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 The Geognosy of the Appalachians and the Origin of Crystalline Books. 
 
 ADDRESS 
 
 TO Tllli 
 
 AMERICAN ASSOCIATION 
 
 Foil THE 
 
 ADVANCEMENT OF SCIENCE. 
 
 BY 
 
 THOMAS STERRY HUNT, IL.D. 
 
 / 
 
 ON RKTlRIXa K.U.M TI.,.: OKKIOK OK VmHlUKST OV U.K ASSOCIATION. 
 INDIANAPOLIS, AUGUST 10, 1871. 
 
 PrintiMl i.. advance iron, the Associaliuii Number of II,,.. Aiiiericau ^ 
 
 Naturalist. 
 
 SALKM : 
 
 NATURALISTS' AGENCY. 
 
 1871. 
 
SPECIAL NOTICE. 
 
 We shall issue a 
 
 DOUBLE NUMBER 
 
 OF THE 
 
 AMERICAN NATURALIST, 
 
 to be called tlie 
 
 ASSOCIATIOISr jS^UMBER, 
 
 as 800U as possible after tlie adjournment of the 
 
 MEETING OP THE ASSOCIATION. 
 
 This double number will contain the papers read before the 
 
 Natural History Sections, 
 
 and will be furnished to subscribers as Nos. 8 and 9 of Vol. 5. The price of single 
 
 copies will be 
 
 FIFTY CENTS. 
 
 Orders are solicited by the 
 
 PltOPltlKTOKS OF THJE WAT lilt AXIST, 
 
The Geognosy of the Appalachians and the Origin of Crystalline Rooks. 
 
 ADDRESS 
 
 TO THE 
 
 AMERICAN ASSOCIATION 
 
 FOR THE 
 
 ADVANCEMENT OF SCIENCE, 
 
 ERRATUM 
 
 For foot notes on page 45, read 
 
 * Pogg. Annal. Ixvili, 319. 
 
 t Amer. Jour. Sci., II, xvi, 218. 
 
 Printed In advance from tlie Association Number of the American Naturalist. 
 
 SALEM : 
 
 NATURALISTS' AGENCY. 
 
 1871. 
 
 
i'a%rwvKT^m 
 
 SPECIAL NOTICE. 
 
 We shall issue u 
 
 DOUBLE NUMBER 
 
 OF TUB 
 
 AMERICAN NATURALIST, 
 
 to be culled the 
 
 ■ reif'm<xws&%Ks.'Xi:¥.-siSMiifA^vm«i 
 
 yL 
 
 FIFTY CENTS. 
 
 Orders are so lie I ted by the 
 
 PIIOPJRAKTOIISI OF THE ]«ATlJltAI.I»T, 
 
 
The Geognosy of the Appalachians and the Origin of Orystalline Books. 
 
 ADDRESS 
 
 TO THE 
 
 AMERICAN ASSOCIATION 
 
 FOR THE 
 
 ADVANCEMENT OF SCIENCE 
 
 BY 
 
 THOMAS STERRY HUNT, LL.D. 
 
 ON KETIRING FROM THE OFFICE OF PRESIDENT OF THE ASSOCIATION. 
 INDIANAPOLIS, AUGUST IC, 1871. 
 
 Printed In advance (Vom tlie Association Number of the American Naturalist. 
 
 SALEM : 
 
 NATURALISTS' AGENCY. 
 
 1871. 
 
SALEM PRESS, 
 
 Comer of Liberty and Derby Streets, 
 
 Salem, Mass. 
 
 L 
 
ADDRESS 
 
 or 
 
 THOMAS STERRY HUNT, 
 
 ON RETIRINQ FROM 
 
 Tlic oliice of President of the American Association for the Advancement of Science. 
 
 [Dellverea at the 20tli meeting of the Association, at Imllaiiapolls, August lOtli, 1871.] 
 
 Gentlemen of the Ameuican Association fou the Advance- 
 ment OF Science : — 
 
 In coming before you this evening my first duty is to announce 
 tlie death of Professor William Chauvci;*. This sad event was 
 not -anexpected, since, at the time of his election to the presidency 
 of th'> Association, at the close of our meeting at Salem in August, 
 18G9, it was already feared that failing health would prevent him 
 from meeting with us at Troy, in .1870. This, as you are aware, 
 was the case, and I was therefore called to preside over the Asso- 
 ciation in his stead. In the ;,atumn of 18G9, he was compelled by 
 illness to resign his position of Chancellor of the Washington Uni- 
 versity of St. Louis, and in December last died at the age of filly 
 years, leaving behind him a record to which science and his country 
 may point with just pride. During his connection of fourteen years 
 with the Naval Academy at Annapolis he was the chief instrument 
 in building up that institution, which he left in 1859 to take the 
 chair of Astronomy and Mathematics at St. Louis, where his re- 
 markable qualities led to his selection, in 18G2, for the post of 
 
 (3) 
 
4 ADDKESa OK T. STKUKY HINT. 
 
 cliiuiocllor of the miivcrsitv, wliich he lllletl with «;rout credit nnd 
 UHcriiliicH.s u]) to tlic time of liis i'csi<j;iiiiti()n.* It is not Inr iiic to 
 pronounce Uw euh)}iy of I'rofesHor Cimuvt'net, to speak of his pro- 
 found :ittiiimnentH in tiHtrononiy and iniitlieniiitics, or of liis puli- 
 lislied works, whicii have iUrciidy tiiken rank as classics in tlie 
 literature of tliese Hcienees. Others more familiar wifli liis Held 
 of laltor may in pr<)|>er time and piiice iitlempt tlie task. All who 
 knew him can however join with me in testityinj>- to his excellencies 
 as a man, an instructor an<l a friend. In his assiduous devotion 
 to scientific studies he did not neglect the more elegant arts. I)nt 
 was a skilful nmsician, and posscHsed of great general culture and 
 retinement of taste. In his social and moral relations he was 
 marki'd by rare elevation and |)urity of character, and hns left to 
 the world a standard of excellence in every relation of life which 
 few can hope to attain. 
 
 In accordance with our cnstoiu it becomes my duty in (piitting 
 the honorable position of president, which T have tilled for the 
 past year, to address you upon some theme which shall l»c ger- 
 mane to the objects of the Association. The presiding otlicer, as 
 you are aware, is generally chosen to represent alternately one of 
 the two great sections into which the members of the" Association 
 are supposed to be divided ; viz., the students of the natural-his- 
 tory sciences on the one hand, and of the physico-mathematicMl 
 and chemical sciences on the other. The arrangement by which. 
 in our organization, geology is classed with the natural-history 
 division, is based upon what may fairly be challenged as u some- 
 what narrow conception of its scope and aims. While theoretical 
 geology investigates the astronomical, physical, chemical nnd bio- 
 logical laws which have presided over the development of our 
 earth, and while practical geolog}' or geognosy studies its natural 
 history, as exhibited in its physical structure, its mineralogy and 
 its paleontology, it will be seen that this comprehensive science is 
 a stranger to none of the studies which are included in the plan of 
 our Association, but rather sits like a sovereign, commanding in 
 turn the services of all. 
 
 As a student of geology, I scarcely know with which section of 
 the Association I should to-day identify myself. Let me endeavor 
 
 * Amer. .Jour. Sci., Ill, i, 233. 
 
GEOGNOSY OK TIIK APPALACHIANS. 
 
 nitlicr to nu'diiitc Ix'twccn the two, iiiid nlunv yoii Homowlmt of tlio 
 two-fold iiHjJi'ct wliicli jiycolojLfical scii-ncc picsi'iits, when vifweil 
 respectively from the staiid-poiiitH of imtmal histoi-y jind of chem- 
 istry. I can hardly do this better than in the discnssion of a 
 suhjcct which for the last <;encrati()n has alfordcd sonic of the most 
 fas('iiiatin<>,- and perplexing pr()i)lcnis for our ^colo<j;i(al students; 
 viz., the history of tiic ;i;rcat A|>paiacliian nionntaii, chain. Xo- 
 where else in the world has a mountain system of sncii ireo«'rai)hi- 
 eal extent and such fi;eolo<«;ical complexity been studied by such ft 
 nunil)er of zealous and learned investif^ators, and no other, it nuiy 
 be conlidcntiy asserted, has fin'nished such vast and imi)ort!int 
 residts to gcolojiical science. The laws of mountain structure, as 
 revealed in the A])palacliians by the labors of the brothers Henry 
 1). and William 15. Rogers, of Lesley and of Hall, have given to 
 the world the l)asis of a correct system of orot-raphic ireoIoLrv,* 
 and many of the obscure <>;eolo,u;ical |)rol)lems of Europe become 
 plain when read in the light of our American experience. To 
 discuss even in the most summary manner all of the (juestions 
 which the theme suggests, would be a task too long for the present 
 occasion, but I shall endeaAor to-night in the first place to bring 
 before you certain facts in the history of the physical structure, 
 the mineralogy and the paleontology of the Api)alacliians ; and 
 in the second place to discuss some of the i)hysical, chemical and 
 bioh)gical conditions which have presided over the formation of 
 the ancient crystalline rocks that make ni) so large a portion of 
 our great eastern mountain system. 
 
 J. The Geofjnosy of the Ax>pahiclnan Si/stem. 
 The age and geological relations of the crystalliiu' stratified rocks 
 of eastern North America have for a long time occupied the at- 
 tention of geologists. A section across northern New Yoi-k, from 
 Ogdensbnrg on the St. Lawi'cnce to Portland in Maine, shows the 
 existence of three distinct regions of nnlike crystalline schists. 
 These are the Adirondacks to the west of Lake ('liami)lain, the 
 Green Mountains of Vermont, and the White IMountains of New 
 Hampshire. The lithological and mineralogical ditlcrences between 
 the rocks of these three regions are such as to have attracted 
 the attention of some of the earlier observers. p:aton, one of the 
 
 * Amer. Jour. Sci., II, xxx, 406. 
 
6 
 
 ADDRESS OF T. STKUUY HUNT. 
 
 fouiulers of American fjcolofjy, at least as early as IH.'J-J. distin- 
 guisheil in his Cieolojiical Text book (2(1 edition) between the gneiss 
 of the Adirontlacks and that of the Green Monntains. Ailopting 
 the then received divisions of i)rnnary, transition, secondary and 
 tertiar}' rocks, he divided each of these series into three classes, 
 which he named carboniferons, (jnartzose and calcareons ; meaning 
 by the lirst schistose or argillaceous strata such as, according to 
 him, might include carbonaceous matter. These three divisions in 
 fact corresponded to olay, sand, and lime-rocks, and were sui)posed 
 by him to be repeated in the same onler in each series. This was 
 apparently the lirst recognition of that law of cycles in sedimenta- 
 tion upon which I afterwardr- insisted in 180.'$.* Without, so far as 1 
 am aware, defniing the relations of the Adirondacks, he referred to 
 the lowest or carboniferous division of the primar}- series, the crys- 
 talline schists of the Green Mountains, while tiie quartzites and 
 marbles at their western base were made the (juai'tzose and calca- 
 reous divisions of this primary series. The argillites and sandstones 
 lying still farther westward, but to the east of the Hudson Kiver, 
 were regarded as the fu'st and second divisions of the transition 
 series, and were followed by its calcareous division, which seems to 
 have included the limestones of the Trenton group ; all of these 
 rocks being supposed to dip to the westward, and away from the 
 central axis of the Green Mountains. Eaton does not aj)pear 
 to have studied the AVhite INIountains, or to have considered their 
 geological relations. The^- were, however, clearly distinguished 
 from the former by C. T. Jackson in 1844, when, in his report on 
 the geology of New IIami)shire, he described the White Moun- 
 tains as an axis of primary granite, gneiss and mica-schist, over- 
 laid successively, both to the east and west, by what were designa- 
 ted by him Cambrian and Silurian rocks ; these names having, since 
 the time of Eaton's publication, been introduced by English geol- 
 ogists. While these overlying rocks in IVIaiue were unaltered, he 
 conceived that the corresponding strata in Vermont, on the western 
 side of the granitic axis, !iad been changed by the action of intrusive 
 serpentines and intrusive (juartzites, which had altered the Cam- 
 brian into the Green JNlountain gneiss, and converted a portion of 
 the fossiliferous Silurian limestones of the Champlain valley into 
 white marbles. t Jackson did not institute any comjiarison be- 
 
 * Amer. Jour. Sci., II. xxxv, 100. 
 
 t Geology of New H!iinj)t-hire, 1(10-102. 
 
^•'5^, (listin- 
 ' the gneiss 
 Adoi)tiii<r 
 lulary and 
 't' classes, 
 ; nieaninir 
 'ording to 
 visions in 
 supposed 
 TJiis was 
 
 Mlinieiita- 
 
 litr as J 
 foiTed to 
 the crys- 
 ites and 
 id calca- 
 •dstones 
 
 1 liiver, 
 uisition 
 I'cms to 
 <" tliese 
 oni the 
 appear 
 d their 
 iiished 
 ort on 
 MoiMi- 
 
 o\er- 
 signa- 
 since 
 gool- 
 'd. ho 
 stern 
 iisive 
 ^am- 
 )ii of 
 into 
 
 be- 
 
 GEOGXOSY OF THE APPALACHIANS. 7 
 
 tween the rocks of the White Mountains and those of the Adiron- 
 daclvs ; but the Messrs. Rogers in tlie same year, 1844, published 
 an essay on tlie geological age of the White Mountains, in which, 
 while endeavoring to show their Upper Silurian age, they speak of 
 them as having been hitherto regarded as consisting exclusively 
 of various niodihcations of granitic and gneissoid rocks, and as be- 
 longing '• to the so-called primary periods of geologic time." * 
 They however considered that these rocks had rather the aspect of 
 altered paleozoic strata, and suggested that they might be, in part 
 at least, of the age of the Clinton division of the New York 
 system ; a view which was supported by the presence of what were 
 at the time regarded by the Messrs. Rogers as organic remains. 
 Subsequently, in 1847,t they announced that they no longer consid- 
 ered these to be of organic origin, without however retracting 
 their opinion as to the paleozoic age of the strata. Reserving to 
 another i)lace in my address the discussion of the geological age 
 of the White Moimtain rocks, I proceed to notice briefly the dis- 
 tinctive characters of the three groups of crystalline strata just 
 mentioned, which will be shown in the seciuel to have an impor- 
 tance in geology beyond the limits of the Appalachians. 
 
 I. The Adirondack or Laurentide Series. The rocks of this 
 series, to which the name of the Laurentian system has been given, 
 may be described as chiefly firm granitic gneisses, often very 
 coarse-grained, and generally reddish or grayish in color. They 
 are frecpiently hornblendic, but seldom or never contain nmch mica, 
 and the mica-schists, (often accompanied with staurolite, garnet, 
 andalusite and cyanite), so characteristic of the White Mountain 
 series, are wanting among the Laurentian rocks. They are also 
 destitute of argillites, wliicli are found in the other two series. 
 The quartzites, and the pyroxenic and hornblendic rocks, asso- 
 ciated witii great fornuitions of crystalline limestone, with graph- 
 ite, and innnense beds of magnetic iron ore, give a peculiar 
 character to portions of the Laurentian system. 
 
 II. The Green Mountuin Series. The (luartzo-feldspathic rocks 
 of tliis serk's are to a consideral)le extent represented by a iine- 
 grained petrosilex or eurite, though they often assume the form of 
 a true gneiss, which is ordinarily more micaceous than the typical 
 
 * Amer. Jour. Sci., 11, 1, 411. 
 tibul, n, V, lie. 
 
8 
 
 ADDRESS OF T. STERKY HUNT. 
 
 Laurcntian gneiss. The eoarse-orainod, porpliyritic, reiUlish vari- 
 eties common to the latter are wanting in the Green Monntains, 
 where the gneiss is general!}' of pale greenish and grayish hnes. 
 Massive stratified diorites, and epidotic and chloritic rocks, often 
 more or less schistose, with steatite, dark colored serpentines and 
 ferriferous dolomites and magnesites also characterize this gncissic 
 series, and arc intimately associated with beds of iron ore, generally 
 a slaty hematite, but occasionally magnetite. Chrome, titanium, 
 nickel, copper, antimony and gold are frequently met Avith in this se- 
 ries. The gneisses often pass into schistose micaceous quartzites, 
 and the argillites. which abound, frequently assume a soft, unctuous 
 character, whit-li has acquired for them the name of talcose or na- 
 creous slates, though analysis shows them not to be magnesian, 
 but to consist essentially of a hydrous micaceous mineral. They 
 arc sometimes black and gra})hitic. 
 
 III. The White Mountain Series. This series is characterized 
 l)y the ])redominance of well defined mica-schists interstratified 
 with micaceous gneisses. These latter arc ordinarily light colored 
 from the presence of white feldspar, and, though generally fine in 
 texture, are sometimes coarse-grained and porphyritic. They are 
 less strong and coherent than the gneisses of the Laurcntian, and 
 pass, through the i)redominance of mica, into mica-schists, which 
 are themselves more or less tender and lVial)le, and present every 
 variety, from a coarse gneiss-like aggregate down to a fine-grained 
 schist, which passes into argillite. The micaceous schists of this 
 series are generallj- much richer in mica than those of the preced- 
 ing series, and often contain a large proporticm of well defined crys- 
 talline tables belonging to the species nuiscovite. The cleavage 
 of these micaceous schists is generally, if not always, coincident 
 with the bedding, but the plates of mica in the coarser-grained 
 varieties arc often arranged at Aarious angles to the cleavage and 
 bedding-i)lane, showing that they were developed after sedimenta- 
 tion, by crystallization in the mass ; a circumstance whicii distin- 
 guishes them from rocks derived from the ruins of these, which art> 
 met with in more recent series. The White jNEonntain rockf^ also 
 include beds of micaceous quartzite. The basic silicates in this 
 series are represented chiefly by dark colored gneisses and schists, 
 in which hornblende takes the place of mica. These pass occi- 
 sionally into beds of dark hornblende-rock, sometimes holding 
 garnets. Beds of crystalline limestone occasicually occur in the 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 9 
 
 Tliev 
 
 ing 
 the 
 
 schistH of the Wliite Mountain serins, and are sometimes aeeom- 
 panied by pyroxene, garnet, idoerase, si)hene and grapliite, as in 
 the eorresponding roelvs of the Laurentian, wliieli tliis series, in its 
 more gneissic portions, closely resembles, though apparently dis- 
 tinct geognostieally. The limestones are intimately associated 
 with tiie highly micaceous schists containing staurolite, andalusite, 
 cyanitc and garnet. These schists are sometimes highly phnnl>ag- 
 inous, as seen in the graphitic mica-schist holding garnets in 
 Nelson, New Hampshire, and that associated with cyanite in Corn- 
 wall, Conn. To this third series of crystalline schists belong the 
 eoncretionar}^ granitic veins abounding in ber}'!, tourmaline and 
 lepidolite, and occasionally containing tinstone and columbite. 
 (Iranitic veins in the Laurentian gneisses I'rcHiuently contain tour- 
 maline, but have not, so far as yet known, yielded the other min- 
 eral species just mentioned. * 
 
 Keei)ing in mind the characteristics of these three series, it will 
 be easy to trace them southward by the aid of the concise and ac- 
 curate descrii)tions which I'rof. II. I). Rogers has given us of the 
 rocks of Pennsylvania. In his report on the geology of this state 
 he has distinguislied three districts of various crj'stalline schists, 
 which are by him included together under the name of gneissic 
 or hypozoic rocks. Of these districts the most northern, or the 
 South Mountain belt, to the northwest of the Mesozoic liasin, is 
 said to be the continuation of the Highlands of New York and New 
 .Tersey, which, crossing the Delaware near P^aston, is continued 
 southward through I'ennsylvania and INIaryland into Virginia, 
 where it appears in the Blue Kidge. Tiie gneiss of this district 
 in I'ennsylvania is described as differing considerably from that of 
 the southernmost district, being massive and granitoid, often horn- 
 blendic, with nmch magnetic iron, but destitute of an}' consider- 
 able beds of micaceous, talcose or chloritic slate, which mark the 
 rocks of the southern district. These characters are suflicient to 
 show that the gneiss of this northern district is lithologically as 
 well as geognostieally identical with that of tlie Highlands, and 
 l)elongs like it to the Adirondack or Laurentian system of crys^tal- 
 linc rocks. The gneiss of the middle district of Pennsylvania, to 
 the south of the Mesozoic. but north of the Chester valley, is de- 
 scribed by Rogers as resembling that of the South Mountain or 
 
 ♦Hunt. Notes on Granitic Kocks; Amer. Jour. Sci., Ill, i, 182, 
 
10 
 
 ADDRESS OF T. STERRY HUNT. 
 
 northern district, and to consist diiefly of white feldspatliic and 
 dark liornblendic gneiss, with very little mica, and witli cr3'stalline 
 limestones. 
 
 The gneiss of the third or sontliern district, that lying to the 
 south of the Montgomerj^ and Chester valleys, comes from l)eneath 
 the Mesozoic of New Jersey about six miles northeast of Trenton, 
 and stretching southwestward, occupies tlie southern border of 
 Pennsylvania, extending into Delaware and Maryland. It is sub- 
 divided by Rogers into three belts ; the first or southernmost 
 of these, passing through Philadelphia, consists of alternations of 
 dark hornl)lendic and highly micaceous gneiss, with abundance 
 of mica-slate, sometimes coarse-grained, and at other times so line- 
 grained as to constitute a sort of whet-slate. To the northwest- 
 ward the strata become still more micaceous, with garnets and 
 beds of hornblende slate, till we reach the second subdivision, 
 which consists of a great belt of highly talcose and micaceous 
 schists, with steatite and serpentine, and is in its turn succeeded 
 b}'^ a third, naiTow belt resembling the less micaceous members 
 of the first or southernmost subdivision. The micaceous schists of 
 this region abound in staurolite, gurnet, cj^anite and corundum, 
 and are traversed by numerous irregular granitic veins containing 
 beryl and tourmaline. All of these characters lead us to refer the 
 gneiss of this southern district to the third or White Mountain 
 series, with the exception of the midi.e subdivision, Avhich presents 
 the aspect of the second or Green Mountain series. 
 
 Above the hypozoic gneisses Rogers has placed his azoic or 
 semi-metamorphic series, Avhich is traceable from the vicinity of 
 Trenton to the Schuylkill, along the northern boundary of the 
 southern hypozoic gneiss district. This series is supposed by 
 Rogers to be an altered form of the primal sandstones and slates, 
 and is described as consisting of a feldspatliic quartzite or eurite, 
 containing in some cases porphyritic beds with crystals of feldspar 
 and hornblende, together with various crystalline schists ; includ- 
 ing in fact tlie whole of the great serpentine belt of Montgomery, 
 Chester and Lancaster counties, with its steatites, hornblendic, 
 dioritic, chloritic, and micaceous schists (often garnet-bearing), 
 together with a band of argillite, affording roofing-slates. With 
 this great series are associated chrolnic and titanic iron, and ores 
 of nickel and copper. Veins of albite with corundum also inter- 
 sect this series near Unionville. We are repeatedly assiu-ed by 
 
GEOGNOSY OF TIIK APPALACHIANS. 
 
 11 
 
 Rogers that these rocks so much resemble the un{lerl,yiii<? hypozoic 
 gneiss, sis to he readily eonfouiuled with tbom ; and when oonipared 
 with the latter, as displayed in the southern district, it is dilHcult 
 to believe tliat we have in this so-called azoic or metaniorphic 
 series of the Montgomery and Chester valleys, anything else than 
 a repetition of these same crystalline schists which have l)een de- 
 scribed along their southern boundary, representing the Green 
 Mountain and the White Mountain series. We thus avoid the dif- 
 ficulty of supposing that we have in this region two sets of scr- 
 pentinic rocks, and two of mica-schists, lithologically similar, but 
 of widely different ages, — a conclusion highly improbable. It 
 should be said that Rogers, in accordance with the notions then 
 generally received, looked upon serpentine as an eruptive rock, 
 which had altered the adjacent strata, converting the mica-schists 
 into steatitic and chloriti(! rocks. 
 
 This so-called azoic series, according to Rogers, underlies the au- 
 roral limestone of Pennsjdvania, thus apparently occu})ying the 
 horizon of the primal paleozoic division or Potsdam series. We 
 find, however, in his report on the geology of the state, no satis- 
 factory evidence of the identity of the two series. On the con- 
 trary, a A'er3' diffei-ent conclusion would seem to follow from certain 
 facts there detailed. Tlie azoic or so-called metaniorphic primal 
 strata are said to have a very uniform nearly vertical dip, or with 
 high angles to the southward, while the niicaceoiis and gneissic 
 strata of the northern subdivision of the southern district of so- 
 called hypozoic rocks, limiting these last to the south, present 
 either minute local contortions or wide gentle undulations, Avith 
 comparatively moderate di[)s, for the most part to the northward. * 
 From this, I think we may infer that the nearly vertical strata must 
 be, in truth, older underlying rocks belonging, not to the paleozoic 
 system, but to our second series of crystalline schists. We con- 
 clude, then, that while the gneisses to the northwest, and probably 
 those along the southeast rim of the Mesozoic basin of Pennsyl- 
 vania are Laurentian, the great valley southward to the Delaware 
 is occupied by the rocks of the Green Mountain and AVhite j\Ioun- 
 tain series. The same two types of rocks, extending to the north- 
 east, are developed about New York city, in the mica-sdiists of 
 Manhattan and the serpentines of Staten Island and lloboken ; 
 
 * Rogers, Geology of Pennsylvanin, I, pp. 69-74, and 154-158. 
 
12 
 
 ADDRESS OF T. STEllRY IIITNT. 
 
 while in the rnn<?e of the IIi<ihlaiKls, the gneiss belt of the South 
 Mountain crosses tlic Hudson river. 
 
 The three series of <>iu'issic' rocks wliich we have (listin<iuiHhe(] 
 in our section to the northward have, in soutlieastcrn New York, 
 as in Pennsylvania, been grouped togetlier in the primary system, 
 and may thence all be traced into western New En<iland, In Dr. 
 Percival's geological report and map of Connecticut, pul>lisiied in 
 1840, it will be seen that he refers to the gneiss of the Ilighlauds 
 two gucissic aicas in Litchfield county ; the one occupying i)arts of 
 Cornwall and Kllsworth. and the other extending from Torrington, 
 northward through Winchester, Norfolk and Colcbrooke into Berk- 
 shire county, Massachusetts. Farther investigations may confirm 
 the accuracy of Percival's identification, and show the Lam'cntian 
 age of these New England gneisses, a view which isai)))arcntly sup- 
 ported by the mineralogical characters of some of the rocks in this 
 region. Emmons informs ns that priniaiy limestones witli graj)hite, 
 (perhaps Lanrentian), are met with in the Iloosic range in Massa- 
 chusetts east of the Stockbridge (Taconic) limestones. 
 
 The rocks of the second series are tracealtle from southwestern 
 Connecticut northward to the (ireen INIountains in Vermont, and 
 the micaceous schists and gneisses of the third (n- AVhite Mountain 
 series are found both to the east and the Avest of the Mesozoic val- 
 ley in Connecticut and INIassachnsetts. They also occupy a con- 
 siderable area in eastern Vermont, where they are separated from 
 the White Mountain range by an outcrop of rocks of the second 
 series. To the southeast of the Wliite Mountain!-., along our line of 
 section, the same mica-schists and gneisses, often with very mod- 
 erate dips, extend as far as Portland, Maine, where they are inter- 
 rupted by the ontcropping of greenish chloritic and chromiferous 
 schists, in nearly vertical beds, which appear to belong to the sec- 
 ond series. 
 
 I find that the strata of the second series appear from beneath 
 the Carboniferous at Newport, Rhode Island, in a nearly Acrtical 
 attitude, and also in the vicinity of Boston and Brighton, Saugus 
 and Lynnfield. Their relations in this region to the gneisses with 
 crj'stalllne limestones of Chelmsford, etc., Avhich I have refeiTcd to 
 the Lanrentian series,* have yet to be determined. 
 
 We have already mentioned that the crystalline rocks of Penn- 
 sylvania pass into Maryland and Virginia, where, as H. D. Rogers 
 
 * Ainer. Joui\ Sci., II, xlix, 75. 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 18 
 
 informs us, they appear in the mountains of tlie Blue l?i(l}ijo. It 
 remains to be seen whetlier the tluee types wliich we have pointed 
 out in Pennsylvania are to be recognized in tliis region. A great 
 belt of crystalline schists extends from Virginia through Nortli 
 and Sontli Carolina, and into eastern Tennessee, where, according 
 to Safford, these rocks underlie the Potsdam. It is easy. IVom the 
 reports of Liel)ei- on the geology of South Carolina, to identify in 
 this state the two types of tlie (Jreen Mountain and White Moun- 
 tain series. The former, as described I)}' him, consists of talcose, 
 chloritic and ei)idotic schists, with diorites, steatites, actinolite- 
 rock and serpentines. It may be noted that he still adheres to the 
 notion of the erui)tive origin of the last three rocks, which the ob- 
 servations of Ennnous, Logan and myself in the Clreen Mountains 
 have shown to be untenable. These rocks in South Carolina gen- 
 erally dip at very high angles. The great gneissic area of Anderson 
 and Abbeville districts is described by Lieber as consisting of line- 
 grained grey gneisses with micaceous and liornl)lendic schists, and 
 is cut l»y numerous veins of pcgmutiti', holding garnet, tourmaline 
 and beryl. These rocks, which have the characters of the White 
 Mountain series, appear, from the incidental observations to be 
 fonnd in Lieber's reports, to belong to a higher group than the 
 chloritic and serpcntinic series, and to dip at comparatively mod- 
 erate angles. 
 
 Professor Ennnous, whose attention was early turned to the ge- 
 ology of western New England, did not distinguish between the 
 three types which we have defined, but, like Rogers in Pennsylva- 
 nia, included all the crystalline rocks of that region in the primary 
 system. It is to him, however, that we owe the first correct no- 
 tions of the geological nature and relations of the Green Moiuitains. 
 These, he has remarked, are often made to include two ranges of 
 hills belonging to different geological series. The eastern range, 
 including the lloosic Mountain in Massachusetts, and Mount 
 Mansfield in Vermont, he referred to the primary ; which he de- 
 scribed as including gneiss, mica-schist, talcose slate and horn- 
 blende, with beds and veins of granite, limestone, serpentine and 
 trap. He declared, moreover, that there is no clear line of de- 
 marcation among the various schistose primary rocks, and cited, 
 as an illustration, the passage into each other of serpentine, stea- 
 tite and talcose schist. His description of the crystalline rocks of 
 this range will be recognized as comprehensive and truthful. 
 
14 
 
 ADDRESS OK T. STEKUY HUNT. 
 
 To the west of tlie hills of pruniuy schist, ho placed his Taconic 
 system, named from the Tacoiiie hills, whieh run from north to 
 south alonjj; the boundary line of New York and Massachusetts and 
 form a ran<i;c parallel with the (jreen Mountains. The lower por- 
 tions of the Taconic system, according to Knunons, are schistose 
 rocks made up from the ruins of the primary schists which lie to 
 the east of them. Thus the talcose schists of IJerkshire are said 
 to be regenerated rocks, belonging to the newer system, l)ut show- 
 ing the color and texture of the older talcose schists from which 
 they were formed. How far this is true of these particular strata 
 may be a question, for there is reason to believe that Ennnons 
 inchided among his Taconic rocks some beds belonging to the older 
 crystalline series of the (Jreen Mountains ; yet it is not less true that 
 the possibility of derived rocks of this kind is one which has been 
 too much overlooked by geologists. Emmons elsewhere remarks 
 that Avhile the talcose slates of the primary are associated with 
 steatite and with hornblende, these are never found in the Taconic 
 rocks, and also, that epidote, actinolite, titanium (rutile), etc., 
 which are characteristic minerals of the primary, are wanting in 
 the Taconic system. 
 
 The statements of Emmons on this point, were snfliciently ex- 
 plicit ; he included in the primary system all of the crystalline 
 schists of the Green Mountains, except certain talcose and mi- 
 caceous beds, Avhich he supposed to be composed from the ruins 
 of similar strata in the primary, and to constitute, with a great 
 mass of other rocks, the Taconic S3'stem ; which was, in its turn, 
 unconformably overlaid by the Potsdam sandstone and Calciferous 
 sandrock of the New York system. His views have, however, been 
 misunderstood b}' more than one of his critics ; thus, Mr. Marcou, 
 while defending the Taconic system, makes it to include the three 
 groups just mentioned, viz. : I, the Green Mountain gneiss ; II, the 
 Taconic strata as defined by Emmons, and III, the Potsdam sand- 
 stone,* tluis uniting in one S3'stem the cr3^stalline schists and the 
 overlying uncrystalline fossiliferous sediments, in direct opposition 
 to the plainl}-^ expressed teachings of Emmons, as laid down in his 
 report on the Geology of the Northern District of New York, and 
 later, in 184G,| in his work on the Taconic sj'stem. 
 
 In the geological survey of the stnte of New York, the rocks of 
 
 *Pioc. Host. Nat. Hist. Soc, Nov. 0, 18iil, and Anier. Jour. Sci., II, xxxiii, 282. 
 tLoc. cit., p. 139, and Agricult., N. York, I, 53. 
 
OKOONOSV OF THE APrALACHIANS. 
 
 15 
 
 the Chiimplnin division, including the strata from the base of the 
 Potsdiiui Handstone to the Hunnnit of the Loraine or Hudson River 
 siuiles, hud, by his colleagues, been looked upon as the lowest of 
 the paleozoic system. Professor Emmons, however, was led to 
 regard the very dissimilar strata of the Taconic hills as constituting 
 a distinct and more ancient series. A similar view had been held by 
 Eaton, who placed, as v/a have already seen, above the crystalline 
 schists of the (ireen Mountains, his primary (juartzose and calcare- 
 ous fornuitions, followed to the westward by transition argillites and 
 sandstones, which latter appear to have corresponded to the I'ots- 
 dam sandstone of New York. Emmons, however, gave a greater 
 form and consistency to this view, and endeavored to sustain it by 
 the evidence of fossils, as well as by structure. The Taconic sys- 
 tem, as defined by him, may be briefly described as a series of 
 uncrystalline fossiliferous sediments reposing unconformable' on 
 the crystalline schists of the Green Mountains, and partly made 
 up of their ruins ; while it is, at the same time, overlaid inicon- 
 formal y by the Potsdam and Calciferous formations of the Cham- 
 plain division, and constitutes the true base of the paleozoic 
 column, — thus occupying the position of the British Cambrian. 
 
 Although he claimed to have traced this Taconic system through- 
 out the Appalachian chain from Maine to North Carolina, it is 
 along the confines of Massachusetts and New York that its devel- 
 opment was most minutely studied. He divided it into a lower 
 and an upper division, and estimated its total thickness at not less 
 than thirty thousand feet, consisting, in the order of deposition, 
 of the following members : — 1. Granular quartz ; 2. Stockbridge 
 limestone ; 3. Magnesian slate ; 4. Sparry limestone ; 5. Roofing- 
 slate, graptolitic ; G. Silicious conglomerate ; 7. Taconic slate ; H. 
 Black slate. The apparent order of sui)erposition differs from this, 
 and it Avas conceived by Professor Emmons that during the accu- 
 mulation of these Taconic rocks, the Green Mountain gneiss, which 
 formed the eastern border of the basin, was gradually elevated so 
 as to bring successively the older members above the ocean from 
 which the sediments were being deposited. From this it resulted 
 that the upper members of the sj'stem, such as the black slates, 
 were confined to a very narrow belt, and never extended far east- 
 ward ; although he admits that denudation may have removed large 
 portions of these upper beds. At a subsequent period, a series of 
 parallel faults, with upthrows on the eastern side, is supposed to 
 
IC 
 
 AKDKK.HS OV T. 8TKIIHY HUNT. 
 
 have broken thn Htnita, j^ivtMi tluMii jin oastwiinl dip, and cuuHcd the 
 newel' beds to pass Hiiecessively beneath th(( older ones, thn.s pro- 
 (hiein<j; an ap/KiiwHtlif inrcrtcd sitrraHrn'on, and niaUinfjj tlieir present 
 seeniiiifj; order of superposition eoinpU^telv decu'ptive. In speaking 
 of this supposed arrangement of the nu'inliers of his 'I'aconie sys- 
 tem, Emmons aUnch'd to them as " inverted strata ;" wliih^ by Mr. 
 Mareou, the strata were said to be "overtiu'ned on each »'u\o of the 
 erystalline and erni)tive roeks wineli ocetujy the eentre of tlu' chain, 
 proihicing tiuis a fan-siiaped structure," eti-.* I liav(! elscwiiere 
 shown tliat tliis notion, thougli to some extent conntenanci'd by 
 his vague and inaccurate use of terms, was never entertained 
 l)y Emmons, whose own view, ns defined in liis Taconic JSystem (p. 
 17),t is tlnit just explained. 
 
 Tiie view of Emmons tliat tliere exists at the western base of 
 tlie (Jreen Mountains, older fossiliferous series ujiderlying the 
 Potsdam, met with general opposition from American geologists. 
 In May, 18-14, II. D. Rogers, in his address as President, before the 
 American Association of (Geologists, then met at Washington, crit- 
 icised this view at length, ami referred to a section from Stock- 
 bridge, ^lassaclmsetts, to the Hudson lliver, made by W. H. Rogers 
 and himself, and by them hlid before the American Philosophical 
 Society in January, 1841. They then nniintained that the (pmrtz- 
 rock of the Iloosic range was Potsdam, the Berkshire marble iden- 
 tical with the bine limestone of the Hudson valley, and the asso- 
 ciated micaceous and talcose schists, altered strata of the age of the 
 slates at the base of the Appalachian system ; that is to say, pri- 
 mal in the nomenclature of the Pennsylvania survey. 
 
 In 1843 Mather had asserted the Champlain age of the same 
 crystalline rocks, and claimed that the whole of the division was 
 there represented, including the Potsdam, the Hudson River group, 
 and the intermediate limestones. J The conclusion of Mather was 
 cited with approbation by Rogers, who apparently adopted it, and 
 
 ♦Comptcs Ucndus de I'Acad., IJII. 804. 
 
 tSeo my iiivtlicr discussion of tlic matter, Amcr. Jour. Sci., II, xxxii, 427, xxxiii, 
 1;$,"), 281. It is by an oversight tliat I liave. in the latter vohinie, page 13(i, represented 
 B.arrande as sliaring the misconception of Mareou, altliougli his language, without 
 careful scrutiny, would lead us to such a conclusion. In fact in the Bull. Soc. Geol. de 
 France (11, xviii, 2(>1), in an elaborate study of tlie Taconic question, Barrande heads 
 a section thus. " lienversemeiit conqu pour tout tin nysteme," and then proceeds to show 
 that the rcnrernement or overturn is only apparent, by explaining, in the language of 
 Emmons, the view alre.idy set forth above. 
 
 X Geology of the Southern District of New York, p. 438. 
 
OEOflNOSY OF THE APPALACHIANS. 
 
 17 
 
 caiiHcd tlio 
 S thus pro- 
 oir prosoiit 
 II Hpoiikiiif? 
 iconio Hys- 
 lilc l.y Mr. 
 side of fill) 
 ' till' cliuiii, 
 elsewhere 
 iiiinceil by 
 iiti'i'tuined 
 Si/tifcm (p. 
 
 rn base of 
 il.ying the 
 zoologists. 
 bcCoro the 
 gtoM, crit- 
 )in Stock- 
 H. Rogers 
 losophical 
 le (piartz- 
 rblo iden- 
 tlic asso- 
 igo of the 
 say. pri- 
 
 tho same 
 isiou was 
 er group, 
 ither was 
 I it, and 
 
 427, xxxiii, 
 ein-psented 
 e, without 
 c. IJool. (le 
 iiulc heads 
 Is lo show 
 mgiiage of 
 
 cluimed that Ilitchoock hold a siiiiilar view. It will bo scon that 
 thoHo geologists thus uiiilod in one groiii), the sohists of the Iloosic 
 range (regarded by Knnnons as primary), with those of the Tu- 
 conio range, and referred both to the age of the Chaniplain divis- 
 ion, the whole of which was supposed to be included in the group. 
 
 In the same address Professor Uogors raised a very important 
 question. Having referred to the I'otsdam sandstone, which on 
 Lake Chami»lain forms the base of the paleozoic Hysteni, he in- 
 quires, "Is this formation then the lowest limit of our Appalachian 
 masses generally, or is the system expanded downward in other 
 districts by the introduction beneath it of other conformable sed- 
 imentary rocks?" He then proceeded to state that from the Sus- 
 quehanna River, southwostward, a more complex series appears at 
 th'.f base of the lower limestone than to the north of the Schuylkill, 
 and ill some parts of the lUue Ridge he includes in the primal di- 
 vision (beneath the Calciforous saiidrock) "at least four indepen- 
 dent and often very thick deposits, constituting one general group, 
 in which the Potsdam or white sandstone (with Scolithus) is the 
 second in descending order." This sandstone is overlaid by many 
 hundred feet of ai'enaceous and ferriferous fucoidal slate, and un- 
 derlaid by coarse sandy shales and flagstones ; below which, in 
 Virginia and East Tennessee, is a series of heterogeneous con- 
 glomerates, which rest on a great mass of crystalline strata. The 
 accuracy of these statements is confirmed by Salford, who, in his 
 recent report on the geology of Tennessee (1869), places at the 
 base of the column a great series of crystalline schists, apparently 
 representatives of those of southeastern Pennsylvania. Upon 
 these repose what Satford designates as the Potsdam group, in- 
 cluding, in ascending order, the Ococee slates and conglomerates, 
 estimated at 10,000 feet, and the Chilhowee shales and sandstones. 
 2,000 feet or more, with fucoids, worm-burrows and Scolithus. 
 These are conformably overlaid by the Knoxville division, con- 
 sisting of fucoidal sandstones, shales, and limestones, the latter 
 two holding fossils of the .age of the Calciforous sandrock. It is 
 noteworthy that these rocks are greatly disturbed bj' fixults, and 
 that in Chilhowee Mountain the lower conglomerates are brought 
 on the east against the Carboniferous limestone, by a vertical dis- 
 placement of at least 12,000 feet. The general dip of all these 
 strata, including the basal crystalline schists, is to the southeast. 
 
 The primal paleozoic rocks of the Blue Ridge were then by Rog- 
 
 AMER. NAT., ASSOC. NUMBER. 2 
 
IH 
 
 ADDUKSS OK T. aTKUUV HUNT. 
 
 orH, lis now by SiiUhnl, lookod upon uh wliolly of I'otsdsim m^c, in 
 eluding tlio ScolitlniH Hiindstonc as ii Hnl)ordin!itt' nioinl)i>r, ho Unit 
 the strata iMMieath tliis wero still rogiirdcd u.s lu'lon«fing to tlu? New 
 York Hystouj. Ilenee, while Rogers inciuires wlu'ther the Taeonie 
 system "iniiy not along the western border of Vermont and Mas- 
 saehiisetts inelude also scjuie of the huikIv and slaty strata here 
 spoken of as lying l»eueath the I'otsdam sandstone"* ho would still 
 embrace these lower strata in the Champlain division. 
 
 Thus wo see that at an early period tho rocks of the Taconic 
 system were, by Kogers and Mather, referred to the Chauiplain divi- 
 sion of the New York system, a eonchision wliieh 1ms l»een sus- 
 tained by subse(|uent oi»servations. IJcfore diseiissing these, and 
 their somewhat involved history, we may state two (luestions which 
 present themselves in connection with this solution of the problem. 
 First, whether the Taconic system, as defined l)y Kinmons, includes 
 the whole or a part of tlu^ C'liMuiplain division ; and second, wheth- 
 er it embraces any strata older or newer than Ww iniMiibers of this 
 portion of tho New York system. With reference to the tirst 
 question it is to bo remarked that in their attempts to compare the 
 Taconic rocks with those of the CHiampliiln division as seen farther 
 to the west, observers were led by litliological similarities to iden- 
 tity the upper members of the latter with certain portions of the 
 Tac<jnic. In fact, the Trenton limestone, witii the lltiea slates 
 and the Loraine or Hudson River shales, making together the upper 
 half of the Chaini)lain division (in which Kimnons moreover in- 
 cluded the overlying Oneida and iVIedina conglomerates and sand- 
 stones), have in New York an aggregate thickness of not less than 
 three or four thousand feet, and oiler many litliological rescra- 
 blances to the great mass of sediments at the western base of the 
 Green Mountains, to which the name of Taconic had been applied. 
 It is curious to fmd that Emmons, in 1812, referred to the Medina 
 the Red sandrock of the east shore of Lake Champlain, since shown 
 to be Potsdam ; and, moreover, placed the Sillery sandstone of the 
 neighborhood of t^uebec at the sununit of the Champlain division, 
 as the representative of the Oneida conglomerate ; while at the 
 same time he noticed the great resemblance which this sandstone, 
 with its adjacent limestones, bore to similar rocks on the contines 
 of Massachusetts, already referred by him to the Taconic system, t 
 
 * Amer. Jour. Sci., t, xlvii, 152, ir>3. 
 
 fGcol. Northei'u District of New York, pp. 121, 125. 
 
(IE0ONO9V OF THE APPALACHIANS. 
 
 19 
 
 Tliin view of KiiiinonH ns to tho (iu('l»e(! rocks was luloptcd l)y 
 Sir Williiim Loij;iiii, when, u fisw yours iiltcrwanls, Ik* ln'j^iin to 
 study tlu! goolof^y of that rej;H)n. Tho Haiul.stone of Sillory wuh 
 (IcHcribod by him as corrospoiidiiif^ to tlio Onuida or Sluiwaiif^imk 
 eon<j;loinorate, wliilo tiu) liincHtoim.s and .shales of thn vicinity, 
 wliich were supposed to iind»'rli»' it, were regarded as llic rcprc- 
 sciilatiycs of tlic Trenton, I'tica, and Hudson liivcr forniali(jns. * 
 IJy followin;^ tlieso rocks alon<; tiu> western base of the Appalach- 
 ians into Vermont and Massaithusetts, they were found to bo a 
 continuation of the Taconic system, which Sir William was thus 
 led to refer to the upper half of the Chumplain division, as had 
 already been done by I'roft'ssor Adams in IMI7.t As retfards the 
 crystalline strata of the Appalachians in this region, he, however, 
 rejected the view of Emmons, and nuuntained that put forward by 
 the Messrs. Rogers in 1841, viz., that these, instead of being older 
 rocks, were but these sanie upper formations of the C'hamplain 
 division in an altered condition; a view which was maintained dur- 
 ing several years in all of the publications of those connected with 
 the geological survey of Canada. 
 
 This conclusion, so far as regards the ago of the unaltered fos- 
 siliferous rocks from Quebec to Massachusetts, was sui)i)osod to 
 be conlirmed by the evidence of organic remains found in them in 
 Vermont. Mr. Eunnons had described as characteristic (»f the 
 upper part of the Taconic system, two crustaceans, to wiiicli he 
 gave the names of Atojxt trilineatus and EHiidocfphalHs cmiphnidPH ; 
 the other fossils noticed by him being graptolites, fucoids, and what 
 were apparently the marks of annelids. In 1847 I'rofessor James 
 Hall, in the lirst volume of iiis raleontology, declared the Atops of 
 Enunous to l)e identical with Triarthi'iiH {('dliiinoK') liccl-il, a char- 
 acteristic fossil of the Utica slate ; while the EUiptocephalus was 
 referred by him to the genus Olenns, now known to belong to the 
 primordial fauna of Sweden, where it is found in slates lying l)e- 
 neath the orthoceratite limestone, and near the base of the paleo- 
 zoic series. Although, as it now appears, the geological horizon of 
 the Olenus slates was well known to Ilisinger, this author in his 
 classic work, Lcthma Suecica, published in 1837, represents, by 
 some unexphiined error, these slates as overlying the orthoceratite 
 
 *Gc()l. Survey of Canada, 1S17-18, pp. 27, 57; and Amer. .Tour. Sci., II, ix, 13. 
 t Aincr. Jour. Sci., II, v, lOiJ. 
 
20 
 
 ADDUESS OF T. STERRY HUNT. 
 
 limestone, which is the equivalent of the Trenton limestone of the 
 Champlain division. Ilence, as Mr. Barrande has remarked, Hall 
 was justified by the authority of Hisinger's publislied work in as- 
 signing to the Olenns slates of Vermont a position above tiiat lime- 
 stone, and in placing them, as he then did, on the horizon of the 
 Hudson River or Lorainc shales. The double evidence atfonled by 
 these two fossil forms in the rocks of \'^crmont, served to confirm 
 Sir William Logan in placing in the upper part of the Champlain 
 division the rocks which he regarded as their stratigraphical equiv- 
 alents near Quebec ; and which, as we have seen, had some years 
 before been by Emmons himself assigned to the same horizon. 
 The remarkable compound graptolites which occur in the shales 
 of Pointe Levis, opposite C^uebcc, Avere described b}' Professor 
 James ILall in the report of the Geological Survey of Canada for 
 1857, and were then referred to the Hudson River group ; nor was 
 it until August, 1860, that Mr. Billings described from the lime- 
 stones of this same series at Pointe Levis a number of trilo])ites, 
 among which were several species of Agnostus, Dikelocophalus, 
 Bathyurus, etc., constituting a fauna whose geological horizon he 
 decided to be in the lower part of the Champlain division. 
 
 Just previous to this time, in the Report of the Regents of the 
 University of New York for 1859, Professor Hall had described and 
 figui'cd by the name of Olenus, two species of trilobites from the 
 slates of Georgia, Vermont, which Ennnons had wrongly referred 
 to the genus Paradoxides. They were at once recognized by Bar- 
 rande, who called attention to their primordial character, and thus 
 led to a knowledge of their true stratigraphical horizon, and to the 
 detection of the singular error in Hisinger's book, already noticed, 
 by which American geologists had been misled.* Thoy have 
 since been separated from Olenus, and by Professor Hall referred 
 to a new and closely related genus, which he has named Olenellus, 
 and which is now regarded as belonging to tiie horizon of the Pots- 
 dam sandstone, to which we shall presently advert. 
 
 Farther studies of the fossiliferous rocks near Quebec showed 
 the existence of a nia'is of sediments estimated at about 1200 
 feet, holding a numerous fauna, and corresponding to a great 
 development of strata about the age of the Calciferous and Chazj* 
 formations, or more exactly to a formation occupj'ing a position 
 
 *For the correspondence on this matter between Barrande, Logan and Hall, see 
 Amer, Jour. Sci., II, xxxi, 210-2iJ«. 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 21 
 
 between these two, and constituting, as it were, beds of passage 
 between them. In this new formation were inehuled tlie grapto- 
 lites ah'eady described by Hall, and the numerous Crustacea and 
 brachiopoda described by Billings, all of which belong to the Levis 
 slates and limestones. To these and their associated rocks Sir 
 William Logan then gave the name of the Quebec group, including, 
 besides the fossiliferous Levis formation, a great mass of overlying 
 slates, sandstones and magnesiau limestones, hithei'to Avithout fos- 
 sils, which have been named the Lauzon rocks, and the Sillery 
 sandstones and shales, which he supposed to form the summit of 
 the group, and which had attbrded onl}- an 01)olella and two species 
 of Lingula ; * the volume of the whole group being about 7000 feet. 
 
 The paleoutological evidence thus obtained by Billings and by 
 Hall, ])oth f'om near Quebec and in Vermont, led to the conclusion 
 that the strata of these regions, so much resembling the ui)por 
 members of the Champlain division, were really a great tlcvelop- 
 ment, in a modified form, of some of its lower portions. Their 
 apparent stratigraphical relations were explained by Logan by the 
 supposition of "an overturned anticlinal fold, Avith a crack and a 
 grout dislocation running along tin- suirrrnit. Ivy »iilch ihe (Quebec 
 group is brought to overlie the Hudson Kiver group. Sometnnes 
 it may overlie the overturned Utica formation, and in Vermont 
 points of the overturned Trenton appear occasionall}' to emerge 
 from l)eneath the overlap." lie, at the same time, declared that 
 ■'from the physical structure alone, no person would suspect the 
 lu'Ciik that must exist in the neighborhood of Quebec, and, without 
 the evidence of fossils, every one would be authorized to deny it."t 
 
 The rocks from western Vermont, which had furnished to Hall 
 the species of Olenellus, have long been known as the Red sand- 
 rock, and as we have seen, were by Emmons, in 1842, referred to 
 the age of the ^Medina sandstone, a view which the late Professor 
 Adams still maintained as late as 1.S47. 1 In the mean time 
 Emmons had, in IS");"), declared this rock to represent the Cal- 
 oiferous and I^)tsdam formations, the brown sandstones of Bur- 
 lington and Charlotte, Vermont, I»eing referred to the latter. § 
 
 * See Billings, Paleozoic Fossils of Cnnadft, p. C9. 
 
 tI>ogan'8 letter to narrniKlo, Amer. Jour. Sci.. II. xxxi,2is. The true date of this 
 letter was DeceinlK'r .'!lst, 18110. but, by a misprint, it is made 1831. 
 t Adams, Amer. .Tour. Sci.. II. v, 108. 
 s Enimous. American Geology, II, 128. 
 
22 
 
 APDRESS OF T. STERRY HtTNT. 
 
 This conclusion was confirmed bj^ Billings, who, In 1861, after vis- 
 iting the region and examining the organic remains of the Red 
 sandrock, assigned to it a position near the horizon of the Pots- 
 dam.* Certain trilobites found in this Rod sandrock by Adams 
 in 1847, were by Hall recognized as belonging to the European 
 genus Conocephalns {=. ConocephaUt.es and Conocoryphe), whose 
 geological horizon was then undetermined. t The formation in 
 question consists in great part of a red or mottled granular dolo- 
 mite, associated Avith beds of fucoidal sandstone, conglomerates 
 and slates. These rocks were carefully examined by Logan in 
 Swanton, Vermont, where, according to him, the}' have a thick- 
 ness of 2200 feet, and include toward their base a mass of dark 
 colored shales holding Olenellus Avith Conocephalites, Obolella, 
 etc. ; Conocephalites Teucer, Billings, being common to the shales 
 and the red sandy beds.| IMany of those fossils are also found at 
 Troy and at Bald Mountain, New York, where they accompany 
 the Atops of Emmons, now recognized by Billings as a species of 
 Conocephalites. 
 
 A similar condition of things extends northeastward along the 
 Appalachian region. On the south side of the St. Lawrence below 
 Quebec a great thickness of limestones, sandstones, and slates, 
 formerly referred to the Quebec group, is now regarded by Billings 
 as, in i^art at least, of the Potsdam formation ; Avhile on the coast 
 of Labrador, and in northern Newfoundland the same formation, 
 characterized by the same fossils as in Vermont, is largely devel- 
 oped, attaining in some parts, according to Murray, a thickness of 
 3000 feet or more. Along the northern coast of the island it is 
 nearly horizontal, and appears to be conformabl}' overlaid by about 
 4000 feet of fossiliferous strata representing the Calcifcrous sand- 
 rock and the succeeding Levis formation. 
 
 Mr. Billings has described a section from the Laurontian of 
 Crown Point, New York, to Cornwall, Vermont, from which it ap- 
 pears that to the eastward of a dislocation which brings up the 
 Potsdam to overlie the higher members of the Champluin division, 
 the Potsdam is itself overlaid, at a small angle, by a great mass of 
 limestones representing the Calcifcrous, and having at the summit 
 some of the characteristic fossils of the Levis formation. Next in 
 
 * Ainer. Jour. Sci., II, xxxii, 2;!2. 
 
 tlbiil.. II, xxxiii. ;i74. 
 
 t Geology of Canada, 1803, p. 261. 
 
 Aiiier. .Tour. Sci., II, xlvi, 221. 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 28 
 
 of 
 
 ascending order are not less than 2000 foet of limestones with 
 Trenton fossils (embracing probably the Chazy division) , while to 
 the east of this the Levis again appears, including the white Stock- 
 bridge limestones. * "We have here an evidence that the augmen- 
 tation in volume observed in the lower members of the Champlain 
 division in the Ai)palachian region extends to the Trenton, which 
 to the west of Lake Champlain is represented, the Chazy included, 
 by not more than 500 feet of limestone. The Potsdam, in the latter 
 region, consists of from .'iOO to 700 feet of sandstone holding Cono- 
 cephalites and Liugulella, and overlaid by 300 feet of magncsian 
 limestone, the so-called Calciferous sandrock. In the valley of the 
 Mississippi these two formations in Iowa, Missouri, and Texas. 
 are represented by from 800 to 1 300 feet of sandstones and mag- 
 ncsian limestones, while in the Black Hills of Nebraska, according 
 to Ilaydon, the only representative of those lower formations is 
 about one hundred feet of sandstone holding Potsdam fossils.t 
 
 In striking contrast to this it has been shown that along the 
 Appalachian range from Newfoundland to Tennessee these lower 
 formations are represented by from 8000 to 15000 feet of fossil- 
 iferous sediments. It has been suggested by Logan that these 
 Avidely dift'ering conditions represent deep-sea accunmlations on 
 the one hand, and the deposits from a shallow soa which covered a 
 submerged continental plateau, on the other ; the sediments in the 
 two areas being characterized by a similar fauna, though ditfering 
 greatly in lithological characters and in thickness. To this we may 
 add that the continental area, being probably submerged and el- 
 evated at interv.als, became ovei'lnid with bods which represent 
 only in a partial and imperfect majiner tlie great succession of 
 strata which Avere being accumulated in the adjacent ocean. | 
 
 In a paper which I hope to present to the geological section 
 during the present mooting of the Association it will be shown 
 from a study of tlie rocks of the Ottawa l)asin that the typical 
 Champlain division not only presents important paleontological 
 breaks, but evidences of statigraphic.al discordance at more tiian 
 one horizon over the continental area, which, as the result of 
 widely spread movements, might be supposed to be represented in 
 the Appalachian region. In the latter Logan has already observed 
 
 * Anicr. .Ti)ur. sci.. 227. 
 t Ibid.. H, XXV. 4;i!i, xxxi. 234. 
 : Ibid.. II, xlvi. 225. ,--^-- 
 
24 
 
 ADDRESS OF T. STERRY HUNT. 
 
 HI 
 
 Hi 
 
 that the absence of all but the highest beds of the Levis along the 
 eastern limit of the Potsdam, near Swanton, Vermont, while the 
 whole thickness of them appears a little farther westward, makes 
 it probable that there is a want of conformity between the two ; 
 and 1 have in this connection insisted npon the entire absence in 
 this locality of the Calciferous, which is met with a little farther 
 south in Ihe section just mentioned, as another evidence of the 
 same unconformity.* There are also, I think, reasons for sus- 
 pecting anotiier stratigraphical break at the summit of the C^nebec 
 group, in which case many problems in the geological structure of 
 this region will be nuich simplified. 
 
 It should be remembered that the conditions of deposition in 
 some areas have been such that accumulations of strata, corres- 
 ponding to long geologic periods, and elsewhere marked by strati- 
 grai)hical ])reaks, are arranged in conformable superposition ; and 
 moreover that movements of elevation and depression have even 
 caused great paleontologlcal breaks, which over considerable areas 
 are not marked by any apparent discordance. Thus the remarka- 
 ble break in the fauna between the Calciferous and the Chazy is not 
 accompanied by any noticeable discordance in the Ottawa basin, 
 and in Nel)raska, according to llayden, the Potsdam, Carbonifer- 
 ous, Jurassic and Cretaceous formations are all represented in 
 about 1200 feet of conformable strata.! In Sweden the whole 
 series from the base of the Cambririu to the sunnnit of the Upper 
 Silurian appears as a conformable sequence, while in North Wales, 
 altiiough tiiere is no apparent discordance from the base of the 
 Cambrian to the sunnnit of the Lingula flags, stratigraphical 
 breaks, according to Kamsay, probably occur both at the base and 
 the summit of the Tremadoc slates, I Avhich are considered equiva- 
 lent to the Levis formation. 
 
 We have seen that, according to Logan, a dislocation a little to 
 the north of Lake Champlain causes tlie (Quebec group to overlie 
 the higher members of the Cha-ni)lain division. The same uplift, 
 according to him, brings up, farther south, the Red sandrock of 
 Vermont, which to the west of the dislocation rests upon the up- 
 turned and inverted strata of various formations from the Calcif- 
 erous sandrock to the Utica and Hudson River shales. These 
 
 * Anier. Jour, Sci., II, xlvi, 225. 
 
 t Ibid., II. XXV, 440. 
 
 i Quai'. Geol. Journal, xix, page xxxvi. 
 
GEOGNOSY OP THE APPALACHIANS. 
 
 25 
 
 latter, according to him, are seen to pass for considcraljle distances 
 beneath nearly horizontal laycr.s of the lied sandrock, the Utica 
 slate, in one case, holding its characteristic fossil, Triarthrns lieckil. 
 This relation, which is well shown in a section at St, Albans, fig- 
 nred by Hitchcock,* was looked upon by Eninions and by Adams as 
 evidence that the Red sandrock was the representative of the Me- 
 dina sandstone of the* New York system. AVhen, however, the 
 former had recognized the Potsdam age of the sandrock, with its 
 Olenollus. Avliich ho supposed to be Paradoxides, this conditi(m of 
 things was conceived to be an evidence of the existence beneath 
 the Potsdam of an older and unconformable fossiliferous series 
 already mentioned. 
 
 The objections made bj-^ Emmons to Pogers's view of the Cham- 
 plain iige of the Taconic rocks were three-fold : first, the great dif- 
 ferences in lithological characters, succession and thickness, be- 
 tween these and the rocks of the Cliamplain division as previously 
 known in New York ; second, the supposed unconformable infra- 
 position of a fossiliferous series to the Potsdam ; and third, the dis- 
 tinct fauna which the Taconic rocks were supposed to contain. The 
 first of these is met by the fact now established that in the Appa- 
 lachian region, the Champlain division is represented by rocks 
 having, with the same organic remains, very different lithological 
 characters, and a tliickness ten-fold greater than in the tj'pical 
 Chami^lain region of northern New York. The second objection 
 has already been answei'ed l)y showing that the rocks which pass 
 beneath the Potsdam Jire really newer strata belonging to the upper 
 part of the division, and contain a characteristic fossil of the Uti- 
 ca slate. As to the third point, it has also been met, so far as 
 regards the Atops and EUiptocephalus, by showing these two 
 genera to belong to the Potsdam formation. If we inquire farther 
 into the Taconic fauna we find that the Stockbridge limestone (the 
 Eolian limestone of Hitchcock), which was placed by Emmons near 
 the base of the Lower Taconic, (while the Olenellus slates are 
 near the summit of the Upper Taconic), is also fossiliferous, and 
 contains, according to the determinations of Professor Hall, species 
 belonging to the genera Euomphalus, Zai)h. ontis, Stromatopora, 
 Ciiaetetes and Stictopora.f Huch a fauna would lead to the cou- 
 
 * Geology of Vermont, p. 374. 
 
 t Geology of Vermont, 419, and Amer. Jour. Sci., 11, xxxiii, 419. 
 
26 
 
 ADDRESS OF T. STERRY HUNT. 
 
 elusion that these limestones instead of being older, wei-e really 
 newer than the Olenellus beds, and that the apparent order of suc- 
 cession was, contrary to the supimsition of Emmons, the true one. 
 This eonohision was still farther confirmed by the evidence ob- 
 tained in 1H(\H by IMr, IJillings, who found in that region a great 
 number of characteristic species of the Levis formation, many of 
 them in beds immediately above or beloAT the white marl ties,* 
 which latter, from the recent observations of tiic Rev. Augustus 
 Wing in the vicinity of Jutland, A''ermont. would seem to l)e 
 among the upper l)eds of the I'otsdam formation. Thus wliile 
 some of the Taconic fossils belong to the Potsdam and Utica 
 formations, the greater number of them, derived from beds sup- 
 posed to be low down in the system, are shown to be of the age 
 of the Levis formation. Tliere is, therefore, at present, no evi- 
 dence of the existence, among tlie unaltered sedimentary rocks of 
 the western base of the AppMlachiaus in Canada or New England, 
 of any strata more ancient than those of the Champlain division, 
 to which, from their organic remains, the fossiliferous Taconic 
 rocks are shown to belong. 
 
 Mr. Billings lias, it is true, distiuguislied provisionally wliat he 
 has designated an upper and a lower division of the I'otsdam, and 
 has referred to the latter the Ked sandrock with the Olenellus 
 slates of Vermont, together with beds holding simihii- fossils at 
 Troy, New York, and along the straits of Bellisle in Labrador and 
 Newfoundland ; the upi)er division of the Potsdam being repre- 
 sented by the basal sandstones of the Ottawa basin and of the 
 Mississi2)pi valley .f In the present state of our knowledge of 
 the local variations in sediments and in their fauna dependent on 
 depth, temperature and ocean currents, Billings, however, con- 
 ceives that it would be i)rematui"e to assert that these two types of 
 the Potsdam do not rej)resent synchronous deposits. 
 
 The base of the Champlain division, as known in the Potsdam 
 formation of New York, of the Mississippi valley and the Appa- 
 lachian belt, does not, however, represent the base of the paleozoic 
 series in Europe. Tlie Alum slates in Sweden are divided into 
 two parts, an upper or Oleuus zone, and a lower or Conocoryphe 
 zone, as distinguished by Angelin. The latter is characterized by 
 
 * Arier. Jour. Sci., II, xlvi.227. 
 
 t Report Geol. of Canada, ISfiS-Ofi, p. 230. 
 
GEOGNOSY OK THE ArrALACIlIANS. 
 
 27 
 
 age 
 
 the goniis Paradoxides, wliicli also occupies a lower division in the 
 primordial paleozoic rocks of IJoheniia (Barraude's stage C), 
 the greater part of which are regarded as tlie equivalent of the 
 Olenus zone of Sweden and tiie Potsdam of North America. The 
 Lingula flags of Wales belong to the same horizon, and it is at 
 their Ijase, in strata once referred to the Lower Lingula flags, that 
 the Paradoxides is met with. These strata, for which Hicks and 
 Salter, in 1H0;>, proposed the name of the Menevian groni). are 
 regarded as corresponding to the lower division of the Alum slates, 
 and, like it, contain a fauna not yet recognized in the basal rocks 
 of the New York S3'stem. Wc here approach the debatable land 
 between the Cambrian and the Silurian of the British geologists. 
 The Cambrian, as originally claimed l»y Sedgwick, inclu(le(l in its 
 upper division the Middle and Upper Lingula flags, with the over- 
 lying Tremadoc slates, to the base of the Llaudeilo rocks, and may 
 be regarded as equivalent to the Potsdam, C'alciferous and Levis 
 formations ; while in the Lower Cambrian were embraced the Lower 
 Lingula flags and the Upper and Lower Longmynd rocks, corres- 
 ponding respectively' to the Harlech grits and the Llanberis slates. 
 A portion of the Cambrian has, however, l)een claimed for the 
 Silurian by Murchison, who draws the dividing line at the top of 
 the Longmynd rocks, leaving the three divisions of the Lingula 
 flags in the Silurian. Lj-ell, on the contrary, remarks that the 
 .Menevian beds, which were, on lithological grounds, made by 
 Sedgwick a part of the Lower Lingula flags, have been sliown 
 by Hicks and Salter to be ver}' distinct from these paleoutologi- 
 cally ; and, while he includes the Menevian in the Lower Cam- 
 brian, refers the whole of the Lingula flags to the Upper Cambrian. 
 Lyell therefore admits the Avhole of the Cambrian system as 
 oriijinally defined by Sedgwick, and the same classification is noAV 
 adopteil by Linarsson, in Sweden, where in Westrogothia, the Cam- 
 brian rocks, (resting unconformably on the crystalline schists to be 
 noticed farther on), ai'e overlaid conformably by the orthoceratite 
 lime&tones, which are by him regarded as forming the base of the 
 Siluri'iu, and as the equivalent of the Llandeilo rocks of Wales. 
 The total thickness of these lower rocks in Sweden, including the 
 representatives of the Lingula flags, the JNIenevian beds and an 
 underlying fucoidal (Eophyton) sandstone, is only three hundred 
 feet, while the first two divisions in Wales have a thickness of 
 five to six thousand, and the Harlech grits and Llanberis slates 
 
 i 
 
28 
 
 ADDUKSS OV T. STKUUY HUNT. 
 
 ili 
 
 11 
 
 (including the Welsh roollng-slivtes beneath) amount to eight thou- 
 sand feet additional. Recent researches show that these lower 
 rocks in Wales contain an altundant launa, extending downward 
 soinc^ 2S()() I'eet from the JNIeneviau to the very base of strata re- 
 garded as the representatives of tiie Ilarledi grits. The brachio- 
 poda of the Harlech beds appear identical with those of the Men- 
 evian, but new species of Conoccphalites^ Micwdiscits and Para- 
 doxidcs are met with, besides a new genus, Phitonia, allied to the 
 last mentioned. Mr. Hicks, to whom wc owe these discoveries,* 
 remarks, tliat the Menevian gives us, for the present, a well 
 marked paleontological horizon for the summit of the Cambrian, 
 corres])onding with the Lower Cambrian as defined by Sedgwick. 
 The Upper Cambrian in North America would thus include the 
 lower half of the Champlain division from the base of the Potsdam 
 to the sunnnit of the Levis (including perliaj)s the Chazy), while 
 the Lower Cambrian, (the Caml)rian of Murchison and liicUs) is 
 represented by the strata holding Paradoxides in Newfoundland, 
 New Brunswick and eastern Massachusetts. Although no strata 
 marked l»y these fossils have yet been found in the Appalachians, 
 it is not improbable that such may yet be met with. In May, 
 1861, I called attention to the fact tliat beds of (piartzose con- 
 glomerate at the base of the Potsdam in llemniingford, near the 
 outlet of Lake Champlain on its western side, contain fragments 
 of green and black slates, "showing the existence of argillaceous 
 slates before the dtiposition of the Potsdam sandstone." f The 
 more ancient strata, which furnished these slat}- fragments to 
 the Potsdam conglomerate, have perhaps been destroyed, or are 
 concealed, but they or their equivalents ma}- yet be discovered 
 in some part of the great Appalachian region. They should 
 not, however, be called Taconic, l)ut receive the prior designation 
 of Cambrian, unless, indeetl, it shall appear that the source of 
 these slate fragments was the more argillaceous beds of the still 
 older Huronian schists. Emmons regarded his Taconic sj'stem 
 as the e([uivalent of t)ie Lower Cambrian of Sedgwick, but when 
 iu 1842, Murchison announced that the name of Cambrian had 
 ceased to have any zoological significance, l)eing identical with 
 Lower Silurian,} Emmons, conceiving, as he tells us, that all 
 
 *Geol. M:(g., V, 30(!; jmil Hep. Brit. Assoc, ]8(58, i). 09; also Hiukness uuU Hicks in 
 Nature, Proc. Gcol. Soc, May 10, 1871. 
 t Amer. Jour. Sci., IF, xxxi. 404. 
 t Proc. Geol. Soc, London, HI, 042. 
 
GE0(JN08Y OF TIIK AI'I'ALACIIIANS. 
 
 29 
 
 Cambrian rockH were not Silurian, instead of niaintaiiiin<j: Sedg- 
 vvicl\'H name, wlneli willi the progress of paleontologicai study is 
 assuming a great zoological inii)ortan('e, devised the name of 
 Taeonie, as synonymous with Lower C'anihrian ;* although, as we 
 have seen, there is as yet no paleontological evidence to identify 
 any portion of the Taeonie; stra*^a with the well-delined Lower 
 Cambrian rocks of our eastern shores. 
 
 Tiie crystalline infra-Siliirian strata, to which the name of the 
 Iluronian series has been given Ity the (Jeological Siu'vey of Cana- 
 da, have sometimes been called Caml)rian from their resemblance 
 to certain rocks in Anglesea, which have been looked upon as al- 
 tered Cambrian. The typical Cambrian rocks of "Wales, down to 
 their base, are however uncrystalline sediments, and, as pointed out 
 by Dr. Bigsby in l«<j;5,f are not to be confounded witli tiie Iluron- 
 ian, which he regarded as ecpiivalent to the second division of the 
 so-called azoic rocks of Norway, the Umchicfrr or primitive 
 schists, wiiicli in that country rest unconformably on the primitive 
 gneiss (Urc/iwiss), and are in their turn overlaid unconformably by 
 the fossiliferous Cambriiin strata. This second or intermediate 
 scries in Norway is characterized by eurites, micaceous, chloritic 
 and hornblendic schists, with diorites, steatite and dark colored 
 serpentines, generally associated with chrome ; and abounds in ores 
 of copper, nickel and iron. In its mincralogical and lithological 
 characters, the Urschiefcr corresponds with what we have desig- 
 nated the second series of crystalline schists. It is, in Norway, 
 divided into a lower or quartzosc division, marked by a predomi- 
 nance of quartzites, conglomerates and more massive rocks, and 
 an upper and more schistose division. Macfarlane, who was fami- 
 liar with the rocks of Norwa}^ after examining both the Iluronian 
 of Lake Superior and the crystalline strata of the Green Moun- 
 tains, had already, in IH&2, declared his opinion that both of these 
 were representatives of the Norwegian Urschiefer, J thus anticipa- 
 ting, from his comparative studies, the conclusions of Bigsby. 
 
 The crystalline rocks of Anglesea and the adjacent part of 
 Caernarvon, which have been described and mapped by the British 
 Geological Survey as altered lowest Cambrian, are directly over- 
 laid by strata of the Llandeilo and Bala divisions, corresponding 
 
 * Emmons, Geol. N. District of New York, 162; and Agric. of New Yoik, I, 49. 
 tQuar. Jour. Geol. Soc, XIX, 36. 
 t Canadian Naturalist, VII, 125. 
 
80 
 
 ADDUKSS OK T. STKllllV HUNT. 
 
 to tho Trenton iind IhulHon River IbrnuitionH. If wc consnlt 
 llainsiiy's report on tlu; region, it will lu' founU that he speaks of 
 them as ''proital>ly Canihrian," and states as a reason for that 
 opinion, that tliey are connected by certain hi'ds of interniediato 
 litholojiical characters with strata of uiulonhted Cambrian a<;c.* 
 These, iiowever, as he achnits, present great local variations, and, 
 after carefully scannin<>; tlu^ whoh^ of the (nidencc; adduced, 1 am 
 inclined to see in it nothiiifj; more than the existence, in this 
 rej^ioii, of Cambrian strata made up from the ruins from the great 
 mass of pre-Cambrian schists, which are the crystalline rocks of 
 Anglesea. Such a phenomenon is repeated in numerous instances 
 in our North American rocks, and is the true explanation of many 
 supposed examples of passage from crystalline sciiists to uncrys- 
 talline setliuients. The Anglesea rocks are a highly inclined and 
 much contorted series of (juart/ose, micaceous, ehloritic and epi- 
 dotic schists, with diorites and dark coloreil chromiferouH serpen- 
 tines, all of which, alter a careful examination of them in the 
 colh'ctions of the (icological Survey of Great Britain, appear to 
 me identical with the rocks of the (ireen jMonntain or Iluronian 
 series. A similar view of their age is shared by riiillips and b\' 
 Sedgwick, in opposition to the opinion of the British survey. The 
 former asserts that the crystalline schists of Anglesea are '• below 
 all the Cambrian rocks ;"■)■ while Sedgwick expresses the opinion 
 that they are of '' a distinct epoch from the other rocks of the dis- 
 trict, and evidently older."]: 
 
 Associated with the fossiliferons Devonian rocks of .the lihine, 
 is a series of crystalline schists, similar to those just noticed, seen 
 in the Taunus, the Ilundsriick and the Ardennes. These, in opi)0- 
 sition to Dumoiit, who regarded them as belonging to an older 
 system, are declared by Kiinier to have resulted from a subse(iucnt 
 alteration of a portion of the Devonian sediments. § 
 
 Turning now to the Highlands of Scotland, Ave have a similar 
 series of crystalline schists, presenting all the mineralogical char- 
 acters of those of Norway and of Anglesea, Avhich, according to 
 Murehison and Giekie, are neither of Cambrian nor pre-Cambrian 
 age, but are ^younger than the fossiliferons limestones of the west- 
 
 *Geol. of N'oitli AVilles, pp. 145, 175. 
 
 t Jlunual of Cieology (18r>3) 89. 
 
 t (ieol. .Touinal fur 1815, WO. 
 
 § Naumauu, Geoguosie, 2d edition, II, 38.3. 
 
OKOUNOSV OK TIIK Al'l'ALACIIIANS. 
 
 31 
 
 ir 
 
 
 era coiiHt (iihoiit Ww horizon ol tlif L«^vi.s roniiiitioii) whicli hccui 
 to pass lH>iu>iitli tliein. Profossor Nifol,on (he coiitniry, iiiaintiiiiiH 
 that tills uppurcnt supor-poHition is *hie to iipiiftN, uiul that these 
 crystal lino schists iirc really older than either Caiiil)ri!iii or Silurian, 
 both of which :ii)pear to the west of them as uncryHtalliiie .sedi- 
 ments, resting on the Lanrentian. lie does not, however, con- 
 i'onnd tliesi' crvHtalline seliists of the Scottish l!i;j;iilands with the 
 Laurentian, from whi(rh they dilfer uiineralo<fic;dly, bnt re<>ards 
 them as a distinct series.* In the presenct; of the ditferences of 
 opinion which have been shown in this controversy, we may be 
 permitted to ask whether, in such a ease, strati<>;ra|»hical evidence 
 alone is to be relied upon. Ki'peated examples have shown that 
 the most skilful strati^rai)liists may be misled in studyiufj; the 
 structure of a disturlx'd re<>ion where there arc no organic remains 
 to guide them, or where unexpected faults and overslides may 
 deceive even the most sajfacious. I am convinced that in the 
 study of the crystalline schists, the persistence of certain mineral 
 characters nuist be relie<l upon as a j^uide, and that the; lanj^iuige 
 used by Delesse, in 1817, will be found susceptible of a wide ap- 
 plication to crystalline strata. "Hocks of the same aj^e have 
 most generally the same chemical and mineralogical composition, 
 and reciprocally', rocks having the same chemical composition and 
 the same minerals, associated in the same manner, are of the same 
 age."t 
 
 In this connection the testimonj' of Professor James Hall is to 
 the point. Speaking of the crystalline schists of the White Moun- 
 tain series, he says : — 
 
 " Kvery observing stmlent of one or two years experience in the 
 collection of minerals in the New England States, knows well that 
 he may trace a mica-schist of peculiar but varying character from 
 Connecticut, through central jMassachusetts, and thence into Ver- 
 mont and New Hampshire, by the presence of staurolite and some 
 other associated minerals, which mark with (he same unerring cer- 
 tainty the geological relations of the rock as the presence of J'cn- 
 tanieriifi obloiujns, J*. ijtdeatKH, Spirifer Nidijare^ifiin^ or S. macro- 
 2)Ieura, and their respectively associated fossils ilo the relations of 
 the several rocks in which these occur." I 
 
 ♦Quar. Jour. Geol. Soc; Murchison, XV, 3.5;J; Giekie, XVII, 171; Nicol, XVil, 58, 
 XVIU, tt.l. 
 
 t null. soc. Gcol. lie Fr. (2), IV, 780. 
 
 t I'Mlcontology of Xew York, Vol. Ill, Introduction, page 93. „ . ^ . .. 
 
89 
 
 AI)1>KK8S OF T. HTKUUY IIl'NT. 
 
 I nm ooiniiiood thiit tliOHc crvHtnlliiio schlslm of riormniiy, Aii<^lo- 
 Hoa, iiiid the Scolcli IIi<{liliiii(ls, will ho round, like those of Nor- 
 wiiy, to holonjj; to ii period anterior to the deposition of the 
 Canihrian sediments, and will eoi'ros[)ond with the newer fi;neissie 
 series of our ApiJuhieliian re<j;ion. Tliere exists, in tlie Iligldands 
 of Seothmd, a <j;reat volume of llne-<^raiued, thin-l>e(lded miea- 
 schists with andalusit*', stainolite and cyaniti'. which are met with 
 in Arj;;yleshii'e, Alierdeenshire, Hanll'shire and the Shetland Isles. 
 Rocks rej^arded hy Ilarkness us identical with these of the Scottish 
 Ilitfhiands also occur in l)one<iai and jNIayo in Ireland. Through 
 the kindness of the Kev. Trof. Ilaughton of Trinity College, and 
 Mr. Uoitert II. S<'ott, then of Dublin, I received some years since, 
 a liirge collection of the crystalline rocks of Donegal, which 
 I am thus enabled to compare with those of North America, and 
 to assert the existence in the northwest of Ireland, of our second 
 and third series of crystalline schists. The (Jreen Mountain rocks 
 are there exactly represented by the dark colored chromiferous 
 serpentines of Aghadoey, and the steatite, crystalline talc and 
 aetinolite of Cnjhy Head; while the nnca-schist of Loch Derg, 
 with white (piartz, blue cyanite, staurolite and garnet, all united 
 in the same fragment, cannot be distinguished from s[)ecimens 
 found at Cavendish, Vermont, and Windham, Maine. The line- 
 grained andalusite-schists of Clooney J^ough are exactly like 
 those from Mount Washington ; while the granitoid mica-slates 
 from several other localities in Donegal are not less clearly of the 
 type of the White Mountain series. Similar micaceous schists, 
 with andalusite (cliiastolite), occur on Skiddaw, in Cumberland, 
 England, the relations of which have been clearly dcdned by Sedg- 
 wick, who groups the rocks of SkicMaw into four ilivisions. The 
 lowest of these, succeeding the granite, is a series of crystalline 
 rocks, not described lithologically, with mineral veins, " having 
 some resemblance to the rocks of Cornwall," and including 
 towards the summit, " cliiastolite schists and chiastolite rocks." 
 These are followed in ascending order by two great series of slates 
 and grits, succeeded by a fourth division of schists, sometimes 
 carbonaceous, holding in parts fucoids and graptolites, which are 
 apparently overlaid discordantly by sundry trappean conglomer- 
 ates and chloritic slates.* The graptolites of the Skiddaw slates 
 
 ♦Synopsis of British Paleozoic Rocks, p. Ixxxiv, being an introduction to McCoy's 
 Brit. Pa). Fossils (1856). 
 
 # 
 
(iKO(iN()8V OF THE AVrALArillANS. 
 
 ya 
 
 lie 
 
 sis, 
 
 Mil, 
 (Ig. 
 
 riie 
 iiie 
 iiig 
 1 iiij; 
 
 Ics 
 
 K!S 
 
 irc 
 ■ler- 
 
 
 i 
 
 ari' round to be identical witli those of the Levis formntion,* and 
 it is wortliy of notice tiiat ultliou<rii Scdj^wick places tlie niica- 
 Hcliists witli andalusite (cliiastolite) ho far below the (jfraptolitic 
 beds, he elsewhere, in coniparinfjj the rocks of North Wales and 
 Cumberland, states that the chloriti(; and micaceous rocks of 
 Aujjlesea and ('aeruarvon are not represented in Cumberland. 
 bein<^ distinct from tlie other rocks of North Wales, and much 
 older.! 
 
 In Victoria, Australia, the position of the chiastolite schists, ac- 
 cording to Selwyn, is beneath the graptolitic slates. JJoblaye, it 
 is true, asserted in \h:\H that the chiastolite schists of Les Salles. 
 near rontivy in IJrittany, include Ortlii.s and Cahimeui\\ but when 
 we remember that even experienced observers in the White Moun- 
 tains for a time mistook for remains of Crustacea and brachiopods, 
 certain obscure forms, which they allerwards found not to be 
 organic, and that Dana, in this connection, has called attention to 
 the deceptive resemblance to fossils presented by some imperfectly 
 developed chiastolite crystals in the same region, § we nui}' well 
 require a verification of Boblaye's observation, especially since we 
 find that more recently D'Archiac and Dalimier agree with De 
 lieaumont and Dufrenoy in placing the chiastolite schists of 
 Irittany at the very base of the transition sediments, marking the 
 summit of tlu! crystalline schists. || 
 
 With regard to the crystalline schists of Lakes Huron and Su- 
 perior, to which the name of the Iluronian system has been given, 
 the observations of all who have studied the region concur in plac- 
 ing them unconform!d)ly beneath the sediments which are supposed 
 to represent the base of the New York system, while, <m the other 
 hand, they rest unconformably on the Laurentian gneiss, fragments 
 of which are included in the Iluronian conglomerates. The gneisf*ic 
 series of the Green Mountains had, however, ns we have seen, been, 
 since 1H41, regarded by the l)rothers Rogers, Mather, Hall. Hitch- 
 cock, Adams, Logan, myself and others, as t)f Silurian age. Eaton 
 and Eminons had alone claimed for it a pre-Canibrian age luitil, in 
 1802, Macfarlane ventured to unite it with the Hunniian system. 
 
 * Harkness and Salter, (Juar. , Jour. Geol. Soc, xix, 136. 
 
 tGeol. Journal (1845). IV, 68;$. 
 
 JBull. Soc. Geo). doFr.,X,a27. • 
 
 § Amer. Jour. Scl., II, i, 415, V, 11«. 
 
 II Bull. Soc. Geol. de Fr., II, xviii, 6(U. 
 
 AMER NAT., ASSOC. NUMBER. 3 ^ 
 
84 
 
 ADDRESS OF T. STEUUY HUNT. 
 
 and to identify both witli the crystnlline scliists of a similar age in 
 Norway. Later oltservationH in Michi<>an jnsstily still farther this 
 comi)arison,for not only the more schistose beds of the Green Monn- 
 taiji series, bnt even the mica-schists of the third or White jNIonntain 
 series, with stanrolito and garnet, are represented in Michigan, as 
 appears by the recent collections of Major li rooks, of the Geolog- 
 ical Survey of Michigan, kindly placed in mj' hands for examina- 
 tion, lie informs me that tliese latter scliists are the highest of 
 the crystalline strata in the northern peninsula. 
 
 To the north of Lake Superior, as I have already shown else- 
 where, the schists of this third series, which, as early as 1861, 1 
 compared to those of the Appalachians, are widely spread ; while 
 in Hastings County, forty miles nortli of Lake Ontario, rocks nav- 
 ing the mineralogical and lithological characters both of the 
 second and third series are found resting on the first or Laureu- 
 tian, the three apparently unconformable, and all in turn overlaid 
 by horizontal Trenton limestone.* 
 
 We have shown, that in Pennsylvania, while some of these schists 
 of the second and tliird series were regarde<l as altered primal 
 rocks 1)3' H, ]). Rogers, others, litliologicall}' similar, were referred 
 by him to the older so-called azoic series, wiiich we believe to be 
 their true position. Professor W. B. Rogers has lately informed 
 me that in Virginia the gneissic series having the characters of 
 the Green jMountain rocks, is clearly overlaid unconformal)ly by the 
 lowest primal paleozoic strata of the region. Coming northward, 
 the uncryslalliue argillites and sandstones holding Paradoxides at 
 Braintree, Massachusetts, f and St. John, New Brunswick, overlie 
 unconformably ciystalline schists of the second series, and in the 
 latter region, in one locality, rocks Avhich are by Bailey and Mat- 
 thew regarded of Laurentian age. In Newfoundland, in like 
 manner, a great series of crystalline schists, in which Mr, Muiray 
 recognizes the Iluronian system as first studieil and described by 
 him in the west, is unconformabl}' OAcrlaid by a gi'oup of sand- 
 stones, limestones, and slates holding Paradoxides. The peculiar 
 gneisses and mica-schists of the White jMountain series appear to 
 be developed to a great extent in Newfoundland, which has led 
 me to propose for them the name of the Terranovan system. J 
 
 * Ainer. Jour. Sci., TI, xxxi, ;!!)5. and 1. K5. 
 tHunt. Proc. Bost. Xat. Hist. Soc, Oct., 19, 1870. 
 t Amer. Jour. Sci., II, 1, 87. 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 35 
 
 I'ay 
 
 >y 
 
 (1- 
 
 i;ir 
 
 fo 
 
 led 
 
 + 
 + 
 
 From the part which the ruins of these rocks play in the produc- 
 tion of succeeding sediments it is not always easy to define the limits 
 between the ancient mica-schists and the Camln-ian strata in these 
 northeastern regions. It is not impossible that the two may grad- 
 uate into each other, as some have supposed, in Newfoundland and 
 Nova Scotia, but until farther lij^'ht is thrown upon the sultject I 
 am disposed to regard the relation between the two as one of der- 
 ivation rather than of passage. 
 
 We have already alluded to the history of the rocks of the 
 White Mountains, formerly looked upon as primary, and b}-^ Jack- 
 son described as an old granitic and gneissic axis uplifting the more 
 recent (Jreen Mountain rocks. Their manifest differences from the 
 more ancient gneiss of the Adirondacks, and their apparent super- 
 position to the Green Mountain series, then regarded by the 
 Messrs. Rogers as belonging to the Champlain division, led them 
 in 1H4(! to look upon the White Mountains as altered strata be- 
 longing to the Levant division of their classification, correspond- 
 ing to the Oneida, Medina and Clinton of the New York system. 
 In 1848 Sir William Logan came to a somewhat similar conclusion. 
 Accepting, as we have seen, the view of Emmons that the strata 
 about Quebec included a portion of the Levant division, and re- 
 garding the Green INIountain gneisses as the equivalents of these, 
 he was induced to place the AVhite Mountain rocks still higher in 
 the geological series than the Messrs. Rogers had done, and ex- 
 pressed his belief that they might be the altered repi*esentatives 
 of the New York system from the base of the Lower Helderberg 
 to the top of the Chemung ; in other Avords, that they were not 
 Middle Silurian, but Upper Silurian and Devonian. This view, 
 adopted and enforced by me,* Avas farther sui)ported by Lesley in 
 18<!0, and has been generally accepted up to this time. In 1870, 
 however, I ventured to question it, and in a published letter ad- 
 dressed to Professor Dana, concluded from a great number of 
 facts that there exists a system of crystalline schists distinct from, 
 and newer than, the Laurentian and lluronian, to which I gave the 
 provisional name of Terranovan, constituting the third or White 
 Mountain series, which appears not only throughout the Appalach- 
 ians, but westward to the north of Lake Ontario, and around and 
 beyond Lake Superior, f Although I have in common with most 
 
 * Geol. Survey of Ciinada. Report 1847-48, p. 58; also Amer. Jour. Sci., II, ix, 10. 
 t Amor. Jour. Sci., II, 1. 8.'{. 
 
86 
 
 ADDRESS OF T. STERRY HUNT. 
 
 other American geologists, maintained that the crystalline rocks 
 of the Green Mountain and White Mountain series are altered 
 paleozoic sediments, I find, on a careful examination of the evi- 
 dence, no satisfactory proof of such an age and origin, but an 
 array of facts which appear to me incompatible with the hitherto 
 received view, and lead me to conclude that the whole of our cr3'S- 
 talline schists of eastern North America are not only pre-Silurian 
 but pre-Cambrian in age. 
 
 In what precedes, I have endeavored to discuss briefly and 
 impartially some of the points in the history of the older rocks, 
 and of the views which during the past thirty years have been 
 entertained as to their age and geological relations, both in Amer- 
 ica and in Europe. I have said some things which will provoke 
 criticism, and at the same time, I trust, lead to farther study of 
 these rocks, a correct knowledge of Avhich lies at the basis of 
 geological science. 
 
 T cannot, however, conclndp fhis part of my subject without 
 referring to the views put forth in 1869 by Professor Hermann 
 Credner of Leipzig, in an essay on the Eozoic or pre-Silurian for- 
 mations of North America.* With Macfarlane, he refers to the 
 Huronian the gneissic series of the Green Mountains, but includes 
 with it, as pai't of the Huronian system, the so-called Lower Ta- 
 conic rocks of Vermont, "with remains of annelids and crinoids." 
 Credner thus falls into the very error against Avhich Emmons 
 warned American geologists, namely, the confounding in one sys- 
 tem the ancient crystalline schists with the newer fossiliferous 
 sediments. Resting unconformably on these, he places, first, the 
 Upper Taconic, corresponding, according to him, to a part of the 
 Quebec group, and second, the Potsdam sandstone. In this he 
 has copied, for the most part, Marcou, who, however, groups the 
 whole of these various divisions in the Taconic s3''stem, while 
 Ci'cdner, rejecting the name, unites a portion of the Taconic of 
 Emmons with the Huronian system, and refers the other portion, 
 together with the Potsdam, to the Silurian. These same views are 
 set fort'\ in a more recent paper, bj'^ the same author, on the AUe- 
 ghf iiy system, which is accompanied with sections and a geologi- 
 cally colored map.f In this, not content with including in the 
 Huronian both the fossiliferous strata of the Levis formation and 
 
 * Die Gliederung der Eozoischen Formationsgi-iipiie, u. s. w., pp. 63. Halle, 1HG9. 
 tPetermaun's Geograpbischo MittheiliiiigcD. 2net't, 1871. 
 
 # 
 
GEOGNOSY OF THE APPALACHIANS. 
 
 37 
 
 the crystalline schists of the Green Monntuins, he refers the 
 gneisses and mica-schists of the White Monntains to the same 
 system ; while the broad area of similar rocks from their base to 
 the sea at Portland, is regarded as Laurentian, This, on Credner's 
 map, is also made to inclnde, with the exception of the White 
 Monntains themselves, all the rocks of the third or White Monn- 
 tain series which cover so large a part of New England. Those 
 who have followed the historical sketch already given, can see how 
 wldel}' these notions of Credner differ from those of Ennnons, and 
 from all other American geologists, and how much they arc at 
 variance with the present state of our knowledge. It is nuich to 
 be regretted that so good a geologist and lithologist should, from 
 a too superficial stud\', have fallen into those errors, which can 
 only retard the progress of comparative geognosy, for wliich he 
 has done so much. In England, again, Credner confounds the 
 Cambrian and Iluronian, referring to the latter system the Aviiole 
 of the Longmynd rocks with their characteristic Cambrian fauna, 
 a view which is supported only by the conjectured Cambi-ian age 
 of the crystalline schists of Anglesea, whicli are probably pre- 
 Cambriau and veritably Iluronian, like the Urschiefer of Scan- 
 dinavia ; which Credner correctly refers to the latter system, as 
 Macfurlane and Bigsby had done l)efore him. He, moreover, rec- 
 ognizes in the similar crystalline schists of Scotland, the Urals, 
 and various parts of Germany, including those of Bavaria and 
 Bohemia, a newer system, overlying the prinnir}' or Laurentian 
 gneiss, and corresponding to the Iluronian or Green Mountain 
 series of North America, while ho suggests a correspondence with 
 similar rocks in Jajjan, Bengal, and Brazil. In a collection of 
 rocks brought from the latter country l)y Professor C. F. Ilartt, I 
 have found, as elsewhere stated,* what api)ear to be representa- 
 tives of the three types of crystalline sdiists which have been 
 distinguished in eastern North America. 
 
 It will be noticed that I have not, in the preceding pages, 
 referred to the Labradorian (I'i)per Laurentian) system, whieh is 
 characterized by a great predominance of norites and hjperites. 
 Although occupying a considerable area in the Adirondack region, 
 it is not certainly known in tiie Appalacliian range, and was, 
 therefore, omitted in tlie discussion. In addition to the facts 
 
 ♦The Nation, Doc. 1, 1870, and Haiti's Geology of Brazil, p. 550. 
 
38 
 
 ADDRESS OF T. STKRUY HUNT. 
 
 given by me in 18G9,* it may be added tliat the observations of 
 Mr. Kicliardsoii, durinfj; tbat season, on the nortli side of the (lulf 
 of St. Lawrenee, confirm the previons conclnsious, and show tliat 
 the rocks of the Labradorian (or ratlier Norian) system there re- 
 pose transgressively, and often at comparatively moderate angles, 
 on the nearly vertical Lanrentian gneisses.f We may, I tliink, in 
 the present state of our kiunvledge, regard these norites or Norian 
 rocks as portions of a i)re-Hnronian system. 
 
 II. The Origin of Cn/stulline Hacks. 
 
 We now ai)proach the second part of onr subject, namely, the 
 genesis of the crystalline schists whose liistory we have jnst dis- 
 cussed. The origin of the mineral silicates which make up a great 
 portion of the crystalline rocks of the earth's surface is a (|ues- 
 tion of nnich geological interest, which has been to a great degree 
 overlooked. The gneisses, mica-schists and argillites of various 
 geological periods do not differ very greatly in chemical constitu- 
 tion from modern mechnnical sediments, and are now very gene- 
 rally regarded as resulting from a molecular re-arrangeuuMit of 
 similar sediments formed in earlier times by the disintegration 
 of previously existing rocks not very unlike thtm in composition ; 
 the oldest known formations being still composed of crystalline 
 stratified deposits presumed to be of sedimentary origin, liefbre 
 these the imngination conceives yet earlier rocks, until we reach 
 the surface of unstratiiicd material Avhich the globe may be sup- 
 posed to have presented Itefore water had begun its work. It is 
 not, however, my present i)lan to consider this far-off beginning of 
 sedimentary rocks, which I have elsewhere discussed. J 
 
 A[)art from the clay and sand-rocks just referred to, whose com- 
 position may be said to be essentially quartz and aluminous silicates, 
 cliierty in the forms of feldspars and micas, or the results of their 
 partial decomposition and disintegration, there is another class 
 of crystalline silicated rocks which, though far loss important in 
 bulk than the last, is of great and varied interest to the litholo- 
 gist, the mineralogist, the geologist and chemist. The rocks of 
 this second class nniy be defined as consisting in great ])art of the 
 silicates of the protoxyd bases, lime, magnesia and ferrous oxyd, 
 
 *0n Norites, etc.. Ainer. Jour. Sci.. II. xlviii, ISO. 
 t(jieol. Survey of Cfiiiada, Heport ISOC-ii!), p. .iOO. 
 t Amer. Jour. Science, II, 1, 2."), 
 
ORIGIN OP CRYSTALLINE ROCKS. 
 
 39 
 
 either alone, or in combination witli silicates of alumina and alka- 
 lies. They include the following as their chief constituent mineral 
 species: — pyroxene, hornblende, olivine, serpentine, talc, chlorite, 
 ei)idote, garnet and triclinic feldspars such as hibradorite. The 
 great types of this second class are not less well defined than 
 the first, and consist of pyroxenic and hornblendic rocks, passing 
 into diorites, diabases, ophiolites and talcose, ciiloritic and epi- 
 dotic rocks. Internieuiate varieties resulting from the associa- 
 tion of the minerals of this class with those of the first, and also 
 Avith the materials of non-silicated rocks, such as limestones and 
 dolomites, show an occasional blending of the conditions under 
 which these various types of rocks were formed. 
 
 The distinctions Just drawn between the two great divisions of sil- 
 icated rocks, are not confined to stratified deposits, but are equally 
 well marked in eruptive and unstratified masses, among whieh the 
 first type is represented by trachytes and granites, and the second, 
 by dolerites and diorites. This fundamental difference between 
 acid and Ijasic rocks, as the two classes are called, finds its ex- 
 pression in the theories of Phillipf^;, Durocher and Bnnsen, who 
 have deduced all silicated rocks f ro n two supposed layers of molt- 
 en matter within the earth's crust, consisting respectively of acid 
 and basic mixtures ; the trachytie and pyroxenic magmas of Bunsen. 
 From these, by a process of [)artial crystallization and elicpiation. 
 or by f'on'.mingling in various proportions, those eruptive rocks 
 which depart more or less from the norm i.l types, are supposed by 
 the theorists of this school to be generated.* The doctrine that 
 these eruptive rocks are not derived directly from a hitherto uncon- 
 gealed nucleus, but are softened and crystallized sediments, in fact 
 that the whole of the rocks at present known to us have at one 
 time been aqueous deposits, has, however, found its advocates. In 
 sui)port of this view, I have endeavored to show that the natural 
 result of forces constantly in operation, tends to resolve the various 
 igneous rocks into two classes of sediments, in which the two tyi)es 
 are, to a great extent, i)reserved. "the mechanical and chemical 
 agencies which transform the crystalline rocks into sedimiMits, sepa- 
 rate these more or less conii)letely into coarse, sandy, permeable 
 beds on the one hand, and fine clayey impervious nnids on the other. 
 The action of infiltrating atmospheric waters on the first and more 
 silicious strata, removes from thein lime, magnesia, iron-oxyd and 
 
 * Uunt oil Some Points of Choinicnl Geology, Qiiar. Jour. Geol. Soc, XV, 48!>. 
 
 . 
 
40 
 
 AI>I)UKSS OF T. STEURY HUNT. 
 
 soda, leaving ])chin(l silica, alumina and potasli — tlie elomonts of 
 granitic, gneissic and tracliytic rocks. Tlic liner and more alumi- 
 nous sediments, including the ruins of the soft and easily al)raded 
 silicates of tlie pyroxene group, resisting the penetration of the 
 water, will, on the contrary, retain their alkalies, lime, magnesia 
 and iron, and tlnis will have the composition of the more basic 
 rocks. * 
 
 A little cousideration will, however, show that tliis process, al- 
 tliough doubtless a true t;auHe of dirt'erences in the composition of 
 sedimentary rocks, is not the only one, and is inadequate to ex- 
 plain the production of many of the varieties of stratified silicated 
 rocks. Such are serpentine, steatite, hornl)lende, diallage, chlorite, 
 pimte and labradorite, all of which mineral species form rock-masses 
 b}"" themselves, frequently almost without admixture. No geologi- 
 cal student will now (juesticm that all of these rocks occur as 
 mem])ers of stratified formations. Moreover, the manner in which 
 serpentines are found interstratifled with steatite, chlorite, argillite, 
 diorite, hornblende and feldspar rocks, and these, in their turn, 
 with(|uartzites and orthoclase rocks, is such as to forbid the notion 
 that these various materials have been deposited, with their present 
 composition, as mechanical sediments from the ruins of preexist- 
 ing rocks ; a hypothesis as luitenable as that ancient one which 
 supposed them to be the direct results of plutonic action. 
 
 There are, however, two other h3'potheses which have been pro- 
 posed to explain the origin of these A'arious silicated rocks, and 
 especially of the less abundant, and, as it were, ex<'Oi)tional species 
 just mentioned. The first of these supposes that the minerals of 
 which thej'^ are composed, have resulted from an alteration ot pre- 
 viously existing minerals, often very unlike in composition to the 
 I^resent, ])y the taking away of certain elements and the addition 
 of certain others. This is the theory of metamorphism b}' pseu- 
 domorphic changes, as they are called, and is the one taught bj' 
 the now reigning school of chemical geologists, of which the 
 learned and laborious Bischof," whose recent death science deplores, 
 maj' be regarded as the great exponent. The second hj'pothesis 
 supposes that the elements of these various rocks were originally 
 deposited as, for the most part, chemicallj^ formed sediments, or 
 precipitates ; and that the subsequent changes have been simply 
 
 Quar. Jouv. Geol. Soc, xv, 489; also, Aiiiei'. Jour. Sci., II, xxx, 133. 
 
OUIOIN Oy CRYSTALLINE KOCKS. 
 
 41 
 
 
 molecular, or, at most, confined in certain cases to reactions be- 
 tween the mingled elements of the sediments, with the elimination 
 of water and carbonic acid. It is proposed to consider briefly, 
 these two opposite theories, which seek to explain the ori<?in of 
 the rocks in (piestion respectively by psendomorphic clianges in 
 pret'xisting crystalline rocks, ! nd b>' the crystallization of aqueous 
 sediments, for the most part chemically formed precipitates. 
 
 Mineral pseudomorphism, that is to say, the assumption by one 
 mineral substance of the crystalline form of another, may arise in 
 several ways. First of these is the fillinfi; up of a mould left by 
 the solution or decomposition of an imbedded crystal, a process 
 which sometimes takes place in mineral veins, wliere the processes 
 of solution and dejiosition can be freel}^ carried on. Allied to 
 this, is the mineralization of organic remains, where carbonate 
 of lime or silica, for example, fills the pores of wood. When sub- 
 setiucnt decay removes the woody tissue, the vacant spaces may, 
 in tlieir turn, be filled by the same or another species. * In the 
 second place, we may consider pseudomorphs from alteration, 
 which are the result of a gradual change in the composition of a 
 mineral species. This process is exemplified in the conversion of 
 feldspar into kaolin l)y the loss of its alkali and a portion of sil- 
 ica, and the fixation of water, or in the change of clialybite into 
 limonite by the loss of carbonic acid and the absorption of water 
 and oxygen. 
 
 The doctrine of pseudomorphism by alteration as taught by Gus- 
 taf Rose, llaidinger, lilum, Volger, Rammelsberg, Dana, Bischof, 
 and many others, leads them, however, to admit still greater and 
 more remarkal)le changes than those, and to maintain the possl- 
 bilit)^ of converting almost any silicate into any othei . Tims, by 
 referring to the pages of Bischof 's Lehrl)uch der Geognosie, it will 
 be found that serpentine is said to exist as a pseudomorph after au- 
 gite, hornblende, olivine, cliondrodite, garnet, mica, and i)robably 
 also after labradorite, and even ortlioclase. Serpentine rock or oph- 
 iolite is supposed to have resulted, in different cases, from the al- 
 teration of hornblende-rock, diorite, granulite and even granite. 
 Not only silicates of protoxyds and aluminous silicates are con- 
 ceived to be capal)le of this transformation, but probabl}' also 
 quartz itself ; at least, Blum asserts that meerschaum, a closely re- 
 
 * Hunt oil the Siliciflcutioii of Fossils, Cauadiau Naturalist, uew series, I, 40. 
 
42 
 
 ADDUKSS OK T. STKKHV HUNT. 
 
 luted 8iliciite of mjigiipsiu, which somotiincs accompanios Horpen- 
 tino, roHiilts from tho altenitioii of flint ; wliilc accord iiifi to lio.se, 
 Herpoiitinc may even Ite produced I'rom (lolomite, wliicii we are 
 told is itself produced l»y the alteration of limestone. IJut this is 
 not all, — feldspar may replace carlionatc of lime, and carbonate 
 of lime, feldspar, so that, according to Volger, some gneissoid lime- 
 stones are probalily formed from gneiss by the substitution of 
 calcite for orthocluse. In this way, we are led fmni gi\eiss or 
 granite to limestone, from limestone to dolomite, and from dolo- 
 mite to serpentine, or more directly from granite, granulite or 
 diorite to serpentine at once, without passing through the inter- 
 mediate stages of limestone and dolomite, till we are ready to 
 exclaim in the worils of Goethe : — 
 
 '• >ricli iiiiffstifft iliii^ VerliiiiKliche 
 Iiii widriKt'ii (ii's<;li\vittz, 
 Wo Nichts veilianet. Alios llielit. 
 Wo sclioii vcrsclnvundon was man siclit,"* 
 
 which we ma}- thus translate : — "I am vexed with the sophistry in 
 their contrary jargon, where nothing endures, but all is fugitive, 
 and where Avhat we see has already passed awaj'." 
 
 By far the greater number of cases on which this general theory 
 of pseudomorphism by a slow process of alteration in minerals, has 
 been based are, as I shall endeavor to show, cxiimples of the phe- 
 nomenon of mineral enveloitment, so well studied by Delesse in 
 his essay on Pseudomorphs,t and maj' be considered under two 
 heads: — first, that of symmetrical envelopment, in which one 
 mineral species is so enclosed within the other that the two appear 
 to form a single crystalline individual. Examples of this are seen 
 when prisms of cyanite are surroumled by staurolite, or staurolite 
 crystals completely enveloped in those of cyanite, the vertical axes 
 of the two prisms corresponding. Similar cases are seen in the 
 enclosure of a prism of red in an enveloi)e of green tourmaline, of 
 allanite in epidote, and of various minerals of the pyroxene group 
 in one another. The occurrence of nmscovite in lepidolite, and 
 of margarotlite in Icpidomelane, or the in\erse, are well-known 
 examples, and, according to Scheerer, the crystallization of serpen- 
 tine around a nucleus of olivine is a similar case. This phenome- 
 non of sj'mmetrical envelopment, as remarked by Delesse, shows 
 
 *Chinesisch-DeiitscIie Jnhres und Tages Zcitcn, xi. 
 t Annalos dos Mines, V, xvi, ;!17-302. 
 
OBIOIN OF CRYSTALLINE ROCKS. 
 
 48 
 
 itself with species wliich tiro fj^enerally isoniorphoius or homa?oinor- 
 phous, and of related eiieinical c(>ini)o.sition. Allied to tiiis is the 
 repeated alternation of erystalline laniiiiu' of related species, as 
 in perthite, the crystalline cleavable masses of which consist of 
 thin, altornatinjif layers of orthodasc and albite. 
 
 Very unlike to the above arc tlujsc cases of envdopnicnt lu 
 which no relations of crystalline synnnetry nor of siniihir chemi- 
 cal constitution can be traced. Examples of this kind are seen in 
 garnet crystals, the walls of which are shells, sometimes no 
 thicker than jtaper, enclosing in dilferent cases, crystalline carbon- 
 ate of lime, epidote, chlorite or (juartz. In like manner, crystal- 
 line shells of leucitc enclose feldspar, hollow })risms of tourmaline 
 are tilled with crystals of mica or with hydrous peroxyd of iron, 
 and crystals of beryl with a granular mixture of orthoclase and 
 quartz, hohling small crystals of garnet and tourmaline, a compo- 
 sition identical with the enclosing granitic veinstone. * Similar 
 shells of galenite and of zircon, having the external forms of 
 these species, are also found tilled with ealcite. In many of these 
 cases the process seems to have been first the formation of a hol- 
 low mould or skeleton-crystal (a phenomenon sometimes observed 
 in salts crystallizing from solutions), the cavity being subsecjuently 
 tilled with other matters. Such a })rocess is conceivalile in free 
 crystals found in veins, as for example, galenite, zircon, tourmaline, 
 beryl and some examples of garnet, but is not so intelligible in the 
 case of those garnets imbedded in mica-schist, studied by Delesse, 
 which enclosed within their crystalline shells irregidar masses of 
 white (pKirtz, with some little admixture of garnet. Delesse con- 
 ceives these and similar cases t()l)e ))ro(lueed by a process analogous 
 to that seen in the crystallization of ealcite in the Fontainebleau 
 sandstone ; where the (juartz grains, mechanically enclosed in wc.'ll- 
 delinetl rhombohedral crystals, equal, according to him, sixty-five 
 per cent., of the mass. Ver3^ similar to these are the crystalloiils 
 with the form of orthoclase, which sometimes consist in large i)art 
 of a granular mixture of quartz, mica and orthoclase, with a little 
 cassiterite, and in other cases, contain two-thirds their weight of 
 the latter mineral, with an admixture of orthoclase and (piartz. 
 Crystals with the form of scapoUte, but made up, in a great part, of 
 mica, seem to be like cases of envelopment, in which a small i)ro- 
 portion of one substance in the act of crystallization, compels in- 
 
 ♦ Rei)ort (jJeol. Survey of Canada, 18(i(;. page 18!). 
 
44 
 
 ADDRK88 Ol' T. STKIUIY HUNT. 
 
 to its own crystalline form a hiryro portion of .some foroi<i;n material, 
 whicli may even so mask the erystaili/in<; element tiiat tiiis l»e- 
 eoines overlooiied, as of Hceonilary importance. Tlie snlKstanco 
 wliieli, nnder the name of honj>;iiile, luis Iteen (lescrilx'd as an al- 
 tered spinel, isfoinid l>y analysis to he an adniixtnre of viillkni'rito 
 witli a variable proportion of spinel, wliicli. in some specimens, does 
 not exceed ei<;ht per cent., hnt to which, nevertheU'ss, tlu'se crystal- 
 loids appear to owe their more or less complete oetohedral form.* 
 The nl»ove characteristic exami)les of synnnetrical and asynnnct- 
 rical enveloimient arc cited from a <^reat nnmher of others which 
 mi;j;ht have been mentioned. Very nnmy of these arc by the pseu- 
 domorphists rcfj^arded as resnlts of partial alteration. Tims, in 
 the case of associated ciystals of andalusite and cyanite, IJischof 
 does not hesitate to maintain tlie di'rivation of andalnsite from 
 the latter species by an elimination of (pnirtz ; more than this, as 
 the andalnsite in (picstion occnrs in a <j,ranite-like rock, he sng- 
 ffests that itself is a product of the alteration of orthoclasc. In 
 like manner the mica, which in some cases coats tourmaline, and 
 in others, lills hollow prisms of this mineral, is supposed to result 
 from a subseciuent alteration of crystallized tourmaline. So in 
 the case of shells of leneite Hlled with feldspar, or of garnet en- 
 closing epidotc, or chlorite, or (juartz, a similar transformation of 
 the interior is snpposed to have been mysteriously effected, while 
 the external portion of the crystal remains intact. Again the ag- 
 gregates of tinstone, (luartz and orthoclase having the form of the 
 latter, arc, by Bischof and his school, looked upon as results of a 
 partial alteration of previously formed orthoclase crystals. It 
 needed only to extend this view to the crystals of caleite enclos- 
 ing sand-grains, and regard these as the result of a partial alter- 
 ation of the carbonate of lime. There is absolutel}- no proof 
 that these hard crystalline substances can undergo the changes 
 supposed, or can be absorbed and modified like the tissues of a 
 living organism. It may, moreover, be confidently allirnu'd that 
 the obvious facts of envelopment are adequate to explain all the 
 cases of association upon which this hypothesis of pseudomori)hism 
 1)3' alteration, has been based. Why the change should extend to 
 some parts of a crystal and not to others, why in some cases the 
 exterior of the cr3'stal is altered, while in others the centre alone 
 
 * Bepoit Geol. Survey of Cauada, ISiifi. y\^. 18!», 2115. Anicr. Jour. Sci., Ill, i, 188. 
 
OUUilN OF C'llYSTALLINK UOCKS. 
 
 4A 
 
 is ivinovcd and roplnccd by u diiriTcnt inatoriul, nro (|U0Htion8 
 which the advocates of tliis fanciful hypotlicsis have not cxphiinod. 
 Ah taufflit by lUnni and lliscliof, liowevcr, these views of the al- 
 teration of mineral species have not only been j^enerally accepted 
 bill have formed the basis of the j^enerally received theory of rock- 
 metamorphisni. 
 
 Protests a<j;ainst the views of this school have, however, not been 
 wantinj?. Scheerer, in lH4(i, in his researches in Polymeric Iso- 
 morphism,* attempted to show that ioUte nnd aspasiolite, a liy- 
 drous species whicii liad been looked ni)on as resnltin<; from its al- 
 teration, were isomoridions species crystallizing!; togcthi'r. and, in 
 like manner, that the association of olivine and serpentine in the 
 same crystal, at Snarnm in Norway, was a case of envelopment of 
 two isoniorphons species. In both of these instances he main- 
 tained the existence of isoniorphons relations between silicates in 
 which ."{MO replaced M<>;(). lie hence rejected the view of (iustaf 
 Hose that these seri)entine crystals were results of tiic alteration 
 of olivine, and supported his own by reasons drawn from the con- 
 ditions in which the crystals occur. In 1853 I took up this (jues- 
 tion and endeavored to show that these cases of isomorphism 
 described by Scheerer, entered into a more general law of isomor- 
 phism pointed out by me among homologous compounds ditl'ering 
 in their formulas by /(INLC)^ (jNI = h3(lrogen or a metal). I in- 
 sisted, moreover, on its bearing upon the received views of the 
 alteration of minerals, and remarked, "The generally admitted no- 
 tions of pseudomorphism seem to have originated in a too exclu- 
 sive plutonism, and require such varied hypotheses to explain the 
 different cases, that we ai'e led to seek for some more simple ex- 
 planation and to find it, in man}' instances, in the association and 
 crystallizing together of homologous and isoniorphons species." f 
 Subseijuentl}', in IHOO, I coni1)ated the view of Bischof, adopted 
 by Dana, that " regional metamorphism is pseudomorphism on a 
 grand scale," in the following terms : — 
 
 " The ingenious speculations of IJischof and others, on the pos- 
 sible alteration of mineral species by the action of various saline 
 and alkaline solutions, may pass for what they arc worth, although 
 we are satisfied that by far the greater part of the so-called cases 
 of pseudomorphism in silicates are purely imaginary, and. when 
 
 * VopK. Annal.. Ixviii, 319. 
 fl'ogg. Anual., Ixvlii, 311). 
 
IG 
 
 ADUItK88 OF T. STKllHY HUNT. 
 
 rpiil, nro Imt local ami accidciHal plicnoiiu'iia. lliscliofH notion 
 ol" till' psi'iKlonioiplilMiii of wilifalt's liko tt'l(lsi)ais ami |)vro\('ue«, 
 pi'i'HU|)|)o.st'H tlio I'xif+tt'iico of cryHtallino rockH, whose gi'iu'ration 
 this iicittiinist never atteniptu to explain, hnt takes his stailing- 
 point from u plntunic hasis." 
 
 I then asserted that the problem to he solved in reji'ional metu- 
 morphism is the conversion of sedin I'ntary strata, "derived by 
 chemical and mechanical aj^encies from the oceau-wuters and pre- 
 existinjf crystalline rocks into aggrej^ations of crystullim! silicates. 
 These nvetaniorphic rocks, onco formed, are liiiblo to alteration 
 only by local ami su[)erlicial aiicncies, and are not, like tlu' tissnes 
 of a living organism, subject to incessant transformations, the 
 psiiiidomorphism of IJischof."* 
 
 1 had not, tit that time, seen the essay by Delessc on Pseudo- 
 morphs already referred to, published in IHol), in which he nudn- 
 taijied views similar to those set forth by me ii IH;').'! and iHCiO, 
 declaring that much of what had been regarded as pseudomor- 
 phism had no other l)asis than the observed associations of miner- 
 als, and that often " the so-called metainorphism tlnds its natural 
 explanation in envelo[)ment." These views he ably and iugeid- 
 ously defended by a careful discussion of the whole range of facts 
 belonging to the history of the subject. 
 
 My own expression of opinion on this question, in IHi')'.), had 
 been privately criticised, and 1 had been charged with a want of 
 comprehension of the (piestion. It was, therefore, with no small 
 pleasure, that 1 not oidy saw my views so ably supported by 
 Di'lesse, but read the lang 'xc of Carl Friedrich Naumann, who 
 in I'SCil wrote to Dclesse a ollows, leferring to his essay just 
 noticed : — 
 
 "You have rendered u veritable service to science in restricting 
 pseudomorphs to their true limits, and separating what had been 
 erroneously united to them. As you have remarkecl, enveloi)- 
 nients have, for the most part, nothing in common with pseudo- 
 m()r[)hs, and it is inconceivable that they have been united bj' so 
 many mineralogists and geologists. It ai)pears to nic. moreover, 
 that they connnit an analogous error, when they regard gneisses, 
 amphibolites, etc., as being, all of them, the ri.'sults of metamor- 
 phic epigenesis, and not original rocks. It is precisely because 
 pseudomorphism has been so often confounded with metamori)hism 
 that this error has found acceptance. I only admit a pseuchMuorph 
 
 * Amer. Jouv. Sci.. II. xxx, 1;>5. 
 
OKKilN Of CIIY8TALLINK UOt'KH. 
 
 47 
 
 wluTo tluu'o Ih Homo crywtiil tlie form of which has boon preaorved. 
 Th(M'o lU'e vory umiiy iiictiiniorphic Miilistjiiiccs which arc, in no hcuhg 
 of tlic wonl, p.HciKloiiioipiis. ihitl the iiitiiic of fri/sfo/hiid hccn 
 chosen, instcml of pHcinloiiiorph, tiiiM conriisioii woiijii ccrtniiily 
 Imvc never found its way into the Hcienco. I think, with yon, that 
 tlie enveh)pnu'nt of two niinerals in most nfcnerally i'xpiiiined hy 
 a coiifi'iii/xirdticoii!* and iiriijiiinl crvHtalli/ation. Secomhiry envel- 
 opments, however, exist, and such nuiy bo caile(l pscn(h)mor|)hH 
 O" civstalloids, if tli«'v repr<Khice exactly tiie form of the crystal 
 enveloped, whether lliis last still renniins, or has entirely disap- 
 peared."* 
 
 It is unnecessary to remark that the view of Delesse and Nau- 
 mann, viz. : that the so-callod cases of psendomorphism, on which 
 the theory of metamorphism by alteration has been built, are, 
 for the most part, ex:inii)Ies of association and envelopment, and 
 the result of a contemporaneous and ori<j;inal crystallization, — is 
 identical with the view suggested by Stheerer, and generalized by 
 myself long before, when, in iHo.'J, I sought to explain the pho- 
 nomemi in (piestion by ''the association and crystallizing together 
 of homologous and isomorplious species." 
 
 Later, in l.S()2, 1 wrote as follows: — 
 
 "Pseudomorphism, which is the change of one mineral species 
 into iinother, l»y the introduction or the elimination of some ele- 
 ment or elements, presupposes metamori)hisin (/. c, metamorphic 
 or crystalline rocks), since only definite mineral i pecics can he the 
 subjects of this i)rocess. To confound metamorphism with pseu- 
 domorphism, as IJischof, and others after him have done, is there- 
 fore an error. It may be fait her i(Mnarkc(l, that, although certain 
 pseudomorphic changes may lake place in some mineral species, 
 in veins and near the surface, the alteration of great nmsses of 
 silicated rocks by such a process is as yet an unproved hypoth- 
 esis."! 
 
 Thus this unproved theory of pseudomorphism, as taught by 
 Bischof, does not, even if admitted to its fullest extent, advance 
 us a single step towards a solution of the i)roblem of the origin 
 of the various silicates, which, singly or intermingled, make up 
 beds in the crystalline schists. (J ranting, for the sake of aruu- 
 ment, that serpentine results from ihe alteration of olivi' or 
 labradorite, and steatite or chlorite from hoinblende, the <• ^in of 
 
 *Bnll. Soe. Geol. tie Friince, II, xviii, i!78. 
 
 t DoKcriptivo Cntiilojrne. Crystallino Uocks of Camilla, p. SO, London K\:iil)itiou, li3<!2; 
 also, Duljlin (iuar. Journal, Julj' 18(!;!, and Anier. Jour. Sci., II, xxx* :\S. 
 
48 
 
 ADDRESS OF T. STEUllY HUNT. 
 
 these anhj'clrons silicates, wliich are the subjects of the supposed 
 cliange, is still unaccounted for. Tlie explanation of this short- 
 sightedness is not far to seek; as already remarked, Bischof, 
 although a professed neptunist, starts from a plutonic basis. 
 When the epigenic origin of serpentine and its related rocks was 
 first taught, these were regarded as eruptive and unstratified, and 
 it was easy to imagine intruded masses of dioritic and feldspath'c 
 rocks, which had become the subjects of alteration. As, however, 
 the progress of careful investigation in the field has shown the 
 stratified character of these serpentines, diallage-rocks, steatites, 
 etc., and their intercalation among limestones, argillites, quartz- 
 ites, gneisses, and mica-schists, and even among feldspathic and 
 hornblendic strata, we are forced to reject, with Naumann, the 
 notion of their epigenic derivation, and to regard them as original 
 rocks. 
 
 This view brings us face to face with the problem of metamoi*- 
 phism as defined by me in 18G0* {ante, page 40). We must either 
 admit that these or3'stalline schists were created as we find them, 
 or suppose that they were once sands, clays, marls, etc. ; in 
 a word, sediments of chemical anil meclianical origin, which 
 by a subsequent process have been consolidated and crystallized. 
 Whence, then, come these silicates of magnesia, lime, and iron, 
 which are the sources of serpentine, hornblende, steatite, chlorite, 
 etc. ? This is the question which I proposed in that same 3'ear, 
 when, after discussing the results of my examinations of the ter- 
 tiary rocks near Paris, containing la3'ers of a h^-drous silicate of 
 magnesia related to talc in composition, among unaltered lime- 
 stones and clays, I remarked that it is evident " such silicates 
 may be formed in basins at the earth's surface, bj"^ reactions 
 between magnesian solutions and dissolved silica;" and, after 
 some farther discussion, said "farther inquiries in this direc- 
 tion may show to Avhat extent certain rocks composed of calca- 
 reous and magnesian silicates may be directly formed in the 
 moist way."t Subsequently, in a paper on "The Origin of 
 soi.e Magnesian and Aluminous Rocks," printed in the Cana- 
 dian Naturalist for June, l^iGO,}: I repeated these considerations, 
 referring to the well-known fact that silicates of lime, magnesia 
 
 *Ainer. Jour. Sci.. 11. xxx. 135. 
 t Ibid., II, xxix. 281; .ajso II, xl, 49. 
 t Ibid., II, xxxii, 280. 
 
ORIGIN OF CRYSTALLINE ROCKS. 
 
 40 
 
 and iron-oxyd are deposited during the evaporation of natural 
 waters, including those of alkaline springs and of the Ottawa 
 River. Having described the mode of occurrence of the niag- 
 nesian silicate, sepiolite, in the Paris basin, and the related 
 quincite, containing some iron-oxyd and disseminated in lime- 
 stone, I suggested that while steatite has ])een derived from a 
 compound like sepiolite, the source of serpentine was to be sought 
 in another silicate richer in magnesia ; and, moreover, that chlo- 
 rite, unless the result of a subsequent reaction between clay and 
 carbonate of magnesia, was directly formed by a process analogous 
 to that which (according to Scheerer) has, in recent times, caused 
 the deposition from waters of neolite, a hydrous alumino-magne- 
 sian silicate approaching to chlorite in composition,* "the tyi>(i of 
 a reaction which formerly generated beds of chlorite in the same 
 way as those of sepiolite or talc." Delesse, subsequently, in 1861. 
 in his essay on Rock-Metamorphism insisted upon the sepio- 
 lites or so-called magnesian marls, as probably the source of 
 steatite, and suggested the derivation of serpentine, chlorite, and 
 other related minerals of the crystalline schists, from deposits 
 approaching these marls in composition.! He recalled, also, the 
 occurrence of chromic oxyd, a frequent accompaniment of these 
 magnesian minerals, in the hydrated iron ores of the same geo- 
 logical horizon with the magnesian marls in France. Delesse did 
 not, however, attempt to account for the origin of these deposits 
 of magnesian marls, in explanation of which I afterwards verified 
 Bischof's observations on the sparing solubility of silicate of 
 magnesia, and showed that silicate of soda, or even artificial hy- 
 drated silicate of lime, when added to waters containing magne- 
 sian chlorid or sulphate, gives rise, by double decomposition, to a 
 very insoluble magnesian silicate. | 
 
 To explain the generation of silicates like labradoritc. scapo- 
 llte, garnet, and saussurite, I suggested that double aluminous 
 silicates allied to the zeolites might luive been formed, and subse- 
 quently rendered anhydrous. The production of zcolitic minerals 
 observed by Daubrce at Tlombieres and Luxeuil by the action of 
 a silicated alkaline water on the masonry of ancient Roman baths, 
 was appealed to by way of illustration. It had there been shown 
 
 * Pogg. Annal., Ixxi, 288. 
 
 t Etudes surle Metamorphlsme, quarto, pp. 91. Paris, 1861. 
 
 i Anier. Jour. Sci., II, xl, 49. ^ ^ 
 
 AMER. NAT., ASSOC. NUMBER. "' f ^ 
 
50 
 
 ADDUESS OF T. STEKRY HUNT. 
 
 by Daubrec that the elements of the zeolites had been, derived in 
 part from the waters, and in part from the mortar and even the 
 clay of the bricks, which had been attacked, and had entered into 
 combination with the soluble matters of the water to form chaba- 
 zite. I, however, at the same time pointed out another source of 
 silicated minerals, upon ^vhich I had insisted since 1857, viz. : 
 the reaction between silicious or argil'-neoous matters and earthy 
 carbonates in the presence of alkalire solutions. Numerous ex- 
 periments showed that when solutions of an alkaline carbonate 
 were heated with a mixture of silica and carbonate of magnesia, 
 the alkaline silicate formed acted upon the latter, yielding a sili- 
 cate of magnesia, and regenerating the alkaline carbonate ; which, 
 without entering into permanent combination, was the medium 
 through which the union of the silic" and the magnesia was ef- 
 fected. In this way I endeavored t . explain the alteration, in the 
 vicinity of a gi'eat intrusive mass of dolerite, of a gray Silurian 
 limestone, which contained, besides a little carbonate of magne- 
 sia and iron-oxj'^d, a portion of very silicious matter, consisting 
 apparently of comminuted orthoclase and quartz. In place of 
 this, there had been developed in the limestone, near its contact 
 with the dolerite, an amorphous greenish basic silicate, which had 
 seemingly resulted from the union of the silica and alumina with 
 the iron-oxyd, the magnesia and a portion of lime. By the crys- 
 tallization of the products thus generated it was conceived that 
 minerals like hornblende, garnet and epidote might be developed 
 in earthy sediments, and many cases of local alteration explained. 
 Inasnnich as the reaction described required the intervention of 
 alkaline solutions, rocks from which these were excluded would 
 escape change, althougli the other conditions might not be want- 
 ing. The natural associations of minei*als, moreover, led me to 
 suggest that alkaline solutions might favor the crystallization of 
 aluminous silicates, and thus convert mechanical sediments into 
 gneisses and mica-schists. The ingenious experiments of Dau- 
 bree on the part whicli solutions of alkaline silicates, at elevated 
 temperatures may play in the formation of crystallized minerals, 
 such as feldspar and p3'roxene, Avere posterior to my early publi- 
 cations on the subject, and fully justilied the importance wliich, 
 early in 1857, I attributed to the intervention of alkaline silicates 
 in the formation of crystalline silicated minerals. * 
 
 * Proc. Koyal Soc, May 7, ISTiT. Amer. Jour. Sci., 11, xxili, 438, and xxv, 28"J and 435. 
 
OUIGIN OF CHYSTALLINE UOCKS. 
 
 51 
 
 While, however, there is good reason to believe that solutions of 
 alkaline silicates or carbonates have been elllcient agents in the 
 crystallization and molecular re-arrangement of ancient sediments, 
 and have also played an important part in that local alteration of 
 sedimentary strata which is often observed in the vicinity of intru- 
 sive rocks, it is clear to me that the agency of these solutions is 
 less universal than once supposed by Daubree and myself, and will 
 not account for the formation of various silicated rocks found 
 among crj'stalline schists, such as serpentine, hornblende, steatite 
 and chlorite. When I commenced the study of these crystalline 
 strata I was led, in accordance with the almost universally received 
 opinion of geologists, to regard them as resulting from a sul)se- 
 quent alteration of paleozoic sediments, which, according to differ- 
 ent authorities, were of Cambrian, Silurian or Devonian age. Thus 
 in the Appalachian region, as we have already seen, they have, on 
 supposed strati graphical evidence, been successivcl}^ placed at the 
 base, at the summit, and in the middle of the Lower Silurian or 
 Champlain division of the New York system. A carefid chemical 
 examination among the unaltered paleozoic sediments, which in 
 Canada Avere looked upon as the stratigraphical equivalents of the 
 bands of magnesian silicates in these crystalline schists, showed 
 me, however, no magnesian rocks except certain silicious and 
 ferruginous dolomites. From a consideration of reactions which 
 I had observed to take place in such admixtures in presence of 
 heater^, alkaline solutions, and from the composition of the basic 
 silicates Avhich I had found to be formed in silicious limestones 
 near their contact with eruptive rocks, I was led to suppose that 
 similar actions, on a grand scale, might transform these silicious 
 dolomites of the unaltered strata into crystalline magnesian sili- 
 cates. 
 
 Farther researches, however, convinced me that this view was 
 inapplicable to the crj'stalline schists of the Appalachians, since, 
 apart from the geognostical considerations set forth in the previous 
 pai't of this paper, I found that those same crystalline strata hold 
 beds of quartzose dolomite and niiignesian carbonate, associated in 
 such intimate relations with beds of serpentine, diallngo and stea- 
 tite, as to forbid the notion that these silicates could have been 
 generated by any transformations or chemical re-arrangement of 
 mixtures like the accompanying beds of (juartzose magnesian car- 
 bonates. Hence it was that already, in 18G0, as shown above, I 
 
52 
 
 ADDRESS OF T. STERUY HUNT. 
 
 annoiinced mj' conclusion that seqientinc, chlorite aurl steatite had 
 been derived from silicates like sepiolite, directly foniicd in waters 
 at the eartli's surface, and that the crystalline schists hail resulted 
 from the consolidation of previously formed sediments, partly 
 chemical and partlj'^ mechanical in their origin. The latter being 
 chiefly silico-ahuninous, took, in part, the forms of gneiss and mica- 
 schists, while from the more argillaceous strata, poorer in alkali, 
 much of the aluminous silicate crystallized as andalusitc, stauro- 
 lite, cyanite and garnet. These views Avere reiterated in 1«G3,* 
 and farther in 1864, in the following language, as regards the 
 chemically-formed sediments: "steatite, serpentine, pyroxene, 
 hornblende, and in many cases, garnet, epidote and other silicated 
 minerals are formed by a crystallization and molecular re-arrange- 
 ment of silicates generated by chemical processes in waters at the 
 earth's surface."! Their alteration and crystallization was com- 
 pared to that of the mechanically formed feldspathic, silicious and 
 argillaceous sediments just mentioned. 
 
 The direct formation of the cr3-stalline schists from an aqueous 
 magma is a notion which belongs to an early period in geological 
 theory, Delabechc in 1834 1 conceived that they were thrown 
 down as chemical deposits from the waters of the heated ocean, 
 after Its reaction on the crust of the cooling globe, and l)efore the 
 appearance of organic life. This view Avas revived by Daul)ree in 
 18fi0. Having sought to explain the tdteration of paleozoic strata 
 of mechanical origin, by the action of heated waters, l;e proceeds 
 to discuss the origin of the still more ancient cryst.illine schists. 
 The first precipitated Avaters, according to him, acting on the anhy- 
 drous silicates of the earth's crust, at a very elevated temperature, 
 and at a great pressure, Avhich he estimated at tAvo hundred and 
 fifty atmospheres, formed a magma, from Avhich, as it cooled, Avere 
 successively deposited the various strata of the crj'stalline schists, § 
 This hj'pothesis, violating, as it does, all the notions which sound 
 theory teaches Avith regard to the chemistry of a cooling globe, 
 has, moreover, to encounter grave geognostical difficulties. The 
 pre-Silurian crj'stalline rocks belong to tAvo or more distinct sys- 
 tems of different ages, succeeding each other in discordant strat- 
 
 *Geol. of Canada, pp. .^77 — 581. 
 
 t Amer. Jour. Sci., II, xxxvii, 2(56, and xxxviii, 183. 
 
 t Researches in Theoretical Geology, pp. 297-300. 
 
 § Etudes et experiences synthetiques sur le Metamorphisnie, pp. 119-121. 
 
ORIGIN OV CRYSTALLINE ROCKS. 
 
 58 
 
 ification. The whole history of tlieso rocks, moreover, shows that 
 their various alternatin<>' strata were deposited, not as precipi- 
 tates from a seething sohition, biit under conditions of sedimen- 
 tation very like those of more recent times. In the oldest known 
 of them, the Laurentian sj'stom, great limestone formations are 
 interstratified with gneisses, quartzites and even with conglom- 
 erates. All analogy, moreover, leads us to conclude that even at 
 this early period, life existed at the surface of the planet. ( Jreat 
 accunudations of iron-oxyd, ])eds of metallic sulphids and of 
 graphite, exist in these oldest strata, and we know of no other 
 agency than that of organic matter, cai)able of generating these 
 products. 
 
 IJischof had already arrived at the conclusion, which in the 
 present state of our knowlodge seems inevitable, that "all the car- 
 bon yet known to occur in a free state, can only be regarded as 
 a product of the decom])osition of carbonic acid, and as derived 
 from the vegetable kingdom." He farther adds, "living plants 
 decompose carbonic acid ; dead organic matters decompose sul- 
 phates, so that, like carbon, sulpluir appears to OAve its existence 
 in a free state to the organic kingdom."* As a decom])osition 
 (deoxidation) of suli>hatcs is necessary to the production of me- 
 tallic sulpliids, the presence of the latter, not less than that of 
 free sulphnr and free carlion, depends on organic bodies ; the part 
 which tliese pla}^ in reducing and rendering soluble the peroxyd of 
 iron, and in t'.ie production of iron ores is, moreover, well known. 
 It was, therefore, that, after a careful study of tliese ancient rocks, 
 I declared in May, 18.58, that a great mass of evidence "points 
 to the existence of organic life, even during the Laurentian or so- 
 called azoic period." t 
 
 This prediction was soon verified in the discovery of the Eozonn 
 Canadenne, of Dawson, the organic character of which is now ad- 
 mitted by all zoologists and geologists of authority. But with 
 this discovery, appeared another fact, which afforded a signal veri- 
 fication of my theory as to the origin and mode of deposition of 
 serpentine and pyroxene. The microscopic and chemical i"c- 
 searches of Dawson and myself showed that the calcareous skel- 
 eton of this foraminiferal organism was filled with tlie one or the 
 other of these silicates in such a manner as to make it evident that 
 
 * lUschof, Lelubuch, Ist. eil., II, i>5. Euglli^h ed., I, 252, iU. 
 t Amer. Jour. Science, II, XXV, 430. . 
 
 : 
 
54 
 
 ADDRESS OF T. STKRUY HUNT. 
 
 they had r('i)hicc(l the sarcode of the animal, precisely as glauco- 
 nito and simihir silicates have, from the Silurian times to the pres- 
 ent, filled and injected more recent foraminiferal skeletons. 1 re- 
 called, in connection witli this discovery the observations of 
 Ehrenbertf, Mantell and Hailey, and the more recent ones of Tour- 
 tales, to the ertect that glauconite or some similar substance occa- 
 sionally tills the spines of Echini, the cavities of corals and mille- 
 pores, the canals in the shells of lialanus, and even forms casts 
 of the holes made by burrowing sponges (C'lionia) and worms. 
 The significance of these facts was fartlicr illustrated by showing 
 that the so-called glauconites dilfer considerably in composition, 
 some of them containing more or less alumina or magnesia, and 
 one from the tertiary limestones near Paris being, according to 
 Berthier, a true serpentine. * 
 
 These facts in the history of Eozoon, were ilrst made known by 
 me in oMay, l<SGi, in the American .lournal of Sciencf, and subse- 
 quentl}' more in detail, February, 1805, in a comnumication to the 
 Geological Society of London.! i'l*^')' were speedily verified by 
 Dr. Giimbel, who was then engaged in the study of the ancient 
 cr^'stalline schists of Bavaria, and soon recognized the existence, 
 in the limestones of the old Ilercynian gneiss, of tlie characteris- 
 tic Eozoon C<inadeiise, injected with silicates in a maimer precisely 
 similar to that observed by Dawson and myself. J Later, in LSOl), 
 Robert IIoHmann described the results of a minute chemical exam- 
 ination of the Eozoon from Kaspenau. in Bohemia, connrining the 
 previous observations in Canada and Bavaria. lie showed that 
 the calcareous shell of the Eozoon, examined by Iiim, had been in- 
 jected by a peculiar silicate, which may be described as related in 
 composition both to glauconite and to chlorite. Tlie masses of 
 Eozoon he found to be enclosed and wrapped around by thin al- 
 ternating layers of a green niagnesian silicate allied to picrosmine, 
 and a brown non-magnesian mineral, which proved to be a hy- 
 drous silicate of alumina, ferrous oxyd and alkalies, related to 
 fahlnnite, or more nearly to jollyte in composition. § 
 
 Still more recentl^^ In the course of the present year. Dr. Daw- 
 son detected a mineral insoluble in acids, injecting the pores of 
 
 *Anu'r. .lour. Sci., II, xl. 3(iO, Koport Geol. Survey Ciiniuln, 18<I0. ji. 231, aiul Quar. 
 Geol. Jour , XXI, 71. 
 t Amer. .Jdur. Sci., II, xxxvii. 431. Qunr. Geol. .Tour., XXI, 07. 
 i Proc. ISoyal Hiivar. Acad, for 18i!0, and Can. Naturalist, new series III, Sfl. 
 § Jour. fur. I'rakt. Ciiciu., Jlny, IWJ, nnd Amer. Jour. Sci., Ill, i, ;i78. 
 
OmOIN OF CRYSTALLINE UOCKS. 
 
 66 
 
 crinoidal stems and plates in a paleozoic limestone from New 
 Ihunswick, whieli is made up of organic remains. This silicate 
 which, in decalcilied specimens, shows in a beautifnl manner the 
 intimate stnietnre of these ancient crinoids, I have fonnd l)y analy- 
 sis to be R hydrons silicate of alnmina and ferrous oxyd, with 
 magnesia and alkalies, closely related to fahlnnite and to joUyte.* 
 The microscopic examinations of Dr. Dawson show that this sil- 
 icate injected the pores of the crinoidal remains and some of the 
 interstices of the associated shell-fragments, before tiie introduc- 
 tion of the calcite which cements the mass. I have since found a 
 silicate almost identical with this, occurring under similar condi- 
 tions in an Ui)i)cr Silurian limestone said to be from Llangedoc in 
 AVales. 
 
 Giimbel, meanwhile, in the essay on the Laurentian rocks of Ba- 
 varia, in JSOCi, already referred to, fully rei-ognized the truth of 
 the views which I had put forward, both with regard to mineralogy 
 of Eozo(iu and to the origin of the crystalline schists. Ilis results 
 are still farther detailed in his Gcnrpiost. Bcschrcibinid den listbayeris- 
 ches (ir('nz('(j('hir(i('x, IHds, p. >s;5.'5. Credner, moreover, as he tells 
 us,f had already from his mincralogical and lithological studies, 
 been led to admit my views as to the original formation of serpen- 
 tine, pyroxene and similar silicates (which he cites from my paper 
 of 18()0, above referred to J), when he fonnd that Giimbel had ar- 
 rived at similar conclusions. The views of the latter, as cited by 
 Credner IVom the work Just referred to, are in substance as fol- 
 lows : — The crystalline schists, with their interstratilied layers, 
 have all the characters rf altered sedimentary deposits, and from 
 their mode of occurrence cannot be of igneous origin, nor the result 
 of epigenic action. The originally Ibrmed sediments are conceived 
 to have been amor])hous. and under moderate heat and pressure to 
 have arranged themselves, and crystallized, generating various 
 mineral species in their midst by a change, which, to distinguish it 
 from metamorphism by an epigenic process, Giimbel lia[)pily des- 
 ignates (h'agenesfs. 
 
 It is unnecessary to remark, that these views, the conclusions 
 from the recent studies of Giimliel in Germany and Credner in 
 North America, are identical with those put forth by me in 18(50. 
 
 * Amer. .Toiir. Sci., HI, i. :t7n. 
 
 t llenuaiin C'rccliier; die Gleiilerung der Eozoischen Forinntionsgrnppe Nord Amer- 
 ikap. Iliille 180!). | That in the Quar. Guol. Jour., XXI, (i". 
 
 . 
 
56 
 
 ADDRESS OP T. STEUUY lUTNT. 
 
 At the early periods in whie-h (ho iniiteriulH of the ancioiit crys- 
 talline schists were accunnilated, it cannot be (hjulttod that the 
 chemical processes wliicii f2;cii('ratcd silicates were nuicli more ac- 
 tive tiian in more recent limes. The heat of the earth's crnst 
 was probably thi'n far greater than at present, while a high tem- 
 perature prevailed at comparatively small depths, and thermal 
 waters abounded. A denser atmosplicre, charged with carbonic 
 acid gas, nuist also have contributed to maintain, at the earth's 
 surface, a greater degree of heat, though one not incompatible 
 with the existence of organic life. * These conditions nuist have 
 favored man}'- chemical processes, Avhich, in later times, have 
 nearl\' ceased to operate. Hence we find that subse(inently to 
 the eozoic times, silicatcd rocks of clearly marked chemical ori- 
 gin are comparatively rare. In the mechanical sediments of later 
 periods certain crystalline minerals may be developed by a process 
 of molecular re-arrangement — diagenesis. These are, in the feld- 
 spathic and :iluminous sediments, orthoclase, nuiscovite, garnet, 
 staurolite, cyanite and chiastolite, and in the more basic sedi- 
 ments, liornblendic minerals. It is possible that these latter and 
 similar silicates may sometimes be generated by reactions l)etween 
 silica on the one hand, and carb(niates and oxyds, on the other, 
 as already pointed out in some cases of local alteration. Such a 
 case ma}'^ tvpply to more or less hornblendic gneissea, for example, 
 but no sediments, not of direct chemical origin, are pure enough 
 to have given rise to the great beds of serpentine, pyroxene, stea- 
 tite, labrad(mte, etc., which abound in the ancient crystalline 
 schists. Thus, while the materials for producing, by diagenesis, 
 the aluminous silicates just mentioned, are to be met with in the 
 nnid and clay-rocks of all ages, the chemically formed silicates, 
 capable of crystallizing into pyroxene, talc, serpentine, etc., have 
 only l)een formed under special conditions. 
 
 The same reasoning which led me to maintain the theory of an 
 original formation of the mineral silicates of the crj'stallinc schists, 
 induced me to question the received notion of the epigenic origin 
 of gypsums an<l magnesian limestones or dolomites. The inter- 
 stratilication of dolomites and pure limestones, and the enclosure 
 of pebbles ol' the latter in a paste of crystalline dolomite, are of 
 themselves sufficient to show that in these cases, at least, dolo- 
 mites have not been formed by the alteration of pure limestones. 
 
 • Amev. Jour. Scl., II, xxxvi, 390. 
 
OUIUIN OV CnVSTALLINE KOCKS. 
 
 57 
 
 The flr.st rcsultH of a very loiif? series of experiinonts and iiuiuiries 
 into tlie liistory of gypsum, were |)iil)liMlie(l hy nie in IHoK, and 
 lartluM" rcsearclies, reiteratinf; and coiiHrniing my previous conclu- 
 sioMH, appeared in IHfK!.* In these two papers, it will, I think, be 
 found tliat the following facts in the history of dolomite are es- 
 tablished, viz. : first, its origin in nature b}' direct sedimentation, 
 and not by the alteration of non-magnesian limestones ; second, 
 its artificial production by the direct union of carbonate of lime 
 and hydrous carbonate of magnesia, at a gentle heat, in the pres- 
 ence of water. As to the sources of the hydrous inagnesian car- 
 Ijonate, I have endeavored to show that it is formed from the 
 magnesian chlorid or sulphate of the sea or other saline waters in 
 two ways: — first, by the action of the l»icarbonate of soda found 
 in many natural waters ; this, after converting all soluble liini'-salts 
 into insoluble carbonate, forms a comi)aratively soluble bicarbon- 
 ate of magnesia, from which a hj'drous carbonate slowly separates : 
 second, by the action of bicarbonate of lime in solution, which, 
 with suli)hate of magnesia gives rise to gypsum ; this first crystal- 
 lizes out, leaving behind a nuich more soluble bicarbonate of mag- 
 nesia, which deposits the hydrous carbonate in its turn. In this 
 way, for the first time, in iSui), the origin of gypsums and their in- 
 timate relation with magnesian limestones were explained. 
 
 It was, moreover, shown that to the perfect operation of this re- 
 action, an excess of carl)onic acid in the solution, during the evap- 
 oration, was necessary to prevent the decomposing a(ttion of the 
 hydrous mono-carbonate of magni'sia upon the already formed 
 gypsum. Having found that a prolonged exposure to the air, by 
 permitting the loss of carbonic acid, partiall}' interfered with the 
 process, I was led to repeat the experiment in a confined atmos- 
 phere, charged with carbonic aciil, but rendered drying by the 
 presence of a \nyci' of dessicated chlorid of calcium. As had 
 been foreseen, the process under these conditions proceeded unin- 
 terruptedly, pure gypsinn first crystallizing out from the licpiid, 
 and siibsequently, the hydrous magnesian carbonate. I This ex- 
 periment is instructive as showing the results which must have 
 attended this process in past ages, when the quantity of carbonic 
 acid in the atmosphere greatly exceeded its present amount. 
 
 OR 
 
 * Anicr. Jour. Sci., II. xxxviii, 170, 305; xlii, 49. 
 
 t Proceedings Uoyal lustitutiou, Jlay 30, 18(j7, and Canadian Natiu-alist, new soriea, 
 111,231. 
 
r)8 
 
 ADDRESS OF T. STKUIIY HUNT. 
 
 As rcgnnlH the hypotheses put forwaitl to cxphiln the Hiipposcd 
 doloinitiziition of prcviously-tbriiu'd liineHtones by un epij^i'iiic 
 proccHH, I iriiiy rciimik Ihiit I repented very nmiiy tiineH, under 
 vuryiii«i eonditioiis, the often eited experiment of Von IVIorh)t*, who 
 chiinied to have j^enerated dolomite by the aetion of H(di)liate of 
 maj^iiesiaon earl)onate of lime, in the presence of water at a some- 
 what elevated temperature under pressure. I showed that what 
 he regarded as dolomite was not sueh, but an admixture of carlion- 
 ate of lime with anhydrous and sparinjily soluble carbonate of 
 matjjnesia ; the conditions in which the carbonate of maj>nesia is 
 liberated in this reaction, not bein<; favorable to its union with the 
 carbonate of lime to form the double salt which constitutes dolo- 
 mite. The experiment of IMarijiiiac, who thouffht to form dolomite 
 by substitutin<>" a solution of chlorid of maiiucKium for the sul- 
 phate, I found to yield similar results, the •greater part of tlu' mag- 
 nesian carbonate produced passing at once into the insoluble 
 condition, without (combining with the excess of carbonate of lime 
 present. The process for the production of the double carbonate 
 described by Ch. Deville, namely, the action of vapors of anhy- 
 drous magnesian chlorid on heated carbonate of lime, in accord- 
 ance with Von Jhich's strange theory of dolomitization, I have not 
 thought necessary to submit to the test of experiment, since the 
 conditions reciuired are scarcely conceivable in nature. Multiplied 
 geognostical observations show that the notion of the epigenic 
 l^roduction of dolomite from limestone is untenable, although its 
 resolution and deposition in veins, cavities, or pores in other rocks 
 is a phenomenon of frcfiuent occurrence. 
 
 The dolomites or magnesian limestones ma}' be convenientlj' 
 considered in two classes ; first, those which are found with gyp- 
 sxnns at various geological horizons; and second, the more abun- 
 dant and widel}' distributed rocks of the samc^ kind, which are not 
 associated -with deposits of gypsum. The i)ro(biction of the first 
 class is dei)endent upon the decomposition of sulphate of magne- 
 sia by solutions of bicarbonate of lime, while those of the second 
 class owe their origin to the decomposition of magnesian chlorid 
 or sulphate by solutions of alkaline bicarbonates. In both cases, 
 however, the bicarbonate of magnesia, which the carbonated 
 ■waters generally contain, contributes a more or less important 
 part to the generation of the magnesian sediments. The carbon- 
 ated alkaline waters of deep-seated springs often contain, as is 
 
«>UiaiN OK CRY8TAI.MNK HOCKS. 
 
 09 
 
 well known, l)osi(loH tho hicurhoniiU'a of soda, limo, nml mafinc- 
 sia, I'onipoiMKls of iron, niiinjfiinosi", nnd nmny «)!" tin' niriT metals 
 in Holulioii, and tlms tlio nictullitVrous ciiaraclcr of n)any of the 
 doloniitt's of the .socond class is oxplainod. Tho siinultanoons 
 oocniiToncc of alkaline silicates in sneli mineral waters, wonld 
 give rise, as already pointed out, to the production of insolulde 
 silicates of ma}j;nesia, and tiuis the fre(|uent association of such 
 silicates with dolomites and ma<j;ncsian carltonates in tiie crystal- 
 line sciiists is explained, as markinji; portions of one continuous 
 process. The formation of these mineral waters depends upon 
 tlie decomposition of feldsi)athie rocks by subterranean or sub- 
 aerial processes, which were doubtless more active in former ages 
 than in our own. The sul»se(|uent Jiction upon ma<^nesian waters 
 of tliese bicarhonated solutions, whetlier alkaline (jr not, is de- 
 pendent upon climatic conditions, since, in a region where the rain- 
 full is abundant, such waters would And their way down the river- 
 courses to the open sea, where the excess of dissolved sulphate of 
 linu! would prevent the deposition of magnesian carbonate. It is 
 in dry and desert regions, with limited hike-basins, tliat avc must 
 seek for the production of magnesian carbonates, and I have ar- 
 gued from these considerations that nuich of northeastern Amer- 
 ica, including the present basins of the Upper Mississippi and St. 
 Lawrence, must, during long intervals in the paleozoic period, 
 hi; e iKid a climate of excessive dryness, and a surface marked by 
 shallow enchjsed basins, as is shown by the widely sjjread magne- 
 sian limestones, and the existence of gypsum and roclc-salt at 
 more than one geological horizon within that area.* The occur- 
 rence of serpentine and diidlage at Syracuse, New York, otters a 
 curious exami)le of the local development of crystalline magne- 
 siau silicates in Upper Silurian dolomitic strata under conditions 
 which jire imperfectly known, and, in the present state of the 
 locality, cannot be studied, f 
 
 Since the nncombined and liydrated magnesian mono-carbonate 
 is at once decomposed by sulphate or chlorid of calcium, it fol- 
 lows that the whole of these lime-salts in a sea-l)asiii must be 
 converted into carbonates before the production of carbonated 
 magnesian sediments can begin. The carbonate of lime, formed 
 
 ♦Geology of Southwestern Oiitiivio, Amer. .lour. Sci., II, xlvi, 35."). 
 ttieologyof tlio;iil ilisti-ict of New York, 108-110. auil Iluut on OiiliiolitcK, Amor. Jour. 
 8ci., II, x.wi, 'i'iii. 
 
60 
 
 AI>lt»KS« or T. STKUUY lIlfNT. 
 
 by Iho lU'tion of carbonates of inajfiusia and soda, iTinaiiiM at llrst 
 diHHolvod aH bicarbonato, and is only soparatod in n solid form, 
 wluMi In excess, or when roiiiiircd for the needs of living plants 
 or animals; which an* dependent for their snpply of calcareous 
 matter, on tlu' Iticarbonate of lime prodncod, in pint by the proc- 
 ess just described, and in part by the action of (■ail)()nic acid on 
 insoluble lime-coni[>()iinds of the earth's solid crust. So many 
 limestones are made up of calcareous orpuiic remains, that a 
 notion exists anion}? nmny writers on geolojiy that all limestones 
 ar<', in some way. of organic origin. At the bottom of this lies 
 the idea of an analogy l»etw<'cn (he chemical relations of vege- 
 table and animal life. As plants give rise to beds of coal, so ani- 
 mals are supposed to produce limestones. In fact, however, the 
 synthetic process by which the growing plant, from the elements 
 of water, carbonic acid and ammonia, generates h^-drocarbonace- 
 ons and azoti/eil matters, has no analogy with the assimilative 
 process by which the growing animal a[)pro|)riates alike these or- 
 ganic matters and the carl)onat(! and i)hosphatc of lime. Without 
 the plant, the synthesis of the hydrocarbons would not take place, 
 while independently of the existence of coral or mollusk, the car- 
 bonate of lime would still be generated l)y chemical reactions, and 
 would accumulate in the waters until, these being saturated, its 
 excess would be deposited as gypsum or rock-salt arc deposited. 
 Hence in such waters, where, from any causes, life is excluded, 
 accunndations of pure carbonate of lime maybe formed. In 18r>l 
 I called attention to the white marl ties of V^ermont, which occur 
 intercalated among imi)ure and fossilifcrous beds, as apparently 
 examples of such a process.* 
 
 It is by a fallacy similar to that which prevails as to the or- 
 ganic origin of limestones, that Daubeny and Murchison were led 
 to appeal to the absence of phosphates from certain old strata as 
 evidence of the absence of organic life at the time of their accu- 
 midation.f Phosphates, like silica and iron-oxyd, were doubtless 
 constituents of the primitive earth's ci'ust, and the production of 
 apatite crystals in granitic veins, or in crystalline schists, is a proc- 
 ess as independent of life as the formation of crystals of quartz 
 or of hematite. Growing plants, it is true, take u\) from the soil 
 or the waters dissolved phosphates, which pass into the skeletons 
 
 * Ainer. Jour. Sci., II, xxxi, 402. , 
 
 t Siluria, 4Ui eil., pp. 28 luul 537. 
 
ORIGIN OF CRYSTALLINE HOCKS. 
 
 61 
 
 of aniiiialM, n procoHH which has been active from very roinoto po- 
 riocU. 1 HhovvHMl in IH.'ti tliat tlie Hhetln of Liii^uUi and Orliiciihi, 
 both those from the liase of the i)ah'o/oie roeks and those of the 
 present (inie, liave (lik(r Coiiuhiria and Serpniiles) a clieinieal com- 
 position siniihir to the skeletons of vertebrati' animals.* The 
 relations of l)otli carbonate and |)hosphate of lime to or<>'ani/ed 
 beinjrs nre similar to those of siliea, whieh, like them, is held in 
 watery sohition, and by processes independent of lif(^ is deposited 
 b(jth in aniorphons and cr^'stalline forms, l)nt in certain eases is 
 appropriated by diatoms and sponj^es. and made to assinne or<;an- 
 ized shapes. In a word, the assimilation of silica, like that of 
 phosphate and carbonate of lime, is a pnrcly secondary and acci- 
 dental process, and where life is absent, all of these substances 
 are deposited in mineral and inorganic forms. 
 
 1 have thus endeavored to sketch, in a c(»ncise and rapiti man- 
 ner, the history of the earlier rock-formations of eastern North 
 America, and of our [)ro<iress in the knowle<l<j;e of them ; while 
 I have, at the same time, dwelt upon some of the }{eojj;nostical 
 and chemical (piestions which their study sufj^ffcsts. With the 
 record of the last thirty years before tlu-m, American {jjeologists 
 liave cause for congratulation that their investigations have been 
 so fruitful in great results. They see, however, at the same time, 
 how nuich yet remains to be done in the study of the Appalachians 
 and of our northeastern coast, before the histor\ of these ancient 
 rock-formations can be satisfactorily written. Meanwhile oin* ad- 
 venturous students are directing their labors to the vast regions of 
 western America, Mhere the results which have already been ob- 
 tained are of profound interest. The progress of these investiga- 
 tions will doubtless lead v.h to modify many of the views now 
 accepted in science, and cannot fail greatly to enlarge the bound 
 of geological knowleilge. 
 
 * Amer. Jour. Sci., II, xvii, 23(i. 
 
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 Chemistry of the Primeval Earth. (Proc. itoyal Inst. 1807) pp. 8 10 ■• 
 
 Chemical Geology; replies to David Forbes. (Geol. Mag. and Chem. News, 
 
 Feb. 1808) pp. ;U _'._,,, „ 
 
 Chemistry of the Globe. (Smithsonian Report 1809) iip. -20 ..>.-, >• 
 
 Contributions to Lithology; Kruptive Uocks. (Sill. ,7„„r. 18(lt) pp. r.l . . . .-,0 « 
 
 llist(ny of Ophiolitcs; parti. Sill. .Tour. I8.-.I)) pp. lo j„ .. 
 
 Euphotide and Saussurite. (Sill. Jour. 18.-)i)) pp. i,") ,„ ., 
 
 On some Fehlspathic Uocks iXorites). IMiilos. Mag. LsTw) pp. 10 ..... 10 •■ 
 
 Norite or Labradorite Rock. (sill. Jour. 180!)) pp. 7 I„ .. 
 
 Notes on Granitic Uocks; parts I and 11. (Sill. Jour. 1871) pp. 20 20 '• 
 
 History of Kozoon Canadense; with plate. Sill. -Jour, hsor,) i)p. 20 .... 2,'i " 
 Mineralogy of Lauientian Limestones. Geol. Survey Canada 18(;0 ; reprinted 
 
 with additions. Uop. Uegents- Univ. N. York. 180!)) PI., to go " 
 
 Chemistry and (Jeology of Natural Waters, (sill. Jour. 18ir.; pp. (17. . . . ,-,„ .. 
 
 Chemistry of Gypsums and Dob. mites. (Sdl. Jour. 18.1!)) pp. ,!7 25 " 
 
 *' continued. (Sill. Jour. Isoo) pp. li) . . jo " 
 
 Siliclllcation of Fossils. (Can. Xatunillst. I80t) p|i. 4 I„ .. 
 
 Notes on the IILstory of Petroleum. (Can. Xaturali-st, 1801) pp. 1,5 ._,,r, .. 
 
 Chemistry and Geology of Hitunu'ns and Pyroschists. Sill. -Tour. 180;j) pp. |.-, p, .. 
 
 Oil-be.u-ing Limestone of Chicago. (Sill. Jour. 1871.) pp. .-i p, .. 
 
 Geology of the .Vlps. (Sill. Jour. 18'i0) pp. 7 I„ .. 
 
 Progress of American Geology. (.Sill. Joui\ 1801) pp. J.") •>.-, .< 
 
 < ieology of South western Ontaiio. (Sill, .|„iir. isos) pp. 10 ]„ ., 
 
 Laurentian Uocks of Eastei-n Massachnsotts. (Sill. Jour. Is70) pp. ;! . . . p» •• 
 
 Geology of Eastern New Enuland. (sill. , Jour. 1870.) pp. 7 ]o " 
 
 Gc(dogy of the Vichiily of IJoston. (Uoston X;it. Hist. Soc. 1870) jjp. s . . pi ••