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 TRI&H AND CANADIAN R0CK8, 
 
 co.MrARi:D. 
 
 [ExtracteJ from tht CFc.i.oniCAl. Maga/.ink, April, 1SS5.] 
 Trlbner & Co , 57 and 59, Lmlgate Hill, London. 
 
 \ 
 
^Exlrncled frnin ///e G i".o log km, MA(iA/.iNK, Doomle HI. Vol. 11. 
 No. 4, p. 1")'.), April. 1S8(1] 
 
 Canadian Arcilean ok Pke-C.^mbrian Rooks and the Irish 
 Metamokphk^ Kocks. 
 
 liy (J. IIemiy Kinahan, M.li.L.V., etc. 
 [KciiJ before the Royal Geological Society of Ireland.] 
 
 "" i 
 
 low ^ 
 and ^ 
 
 AS introiluctory to the subject of this paper, some observations 
 made in Irelunil on foliation, or the structure induced by 
 nietamori)hisni, with other phenomena connected therewith, will be 
 submitted. 
 
 Students of Petrolo<];y and Litholo<;y seem now in general to all 
 
 that there are three kinds of metamorphism, namely Reji;ional 
 
 Contact, for which I have proposed respectively the terms lifetapepsia . 
 and Paroptesis.^ and Chemical change, to which King of Galway ' ^ 
 gave the name Methylusls, while more recently the Americans called-"^^ 
 .^Farivnorphosis. At the present time it is not intended to refer to 
 the latter, as these preliminary remarks refer specially to the others. 
 
 In one and the same area Paroptesis or Contact metamorphism 
 must necessarily occur at a different time to 3Ietapepsis or Regionr.l 
 nietamorpliism ; and the first may take place either before or after 
 the other ; or possibly there may have been two or moi'e successive 
 actions which affected the rock or rocks of one area ; as, for instance, 
 first in places there may have been Paroptesis, while subse(juently 
 these altered rocks were included in a Metapepsis area, while after- 
 wards in portions, or the whole of the area Paroptesis or Metapepsis 
 may again have taken place ; because, as long ago pointed out by 
 Lyell, vulcanicity often occurs over and over again, even with ages 
 between, in one place or one area. In places the present structure 
 of some of the Canadian Archreans would suggest that they were sub- 
 jected to a succession of periods of alteration, some due to Paroptesis, 
 others to Metapepsis ; to this subject we will hereafter return. 
 
 ' Geology of Ireland, p. 1".">. 
 
 3'7 / 6'/ 
 
H'O G. II. Kinalfttn — Iri^li <ind ('inirn/iaii llochs, CoiiijiiirciJ. 
 
 Tlifi soiitli-east of Trflaiiil is very instructive, as on ImiIIi ^ides of 
 tlie ril) of j^runitc of tiu; Lcinstcr raiij;<' tlicie are l)ati(ls of I'arnptesis 
 roeks ; Imt wiiiie tluj^e to westward of the rili, with some peculiar 
 exceptiuiis licreal'ter Tiietitioiicd, n laiii their I'aroptesis form, those 
 ill the liaiid to the eastward of the ril) have been ciianp'd into gneiss 
 and sclilsf l.y till- Mrtajiepsis that snlisi(jii(.ntiy invaded those por- 
 tii>nsof tiie counties of Did.lin, Wiciclow and Wexford. Tlierefore 
 we have an a ijeturnl nile to the westward of tlie granite rib a band 
 of "baked rocks" (iliie to I'aroptesis), while eastward of the rib 
 there is a band of gmiss and schist (dne to Parojitesis and subse- 
 quent Metiipe|>sis), outside of wjiich are sub-nietamorphic rocks. The 
 nietaj)eptic action that invaded the latter area seems to liave been 
 most intense in lines running about E.N.F]. and W.S.W., so that if 
 we traverse the county from south to north, we cmss over zones of 
 "8id,metainorphic rocks" and of rocks Ixdonging to the "Schist 
 Series ; " ' that is, if we ignore other metamorphic actions now to be 
 mentioned. 
 
 In this region, besides the intrusion of the normal Leinster granite 
 (Haughton's typej, which is supposed to huve taken i)lace in Post 
 Cambro-Silurian time, there were also newer intrusions that may 
 have occurred in Devono-Silurian - times; and as the latter were 
 accompanied by Paroptesis, tlie rocks in connection with them are 
 additionally altered ; the "baked rocks" to the westward of the rib 
 being changed into schists, while to the eastward of the rib they 
 have had the metainorphism intensified. There is also to bo con- 
 sidered what may have been the effect of the granitic roots (the 
 laccoliths of CJilbert) of the eruptive rocks contemporaneous with 
 the Cambro-Silurians, as tliese also seem to have had Paroptesis in 
 connection witli them, and this necessarily was prior to the Metapepsis 
 of the district. Although the etl'ect of tliis Paroptesis is not now 
 very conspicuous, yet it should be mentioned, as it shows how many 
 diflferent times the same rocks may be subjected to metan. orphi'c 
 action of some kind or another. 
 
 There is also in this area a peculiarity in the raetamorphism. 
 Years ago Jukes pointed out that the younger or Cambro-Silurian 
 rocks were mere altered than the older Cambrians ; and suggested 
 that it might be more apparent than real, as none of the Camljrians 
 in contact with the granite were exposed. P>ut down in the south- 
 east of the Co. Wexford, away from the granite rib, the same thing- 
 occurs ; as nearly invariably along the boundary between the 
 Cambrians and the Cambro-Silurians the last are more altered than 
 the first.' 'Jo the north-west and westward of Kathdrum, Co. 
 
 ' Ibid, Chapter x. paije I'o. 
 
 " Til tlie old world the terms Lower Siluriim, Upper Silurian, Devonian and Lower 
 Old Red San(l>toiie are used so iudiscriniinately tliat it is hard to know exartly what 
 rocks are meant. In this paper Schvvu will be loUowed and to iiiditate Lower 
 Silurians I'liillips's term Ciimhiv-Hiluniin will be used, while all the others will be 
 iiuluded umler the term lHr<jinj-Silnn,in. 
 
 ^ In coiiiiection with this nietamoi-phisni of adjciiuinjr roeks, it may be mentioned 
 that iu the Helvoir section (('anilir()-Siliiriau\ Co.' Clare, there are soinc beds in the 
 lossiliterous ftrata altertd apparently tor no particular reason. 
 
O. n. Kinnhnn — Irish a iff Canadian Rocks, Compared. lOl 
 
 Wicklow, tlioro are rocks that Wyloy considored to ho iiu'ta- 
 morplinscd CiiDln-iiiu, but .Jiikcs put tliem in the C'ainhro-Sihiiiaiis. 
 As lias lii'eu incut ionod in my ilcscription of flie Irish rocks, I beliove 
 Wyley was n;;lit, and that Jukes was mistaken l.y supposing that iio- 
 wher.j in tlieuuunly wore Camhrian rocks S( nuicfi altered. Thi.) 
 confusion due to dilferent kinds and times of metaniorphism, will ho 
 referred to hereafter when speakinjjj of the Canadian rocks. 
 
 The Camln-ians of the Carnsoro district (S.E. Wexford) illustrate 
 some peculiar jjhases in iiietamor|)hisni. If you follow the rocks 
 iu)rthward from Carnsore l)y Carne to Greenore, there are ; first, 
 oligoclasic porphyritic <;ianite, then oli<jj(Hdasic porphyritic granitoid 
 gneiss or gneissic granite, that graduates through gneiss into schists. 
 Go, however, a sliort distance westward, and on the Saltces Island 
 are^ found orthoclasic gneissic granites, usually fine-grained, in 
 which are a few subordinate hornblendites i hornblende-schist), while 
 on the mainland at Forlone Point ; Kilniore Tier) tliere are at the 
 South hornblendites, that by an alternation of beds graduates into a 
 considerable thickness of orthoclasic fine granitoid gneiss ; the last, 
 to the north, has a hard boundary, outside of which are horn- 
 blendites and other schists. This sudden change in lithological 
 characters is important. 
 
 In the .Mourn Mountain district. Co. Down, there are two distinct 
 intrusions of granite, tlie first, "ISlieve Croob granite,"' pnjbably at the 
 close of the Cambro-Silurian period, and the second at the close of 
 the Carboniferous period. The Cambro-Silurian rocks of the country 
 are altered (sub-metamorphic) by Metapepsis, probably an adjunct 
 of the genesis of tiie older granite ; but subsecpiently a new ineta- 
 niorphic action invadeil the rocks in the vicinity of the boundary 
 between the granite and sub-n;etamorpliic rocks, changing the latter 
 into gneiss and developing a foliation in the granite, the rocks now 
 occurring in tiie following order : — 
 
 1. Granite ) „,, . . , . . 
 
 2. Gneissic granite | ^'"^ °'''°"'^' S™"^'' intrusion. 
 
 3. Hard bouuaary. 
 
 4. Gneiss 
 
 5. Schists 
 
 The original submetamorphic rocks. 
 
 The newer granite (Post-Carboniferous?) has not to any great 
 extent altered the adjoining strata ; but at the same time more or 
 less signs of Paroptesis are ap{)arent. 
 
 In the Counties (Jidvvay and Mayo different phases of metamor- 
 phisin can also be studied. At first tlie metaniorphism may appear to 
 follow general rules, but when details are entered into, here as 
 elsewhere, peculiarities hard to be explained are found. 
 
 If a traverse is made northward from Furbogh, west of Galway 
 town, to Oughterard across the strike of the rocks, you start from a 
 tract of i)<)rphyritic oligoclasic granite tliat merges into porphyritic 
 oligoclasic gneissic granite, while the latter graduates through gneiss 
 into schists ; still further north in the Co. ]\Iayo these schists merge 
 luto unaltered Cambro-Siluriau rocks. Althoujrh across the strike 
 
 
Ifi'J (1. II. Kindliuu — Trixli (IIkI Ctinddimi Rocks, Cn/ii/mrrd, 
 
 tliL' ^iwissic m'.iiiitc <;oiipr.illy Kriidiifites into pjiieiss, yot in some 
 |il:u'('S, tliiTt' is fi Ii.imI IiiimikIihv lictwccn tlioiii. 
 
 It' till! rocks, liowfvor. mo I'nlldwt/il WLStwaiii uloiip; tlie Htril<e of 
 tlio rocks, till- cliani^o is not so ^radiuil. as tliere iire rather Hiiddcii 
 ]ii!!i])S fVoDi granitic to schistose neks ; wliilo in the latter aro 
 toinnl outliers, cither havinj^ a nucleus ot" porjihyritic olifijoclasio 
 <;ianite, ur heiiij; entirely j^neissic "granite. 'I'hese usually fH'O 
 suddenly rejihu'ed hy schists, as it' they were small tracts which had 
 Iteen sulijected to an extra action, prior to the time of the regional 
 nietamor[iliism. 
 
 Hut if we go southward from the mass of the poiphyritic oligo- 
 clasic granite, there is a complete change in the character of the 
 nietamorphism ; as here in places margining it are gneissic granites 
 often orthoclasic and fine-urained, hut having associated, and alternat- 
 ing with them, coarse-grained and oligoclasic beds. While to the 
 S.E.. at Gahvay town, there is a complete change of rocks, 
 princijially hornhlendites, that come in against the granite, and in a 
 few small patches on it. This small area of schist apparently in 
 such close proximity to the mass of the oligoclasic i)orphyvitic 
 granite seems jteculiar. This, however, might perhaps be explained 
 by phenomena that can be studied to the westward near Koundstone 
 and Slyne Head ; but as it would take some time, and the rocks are 
 not of interest in the present inquiry, it appears sufficient to liave 
 recorded their presence. 
 
 In the Co. Galway the oligoclasic porphyritic gneissic granite, 
 especially' across tlie strike of the rocks, is a portion of the general 
 graduation from the oligoclasic porphyritic granite into the schists 
 and unaltered rocks : but in the Castlehar district, Co. Mayo, there 
 are courses and masses of it that evidently were intruded into their 
 present positions. 'I'hese Mayo rocks are very interesting, because 
 among tlie Laurentians of Canada we find somewhat similar gneissio 
 granite as intruded masses (called Labiadorians and Norians by the 
 Canadian geologists and marked La on Selwyn's map). 
 
 From the pulilished writing in connection with the oligoclasic 
 granite and associated rocks of the Co. Donegal, it is evident that 
 the sequences are .somewhat similar to those in the Counties Galway 
 and Wexford; tliere being granite that in places graduates through 
 gneiss into schist; while in ither places, as at the south of the 
 Galway, porphyritic granite, dift'erent groups of gneissic rocks, comes 
 in. At the same time, however, as a general rule, the margin of 
 the granitoid rooks is here more marked than in either Galway or 
 Wexford. 
 
 It is nnnecessarj' to further individualize the Irish localities ; but 
 to certain traits of nietaniorphism I would draw attention. Years 
 ago I iHiinted out ' that in the West Galway and Mayo districts, rocks 
 in the " Second Stage " ^ of nietaniorphism followed the planes of 
 the most consjiicuous structures in the original rocks ; let this struc- 
 ture be lamination, cleavage, fine jointing, oblicjue laminutit)n, 
 spheroidal structure, concretionary structure, or any of the wavy 
 
 Gkol. Mao. 1S71, Vol. VIII. pp. 26;j-208. - Gcol(i;;v of Irelaud, cLapter x. 
 
G. 7'. Kiiiiihnn — Tr'mh rtml Canadian Rocka, Compainl. 1(53 
 
 Btnictures peculiar to some calcareous or allieil rocks; wliilo in the 
 typical j^Tici.Hsic j^raiiito or f^ranitoid giici.sH.all tlic oriffiiial stnictiinl 
 linos are oi)litcratO(l ; tliey or any siilmfvjiient foliatiun beinj; replaceil 
 by a nearly pcrpeadicular one ; Imt llie strata of tliis new foliation 
 seems to follow tlio strike of tlie original Ntralificaliun. 
 
 In some places tlicrc is a liarl hoMinlary between tlio j^neissic 
 granite and tiio j^neiss; or tlie latter may bo absent, the granite 
 ])eitig margined by schist. 'I'his seems to suggest that it is possible 
 tiie coarse foliation of the gneissic granite may 1)0 duo to a second 
 IMetapopsis of a more limited extent ; tliat while it atVacted them ami 
 doveloited the leaves of foliation, it did not invade .lie adjoining 
 strata. We will now proceed to the iiietamorphic rocks of Canada.' 
 
 A feature that strikes a stranger is the massive coarseness of the 
 foliation in some of tfie Laurentian gneiss. 'I'his appears to me, as 
 mentioned in connection with the Irish rocks, to bo duo not to exces- 
 sive metamorphism at one and the same time; but to stages, the 
 rocks having been invaded two, three, or even many more times by 
 successive but independent periods of metamorphism ; thus develop- 
 ing but not obliterating tlie leaves duo to the earlier inotamorphisms.^ 
 
 This coarse foliation is very conspiciiciis in the previously men- 
 tioned gneissic granite called Lal)radorians by the Canadian geolo- 
 gists. Of it we have no exact representatives among the Irish rocks; 
 the nearest approach in structure being the gneissic granites of 
 Carnsore, co. Wexford : of the barony of Sloycullen, co. Galway ; of 
 the Krris district, co. Mayo ; and of the ('astlebar district, also in 
 JIayo. The latter being an intrusion, is in this respect more like 
 the Canadian rocks than the others, which were originally stratified 
 rocks.' 
 
 ' It appcurs rfTiiarkalilo that metamorphism seems to he so restricted to tlie older 
 roiks in CaiKida. Is it possil)le. that in the areas calhd Arehiean, from tlieir 
 litlioloirieal eharaeter, there may he newer roekn included;- If not, why should 
 mitamoiphism he so contined to them, when in a little spot like Ireland we have 
 metamorphosed Camhriaus, Canihro-tjilurians, JJevono-Sdurians, Carhoiul'erous ('-) 
 and bias. 
 
 - Fxcessive metamorphic action in a portion of an area will ehanire rocks into 
 granite ; but if a milder metamorphism invades rocks at different successive times, it 
 ouirht to more and more develone the i)lat<s or leaves without oltliteratiufj them. This 
 can he seen on a small scale in ditt'enut places in Ireland, tiie hest perhaps heinjj alonfj 
 the hefore-meiitioned boundary of tlie older, or -'Slieve Crooh" ,'ranitn of the Mourne 
 Jlonntain district. In ^reneral in Irish localities the additional metamorphism seems 
 due to Metapepsis, succeediiiiT I'lropiesis, or vtce vifnu ; but in some places one period 
 of Metapepsis seems to have been followed by another. As the Canadian rocks are so 
 ancient, we may suppose that at least three or four times they have been covered by 
 a sutticient depth of strata to develope metamorphic action, but not sulKcient to 
 convert them into typical irranite. It appears to me an iuterestintr prol)lem, why in 
 such vast areas we should have frueiss without its beinif, in part, converted Into 
 granite of nietamnri)hic orin-in r Inhss we sui)pose that some of the rocks that are 
 now jinciss Were at nue time ^'ranite, but by subse(|Uent metaninr]ili'c action foliation 
 was developed iu it, and thus by deirrees it was chan^red into f^neiss. Such a chanj^o 
 can take place; bei'ause if the "Slieve Croob irranite" was covered up with a 
 Butlicient depth of strata, it would be entirely converted into i^iieiss. 
 
 ^ Mixed up, either as strata or small intrusions, with these rocks of Wexford, 
 Galway, and Mayo, are eruptive rocks; they, however, werj portions of the geo- 
 loirical frroui)s (Cambrians and Canibro-,s;iluri:uis) and not subsequent intrusions, 
 
 J)> was the (JMse in resljeCt to the f Vwllnli'ir (li.ifrir't T».->ri>lM-riti/' mit.ic^ 
 
IGl (1. II. Kniiiliiiii — Irixh (ind Ctnutdinn Rochs^ (^jiiipn/rd. 
 
 Soino of tlie vdiicticH of grniiitc (xro also rcinaik.'ilih! for tlio 
 nmssivo chamctcr of their crystalli/ation, more t'«[ifinally tli<* \>''ii- 
 iiiiUites. Tl.iM, ainoiij^ otlitTH, is very conspicuous in tlic wliitu mica 
 pt'j^inatite of tliu Valo of tliy Dii Lcivn-, Mk! felspar luiii;; in coii- 
 sidorahle nmsscs, wliilo tlie |)hiteM of the white mica arc in places 
 over nine inches acntss. 
 
 These pe^riuatiti's Ix'loti;^ to Storry Hunt's •' Eniloj^enous rocks"; 
 he Ku^j^pstiri}^ that the minerals crystalli/ed out of solution. >5iich 
 a supposition can lie easily un'lerstootl when poj^inatite is found 
 in small masses or in lenticular veins : hut it is not so easily con- 
 ceived when we have to treat with lari^e masses.' Still, however, 
 it is possihle, if not prohahle, that Sterry Hunt may he ri^ht ; as in 
 great thicknesses of rocks there is no reason why there should not 
 1)0 vast vugs tilled with mineral solutions ; ami wiieii the minerals 
 crystallized out, they would fill such cavities, thus forming masses 
 of pegmatite or other rocks that had a similar genesis. In the 
 Aughowle district, co. Wicklow, there is a pegmatite locally called 
 '' l')astaril (Iranitc," a variety of which is the " I'himose (iranitc" 
 of. hikes. This rock occupies a considerahle area, and is somewhat 
 like the Canadian pegmatite, although not as coarsely crystalline. 
 JVom it I would suggest, that it is prohahle the coarso crystallization 
 of pegmatite may lie original structure and not due to suhseijuent 
 metaniorphism ; the mass of this Wicklow pegmaiite is newer than 
 the normal Leinster (iranite (Haughton's type), and c(inse(piently 
 ought to ho younger than the time of the Regional Metaniorphism ; 
 as there is no newer metamorphism recorded in its vicinity that 
 might have affected it. At the same time, the Canadian rocks are so 
 much older, it is (juite possihle that their crystallization may have 
 been augmented by metamorjihism. 
 
 Jn the Province of Ontario and the neighhouring portion of the 
 Province of Quebec, the Arch;ea:i rocks are divided up into Iluro- 
 iiians and Tjaurenlians. Sclwyn has pointed out, that these divisions, 
 although lithological, have not been jiroved to bo petrological ; while 
 as far as I can learn, Logan lias not stated that he had found any 
 proofs of their lieing petrological groups. On the other liand, how- 
 ever, Dawson (Sir J. W.). Sterry Hunt, and otliers seem to insist 
 that they <ire not only lithological, but also petrological groups. 
 
 A rock that appears to be considered a typical Ontario Laurentian 
 is a pinkish or fi-ish-coloured fine-grained gneiss. Hand-specimens 
 of this gneiss arj nndistinguishable from some of the rocks of the 
 Cambrians of the Salte' s and Forlorn. S.E. Wexford, of the Cambro- 
 Silurians, counties Wexford and Wicklow, of the Cambro-Silurians, 
 CO. Galway, of the Cambrian (?) of Erris. co. Mayo, and of the 
 Cambro-Silurians and Cambrians (?) of the co. Donegal. Some of 
 these nietamojphic rocks, as for instance those at Forlorn, were 
 evidently originally felspathic and proliahly tuffose stratified rocks ; 
 this piobably was also the case in many places where similar gneiss 
 occurs in the counties Galway, May«n and Donegal; but there are 
 also in those places, and in the co. Wicklow, similar gneisses that 
 evidently were originally intrusions of felstone or felsite. In the 
 iiigii gi'OUluI called Ciieisca MoUnlaiiis, UlLuWa C^iUiity, lliC-i'c io A 
 
Cl. II. Kindhnn — Irish tuid Canndian Uorh:, Cowpnrrd. 105 
 
 pmnitdiil giuMHs very liko fiomo of thoHe of (Jnlway, Mnyo, iiml 
 Diiticf^ul ; this is i\ nnik iiittTiiifiliate in Htructuio lu'twceti tJiosc jimt 
 incnti</MiMl ill Ontario and tht> coarse uneiMsiu granite of Cliicoiitiini,' 
 Mont i'aiin, etc., of tlie pnivinco of Quebec; these rocks apparently 
 I 11 hoinj; more or lens .similar in tlu-ir v^oiiHtitiientH, l»iit lia\iiij; heeii 
 Huhjccte.l to (litVcrciit dej^recs or pcrio<l« of iiietaniorpliisni. 
 
 Here in connection with the Chelsea district may ho mentioned 
 the schistose rocks between the highland and Chelsea sottlenient ; as 
 with them there are calcareous ami allieil rocks exactly similar to 
 rocks in the '-Ophiolite and Dolomite series "' of the I'welve I'ins or 
 lien.iabeola district, co. (Jalway." These Irish rocks have been snp;- 
 j^ested by William Kin^, (ialway. to be of Cambrian a^e, while my 
 examination of the district seems to <^o to contirm this oiiinion.-' 
 
 J'lofore proceeding further, it a](pears necessary to mention .somo 
 Ti*>ciiliar Irish calcareous rocks. These are found at the base of tho 
 Lower Carboniferous Sandstone. Co. Clare, at or near tho base of 
 the Devono-Silnrian rocks of Mayo ami Calway. and at diflbrent 
 horizons' in the Cambro-Silnrians and Caiidirians of Donegal, 
 Sligo, Mayo, Galway, Waterford, We.vford, and Wicklow. 'I'hese 
 calcareous rocks aie more or less intimately connected with basic 
 eruptive rocks and to me appear to lie adjuncts of vulcanicity.' 
 In the township of l^uckingham and elsewhere in Ottawa county 
 there are ajiatites ([ihosphate of lime), that make very like the 
 above-mentioned Irish Cambro-Silurian and (^ambrian (i) limestones 
 as they are associated anil more or less intimately connected or 
 entangled with the basic eruptive rocks. In connection with these, 
 it may jierhaps be allowable to suggest, tliat originally they possibly 
 were carbonates ; but that in .some way. not yet explained, but at 
 the same time being an adjunct of metamorphism, they were 
 changed into the phosphate. 
 
 The rocks which par excellence are clarsed as Laurentians belong 
 to the lithological groups for which I liave proposed the names 
 " Gneiasic Granite or Granitoid Gnei.ss " aiid " Gneiss series " ; while 
 the Iluronian rocks i)ar excellence belong to the group called 
 " Schist series " and •' kSub-Metamorphic rocks." ^ In these general 
 classifications, however, there are exceptions ; because, as in Ottawa 
 county, there are included in the tracts at tho present time mapped 
 
 ' Some of these rocks 1 learn from Dr Genrire Dawson, durinu; last summer's 
 e.\i)lor;i*ioiis, Imvu lueu proved tj beloujj te the Laureutians and not a separate 
 group. 
 
 - (jeolopiy of Irelanil, chapter i. p. xxi. 
 
 '' Thise rocks Wire siifrffisted l)y the late Sir R. 1. Murchison to be Laiirentiiins ; 
 he however sub-^t (lueiitly cliunj^'t'd his opinion. In the hite proposed classitication of 
 the West Galway rocks, these have not been included in the so-called Arch, can 
 rocks ; tliat distinction bein;,' ijiven to the ni'ire n!etanior]ilio>ed, but youni,'er rocks 
 in the country to the southward ; — rocks that have ijeeii proved by their fossils to 
 be of Canibro-Siliiriau aye. 
 
 ■• Oeol. of Ireland, chap. xii. p. 19t. 
 
 ^ Geo!. Ireland, chap. x. p. 177. As a rule the Iluroni! ns seem to belong to the 
 " Schist series," but some of the Iluronian limestones and associated ro ks between 
 I'ort Arthur and the Hat l'ortau:e helonj; to the rock called by Indian ^^eologists 
 " Sub-Metamorphie rocks." Some of these liniestoues are very little altered. 
 
166 G. n. Kinnhan — Irish and Canadian Rods, Compared. 
 
 as Lfiirentians ' greater or less exposures of schistose rocks ; while 
 among the Huronians, gneiss occurs. Tiiis is similar to what occurs 
 in the old country ; as always in a tract helonging to the " Gneiss 
 series," and even often in the " Gneissic Granite," subordinate 
 schistose rocks appear, while in ♦he "Schist scries," and even in 
 some places in the " Sub-Metaniorphic rocks," sulwrdinate gneiss 
 occurs. From ocular demonstratior it is evident, as has been 
 already mentioned, that the Laurentians and Huronians are litlio- 
 logical groups ; but are they also petrological, that is, geological 
 groups ? This we have now to consider. 
 
 In the Province of Ontario there are numerous junctions of the 
 Laurentians and Huronians. Those that seem most known and have 
 been more generally studied occur more or less in the neighbourliood 
 of the Canadian Pacific Kail way, between Port Artlmr and Winnipeg ; 
 and of these the one to which the greatest attention has been directed 
 is the section at the rapid of the outfall of the Lake ot the Woods 
 near Rat Portage. This junction is stated by Sir J. W. Dawson and 
 others to be a "Fault boundary." Such a statement cannot be 
 ligiitly passed over, especially by an Irish geologist, when he thinks 
 of the intricate boundaries in S.E. Ireland (cos. Dublin, Wicklow, 
 and Wexford) between the Cambrians ,vnd the Cambro-Silurians, that 
 were first unravelled by Jukes ; es])ecially those in the neighbour- 
 hood of Carrick Mountains and Glenealy. co. Wicklow, and at 
 Poulshone and Bannow, co. Wexford. As. from the light supplied 
 by Jukes, I was able to satisfy myself that such intricate uncon- 
 formities may occur, I should be rash to state that somewhat similar 
 unconformabilities did not occur in Ontario; ;,et at the same time I 
 may be allowed to make suggestions, — or to say that I could not find 
 any satisfactorj' reascms for supposing that there is an unconform- 
 ability between the Huronian'5 and the Laurentians. 
 
 Here we may digress ai.d ask what are geological — that is, petro- 
 logical divisions ? Years ago I have heard American geologists state 
 that the European maps are r.ore lithological than geological; and 
 the more the subject is studied, the more reasons appear to believe 
 they are right in this opinion ; as the major nund)er of the divisions 
 on these maps partake more of lithological grouping than of being 
 natural petrological, that is, geohigical, divisions. Tliis is especially 
 the case in reference to the Kainozoic and Mesozoic rocks ; as the 
 different groups in them are merely lithological groups ; but it is 
 not BO much the case in the Palaeozoic rocks, as in the latter the 
 groups for the most part have a claim to be petrological ; but not 
 always, as the rocks between the Carboniferous and the Cambro- 
 Silurian are still in a higgledy-piggledy condition. The subdivisions, 
 however, are onlj' lithological, as is demonstrated by a comparison 
 of the rocks of Ireland with those of p]ngland ; the sub-groups that 
 occur in regular succession in the English groups being (juite mixed 
 up in the Irish ones.'^ 
 
 ' Sulwyn hasspcrially mditioiifd, that (lie pnstnt boundaries and mappinj; ol tliig 
 rounty is only provisional, and tliat luTialtir tliirt' will, probably, bu lound in it 
 tracts of rooks bclonjifinf; to the Huronians. 
 
 
G. II. Kinahan — Irish and Canadian Roch, Compared. 1G7 
 
 'J'his confusion of litlioloi^ioal and petrological f!;ronps in the 
 geolo^^y of the jneseiit time appears to ine to be a moat inijiortant 
 con.siil(M-atioii in tiie present iinpiiry, ])ecause, if such a chissification 
 is allowed, the Canadian groups have as much right to be called 
 " geological divisions " as many, so called, in England or rather in 
 Europe. 
 
 The mistakes that may occur by substituting lithology for petrology 
 I may attempt to illustrate by facts observed in Ireland. For the 
 uppermost group of the Irish Cambro-Silurian the term "Slate 
 series " has been suggested, as in general it consists of argillaceous 
 accumulations, also as in it all the principal veins of roofing 
 slates are found ; while for the lowest grouj) of the same formation 
 the term ''-BlHck Sliale series" has been proposed, the rocks in it 
 being also for the most part argillaceous, but at the same time car- 
 bonaceous and of a blackish colour. In both groups, however, in 
 places, thick masses of arenaceous rocks may, often suddenly, cut 
 out the argillaceous rocks. This is the case in the western extension 
 of the Croghan-Kinshella hills to the N.E. of Carnew, Wexford, 
 where in the " .Slate series " a considerable thickness of grit suddenly 
 appears in the slates ; while in the Erriff Valley, co. Mayo, a mass of 
 lithologically identical grits appear in the '^iUm^ Shale series." 
 Now, if the rocks in these two far-ai)art districts were subjected to 
 exactly the same degree of metamorphism, and under exactly the 
 same conditions, we should have two groups lithologically similar, 
 but petrologically or geologically very different ; also in both 
 localities the change from one group to another would be marked, as 
 in botli these places the argillaceous rocks are suddenly replaced by 
 arenaceous ; therefore, if metamorphosed, in both cases there should 
 be hard boundaries between the metamorphosed grit and meta- 
 morphosed slates. — one probably being gneiss and the other schist. 
 
 In dilierent places in Ireland there are tracts of gneissic rocks 
 more or less similar to the Canadian Laurentian, yet evidently they 
 belong to distinct geological groups. Of these, those in S.E. Wex- 
 ford, Carnsore district, are probably of Cambrian age, while those of 
 north Wexford in the Croghan-Kinshella range undoubtedly belong 
 to the Upper group ("Slate series") of the Cambro-Silurian ; while 
 those of the counties of Galway and Donegal may in part belong to 
 the Camljro-Silurian and in part to the Cambrian ;' in Erris, N.W. 
 
 this liowcviT (liK's not iippcar to \w proved. The dilferent flora and fauna were 
 developed and tlourislied under >U(h coiMhtioiis as were most t'avourahle ; and eonse- 
 (juently eacli dilferent irroup is most conspicuous, in more or less similar ^Toups of 
 strata ; and lor this n asoii such strata are said to he of one afje. This olten is 
 hard to disprove, on account of not beinjj able to trace the rocks trom one place to 
 another; hut when we are able to do so, as is the case with the farhotiiterous rocks 
 of Ireland, it is found tliat the so-called divisions are only litholoj:ical. This cau 
 also he seen in tlit> Irish I)evono-Siluri;in ; take, for instance, the Cultin section, 
 CO. Galway, where the lowest rocks contain Llandovery and Wenlock fossils, while 
 over them are strata containini^ Caradoc fo-^ils, which are succeeded by rocks iiavinj^ 
 tyi)icid Weulock and Ludlow fossils, while in the frroup ahovi' theni, accordini;- to 
 I)avidson, the jirominent and nearly only fossil is of a Llandoverv tv[(e. 
 
 ' In both thc'^e counties these jjneissose and ^''ranitic rocks are evidently, at least 
 in part, vouni;er than the associated rucks, which have been proved to be, or are 
 
 .... 1. .1 1.. t /, ... ] _, o'l • ' ' ' 
 
 4 W ~ ^^..UHUAA 
 
 
168 G. II. Kinahan — Irish and Canadian liorks, Compared. 
 
 Mayo, tliey may bo metamnrpliosed Cambrians ; in cast Mayo, Sligo, 
 and Tyrone, lliey are possibly Cambro-Sihirians or Upper Cambrians, 
 that is, the representatives of the Arenij^ rooks of Wales ; wliile in 
 the CO. Antrim, in the Eallycastle district, they are either Cambro- 
 Silnrians or Cambrians. All these litholnjrically beltT.gto one group, 
 while petroldgically they represent dilJerent groups, belonging to 
 dift'erent "•eoloj'ical acres. 
 
 It should be pointed out that, as a general ride, hard well-defined 
 boundaries are characteristic of excessively altered rocks; while 
 partly or unaltered rocks usually graduate into one another by alter- 
 nations of intermediate kinds of rocks; thus limestones in general 
 graduate into argillaceous rocks, and the latter into arenaceous 
 rocks ; while a mass of arenaceous rocks will usually at its margin 
 first alternate with argillaceous rocks, before the latter predominate. 
 
 The subject of hard boumlaries to metamorphosed rocks has been 
 discussed in Chap. x. of the Geology ot Ireland, where it is illus- 
 trated that, in general, small altered tracts in large unaltered areas 
 have well-marked boundaries ; while here I would point out that in 
 large areas of granitoid rocks, like those of Galway and Donegal, there 
 are facts which indicate that the me\amorphism which invaded the 
 rocks was long subsequent to their original accumulation ; as prior 
 to their metaniorphism they were upturned, coniorted, dis])laced by 
 faults and denuded, while subsecpiently such ruptures and breaks 
 were sealed up by the metamorphic action ; as proved by the breaks 
 in the less altered rocks being much more numerous than in the 
 granitoid rocks, while all in the latter are also found in the former. 
 
 ]\Iany of the phenomena mentioned as occurring in the Irish rocks 
 may not directly apply to the Canadian, but indirectly they do ; as 
 they go to prove that too much reliance must not be placed on 
 merely lithological characters, l^'urthermore. although there are 
 many varieties of the Canadian Archasan rocks for wliich thvre are 
 no equivalents in Ireland, yet there are also many that have. 
 Already the great similarity between the gneiss of the two countries 
 and of the calcareous rocks has been pointed out; while there is 
 even a greater similarity between the metamorjdiosed basic eruptive 
 rocks, if one set is compared with the other. It was remarkable ia 
 the section between Port Arthur and Winnipeg, also in Ottawa 
 County, and other places in the Province of Quebec, the lew rocks 
 I saw with wliich I was not previously acfpiainted. 
 
 To return to the boundaries of the Ontario Laurentians and 
 Huronians. All those I saw strongly suggested that they are more 
 lithological than petrological, as in no place does there apjjcar to be 
 a regular or well-marked unconformaliility or even an overlap of the 
 Huronians on the Laurentians ; while at each side of the boundary 
 there are striking similarities in the direction and dip of the beds in 
 both classes of rocks ; also all breaks, faults, and such like in the 
 supposed older mcks appear also to occur in the supjiosed newer 
 rocks. There not even being such marked differences in character 
 between these Laurentians and Huronians, as are common in the 
 Irish Cambro-Silurians, l)et\veen those altered into schists and those 
 altered iuto granitoid rocks. 
 
0. II. lunahan — Iri-sh aiid Canadinn liorks, Compared. IfiO 
 
 If we coinpaie small tliiiif^s with f;roat, a parallel niiiy be drawn 
 lietwten tlie section of metamorphosed Cambrian rocks at Forlorn 
 roint. CO. Wexford, and the section at the Kapids out of the Lake of 
 the Wood, one being a pocket edition of the other. In the Forlorn 
 Point section going southward, we first meet schists, then a h.'ud 
 boundary, then gneiss, and tlie latter after a time graduates by alter- 
 nations into schists. In the Canadian section going northward, first 
 <J^ you »>eet schists, then a hard boundary^J^iuth of which is gneiss ; and 
 / the latter still further north having in it alternations or subordinate 
 
 beds of schists : while there is also a bay that seemed to have been 
 denuded into softer strata tlian the gneiss ; of this, however, J coidd 
 not satisfy myself, as the nature of the country and time did not 
 permit. 
 
 I am aware that Sterry Hunt and others have suggested that those 
 older rocks accumulated under circumstances quite different to those 
 of the accumulation of the younger rocks ; they in a great measure 
 being more chemical than sedimentary accumulations. Such a sup- 
 position, however, now that I have been able to study the Canadian 
 rocks, appears to me unnecessary, as these supposed chemical accu- 
 mulations have their characters in common with rocks of the old 
 country, — rocks whose characters can be j)roved by ocular demonstra- 
 tion to be due, not to chemical accumulations, but to metamorphic 
 action, — that took place long subsequent to their original deposition. 
 
 Some of the suggestions that I have put forward in this paper may 
 possibly have already been ventilated by American geologists. If 
 this should happen to be the case, I beg leave to assure the originator 
 of the suggestion that his claim has been ignored not purposely, but 
 on account of my being unacquainted with the paper in which it was 
 put forward. 
 
 STKI'IIKN Al'SlIN AM) SONS, IKINIIIRS, UHRIKIKI).