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Maps, plates, cherts, etc., mey be filmed et different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand comer, left to right and top to bottom, as many frames aa requi.«d. The following diegrams illustrate the method: Les certes, planches, tableaux, etc., peuvent Atre filmte A des taux de rMuction differents. Lorsque le document est trop grand pour Atre reproduit en un soul clichA, il est filmA A partir da I'angie supArieur gauche, de gauche A droite, et de haut en bas, en prenant ie nombre d'images nAcessaire. Les diagrammes suivsnts illustrent la mAthode. 1 2 3 1 2 3 4 5 6 i%f^!TP'^ ^iHfJ 1^ ^ Hi,* Tfr V* > i s.t "^ I f' McGILL UNIVERSITY lis PAPERS FROM THE DEPARTMENT OF Geology. No. 2. — Review of the Evidence for the Animal Nature of Eozoon Canadense. Pt. 2. — Petrological and Chemical. BY Sir J. William Dawson, C.M.G. [Rtpriated from the Canadiui Record of Science, Janiuirj and April, 1896, pp. 6a-77.1 »^.- : p* l:>,*>^' Montreal, 1896. v.; ',\ ■ , ,-,;-l'- •/ I II I .. .,y^w,, -i . . », ., „ —— " Reprinted from the Canadian Record of Science, Jan. and April, 1896." Review of the Evidence for the Animal Nature of EozooN Canadense. (Concluded. ) By Sir William Dawson, C.M.G., LL.D., F.R.S., Etc.* II. PETROLOGICAL AND CHEMICAL. Bearing in mind the statements made in the previous note, respecting the stratigraphical relations of the Grenville Series, and referring to the excellent account by my friend Dr. lionney of his observations at Cote St. Pierre, and to some difficulties stated by him which merit attention, we may sum up the evidence so far, under the following statements • — 1. The limestones included in the Grenville Series and their associated quartzites and schists bear so strong a resemblance in mineral character to metamorphosed Paheozoic calcareous beds of organic origin and their associates, as to warrant at least the careful consideration of any forms apparently organic contained in these limestones. 2. The occurrence in these limestones of nodular silicates, of graphite, of pyrite, and of apatite, affords additional reason to suspect their organic origin. 3. The presence of large beds as well as of veins of graphite and of thick deposits of iron ore in the (Jrenville Series constitutes an additional analogv with Palieozoie formations holding organic remains.'^ These facts were adduced by Dr. Sterry Hunt and Dr. J. D. Dana in evidence of the probability of life in the Laurentian period, even before the discovery of Eozoon. Certain particulars connected with them, how- ever, now demand somewhat more detailed attention, in 1 [Reprinted from Uie Geological Magazine, Decade IV., Vol. II., October, Novem- ber, December, 1895. > See papers by the antlior on the Graphite and Pliospliate« of the Laurentian Rocks, Quart. Jour. Geo). 8oc. London, 1860 and 1870. Animal Nature of Eozoon Canadense. 63 connection willi thai discovery, juitl with recent objections to the organic natnre of Eozoon. Dolomite or niagnesian limestone is a not infrequent associate of I'ahcozoic fossiliferons limestones ; and I have remarked in previous papers on the similarity of the mode of occurrence of silicified Stromatopora- in the great dolomite (jf the Niagara formation witli that of Eozoon in the (trenville Limestone, in which dolomite occurs in beds, in thin layers, and in disseminated crystals, in a manner to sliow that it was an original constituent of the deposit. Dolomite is ulso one of the most common minerals filling the cavities of Eozoon, and especially the finer tubuli. The mode of its occurrence on the small .scale may be seen in the following description of a section of a portion of a bed of limestone fi'nni Cote 8t. I'ierre, examined under a lens, after lieing treated with dilute a,cid. The specimen comprised about six inches of the thickness of the bed : — Crystalline limestone with cry.stals of dolomite, consti- tuting }i])out one half (fragments of Eozoon in calcite portion).' More finely crystalline limestone, with rounded granules of serpentine, some of them apparently moulded in cavities of Archieospherinte, or of chamberlets of Eozoon. Limestone with dolomite as above, but including a thin layer of limestone witli granules of serpentine. Limestone and dolomite, with a few grains of serpentine and fragments of Eozoon. Crystalline dolomite with a few fragments of Eozoon, as limestone, with canals in dolomite. Limestone with fragments of Eozoon, granules of serpen- tine, and groups of chamberlets filled with serpentine. We have thus a bed of limestone in which dolomitic 1 Digtingiiished by Uieir flue granular texture and canal-sygtems. I '^(P*:'^"'^ mm^^mf 64 Canadian Eccoi'd of Science. and serpentinous layers appear to alternate, and occasional fragments of Eozoon occur in both, while the smaller forms resembling fossils are, so far as can be observed, limited to the serpentinous layers. At Arnprior on the Ottawa a portion of the Grenville Limestone presents dark graphitic layers parallel to the bedding, and giving it a banded grey and white appear- ance which has led to its use as a marble. An analysis by Dr. Harrington shows that tlie graphitic layers contain 8.32 per cent, of magnesia, the lighter layers only 2.57 per cent., in the state of grains or crystals of dolomite. Associated with the marble there are also beds of brown- weathering dolomite, affording 42.10 of magnesia. The graphite in this marble, under the microscope appears as fibrils and groups of minute clots, and sometimes coats the surfaces of crystals or fragments of calcite, the appear- ances being not unlike those seen in carbonaceous and bituminous limestones of later date. In l)oth the above cases the magnesium carbonate is evidently an original ingredient of the bed, and cannot have been introduced by any metamorphic action. It must be explicable by the causes which produce dolomite in more recent limestones. Dana has thrown ligiit on these by his observations on the occurrence of dolomite in tiie elevated coral island of Matea in Polynesia,' under circumstances which show that it was formed in the lagoon of an ancient coral atoll, while he finds that coral and coral sands of the same elevated reef contain very little magnesia. He concludes that the introduction of magnesia into the consolidating under -water coral sand or mud has apparently taken place — "(1) In sea- water at the ordinary temperature; and (2) without the agency of any other mineral water except that of tiie ocean ; " but the sand and mud were those of a lagoon in which the saline matter was in pro- 1 '■ ComU and Coral I.slaiids," p. 356, etc. i^ Animal Nature of Eozoon Canadense. 65 cess of concentration by evaporation under the solar heat. Klement has more recently taken up this fact in the way of experiment, and finds that, while in the case of ordi- nary calcite this action is slow and imperfect, with the ara^onite which constitutes the calcareous framework of certain corals, and at temperatures of 60° or over, it is very rapid and complete, producinjj a mixture of calcium and magnesium carbonates, from which a pure dolomite more or less niixed with calcite may subsequently result.' I regard these observations as of the utmost importance in reference to the relations of dolomite with fossiliferons limestones, and especially with those of the Grenville Series. The waters of the Laurentian ocean must have been much richer in salts of magnesium than those of the present seas, and the temperature was probably higher, so that chemical changes now proceeding in limited lagoons might have occurred over much larger areas. If at that time there were, as in later periods, calcareous organisms composed of aragonite, these may have been destroyed by conversion into dolomite, while others more resisting were preserved, just as a modern Polytrcma or Balamis might remain, when a coral to which it might be attached would be dolomitized. This would account for the persistence of Eozoon and its fragments, when other organisms may have perislied, and also for the frequent filling of the canals and tubuli with the magnesian car- bonate. The question now arises as to the mineralization of Eozoon with serpentine, and more rarely, especially in the case of its larger and lower chambers, with pyroxene. Connected with this is the alternation, as above described, of serpentinous and dolomitic layers in the limestone, as if in successive times the conditions were alternately favourable to the deposition of magnesium in the form of carbonate and in that of silicate. » Bulletin Geol. Soc. Belgium, Vol. IX. (1895, !>. 3). Also notice, in Geol. Mag., July, 1895, i>. 329. 66 Oanhdian Record of Science. We learn from the " Challenger " Reports that under certain circumstances the presence of organic matter in oceanic deposits causes an alkaline condition, tending to the solution of silica and the formation of silicates. We also learn that siliceous matter in a state of fine division {e.g., volcanic dust) may afford material for the production of hydrous silicates, either directly or indirectly through the agency of organisms forming siliceous skeletons. The " Challenger " Reports also show that the silicates known under the name of glauconite,'and thus deposited, contain several bases to some extent interchangeable. Of these the principal are aluminium, potash, and iron, though magnesia is also present. Some older silicates injecting fossils in the Palteozoic rocks are less complicated, and contain more magnesia : and, as Hunt has shown, there is nothing anomalous in the supposition that in the Lauren- tian period silicate of nuignesium and iron nuiy have acted in this capacity.* It is true that serpentine is now usually regarded as a product of the hydration of olivine and pyroxene ; still, even on this supposition, it might be formed from the hydration of fine volcanic dust falling into the sea. Hunt also has shown that the serpentine of the Grenville Lime- stone differs chemically from those supposed to be of direct igneous origin, in its comparative freedom from iron oxide, in its larger proportion of water, and in its lower specific gravity, besides being a n)ore pure silicate of magnesium. That it can be deposited by water is shown by the chrysotile filling veins, and by my own observa- tions, published long ago, on the serpentine replacing and filling cavities of Cambro-Silurian fossils at Melbourne in Canada, and filling the cells of Silurian corals at Lake Chebogamong.'^ t See AiinlyHes of GlauroniteM, etc., by Dr. Hunt hi " Dawn of Ijife," ji. 120. One tertiary exaniple is Hilicato of iron and magnesia. See also Hoskins on Olaiiconite, Geol. Mag., July, 1895. 2 Quart. Journ. CvC'. ^t:^. 1804, p. 09, alHu 1879, i>. 48, tt seq., Memoir on Eozoon in Peter Redpatli MuHeuin, 1888, i>. 48 et acq. Animal Nature of Eozoon Canadcnsi'. 67 The occurrence of pyroxene in the limestone, and tilling some of the chtunla'rs of Kozoiin, may also be easily explained. Dr. JJonney well remarks that it does not resemble any i«,'neons rock known to him, and it is (luite certain from its mode of occurrence that it cannot be directly igneous. Somewhat thick and continuous beds of a coarser-grained l)ut scarcely less pure pyroxene occur in .some parts of the (Jrenville Series, e.g., at Templeton, and I have described them as probably volcanic ash-beds, though the large [>yroxene crystals found in the veins of apatite traversing these beds are probably of thermo- aqueous origin.' But the limited and irregular masses and concretions of white pyroxene occurring in the lime- stones are of different texture and colour, and with less iron. They may have resulted from local showers of vol- canic ashes drifted by currents into hollows of the Eozoon reefs, and sufficiently fine to fill the chambers of dead specimens, while they might also form a basis for the growth of new individuals. This is, I think, the only supposition on which they can be explained, and it would also explain the difficulty suggested by JJr. Bonney as to the association of the pyroxene with Eozoon. There seems, however, to be no good evidence that any portion of the pyroxene has been changed into serpentine as a result of metamorphism ; and it is evident that if such a change had occurred after the consolidation of the rock, serious chemical and mechanical difficulties would be involved, whereas if volcanic dcjbris, whether of the nature of olivine or pyroxene, became hydrated while the rock was incoherent and in process of formation, this would tend greatly to promote the infiltration with hydrous silicates of any fossils present in the mass. Assuming the serpentine and pyroxene to have been deposited as above suggested, the remaining objections 1 In Logan's Geology of Canada, \>. 467, Hunt gives the analysis of a bedded pyroxene, at High Fi>lls, on tlie Madawaskn, as-Silica M.-iO; lime 25.65; magnesia 17.02 ; piotoxide of iron 3.24. 08 Caiiadia/i, Record of Science, stated by Dr. Bonney would at once disappear. Speci- mens of Eozoiin or other fossils might be infiltrated or filled with these silicates, and when the latter were super- al)un(lant they niight form separate concretions or grains, which might in .some ca.ses envelop the fossils or be attached to them in irregular forms, just as one finds in the case of the flints, in chalk or the chert in some other limestones." It is scarcely necessary to say that no objection to the organic origin of the Kozoiin can be founded on the fact that many of the specimens are fractured, crushed, bent, or faulted, by the movement of the containing rock, or on the circumstance that well-preserved specimens should be rare, and found chiefly in beds containing silicates capable of injecting their cavities. On the other hand, the circumstance that fragments of Eozoon are abundant in the limestone is one of the best possible proofs that we are dealing with a calcareous organism. It would be interesting to describe and figure a number of specimens in our collections illustrating these points ; but to do so would reciuire an extensive illustrated memoir, for which neither space nor means are at present available. I observe, in conclusion of this part of the subject, that in any highly crystalline limestone we can hope to find well-preserved fossils only when their cavities and pores have been filled with some enduring siliceous mineral ; but, on the other hand, that porous fossils, once so infiltrated, become imperishable. It still remains to consider shortly new facts bearing on the structure of Eozoon and its possible biological affinities. 3 It \» 11 curious cdiiicideiiue Uiat Dr. JohiiHtoii-Lavis Ims deHcrilied in tlie July number of tliis Journal, Ui« aqiieoux depoHitioii at ordinary temperature of crystals - of pyroxene and Iiurnblende, in cavities and creviccH of bones included in nu asli-bed of recent date, and in presence of calcite. apatite, and fluoride of cnlciuiii, as in the Qrenville Series. This is a modern instance analogous to that suggested above. Animal Nature of Eozoon Canadense. 69 III. STRUCTURAL AND BIOLOGICAL. In recent years I have been disposed to attach more importance than formerly to the general form and macroscospical characters of Eozoon. The earlier ex- amples studied were, for the most part, imbedded in the limestone in such a manner as to give little definite information as to external form ; and at a later date, when Sir William Logan employed one of his assistants, Mr. Lowe, to quarry large specimens at Grenville and Cote St. Pierre, the attenjpt was made to secure the most massive blocks possible, in order to provide large slabs for showy museum specimens. More recently, when collections have been made from the eroded and crumbling surfaces of the limestone in its wider exposures, it was found that specimens of moderate size had been weathered out, and could, either naturally or by treatment with acid, be entirely separated from the matrix. Such specimens sometimes showed, either on the surfaces or on the sides of cavities and tubes penetrating the mass, a confluence of the lamime, constituting a porous cortex or limiting structure. Specimens of this kind were figured in 1888,' and I was enabled to add to the characters of the species that the original and proper form was " broadly turbinate with a depression or cavity above, and occasionally with oscula or pits penetrating the mass." The great flattened masses thus seemed to represent confluent or overgrown individuals, often contorted by the folding of the enclosing beds. The openings or oscula penetrating .some of the larger specimens of Eozoon may perhaps be compared with the central canal in the modern Cai'penteria. There are also in well-preserved specimens certain constant properties of the calcite and serpentine layers. The former are continuous, and connected at intervals, so that if the siliceous filling of the chambers could be Geological Magazine, and HiiHeuni Memoir. 70 Canadian Record of Science. removed, the calcareous portion would form a continuous skeleton, while the serpentine filling the chambers, when the calcareous plates are dissolved out by an acid, forms a continuous cast of the animal matter filling the chambers. This cast of the sarcodous material, when thus separated, is very uniformly and beautifully mammillated on the surfaces of the laminre, and this tuberculation gradually passes upward into smaller chambers, having amoeboid outlines, and finally into rounded chamberlets. It is also a very constant point of structure that the lower lamina; of calcite are thicker than those above, and have the canal-systems larger and coarser. There is thus in the more perfect specimens a definite plan of structure on the large scale. Fio. 6. — Diagram of typical mode of arrangement of canals and tubuli in a lamina of Eozodn Canadeiue. (Magnified.) The normal mode of mineralization at Cote St. Pierre and Grenville is that the laminae of the test remain as calcite, while the chambers and larger canals are filled with serpentine of a light green or olive color, and the finer tubuli are injected with dolomite. It may also be observed that the serpentine in the larger cavities often shows a banded structure, as if it had been deposited in successive coats, and the canals are sometimes lined with a tubular film of serpentine, with a core or axis of dolomite, which also extends into the finer tubuli of the surfaces of the lamima This, on the theory of animal origin, is the most perfect state of preservation, and ~^. Animal Nature of Eozoon Canadensc. 71 i.'i it equals anything I liave seen in calcareous organisms of later periods. Tliis state of perfection is, however,' naturally of infreiiuent occurrence. The finer tubuli are rarely perfect or fully infiltrated. Even the coarser canals are not infrequently imperfect, while the laminje themselves are sometimes crumpled, crushed, faulted, or penetrated with veins of chrysotile or of calcite. In some instances the calcareous laminse are replaced by dolomite, in which case the canal-systems are always imperfect or obsolete. The lamime of the ' test itself are also in some cases replaced by serpentine in a flocculent form. At the opposite extreme are specimens or portions of specimens in which the chambers are obliterated by pressure, or occupied only with calcite. In such cases the general structure is entirely lost to view, and scarcely appears in weathering. It can be detected only by microscopic examination of slices, in parts where the granular structure or the tubulation of the calcite layers has been preserved. All pahcontologists who have studied silicified fossils in the older rocks are familiar with such appearances. It has been alleged by Miibius and others that the canal-systems and tubes present no organic regularity. This difficulty, however, arises solely from imperfect specimens or inattention to the necessary results of slicing any system of ramifying canals. In Eozoon the canals form ramifying groups in the middle planes of the laminte, and proceed at first almost horizontally, dividing into smaller branches, which ultimately give ofl' brushes of minute tubuli running nearly at right angles to the surfaces of the lamina, and forming the extremely fine tubulation which Dr. Carpenter regarded as the proper wall. In my earlier description I did not distinguish this from the canal-system, with which its tubuli are inwardly continuous; Dr. Carpenter, however, understood this 72 Canadian Record of Science. arrangement, and has represented it in his figures' (see also Fig. 6). It is evident that in a structure like this a transverse or oblique section will show truncated portions- of the larger tubes apparently intermixed with others much finer and not continuous with them, except verjr oo o '^ O O^ ft o ^ r'i ^ o /-^ a ^ Fio. 7. — Cross section of minute tubuli, about 5 microms. in diameter.. (Magnified.) rarely. Good specimens and many slices and decalcified' portions are necessary to understand the arrangement. This consideration alone I think entirely invalidates the- y.vO:,'9.V6P'0'-o'- ■■■:^:;fi^,- ■:-:<:> ■:■:■:■■■:. Fio. 8. — Cross section of similar tubuli, more higlily magnified, and' showing granular character of the test. (From camera tracings. ) criticisms of Mobius, and renders his large costly figures of little value, though his memoir is, as I have elsewhere- shown, liable to other and fatal objections.' > Ann. and Mag. Nat. Hist, ser. 4, xiii, p. 456, tigs. 3, 4. 3 Museum Memoir, pp. 50 tt uq. Animal Nafiin of J^ozoon Canadense. 73 1;^ It has been pretended that the veins of chrysotile, when parallel to the laminse, cannot be distinguished from the minute tubuli terminating on the surfaces of the •iaminfe. I feel confident, however, that no microscopis*-. who has seen both, under proper conditions of preservation •and study, could confound them. The fibres of chrysotile are closely appressed parallel prisms, with the optical properties of serpentine. The best preserved specimens of the " proper wall" contain no serpentine, but are composed of calcite with extremely minute parallel cylinders of dolomite about five to ten microms. in -tliameter, and separated by spaces greater than their own 'diameter (see my comparative figure, "Dawn of Life," p. 106 ; also Figs. 5. 6). In the rare cases where the cylinders are filled with serpentine they are, of course, still anore distinct and beautiful. At the same time I do not •doubt that observers who have not seen the true tubula- .tion may have been misled by chrysotile v^ when these iringe the laminie. Mobius, for instance, figures the true -and false structure as if they were the same. Protest should here l)e made against that mode of treat- ing ancient fossils which regards the most obscure or defaced specimens as typical, and those better preserved -as mere accidents of mineral structure. In Tertiary Nummulites injected with glauconite, it is rare to find the tubuli perfectly filled, except in tufts here and there, jet no one doubts that these patches represent a con- tinuous structure. I have remarked on previous occasions that the calcite ■c' '"tuting the laniinfe of Eozooon often has a minutely ; .. ^r appearance, different from that of the surround- ing limestone. This is, I presume, the "dusty" appear- ance referred to by Dr. Bonuey. Under a high power it resolves itself into extremely minute dots or fiocculi, .somewhat uniformly diffused. Whether these dots are particles of carbon, iron, apatite, or siliceous matter, or 74 Canadian Bccord of Science. the remains of a porous structure, I do not know ; but similar appearances occur in the calcareous fossils con- tained in altered limestones of later date. Wherever they occur in crystalline limestones supposed to be organic^ the microscopist should examine them with care. I have sometimes by this appearance detected fragments of Eozoon which afterwards revealed their canals. I have not space here to notice late observations on Archjeospherinje and other objects supposed to be organic found in pre-Cambrian rocks in Canada and in Europe. They afford, however, to some extent, corroborative evi- dence in favour of Eozoon. Supposing a probability to be established of the animal nature of Eozoon, we should naturally expect to detect links of connection between it and fossils known to us in the succeeding geological formations. We have, however,, here to make allowance for the probability that an organ- ism so very ancient may differ materially from any of its successors, and may probably be a synthetic or generalized type, or present en)bryonic characters. Analogy might also justify the supposition that it might be represented in later times by smaller as well as more specialized forms. In this connection, also, the probable warmth and shallow- ness of the Laurentian ocean, and its abuntlance in calcium carbonate and in carbonaceous matter, probably organized,, should be taken into account. It should also be noted that the formations next in ascending order are of a character little likely to preserve organic marine forms of the " l)enthos " or ground-living gioup. We might thus expect a gap in our record Itetween the fauna of the Gren- ville Series and that of the next fo.ssiliferous formations. Logan naturally compared his earlier specimens with the Stromatoportb so abundant in the Ordovician and Silurian Limestones; and in this he was justified, for, whatever may be the ultimate judgment of naturalists as to these problematical fossils, and whether they are Animal Nafnrc of Eozobn Canadom. 75 referred to I'rotozcii or to Hyclrozoa, or, as seems more likely, are divided between tiie two, they resemble Eozoon ill general .structure and mode of accumulation of cal- careous matter, and occupied a similar place in nature. My own conclusion, in discussing the microscopic struc- tures of the sitecimcns of Eozoon, was that they were prolml)ly those of l'rot(»zoa allied to those Foraminifera with tiiick .sui)pleniental skeleton' which had been described by Dr. Carpenter. At the same time, I sus- pected that those Stromatoporoids, like Crenostroina, which pos.sesses tliick lamina' penetrated l»y ramifying tubes, might lie allied to the Laurentian fo.ssil. Dr. Car- penter regarded the structures as com1)ining in some respects those of llotaline and Nummuline Foraminifera, and ably, and as I think conclusively, defended this view when attacked.* The llotaline type of Foraminifera has since that time been traced by Cayeux and Matthew far down into the pre-Canibrian rocks. The Nummuline type is not known so early. As to the canal-bearing Stroniatojioroids, none of them show the fine tubulation, though some have radiating and branching canals. Kecent students of the Stroniatoporic seem disjiosed to refer them to Hydrozoa,^ a conclusion prol>altle in the ca.se of some of the forms (especially those sjnnous ones incrusting shells), but doubtful in the ca.se of others, and more par- ticularly the (jldest of all, belonging to the genus Crypto- zoon of Hall, and Archicozoon of Matthew,* the structure of which seems, so far as known, to consist of very thin primary lamina' with a sujiplemental tubulated skeleton re.sembling that of the genus Lqffnsia, and which must, I think, be regarded as foramini feral. In any ca.se, whether the.se primitive forms are Protozoa or rudimen- .tary Hydroids, they reach back in time nearly as far as J Cali.'ariiia, etc 2 Ann. ami Mag Nat. Hist., Inc. eil. ' Nicliolson, Motiogi'nplis Pala'ontograjiliical Society. * Bulletin Nat. Hi»t. Survey of New Ikunswick, 1804-95. 76 Canadian Record of Science. Eozoiin, and are e(]ually massive and abundant, and may Ije regarded as analogous to it in magnitude, habitat, mode of urowth, and function in nature. These later discoveries are gradually widening the hori- zon of paheontologists in the direction of the dawn of life, and the studies of those who trace liackward the history of the Invertebrates of the Palu'ozoic seas are demanding more and more the discovery of earlier forms than those yet known to complete the chain of life,* The field is a difficult one to cidtivate, and demands l)oth labour and patience, but it holds forth the prospect of great discoveries, and it has already bec(nne the duty and interest of palii'ontologists to extend their incpiiries as far l)ack as the Laurentian in the search for Eozoic life. In this respect the study and discussion of Eozoijn have not ,been without u.se, in directing attention to the possi- l»ility of finding organic remains in the older crystalline rocks, to the danger of confounding tliem in their peculiar condition with merelv mineral structures, to the state of jtreservation of organic remains in the older formations, and t(» the origin and significance of the large deposits of limestone, dolomite, hydrous silicates, iron ore, graphite, and a[)atile, laid up in certain horizons of the Eozoic rocks. Questions of this kind have been greatly a