mcthyloscii rocks ; mo may thei'efoiv confine oni-sclvcs to the serpentine and caleite of the hcmithrene in this instanc(\ The serpentine is so associated ^ith the trcmolitc as to make it evident that the former has rcstiltcd tVom chemical clianges effect (^i in the latter : and there IS nothing mc»rc certain than that the ealcite stai\ds in the same relation to the malacolitc. That water has accompanictl the changes is pmvtni by the pi'csencc of sicri>cntinc in the hcmithrene ; and the fact that IIIMII'IIHKNI:*) AND MTIIKIl ( Al.riTlf RlH K«. 51 WW to 1 ystnls w\h nvr UFi inui I'lt'vilr) - Inllrv ocininl lU'olih', 'Ui inul I'^rtioil : ; wlnlo ; ri«o i'Hicilr u«ly tli- u> rvys- liuril in i> Inyovs 1 jvonu)- 1)0 oon- . lualvo rl into (tovy 51 luM'lift", SiUul. nooouut MO niiw • loito of soiiatod wor has (1 (hoixj \o 5«ainc bv tlio not that iiiliilo uit'iiiN in I he ilyko may lie liikoii ih |i(iHiliv«f ••vi'loiiic n oai b(nia(o ui'oaibiinio aoid in •solution ' . In addition lu tho ini|M)ilanl oridonoo nliiih )ho honiilhiorn' ii( Mnnt Sainf -l'hili|)|io has aJToKh'd in (Mnnivi'in with Iho ihoniitid ( han{»0H oM'oolod in ininoiidH, uo have ncsl In make kM^l\^n stnno laols IVnin Iho nanio |dao(^ which boar dirootly i^n (ho nnillor tnidor o(»nMi(h'i'atinn. The rofjiitn plaros naniod (horo in a dovolopnuMil ol' honiilhion A \nv^v (pnti ry oC IImm rook ("' oalcairo Haooharoid(> ") is worked at St.-1'hilippo. It isu lu'arly roclan^iilar oxoavalion, about (K) or 70 paoos lonp;, JU) pacos wido, and 15 foot in dopth. Tho rook, ol a highly orystallinn oharaotor, is lor tho njost part well «(rati- liod, as is also (Ih> (iRsooialod fjnoisH : both dip in tin; sariKMliroo- (ion {^(Milh-ouMt), at an an^lo oi' abont lit)'. Tho hoinilhrono, li^ht in oolonr, i'^ inorotn' Iohm olnirji,cd with pyroMolorito, ohiolly in grannies; and tho Haino niinoral ooonrH, but rarely, in tli(^ iinniodiaUdy adjaooni portions ol' Iho gneiss. Tho pyros(;lorito and olhor mineral .silioatos, as pn>vionsly notiliod, are irromilarly int(Mini\od with oaloito; but very ot'ton tho diHoront kinds (oar- bonatos and silioatos) arc dinposod in layers : on aooonnt ol tln^ latter arrangement tho bods have assumed a laminated Htrnotnro. Tho lamination is ot'ton irregular, being variously nndnlalod, and separating horo and there through tin; interposition of com- pressed lumps whioh consist internally ol" a white granular oi- * Quart. ,1011111. Uool. HyH\ vol. xvii. p. Iviii. A hIioiI tini<> n^n IWcoggoi icjx ftiul Uovoli ol).>»orvi'il lit JliiisiMi, in Norway, " a voiii ol' lioiiildondf! cliangod into (I mass of calcsjiar" (('aniuliiiii Niitumliat, ii. i*. v(j1. viii. p. 4oO). Jtotli tliii* case and tlio eiiloitlLHl iloloritic dylio at Cit'ti^giia may be takuii to provo tlial tl\(> \V('ll-kno\vn caloilii' dvkc. (riivoi-.Miig iiiotaniorpliic rockn nwir Auor- bu'li in iJorg-JtriiMso, tii\st dosoribtnl by Von (JCyiiliaukMi luori) than lil'ty years i>^i. was originally c .-^ilacid igneous inasp, and f*iuco convert od into henii- tluone: its accessory luiuorals (liornblondc, Iremolito, idocrase, wollastonitM, epidoto, and tbo like) favour this view. i I' !l ! ! \. ( I r,») HOCK-METAMOKPHISM. amorphmis mineral, considered by Dclcsse to he fcldspathic and related to liiilleflinta : this part passes insensibly into a eoat of pyroseleritc ; and the latter is snrrounded by phlogopitc. These lumps have consecjuently a concentrie structure. The gneiss, dark in colour, consists of layers of opaque ortho- clase, translucent plagioclase, dark bronzy mica, and dark green hornblende : quartz is more or less irregularly intermixed with these minerals ; also, as accessories, garnet, pyrites, graphite, and sphene. AVherc the gneiss and Iiemithrene arc in immediate contact, their respective minerals are intermixed ; nevertheless both rocks are well diftcrentiatcd, and readily distinguished from one another. The hornblende unmistakably changes into pyroseleritc, as is also the case Avith the augite ; and the least reflection must make it clear that the two minerals plagio- clase and malacolitc have contributed to produce the eal- cite : besides, according to Delcsse, the dark bronzy mica of the gneiss has become magnesiated into the lighter-coloured phlogopite which characterizes the heraithrene. Moreover it is highly probable that the caleitc, where it is the dominant con- stituent, has been increased by carbonate of lime brought in by water from extraneous sources. Figure 1, Plate VI., represents a section, about 13 feet in height, showing the gneiss and hemithrenc in contact, as seen on the right-hand side of the quarry near its entrance. The beds of gneiss (coloured red in the figure), it will be seen, come in between two masses of bedded hemithrenc (coloured green) rudely jointed. There is no appearance of a fault bringing the two rocks into their present relative position; nor, considering the perfect continuity between their respective beddings (which, it is to be remarked, have a uniform dip), can it be said that the hemi- threnc is in detached masses that have been let into a synclinal hollov/ and by this means preserved in their present position. The bedding of the hemithrenc is in other parts of the quarry somewhat obscure ; and so is the limestone, especially where the interposed concretions are present. Delesse, M'ho had favourable opportunities for examining the geology of the Vosges, where the hemithrene occurs, states that the " caleaire saccharoidc est toujours comple'temeut enveloppe par le gneiss dans lequel il forme des flambeaux irreguliers ou lenticulaires tels que ceux qui out ete signales dans la Scandinavie IIEiMlTHUENUS AND OTHER CALCITIC KUCKS. 53 :hic and coat of These D ortho- k green ;c(l with raphite, mediate rtheless iguished ges into he least plagio- thc cal- miea of coloured )ver it is ant con- Right in feet in as seen The !n, come d green) ging the 3ring the ich, it is le hemi- vnclinal sition. e quarry fherc the ning the ates that nveloppe aliers ou indinavie par MM. Schcorer et Keilhau"*. He also mentions that at Laveline " le calcairc passe insensiblement an gneiss encaissant.* The conclusion we have {'ornied respecting the origin of thosu tongue-shaped masses of heniithrene will he obvious to the reader. Undoubtedly there is a decided ditl'ereiuH! between them and the enclosing gneis." ; it cannot, however, have been caused by any mechanical break. Nor <'an tlu; hemitluvn(> Im; infolded masses due to a crumpling of the beds ; for the gneiss is plainly seen passing into the hemithrene both vertically and horizontally, the change of colour (dark in the forni(!r aiul light in the latter) altording the clearest evidence of the transition, while the bedding is perfectly even and only slightly disturbed. Even hand specimens may be collected with the two rocks in such union as to make it impossible to detect any thing like a mechanical division between them. With these evidences before us, and taking into consideration various others that have been adduced, including those revealed by the Cleggan dyke, proving rock-forming siliceous minerals to have had their calcium silicate changed into a carbonate, the conclusion becomes inevitable that the hemithrene of St. Philippe is a raethylosed product after gneiss. M. Rozel held the opinion that the heniithrene masses of the Vosges are veins of igneous origin f — thus agreeing with ]!]mmons (1842), Mather and Von Leonhard (1833), with respect to corresponding cases made known by each as occurring in other regions. Delesse, on the contrary, conceives that the Vosgesian masses are genetically contemporaneous with the associated gneiss. Our view is that they are due to heated Avater holding carbonic acid or carbonate of lime in solution, which has penetrated the gneiss through joints and other open- ings, and converted it, where so aft'ected, into dyke-like masses of calcareous marble J. Having shown the convertibility of mineral silicates into calcite and calcitie rocks, the question that next turns up for consideration is whether a similar change has taken place over a large area. * Anuales des Mines, 4'" S(5r. vol. xx. p. 181. t Bull. Soc. G^ol. de Fiance, vol. iii. pp. 215-235. j: It is said that the rock at Chippal resembles in its purity Pares marble. I was unfortunately prevented reaching this locality during my visit to the Vosges.— W. K. mmmm '.TJ. I.J^A^JB 54 ROCK-METAMORPHISM. , It will not be denied, except ])erhaps by a few, that earthy sedimentary roeks have been mineralized over extensive regions into ordinary nictamorphics ; there is therefore no reason why ehcmical ehanj^cs or mcthylosis may not have been cfteeted on ii rcf^ional scale. Bischol", according to the extract previously ([uoted from his '(Jhcmical and Physical (ieology,' was evidently not averse to this view; nor v,'ould Ilcddle, we strongly suspect, be opposed to it. Speaking of the euphotide at Portsoy, and the occurrence there of a " vcit siliceous limestone in immediate contact with it," Heddlc proceeds — " Now the frequent association of thin beds of limestone with serpentine supplies very direct evidence of the conversion of hornblcndic and augite rocks into serpen- tine. In that fact we have a ready answer to the question, ' What becomes of the carbonate of lime necessarily formed during such an alterative process as the above?' I will not say that limestone is always to be found in such association ; Ave do not always find limestones even where we have indubitable evidence that they once existed ; for here the very thing that makes can unmake or sweep away. The carbonate of lime thus fashioned out of the rock forms a belt ])eneath the residual serpentine, thicker or thinner in accordance with the original thickness of the stratum of transformed rock ; also thicker or thinner according to whether that rock was augitic or horn- blcndic ; for the former can supply considerably more lime than the latter. This calcareous belt must lie beneath the parent rock, scaled against any great amount of further change, unless or until upheaval or denudation expose it to meteoric influences. Then water, flowing eitlier downwards or upwards, may — nay, in time must — sweep it away in solution, leaving lime-sink or collapsed void to evidence its former existence. But if the limestones, so frequently associated with serpentines, are thus to be assigned to the decomposition of the rock which yielded these serpentines, we have a crucial test of the soundness of the theory of the change, in the inquiry as to whether unchanged gabbro, or other such rocks, occur in contact with lime. That it never does, I will not say : but, in glancing at a skpt^-h geo- logical map which I have constructed of the district where these rocks occur, I find, as regards the great belt of diorite and diallagic rock which sweeps up Central Scotland, that where \W IIEMITHKENE'S AND OTHER CALCITIC llOCKS. 55 earthy ^\\ why ctcd on viously idcntly inspect , urreuce ict with of thin vidence serpen- ucstion, formed kvill not ion; we ubitable ng that of lime residual original icker or ir liorn- tne than parent unless luences. y— nay, sink or ; if the ire thus yielded 3s of the changed That t"li ueo- jre these rite and it where cither the limestone appears in contact witli it, or a "wash-ont discloses its former existence, there the rock is serpentine ; wliiM'e it appears as unaltered rock there is no litnc. " r find, moreover, that wherever the associntion can he observed, the lime invariably is beneath the serpentine. So it is with the loch of Clitf lime and the serpentine of Unst, both of the lime and serpentine beds at Pohnally, both of the lime and serpentine beds at Portsoy, at Limehilloek, Tombreck, tiie (Jreen Mill of Strathdon, and IJeanty Hill; and in enumerating these 1 have named all the most important masses in the country""^'. We liavc only one objection to Professor Hcddle's \'w\v. \t would seen) that he considers the calcareous matter, resulting from the changes he advocates, to be transferred to beneath the rock from which it was abstracted. Hut a difliculty strikes ns as to what was in the place of the new "calcareous belt^^ before it was formed. This point seems to have been overlooked. We are quite ready to admit the important bearings of tne fact stated bv Ileddle, that the lime '' invariably is beneath the ser- pentine;" we cannot but suspect, however, that the lime has taken the place of a mass of transmuted serpentine or malacolite. The notable shotted structure which frequently characterizes hemithrenes, and in many instances ophites, has an important bearing on the present question, inasmuch as this structure is due to the presence of crystalloids or portions of different minerals possessing a peculiar exterior. As far as y\c have been able to ascertain, MaecuUoch appears to h.ave been the first to bring the matter before the notice of geologists f. According to his description of the Tiree marbles (one mass of which is " an irregular rock — a nodule of limestone, improperly called a bed, lying among the gneiss without stratification or continuity ") , they consist of amor- phous or finely granular caleite in pink, white, and other colours, in which are imbedded (;rystalloids of sahlite, augite, and hornblende, termed in a general way coccolitc, separately dispersed, or aggregated — in the latter state attaining the size of an orange or larger. Other minerals are present, as mica, ser- pentine, steatite, sphene, &c. The crystalloids are often either * Oj). cit, pp. 540, 541. Biscliof mentions the occurrence of beds com- posed of limestone beneath others formed of mineral silicates. See ' PJiysical and Chemical Geology,' vol. iii. pp. 304, 305, 307, 308. t Western Islands of Scotland, vol. i. pp. 48h50(1819j. .-;;l m^miminsmsmmm I i] .'I i 5G ROCK-METAMORPHISM. partially rouuded or entirely sliapelcss — a peculiarity which Mae- culloch conceived to have resulted "from an incipient solution." Nauinann next drew attention to the rounded form of the eryntalloids oi' augite and other minerals in ealcitic rocks, par- ticularly in that at Pargas, in Finland, and attributed it to partial fusion. Emmons, in 181-2, referred to the rounded outlines of crystals of certain minerals imbedded in the crystalline limestones of Rossi 0, New York, and suggested that they were due to a partial fusion *. In 1863 Sterry Hunt briefly nv>tieed the occurrence of rounded grains of various minerals in the Archaean rocks of Canada f- Our attention liaving been drawn to the so-called ''chamber- casts of Eozoon '' in 1860, we identified them with the crystal- loids in the hcmithrenes of Pargas, Tiree, and New Jersey, also with the lobulated grains of serpentine conimon in the ophite of (yonncmara. It was likewise suggested by us that they had been shaped by chemical reactions aided by heated water, which, having aft'ected them superficially, had removed their substance and repiaced it by the calcite in which they are now imbedded J. About the same time as ourselves Giimbel noticed similar rocks, also the peculiar form oi the crystalloids contained therein, but he adopted the view, then pretty gen'rally received, that the latter were of organic origin s^. In his report, addressed to Sir William E. Logan, and pub- lished in 1866, Sterry Hunt, again referring to the subject ||, drew attention to the fact that crystalloids with rounded forms, besides occurring in the bedded hcmithrenes of Canada, are also present in "calcareous veins ^' (some being 150 feet thick) intersecting the latter and the associated gneisses, dolerites, &c. As this fact will have to be noticed again, its further c;onsideration may for the present be deferred. * Geology of the First District of New York, pp. 37-.*]9. Delesst, we are aware, has noticed rounds d crystals ; but, unfortunately, our extract, stating the fact, from one of his memoirs has got mislaid. t Report, Geological Survey of Canada, 18(53, p. 592. X Quart. Jouru. Qeol. Soc. vol. xxii. pp. 108, 199, 209 (Jan. 1800). § Sitzungsberichte d. Miinchener Akad. d. Wissensch. (Jan. 180G). II We find no reference to the rounded crystalloids in S. Hunt's memoir " On the Mineralogy of certain Organic Remains from the Laurentian Rocks of Canada," published in the Quart. Jouru, Geol, Soc. vol. xxi. (Nov. 1804). HEMITHRENES AND OTHER CALCITIC KOCKS. 57 In our paper of 1868 we also noticed the occurrence of crys- talloids of raalacolite in ophite from Connemara, which are not only more or less externally eroded and separated by calcite, but have gaping or chink-like cleavage-partings filled with the same substance. The mineralogist, it Avas asserted, knows full well that originally the cleavage-partings had individually their two planes in perfect contact ; hence there is no other explana- tion open to him than the one which admits that some solution, charged with carbonic acid or a carbonate, has gained access into the cleavage-partings of the malacolite, and, necessarily reacting on some of its constituents (? calcium silicate), has generated the infilling of calcite. Reverting to our account of the diiferent minerals in the l^iree marble, it was stated that we had found in this rock •'crystalloids of hornblende, othci's of sahlite, a few of quartz, and some apparently of serpentine ; while an occasional one appears half composed of hornblende and the other half of sahlifce ''*. Pretty much the same result has been lately obtained by Heddle, who mentions portions of sahlite in which " an inci- pient as well as a perfected passage into serpentine is seen^'f. Since the year 1869 we have described the microscopic struc ture of hemithrenes from the Isle of Skye, New Jersey J, Akei', and Ceylon §. Zirkel, in 1870, noticed the '* roundish, sharply- defined, serpentine grains " in Scandinavian hemithrenes, and assumed them to be pseudomorphs. In our papers it was shown that they contain not only rounded crystalloids of raalacolite and white pargasite (or it may be wollastonite), singly and in aggre- gations, but the same thingn decrcted and fashioned into slender shapes, corresponding with the remarkable configurations already described as occurring in Canadian ophite. A specimen from New Jersey contains numerous configurations associated with spinel, a well-developed example being actually imbedded in the calcito occupying a fissure-like opening in a large octahedral crystal of this mineral II . Specimens of the Skye rock, where it is ophiticif, • Proc. Roy. Irish Academy, July 12, 1809. t Op. cit. ih Ar)9. t Proc. Roy. Irish Acftd. n.?. vol. i. (1871). § fSeological Magazine, vol. x. Jan. 1873. II Proc. Roy. Iri8h Acad. vol. x. p. 547 (Feb. 1870). ^1 This rock .seems for the most part to be a carrarite ; but the poiiions we have examined are in the state of ophite or hemithreue. "ii 'i 1 58 ROCK-METAMORPHISM. after oeing decalcified, showed separated grains or crystalloids of malacolite with a thin white crust enclosing their translucent suh- stance ; others were seen with a portion of the latter removed^ hut the crust remaining intact; while close hy were hollow spheroidal cases identical in composition with the crusts : hefore decalcification the eases were filled with caicite. A few examples of the cases occur entirely riddled, reminding one of the per- forated shell of a Polyeystine ^. In our remarks on these things it was contended, considering the crystalloids of malacolite show themselves in every stage of decretion, that in numerous instances they must have disappeared altogether ; also that it was equally to he inferred tliat the inter- stitial ealcite separating the grains, even that forming the asso- ciated layers, had replaced a corresponding amount of malacolite. From the various evidences just given, added to those pre- viously adduced, all demonstrating that both minerals and rocks essentially silicates have been converted into ealcite and cal- careous masses, we feel it impossible to form ariy other con- clusion, as regards the hemithrenes so far considered, than that they were originally silacid metamorphics, also that the asso- ciated marbles, " consisting of nearly pure carbonate of lime,^^ are examples in which the mineral silicates have been completely extracted by the s'-.me methylotic process. Professor Heddle, it may be said, takes a different view. Referring to the hemithrenes that have come under his own observation, such as occur in Tiree, Harris, Lewis, and some other localities in Scotland, and contending that the crystalloids they contain " are one and all pseudomorphs of preexisting crystals of augite, sparsely sprinkled throughout a great mass of lime, in an amount which is altogether quite trifling," he declares that " these trifling specks could never have been the origin of a lime stratum tens of feet in thickness " f. Whatever may have been the origin of the other hemithrenes referred to by Heddle, we certainly must contend, with respect to the Tiree marbles, that their rounded crystalloids are not only pseudomorphs but also the residue of M-hat was once an augitic rock, and that the portion which has been destroyed, or rather removed, has undergone replacement by calcareous * Proc. Roy. Irish Acad. n. s. vol. i. p. 138 (1871;. f Oj), cit. p. 642. HEMITHRENES AND OTHER CALCITIC ROCKS. 69 matter*. Agreeing Avith Heddlc tliat it ^as not the " sparsely sprinkkHr'psendomorphosiul rrystals'Svliieh liavo been the origin of the lime stratum," wa iiovcrtheless ask wliy may not augitic rock-masses, by metliylosis and decrction into the " trifling specks," have given rise to it? Considering also that the marbles of Harris and Lewis are .Archaean, like those of Tircc, we have no hesitation in placing them in the same category. Professor James D, Dana, as it seems to us, advocates the methylotic origin of heinithrenes ; but lie takes a dift'erent view from ours as to the modus operandi of the process. In his description of rocks of the kind common in Westchester County, New York, he argues that they have been originally limestones or dolomites, which, through the action of hot silicic solutions, have become silicated, their mineral carbonates (calcareous and magnesian) being thus converted into mala- colite, treraolite, and other mineral silicates f. We have no objections to wv^Q against changes of this kind having occa- sionally taken place. But in the rocks to which we refer the evidences are so palpable and prevalent of the calcite having replaced malacolite, that we feci assured, if Prof. Dana were to decalcify specimens of the Westchester rocks, he would at once see the force of our view in its application to his par- ticular instances. Another objection lies against the idea that hemithrenes are silicated limestones, inasmuch ra, if applied to the Archsean deposits of the kind, it would make the latter to have been even more calcitic than they are at present ; and this would increase the difficulty in solving the problem (to be dis- cussed in a subsequent Chapter) as to the source which supplied the calcite. * The Tiree marble evidently contains much more augitic residue than is represented by the crystalloids, as there are frequently imbedded in it siliceous bodies of vai'ious sizes : the crystalloids are also often surrounded by a white, spongy, siliceous covering (oorresponding to flocculite), to be seen after decalcification. Macculioch has noticed something of the kind (op, a't. vol. i. p. 5.3). t American .Tournal of Science, ."rd sor. vol. xx. p. 28, &c. The origin of these rocks will be further noticed in Chapter XIII. 60 ROCK-METAMORFHISM . CHAPTEE XL ON THE ORIGIN OF THE MINERALS CHARACTERISTIC OF OPHITES AND RELATED ROCKS, THE MINERAL PERI- DOTE IN PARTICULAR. )^il \",i The object of this Chapter is to show that the minerals referred to ill the heading arc the iMrcct products of hydrothernial reactions in methylosed and volcanic rocks, also of pseudomor- phism in minerals characteristic of ordinary metamorphics and different kinds of igneous masses. If this object can be accom- plished, it will necessarily follow that all the minerals under notice are, in a certain sense, secondary products. Several of these minerals, such as calcitc and the different serpentines, arc generally admitted to have had this origin ; there are others, however, which, as far as we can ascertain, have never been considered any thing else than original in the same sense as the quartz, feldspar, and hornblende of granites are held to be so. At first sight the occurrence of secondary minerals in volcanic rocks seems improbable. Still it is pretty generally considered that many of the minerals found in dolerites, trachytes, and ordinary lavas have been generated under circumstances, as to time and conditions, totally different from those under which the rocks in question were formed. Even granite, generally assumed to consist of original minerals, occasionally contains zeolites, which all must admit to be secondary products. The same must be asserted of caleite and serpentine, already notified as present in the dioritc and other rocks near Galway and in Jersey. It is necessary to mention, in the next place, that numerous instances must occur of a rock that has undergone partial me- thylosis, having some of the minerals it contained in its previous or primary condition (whether such rock be igneous or ordi- nary metamorphie) retaining their original character, and others partially altered. Thus the hemithrene of St. Philippe carries hornblende and muscovite ; but as these minerals lie immediately adjacent to the contact rock, viz. gneiss, there can be no doubt that they have escaped the changes which converted the same species accompanying them into malacolite and phlogopite. ORIGIN OF MINERALS CHARACTERISTIC OP OPHITES ETC. 61 I « It has been clearly shown that, besides other minerals, mala- colite and serpentine — demonstratively secondary products — have themselves undergone chemical changes which, gradually removing certain of their constituents, especially the silacid, have terminated in calcitic or miemitic (dolomitic) replacements. With respect to several otlicr minerals characteristic of ophites and hemithrencs, such as spinel, idocrase, apatite, sphene, &c., it may be assumed that, although original in these cases (that is, formed independently of any other mineral), they arc neverthe- less of secondary origin, having resulted from the intervention of hydrothermal reactions. Another mineral of importance in the subject ujider conside- ration is peridote. also known under the name of olivine*. It runs into several varieties, as limbilite, chrysolite, glinkite, bol- tonite, olivinoid, hyalosiderite, &c. Analyses make it to consist of magnesia from 32 to 50 per cent., protoxide of iron from 6 to 30 per cent., and silica from 31 to 44 per cent. Accessory ingredi.^nts, as alumina, oxide of nickel, oxide of manganese, titanic acid f, and silicate of lime, are not unfrequently present. The magnesia is often about 13 per cent., generally 10 per cent., and occasionally 2 or 3 per cent, in excess of the silica. Silicate of lime is present in specimens of peridote from the lava of Togo (Cape-Verd Isles) to the extent of nearly 6 per cent. Monti- cellite is a highly calciferous peridote, containing 34 per cent, of calcium silicate. The minerals nearest to peridote are humite (which contains, in addition to the Cjsentials of peridote, between 2 and 3 per cent, or more of fluorine) and chondrodite, in which the fluorine is increased in some cases to more than 7 per ceit. Leipervillite (bronzite according to Pisani) only differs from peridote in its magnesia reaching to 75 per cent. Forsterite, another related species, but containing only a few per cent, of protoxide of iron, carries us on to diaclasite, enstatite, and certain reputed diallages and hyperstheues : in these last the silica is in excess of the * D'Argenville's name peridoie (date 175.5) has piiority over that of Werner's olivine (1790) ; obviously, then, French mineralogists are right in adopting it. Pliny's name, chrysolite, it would appear, was not applied to the mineral now so called by mineralogists (see Dana's ' Mineralogy,' under " Olivine "). t A titaniferous peridote from Zermatt, according to M. A. Damour, contains 5-30 p'>?r cent, of titanic acid (Bull, de la Soc. Mineralogique, t. ii. pp. lo, 10). 63 HOCK-METAMoUPlI ISM. magnesia. Fayalitc is usually classed with peridote, though containing only a small quantity oi magnesia. terpentine is another chemically related mineral, with the dif- ference principally in l)eiiig hydrous. It frequently contains iron protoxide, by which its relation to peridote is further sustained. The frequent change of peridote into serpentine, which we liave already noticed, has no doubt largely contributed to the prevailing idea that the former mineral is always an original product. Taking this view, some difficidty would be felt by conceiving that peridote itself could occur as a product of pseu- domorphism. Hence it is, in the case of a rock containing peridote associated Avith augite or hornblende, that the idea of the first having been pseudomorphically generated out of either of the latter two docs not seem to have been entertained. Rocks containing peridote have been called pcridolytes, the principal of which are Iherzolyte, dunyte, and picryte. Peridote is of somewhat common occurrence in many dole- rites, trachytes, and lavas. Its presence is well known in what may be an igneous rock, — the hypersthenyte near Elfdalen in Sweden*; and it is said to occur in the granite or syenite between the Nile and the Red Sea. Delcsse discovered a ferru- ginous variety of peridote in cavities of the pegmatite or granite of the Mourne Mountains f. The related species, fayalitc, has been found in ordinary metamorpliies (those simply mineralized) at Tunabcrg in Sweden, forming, with augite &c., a bed, called eulysyte, in gneiss. A true peridote dominates in a rock, called olivenyte, associated Avith talc-s:'hist, at Uddevalla, Sweden ; a variety has been observed near Kyschtimsk, north of Miask, and near Synersk in the Ural in talcose rock : these cases show that the mineral is also present in met!./losed metamor.. phics ; Avhile its frequent occurrence in serpentine, made known by Breithaupt, Bischof, Hunt, Otto Hahn, and others, leads to the same conclusion. As it is found in methylosed rocks, the presence of peridote in veins of cnlcitc, presumably of secondary origin, traversing large l)locks of talcose schist scattered over the southern moraine of the Findelen glacier near Zermatt, is not surprising to us, though it must be to those who subscribe * Tliis rock is said to cousist of hyperstliene, labradorite, and peridott!. 1" lleforerce to the fact is unkiiowu to us ; but the occiureuce of peri- dote in the lourne granite id mentioned by Dr. Hauglilon in Quart. Jouru. Geol. Soc. vol. xii. p. 191. ORIGIN OF MINERALS CliARACTERlSTlC OF OPHITES ETC. to the prevailing idea just stated. But it ought to be greatly embarrassing to the latter to find that it notably occurs (rts bol- tonite) in the hemithrenc ol' Massachusetts, also as " roundish sharply defined grains/' more or less changed into serpentine, crowding the corresponding rock ("granular limestone'^) at Snarum, Aker, and Modum in Norway*. To add to its remarkable indifference as to the nature of the material selected by peridote for its matrix, the fact may be mentioned that this mineral, or some of its varieties, besides being often in association with other substances, exists imbedded in the nickeliferous iron of meteoric amygdaloids that have fallen ill Siberia, Atacama, and elsewheref; and it is a common ingre- dient in meteoric stones. We have shown that peridote is a variable mineral through the increase or decrease of the percentage of its magnesia and iron, also through the presence of accessory substances. Thus, let it be conceived, in the case of a rock like ophite, which has often resulted from hornblende and augite, that during the process of alteration the protoxide of iron belonging to either of these minerals were not removed, there seems to be no valid reason against the probability that this substance would become united, all things being favourable, with any available free sili- cate of magnesia, and thus form peridote or some variety of it. The two minerals peridote and serpentine can be readily dilt'crentiated by the polariscope when they are associated as in ophite. Guided by the peridote in the hyperstheny tc of Elfdalen (which is optically in agreement with the same mineral from Expailly, in Auvergne, and several other localities), and allowing for variations due to circumstances such as have been mentioned, it may be stated that this mineral exhibits a display of the richest colours by rotating the prisms, viz. yellowish green, sap- green, pink -rose, ruby, blue, &c. — being a greater variety and of more brilliancy than those displayed by chrysotile. On the contrary, serpentine only shows pale yellow (under parallel prisms), changing into dark grey (when the prisms are crossed), and back again into pale yellow. The specimens of peridote which Me are about to notice exhibit * Neues Jabibuch fiir Mineralogie, 1870, p. hi>8. t As meteoric peridote is generally believed to be of extramuudaiie origin, .probably solar, obviously any endea\our to explain its ori{.an maybe properly avoided. mp Hill iiiiiiiiia r 1 1 ' ■ i ! rtt HOCK-MKTVMOHPIIIsXf. the hcimlilnl {jroon, ruhy, ami ollirr colnnis tlml rMppoiiillv (listinjyuish it. HntluM" often iiuiy he Holcctrd 1m- polnri/.rd lijrlit sopln ninl strini^s oftliis iniiirral loosdy and conrMHcdly inlrrivti- (Milatod witli sorpontinc. lii (i{?. I, I'l. Ml., wo liavt* rrprcHCMiod a short pliito (" oliambcv-oast " of" Mozoon ") <'onsislinfr of Ror- ponlinc at one cud and pcridoto \\'\{\\ a stroiifj; ol)li(|U(' olrava^c? at tli(M>thov. Fig. 5, IM. III., oxliibits jioridotc forming a portion of another " chambiM'-east " and intcM'scctcd by hjyern of calriic. 'rh(Mnttt in the two latter it wouM seem that the peridotc is psendomor])hie t\\'U'r some mineral, partly retaining its erystalline form. The intersecting layers of ealeito ii\ the specimen nnder ligiire 5 may be accepted as strong ])resnmptive evidence of chemical changes involving the |)sendo- morphie development of this carbonate. The opinion is prcttx general that peridot«» is in all cases an igncons ]n'odnct. A tlitVcrent vi(nv n>ay b; entertained by Sterry Hunt, Mho, considering the doctrine ot chen\ical precipitation which he advocates with respect to the origin of the Archji;aii hemithreues, cmght to regard peridotc, at least that form of it which is known to occur in these rocks, as liaving been formed in the humid or wet way ; for it has come under his notice both in their bedded and " vein "-masses*. It has seemingly never struck any one that the fre(pient intermixture of peridotc and serpentine (the latter in bedded aud dyke-shaped masses) is strong evidence at least of its being due to chemical alteration. Breithau|)t, who had knowledge of masses of serpentine coutainiug peridotc, was evidently intlu- euccd by the }>revailing idea, already noticed, iu making the suggestiou that they are altered examples of the latter mineral — that is, of a rock related to what is now called a pcridolytc. Hut as to a rock of this kind being a methylosed dolcritc, dioritc, or any thing else, the idea to Brcithaupt w as apparently, as it is to several others of the piwsent day, entirely out of the question. The occurrence of peridotc in tale-schists seems to have perplexed Bischof; for he, too, advocated its igneous origin: but being a thorough hydrothermalist as regards the agencies which developed rock -metamorph ism, he was compelled to admit that the case " would seem to indicate that this mineral has * Chtmical and Geological Esstxys, pp. 31 and ilO. onifMN nr minrhalh cifAnAfTKiUNTrf (iv »)l'iirri';«i ktc. Ofi hpcii I'oi'incd ill tin- wet way"*. IliHclujI', we lire RtroiiKly inclined to iliiiik, vvonid liiivi; felt no lirMitiitioii in (tikin^ iliiH view Iitid ho been iu'<|uaint('d willi iicridotilc rons ophites that were HediinentH oiif^inally. Sii|»|)oited hy niiineronH evideneeH whieh have ef)nio to lif^ht of hite years through the Htndy ol' ophites, we must deehire ourselves on th(^ side of the- opinion that the presenee of peridote ill all Niieli I'oekn is asiinieh tin; result of hydrotheiiiial and ehe- luieal changes as is tlu^ serpentine with whieh it may hi; associated. Mesides, it is well known that lava contains water and steam for years after its eruption : jets of va|)our are still given off from the lava of Jurolla, now nearly niin^ty years after its ejection. The occurrence of peridote in granites, though countenancing the id( a of this mineral having hecn formed hy igneous a(!tion and in the dry way, cannot Ix; accepted as proving any thing of the kind ; for it is now well known that these! rocks occasionally contain Kcolites, serpentine, chlorite, and other hydrous minerals, which must have been formed in the w(!t way. Hence hydro- thermal conditions, recpured by our theory for the production of secondary minerals, have not always Ixum absent in granites. Not long since we pointed out instances of peridote in the amorphous or colloidal form, where it is interreticulated with serpentine. It may also be mentioned that the former mineral oecursin the crystalloid and crystalline conditions, as at Snarum. Bea\itiful crystals have been found in tlie lavas of Vesuvius, in forms proper to itself, and not pseudomorphic after those belonging to another mineral : this may be regarded as proving thai, peridote is not of secondary origin. Any argnment of the kind, however, is invalidated by the fact that other minerals arc in the same predicament. Epidote, calcite, and tale occur crystalline, each as a secondary product and in forms proper to itself, also as pseudomorphic after garnet &c. Again, the occurrence of crystals and crystalloids of peridote in true igneous dykes and beds of lava is lield by some to prove that this mineral and the ejections containing it arc of contem- poraneous origin. But a formidable ditHculty meets this view at the outset. As generally considered, ])crid()te is one of the most refractory bodies known j and in agreement with this fact is the well- attested statement that peridote frequently occurs under circumstances showing that the heat of its matrix, when * Olieinical ami Thysical Geology, vol. ii. p. JJoc*. 66 ROCK-METAMORFIIISM. iu a molten condition^ was insufficient to fuse it. The opinion is therefore pretty general that the periclotc in these eases has been thrown out of volcanoes in a solid condition (crystalline and amorphous) , imbedded in the lava ; in other terms, as ex- pressed by Bisehof, " all these facts are indications of its exist- ence in ;i solid state in the melted lava, and arc quite inconsis- tent with the opinion that it has originated from the lava/' Moreover " the occurrence of peridotc in a metamorphic ruck renders it intelligible that lava penetrating through beds in such rocks might carry up with it lumps or crystals of this mineral " *. But we cannot admit that its presence in lava is to be explained in this way. The fact that it occurs abundantly in the old lavas of Vesuvius and rarely in those of historical eruptions may be held as supporting a contrary interpretation, in cases of this kind at least; for, admitting that this mineral has been derived from previously existing rock-ma««''s lying at great depths, there is no reason against the subterranean sources yielding it at the present day. Before closing this portion of our present argument we shall cite a passage from Bisehof giving his view as to the origin of other minerals (augite, hornblende, leueite, &c.) common in dolerites and lavas, though it may not be unnecessary to remind the reader beforehand that, in agreement with passages already cited, our author must have inconsistently excluded peridotc. ^Mt is evident that, after the solidification and cooling of lava, crystals can no longer be formed by fusion. Therefore, when we find that the older lava contains (crystals whicli either do not occur at all in the more recent lava, or which are at least much larger and better developed than in tlie latter, it is certain that these crystals have been formed in some other way than by fusion, and there is no otlicr way than the wet way in which they can have been formed : . . . . there is no reason why this mode of for- mation should be considered impossible ir the older lava, which has for long periods been exposed to the j'-tion of water." .... ''We must therefore refrain from regarding crystalline minerals which occur in volcanic masses as products of fusion " f. Tn view of the various points thus far brought forward, it seems most unreasonable to exclude peridotc from the list of products of alteration. Therefore, until better evidences than have hitherto * Chemical and Physical Geology, vol. ii. p. 358. t Ibid. vol. ii. pp. 94, 95. ^:. ORIGIN OF MINERALS CHARACTERISTIC OF OPHITES ETC. 07 been adduced to the contrary arc forthcomirifi;, we shall continue to maintain that peridotCj whatever kind of rock may be its matrix, or whether occurring in crystalline forms peculiar to itself or as amorphous masses, is as much a secondary product as other secondary minerals which may be its accompaniments. Weighing the evidences and considerations hitherto adduced, it may be taken as clear that, although genetically a secondary mineral, peridotc is of independent origin in the crystalline and crystalloidal examples last under notice. Our ne\t object is to show that pcridote, or a mineral sub- stance assumed to be the same, has originated through pseudo- morphism after other minerals, and that therefore in cases of this kind it cannot be of independent origin. That peridotc occurs frequently changed into other minerals, as serpentine, is p well-established fact; but the proposition just laid down does not seem to have been entertained by mineralogists : it is one, however, which cannot be said to be gratuitous ; for other minerals are known to be similarly poly- genetic. As hexagonal crystals, quartz is in a form proper to itself and of independent origin ; but as the same mineral sub- stance is found in forms peculiar to calcite, such forms are pseudomorphs, and cannot have originated independently. Our illustration has its parallel in pcridote. Again, as we purpose to show that peridotc is pseudomor- phous after hornblende and augitc, we may be allowed before- hand to ask the question — As serpentine frequently occurs pseudomorphosed after hornblende and augitc, why cannot th^i latter species be pseudomorphosed into peridotc, Avhich is so closely related to serpentine ? We shall endeavour to answer the question in the affirmative by the consideration of evi- dences pertaining to the crystalline form, cleavage, and polarization respectively characteristic of the three minerals concerned. Peridotc belongs to the trimetric crystalline system ; and it necessarily has for its primary a right rectangular prism, Avhich in this particular mineral rarely occurs otherwise than under somewhat complex prismatic and basal moditications. Its simplest prismatic modifications, by removal of the lateral edges to the complete effaeement of all the primary faces, would be rhombic, with acute and obtuse angles respectively ■■MWWWii— > mmmmm «.JL^.«. I f B 68 ROCK-METAMORPIIISM. 86° and 91.°; but it seldom, if ever, occurs iii this form. In the annexed woodcut, fig. 1, the outside dotted lines represent a cross section of the primary rectangular prism of pcridote ; the thick continuous lines within represent the secondary rhombic modification ; the broken lines represent the cleavage. Usually the prism has eight, ten, or twelve lateral faces; a cross section, being thus many-sided, has a somewhat rounded or ratlier ellip- tical outline. Cross sections of pcridote arc figured in Zirkers Avork with six sides ■**". The cleavage of pcridote consists of three dissimilar sets, two being parallel with the prismatic faces of the rectangular pri- mary, and one conformable with the ba^al faces; consequently their mutual intersections are at right angles to one another (sec inner broken lines in fig. l),asmjybe observed in the cleavage-solids which occasionallv occur in masses of this mineral common at Unkcl and elsewhere. 'lurning to augitc and hornblende, both belong to the mono- clinic crystalline system ; their respective crystals, which often occur as six- or eight-sided prisms, are usually less modified than those of pcridote; and moreover, on account of their inclination, tlicv arc further differentiated from crystals of the last mineral. The simplest modification of the primary of hornblende, when it obliterates, as stated of pcridote, all the original faces, gives rise to an oblique rhombic prism, whose acute and obtuse angles are respectively 55° 30' and 124<° 30' (see fig. 3) . The corresponding modification of augite yields angles 87° 5' and 93° 55', as in fig. 2. It Avill thus be seen that the cross section of a rhombic priom of augite dift'ers extremely little in its angular measurements from a similar section of })eridotc', and that both arc n?arly a square. The decidedly rhombic form of the cross section of hornblende need not be mentioned in this comparison. The basal modifications in each of these three minerals render it difficult to determine Ihc form of their respective longitudinal sections, depending, a, t\e question does, as to whether such section be a true one or not, on its parallelism with the vertical crystalline axis. * J)io mikroskopische Berscliaftenlieit der Mineralien uiid Gesteine, pp. 09, 21(5. None of Zirkel's figures represents a true cross section of peridote, as they nre too rhombic ; they muat be somewhat obliciue to the vertical axis instead of at a right angle. il Sock-ifitamorpkiMm,] [To face \>. (kS. n. Ill cscnt a X ; the liombic Jsually jectioiij sr ellip- ifiirkel's 2ts, two Fig. 1. Fig. 2. Fig. 3. 2 mono- 2\l often nodified jf their s of the nary of all the whose 24,°30' yields leen that tremely ;ion of ccidedly not be s render itudinal ler sueh vertical ae, pp. 90, iridote, as rtical axis Fig. 1. Diagrammatic transverse sections of a prismatic crystal of peridote. Obtuse angles 04" ; acute angles 80°. The outer dotted lines represent the form of its primary ; the inner continuous lines angular measurements of its simplest modiiication j the broken lines its rectangular cleavage. The prism is upright. Fig. 2. Diagrammatic transverse sections of a prismatic crystal of augito. Obtuse angles 92° 55' ; acute angles 87° 5'. Fig. 3. Diagrammatic transverse sections of a prismatic crystal of hornblende. Obtuse angles 124° 30'; acute angles 55° 30'. The augite and hornblende prisms (Figs. 2 & 3) are inclined (mono- clinic). Their inclination to be assumed as from bottom to top of the page. When their angles are truncated down to the white lines, the resulting section is that of the usual prism. The outer dotted lines represent the form of the primary ; the con- tinuous lines a secondary form, or that of the cleavage-solid; the broken lines the cleavage, which is rhombic. -'"'^"''-'^SWiM f ! i i ■mmms<^mmm^B:^sims ORIGIN OF MINERALS CHARACTERISTIC OF OPHITES ETC. 69 The cleavage of hornblende and augite is prismatic and basal : the two prismatic sets are parallel with the faces of the secondary rhombic prism ; while the basal set, which is parallel with the basal faces of the inclined primaries, necessarily intersects the prismatic cleavage-planes obliquely *. Obviously, whatever difficulty attaches to crystalline form, cleavage is of great assistance in enabling the investigator to distinguish peridote from either augite or hornblende ; for while there are only right-angled sets of cleavage in the first, there are nothing but oblique sets in the two last. Still there are difficulties to be encountered in connexion with this point, depending on whether or not the section which may be under examinatioii is in its correct, or approximately correct, position of intersection relatively io the vertical axis of the prism : but their consideration may be advantageously passed over as in- volving niceties of calculation unnecessary in this work; and we feel ourselves bound to argue out mir conclusions suitably for geological students in gencial. Let us next examine the sections of crystals of " peridote,^' as represented by two of our fellow labourers, to see how far they are in conformity with the cleavage-characters of this mineral. Unfortunately the figures of " peridote " given by Allport " t> although representing each a cross section, do not exhibit any cleavage. Professor Hull's figures are not in this predica- ment |. Allport, who has carefully examined a number of British dolerites, has represented in his figures 25 and 27 cross sections of what he takes to be peridote ; but, from their form, it may be equally assumed that they represent augite. lie has also given another secaon, four-sided, in fig. 26 ; but exception may be taken to it as being too simple in form for peridote, and having its angles approaching too closely to those .characteristic of the acute rhombic modification peculiar to hornl)lendc in its simplest secondary form, and as equally represented by its clea- • The basal cleavage of these minerals, it will ho uiulersloocl, could not he represented in figures of cross sections. t Quart. Journ. Geol. Soc. vol. xxx. pi. 34. figs. 25-27. X Trans. Royal Irish Academy, vol. xxv. pi. xi. figs. 25-30, " Report on the Cliemical, Mineralogical, and jNIicroscopic Characters ot the Lavas of Vesuvius from 1631 to 1868," by the Rev. Trof. Ilaughton and Prof. Hull, I' I »i M :l 1 M ' 1 i 1 : i If 1 i hi i ■■ i i ■ i 70 ROCK-METAMORPHISM. vage-solid : compare Allport's figure wit]i our fig. 2. We there- fore cannot accept this casc^ any more than the others, as an example of peridote, unless in the condition of a pseudomorph. We have been obligingly favoured by Mr. John_, Young, of the Huntcrian Museum of Glasgow, with a number^of speci- mens of trap rocks from the Clyde district — the [same rocks which supplied Mr. Allport with several of his specimens. From the specimens which Mr. Young sent ua we have had prepared several microscopic sections ; but in none do we observe any thing opposing the above conclusion. Many of the crystals contained in them (showing peridotic colours) exhibit irregular rhoraboidal sections, which, we consider, prove that the longi- tudinal or vertical axis of the sections is inclined; moreover several of them exhibit prismatic rhombic cleavage. The mineral we must therefore consider to have been originally augite or hornblende *. In our present investigations we have been materially assisted by Professor Hull, who, though aware that we were disposed to take a view different from his, has kindly allowed us to exa- mine the sections represented in the " Report " with which his name is connected. In the figures to which allusion is "o^ made, attention has been paid not only to angular measurements, but to cleavage-peculiarities. We have not been able to form any satisfactory opinion on any of the sections referred to (being unsymmetrical forms), except the one under fig. 20 ; fortunately this is sufficiently decisive for our purpose. The section given in fig. 7, Plate I., is from a drawing made by ourselves, which, it will be seen, closely agrees with Dr. Hull's representation, 'except that the cleavage is shoMu a little more in detail. It is stated that this is a " section of olivine crystal from the lava of 1794." The mineral or chemical nature of the section Ave do not dispute ; for it exhibits under polarized light the colours characteristic of peridote, excepting that they are slightly * A crystal of aiigito described by Saiidberger has, disseminated through its entire mass, a substance which he considered to be peridote (Biachof, op. cit. vol. ii. p. 30r). We should like to draw Mr. Allport's attention to this case. Moreover the presence of cnlcite associated with serpentine in Mr. Allport's examples is a noteworthy evidence in fHVour of our view as to the origin of the "calcareous skeleton" and the caleitic interpolations in the "nummuline wall" of " JSozom Camdcnse,' ^ X ; there- ,, as an morph. ung, of ■ speci- D rocks From reparod rve any crystals rregular B longi- loreover mineral ngite or assisted disposed 3 to exa- i^hicli his 1 is "c. rcnients, (inion on forms), fficiently fig- 7, ;h, it will n, [except from the le section light the e slightly ed tbrougitt Bischof, op. tion to this tine in Mr. w as to the ious in the ORIGIN 01' MINERALS CHARACTERISTIC Ol' OPHITES ETC. 71 duller, and their variation is somewhat different ^. These differ- ences, however, are no more than what may he observed in most minerals assumed to be peridote. It may also be mentioned that, considering the approximate agreement between peridote and augite (woocut fig. 2) in their cross sections. Dr. Hull was justified in assuming the crystal to be peridote : for the same reason we see no impropriety in taking it to be augite ; but the sectional difference they exhibit is not to be overlooked. Still, although so much can be said in favour of the identifica- tion made by Hull, it is extremely doubtful to us that it is a correct one, inasmuch as the prismatic cleavage, so well displayed in the crystal under notice, instead of being right-angled in its intersections or parallel with the sides of a rectangular prism, as required for peridote, is rhombic, precisely like that of augite. We are therefore inclined to the conviction that this example was originally a crystal of augite, which has undergone a chemical change into a substance resembling that of peridote, or, as wc prefer to say, M'hich has become peridoti/cd. The presence of peridote in certain rocks may be satisfactorily explained in accordance with the views that have been advanced ; for, admitting that crystals of hornblende and augite can be pseudomorphosed into peridote, there is no reason why a crys- talline rock, whether xerothermal, methylosed, or volcanic, wliich contains these minerals, may not become more or less peridotized. It is in this light that we regard dunyte, picrytc, liierzolyte, ossipyte, olivcnytc, and others of their class, also many of the doleritic dykes described by AUport f, AVe arc therefore opposed to accepting the presence of peridote in any one of the above-named examples as evidence that a rock of the kind is in its original condition, but rather as proving that it is more or less a methylotic product. • A\'hen tho prisms are pniallel tlie colour is pale jellow, at 45- pale purple, at 00^ (cross prisms) deep jjurplo, at 135 pale pink, returning to pale 3'ellow: there i8 no brilliant 8np-green, nor ruby. The structure is granular. t The remarkable doleritic rock at Carmoney Hill, co. Antrim (the matrix of the new mineral, huUite, Ilardman), is so charged with peridote, as fir,st made known by Prof. Hull (Proc. Iloyal Irish Acad. 2nd ser. vol. iii. (SL,ionce), pp. 100, 107), that we ar-j disposed to consider it another ex- ample of tho kind. Ir 1 J I Mi 72 ROCK-METAMOKPHISM. CHAPTER XII. ON THE OKIGIN OF THE ARCH/EAN " CRYSTALLINE LIMESTONES " OF CANADA.. The Canadian Archseans are for the most part mineralized metamorphics, the methylosed members (usually silo-carbaeid) bern^ a subordinate group. In general highly crystalline, the former consist of bedded masses of granitoid gneisses, quartzites, diorites, dolcritcs, various crystalline schists, &c., and the latter of calci-hornblendic gneisses, ophites, '' crystalline limestones," and other related kinds. The "crystalline limestones" having been proved to be chemically, mineralogically, and structurally identical with lumithrenes, we shall assume them to be rocks of the latter kind. The " crystalline limestones " or hemithrenes, which are often interstratified with the mineralized metamorphics, vary much in their mineral composition : calcite, or miemite (either of which is usually present) generally serves as a matrix for tlic mineral silicates — chondrodite, augite, hornblende, phlogo- pite, orthoclase, labradorite, serpentine, quartz, idocrase, &c.; which, with apatite, graphite, and other non-silicates, occur as crystals, or as irregularly-shaped grains (crystalloids) varying much in size, "either alone or variously associated, and some, times in such quantities as to make up a large proportion of the rock, to the exclusion of carbonate of lime ;" so that beds are often seen to graduate completely into diorites, gneisses, and other silacid metamorphics^. The beds arc often greatly contorted ; and their component layers are frequently and independently crumpled in the most extraordinary manner. At the Ragged Chute on the Mada- waska (Canada) there is a bed, according to Logan, " three feet * Report of the Geological Survey of Canada for I8CG, p. 185; and Chemical and Geological Essays, p. 206, "CRYSTALLINt; LIMESTONES " OF CANADA. 73 thick, which consists of alternating layers of limestone and gneiss singularly corrugated, lying between masses of evenly laminated hornblendic gneiss"*. The latter, from its structure, may be regarded as due to sedimentation ; but the corrugation of the enclosed " layers of limestone and gneiss " is totally inconsistent with its being of similar origin. Obviously the phenomenon is an example of segregated lamination, whose corrugation is the effect of internal movements, in individual beds, produced by chemical forces. The latest estimate of the thickness of the entire group of Archfean rocks has been made by Pdr. Henry G. Vennor, who, from very careful and laborious observations carried on during a number of years, is entitled to the highest confidence, and '^ from whose views'' Mr. Alfred 11. C. Selwyn, Director of the Canadian Survey, says " he has no reason to dissent.'" " It would appear that the whole volume is not less than between 50,000 and 60,000 feet ; and this estimate does not include the great fundamental unstratified or obscurely stratified gneisso- syenitic series, but commences only with the first strata of clearly stratified gneiss." As to the great fundamental series, it is at present impossible to suggest even its approximate thick- ness ; but, forming the backbone of Eastern Ontario, as well as thousands of square miles in the region to the northward of the Ottawa river, it '' is apparently a distinct formation, though the separation between it and the first strata of the overlying stra- tified gneiss is not alwjiys clear "f- It is well Icnown that the late Sir William Logan designated the great metamorphic group under consideration by the name Laurentian, also adding thereto, with a distinctive title, another metamorphic group, on the whole mineralogically diflerent, which he regarded as an unconformably overlying one. But the inves- tigations of Vennor have thrown some doubt on the alleged unconformity ; the latter geologist is nevertheless disposed to * Geology of Canada, 18G3, p. 27. Dr. Bigsby, speaking of the bands of Canadian crystalline limestone, states " they are tortnous, and often, by bend- ing round, sharply return by a parallel course to within a short distance from their visible point of departure. Corrugated seams of gneiss are sometimes enclosed in the limestones" (Geological Magazine, vol. \ p. 150), t Keport of the Geological Siu'vey of Canada for lt*70 and 1877, pp, 280, 299, 300. TTf m .lid IL: li ii 74 KOCK-METAMORPHISM. adopt a twofold division, but to make the separation on a dif- ferent horizon to that adopted by Sir William. If we have not misunderstood the proposed subdivisions, the lowest one, which includes most of the Laurentian system of Logan, is essentially composed of silacid rocks, only a thin zone of crystalline limestone being included in it ; the next one embraces, in addition to the silacid members, a massive zone of hemithrenes (''crystalline limestones ^^), in which arc included stratified dolcrites, ophites, and other related rocks. Accord- ing to Vcnnor, who had favourable opportunities for taking measurements^ the zone has '' an average thickness of 5600 feet"*. Mr. Selwyn proposes to make a system for the last group of rocks, retaining for it Logan's name, Huronian f, but to add thereto some other groups (certain members being slightly altered). Respecting the correctness of this proposal there may be some disagreement among American geologists. It has been remarked by Sir William E. Logan that " even during the Laurentian period the same chemical and mecha- nical processes which have ever since been at work disintegrating and reconstructing the earth's crust were in operation as now. In the conglomerates of the Huronian series there are enclosed boulders derived from the Laurentian, which seem to show that the parent rock was altered to its present crystalline condition before the deposit of the newer formation, while interstratified with the Laurentian limestones there are beds of conglomerate, the pebbles of .,!iich are themselves rolled fragments of still older laminated sand- rock; and the formation of these beds leads us still further into the past" |. Cordially agreeing with these remarks, we are prevented ac- cepting Sterry Hunt's belief that in " pre-Cambrian times there prevailed chemical activities dependent upon greater subter- ranean temperature, different atmospheric conditions, and abun- dance of thermal water, and that under these circumstances * Ibid. p. 204. This is Mr. Veuuor's estimate for the " Ifastinga limestone zone." His estimate for what is considered to be a corresponding zone in Lanark township is not " less than from 6000 to 0000 feet thick " (Report, 1874-7.'3, p. 14.3). t Canadian Naturalist, vol. ix. p. ,30. :|: Quart. Journ. Geol. Soc. vol. xxi. pp. 40, 47, (< }) CRYSTALLINE LIMESTONES OF CANADA. 75 were deposited the materials of the great crystalline rocks '^■'*', — that is, as chemical precipitates. There arc no more reasons for ascribing the 60,000 feet of Laurcntian sands, argills, and other deposits (that is, in their original condition as sediments) to Dr. Hunt's " chemical acti- vities " than there are for attributing the 30,000 feet of similar deposits forming the Longraynds to the same agencies. At the Dublin meeting of the British Association, 1878, Dr. Sorby referred to the presence of certain crystalline substance^, in the "red clay'' and other deposits, which the ' Challenger' expedition brought up from the bottom of the Pacific and Atlantic Oceans, in such a way as to make it appear that he is not opposed to the notion that they are the products of chemical precipitation. The nature of these crystalline substances and the deposits enclosing them is engaging the attention of Renard and Mun'ay. The full result of their investigations has not yet been published ; but some of their conclusions are stated in the British-Association Report of the Sheffield Meeting in 1879, pp. 340, 341. There is nothing in their statements to coun- tenance the idea that any thing in or belonging to the red clay, or the deposit itself, is a chemical precipitate from ocean water, but on the contrary, that it is for the most part a volcanic ash, which through decomposition or disintegration has become con- verted into red clay. The crystalline substances it contains, viz. plagioclase, augitc, peridote, sanidine, magnetite, zeolites, sideromelane, &c., arc more probably non-disintegrated portions of mineral aggregations contained in the 'olcanic ash, than the result of chemical reactions. Prof. A. Geikie (seemingly referring to some of the above), in stating that " these silicates (there may be several of them) have certainly been formed directly on the sea-bottom," t commits himself to what we expect will turn out to be an erroneous conclusion. Dismissing the silaeid ractamorphies for the present, Sterry Hunt's theory of the origin of the Canadian Archseans in their totality necessarily makes the interbedded "crystalline lime- stones " a " chemical deposit; and there is no doubt that a part of these limestones, like those of more recent formations, Iiave been directly precipitated by chemical reactions from the waters * Nature, August 22, 1878, p. 444. t Article " Geology," iu ' Eucycloptedia Britannica,' vol, x. p. 288. \' I 1 I i- i II ;h 1 76 R0CK-METAM0RPHI8M. of the ocean/' to " reaciionsj which are still going on in the ocean's waters, and which have, in past time?, given rise directly to limestone strata, in Avhich the occurrence of shells and corals is only accidental" ''\ That the latter deposits arc in the main of organic origin is doubtless the opinion of most geologists ; but a difficulty in connexion with this point has arisen as regards the Archaean hemithrenes. To those >vho believe in " Eozoon/' with the exception of Sterry Hunt, the organic origin of the Canadian hemithrenes, it may be assumed, is a settled matter. But it mvist be admitted, even by those to whom we refer, that there are others who totally dissent from this belief, and who, besides, reject the theory of chemical precipitation. Obviously, then, the onus lies with them to suggest or propose a different solution of the problem. It would be rash on our part to deny that organisms of any kind were in existence during the Archaean periods; but our researches having afforded no proper evidence in support of the affirmative, we ai'e induced to make the attempt to solve the question, as to the origin of the Canadian hemithrenes, other- wise than by the doctrine either of organic intervention, or chemical precipitation. Reverting for a moment to the Laurentian silacid rocks, our view as to their origin is based on a full recognition of existing operations pertaining to physical geography : it involves the intervention of mechanical and chemical agencies in effecting the disintegration of rocks already in existence ; also the removal and dispersion of the materials derived therefrom, and their consequent deposition in other and distant areas. It will therefore not be unreasonable to regard the Ontarion funda- « 1. 1 '1 ! ' ■ J ; 1 80 ROCK-METAMORPII ISM . and all-pervading, in deep-seated rocks, as repeatedly contended for by the author, the fact may be taken as positive evidence that the "granitic veins " and the peculiar pyroxenic beds ■vverc alike penetrated by such solutions, whose solvent powers were exerted on the mineral silicates, whether belonging to the beds or the veins. As to the " marked contrast " which it is endeavoured to make out between the "rounded irregular grains " of the former and the " rounded crystals " of the latter, it seems extremely doubtful that the difference is more than one of degree : it is not, however, beyond an explanation on our view. As the veins are clearly posterior to the beds, the latter have an important factor in their favour : time would enable the corroding agents to act more decidedly and more generally on the " grains " in the beds than on the " crystals " in the veins. Moreover the "contrast^' may also be due to a difference in solvent power between the penetrating water in the two eases. Again, the action of solvents, by rounding the " grains " or " crystals," involves removal and displacement, whether it takes place in beds or veins ; and as there are no openings surround- ing either the grains or " crystals,^' but on the contrary an environment of calcite, obviously the latter is the replacement substance. And it may be equally affirmed that all the calcite which occupies the interspaces between the grains and crys' ^s is in the same predicament, as in certain pseudomorphs w mineral silicates have been replaced by a mineral carbonate. Applying this reasoning to the solution of the problem in regard to the origin of the Canadian bedded " crystalline lime- stones " or hemithrenes, it will be understood that we have simply to enlarge the field of solvent action. We may take a region occupied by contorted granitoid, labradoritie, horu- blendic, and other gneisses, permeated by thermal water charged with a earbacid solution — the water having gained admission into the rocks either directly or indirectly from an overlying ocean, along zones of outcrops, jointing, or porous beds, the dir etion of such zones corresponding to the strike of the rocks : by this means the gneisses would become regionally converted into hemithrenes, the quartzo-feldspathic diorites, with their admixtures of calcite and serpentine, being "beds of passage between the two rocks." - • .J-^v ti'." ~'~ .' I "crystalline limestones" op CANADA. 81 =' i« We may uow summarize the evidences and considerations which have been brought forward by way of substantiating our view as to the origin of the Archsan " crystalline limestones '* of Canada — that they were silacid metamorphics which have become chemically and otherwise changed or methylosed into calcitic masses (hemithrenes) , it having been shown : — That the calcite of the calcareous structures of " Eosoon " in the ophite of the Canadian Laurentians is a replacement of serpentine and other mineral silicates ; That the mineral silicates, augite, hornblende, &c. (character- is. ic of hemithrenes), are often pseudomorphosed into calcite ; That only under extremely limited conditions are chemically precipitated limestones formed ; That no reliable evidences have yet been adduced proving the existence, during the Archaean periods, of lime-elaborating organisms (the only other kind of agency admissible on our part), through whose intervention the ''crystalline lime- stones " could have been formed ; That the peculiar convoluted or tortuous lamination which distinguishes many of the " crystalline limestones " is only explicable, in the absence of cases to the contrary, on the idea of its being a superindurod phenomenon ; That the " crystalline limestoni >," also the associated ophites, are most abundant where they are interbedded with silacid rocks (" pyroxeny tes ") , whose essential minerals contain a large percentage of calcium (and magnesium) silicate ; That thegneissose rocks of St.-Philippe (Vosges) and of Glas- sillaun (Cleggan Bay) have been converted into hemithrenes by chemical action ; finally. That the great Archaean limestone formation of Canada consists of silacid gneisses which " pass insensibly " into hemithrenes through decrease of mineral silicates and increase of carbonate of lime, — that this formation is inter- sected by " granitic " and " calcareous veins," between which " it is easy to trace a gradual change," — that the " pyroxeny tes " and beds of limestone, also the " granitic " and " calcareous veins," include in a general sense identical crystalline siliceous minerals, with their surfaces more or less corroded by the dissolving action of heated water con- o 82 ttOCK-METAMORPIIISM. taining carljacid solutions, ever present in deeply-seated rocks, — and that, under the influences stated, the " granitic veins " and the bedded " pyroxenytes " have gradually undergone changes, which eventually converted them re- spectively into " calcareous veins " and beds of " crystalline limestone/' If any extensive beds of really pure limestone, resembling carrarite, are included in tlie great Archsean class of rocks, we should, rather than ascribe them to simple mineralization as we do the marble named, prefer the suggestion that they have been deprived of mineral silicates through the latter iiuving been washed out by dissolving waters. BJi I t UARITV OF POST- ARC HiEAN LIMESTONES. 88 CHAPTER XIII. WIIY ARE LIMESTONES COMPARATIVELY RARE IN TriE FORMATIONS IMMl':i)IATELY SUCCEEDING THE ARCIIyEANS ? It has long been a matter of surprise that the Cambrians (the great series of rocks from the base of the Longmynds to the top of the Tremadocs)^ exceeding by far 40,000 feet in thickness, contain very few limestones; and the surprise is heightened when the paucity of the latter formations is compared with the vast masses of calcareous members belonging to the Archeeaus. We are referring to the Cambrians as they occur in Wales, Scotland, and Ireland, where their calcareous matter, comparatively a mere fractional constituent, is generally in a diflFused state, or forming only thin layers. Even by including Hicks's Dimetian series (which, however, he regards as Archaean) , the " limestone beds " it contains at Porthlisky would form no valid exception to our statemeni, particularly as there are strong grounds for the opinion that they, and the ophite associated with them, do not retain their original composition''^. * Dr. Hicka has kindly favoured us with two small specimens taken from the " impure limestone bands " (from 1 to 3 feet in thickness) of Porth- lisky, and belonging to his Dimetian sories. This is separated by uncon- formity from his Pebidian series. lie ia inclined to consider both as Archaean, the PebidiauB being overlain unconformably by unaltered Harlech grits. Wo find the specimens to be principally composed of white augite or mnlacolite, in short well-cleaved crystalloids confusedly aggregated. After decalcifi- cation they present themselves separated by interstices, cavities, and con- tinuous passages, which before had been filled with calcite. In many instances the crystalloids of malacolite are translucent, and their angles are sharp ; but oftei?. they are opaque, rounded, and iucrusted with white floccu- lent matter. Every thing observed in connexion with the malacolite and calcite convinces us that the former is in course of replacement by the latter. The calcite is more abundant where the crystalloids of malacolite are eroded g2 iii^' I ( I : IMi 84 llOCK-METAMORPHISM. It is not until the Lower Silurians are reached that limestones are found to occur to any extent ; and these are either very impure, as in the Llandeilo flags, or they form thin beds, e. g. those in the Bala limestone oi the Caradocs. The Durnes lime- stone in Sutherlandshire (a partly mineralized rock, older than our Llandeilo flags, and probably the etiuivalcnt of the Stiper- stones, the bottom of the Lower Silurians) and the Coniston limestones may be regarded as improvements on their Welsh equivalents. During the Upper Silurian period a marked change took place : limestones were developed on the graiulest scale ; and s^incc then the formation of the same class of rocks to the like extent has continued throughout every succeeding period. On the continent of Europe a similar scarcity of limestones characterizes the C!arabrians, while a fair increase in their amount ir.arks the Lower Silurians. In North America the Cambrian limestones oft'er no very marked exception to contemporaneous formations in the British Isles or on the Continent. Of the Acadian and Potsdam groups, which have been bracketed with the Welsh Llongmynds, Harlech Grits, and some other Lower Cambrians, the first contains no recorded non- crystalline limestones*; while the second only comprises some of inconsiderable thickness and occupying but small areas : such arc the red sandy dolomites and other calciferous formations of Troy (N. B.), North-western Vermont, the Straits of Belle Isle (Newfoundland), and a few more places. and covercd with flocculite (which substance can only be their residue) than where they are shai-p and translucent. The crystalloids of malacolito in a few coses were observed to be so far decreted as to assume rudo branching forms. In one instance of this kind the form closely resembled typical imi- tative configurations. Intermixed with the calcite and malacolite we found a pale greenish-yellow granulfir substrmce resembling serpentine, bundles of prismatic epidote or actinolite, magnetite in octahedral crystals, a triclinic feldspar showing striping, and galena. This case strikingly resembles the one at Cleggan. If these specimens are characteristic of the limestone beds at Porthlisky, there can be no question about the latter being methylosed products. * For reasons which will be understood after a perusal of the last para- graph of the present Chapter, we confine our remarks on the question under consideration to unaltered limestones. RARTTV OF POST-ARCH/KAN LIM KSTOXES, 85 1. 1 the Canadian group, presumed to correspond with our Upper Cambrians, wc have evidence that a further increase of limestones took place, while the Chazy limestone (considered to be the youngest member of this group) and the Trenton lime- stones of the Lower Silurian system afford ample evidence of an abundant increase of the calcareous element. With reference to the large increase of limestones in the last- named formations, the fact must be tuken as showing that in North America the increase took place earlier than in the Euro- pean areas. Cconnected with this is the remarkable fact, already stated, that the earliest Palaeozoic formations (those constituting the two Cambrians) contain few fossils with ordinary calcareous skeletons. Besides some others (fucoids) of no importance to the question at issue, the Cambrians yield the remains of Protozoans, Crustaceans, Coelenterates, Mollusks, and Echinoderms, occa- sionally in abundance, and some of them {Paradoxides) of gigantic proportions ; instead, however, of the skeleton of these organisms being ordinarily thick and composed of lime, as is general in certain of their classes respectively, they are (admit- ting a few apparent exceptions) thin, and for the most part horny, with comparatively a small quantity of phosphate of lime, and a much smaller of the carbonate — a circumstance which may be taken as favouring the idea that the Cambrian stages of organic development were not much beyond that of the larval evolution of the invertebrates whose remains have been noticed*. The absence of calcareous fossils, and the rarity of limestones in the Cambrians, it may therefore be assumed, are correlative phenomena. It would seem tha+ the seas of the very earliest Palteozoic periods were poorly charged with calcic constituents, and that they were thinly tenanted by lime-elaborating organ- isms. Was the latter consequent on the former? The Cambrian rocks, whether occurring in North America, on the continent of Europe, or in the British Islands, consist of * Mollusks and other invertebrates in their larval condition have homy shells. It seems extremely doubtful that there was much calcic matter of any kind in the Cambrian trilobites. Stony corals have not yet been found in the Cambrians. ArchtBoq/atfius Atlanticus (presumed to be a sponge), from the Potsdam of the Straits of Belle Isle, Newfoundland, may be calcareous, Stems of crinoids occur in the Potsdams, i 1 i ' 1 h i li : i \\> lit I .1 86 norK-MRTAMonniisM. matorinls pvcriNPly such as would rcmilt, from the nioohauical dcgradntion of tho p^noissos, syonitps, and other silacid mombera of tho Arehroans. Tho ahundatioo of argillytos, saudstouoa, and other nioehanionlly prochu'od deposits, tho rai*o acoonipanimcnt therewith of limestones, and tho eontemj'.orancims presence of non-oaloareo\is fossils admit of no diflleult explanation ; but wlien viewed in eonnoxion with tho oeeiirreuee of (UM)() feet of erystalline limestones in Iho preceding Archnjans, the problem beeomes inexplicable. It must strike every ficologist that, if s\ich an enormous thick- ness of (Milcareous rocks was available duriufj; tho Tiowor Cambrian ]>eriod (that is, when thes(^ sandstones and argillytes were in C(Uirse of derivation, tln'oup;h disintcfj^ration and denuda- tion, from the Archjvan gneisses Sic), wo ought to expect that the great lime-bearing series referred to yielded, through organic intervention, a considerable an\ount of iinu^stones. Hut Mhere are they ? ( Vrtainly not in the dilVuscd qiumtities, or the ''belts" and "bands," that are known, particularly as it is questionable that the linu^ in these cases is much in cxocss of tho amoiu\t whi(»h could have been generated by tho contemporary notion of the carbonic acid, then ])crvading the atmosphere and different waters, on the calcium silicate in tho labradoritic, hoi'nblcudic, and augitic debris produced by tho disintegratiou and denmlation of the Archjoans during tho Cambrian periods. With respect to the period when tho Archaean crystalline limestones Avcre completely elaborated (for our hypothesis in- volves slow j^rocessos requiring immensity of tinu"),MO can offer no decided opinion. It would aj>pear improbable that their denudation, operating throughout a vast chronological term that embraced tho two Cambrian periods, and producing miles in thickness of debris, would give rise to no more than the small quantity of limestones that m ere deposited during these periods. On tho other hand, however, there seems to be great probability that ihe crystalline limestones constituted the great factors which so vastly increased the number of organisms with calcareous skeletons, and the consequent calcareous deposits, during the Silurian periods. To account for the paucity of early post- Archaean limestones, we offer the suggestion that, during the Lower Cambrian period there was no great series of crystalline limestones included IIARITV OF F()NT-AllCI!i«AN MMKSTONKS. 87 among tho Arclienan i'ocUh, that tli(3 liomitliiniioH and ophitrn conHtitiiting this Horios wore only in prornHsololaboration when th(! Lower CanibiianH worn in conrHo ol' fornrntion. It wonld 1)0 ol' injporlanco to l(3arn if any N|)('(!inirnN oC lionii- thivnc or ophite oecMir in the Arehican confflomerato of tho {^onlon^e river and other plaecM. The eircnnistance wonld have to be aeee|)t(Ml as provini^; that the metliylosis wliieh had de- veloped the erybtalline linu'stonefi luul s !t in antecedent to the formation of the conglonu'rat(\ The explanation involved in the above snggention embraees all the facta of a problem Avhieh is nnresolvablc by either of the doctrines we are opposed to, as regards the origin of tho Anilmum hemithrcnes and ophites; for if one were trnc, its advocates w(ndd be able to point to something less vulnerable than sparingly-developed limestones of tho Cambriims ; or if the other were a fact, its R\ipporters would be able to refer to other than the little better than corneous I'ossils characteristic of the same rocks. Again, why chemical calcareous precipitates shonld cease, or why the presumed " Eozcou Canadense " should precede others only furnished with skeletons of a larval ty])c, while it never puts in an appeaiancc subsequent to the Archsean periods, except in the like nicthyloscd and crystalline rocks, as the ophites or hemithrcnes of (Jonnemara, Ceylon, Akcr, Mt. St.-Philippc, the Isle of Skye, and other places (most of them considered to be Postarchajan, the last-named one being Jurassic), arc also questions which require to be satisfactorily answered. In the meantime wc must continue to put faith in our sug- gestion that the rarity of limestones in the Lower Cambrian system is due to the absence of preexisting calcareous rocks from which they could be derived — that the great scries of Arclucau crystalline limestones, which would represent such prcexii Jng rocks, was only imperfectly elaborated during the Lower Cambrian period. This we beg to be accepted as our answer to the question, Why are limestones comparatively rare in the formations immediately succeeding the Archaeans ? The preceding observations, we wish it to be understood, refer to Cambrian calcareous deposits that have undergone neither mineral nor chemical changes : we arc thus particular because it is well known there are certain metamorphosed groups which com- prise crystalline limestones and ophites, in Canada, the State of f, II ■' I il n' 88 ROCK-METAMORPIIISM. Now York, nnd Ncav BrunsAviok, considered })y many geologists to be of poat-Archrcan age, as tlio altered Qnebecs, Emmons's '' pri- mary limestones/' &e. A corresponding formation (the lime- stone of Essex and adjacent eonnties) is considered by Pro- fessor James Hall to belong to a " period snbseqnent to the deposition, metamorpbism, and diatnrbanec of the rocks of anthentic Laurentian age," and to apparently bold a place in the series between the Laurentian and the " Potsdam periods ; but whether of Iluronian age or otherwise " he does " not pre- tend to say ; and it may even prove of later date than this'**. Cont(Miding f(n' the existence of true Archaians or Lauren- tians in the higldand region of Northern New York, and that these rocks are uneonformably overlain by a younger and well-developed series of gneisses, mica- and hornblende-schists (inehuling crystalline limestones and ophites) in Westchester and oiher adjoining counties. Prof. Dana has of late endeavoured to prove, by their relations to certain fossilifcrous deposits occur- ring in neighbouring places, that the younger metamorphies are of Upper Cambrian and Lower Silurian {'' Calcifcrous," ''Quebec," '' Chazy," and "Trenton'') agesf. Should this prove to be correct, there will be no need of trying to make out that the crystalline limestones they contain were ever other- wise than calcareous ; for as such they may have been simply mineralized. Nevertheless it docs not seem improbable that some of the Westchester crystalline limestones maj be raethy- lotic products, particularly as there is no reason to exclude from the series containing them two or more older groups, the Acadian and Potsdam, whose remarkable deficiency of cal- careous matter in their unaltered condition would render it highly probable, should they in their metamorphosed state contain well-devoloped crystalline limestones and ophites, that metamorphosing agencies had generated such limestones. * ' American Journal of Science nnd Arts,' 3rd series, vol. xii. p. 300. t Amoricnu Journal of Science 'and Arts,' 3rd series, vols. xix. and xx., "Geological Relations of the Limestone Belts of Westchester Co., N. Y." The reader is referred, in this connexion, to Selwyn in ' Canadian Naturalist,' new serie.o, vol. ix. pp. 17-31 . MINERALIZED CKVSTALLINE LIMESTONES. 89 ,"^f >» f CHAPTER XIV. SOME CKYSTALLINK LIMESTONES ARE SIMPLY MINERALIZED. It will be recollected that we have made an exception to cer- tain crystallized calcareous rocks related to hemithrenes being of purely mcthylotic origin. It seems probable that this excep- tion may apply to the marbles of Dalnein in Strathdon, Glen Elg, Glen Tilt, and the neighbouring localities : still we cannot altogether reject the idea that there are no methylosed examples amongst these marbles, even should they beof post-Arehrean age, just as it may be doubted that all the Westchester crystalline limestones arc simply mineralized products. The fact men- tioned by Dana that " green hornblende in minute rounded crystals is occasionally found disseminated through the lime- stone of Westchester," and the similar well-known fact of the Scotch marbles being shotted with deereted crystalloids of augite &c., involve the action of corroding or dissolving solutions — the prime agents in methylosis — which marbles, according toHeddle, contain trifling specks or remains of augite, and are of post- Arclnean age ; and for this reason doubts may be entertained of their belonging to the group treated of in Chapter X. But we see no improbability of an impure limestone belonging to the Cambrian, Silurian, or later systems *, throngh mineraliza- tion, changing into a rock which it would be difficult to distin- guish from a hemithrene f. Therefore, until further light has been gained respecting the geological position of the marbles of Glen Elg and other places referred to by Heddle, and generally considered to be Upper Cambrian or Lower Silurian in age, we consider it safest to admit that some of them may have been calcareous in their original condition, especially as the Durness limestones are proved to be early Palssozoie by their fossils. * Some of the Scandiuavian " primary limestones,' described by B. Cotta ( Zeitsclirif t der deutsch. geol. Gesellscliaft, 1852, Band iv. pp. 47-53), are undoubtedly of this class ; but we strongly suspect that many others he hua noticed (Aker &c.) are methylotic. t Excluding its ophitic portions, much of the Isle-ot-Skye " white marble " may be an example of mineralized limestone. . V *^;**- ■i'* !"^ * 90 ROCK-METAMORFHISM. U I , Many of the bedded crystalline calcitic rocks of Connemara appear to be simply mineralized metamorphics. There are calcareo-siliceous bands, more or less crystalline, commencing at Lough Bofin, a little north of Oughterard, and skirting, apparently continuously, the mail-road on to Ballinahinch, thence across the mountains to Letterfrac*. There are good reasons for believing that they were also originally impure limestones. Still we entertain a suspicion that the " crystalline limestones " which have been noticed, by Mr. R. Glascott Symes, occurring in what appear to be corresponding metamorphic schists in Mayo, will turn out to be methylosed hemithrenes. They are " seldom following the foliation of the beds, but occur along lines of great fault/' " From such evidence,^' according to Mr. Symes, "it may be assumed that this crystallized limestone has been formed by infiltration or percolation of bicarbonate of lime, from the once overlying Carboniferous rocks, into joints or cracks in the now metamorphic series.'^ Prof. Hull, however, expresses his aversion to this view, and considers these limestones " to 1 elong to the group of strata in t; lilch they are found, just is similar limestones do in the "Vv est Galway district "f* It is highly probable that the pure marbles (carrarite) of the Apuan Alps are simply mineralized. But it rarely happens that the Irish cases to which we have referred are unassociated with methylosed rocks — that is, beds chemically changed into dolo- mites, ophites, and even into true hemithrenes. Moreover the limestones in the north-east of Donegal are undoubtedly no more than mineralized, and probaV'V of Lower Silurian age ; while the calcitic rocks occurring farther west, filled with ido- crase and other mineral silicates, t-nd interbedded or intimately associated with granites &c., may be of methylotic origin and represent a much earlier geological period. * We are not sufficiently acquainted with the stratigraphy of the calca- reous marbles and ophites of the Bama-Oran district, east of Ballinahinch, to offer a decided opinion as to whether the former are methylosed or mine- ralized — though, from their being associated -with the latter, the probability seems strong to us that they were originally silacid rocks. t Explan. Mem. of Sheets 41, 63, and 64, Geological Survey of Ireland, p. 12. Mr. Symes mentions f^'Saet cases of the kind occurring in Mayo — beds of micaceous limestone in mica-schist, in some places traversing the latter at right angles, at others folio-wing the direction of its folia. See Expl. Mem, of Sheet 75, p. 12, and Expl. Mem. Sheets 63 and 74, p. 11, \ \ METHYLOTIC ORIGIN OF DOLOMITES. 91 CHAPTER XV. DOLOMITES AND DOLOMITIC ROCKS HAVE UNDERGONE METHYLOSIS. Dolomites, in our opinion, are in all cases products of methy- losis; but the phenomena have been eflPectcd in two different ways — one by substitution of their original basic and acidic compo- nents, as in the dolomitic hemithrenes of the Canadian Archseans, and the other by replacement, more or less, of only their original basic carbonate of lime. Although the rocks we propose to con- sider in the present Chapter are of sedimentary origin, it must be understood that we do not deny the probability of certain igneous and silacid masses (veins and dykes in the Canadian Archseans), through methylosis, having been dolomitized. But the rocks we are more ^irectly engaged with are the mag- nesian limestones which, chiefly belonging to various systems of the primary and secondary groups, are spread over extensive areas of Europe and North America, and beneath or associated with which nothing is present except sedimentary deposits in an unaltered condition. Our typical example is the Permian magnesian limestone of the north of England. Various opinions have been propounded as to the origin of the magnesian carbonate present in this limestone and others analogous to it. There are some, as Apjohn, T. Richardson, Hunt, and Ramsay, who believe that this compound is an original constituent; while others, as Virlet, Scouler, Haid- inger. Von Morlet, Bischof, Johnston, Sorby, and Hardman, make it to be a superadded ingredient: the last opinion is methylotic. But let the different opinions of both classes be exam'-^ed, and it will be found that all are at variance as to the modus operandi which has developed the magnesian con- stituent. Von Buch's celebrated theory of dolomitization (applied, however, to rocks we have excluded) advocates that the lime- stones forming the dolomite mountains of the Tyrcl have . iiiiflinii I t. i . gularity ; they have been in'egulavly recurrent, and have varied in horizontal and vertical extent, in time-limitation, and in force, as evidenced by the sudden and repeated changes (from freshwater to marine conditions) in rocks of a formation, the presence of a well-developed formation over a certain area and its absence in another and contiguous area, the dissimilarity between sya- ■ 102 BOCK-METAMORFHISM. satisfied, however, that the group contains formations referable in the main to the difierent stages of a cycle of vertical move- ments, I cannot but regard u as of systemal rank, though I admit that it cannot be equalled in comprehensiveness with certain other rock-systems. The following table exhibits a series of formations representing the different stages, as successively developed in the course of a cycle of vertical movements which took place during the Permian period : — Lancashire Triassic Bimter sandstones. 5th Stage. St.-Bees (Whitehaven) red sandstones. ^fh Stage, Manchester marls and thin-bedded limestones. Yorkshire and liarroAvmouth (Cumberland) Schizoih(s-\in\sioxxes and gypseous marls. Sunderland coralloidal limestones. Hartlepool and Marsden lime- stones. Ardtrea (co. Tyrone) magnesian liaiestone. ^rd Stage. Ilumbleton (Di^rham) fossiliferous limestones. 2«rf Stage. Midderidge (Durham) compact limestones. Durham marl-slate. Ist Stage, Ponlefract sandstones. Solway red-sandstones. "\Vestoo (Durham) SigiUana-HAnAstones. Coal-measures of the Carboniferous system. i chronous formations in separated areas of one and the same region, and the vast difierence in thickness of the rocks severally constituting the different systems. Eock-systems are often deficient in formations representing the 1st and 5th stages : such arc usually tripartite, as the Triassic ; though in some instances of the land the missing formations have doubtless been removed by denuda- tion, which, as will bo readily understood, must be energetic dm-ing these two subaerial stages. The Carboniferous system may be taken as an example in which all the stages, especially the Ist aiid 5th, are well represented. The Triassic system, which on the continent comprises three foi-mations cor- responding \di\\ the 2nd, 3rd, and 4th stages, is in the British Isles devoid of any representative of the middle one (3rd) of these stages. On the other hand, this stage is well developed in the Cretaceous system of the south of England and other countries j but the 5th stage is poorly represen d in most regions, except, seemingly, in the Eocky Mountains and the uioix western ranges, where occur intercalated formations containing Atnmonites Bacnlites, Sec, and Tertiary plants, which indicate the missing time-link between the Cretaceous and Eocene periods. (See Prof. J. Stevenson American Philosophical Society, June 18, 1875.) APPENDIX. 103 I i irable nove- lOUgll i with jnting je of a srmian imstones len lime- 1, and the different [st and 5tli instances )y deniida- 'ing these HI example ^presented, [ations cor- sles devoid the other |e south of represen d [d the moit [mmonites, time-link Stevenson, To accept Dr. Ramsay's belief, it would be necessary to over- look altogether the middle (or 3rd) and much of the 2nd forma- tions of the Permian system. Reverting to Dr. Ramsay's grounds for assigning a brackish- lacustrine origin to the Permian rocks in general, I propose, in the next place, to notice the one founded on the " poverty in number of the fossils " they contain. Conclusions on this point are not to be influenced by consi- derations arising from the study of individual characteristics, but of general facts. Evidently Dr. Ramsay has been in- fluenced in his belief by the fact that brackish lakes, com- pared with sea-basins, are sparsely inhabited by molluscs ; but he overlooks another .fact of importance, that depths exceeding 100 fathoms are not so prolific in animals of the kind as shallower bottoms. " Poverty in number " as a feature of deep-sea life affords a more satisfactory explanation of the point in question than the corresponding feature in its brackish- water relations. The same argument attaches to the " dwarfed aspect " of the Permian invertebrates ; for the term " dwarfed " is equally applicable to a deep-sea fauna, which usually consists of small and delicate species. Such forms as Productus horridus, with its long projecting hinge-spines, and Fenestella retiformis, with fragile fronds six to eight inches in spread, and several other tender organisms could only live at considerable depths, where still water prevailed. But it cannot be said that the Permian fossils are particularly dwarfed ; the Bryozoon just referred to is a strong fact against any statement of the kind. Spirifer alatus does not compare unfavourably with most of its Carboni- ferous congeneric species ; and Camarophoria multiplicata is a match for the largest of its allies, C. Kingii (Davidson), of the Carboniferous limestones. Several other Permian fossils could be mentioned in this comparison. It is quite true that, so far, the Permian rocks have not yielded any thing equal to Productus giganteus and P. ponderosus and other heavy fossils, especially corals ; but these may be safely consigned to shallow seas. It is necessary to mention that the Permian palliobranchs were denizens of deep water ; for in fossiliferous beds which bear all the marks of having been formed in shallow water these shells are absent. Certain beds of coralloidal limestone 104 ROCK-METAMORPH ISM . I I': m. ! I h .SI ni r si lii- j ii 1^ ; i 1 i |j on the shore at Sunderland which came under my notice have their surfaces distinctly rippled j but they contain no fossils of the kind — merely bivalves {Schizodus &c.) . These beds, however, do not belong to the deep-water stage; for they overlie the limestone (fossiliferous par excellence) which crops out at Hum- bleton and other inland locaHties. Other beds occurring in Lancashire, Yorkshire, and Cumberland, which possess similar paltcontological characteristics, arc referable to the same stage. Another fact of importance, which also seems to have been overlooked by Dr. Ramsay, is that the Permian invertebrates, which he assumes to have lived in '^ brackish water '^ of an " inland unhealthy nature,^^ are, as a rule, well-developed species, and bear the stamp of having inhabited an open sea. How can it be conceived that palliobranchs, only known as denizens of the sea, could exist in brackish-water lakes ? As to why an exuberant variety of invertebrate marine life is not a characteristic of the Permians, it must be borne in mind that information on the distribution of these rocks is still very limited. In the face of certain deposits in North America and Central Asia, doubtfully referred to the Carboniferous, or Permian Triassic system, it seems preferable to wait until they have received fuller attention. In the Austrian Alps and^ in Northern India there occur fossils {Ammonitidee, GoniatQae, &c.) of types indicating that the rocks containing them may be of Permian age. Now, as my theory of regional cyclical vertical movements admits of different conditions prevailing at the same time in separated regions, it is not at all improbable that the marine formations referred to may belong to the pelagic stage, and nevertheless be synchronous with those which in Western Europe gave birth to the shallow- water and cstuarine (2nd or 4th) de- posits of the Permian system. I would suggest the application of this argument by way of explaining the difference between the rock-systems of Europe and their presumed equivalents in extra-European regions. Dr. Ramsay has introduced into his remarks on the Physical Geography of the Permian Period * another matter, which he * Op. cit. pp. 149, 150. APPENDIX. 105 have Ills of rever, le the Hum- ng in imilar same J been brates, of an reloped en sea. Dwn as e life is n mind till very fica and ous, or til they and^ in may be Ivements Itime in marine |,ge, and Europe tth) de- )lication Ibetween llents in i*hysical l^hich he evidently thinks supports his belief, but which, as will be learnt from a perusal of Chapter XV., I am totally opposed to. To quote his words : — " I repeat that the Permian magnesian limestone was not, as used to be supposed, formed in the sea, but in an inland salt lake, under such circumstances that carbonates of lime and magnesia were deposited simultaneously, probably by con- centration of solutions due to evaporation. In an open sea lime and magnesia only exist in solution in very small quantities ; and limestone rocks there are formed (as in coral reefs) by organic agency.'^ If, as seems to be meant by the last sentence, lime and magnesia are unlikely to be precipitated in an open sea (a view I quite agree with — not, however, because salts formed of these bases arc in small quantities, which statement is a slip of some kind), it is to be apprehended that there is little chance of their being deposited in an inland salt lake, consider- ing that Dr. Ramsay has not been able to point out a single instance of the kind. " In some of the lower strata of the magnesian limestone, when weathered, it is observable that they consist of many curious thin layers, bent into a number of very small eon- volutions, approximately fitting into each other, like sheets of paper crumpled together. These dolomitic layers convey the impression that they are somewhat tufaceous in character, as if the layers, which are unfossiliferous, had been deposited from solutions. In other parts of the district, along the coast of Durham, large tracts of the limestone consist of vast numbers of ball-shaped agglutinated masses, large and small ; and I have observed in limestone caverns, iu pools of water surcharged with bicarbonate of lime, that sometimes precipitation takes place on a small scale, producing similar nodular bodies. It is notable also that, when broken in two, many of the balls are seen to have a radiated structure ; that is to say, from the centre rudely crystalline -looking bodies, all united, radiate to the cir- cumference. In other places we find numerous bodies radiating in a series of rays that gradually widen from the centre, and are unconnected at their outer ends, which reminds the spectator of radiating corals. There is, however, nothing organic about them ; and I do not doubt that they owe their growth to some kind of crystalline action going on at the time that the limestone was being formed.' }) i|i:j MiPIII P 106 R0CK-METAM0RPHI8M. h il The facts on which the above description is based I must regard as affording no more support to Dr. Ramsay's belief than the fossils that have been under consideration. It appears to rae that the coralloidal and other bodies described in the foregoing extract, besides having been examined with insuffi- cient deir jration, have not been considered in connexion with the evidence adduced by Sedgwick and myself, proving them to be of superinduced origin. I pointed out upwards of thirty years ago their relation to well-developed rock-jointing*, a fact which may be unhesitatingly accepted as disproving the idea " that tliey owe their growth to some kind of crystalline action going on at the time the limestone was .being formed." And Avith respect to the presumed identity between the " ball- shaped agglutinated masses" of the Permian limestones and the " nodular bodies precipitated in pools of water of caverns," the two phenomena .are not to be compared, — the one (taking ordi- nary stalagmitic deposits into consideration) being a simple product, and the other a complex development — the " balls " of the " masses " essentially consisting of carbonate of lime, and their matrix of carbonates of lime and magnesia. In conclusion I would respectfully urge on Dr. Ramsay to consider the various points that have been adduced against his belief; at the same time I mn xpress myself as indulging in the hope that the next edition of his valuable work will contain views on the physical geography of the Permian period more in harmony with the general evidences of the case. * See Supplementary Note B, -i .1 ^t'k SUPPLEMENTARY NOTE A. 107 SUPPLEMENTARY NOTE A. a the lamsay o-ainst Iging will riod In the abstract referred to in a previous page I first broaehed the hypothesis of cyclical vertical movements on a regional scale in connexion with '' Rock-jointing in its relation to Phe- nomena in Physical Geography and Physical Geology;" and as the subjects it treats of are of general importance^ and exciting much attention just now, I may be excused introducing them into the present note. In my Report on Jointing and Slaty Cleavage^ which appears in the 'Transactions of the Royal Irish Academy/ vol. xxv. (1875), reasons are given in favour of the doctrine that jointing is Vi physical phenomenon, which, constituting lines or zones of weakness in the earth^s crust, has permitted subterranean dis- turbances, often accompanied by igneous upbursts, to follow tho courses of these zones *. With respect to slaty cleavage, in consideration of various evidences adduced in the Report, I have for several years jmst maintained that it is the result of pressure consequent on subterranean disturbances exerted against planes of jointing (Bangor slates), or dcpositional partings (Dclabole slates), — thus bringing them into approximate or immediate contact. Since the Report appeared, Daubree has given a description of some experiments which he regards as proving the mechanical origin of jointing. By means of torsional pressure applied to plates of ice, he has developed, in the latter, groups of " approx- imately parallel" lines of fracture, crossed by other lines nearly at right angles. But I cannot regard these experiments otherwise than as simply illustrating the well-known truth that similar effects are produced by dissimilar causes ; and it may be strongly contested that ice, crystalline in its origin — in which it is doubtful that structural planes, original or superinduced, are ever absent — is a suitable substance on whicli to experiment by way * This doctrine suggested itself to mo on my becoming acquainted with an early speculation in dynamical geology of Phillips's. See op. cit, pp. G37 and G38, and Phillips's lleport Brit. Assoc. 1834, p. G57. » w wii m C% m I | T# i B ^ iiii I ■» I I.P W ■5W |! 108 ROCK-METAMORPUISM. of illustrating a phcnoraenou abundantly characteristic of me- chanicnihj deposited rocks. I do not deny that pressure, under certain conditions, has produced parallel fractures in rocks; and examples could be cited of a mechanically developed parallel divisional structure such as some geologists have taken for jointing. Still, as jointing is common in its indisputably typical or normal condi- tion, without a tittle of evidence of mechanical pressure having been in any way concerned in its development, obviously a physical causation must be ascribed for the plienomenon. As stated iii my Report, there are miles and miles of Carboniferous limestone, in nearly horizontal beds, forming the bare surface of many parts of counties Clare and Gahvay, in "vvhieh jointing is wonderfully developed ; but nowhere is it accompanied by evidences of crush or stratal disturbance involving a mechanical causation. On the contrary, the phenomenon so closely simu- lates mineral cleavage in fineness, and it is so completely divested of all indications of supervened compression, that the view of its mechanical origin, advocated by Daubree and others, must be regarded as completely at fault. M. Daubree, however, by way of adducing some evidence of the required pressure in rocks, has brought forward a case notified by Harkness and examined by myself*. It is an instance in Carboniferous limestone near Cork, which not only comprises typical jointing, but shows indisputable evidence of the rock having undergone powerful compression. This case, however, is altogether valueless with reference to tlic mechanical hypothesis; for it can readily be proved that the jointing (which is meridional) has been developed after the rock had become compressed. Clearly the divisional structure in this instance is altogether independent of compression. The fact is, the Cork limestone (as well as its associated rocks) has been flexured into cast-and-west rolls, corresponding in direction with an old equatorial jointing, traces of which are still to be seen in the roughened and dislocated divisional planes everywhere present. On the contrary, the jointing referred to by Daubree cuts cleanly through the disturbed rocks, north and south, and holds on for miles in the same way as the meridional jointing of Ireland generally. * Op. cit. pp. G38 & 039. SUPPLEMENTARY NOTE A. 109 )n in fhcvc ibree and iting In the matter of slaty cleavage, Sorhy (who, it is well known, ably supported the view originally brought out by Daniel Sharpe many yeare before my Report was published) has of late returned to the subject. In his Anniversary Address, as President of tiie Geological Society, he makes known some microscopic observations in connexion with the development of slaty cleavage. It would appear " that, though in some cases" his " original explanation of very perfect cleavage may be true " (that is, du(^ to pressure alone, aad independent of any pre- existing divisional structure), he now recognizes "fine lamination in the ]) lane of deposition," and " very close joints," as noteworthy agents, and affording an "explanation which removes a vci*y seri- ous difficulty in completely explaining the mechanical origin of slaty cleavage in rocks which have yielded to pressure as imper- fectly plastic substances " *. Do not these observations manifest a decided leaning in the direction of the theory which, for several years, I have been advocatinfj' ? — viz. that slaty cleavage, instead of being simply the result of pressure, is the outcome of pressure exerted against preexisting divisional planes of jointing and bedding. Ilevcrtiug to the disturbances and accompanying igneous upbursts which have followed zones of jointing, the least reflection will make it clear that they would powerfully affect rocks possessed of this divisional structure, assumably com- pressing them at right angles to the course of an axis of disturbance, and bringing the joint-planes into immediate con- tact, thus developing slaty cleavage. The same agencies, besides producing enormous dislocations or faults, must have, by their transgressive action, flexured rocks into mountain chains and intervening valleys, also into parallelism with an axis of dis- turbance. Although agencies of the kind must have often obliterated jointing, I assume that cleavage-planes represent it — also that the strike of these planes indicates the course or direction pur- sued by the obliterated jointing, and consequently the system to which this divisional structure belonged. There are two systems of the kind — one Meridional, and the other equatorial — depending on the maximum frequency of the joints within certain points of the compass. The first, especially, * Quart, Joiim. Geol. Soc^ vol. xxxvi. pp. 72-74 (1880). no ROCK-METAMORPHISM. i i is div^isible into two sections — east-of -north, and west-of-north ; a tliird section, not so strongly developed, remains to be added, which, running north and south (that is, between the others), may be called medio-meridional. The equatorial system, in general not so well developed, may also be divided into two or more sections. As the earth's continents and great peninsulas (India &c.) have their chief coast-lines run- ning in directions corresponding to the two principal meridional sections (which is also the case with the main trends of the islands of the Paciific and other oceans), my contention is that their east coast-lino belongs to, and has been aligned by, the east-of-north meridional jointing — also that their west coast-line stands in corresponding relation to the west-of-north section. Thus I look upon the coast-lines of continents as a correlated phenomenon, taking these features to be defined by the edges of the great submarine plateaux which, stretching out for 200 miles or more, abruptly terminate in a succession of bench-like terraces, suddenly descending into the abysses of the oceans. Respecting another prominent feature of our continents, I offer the suggestion that the cast-of- north and the west-of-north sec- tions of meridional jointing have primarily marked out the sides cf the triar gle under the form of which these great land-masses are for the nost part presented ; while the base of the triangle is ascribed to equatorial jointing. But as it is not yet clear to me why the base of the triangle faces the north and its apex points to the south, I am inclined to think the solution lies in the fact that the greatest elevated land-masses characterize the northern hemisphere and equatorial regionc — a disposition which would cause a greater width of elevated land to lie within the basal area c^ ihe triangle than at the apex. This last point requires to be conssidered in connexion with the theory originally advanced by Dann"*^, that the earth's con- ^i^ents have always been continents, or, as I prefer to put it, that the present continents, in the main, have been from the earliest geological periods greatly elevated regions separated by enonnously deep depressions. Dana, however, contends that the great land-features of the globe have been produced by rej^onal up-bendings and down-bendings of its crust, the former having given rise to continental masses, and the latter "jo vaet ocean-basins ; whereas, although accepting the pre- * 'American Journal of Science,' 184G, and 'Manual of Geology.' 11': « SUPPLEMENTARY NOTE A. Ill nth. ion- it, Ithe by that by Ithe tter ire- Cambrian antiquity of the main surface-features of the earth's crust, it is my opinion that our continental coast-lines are in correlation with enormous faults, which have thrown down the rocks on one side of a dislocation thousands of feet below their corresponding masses on the other side, and, furthermore, that the general direction of any given continental coast-line has been determined by some system or section of jointing. In contending that jointing, slaty cleavage, great lines of faulting, continental coast-lines, and mountain- chains are cor- relative phenomena, I feel myself powerfully sustained, not only by the parallelism between the United-States coast and the Appalachian ridges, but equally by the corresponding parallelism of th-^ enormous faults (some with a downthrow of thousands of feet) which characterize this mountain-system. One of the faults is known to stretch from Quebec to New Jersey ! The disturbances which developed the " great feature-lines '' of our globe seem to have Lejn in operation in pre-Cambrian periods. Evidences have been discovered in the Wahsatch range (Rocky Mountains), by Clarence King, of an elevated mass, defined in one tract by a nearly vertical ciiff, which, with an altitude of 30,000 feet, was presumably in existence before the earliest palajozoic deposits were formed ; and there are the strongest evidences for the conclusion that, before the adjacent Cambrian rocks were deposited, the Archseans of North Americtt had been violently flexured, and thrown up into ridges — belong- ing to two divergent systems conformable with the zones of weakness '.vhich determined the east-of-north and the west-of- north outlines of this great continent ; the ridges forming in its central region a mountain-mass in pre-Cambrian times. The agent which gave an east-of-north trend to the west coast of Europe similarly affected much of the north \v(>Ht coast ol Africa : seemingly it struck obliquely uoioa^ the equatorial section of the Atlantic, reappearing at Cape St. Roquc, and proceeding onward along the mountainous soa-board of Brazil to the La Plata. Enormous as undoubtedly is this extent of coast-line formation, it is surpassed by what is presented on the west coast of the two Americas and the east coast of Asia : obviously the former, with its parallel mountain-ranges, is in genetic relation with the west-of-north and median sections of meridional jointing, and the latter with the east-of-north section. Attention may next be directed to the great inland ranges 112 ROCK-METAMORPHISM. I '' constituting the Alps and the Himalayas. Both mountain- masses have been more or less aft'eeted by forces exerted in direc- tions corresponding with the two principal sections of meridional jointing; but in both eases the phenomenon has been greatly swaj'^ed by movements presumably acting under the influence of the equatorial system. The disturbances which developed High Asia — a viist conti- nental mass within a continent stretching from India to the tundras of the Taimyr peninsula in Asiatic Siberia — liave ridged it up transversely into mountain-chains, Avith intervening desert platforms. Its southern extremity is formed by the Hi- malayan and other ridges, whose general level (20,000 feet or more in altitude) culminates in still loftier peaks, some not far short of 30,000 fee All the transverse ridges, in a great (or the middle) portion of their length, have an east-and-wcst course. The development of High Asia is a vastly complex phe- nomenon, presumably resulting from disturbances which have been directed along different zones of Aveakness. The zone in correlation with equatorial jointing seems to have been the mecUum hrough which the transverse ridges and their respective igneous axis were upheaved ; wliile those referable to the two principal sections of meridional jointing may have similarly influenced the terminations of the ridges on both sides of this huge plateau, especially in the region east of it, where mountain-ranges, coast-lines, and off- lying islands all coincide in their strike with the east-of-north meridional jointing. The lofty parallel ridges east of Burmali, in being medio-meridional, are so far in conformity Avitli the last-mentioned features. This brief notice vill scarcely permit of any reference being made to the equatorial extensions from the Pamir through Western Asia, &e. The question next suggests itself, arising from a consideration of all the phenomena that have been noticed — If the great pre- Cambrian plateaux have always existed as masses, having an ele- vation far above the bottom of the great intervening depressions (ocean-basins), how have they become covered up with marine sediments thousands of feet in thickness, and representing suc- cessive geological periods ? In this connexion It may be argued that elevations of rock-masses ar(* of two kinds ; — one due to stratal distu'^bances, which for the most part have been exerted m W i"] »P . iii lion )re- Icle- lons due suc- hied to fted SUPPLEMENTABY NOTE A. 113 horizontally, or approximately so, and the other to vertical movements extending over wide geographical areas. More than thirty years ago my attention was called to the latter class of movements by the beautifully developed series of terraces in the Burren of Clare, reaching to the height of nearly 1200 feet. This particular instance I have ascribed to a slow upheaval of the district above the sea, the surface of each terrace representing the bottom of a coast- shore — a plane of marine denudation — and an intermittent stoppage in the upheaval^. An examination which I made in 1870 of the terraces of Lochaber resulted in my becoming convinced that they are ancient sea-margins : 1495 feet is the height usually stated of these terraces; but I detected on the flanks of Ben Nevis, and of the opposite mountains, tao like features, which must reach to an altitude of between 2000 and 3000 feet. Besides the raised shell-beaches standing at a com- paratively low level on the coasts of Norway, terraces have been lately observed and described by Dayliins, which occur on the Dovrefjeld, at heights of from 2000 to 3100 feet. Darwin's account of the remarkable examples that occur in Patagonia, up to the height of 1300 feet, leaves no doubt on my mind that they have been formed by the a^ition of the sea. Hector has described vast terraces on both the eastern and Pacific slopes of the Rocky Mountains, stretching from the Athabasca river to Mexico, and rising one above another to heights ranging from 3500 to 4500 feet above the level of the sea. WeU marked parallel terraces are striking features in other parts of North America. A series of *' horizontal benches,^" twenty in number, deeply cut into the mountain-slopes, and situated at heights between 1100 and 2580 feet above the sea-level, extend over an area of 10,000 square miles both east and west of the Alleghanies of Pennsyl- vania, Virginia, and Maryland. As proper] v remarked by Prof. Stevenson, who has lately desoibed them, " they can be no other than sea-beaches marking stages in the withdrawal oi the ocean^'f. The late Daniel Sharpe made known the occurrence of lines of erosion on the inner and outer flanks of the Swiss Alps, at about 4300, 7500, and 9000 feet above the sea. And, to finish what could be made a much longer list, Rudolph Griesbach has described terraces in Natal lying at heights ' See 'The Geologist,' vol. vi. pp. 172, 173 (1863). t American Philosophical Society, August 16, J 879. 1 a-- f 114 ROCK-METAMORPHISM. ! - I \'i\ N '^ ^i' .1 I s'f > ; «^ if: I i of about 1000, 2300, and 5000 feet : it would also appear that these correspond with the main plateaus of Cape- colony. In short, it may be safely stated that marine terraces are to be seen in every region of the globe. In the deep valleys of the lofty southern buttress (Gangri range) of Thibet, terraces ascend to the height of 16,000 feet ; but as these may have been formed along the shores of elevated lakes, such as arc noAV in Ladak and adjacent countries, it would be nnsafe to classify them with the marine representatives that have been noticed. It may nevertheless be maintained that a number of geological evidences afforded by the area last noticed, combined with the proofs already brought forward, establish the conclusion that vertical movements of vast regional extent have affected not only High Asia but the entirety of the carth^s surface — elevating con- tinents, including mountains ami plateaus, at the same time uplifting the bed of the intervening oceans thousands of feet above their present level relatively to that of the sea, or plunging them as deeply in the opposite direction. Without denying that the level of the sea may have undergone great fluctuations at intervals during past geological time, caused by seonic flows and ebbs of the ocean, and that such changes may have participated, to an extent far beyond what physicists and hydrographers are at present disposed to admit, in developing phenomena which, for convenience' sake, I have collectively ascribed to vertical movements of the earth's crust — or without offx3ring any opinion respecting the hypotheses suggested by Babbage, Herschel, and others as to the cause of phenomena of elevation and subsidence — it does not appear improbable that cyclical or periodically recurrent vertical movements, each one representing a va^t chronological term, have by slow degrees alternately elevated and depressed opposite areas, corresponding in extent with a continental or even a hemispherical division of the globe. To illustrate this view, let it be assumed that one of oUr con» tinents, having attained its maximum elevation, is next to undergo subsidence. During this elevated period the land- surfaces of moderate height would be in what may be termed the first stage of depositional action, viz. the formation of subaerial, freshwater, and estuarine deposits ; in the second stage the same Bi. I one jgrees iding Iriaion con- it to thc irial, ■same SUPPLEMENTARY NOTE A. 115 areas would be subjected to marine actions, producing littoral and deepish-Avater conglomeratic, arenaceous, argillaceous, and cal- careous beds ; in the third stage, in which maximum depth had been reached, they would be under pelagic conditions, developing limestones, argillytes, and siliceous rocks. Next, elevation having again come on, the fourth stage would be a repetition of the second, yielding comparatively shallow-water marine de- posits ; and this would terminate by passing into the fifth stage, which corresponds to the first one. Thus would our continents, notwithstanding their being at present at an average height of a few thousand feet above the sea-level, become overlaid in every systemal period with vast deposits of all kinds — those of any given stage representing one of the formations (assumably five) which constitute a geological rock-system, and, moreover, the whole agreeing with the formations of a system in their suc- cessive order of superposition. A few points may be briefly added. It is not assumed that all such vertical movements have proceeded in the invariable course and to the extent, vertical or areal, above illustrated, or that they were unaccompanied by minor ups and downs. The region opposite to the one given as an illustration would be undergoing a cycle of counter vertical movements. As to the deposits which were thrown down over the abysses of the oceans (Atlantic and Pacific) when the continents were under pelagic conditions, it is admitted they involve some questions difficult to answer, whether considered in connexion with Dana's hypo- thesis, or the one just stated. Obviously great recurrent climatal changes would result from these elevations and depressions — severe glacial conditions accompanying the one, and the replacement of the latter by genial ameliorations arising from the other. The consideration of these points gives rise to the question, often debated, How has it happened that after the Pliocene period climatal conditions prevailed which converted a .,'reat portion of Europe and North Americn (there arc grounds for excepting Northern Asia into ice-covered regions, and that during the Miocene (or probably some portion of the Plifx 2nej period areas lying within from 10° to 20° of the North Pole have enjoyed, as it appears to some geologists, a climate a] > oaching in genialness that of the south of Europe at the pn cut day ? 116 ROCR-METAMORPHISM. I f Influenced by objections to all the hypotheses that have been oflferod in explanation of these climatal interchanges, I find a much more tenable one in that which attributes them mainly to the aforementioned vertical movements. Confining myself to the climatal conditions whii charac- terized Grinnell Land, Spitzbergen, and other Art.io areas during the Miocene period, as indicated by their plant-remains, T make the suggestion that these and adjacent areas stood at a somewhat lower level relatively to the sea than at present, and formed an archipelago, freely permitting currents with a tem- perature slightly more elevated than that of the gulf-stream where it now strikes the west coast of Ireland to bathe the coasts of its islands. Climatal amenities now prevail in Arctic Scandinavia, the Kara Sea, and on the western border of the Taimyr peninsula in Asiatic Russia : the last place, the most northern continental land of the globe, now supports an exuberant forest vegetation in a much higher parallel than anywhere else within the Arctic circle, and only about 16° or 17° short of the North Pole — the fact being seemingly due to the presence of warm water, carried by ocean-currents and by rivers (as the Yenissei) from the south. Boreal Siberia, in direct communication with southern lakes, inland seas, and ocean- streams charged with warm water, and in the condition of an archipelago, — why may not its great forest belt be extended up to Spitzbergen and Franz- Joseph Land — to parallels corresponding with those in Grinnell Land, which formerly supported the growth of a vegetation approximately similar in some respects to that now characteristic of Northern Italy and the Southern States of North America ? As to the long winter-night of darkness and the long summer- day of sunlight, I feel satisfied from adducible evidences that, other things being favourable, such conditions would rather favour than impede vegetable growth. Areas favourably situated as to shelter, meteoric influences, soil, proximity to warm currents, &c., and especially where a thick covering of snow prevailed during the severe months of winter, would, in my opinion, become genial oases supporting an exceptional vegetation : such I look upon were the places in Grinnell Land and Spitzbergen where, during the Miocene or early portion of the Pliocene period, flourished guelder roses, water- f|i SUPPI^EMENTA.HY NOTE A. ur ler- that, Ither |ably lity |ring mid, lonal mell [arly iter- iilies, sequoias, swamp-cypresses {Taxodium), &c. of extinct species, and varieties of known species now living in temperate latitudes, and doubtless acclimated to arctic conditions. The adaptive constitution of plants has not been sufficiently considered in connexion with this ([uestion. I shall conclude with a few brief remarks on linear igneous disturbances. Admitting the existence of a number which may be included in the equatorial system of jointing, disturbances of the kind are for the most part limited to the meridional zones of weakness. As is well known, a most important scries of volcanoes characterizes the western borders of the two Americas ; and a similar series lies off the east coasts of Asia, belonging, in my opinion, one to the west-of-north and the other to the east-of-north section of meridional jointing : both series become united in Behring^s Sea. Other writers, by connecting the equa- torial series of volcanoes north of Australia with the above two, have constructed a " circle of fire ;" but Avith far too limited a range. The two meridional series (by pursuing a direct course, so as to embrace the Cocos Islands, St. Paul's, Kerguelen's Land, Enderby's Land, thence curving to Trinity Land, passing on to the South Shetlands, and through Fuegia into the Patagonian Andes) form but one a great volcanic girdle, which may be said to stretch without interruption round the world, traversing the Arctic regions a few degrees east of the North Pole, and inter- secting the Antarctic circle at a corresponding distance west of the South Pole — thus dividing the crust of the globe along its greatest zones of weakness into two nearly equal halves, and at the same time separating its superficies into a water- and a land- hemisphere. As to reflections which may naturally arise in connexion with the last subject, I avow myself to be, scientifically, too much of a teleoptimist, too extravagant a timist, and too little of a catastrophist to entertain any that involve serious or disquieting apprehensions. mmmm [I .= f'r :' 118 ROQK-MflTAMORPHISI^, SUPPLEMENTARY NOTH B. ON THE CRYSTALLINE BODIES OF THE SUNDERLAND PERMIAN MAGNESIAN LIMESTONE. ''^■^ .i Fig. 2. Fig. 1 represents a section of Permian limestone, exposed in a railway-cutting between Sunderland and Ryhope, as displayed when I made a sketch of it about the year 184G. The beds exhibit well-developed jointing, running in two directions. The front or fa':!e of the section is a joint-plane (as is also the one further in) belonging apparently to the equatorial system ; the oblique lines, also the end-surface parallel with them, belong to the west-of-north meridional set. The horizontal lines and the corresponding surface at top represent bedding. The interest which attaches to this section is the fact, well displayed, that the coralloidal bodies spring from the planes of both bedding SUPPLEMENTARY NOTE B. 119 a red ids phe n\e We I to ihe 3St iat and jointing. I have repeatedly observed the same thing at other places in the neighbourhood of Sunderland; on one occasion a coralloid with a stem as thick as a man's arm, came under my notice. It is also a common occurrence, where semi- globular bodies are developed, for them to be integrally con- nected with the surface-portion (usually upp >r) of a bed. Fig. 2 represents a portion (about a foot square) taken from a bed at Building Hill. The oblique lines represent west-of- north joints, and the horizontal bounding lines bedding-planes. The specimen, with several others of the kind, was collected about the year 1839, on an occasion when the quarrymen had exposed a singularly beautiful development of such forms. In this example, as in the section fig. 1, the coralloids branch off from the planes of bedding and jointing j but one of its features is worth special notice : the coralloids, according to a note I made at the time, are best developed where branching from the west bounding-plane of the meridional joints, Thesr examples are amply sufficient to disprove the idea that they were formed at the same time as that in which the limestone Avas deposited j also that, howsoever they may have originated, the agent which produced them must have penetrated the partings of both jointing and bedding. It cannot be too strongly impressed on the mind of the reader that the coralloids, also the other configuration to which Dr. Ramsay has referred, are more or less crystalline internally, and consist of carbonate of lime, adding a few per cent, of carbonate of magnesia ; while their matrix, or the body of the rock, is structureless and essentially dolomite. 120 ROCK-METAMOBPHISM. u m 11 lli -ill 1 1 if ^ m III: SUPPLEMENTARY NOTE C. CERTAIN LIMESTONES ARE OF MECHANICAL ORIGIN. It is well known that Dr. S terry Hunt, in advocating the purely chemical origin of limestones, places himself in op- position to the opinion generally prevailing on this subject, viz. that while some rocks of the kind are chemical products, such as freshwater and marine travertines, by far the greater portion are of organic origin, that is, the skeletal exuviae of shells, corals, foraminifers, and other animals. Excluding the methylosed crystalline limestones, I quite agree with this view ; but I have now to bring under notice another class of calcareous deposits, whose origin, it is assumable, was altogether different ; though they may have been primarily of organic, chemical, or methylotic development. The calcareous nature of the erratic drift, so well developed toear the " Citie " of Galway (to which reference has been pre- viously made, footnote, p. 93), can only be due to this deposit having been derived from the Carboniferous limestone of the surrounding district by the abrading action of glaciers. From what has lately come under my notice I see no reason why certain calcareous deposits, obviously of littoral origin, cannot be the debris of mechanically abraded limestones. Lately, availing myself of an occasion when Lough Corrib was in a muddy condition, caused by heavy rains, I put aside a couple of quarts of the water to stand for a few days. Testing the sediment which had settled at the bottom of the vessel with hydrochloric acid, a brisk effervescence took place, denoting it to contain a notable quantity of carbonate of lime. The remaining clear water, on being tested with oxalate of ammonia, exhibited decided evidence of its containing bicarbonate of lime in solution. These facts prove that the water of rivers in limestone districts contains calcareous matter both mechanically m SUPPLKMENTARY NOTE C. 121 led »re- isit Ithe fom rhy Inot a of Ithe ^ith it lie lia, ime in lUy suspendcd and in a chemically dissolved state ; so that, while the latter may he carried out into the open sea, to he appro- priated by shells, corals, &c. for their skeletons, and the dtl)ris of these converted into limestones, the former may he mechani- cally deposited in estuaries and along shores. I have often thought over the fact that many limestones are so greatly deficient of calcareous fossils as to render their organic origin doubtful : the lithographic limestones of liavaria are cases in point, also the Permian marl-slates of Durham and (ierniany. I am therefore now strongly inclined to assume that these and other calcareous deposits are of mechanical origin. When writing the footnote above referred to, I thought it not improbable that the doloniitic conglomerate of the Bristol district was a Triassic glacial deposit, its paste having been derived from a Permian magnesiun limestone now entirely removed. But from information I have liberally received from Prof. Sollas (whose short note in the ' Geological Magazine ' of Febmary last led me to put a few questions to him) I feel per- suaded his opinion i' correct, that both the paste and the pebbles it contains have been dulcmitized since they were accumulated, and that the paste had not bec:i derived from a Permian limestone. Prof. Sollas and Mr. Margetson, I understand, are preparing for publication an account of the Bristol rocks. v>, "iu .o^,\^ IMAGE EVALUATION TEST TARGET (MT-3) !.0 i.l 2.0 HI 1^ If 1.8 1.25 1.4 1 1.6 — il = M 6" .._.. _^ .J> «55% A # // ■^Jhr" > "^v^. ^J^'. ^^ Hiotographic Sciences Corporation 23 WEST MAIN STREET WRbSTER.N.Y. 14580 (716) 873-4503 <. m '4^ & W ■I* If >i ) DESCRIPTION OF THE PLATES. PLATE I. Fig-. 1. Chrysotile interlamellated with sei pontine. Colafirtli, ohetland. Fig. 2. Lamellated ophite ("iJocoora Ommfenm'"), consisting of layers of serpentine and calcite in parallelism with one another. Canada. Fig. 3. Peridote (olivine) enclosing fibrous or striated laiuina\ Elfdalen in Ualeoarlia. Fig. 4. Feldspar enclosing fibrous or striated lamina!. Fig. 5. Graphic granite, consisting of layers of feldspar (n) alternating with others composed of quartz (i). The former are transversely intersected by striated fibrous and striped laniino). Harris, Hebrides.— Specimens of tiie kind have been taken for a fossil related to " Euzoon Canadense " ! Fig. 0. Specimen in which there is a definite and parallel alternation of reddisli quartz and red feldspar, rivalling that of the lamellated variety of ^'' Euzoon Canadcnse,'' Astnican. Fig. 7. Transverse section of a crystal, presunuxl, from its cleavage, to be augite ; an optical examination, however, shows that its substance is jieri- dotized. Vesuvius. PLATE IL Fig. 1. Chrysotile changing into^ 'the acicular varieties ; also the sam(> rejilaced by calcite («) : the vai-iety c answers to the " proper wall," and the calcite to the " intermediate skeleton " of '* Eozoon Canudeme.'" Keiclienatein. Fig. 2. Portion of specimen of" ^oroojj Canadensey Imyor of clirysotile («) in parallel alternation with serpentine (6) on one side and calcite (c) on tiie other. In the latter case the fibres at tlie upper surface of the layer of chry- sotile are broken and pressed obliquely out of position, thereby forming a thin lamina ; these fibres are more or less separated by films of calcite iii- tegi-ally connected with the overlying calcitic layer. Thus the lamina corre- sponds to the " proper wall," and the latter part to the "intermediate skeleton." (N.B. Tlie layers of chrysotile and serpentine are in such position to each other as to ]»rove tlieir genetic correlation : it is also noteworthy that on the margin where the chrysotile is in inunediate contact with the serpentine there is no fibrous lamina with its fibre? separated by calcitic interpolations.) Canada. ■MM if 12 A DESCRIPTION OF THE PLATES. Pl.ATK n. (continued). Fig. .'}. Portion of a specimen of " Eozoon Canadense" showing a fissure or erack (several more are present in the specimen, see ' Proc. lioy. Irish Acad, vol. X. ]»1. xli. fig. 4) obliquely intersecting a lobiilated layer of serpentine (" chamber-Cc'ist ;'' other layers of the Icintl are similarly intersected). This fissure, ns in other cases, is cliaracterized by "intermediate skeleton " (<■?), bounded at top and bottom by " proper wall " ('/). A layer of chrysotile (c), in its incipient stage of development (see PI. IX. fig. !,«), lies above and in parallelism with the fissure, proving tlie genetic correlation of the two parts. Observe that the Hbres (jf tiie chrysotile in the fissure pass cimtiuuou.-.ly lengthwise into the separated aci(.'ula). PLATE III. Fig. 1. Decalcified specimen, magnified, of saccliaroid marbh? (hemitiirene), containing crystalloids of malacolite (a) decreted or etched into brandling configurations («*), identical witii "canal .system" of '^JEozoon;"' also crystal- loids of pyrosclerite(i), someof wliich have tlieir surfaces coated witli acieuhe. Mt. St. Philippe, near Mario aux Mines, "N'osges. Figs. 2 & li. Cry.stalloids, highly magnified, of pyrosclerite invested with a fibrous lamina (6), portions of whicli are pectinated (d), as in the variety of chrysotile corresponding with the "proper wall" of ^^ Eozoon,''' Mt. St. Philippe, Vosges. Fig. 4. Section of a ci'ystal of (Pjperidole (polarized), associated with ser- pentine. ^^ Eozoon CanadcnsL','" Canada. Fig. .5. Section of a crystal of (?) peiidote (polarized), divided by laminne of calcite corresponding with tlie cleavage-divisions. Tlie calcite is obviously a replacement product (pseudomorphism). Same as section fig. 4. Canada. I'LATE IV. Ground-plan of a trap-dyke (a) intersecting gneiss (b) in a cove (A) at Glassillauu (B), on the north shore of Cleggau Bay, Connemara. Thi; gneiss is converted into hemithrene (c) in places on both sides of, and adjacent to, the dyke. The dyke is calcitized. PLATE V. Natural vertical section of the last case (letters the same), showing gnei.ss converted into hemitlirene by action of trap-dyke. PLATE VI. iMg. 1. Vertical section (Ix'ing face of a quan-y at Mt, St. Philippe) of gneiss (red colour) intersected by irregular masses nf hemithrene (green). DESCRIPTION OF THE PLATES. 125 ng a fissure ov '. Irish Acad. of serpontino jocted). This skeleton" (a), chrysotih; {<■), aljovo and in the two parts. continuously (xivcn as nfTordiiig evidences that the f:,neiss has been methyloseil into the lieniitlirene (pp. 51, 52). The specimens represented under ligs. 1, 2, and iJ, PI. III., are from this quarry. Fig. 2. " Eozonn Cunack'nge." A layer of chrysotile in its ditl'eront stages of development: — «, incipient stage; h, typical chrysotile; c, closely acicular (" velvet pile '") condition of '' proper wall." Canada. Fig. o. " Uozoon Caiutdfuse^ " Proptir wall " in two separate lamin.Te, and in different stages of modification. One of the laminre is pectinated, and thus assumes the form typical of the "proper wall." Canada. PIATE VII. Specimen of a serpentine rock, psoudomorphic after tremolite (uatuial size). Cannavor, Lough Corrib, Connaught. 'heniithrenc)* ito branching " also crystal- . with aeiculie. PLATE VIII. Specimen of tremolite (natural size), for comparison with that repre.sented in Plate VII., the crystalline structure of both being identical. St. Gothard. ivested with a the variety of un." Mt. St. ated with .ler- ed by laminne e is obviously 4. Canada. covo (A) at The gneiss adjacent to, lowing gneiss Philippe) of reue (green). \ PLATE IX. {Frontispiece.) Fig. 1. Diagrammatic sketch, showing serpentine (a) changing into chry- sotile (b) ; also the latter in its various modifications or stages of development. Under a the chrysotile is in the (first) incipient stage, being striated ser- pentine (that is, the variety marked with separated thread-like lines or cuts) ; b, (second) fibrous stage, which is typical chrysotile ; c, (third) close-acicular stage, in which the fibres are changed into definite acicuhne ; d, (fourth) pecti- nat(;d stage, in which the aciculte are separated by films of calcite — thus con- stituting the " proper wall " of " IJoznon Canadense.''^ Fig. 2. Portion, highly magnified, of an accredited specimen of " Euzoon Cmiddense,^' showing the diilerent features of the presumed fossil originating from cheuiical and structural changes in the minerals entering into its composition (pp. 18, 19). The layer a consists of ordinary serpentine changed into the striated variety or incipient chrysotile (a) (other layers consist entirely of structureless serpentine). At b is chrysotile in its tj-pical condition. This layer at top, under c, is changed into the close-acicular variety, and under d into the sc^parate-acicular or pectinated variety, the aciculae in which are separated by calcite : it is thus converted into the " proper wall " of " Eozoon Cn7iadense." The acicuhc i'l the last stage are considered to be " casts of tubuli," such as characterize tiie nunimuline layer (" proper wall ') of certain recent foraminifers. T'/'o letter c denotes llocculite, a white (floc- culent) variety of sei'peutine, whicii usually occurs as layers, or clotules : it is often decreted or etched oat by solvent action into arborescent configurations (c*), forming the "canal system " of " Eozoon." (N.B. The la.st feature is not in its original place : it occurs in another part of the specimen ; but its relations to other eozoonal features are ^oncctly represented.) The layers d (" in- mmmmm I ■ \:u\ DESCRIPTION OK THK PLATES. Platr IX. {(otitiimed). termediate skeleton ") are in calcite, resulting directlj frxco:t .'J'ay/.'ii.U'.:\^t' " n '■I ^ i II \i I ' ■1 f ! I ? I 1 1 i ! ( , I pim K.ux V/K JiHuna!'!. iitn ffl T-*^ ^n in in m" m\ W ' ii 1 1 ffflr i 1 H, ■ i m3 iH i f 2 'iik^^di^. ::>^^4fc.^.- : ./ .Al5^'*^:^^-k/Jiii£k>!^ ,j,m.l,'".8'il'IJJ'''»*r-r*" ' . ^r.i4 I ;■.' i:..» GNEISS IRED) CHANGED INTO HEMITHRENE iGREEN) MONT S^ PHILIPPE VOSGES h: i m^ 'If: k Sei^pent.iiie v.^eudomorpnio aii.er i r^^iriciliL.e i.iyj.P'':] uii.iV/^y. m ' I' v> I V!!I TREMOLITE. S^ GOTHARD. Kanha pt imp INDEX. Aby88es of the ocean, deposits \n, 75, 99, 115. Acadian rocks, 84, 88. Acclimatization of plants, 117. Achiardi, A. d', on argillaceous schist changed into serpentine, 44, 97. Agalmatolvtes, 2, 43. Aker (Finland), heniithrenes &c. of, xvi, 23, 40, 57, 63, 87. Alabaster, a methylosed product, 43. Alberese (Cretaceous limestone) ser- pentinized hy euphotide, 97. Alkaline salts in rocks, 30, 31. , action of, 35, 79. Alleghanies, terraces of the, 113. Allomorphs of serpentine, 6, 19. Allport, Samuel, on peridote &c., 34, 69, 70, 71. Alps, ranges of the, 111. , terraces of the, 113. Aluminate of magnesia. See Spinel. Aluminous serpentine minerals, 5. America, mountain-ranges of, 111, 113. , terraces of North, 113, 116. — — , volcanoes of, 117. Amianthus with fibres of calcite, 16. Amity (New Jersey), hemithrene of, xxiV, xxviii, lii, 10, 23, 56, 57. Ammonites in metamorphics of Switzerland, 32. Ammonitidae in Austria and Northern India, 104. Andalusite ferruginated into stauro- lite, 23. Andes. See Patagonian. Anhydrous magnesio-siliceous mi- nerals, 7. minerals of metamorphic rocks, 35. ' Annales des Mines,' 28, 35. Antarctic Circle intersected by the earth's volcanic girdle, 117. Anthophyllite, 7. Antigorite, ferruginous serpentine, 5. Aphrodite asiliceous serpentine, 5, 44. Apjohn, Dr. J., on origin of dolomite, 91, 94, 95. Appalachian ridges. 111. Aquosity of rocks, 35. Aragonite(l') replacing chrysotile, 21. Archsean " crystalline limestones," 72-82. ophites. See Serpentine rocks. rocks, 29, 32, 33, 34, 66, 72-83, 86, 87, 88, 91, 9G, 111. ArcheBocyathus atlanttcus, 85. ' Archiv fiir Mineralogie,' 32. Arctic regions under climaial ameni- ties, 116. intersected by the earth's volcanic girdle, 117, Ardtrea magnesian limestone, Per- mian, 102. Argile magn^sienne, 2, 29, 44, Argillaceous limestone converted into rottenstone, 43. Argillytes, 34, 43, 44, 86. Arkoses, 31. Asbestiform serpentine. See Chry- sotile. M I 128 INDEX. Asbestos an nlloraorph of liorn- blendt!, 14. Aaia, Iligli, mountain-rangea of, 112. Asiatic llussia, climatal ameaitics of, lie. Atacama, meteoric aiuvgdaloids of, 03. Athabasca river, terraced of, 1 ]'■]. Atlantic Ocean, 115. See Abysses. Aiierbach, calcitic dvke of, 51. Au-rite, 1 1 , 24, ->('., •}'.), .37, 58, (>;{, 00, 07, 08, 70, 71,72, 7S>, 81,89. Aiigitic rocks. S^'e Doleritoa. Austrian Alps, Annnonitida> of, 104. Auvergne, peridott; in lava of, (}'■>, Axes of stratal disturbance in rela- tion to joint ing &e., 100. Azoic rocKs, 21). B. ]5abbage, Charles, on vertical move- ments of the earth's crust, 1 14. JJacculites assc ciated with Tertiary plants in Ilocky Mountains, 102. Ikily, \V. llellier, ojjposes "Ji'ns«o«," xiii. Bala limestone, 84. Ballinahinch (Connemara) crystal- line limestone, 00. Baltimorite, 5, 27. Baretti, M., on the mntamorpbics of the Central Alps, .'U. Barker, Arthur E., xxxi. Sec Max Schultze. Barna Oran (Connemara), 90. Bastite, 5, 0. Beaches, ancient sea-. See Terraces. Beaumont, Elie de, on metamorphics of France and Switzerland, .'JI. Beauty Hill (Scotland), lime and serpentine associated, 55. Bebring Sea, its volcanoes in the line of the earth's great volcanic girdle, 117. Belemnites in metamorpbics of tbe Mont-Cenis district, 32. Ben Nevis, terraces of, 113. Bigsby, Dr. Jolm J., on Canadian crystalline limestones, 73. Biharite, 5. Biotite, 7. Bischof, Gustav, vii, 24, 25, 20, 31, 32, 30, 37, 40, 44, 47, 54, 55, 02, 04-06, 70, 91. Blum, vii, xiv, 24, 37, 45. Bofin Tiough (Connomara), crystal- line limestone of, '.K). Boltonite, (51,0.3. Jionnard, M., on metamorpbics of France, 31. Bonney, Rev. I'rof., on aerpentino, peridote, kc, xliv, 1 1, 37, 40. , accepts " Euzoon,'' xliv. Bowenite, 5. Brackish lakes, 103, 104. Brazil, sea-board of, III. Jtreitbaupt, M., on serpentine and peridote, 37, (i2, (54. Bristol dolomitic conglomerate, 93, 121. British A.«rito of, 37, 40. Bunsen, his names " bydatothermic " and " pyrocaustic,"' 35. Bunter sandstone, 102. Burbank, L. S., at first accepts and next opposes " Eozoon" xxiv, , eozoonal limestones of Chelms- ford not true stratified deposits, xxix, xxxviii. Burgess (Canada); " Uozoon" from, XV, Ivii, 41. Burmah, mountain-ridges of, 112. Burren of Clare, terraces of, 113. Byera's Quarry (Durham), crystal- lized dolomite of, 94. C. Calcaire saccharoide. See Limestones. Calcareous drift of Oalway, 93, 120. dykes, or calcitic vein-like masses, 51-53, 50, 02, 04, 78, 79, 81. fossils, rarity of, in Cambrian rocks, 85. matter held in chemical and mechanical suspension in water of Lough Corrib, 120. INDEX. 129 crystal- [>llIC8 of rpentino, 40. tine and rate, 93, . X, xiii, 'op-water c systeni changed aniphibo- e " rocks, f, f}7, 40. thermic" :epts and cxiv. If Cliehns- deposits, \h" from, :)f, 112. ■113. , crystal- Imestones. 93, 120. veiu-lilie I, 78, 79, ^ambrian lical and water of Calcareous rocks. Sfe Limestones, Calci-feldspathic gneiss, 13. Calciferous rocks, 84, 88. Calci-granitoid >?nei»H, xlv. Calci-hornbleudic gneiss, xiii, xlvi, 14,7: •3. Calci-niicnschista, 2. Calciphyres of Alex. Bron3, 5/ , polarized, 17. Calcitizatiou of granite &c. near Galway, 27, 41. Calumet (Canada), " Uozouti'^ from the, ix. Camarophoria Kiiit/ii, 103. multiplicato , 103, Cambrian cru.staceaiis, 8o. limestones, their rarity, 87. organisms, 85. rocks, 83-89. Canadian Archajans. See Archtean rocks. Geological Survey, 29, 73, 70. group (? Upper Cambrian) of rocks, 85. * Canadian Naturalist,' 29, 48, Canadian ophites, 45, 57, kc. " Canal system." See " Eozoon Canadense.^' Cannaver Isle (Lough Corrib), ser- pentine after tremolite, 39, 40, 125. Cape Colony, terraces of, 114. Cape St. Roque, 111. Cape-Verd Isles, peridote of, 01. Caradoc limestones, 84. Carbonate of magnesia in I'ermian dolomite, 93, Carbonic acid or carbacid solutions, iheir action upon silacid rocks and mineral silicates, 25, 20,53, 79, 80. Carboniferous metamorphics, 32, 90, 94. system and its formations, 101, 102, 104, 108, Carmoney Hill (Antrim), doleritic . dyke of, 71. Carpenter, Dr. W. B., his attack on the authors, xiii. , on " Eozoon Canadense,^^ x, xi, xix, xxi, xxii, &c. Carpenter, Dr. W. B., virsm IL J. Carter, xxx, xxxi. vt'i'nm T, Mellard IJeade, xxvii. rcr/iitH Otto Hahii, xiii, versus Miibius. .Vry Corrigenda. , remarks on Max Schultze, xxxii. , on new Lurentian fossil in graphic granite, xl. -, " I'iiial Note on Eozooti Cana- dense" xxxiii. Carrarite (Carrara marble), 2, 32,82, 90, Carter, If. J., opposes "Eozoon,''' xxx, xxxi, xxxvii. Caspian Sea, 92, 99. Cassiterite, pseudomorph after feld- spar, 2-3. Central Italy, metamorphosed rocka of, .32. (.erolite, 5. Cevlon, " Eozoon " in, xxix, 23, 57, Chazy limestone, 85. Clichusford (Massachusetts) crystal- line lin)e>tones, ^'Eozoon " &c. in, xxiv, xxviii, xxLx, xxxviii. * Chemical and Geological Essays ' (Dr. Hunt), 29, 32, 33, 35, 44, ' Chemical and Physical Geology ' (Bischof), 24, 25, 20, 32, 48. Chemical clianges in minerals. See Pseudomorphism. deposits, 29, 75, 120, Chippal (Vosges), hemithrene of, 51, 53, f !hlorargillytea, 2, 43. Chlorite (see Corrigenda), 29, 50, 65. pseudomorphic after augite, II. schist 2 29, Chondrodite, 7"oi,"72, 79. Chonicrite an alumino-calcareous serpentine, 5. Chrysolite, 01. Chrysotile an allomorph of serpen- tine, 8, 19. , changes of, into " proper wall " of" Eozoon Canadense,'' xiv, xxxiii, xxxviii, xlv, li, 8, 9, 14-19,21,20, 125. from Reichenstein (Silesia), 15, 16, 123. -, Dr. Dawson on, xxxv, xxxvi, xxxvii, li. -, M. Delesse on, 15. « Circle of fire," 117. Clare (Burren), terraces of, 113. m2 i'i if 130 INDEX. ■If:: i Clay-Blate, 2, 32, (Ueavapre, ininural, xv, xvi, 12, 57, 1,5:1, 78, Hi, 124. Climatal aiiit'iiitieM, 11<). chanj;re»,great rt'ciirrent,! 15,1 10. Clyde distiict, peridotic trap rocks of the, 70. Coal a metLylost'd product, 4.3. CoiLSt-lines. iit'e Continents. Cocclii, M., on foHsils of the crystal- line liiiicstone of Carrara, .'{2. Coccolitic minerals and marbles, 7, 48, 55. See Crystalloids. Cocos Isles in relation to the earth's volcanic f^irdle, 1 17. Coelenterates of the Cambrian system, 85. Colafirth chrysotile, 8. Colloidal serpentine, 0. Conligurations, mineral. See " Hu- zoon" " canal system." Coniston limestones, 84. Connemara, " Eozoon " in ophites of, xi, xxi, XXV, 87. ophites. See Ophites. Continents, their coast-lines and tri- angular form, 110, 111. Conzocoli (Tyrol), junction of diorite and dolomitic limestone, 41. Co(juand, Henri, fossils in crystalline limestone of Carrara, 32. Coralloirts of magnesian limestone of Sunderland, xviii, xix, Ivi, 03, 04, 105, 100, 118, 119. Cordier, M., 13. Cork Coimty, jointed limestone of, 108. Cornwall , serpentinyte of. See Lizard. Corrosion of minerals. See Crystal- loids and "^'ozoon ''" canal system ." Corundophyllite, 5. Cotta, Bemhard von, on pseudomor- phism, 37. ■ , on crystalline limestone, 89. Coulonge river (Ottawa), Archtean conglomerates of, 77, 87. Credner, H., advocates '* Eozoon" xxii. Cretaceous system, pelagic formations of, 102. Croix-aux-Mines (Vosges), metamor- phics of, 51. Crouza stone, 21. Crustaceans, Cambrian, 85. Crystalline limestones. See Lime- stones otic/ Ilemithrencs. Crystalloids, xv-xvii, xx, xxvi, xxviii, Iv, Ivii, 21, 22. 41, 50, 55-50,79,83,84.80, 124. Cumberland, Permians of, 104. Cunniughauie on serpentine, 37. Cyclical (regional) vertical move- ments of the earth's crust, 100- 102, 104, 113-115. D. Dakyns, J. R., on terraces on the Dovrefj.'ld, 113. Dalmein (Scotland), calcareous mar- ble of, 89. Damon, Robert, specimens of " Eo~ zooH " received from, xv, xxxvii, 18. Damour, M. A., on " tremolite " &c., 40, 01. Damourite an alkaliferous mineral,31. Dana, Prof. James, on the West- chester crystalline limestones, 33, 42,69. ^ , on the earth's continents, 110, 115. -, on loganite, xv. D'ArgenvilTe, priority of his name peridote, 61. Darwin, Charles, on terraces of Pata- gonia, 113. Daubr^e. Prof. A., on rock-jointing, 107, 108. , on action of alkaline waters, 35. ' Dawn of Life ' (Dr. J. W. Dawson), xxxviii. Dawson, Dr. J. W., on " Eozoon Ca- nadense" x, xi, xxi, xxiv, xxvii, xxviii, xxxiii, &c., 13, 18. , on "imitative forms of Eo- zoon" xlv. , on pseudomorphism, xxxv, xxxvi, xhx, 1, li, 19. -, on chrysotile and serpentine, xxxv, xxxvi, xliii, li. — versus Mobius, xlvii. — versus Otto Halin, xliii. — versus T. Mellard Reade, xxvii. — versus Carter, xxxvii, xxxviii. versus Koemer, liii. Decalcification, its effect on a dolo- mitic limestone, 94, 95. De la Beche on ancient crystalline rocks, 29, Delabole slates, their cleavage corre- See Lime- es. XX, xxvi, 2->. 41, CO, 124. nf, 104. tine, .'J7. •tical move- crust, 100- ncos on the careoiis mar- Bna of " Eo- XV, xxxvii, molite " &c., 8 mineral ,31. the West- lestones, 38, tinents, 110, f his name aces of Pata- 3ck-jointing, e waters, 35. rV. Dawson), Eozoon Ca- xxiv, xxvii, 18. •ma of Eo- ism, XXXV, serpentine, i. diii. eade, xxvii. ii, xxxviii. on a dolo- crystalline ivage corre- INDEX. 131 nponds with depositional partings, 107. Delesse, M. ^ "^ille, on pseudomor- phism, 23. , on luotamorphism, 28. , on change in chrysotile, 15. , on slatj changed into schistose serpentine, 44. , on hemithrenes of the Vosges, 52, 53. Deraagnesiation of Durham Permian dolomite, 04. Dendritic shapes assumed by minerals. See Flocculite, Crystalloids, &c. Derryclare Lough(Connemara), crys- talloids in limestone of, 40. Deweylite, 5, 6. Diaclasite, 7, 01. Diallage rock, 37, 38, 64. Diamond, 7. Dimetian rocks, impure limestone bands in, 83. Diopside, 35. Diorites and their methylosis, 2, 20, 27, 37, 38, 41, 48, 64, 04. Dolerites and their roethylosis, 2, 37, 38, 48, 4i), 51, 04, 71. Doleritic dyke at Cleggan. See Cleg- gan dyke. Dolomites and dolomitization, 2, 3, 32, 41, 43, 84, 91-95, 102-100, 118, 119, 121. Dolomitic conglomerate near Bristol, 93, 121. Donegal, crystalline limestones of, 14, 90. Dovrefjeld, terraces of the, 113. Duncan, Dr. P. Martin, adopts " Eozoon,^' xxii. Dunglow. See Donegal. Dunyte a peridotic rock, 2, 02. Durham coal-measures, their place in tlie Carboniferous system, 101. magnesian limestone, 91-95, 102-100, 118, 119. and marl slate, their flace in the Permian system, 92, 02, 121. Dumes (Sutherlandshire) limestone, 33, 84, 89. Dwarfed organisms of the Permian period, 103. Dyke, doleritic. See Cleggan dyke. Dyke-like masses of crystalline lime- stone, xxviii, xxix, 51, 52, 63, 78-82. Dyke-like masses of granite. See Urauitic veins. E. Earth-crust movements. iS?^ Cyclical and Stratal. Echinoderms, Cambrian, 85. ' Edinburgh New Philosophical Jour- nal,' 25. Elevations and subsidences. See Cy- clical and Stratal. Elfdalen (Delecarlia), peridote of, 12, 02, 03. Emmons on "primary limestones" (hemithrenes), 5.3, 88. on crystalloids, 60. Enderby's Land in relation to the earth s volcanic ^rdle, 117. Engadine. See Kalkgebirg. Enstatite, 7, 11, 37, 01. Eocene deposits of Central Italy con- verted into op'tites, 97. "Eozoic" rocks, 29,32. ^* Eozoon" preserved in loganite, x, XV, xxiv, Ivii, 41. ^'Eozoon Canadense," v, vi, vii, and Introduction generally, 87. , " acervuline" and " lami- nated " varieties, 10, 1 1 , 13, 14. , " canal system," xviii, Iv, 10,19,20,22,57,84. , "chamber-casts," 50, 04,79. -, " intermediate skeleton," 10,13,21,22. -, ''properwall,"9,17,18,70. , summary of evidences and arguments against, liv, Iv, Ivi. Eozoonal features in chrysotile rock of Reichenstein (Silesia), 15, 10. in hemithrene of Aker,23, 87. xxiv, 57. - Amity (New Jersey), - Ceylon, xxix, 57. Chelmsford (Massa- chusetts), xxiv, &c. Connemara, xi. Sec. ■ Isle of Skye, xxv'iii &c. Mont St. Philippe (Vosges), xlvii, 22. Switzerland, 31 . present in intrusive ser- pentine rock of the Lizard, xliii. Epidote,2e, 29, 51,06. Equatorial. See Jointing. Eribol, Loch, See Dumes limestone. 132 INDEX. Easex Co. (New York) limestone. (S'ee Westchester Co. Estuarine deposits, their position in a rock-systeiii, 100-102, lU. Etheridge, ]{obt., on organic origin of graphic granite, xi. , accepts " Eozoon." See Corri- genda. Eiilysyte (a peridotic rock) of Tuna- berg (Sweden), (!2. Euphotide, 2, 38, 42, 54, 07. Europe under Pliocene climatal con- ditions, \h~). Expailly (Auvergne), peridote of, 03. F. Ffhlun . (Sweden), primitive schists of, 32. Fallon, M., on serpentine, 37. Fassaite, its relation to augite ar.d serpentine, 37. Faults in relation to systems of rock- jointing itc, 109-111. Favre, Alphouse, his discovery of " Eozoou" in the crystallines of the Jungfrau, 31. Fayalite a peridotic niinerfd, 02. Feldspars, 24, 20, 29, 31, 39, 49, 50, 52, (50, 02, 72, 75. • interlaiuellatod witli calcitp 13. with quartz. Sec Granite, gi-aphic. striping or striation of, xxxiii. Fossils of the dolomites of Tyrol, 32. of the (?) I'ermian and (?) Car- boniferous rocks of N. India, N. America, and Austrian Alps, i04. of the Permian and Carboni- xxxix, xl, xli, xlii, 12, 120. Feldsyteot'Giihvay serpentinizcd, 41. Fencstella retifonnis, a doep-wiitor organism of the I'ermian period, 103. Ferruginous serpentines, 5. Figures de corrosion. See "Eozoou," "canal system." Fiudelen glacier moraine, peridote and caljitic veins in blocks of, ()2. Floceulite (Hoccuieut serpentine), its J}i/ni\.: de corrosum form the " canal svsteni " of " JEozoon" xviii, 0, 10, 19", 20, 23, 50, 59, 84. Fogo (Cape-Verd Isles), peridote of, 01. Formations, Cambrian, deficient in limestones, 83-88. , Permian, 99, 102. , , as divisions in a rock- system, 100, 101, 102. Forsterite a peridotic mineral, 01. ferous rocks, 103. Franz-Joseph Laud, its climate under altered physical conditions, 110. Froisset, M., on metamorphic rocks of lOurope, 31. Fuegia, its relation to the earth's volcanic girdle, 117. Fundamental roclis, origin of, 29. Funkite, 7. G. Gabbro of Portsoy, 38. Gages, Alphouse, on sei-pentino, 4, 6. Galway Co., rock-jointing of, 108. , glaeiai drift around, 93, 120. , igneous rocks near, serpenti- nized and caleitized, 27, 41. , crystallized limestones of West (Conuemara), 90. -, Queen's College, specimens de- posited in Geological Museum of, 18, 27, 94. Gangri range (Thibet), terraces of the, 114. CJaiuet, pseudomorplK.sed, 24. Gastaldi, I'rof. IJartolouieo, on meta- morphics of Central Italy, 31, 32. Geikie, Prof. Archibald, on deposits dredged by the ' Challenger,' 75. " Geikie, Prof.," stated to be in favour of tlie organic origin of the Harris graphic granite, xl. Geniaingoutte (Vosges), hemithrene of,5i. , , Genoa. Sec Spezzia. Geography, physical, in relation to geological plienoinena, 99-117. * Geological ISlagazine,' 23, 28, 57. Geological Survey of Canada, 29, 73, 70. time, 100, 117. phenomena in relation to svs- tems of rock-joiutiug, 107-117. Glassillaun. See Cleggan dyke. Glfvuconite, 0. Glenelg ( Scotland), calciu'eous marble of, 89. Glen Tilt (Scotland), 89. Gliukite a peridotic mineral, 01. Gneisses, 2, 31, 51, 52, 00, 72, 73, 81. Goniatitidie of Northern Ind: and the Austrian Alps, 104. Ui f Tyrol, 32. nd (':') Car- , ludia, N. Alpf,, i04. d Carboni- iinate under ions, 110. rphic rocks xhe earth's n of, 29. lentine, 4, 6. . , on crystalloids, 60, 79. , his " novel doctrine " in oppo- sition to metamorphism, vii, xiv, 1, li, 28-33, 30, (54, 74. , on dolomitization, 91. -, on " JEozoon Canadense,''^ ix, xi. xv-xviii, xxiv, xhv, Iviii, 10. — , on origin of serpentine &c., vii, 29, 30. — ', on origin of limestone, xxv, xxvi, 75, 70, 78. -, on granitic and calcareous « veiu-rocks," 60, 04, 78-81. Mi 134 INDEX. !.= , Huronian rocks, 74, 88. Hyalite in Roman masonry at Plora- bieres, 86. Hyalosiderite, its relation to peridote, 61. Hydration of minerals &c. See Sol- vents. Hydatothermic, Bunsen's name for hydrothermal, 35. Hyarocalcite, 7. Hydromagnesian silicates (serpen- tinous minerals, &c.), 4-7. Hydromaenesite, 7. Hydro-pmogopiteschists, 2. Hydrothermal action on rocks and minerals. See Solvents. Hydrous acuminate of magnesia (volknerite^, 7. magnesia (brucite), 7. silo-magnesiau marl. See Sepi- olyte. Hypersthene, 7, 62. Hypersthenyte of Elfdalen, 12, 62, 123. I. Idocrase, 7, 14, 51. Imitative shapes in minerals. See " Eozoon^^ " canal system." in dolomite. See Co- ralloids. Imp.anetta, ophite of, 46. India, Northern, fossils of, 104. Infra-Liassic fossils in metamorphics of Mont-Cenis district, 32. Intrusive or igneous serpentine rocks, xiv, xliv, 46. Ireland, Geological Survey of, 39, 48, 90. • , west coast of, affected by Gulf- stream, 116. Irish Academy, Proceedings of Royal. 17, 20, 29, 32. dolomites, 94. Isle of 3kye, Eozonal marble of, xvi, xxxviii, 11, 32, 41, 67, 87, 89, 96. Italy, Central, ophites of, 97. , Northern, vegetation of, 116. J. Jannettaz, M. Edouard, referred to, 13. Jardin des Plantes, specimens in Geological Museum of, 13. Jersey, diorite of, changed into cal- cite, 26, 60. . New. See Amity. Jems, Chevalier, on serpentine rocks of Italy, 46. Johnston, Prof. James F. W., on mag- ncsian limestones of Durham, 91. Jointing in rocks, 63, 80, 90, 94, 106- 112,118,119. Jones, Prof. T. Rupert (" T. R. J."}, on ^^ Eozoon" xi, xiv, xxii, xlii, xlvi. Judd, Prof. J. W., volcanic rocks of Scotland, 97. Jungfrau, occurrence of **Eozoon" near the, 31. Jurassic ophite of Skye, occurrence of " Eozoon " therein. See Isle of Skye. metamorphics, 31, 32, 87. JuroUa, vapours still disengaged from lava of, 66. K. Kalkgebirg (Todte Alps, Engadine), lameUar ophi-calcite of, 11. Eammererite a serpentinous mineral, 6. Kaolin, Prof. Ileddle on, 39. Kara Sea, its genial temperature, 116. Karsten's 'Archiv fiir Mineralogie,' 32. Karstenite psendomorphosed into selenite, 23. Keilhau, M., on hemithrene of Scan- dinavia, 63. Kerguelen's Land, its relation to the earth's volcanic girdle, 117. Keuper of Cheshire, its rock-salt, 92. Kilkenny coal-beds, their place in . the Carboniferous system, 101. Killas, serpentinized, 2, 43. Kinahan, G. H., on serpentine of Cannaver Isle, 39, 46. , opposes "Eozoon,'^ xxvii. King, i)r. Clarence, on Wahsatch mountain-mass, 111. King, Prof. William. See Rowney. , on metasomatosis, 28. , on a silo-carbacid rock in Ceylon &c., xxix. ,' reply to Dr. W. B. Carpenter, X}.11. — , on Permian limestones of Dur- ham, 94, 118, 119. INDEX. 135 intocal- tine rocks ,, on niag- ham, yl. 1,94,106- r. R. J."), Kxii, xlii, I rocks of "Eozoon" )ccurrence fee Isle of ,87. aged from 5ngadine), 11. IS mineral; 9, iperature, leralogie,' Ised into of Scan- Ion to the 7. c-salt, 92. 1 place in , 101. ptine of Ivii. /^absatch lowney. Irock in krpenter, of Dur- King, Prof. William, Xera and Tha- lassa in the Permian period, 99- J 21. Knocktopher sandstone. Carboni- ferous system, 101. Knop, M., on metasomatosis, 28. Kobell, M., on cbrysotile. 8. Kuntze, O., on " Hozoon, xlvi. Kyschtimsk, peridolyte of, 62. L. Labradorite. See Feldspars. Lacustrine deposits, their place in a rock-system, 100, 101, 104. Ladak, elevated lakes of, 114. Lancashire " Bunter," its relation to the Permian system, 102. Land and sea features in relation to different stages of vertical move- ments of the earth's crust, 100. Larval evolution, 85. Lasaulx, Prof, von, on metasomato- sis, 28. Laurer+' n rocks. See Archaean TOCkS Lava, 65, 66, 69. Laveline (Vosges), hemithrene of, CI. Leibnitz, on metamorphic rocks, 28. Leipervillite a peridotic mineral, 61. Loonhard, Von, on origin of hemi- tLiene masses, 63. Letterfrac (Connemara), crystalline limestone of, 90. Leuchtenbergite, 5. Leucite, its origin, 66. L6vis dolomites and limestones of Canada, 48. Lewis (Hebrides), hemithrene of, 68. I>herzolite, 2, 37, 62. Liassic metamorphics, 32, 96. Liguria, ophites of, 97. Limbilite a peridotic mineral, 61. Limehillock (Scotland), serpentine &c. of, 65. Limestones, Carboniferous, of Ireland dolomitizea, 94, 101. , Archsean, origin of. See Hunt, Hull, Ramsav, and Chap. xii. • , " Eozonal." See Ophites. , magnesian. See Dolomites. , mineralized, 89, 90. ■ , methylosed. See Methylosis. of mechanical origin, 120, 121. • of chemical origin (their organic origin " a fallacy "). See Hunt, also 120, 121. Limestones rare in Cambrian system, 83-87. Lisoughter (Connemara) crystalline limestone, 42. Lizard (Cornwall), serpentine rocks of, xliii, 11, 21, 37. Llandeilo flags, impure limestones of, 84. Lochaber terraces, 113. Loch Eribol, subcrystalline lime- stones, 33. Logan, Sir W. E., on Laurentian rocks of Canada, ix, 45, 73, 74. , on " Eozoon" viii, ix, x, xiv, xxi. Loganite, a pseudomorph after horn- blende, XV, 6. . See " Eozoon " in loganite. ' London and Edin. Phil. Magazine,' xliii, 2, 11, 37, 43. Longmynd rocks non-calcareous, 76,83. Lough Corrib. See Cannaver. water contains lime in mechanical and chemical suspen- riion, 120, 121. Lower Cambrian limestones, 83-87. Silurian limestones, 33, 84, 88, 89. metamorphics, xlii, xliii, .33,88. Lyell, Sir Charles, on metamor- phism, vi. , accepts " Eozootif* xxix. M. Macalister, Dr. A., accepts " Eozoon,^ xxix, XXX. MacCuUoch on coccolite marble of Tiree, 48, 55, 6Q, 69. M'Miillen, J., early discoverer of " Eozoon" ix. Mftdawaska (Canada), crumpled layers of limestones at, 72, 73. Magnesian limestones. See Dolo- mites. of Durham, their con- figurations. See Coralloids. silicate minerals, their origin, 24,25,26,29. Magnesiated rocks, Prof. Ileddle on, 39 ; J. Arthur Phillips on, 43. Magneso-argillyte. See Sepiolyte. Malacolite, xv, xvi, 7, 21, 22, 23, 60, 57,58,60,61,83. ' ' 136 INDEX. , ' I M Malacolite replaced by calcite, xvi, Ivii, 21, 50-53, 57, 58, S'3. Malacolophyte3, xvi, 2. Malbay flags, their place in the Car- boniferous system, 101. Manchester marls, their place in the Permian system, 92, 102. Marbles, calccreo - crystalline. See Hemithrenes. Marl-slate of Durham, its place in the Permian system, 92. Marmolite, 5, 0. Marsden limestone of the Permian , system, 107. Maryland (U.S.), terraces of, 113. Massachusetts, hemithrene of, 03. Mather on origin of hemithrene masses, 53. Max SchiUtze on "J?osoom," xxix- xxxii. Meridional. See Jointing. Metamorphic rocks, methylosed. See Methylosis. , mineralized. See Meta- morphism. of Canada, 72-83. Metamorphism, v-vii, 1, lii, 7, 28-59, 72-83, 01-95, 105, 100, 118, 119, 121. Metamorphosed " igneous " or irrup- tive rocks, 39. Metasomatosis, 28. Metaxite, its structures and relation to serpentine, xviii, 0, 10. Meteoric peridote, 03. Methylosis, vi, xxix, xliii, 28-83, 91- 95, 105, 100, 118, 119, 121. Mettenbach (Switzerland), "Uuzoon" of, 31, 32. Mettenberg (Switzerland), Aiumo- nites in gneiss of, 32. Ikliask, peridote in metamorphics north of, 02, Mica-schists, Dr. Sterry Hunt on their origin, 29. Midderidge limestone, its place in the Permian system, 102. Miemite, the crystalline form of the rock dolomite, xv, 29. Milan Cathedral built of ophi-cal- cite, 3. Millstone-grit of the Carboniferous system, 101. INIiuerals that occur calcitized, 2G, 51. Mineral carbonates, their part in hemithrenes, 29. cleavage. See Cleavage. " Mineral Resources of Italy " (Che- valier Jervis), 40. Mineralized limestones, 89, 90. metamorphics. See Metamor- fthism. ineralogical Magazine,' 8, IG, 48. 'Mineralogy of Scotland,' lleddle's, 38. Miocene climate and vegetation of the Arctic regions, 115, 110. Mcibius, Prof. Karl, accepts " Eozoon" xliv. , rejects ''Eozoonr xlv. , in reply to Dr. Dawson, xlvi. Modum (Norway), hemithrene of, 40, 03. MoUusks, Cambrian, little lime in their shells, 85. 'Monograph of Permian Fossils of England,' 92, 99. Monradite a serpentinous mineral, 5. Mont-Cenis district, metamorp'-'os of, 31, 32. Mont St. Philippe (Vosp^es), hemi- threne &c. of, xvi, xlvii, 22, ^^., 52, 63, GO, 78, 87, 124. Monticellite a peridotic mineral, Gl. Monzoni (Tyrol), serpentine pseudo- morpluc after augite at, 30. Mouroe Mountains, peridote in gra- nite of, 0'^. Movemeuia, vertical, of the earth's crust, 100-102, 104, 113-115. Miiller, II., on the origin of serpen- tine, 37. , Prof., of Basle, referred to, 11. Murray on the 'Challenger' dredg- iugs, 75. Muscovite, its relation, to phlogopite, GO. N. Nantwich (Cheshire) rock-salt, its origin, 92. Natal (Africa), terraces of, 113. Natrolite, its occurrence in granite, 34. 'Nature,' xxvi, xxvii, xxxiii, xl, xlv, liii, 30, 75. Naumann, C. F., on pseudomorphism, , on serpentine, 37. on rounded crystalloids of augite &c., 50, Neolite, 5, 29, 30. Neptunists, Sterry ilunt on, 30. Novi? Ben, terraces of, 1 13. ly " (Che- ,90. Metamor- 8, 10, 48. lleddle's, etation of 110. V. son, xlvi. threne of, e lime in Fossils of mineral, 5. tamorp'-^'is es), hemi- ineral, 01. ne pseudo- .'30. )te in gra- tlie earth's J-115. of serpen- red to, 11. or' dredg- )lilogopite, jk-salt, its 113. ill granite, iii, xl, xlv, niorphism, alloida of n, 30. 3. INDEX. 137 10° the New Brunswick, metamorpliics of, 88. New Jersey, '^Hozoon " »S:c in hemi- threne of. See Amity. New- York State, crystalline lime- stones of, 50, 50, 88, Nicholson, Prof. H. Alleyne, on or- ganic remains iii Harris graphic granite, xxxix, xli. Nickeliferous serpen;' le (Nouemite), 4,6. North Pole, present vegetation or 17° below, 110. , its proximity to earth's volcanic girdle, 117. Northern Italy, methylosed rocks of, 00. - — , relation of its present flora to that of Grinnell Land in the Miocene period, 110. Norway, raised shell-beaches of, 113. Nouemite, a nickeliferous serpentine, 4, 5. 0. Odern (Vosges), homogeneous slate serpentized at, 44. Oligoclase. See Feldspars. Olivine. See Peridote. Olivinoid a peridotic mineral, 01. Olivinyte a peridotic rock, 71. Ontario, Eastem, " fundamental gneisso-syenite " of, 73, 77. Ophi-calcites, Ophi-dolomites, Ophi- euphotides, Ophi-magnesites. See next reference. Ophites (see Serpentine rocks) defined and classified, 1, 2. , their minerals, 1, 2, Szc. , their structural characters. Introduction generally, 8-22, 50, 04, 70, 79, 122-120. of Connemara, xi, xxi, 40. O'Reilly, I'rof. J. P., on sepiolyte of Vallecas, Madrid, 29. Organisms, Cambrian lime-elabora- ting, 86. Ossipyte a peridotic rock, 2, 71. Ottawa, Laurentian conglomerate of, 77, 87. Oughterard (Connemara), crystalline limestone near, 42. P. Pacific Ocean, deposits in abysses of, during the various geological periods, 116. Palajozoic metamorphics, 31, 32, 33, 88, 89. rocks, fossils of earliest, 85. Pamir (High Asia), in relation to equatorial jointing, 112. Paradoxides, rarity of lime in the shell of this trilobite, 85. Pargos (Lapland), hemithrene of, 40, 50. Paris basin, sepiolyte of, 44. Parker, Mr., accepts ^^ Eozoon,^' xxii. Patagonia, terraces of, 113. Patagonian Andes, their relation to the earth's volcanic girdle, 117. Pebidii.n series, 83. Pelagic deposits, their place in a geological rock-system, 101, 102, 115. Penninite a serpentinous mineral, 5. Pennsylvania, terraces of, 1 13. Peridolytes (peridotic rocks), 2, 40, 02, 7L Peridote (olivine), 7, 17, f?4, 26, 37, 40, 60, 01-71, 75, 123, 124. under the polariscope, 17, 60, 03, 04, 70, 71. Permian rocks, 91-95, 101-100, 118, 119. fossils, 99, 103, 104. physical geography, 99-100, Pony, .John K, opposes ^^Uozoon" xxviii, xxix. Philippe, Mont St. See Mont St. Philippe. Phillips, J. Arthur, on serpentinized killas, 2, 4:5. Phillips, Prof. John, on "J-Jozoim,"' x'vii, , on rock-jointing, 107. Phlogopite, 7, 24, 29, I'hosphate of lime in Cambrian fossils, 85. Physical geography of the Permian period, 99-100, , its phenomena in relation to rock-jointing, 107-117. geology, 107-117. Pic d^^ridlitz (I'ynnees), calci-feld- spar rock of, 13, Picrosmine a aerpentinous mineral, 5, 0. Picryte a peridotiferous rock, 2, 02. Pisani on leipervillite, 01. Pla'gioclase, its presence in the * Challenger ' soundings. To. I I , 138 INDEX. See Plagioclase, striping or strise of, Feldspars. Plateaux, continental, in relation to the intervening oceanic depres- sions, 110, 112. Pliny, his name chrysolite, 61. Plomoieres, action of alkaline water on Roman masonry at, 35. Plutonists, Sterry Hunt on, «?0. Podermo (Tuscany), argillaceous schist changed into serpentine, 44, 97. Polarization of serpentine, 60, 63. of peridote. See Peridote. Polmally (Scotland), " lime and ser- pentine beds " of, 55. Pompeii, its ruins contain fragments of ophi-calcite, 11. Pontetract sandstones of the Permian system, 102. Porphyritic serpentinyte of the Li- zard. See Lizard. rooks near Galway, serpenti- nized, 27, 41. Porthlisky ( Pembrokeshire) , * ' impure limestone beds " of, 83, 84. ( ), malacolite replaced by calcite, xvi, 83. Portsoy, serpentine and other rocks of, 30, 54, 55. Post- Archaean ophites and hemi- threnes, 87, 96. Potsdam rocks, rarity of non-crystal- line limestones in, 84, 85, 88. Prato (Central Italy), ophites of, 40. Pre-Cambrian metamorphics of East- ern North America (Hunt), 33. Predazzite (hydrous dolomite) of Conzocoli (tyrol), 7, 41. Presidential Address of Leonard Horner, 48. of 11. C. Sorby, 109. of Dr. A. Macalister, xxix, XXX. Pre-Silurian metamorphics according to Sterry Hunt, 33. "Primary limestone." See Ilemi- threnes. " Primitive water " in granite and metamorphics, 34, 35. Prochlorite, 6. Productus horridm, P. gigantetcs, P. ponderosus, their habitat, 103. " Protogeea" of Leibnitz, 28. Protogines, 2. Protozoans of the Cambrians, 85. Pseudo-diallage, 5. Pseudomorphic serpentine minerals, 6. Pseudomorphism, vi, xiv, xxxv,xxxvi, xlix, 1, li, 11, 19, 23, 24, 67. Pseudophite, 6. Pusyrewski on " JSozoon" xx. Pyrallolite a serpentinous mineral, 6,6. Pyrocaustic rocks according to Bun- sen, 35. Pyrosclerite a serpentinous mineral, 5, 27, 62. in " Eozoon;' xlvii, 124. Pyroxene, white. See Malacolite. "Pyrox^nique " rocks according to Alex. Brongniart, 47. Pyroxenites, their association with hemithrenes, 78, 81, 82. Q. Quarry-water (" eau de carriSre), 35. * Quarterly Journal of the Geological Society,' 22, 28, 29, 35, 37, 42. Quartz, pseudomorphic and original, 67. Quartzites &c. of Loch Eribol, 33. Quebec fault, its extent and direc- tion, 111. " Quebec rocks " in Canada and Northern New York, 48, 88. Queen's College, Galway, specimens in Geol. Museum of, 18, 27, 94. E. Ragged Chute (Madawaska,Canada), corrugated layers of gneiss and limestone, 72. Ramsay, Dr. A., on rock metamor- phism, V. on origin of Archaean lime- stones, xxii. on Permian formations, 91, 99, 101, 103-100, 119. adopts " Eozoon" :cxii. Reade,T. Mellard, opposes "jEbsoon," xxvi, xxvii. Regional cyclical vertical movements of the earth's crust, 100-102, 106, 113-115. metamorphism. See Metamor- phism. Reichenstein (Silesia), chrysotile of, 8, 15, 10, 123. Renard, Abb^, on the ' Challenger ' soundings, 75. INDEX. 139 ninerala, :v,xxxvi, i7. mineral, • to Bun- mineral, I. icolite. rding to ion with riere), 35. l^eological 7, 42. . original, bol, 33. ind direc- ada and 88._ pecimens 27, 94. ,Canada), iisa and letamor- m lime- s, 91, 99, lEozoon" pvements L02, 106, [etamor- Isotile of, Uenger ' Rensselaerite a serpentina mineral, C, 6. forms an ophitic rock, 2. Retepora cellulosa simulated in Cor- nish serpentinyte, 11. Retinalite, 6. Rhodochrome, 5. Richardson, T., oa dolomite, 01. Ripidolite, 6, 6. Roches homogenes et het^rogenes of Alex. Brongniart, 47. Rock-jointing. See Jointing. Rogers, Professors, on decomposition of serpentine, 4, 25. Roman baths at Plombieres, minerals generated in brickwork of, 35, Rose, Gustaf, origin of serpentine, vii, 37, 41. Rossie (St. of New York), ciystalline limestone of, 66. Rottenstone, a product of rock-alter- ation, 43. Rowney, Dr. T. H. (in conjunction with Prof. W. King), xii, xiii, xxii, xxiii, xxviii, xxxiii, xxxix, xliii, xlvi. ( ), on regional metamor- phism, 34, 35. ( ), on dolomitization, 92, 93, 94. Rozel on hemithrene of the Vosges, 53. Rutley, Frank, on the serpentire of Cannaver Isle, 40. S. Sahlite, 7, f-S, 57. St.-Bee8' red sandstone, its place in the Permian system, 101. Sainte Marie-aux-Mines. See Mont St. Philippe. St. Paul's Islands, their relation to the earth's volcanic girdle, 117. Sandberger, F., on origin of serpen- tine rocks &c., 70. Sandford, W. A., on " Eozoon " in Connemara marble, xl. Sanidine, its occurrence in deep-sea deposit d, 76. Saponite, xliii, 5, 11. Sapphire, its occurrence in hemi- threnes &c., 7. Scheerer on pseudomorphism, vii, 24. on aqueous origin of granite, 34. on hemithrenes, 48, 53. Schimper, Prof. W. P., opposes "Eozoon" xlix. Schtzodtts-hvaeatoneB, their position in the Permian system, 102. Scouler, Dr. R., on dolomite, 91. Sedgwick, Rev. Prof. Adam, on ser- pentine rock of the Lizard, 87. on coralloids of the Durham magnesian limestone, 03, 106. Sedimentary ophites, 45, 46. Selwyn, Alfred R. C, on L^via metamorphics, 48, 88. , on Huronian rocks of Canada, 74. , dh thickness of the Archsean rocks, 73. Sepiolyte (sepiolite, " argile mag- n^sienne), 2, 5, 29, 44. Sequoias, fossil, of Grinnell Land and Spitzbergen, 116. Serapis, columns of verd antique in temple of, 11. Serpentine minerals, their pseudo- morphic origin &c., xiv, 1, 4^7, 24, 60, 63, 64, 71. rocks (serpentinytes), their methylotic origin. See Methy- losis. generally. See Ophites. — ; , kinds originally igneous, intrusive or eruptive, xiv, xliv, 46. , kinds originally sedimen- tary, 45, 46. Serpentinized porphyry, granite, sy- enite, and other rocks near Gal- way, 27, 41. rocks. See Methylosis. Serpentinytes, xliii, 2, 11, 21, 37. Seybertite, 5. Shallow-water deposits, 100, 101, Sharpe, Daniel, on slaty cleavage, , on terraces of the Alps, 113, Shetland, serpentines &c, of, 38, 48. . South, its relation to the earth's volcanic girdle, 117. Siberia, meteoric falls of, 63. , Boreal, under genial climatal conditions, 116. Sideromelane, its occurrence in deep- sea deposits, 75. Silacid or ordinary metamorp>hics, 2, 76, 76. and silo-carbacid ophites. See Serpentine rocks. 140 INDEX. Silicate of magnesia, anhydrous, 24, 25. , ' .ydrous. See Serpentine minorala. Silurian period, calcareous deposits of, m. Siphnnoti-eta, spines of, containing glauconite, (>. Six, A., on " Eozoon" xlvi. Skye, Isle of. See Ish; of Skye. Slaty cleavage, 107, 10!). Sleat (in Skye), I'ost-Canibrian metaniorphics of, Ji.'i. Smaragdite, 7. Smyth, Warington W., on "Euzoon,"" XX. Snarum (Norway), peridote of, 08, (ir). Sollas, Prof. W. .T., on Bristol dolo- njitic conglomerate, 121. Solvents or solutions, their dissol- ving or was+iug action on crystals &c., 2.), 20, .•54, 3o, rA, 53, 0"i. 70,80. Solway red sandstones, their position in the Permian system, 102. Sorby, II. (Uift()ii, on dolomitization of Permian magnesian limestone, J)l. , on liquid cavities in metanior- phics, 34. , on slaty cleavage, lOf). South I'ole, its proximity to the earth's volcanic girdle, 117. Shetland in relation to the earth's volcanic girdle, 117. Spadaite a serpentine, 5, 44. * Spanish Geology, Notes on,' 29. Spezzia (Central Italy), Alberese limestone near, ophitized by dykes of euphotide, 42. Sphene in hemithrene, 7, /)o. Spinel in ophites &c., and its inti- mate association with eozooual structures, xxiv, xxv, 7. Spitzbergen under genial climatal conditions, 116. Staurolite, pseudomorphic after an- dalusite, 23. Steatite, o, 55. Stevenson, Prof. J., on Ammonites &c. of the Rocky Mountains, 102. -. , on " horizontal benches " of the AUeghanies, 113. Straits of Belle Isle, calcareous Aca- dians of, 84. Stratal disturbances of the earth's crust, 109-112. Strut hdon (Scotland), marbles of, 89. Striping of feldspars. See Feldspars. Studer, Prof. Bernard, on metamor- phism &c., 31, 32. ' Study of Bocks,' liutley's, 40. Stylolitic structure in rocks, 12. Sullivan, Dr. (Pres. Queen's Coll., Cork), on origin of sepiolyte of ^'allecas, 29. Sulphuric acid, the part it plays in methylosis, 93. Summer-day of sunlight in Arctic regions, 110. Sunderland (Durham) coralloidal limestones, xviii, xix, 93, 102, 118, 119. Sutherlaudshire, Lower Silurian me- tamoi-phics of, 33. Swamp-cypress. See Taxodium. Swinaness (Unst), altered rocks of, 38. Symes, R. Glascott, on crystalline limestones of Mayo, 90. Synersk (I^^ral), peridote of, 02. Systemal periods, 100. T. Tabergite a serpentine, 5. Taimyr peninsula in relation to High Asia, 112. , its climate and vegetation, 110. Talc a hydrous mineral occurring in granite, 5, 34. Talc-gneisses or protogines, 2. Talc-schists, 2, 02. Tarbert (Harris) gi-aphic granite, its pi'esumed organic structure. See Granite, graphic. Taunus slate alkaliferous, 31. Taxodium (swamp-cypress) accli- mated to Arctic conditions, 110. Terraces of mountains, their relation to changes of ocean-level, 113,: 114. " Thalassa and Xera in the Permian period," 99-100. Thermophyllite a serpentine, 5. Thibet, terraces of, 114. m INDEX. 141 accli- iditions, 'erraian Thomson, James, his bolief in orp^anic fitructuros in Tarbert ^Taphic j^ra- nite, xxxix. Tliuringerwald, alabaster of the, 4'J. Tiree, marble of, 48, /io-SO. Titaniferous peridote of Zerniatt, 01 . Torrin dale of Skye), eozoonal ophite of, 41. Totaigite a calcareous serpentine, 5. Tourmaline, 7. Towanrietf hill (Scotland), serpen- tine of, 88. Trans. Cambridge Phil. Society, 87. Trans. Royal Soc. of Edinburgh, ,'58. Tremadoc rocks, scarcity of limestone in, 83. Tromolite of St. Gothard, 80, 125. Trenton metamorphics. See West- chester Co. Triassic metamorphics, 81 , 82. deposits formed in inland seas, 02, t)8. Trinity T^and, its relation to the carth'^ volcanic girdle, 117. Tscherniak, G., on serpentine, 40. Tudor " Eozdon,"' xxiii. Tunnberg (Sweden ), metamorphics of, (52. Tuscany, recent formation of serpen- tine ill, 97. Tweedian beds, their position in the Carboniferous system, 101. Twining, Frederick, of Cleggan Tower, 48, 50. Tyrol, dolerite of Bufaure in the, 36, 37, 43, 91. , pseudomorphs in serpentine after augite at Monzoni in the, 30. U. Uddevalla (Sweden), peridolyte of, 02. Unkel, peridote of, 08. Unst (Shetland), serpentine rocks of, 38. Upper Cambrian metamorphics of Eastern North An:crica, 33. Ural talcose rock, 02. Urkalk, 47, &c. See Corrigenda. V. Vaalite a serpentine, 5. Vallecas. See. Sepiolyte. Vegetation of Arctic regions, 110, 117. Vein-masses of granite and limestone. See Dyke-like masses and Hunt on ditto. Venerite a serpentine, 5, Vennor, Henry (t., on thickness of Archajan rocks, 73, 74. , his discovery of "j&«soa?t" on the Gatineau, xlvi. Vermont, North-western, calciferous formations of, 84. Vertical movements of the earth's crust. See Cyclical ditto. Vesuvius, peridot ! in lava of, 05, 09, 70, 71. Vigan (D.'pt. du Gard), calci-feld- spathic gneiss of, 18. VilanoAa y Peira, Juan, opposes '^ Uozoon," XXXV. Villa Itota, its slate changed into schisto.-ic serpentine, 44. Villarsite a serpentine, "i. Virginia (U. S), terraces of, 113. Voigtland, diorite of, changed into serpentine, 87. Volcanic girdle of the earth, 117. Volcanoes of the western borders of the two Americas, 117. Volknerite, 7. Volten-a, dykes of ophite ai, ^0. Von JJucli, his theory of dolomiti- zation, 91. ^'on Leonhard on origin of hemithrene masses, 58. Von Morlet on dolomite*, 91. Von Q^]ynhausen on calcite dyke near Auerbach, 51. Vorhauserite a serpentine, 5. Vosges. See Mont St. Philippe. W. Wahsatch, mountain-mass of. 111. AVestchester Co. (New York) meta- morphics, their age and origin, 33, 59,88,89. ^ ' ' Westoe (Durham) Sif/iUan'a-iiand- stone, its place in "the Permian system, 102. Wick, M., on the age of the crys- tallines of the Central Alps. 31. ^ ' Wilson, Dr. James, an early discoverer of " JEozooji," ix. Winter-night of darkness in the Arctic 142 INDEX. j regions in relation to vegetable ' ^owth, ii*^. Wisembach (Vosgos), rocks of, /il. Wollastonite occurs in altered rocks, 7,51. X. Xera (and Thalassa) in the Permian period, 99-106. Xerothermal rocks, 86, 71. Y. Young, John (Ilunterian Museum of Glasgow), referred to, 70. Z. Zermatt, peridote of, 01, 02. Zircon occurs in methylosed rocks, 7, Zirkel, Prof. F., on rounded crystal- loids in homithreae, xxvi. , on " Eozoon" xxix. Zittel opposes ^^Eozoon" xlix. ; ■■:■ 1 Printed by Taylor and Francis, Bed Lion Court, Fleet Street. 1 Museum of 70. 02. ed rocks, 7. led orystal- :vi. kUx.