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LL.I)., F.R.8, REPORT ON TH« GEOLOGY OF BROME MOUNTAIN QUEBEC JOHN A. DRESSER, M.A. OTTAWA PRINTED BY S. ti. DAWSON. PRINTER TO THE KING'S MOST EXCELLENT MAJESTY » 1906 No. 90« ;ii 11 stii ! \ .£> '■ , i?hi 3 i To Dr. Robert Bkll, Acting Director, Geological Survey of Canada. Sir —I have the honour to submit the inclosod report on the jreol- ogy of Brome mounUin. Quebec, together with a map^ illu" trat/^l I liave the honour tl(>gy I'ftnmraphy Diku Kflationof Shefford and lirome mtnx. Chemical c<>iiiiK«itif>n of the magma. . Kcdnipinic geoloiry . . The Mtinteregian serien 7 U IS 16 17 18 1 I fUT- t< ^ THH GEOLOGY OF BROME MOUNTAIN, QUE. JOHN A [>HES8ER, M.A. • On the «e.ter» p.iit .if fl... piovin... of Quel»H., the ImMi. In-tween tlie A|.p.ila.hirt,. hilN an.l th ^ F-ttur-'iitiun hi^hlnn U i, .M.upi^l by r.«kH .,f P„!,ie..zoic age, which rfi.r.'«-nt th.- «c.l..gio,il smlo fr..m (. aml.ruin to thi' l^.wer D.-voniun, Ixjth in.lusive. Tlie hmi.lth of thU t»i.MM ill thr V icinity of Montreal is alx.ut eighty inilev ft. surtW.. in nhuHHt uniformly 1..V..1, fxrf-pt for th.. pr.'s..n<.. ..f a «Mies ..f .ight hill, which ii«. f,.,ni 700 t.. re than l.OtW feet alx.ve the plain. Six est known . f the group, and this name is likely to obtain permanent currency. The hills of this series have already received consider»',ble attention from the Geological Survey and referents may be made to reports by D. T. Sterry Hunt (■), Sir William Logan (') and R. W. Ells {«). (') Jouroftl of Geology, Vol. 11. No. .'t. April-May, 1903. («) Geol. Surv, of C»n., 1868, pp. 171-187. (') Geology ol Cm., 186,"». pp. 636-659. Geol. .Surv. of Can., lo(M, pt. .1. (») Physical Geography, Uinn & Co., Boston, 1898. pi « rj rt mi Mheffoiil iiuiuntMii, whit'h ii|ipi>tir< I in t>ii> l.'lth Atiniml Re|Mirt of tli«> lif«uni)> of the n*|M)rt wiiM |iul>li>tli«tl in tli« Amt^rican (ietilotfixt for (X-tober 1901. Tlie nmin ffHturex of the .Sh<>fl'>r(l mountHin, tli«! rfM-mhlnncc of Sht-f- foni to Hrouie and aiwi their probable (nmnexion will lie ilincuptHeil lutfr. • Hroine mountain conipriwn nn area of about thirty M<|uart' niil«>Kian hilN, linM two and a half iiiilt'N south of SheffonI, whirh t-onieit next in nize, the two mount. ain>4 being the nio«t caiiterly of the group. In form Urome is rudely cinular. The central (lortion, in the vicinity of Bnime pond, wliich iH three quart4>n« of a inilo in length and half an broad, in a nearly level boain about two by two and one half niilcH in extent, and is generally overlain by heavy beds of tlay. This in !«urr..undein 600 to 1,000 fwtalxivo the altitude of the iia»in, which in itself aliout Hfty feet aljove the level of the country surrounding th<- mountain, or five hundred feet alwvesea level. Pine .VIounUin, the highest |K)int in the Bromemass, was found by simultaneous aneroid readings at th, base and summit to be 1 ,500 feet above mean sea level. The main inlet i>f firome pmd, which drains the entire central pIOr!lMti.>ri M not .Riui in tlii' I'eiii,,, Cai U.niffinti, ..f ||„. „„,,, timi- pnivii,..-^; Kr<,inf> M.mnuin mu«t llit.'*r»iv Imvr ' -.ii t'..iMii>«iti<>n ..f th.- ii|>|>.t Cl..i/.y ^-.linH-ntH Hn. w.-ll as ..thor .-v i-U-mes, prov.- tlif i^n^Kis part to Im> intru<.iv(', an.l th.-ir p{ii..oiis r.xk of the mountain formwl a lai<-..lith, ratlicr than an aitunl volcano. The writer.. r..H^aixh.'H at Mheffor.1 Mountain hav..,|,own tliat imux, also, t.. U. lacTolithic. Th re, the stmta shows an arch.-.! jH.siti.,n, und the higheni part of the i^n.H.us jn.rti.iD of the Mountain is overlain hy acap .if mKlini.-nt.iry r.K:k, th.? Trent.m dat.'s, having an ar..u of about a <|uarter ..f a Mjuare mile which is invade«l by dik.-nfr..Mi tli.. un.lerly inj< intrunives which ait! th.-mwlves ..f two diffi-niit ages of intruHioli. Dr. Adams ha.s demonstrate.! that Mount J..hn«m (Op. . iV.) isa tru.' volcanic neck ; Mount K..yal has been sh.iwn t.. have in all prolwbility H Nimilar origin (Canmlian ei.(,H .>f icnce). In regard to M..unt Royal, Mr. J. «. Buchan 1 .ecently (Cana.lian Re.juent and the country is often heavily wooiled. 'n the .jnly contact found between the first and second in- trusions the syenite was evidently intruci.'il later than the essexit.-, fragments of which it contains and into which it scn.ls oft apophyses! This contact exposed at intervals for ab.mt a .(uarter of u mile can Iw seen in cn.ssing the eastern r" Ige of the mountain through the notch nearest West .Sheffi.rd station. Except in one small exposure on what is locally known as Colliers hill, there were no evi.lences of a transi. tion from one rock to the other. At the top of some of the highest hills, as at Iron lull for instance, the syenite becom.'^s finer in texture, in others, as on the northwest side of Collier's it bee mes porphyritic. No such variation was detected in the essexite. These facts, together with the relative positi.>ns occupied 8 o OEOLOOICAL HURVEY OF CANADA by the two nK;ks, lead to the deduction that the syenite l^as lx>en in- jected largely between the previously formed essexite and the overlying seflinnntary rock, and consequently, that the esse.xite is covered in many portions of the present surface by syenite. In further support of these views, hornstone and other se^ with y nearly e<|ual to (fit. The colour ranges from chestnut to yellowish brown. The maximum angle of extinction observt>d it >*£ 20. The principal augitic constituent is slightly dichroic. (Sections having ip or U parallel to the plane of the polarizer aregrav, or gray- ish given, while those having ^ in a similar position are tiesh-coloured. Much of the mineral, however, shows no pleochroism whatever. The angle of extinction, was found to be as high as 4.") degrees. The augite is commonly inter;,'r-own with hornblende in a very intricate manner. These zones are distinguished by .slight differences in their angles of extinction, due, apparently, to minute variations in the chemical comfMJsition in the mineral. In a few sections, small grains are seen which seem to belong to another variety of augite. Thev show a difference from the last in their polarization colours, which can hardly be accounted for by mere difference of orientation. They are, however, too small to admit of satisfactory determination and are iiuite unimportant in amount. Biotite is present in irregular areas having imperfect crystallographic outlines. Sphene is prominent, its idiomorphic outlines indicating a compara tively early crystallization. The olivine is nearly colourless, and is serpentinized along cracks of the primary mineral. It crystallized earlier than the pyroxene. Nepheline is represented by a few areas of secondary material wcupy- ing interstices amongst the other minerals. Apatite occurs in needles, and, with magnetite, was the earliest con- stituent of the rock. The order of crystallization of the minerals has been approximately as follows :— magnetite, apatite, sphene, olivine, pyroxene, hornblende, biotite, plagioclase, orthocla-se, nepheline. From the foregoing description the rock is, therefore, Ijest classe*! with the es,sexite group in the Rosenbusch classification. Chemically considered it differs from the type of that group, as the following analysis by Mr. M. F. Connor, shows, in possessing less silica and greater amounts of alumina and lime. This follows naturally from the i i* i ij, ::ii yi 10 u GEOLOGICAL SCRTKT OF CANADA preponderance of lime-soda feldspar which characterizes the rock. Its varietal determination is, therefore, a lime-feldspar rich essexite. For purposes of comparison the related rocks of ShefFord and Mount Johnson are also quoted. An analysis of the essexite from Brome is j^iven under I in the fol- lowing table— II is an analysis of essexit* from Shefford mountain,— III, of essexite from Mount Johnson and TV, of essexite from Salem, Mass., which is the type occurence of essexite, SiO^ ! 44-00 ALO, Fe, O3.. FeO. .. Mg O. . . . CaO. ... Na, O. . . K, O. . . CO , Ti O., P,0,...' SO, CI MnO.. BaO. .. H. O. .. 27 73 2 3G 3!I0 2-30 13 94 2-36 •45 1 90 20 08 •80 100 02 II III i 53- 15 1 48-86 j 17 64 1938 ' 3 10 4 29 1 4 65 4 94 ; 2 94 2 00 1 566 798 500 6 44 3 10 1 91 39 1 62 2-47 65 1-23 ■28 07 — •46 •19 13 1 10 •68 99 84 99-36 ; IV 4-94 17-44 6 84 6 51 202 7-47 5-63 2-79 20 104 2-04 99 !t2 Nordmarkite is a plutonic rock generally of uniform texture, of medium or coarse grain, and gray or reddish gray in colour. It is one of the "Trachytes" of Hunt. In the hand specimen it is seen to be highly feldspathic, the only dark mineral discernible being an occa- sional speck of biotite. In the thin section, feldspar is found to make up probably 90 per cent of the entire rock. The remaining constituents in order of rela- tive abundance are,— biotite, pyroxene, hornblende, sphene and apatite. Biotite and pyroxene, and rarely hornblende, may be ranked as essential constituents. Biotite is more than equal in amount to all the other constituents together except feldspar. Occasionally a little nepheline appears, and in other i -rts a few grains of quartz. Logan gives the specific gravity of the rock as 2.632—2.638 (Geology of Canada 1863 p. 656). The feldspar has a mottled appearance and generally resembles oi-thoclase, but on closer examination proves to have a finely laminated perthitic intergrowth in the spotted areas. These areas appear to be more numerous in proportion to the magnifying powers employed. BROUK MOUNTAIN 11 O Consequently, it seems that their number is limited only by the power of the microscope. The feldspar is therefore regarded as kryptoperthite. Logan reported its specific gravity to be 2-575, and gave the following analysis (V) of selected grains: — V ! VI Si O., AI,6. Pe,0, G5 70 20 80 84 « 52 6 43 Sf) i 6S 90 1» 4« ■44 •28 6 14 6 r>5 12 Ca O Na, O ■.';■.; K3O H, 100 79 98-89 The biotite is strongly pleochroic in shades of brown. The pyroxene is nearly or quit* colourless. The extinction angle in the principal plane rises to 45 degrees. The hornblende is green in ordinary light, and shows pleerthite i>f Brome indicates a mixture having nearly the compcmition Abj Or.j. VII. Nnrrlmarkite, Brome, analysia by M. K. Connor. VIII. liaiirvikite, Byskoven, near Laurvik, Norway. Analy«i», cited by Ro»en- buBch in " Klemente der f iexteinfilehre. " IX. Nordmarkite, Shelford, Hnalyois by SI. K. Connor. X. Laurvikite >, „ „ The noim of VII is as follows : Orthoclase 3r 14 Albite 57 11 Anorthite 2'78 Nepheline. of8 Olivine o(i2 Dioiwide 3 kj Apatite oS-J Ilnienite 1 ■ 37 Magnetite 2 ' .lii !»!» aj The place of the rix;k in the quantitative classification is as follows : Class 1, Persalane. Order 5, Canadare. Rang. 1, Nordmarkase. Subrang 4, Nordmarkose. In structure it is megascopically granitic, and therefore becomes a grano-nordmarkose. It, too, is approximately normative. The chief departure of the norm from the mode is in the alkali feldspars, which in the rock are in the form of microperthite. (Laurdalose). This rock forms a low rounded hill, chiefly in lot 25 of range 11 of Brome, and occupies an area scarcely one-third of a mile in length, and of nearly equal width. It is a porphyritic rock having a green matrix and a few phenocrysts of light gray colour. In the microscopic section the rock is seen to be porphyritic and with a felsitic base. The phenocrysts are found to be feldspar, gene- rally of the character of that mineral in the nordmarkose. Typical jilagioclase was seen. Some of the phenocrysts appeared to be pure orthoclase, but more possessed the mottled character of kryptoperthite. Areas of granular, feldspathic-looking material are also numerous and are prominent in the cryptocrystalline pwrtion of the rock. Oranular f erro-magnesian minerals are also found in some of these aggregates with small amounts of magnetite, apatite, chlorite and a few individuals of biotitf. ' f DRnNRR BRONB MOUNTAIN 13 n Modalite appears in bluish individuals having roundwl or polyRonal outlines. It is isotropic showing no plcocliroism even with a j^^psuin plate produring red of the first ortler, yields no interference figure .r convergent light and the characteristic dust-like inclusions are notice- able. The structure is that of a typical effusive nK-k. Whether it repre- sents a separate irruption through iiordnmrkosc, which entin-ly sur- rounds it, or is a sharp differentiation from it, has been iniiKJssible satisfactorily to determine. The conUct with the adjacent rock is every- where drift-covered and no dikes of it are found in tlie s.irroun 1 m M 34 1 M (tn 84 Add H, O. It is therefoi-p classed as foUown ; — CUmH DowUne. Ordp'S Noigare. R*"? 1 Laurdalaw Subranff4 Laurdalow. The structure of this rock is both macroscopically and microscopi- cally, porphyritic, the ground-mass being microcrystalline. As sodalite is one of the few distinguishable minerals in it, and is indicative of its alkaline character, it may best be designated as a sodalite-bearing felsophyro-laurdalose. DIKES. Dikes later than the principal intrusions of the mountains which contain them, are very abundant in some of the Monteregian hills, and, in others, they are almost entirely wanting. Mount Royal and Shefford a<^m to have been, subsequent to their solidification, shattered by disturbances — which gave rise to the many fissures represented by the dikes, but Mount Johnson does not appear to have similarly suf- fered. In Shefford, "le dikes are of the camptonite and bostonite varieties, the latter being the lat«r in age. Only five dikes wereobs< ' ^ in tlie Brome mountain, and two of these, at least, being nordmarkite cutting essexite, do not properly come under the category of the later dikes. Of the remainder, two belong to the camptonite class and consist of hornblende and plagioclase feldspar, a few grains of magnetite and, in one case, a little augite. One of these two is marked by a tendency towards idiomorphic structure ; the other by a distinct fluidal arrange- ment of the ciystals. One is seen to cut nordmarkite ; the other is found in essexite. The remaining dike is allied to the bostonite type. It occurs in nordmarkite, having been intruded later than the body of that rock. No evidence of its age relative to that of the camponite could V)e obtained. DHKMKK BROMK WOUNTAIN 15 n The Hcan;,ty of diken at Brome, as well as the contact of the ixne-us with the sodimenury i-ocks, points to the intru8ions of this mountain as having been of no very violent character. The geneial absence of dikes within the igneous mass of the mountain also indicates since it. intrusion, there has l)een little disturbance. RELATION OK SHEKKORD AND BROMK MOUNTAIX.S. The similarity of Brome and Hhefford mountains, both in the rcks which comp,«e them, and in their laccolithic structure, combined with their close proximity, seems to point to their being parts of one laccolith. The evidence upon the point is not, however, such as t«. be wholly con- clusive The greater part of the area between the two mountains is mantled by a heavy bed of post glacial clay, admitting of a few rocks exp..sure3 m the intervening distance. The bed of the Yamaska river which 18 the lowest depression between the mountains, was carefully examined, but no exposure of igneous i-ock was found. In a hill a quarter of a mile distant from Brome and west of the West Sheffi^rd Station of the Canadian Pacific Railway, the chief additional evidence is gained. The hill itself which is 1,200 feet Ion" and rises nearly 150 feet above the surrounding land maintains fairly uniform level on the tops and is not over five hundred feet in widtk Its sides are quite steep. The rocks are chiefly bl -k slates and a quartzose sandstone, both charactensfc of the Trenton formation in the vicinity. But these are often rusty, as though near an igneous contact, and in several places are cut by narrow dikes, less than half an inch in width, of the nordmarkite or some closely allied rocks. The hill is evidently a l^htly covered boas of igneous rock forming a spur of the mountlin. Ihe hardening of the sedimenteries by the contact with the under- lying Igneous mass has probably given it its superior resisting power to the unaltered Trenton, the removal of which hp- formed the hill. A smaller though very similar hill oo -irs a short distance west of the Sheflbrd mountain, but the most xeful examination failed to find any evidence, other than its occur, oce, that it is due to intrusive agency. On thejvhole, however, it seems probable that Brome and Shefford are merely parts of one great laccolith and that the connecting part between is only lightly covered by palaeozoic sediments. The akerose essex.teof SheflFord and the hessose of Brome are. then, merely phases ot the same mass. The nordmarkose of both form one mass, and the aurdalose of Brome, if a separate intrusion, corresponds to the laurvi- kose (pulaskite) of Shefford, which, like the former, is in parts al.o poony crystallized. i 'A i (I 'I Vr 16 n OEOLOOICAL ai'RVRY or CANADA THK CHKMIC.VL COMl'OHITION OF THE M.VUMA. The chemical mean of the three intrusianf* at >Sheffurtl is practiciilly identical witli the compuNition of the laurvikoHe, while the order of intruNion is : 1st, the most bdHiu difftTentiate, es.sexite akerose ; I'lid, the arid extreme, nordmarklte nordmnrkose ; and Hnl, the pula.skitc (laurvikotte) oi intermediate composition. A comparison of the following tables of analyses of rocks frniii Shefford mountain shows the Brome specimens to have lower ratios of silica but higher of alumina and lime. II EKWxite (akerow). IX ' Nordiiiarkite (nordmarkoiie) X r.„:uikitH (laurvikone). XIV >Ie(,n of II, IX and X. XV Brutiie mtn. .M 25 22- U 2 (13 2 6ir84 65 43 16 96 1 .55 1 53 22 1 36 5 96 636 16 02 06 04 40 82 89 !»i 19 12 1-85 1 73 65 2 24 6 98 4 91 6«! 14 •(« 14 49 12 1 10 89 .-il 17-!« 2 17 2 (i» 1 27 309 6 98 4 46 13 78 27 •14 -08 46 08 1 OO 88 47 2117 2 07 2 «6 1 44 5 !>S 8 l» 3.52 1 13 12 20 •99 99 86 100 17 99 95 lllO 01 99 89 The akerose and nordmarkose areas of Shefford Mountain are practi- cally equal in extent, and while the laurvikose is much smaller than these, its composition is virtually the mean between the akerose and nordmarkose. Therefore the calculatefl analysis XIII may be safely taken as representing the average composition of the Shefford mass, ii>» indicated by the section afforded by the present surface. A rock of the composition of the mean of Shefford would be classed as follows in the quantitative cla.ssification : — Class II DoRalane. Order 5 Gprmanare. Rang :! Andase. Subranfr 4 Andose. It stwids nearly on the line between persalane and dosalane, the ratio of the salic to the femic minerals being as 83.33 : 12.40, MHOJIK MOUNTAIlf ]f ^ The „.e*n comp.mition ..f Hn.n... Mountnin, o.tinmfHJ fn.,n tl...ar.«s or the pre«,nt sui..ice ..xp-Huren (^cl. XV). w,,,,:.! U-daHSMl tl.u.-. Order T, I -r.,,U„... Rang 3 «..r..mnurH. Mubrnng ^ . Ulknli.ttliii) (iloiHxIic). The mean componition of Shefford an.J Brme mountain., .i„,il«rlv CHtiraated, is given in col. XVI. - T).e i>o.,iti. n of such a ruck in the guantitative Classification woul.l oe as follows ;-- • CUm I u 1 Order .1. H-n* «.,.. KanK 3 . Can,«l»r... SiibrMK ■» (»IUlK,ilcic). (se. It .8 light gray rock, or sometimes fawn coloure.1, and has been u».xl for the walls of a handsome Roman Catholic Church in West 8hefi-«rd village. The nick has been quarried on the northern part <,f the mountain known locally as Gale mountain, and also at Hayes quarry near the road to Hheffington. The latter quarry about two milis froni the radway has furnished th. stone used in the construction of the Canadian Pacific Railv. ay bridge over the Yamaska river at Sheffington Some excellent types of this rock suiUble for finer work are to be seen near Iron hill, five or six miles from the railway. This rock disinte- grates rapidly on expo,sed surface.s, where the gradient is steeper than the angle of repose for the detritus. This is due to the aksence of any cementing mmeral, and gives rise to large bodies of angular feldspathic talus This Ks especially noticeable on the south side of Pine mountain, Iron hill. It forms a valuable road metal, and should be more gener- ally used m the vicinity. These ai-e the chief economic uses of Brome mountain. CerUin areas of Nordmarkose might, however, be found so free from dark mineral as to be of use for feldspar. 16— G— 2 ! V. II >|S ' i!) 'M, ii •* If -I- 18 o OBOUMIOAL MURVRV or nANAnA The name Inm hill in wiil U> have bui'n kivimi on iM« NU}>p<)Ht»Nenc«> of iron in abundance. Joint planeii in thi' nordinarkom* on Pine mountain, at in mJVfntI jwirtu of Kluffonl, and Krome mountains, arc coatiMl with a thin im-ruNtAtion of iron and havi> Hoiiictiiiii'M Imh-u iiiiHtiikcn for Holid iiiaN.><«'H of iron an larKi* »h tli<^ bliM^lcH they enolom>, DISTRIBUTION AND KXTKNT OK THK MONTKKK'JIAN HKIIUX It wa.s Hir Williitni Tjoxan'x opinion (') timt tlit- dixtrilMition of thene liillH deiieiidM on a fold of the i>alH><>/oicstrutiIle an.l M..unt Royal the MHmlh^t of the neries, except Mount John*-n, which in .,uite .'.ut of the mam line and no may depend on a Hulj.,r.linate lonKitudinal fold rhe ,on.pre«iion of the Nediment*ry mck,, it should be mentioned. t.«k place very largely l«.fore the intrusion of the Monteregian hilU. Tl,e p,H«ibility Hug«eMt«l by Dr. El^ of the Monteregian chain extendrng acroM the Appalachian axin, wan inferre*'ration timn the pliKniicryiU. Thny hIkiw no lliiw Nti'ucturc, Umiik nrrnii|;ml im in ilikbAM« and hsvinK th« intcmtirvN HIIihI with {crruKitinux inat«ri«l. There »re alio a few Nrnall KmiiiN of a liri){htly |)<>lHrizinK NiilMtance which haa not been iil«)l. Th(>y aru prolmhlj the r«r« >iocura an intruwinn of it(iic ftt>t along the railway. The ((rcati-r |iortion, whivh in hIno preNUinably the ohier, ia a citantely por- phyritic ilark j^nf-n riK'k which wpathem to a brown or bluiith-brown. ItH nioxt MtrikinK feature in the ubunilance of black hornblemlu pheno- cryHtK, fr«>4|m'ntly un inch to an inch and a half in len({th. In the thin M4<<'tion theiu* upt«iir to Im> dichruic, the svhoiiie of the alianrption beini{<) -b< A. The colour raiiKeN from deep to yellowiNli brown. The aiikIc ot' extinction in a M b > a. Olivine forms the largest individual crysteU in the «!ction Tliev Hhow characteristic high .i le an.l double n-fraction and line, of partmg. Along the latter, the mineral has altered to a yellowish gi-een serpentmou. decomposition product. In natural light a section .s made quite dark by the presence of a vast number of minute opaque, tnchite-like inclusions which appear unchanged in compIetclJ serpentimzed portions of the olivine and a.e pn,bably some ore of iron. Alteration to serpentine is observed to have taken place in the centre of an otherwise fresh looking crystal of olivine. In others, the change logins along the lines of parting or around the margin. A little interstitial quartz is to be seen. The .-ock is an olivine gabbro, and is essentially similar to the olivine gabbro of Mount Washington river. New Hampshire con- tained in a series of typical rocks prepai-ed by Dr. F. D Adam» of which descriptions were published by the Geological Department' of McGill University in 1896. A comparison of these .likes with what is known of the Mount Orford series on the one hand, and with the rocks of the Monteregian 22 n GKOLOOICAL 8URVKT OW CANADA chain on the other, shows them to be closely allied to the former, and quite dissimilar tu the latter. An examination of the copper bearing (') traps of the Precambrian belt, which lies between the Orford series and the Monteregian chain in in progress at the time of 'vriting. This belt, which forms the ridge of the Ap{>alachian axis, has been examined for a distance of twenty miles southwest of Bn>me, and forty miles to the northeast without finding a single occurrence of any rocks related to the Monteregian series. In similar volcanics, presumably of the same age, a typical compttmite dike was, however, found by the writer at Lennox- ville (■'), fifty miles southeast of Brome. A similar dike has been observed by the writer at Richmond (') about fifty miles east of Brome. Mr. V. F. Marsters (*) has found typical comptonite on the shore of I^ke Mempliremagog, about the same distance south of Brome, while Prof. Kemp has recoi-delogi8t 1896. )») Bull, U. S. G. a. No. 107. r