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^■inWiWP""!^ — r- 
 
SUPERFICIAL OEOLOOY OP THE CENTl AL REGION OF N. AMERICA. G03 
 
 44. On the SuPKUFicrAi. Geology of the Central 11e(}ion of North 
 America. By Georgk M. Dawson, E*i., Assoc. H.S.M., Geologist 
 II. M North- American Boundary Commission. (ReadJune 23 
 
 (Cominuiiicuk'd by Dr. Bigsby, P.R.S., F.G.S.) 
 
 [I'tATK xxxir.] 
 
 J*hi/sicnl Gmjmphj of the Iteyion. 
 
 Where tho groat region of plain and prairie which occupies the 
 whole central part of Mexico and of tho United States crosses 
 the forty-niiitli parallel of latitude, which eonstitutes the political 
 boundary between the last-named country and British North Ame- 
 rica, it is included in longitude between the t)Gth and 114th meri- 
 dians. It narrows pretty rapidly northwards, ehietiy by the 
 encroachment on it of its eastern border, but continues as a' great 
 physical feature even to the shore of the Arctic ocean, where it ap- 
 j)ears to have a breadth of between 3U() and 400 miles. North of 
 the North Saskatchewan river, however, it loses to a great extent its 
 jtrairie character, and, with tlie increasing moisture of the climate, 
 becomes thickly covered with conift^rous forest. 
 
 The eastern boundary of this interior continental plateau, north 
 of latitude forty-nine, is formed by the western slope of that old 
 crystalline nucleus of the continent, which extends north of the 
 St. L;'.vrence and the great Lakes from Labrador to the Lake of the 
 Wojds, with a general east and M'est course, and then, turning sud- 
 denly at an angle of about ()(J° to its former general direction, runs 
 with a north-north-west course to the Arctic sea. This boundary, 
 though formed, wherever it has been carefully studied, in part of 
 less-metamorphosed rocks generally attributed to the Huronian, may 
 be called the Laurentian axis (see map, 1*1. XXXII.) In this part of 
 its course it is not of the nature of a mountain-range. It probably 
 does not attain a height of over 150U to 2U00 feet, and has an average 
 breauili of about 2')0 miles. It may rather be considered a great 
 rocky plateau ; and though it forms the division between the streams 
 running directly into Hudson's Bay and those flowing westward and 
 southward, the actual line of watershed has no determinate direction 
 on it, but follows a devious curve, which in one place (to the east of 
 the region now under consideration) approaches within twenty miles 
 of Lake Superior. Neither is it always a continuous barrier ; for 
 near the no)th end of Lake Winnipeg it is broken through by tho 
 Nclsoji aiul Churchill rivers, the former of which carries across into 
 Hudson's Bay a great part of the drainage of tho plains. 
 
 To tho west the plateau is bounded by the Rocky Mountains, 
 which rise abruptly from tho elevated plain at their base, presenting 
 often to the east almost perpendicular walls of rock. They are 
 
 1^ 
 
 i 
 
 l-bi 
 
604 
 
 O. M. DAWSON ON TOE SIPKHKICIAL OKOI.OOY OF 
 
 oomposod. not of a sinjlc ujilicavrd ridpro. but of n minihor of more 
 or loss nearly jiarallcl niiiiros. which have u trrncral tlircctinn a little 
 west of north, and a hreadtli of ov(>r <»<» miles, extendiui; from the 
 niiirjriM of tlu> frreat plains to the vjille\> of the Kootanieand (!oliim- 
 bia rivers. In the vicinity of th<' forty-ninth parallel, the j;eoln::i(al 
 continuity of the country is as sharjily broken by the line of thfir 
 0!i.stern l)as»> as its ])hysi<'al characttr. and we pass suddenly from 
 tho little-altercil or disturbe<l strata of Cretaceous and 'I'ertiarv ago 
 to scaqwMl mountain-sides of pabeozoie rocks, metamorphosed' and 
 crumitled. The liigher peaks of the mountains north of the boun- 
 dary do not seem often tt) surjtans Iojmmi feet. The jdains may 
 thoroforo be considered broadly jim a trough iutervenini; between the 
 two great loniritu-linal watersheds of the northern pail of the con- 
 tinent. The lowest ]Hirtion of this trough, however, is seV(Tal hun- 
 dred f«Ht above the sea-level; and mueh of its Western j)art is actually 
 liigber than its eastern l^iurontian rim (see Section. I'l. XXXII. 
 tisr. 2). 
 
 l{esid<>s the main lonp:itudinal watersheds, there are also two verv 
 important transverse (mi«'« (s<'e map), which are not marked by any 
 praml ]ihysical features, but ajijwar to he merely cnusiHl by low <;enlle 
 rolls in the strata. Of these, one in a general way follows the political 
 Vxtundary of the forty-ninth jtarallel. it sej)aratcs the waters of the 
 K«h1, the Assineboin and Sjiskatchewan rivers (which tind their way 
 throufih NN innijH'ij I,ake to Hudson's liay) from those of the Missis- 
 itippi and Missouri and their various tributaries. Uefrinninfr in that 
 repion of swamj) and lake in Northern Minnesota whi( h feeds the 
 variously destined head- waters of the \Vinni|K'p, St. Lawrence, Mis- 
 wssippi. and H<Hi rivers, it dips southward Ix'tween the tnlaitaries 
 of the latter two streams, and pa.>ses between Like Travei'se and h'\'^- 
 Stone litike. with an altittide ot'oiily '.'7<i feet, )•' out I'oo miles south- 
 of the b<»undary-line. Thence it ])ursues a general north-westerly 
 course along the high lands formed by the scnithern extensions of 
 I'embina KHcarpment and t!ie Missouri Coteau. and. becoming iden- 
 tified with the latter, orosH<'s the boundary-line ncarthe l(»4th nu'ri- 
 dian, .*VM) miles west of Hod Hiver. Then falling south of the drift 
 ridge of the Missouri Coteau. it follows the summit of the plateau of 
 the Lignite Tertiary for about M'Xi miles to the Cypr»'>s Hills, where 
 it is oidv 4«i miles north of the line, in longitude 1 10" 'M\'. Thence 
 it trend.H southward and crosses the forty-ninth parallel for the last 
 time alMiut .'i<> mile.s east of the base of ihe Kocky Mountains. Tie 
 avenige altitude of this watershecl region east of the Ked Kiver is 
 14(M> feet. In Northern Dakota it may bo estimated at 2<HM» feet ; 
 and from this it rises till near the mountain.s it has attained an ele- 
 vation of alMiiit 4'MM» feet. 
 
 The 8t»c«nd transverKe wnterHh<>d crosses from the Itocky ifoun- 
 tains to the Luurentian region, near the fifty-fourth i)arallel ; and 
 not much is known about it. It separates the rivers which reach 
 the Arctic Seadircitly. from those of the Saskatchewan Hyst«'m. which 
 flow into HudM)n's Hay. Where crossed by the canoe-routo to 
 JJackenxie Uiver at Methay Tortage, near it« eastern extremity, '■■' 
 
 H 
 
THE CENTIUL REOIOX OF XORTIT AJfETtrCA. 
 
 6i)o 
 
 (I 
 
 \ 
 
 i 
 
 II 
 
 hpis'nt, according to Sir J. Ilinh- 
 anlsoii, ia !')(»(; feet. Near its 
 western extremity it would ap- 
 pear (according to Dr. ircctor's 
 observations) to be al)out L'KIO 
 feet. It is ])robable that tliis 
 waterslied is lower than eitlier 
 of these measurements in the 
 intervening region. 
 
 Between the two transverse 
 watersheds thus delined, the three 
 prairie sfi'pj),s or plateaus of dif- 
 ferent elevation now to be de- 
 scribed are embraced. 
 
 The whole of tlie region slopes 
 gradually eastward from the most 
 elevated plains at the base of the 
 Rocky Motmtains to the lowest, 
 at the foot of the Laurentian i)la- 
 tcau to the east. The inclination 
 becomes more abrupton approach- 
 ing the mountains, but not so 
 much as to attract special atten- 
 tion ; but along two lines whieli 
 are in a general way parallel and 
 hold a north-west and south-east 
 course across the plains, a very 
 nuirked step-like ri.u) occurs. 
 These escarpments form the east- 
 ern Ixaindaries of the two higher 
 prairie plateaus. The lowest and 
 most eastern prairie-level is that 
 which includes the valley of the 
 Red River in its southern portion, 
 and northwards embraces Lake 
 Winnipeg and associated lakes 
 and the tlat land surrounding 
 them. Its average altitude may 
 be estimated at almut ^>UU feet ; 
 its area at oo,(!00 scjuare miles, 
 of which the great system of 
 lakes in its northern part occupies 
 i;{,i)(M) miles ; its average width 
 ia over 100 miles; iis eastern 
 boundary is in pari conterminous 
 with the shore of Lake Winnipeg 
 and the Laurentian axis, in part 
 formed by the great drift pla- 
 teau south of the Lake of the 
 Woods. ltd western limit is ^"^ 
 
 !■ 
 
 *l 
 
 
 :n 
 
 ^' 
 
 ^^^ 
 
606 
 
 O. II. DA\*'SOJf ON TOK srPKRKiriAr, (JKOLOOY OF 
 
 found at tlio foot of tho lo\v«\Ht of tlw fjrciit csoarpmonts nlrcndy 
 nuMiliDiicd, which in tho virinity of tho houndary-liin' is known 
 a« IVmbina Mountain (Hjj. 1), and, thoiij'h hrokcn throujjh by tho 
 Assinohoin iiv«T. is conliimod northward in tho Uitlinj:^, Duck, and 
 Torcupiiu' Mountains. 
 
 Hisinjr to Iho summit of the second prairie-steppe, we find our- 
 selves on the niar|j:in of the '"(Jn^at Plains," jiroperly so called. 
 This plateau lias an aver.i;;e elevation of ahont h!(Mt feet, ;ind is 
 boundetl to the Mesi liy the Missouri Coteau and foot of thi- third 
 prairie-steppe. On the forty-ninth parallel it has a width of L*:iO 
 miles, (Ui the lifty-fourth of about L'<»«i miles, thoiiirh it cannot there 
 be so strictly d«'lii"ed. To the siuth the boundarii's of this reiriou 
 apjH'arto bt'conie more indelinite. ami in the southern part of jJakota 
 the three primary levels of the country, so wol.l rnaiked north of the 
 liiu'. are jirobably scarcely distiuj;uishable. The elevated re<;ion lyinj; 
 south and west of the Lake of the Woods, and forinin;; in one places 
 the eastern boundary of tlie lowest jtrairii', als<) assumes the form of 
 a jiiateau : and though haviufj; an eh'vatiun of from lOoK to ]ti(M» 
 feet only, it corresponds with the heiirht whith the second plateau 
 above described mii;ht be expect<'d to have, had it coiitiuueil thus 
 far ea.stward. It is covered to a frr«'at depth with ilrift materials, 
 and nuiy be called tlie drift jdateau of Northern Minnes(tta. 
 
 The thir 1 or hij;hest prairie-stepjx' has an altitude of alxiut 2r)00 
 feet where it is tirst mi I with ; its surface, however, is much less 
 unifonu and more weathered than that of the lower plains; and to- 
 wani the base of the mountains it risen on the boundary-line to a 
 height of -42Mit l\'et. and in the latitude ..f the North Saskatchewan 
 to about ;{itiii( f,Lt. Soulliward. as is well known. th«' ))lains alon^ 
 the baH«> of the mountains continue to increase in elevation, the level 
 of tlie ])a8se8 through the ran^e bein;; etpiully atlected. 
 
 The eastern escarpment of this hi^diest steppe (lij,'. IM crosses the 
 l)oun<lary-line about longitude l''^^ [U^'. and runs thence with a 
 general west -north-west course to the elbow of the South Saskatche- 
 wan in longitude I*'?? . Here it bc'uds abru]»tly, and, passing due 
 north, crosses tlu' North Saskatchewan liver. 
 
 Disreurunling the two escari)ments (which in reality account for 
 but a small part of tlie westward increiuse of elevation) and drawing 
 a line in the direction of the greatest general sIojh- of the prairie- 
 surliu'e. from the intersection of the eastern base of the Kocky 
 Mountains and the forty-ninth parallel to a point on the tirst prairie- 
 level near the northern end of Lake Winniiu.' we find that it crosses 
 the escarpments nearly at right angles, and b.a.s an average fall ot 
 5'.V-< feet p<r mile. \ second line starting at the same point, and 
 terminating eastward in the lowest part of the Ued-l{i\<'r valley, on 
 the forty-ninth parallel, hhiiws an inclination of 4-4S feet. 
 
 In the foregoing brief summary of th<' physical features of the 
 region, 1 have been guided not oidy by tlie facts «>btained by the 
 lioundary-Commission Surveys, but l)y the observations of previous 
 explorers, among wh<»m I>r. He( tor deserves special mention. To 
 this geologist (who accompanied (a [(t. Palliser's expedition) is due 
 
THIS CKKTRAL REGION OP WORTH AMERICA. 
 
 eo7 
 
 the Hret clear definition of the three steppes into which the interior 
 region of British North America is naturally di\'i(lo(l. 
 
 The region which has come under my own observation is for the 
 most part pretty closely confined to the forty-ninth parallel, and forms 
 a line about 900 miles in length, extending completely across the 
 interior plateau of the continent. 
 
 Ohcinl Phenomcm of the Lanrentlan Axis. 
 
 Beginning, then, with the glacial phenomena of the Laurentian 
 axis, I shall describe tlio appeuraiices presented in the noighbour- 
 liood of tlie Lake of the Woods oidy, wliere tliis axis is intersected 
 by the forty-ninth parallel ; but, from the similarity of the traces 
 of glacial action even in very distant parts of the Laurentian 
 region, this will serve in some sense as a representation of its general 
 features. 
 
 The I^ko of the Woods, as a whole, occupies a depression in the 
 south-western slope of the Laurentian region (see Map, PI. XXXII.). 
 It is over 70 miles in extreme length, and has a coast-lino of between 
 poo and 400 miles. Its northern part is comparatively deep, reacliing 
 in some places a depth of over 80 feet. Its general form has been 
 determined by that of an area of less highly altered rocks, which are 
 j)robabIy Huronian ; and the details of its outline even follow very 
 closely the changing character of the rock, spreading out over the 
 schistose and thinly cleavable varieties, and becoming narrow and 
 tortuous where compact dioritic rocks, greenstone conglomerate, 
 and gneiss prevail. Its shores are almost invariably composed of 
 solid rock with the rounded forms characteristic of ice-action, and 
 dip rapidly below the surface of the water, forming a bold coast, 
 sandy or gravelly beaches being comparatively rare. It is studded 
 with innumerable islands, few of which are laid down on the im- 
 perfect maps yet made of the region, but which vary from those 
 several miles in length to mere water-wasted rocks. The islands, 
 like the mainland, are seen, where not covered with luxuriant vegeta- 
 tion, to be composed of round-backed rocks. Only where the rocks 
 are of a specially soft or schistose character has the action of the 
 waters of the lake had sufficient effect on them to form cliffs. The 
 southeru ])art of the lake is very different : there are few islands ; 
 the water is not deep ; and the whole southern shore is formed by 
 low-lying deposits of sand and detrital matter. Where rock-surfaces 
 appear, however, they are like those of the northern part of the lake, 
 heavily glaciated. 
 
 All the harder rocks of the region still show with the utmost per- 
 fection the scratching and grooving of the glacial period ; and some 
 of the more compact granites and intrusive diorites retain a surface 
 still perfectly bright and polished. On a small scale even the hard- 
 est and most homogeneous of the rocks show a tendency in the 
 longer axis of their elevations to parallelism with the glacial mark- 
 ings. Though the general direction of the northern part of the lake 
 
 U. J. (i. H. No. 124. 2 s 
 
f'lTfW yi 
 
 vM 
 
 • ioS 
 
 ».. M. PAWflOX ON TIIK srPKnFirUI, OFOLonV OK 
 
 also follows that of the ico-notion. it ir* at tho sanu* time that of tlu* 
 hrlt of Iluroni.-iii itK'ks already incut ittiu-d. Thr course of the 
 irlaiial striu' is rxtmiicly unifonn. and. from a fjrcat nunihor of 
 obstMvatioiis ill (lit!( rent i>arts of the lake, is found to vary through a 
 t« w jxiints only, lyiiij? hctwcon north -north -cast and south-south- 
 w»'»t and north-cast and south-west. Slijjht dctlcxions, sometimes 
 nhscrved, arc frcncrally t; accahlc to deviation of the ire hy masses 
 of re>istent rock running athw.irt its course, tlie .striie always 
 t*howin>; a tendency to U-nd towards the niore level n-^ions, and 
 away from the mor»' elevated and ru;rp'il jvirts. 
 
 At a fe^^ places in the southern |»;irt ot the lake, phuiation in the 
 ordmary direction whi«h ^iv«s form to the rock masses, was observed 
 to he sujM'rinwrihed with coarser scratches nearly eawt ntul west in 
 <lirectii>n. Some of these may he due to the packinjj of the ice of 
 the lake itM« If in the sprinjr : hut instaiii-cs occur which cannot he 
 nceovinteil for in this w ly. iS>mc rixk-surlaci'son a low jtromontoi'y 
 in the soutlu'rn part of the lake atlonl inten'stinfj examph'S. The 
 most imjxutant direction and that with \\hich the fonns (.f the sur- 
 face coim-iile is here S. l;{' \V., superinijioscd on which at one plac«' 
 are mnitches S. -I.'*' W, or N. 1*) K. Near this n direction of S. 
 .*>()" W. or N, 5<» K. ot'curs. on which is su]>erin. posed striation 
 S. 1,7^ W.. a direction cl(»sely airn-cint? w"th the general one, and 
 prtdtahly indicating a brief resumption < 'le orij^inal fore*' after a 
 short interval. 
 
 Many interestinjr special eases showin;; th>* <h:',racter and etTect 
 of the i;iacial action, came under ohser\ at ion ; hut with thi>se I do not 
 wish to burden this jta]»cr. 'i'lu- nntur«> of the present outfall of the 
 lake, however, deser^es mention. There are two channels now in 
 two. nnd evidence' of nt leju«t one other now disused. They cross a 
 narrow ridtje which separates the writers of tht< lake from th«>se of 
 the ]>asin-like head of the NVinniiK-j; Ilivcr, ami are com]>riscd 
 within a distunce of about two miles. The hard ridj;c marks the 
 junction by fault of the I^nirrntian and llun»nian rocks, the line 
 nearly foUowinj; it-* crest. Thi- j^aps throUL'h which the water 
 llows do not dejM'iid on any evident p^N-uliarity of jj;eolojjical si rue- 
 ture, but probaldy owe their origin to smaller transverse faults or 
 joints, as a tissnrc tilled with a larire grcenstom' dyke was observed 
 not many miles distant with a direction parallel to theirs. The 
 gorge-like gap through which the northern stream tlows is the 
 most interesting, and was most careiuUy examined. It is o<'enj)io<l 
 by a very pictun'sque cascade, the first lenj) of the Winnipeg River. 
 It is certainly preglacial in d:ite, and has probably arisen from 
 Bubaerial weathering along some line of weakness. The glacial 
 strue cross over it oblicjuely at an angle of about Jk»'' with it« 
 direction ; nnd the ice has had wonderfully little effect on its shape, 
 having only succeeded in rounding off somewhat the exposed angles 
 of the cliflTs. Since the glat;ial jwriod the river haw done little, as 
 tho ro^-'ks retain their rounded aspects and show ice-striation almost 
 everywhere. 
 
 
w 
 
 >L'T 
 
 TllK CKNTRVr, RKtJTOX Of NOUTII AMKUrCA. 
 
 »)(IH 
 
 thrift Phttcnu of Northern Minnesota awl Eastern Manltoha. 
 
 Mwir^fr^nT^^^f f"" "f ?'^'^^'''" ^fin'^'^^ta, which Stretches south- 
 M ard from ho L«ke of the Woods, shows only drift materials, and 
 IS eonjposed of ihom to a Rroat depth (,sec Map and Section PI. 
 AAAll f»). .Its K(M.cr;d surface is remarkably uniform, and iUs 
 slopes almos imp..rccptibly sli},ht. It is, liowover, diversified nn . 
 small scale heinj? thickly strewn with .hallow hollows, which arc 
 hlled by httlc lak,.s or the almost impassable "muskegs" of the 
 rj1?ion Iherc are also low fiat-topped ridges of sand and gravel of 
 he na ure ot kam.>s <«• eskers, and in many localities traces of larger 
 lakes than those now existing, which have been drained by the gradual 
 wearing down of the beds of their outfall streams. 
 
 The drift-deposits of this region rest on the gently sloping foot of 
 the Lnurentian axis, and are, wheiv I have seen them, composed to a 
 depth of <;(» feet or more of fine sands and arenaceous clays, with 
 ooea.sional beds of gravel and small boid<lors. The finer deposits are 
 pcnorally very evidently false-bedd.>d, and sometimes (juite hard. 
 'I'he gravelly layers, as a rule, are found n'sting on the finer material 
 U'tween it and its surface-soil, and sometimes lie on the demided 
 edges of the curved sand-lxds l)e]o\v. In one place only did I find 
 any trace of organic remains. On llie Roseau River, about oO feet 
 from the top of the bank, a piece of wood protruded from a clitt' of 
 hard sandy clay, and, on microscopic examination, appeiinxl to be a 
 fragment of the cimimon eedar (TJmjn orddcntalJ.'i). 1 have no 
 doul)t that tliese distinctly -bedded deposits of the plateau repose 
 throughout on boulder-day. I have observed them to do so in the 
 southern part of the Lake of the Woods; and, on the Roseau lliver, 
 also, indications of the underlying boulder-clay are found. In general, 
 I'owever, the few sections which exist do not penetrate suiilcieutly 
 di'cp to show this deposit. 
 
 An interesting confirmation of the general direction already stated 
 for the glacial action, is found in the composition of the materials of 
 tliis ])lateau. Its eastern side, fronting on Lake Superior, is ver^- 
 :ibnii)t, and seems to be held up bj- a ridge of hard old rocks, which 
 here and there appears from b»Mieath it. Ascending to the plateau- 
 level from the extivme western point of Lake Superior by the 
 >'i.»rthern Pacitic Railway, the drift is seen to have a reddish-purple 
 colour, which continues, though gradually l)ecomingless marked, for 
 some distance alter attaining the Munimit. The coh)ur then changes 
 to the pale yellowish giey which is generally characteristic of the 
 drift of this plateau. The red drift is derived from the red rocks 
 of the border of the lake, and is found along its whole southern side. 
 It is here bounded by a line lying a short distance back from the 
 north-western shore and nearly parallel to it. This western edge 
 of the rtxl drift has Ih'cu already noticed by Whittlesey in his paper 
 in the Smithsonian C^ontributions. The surface of the plateau is 
 very generally strewn with erratics ; and some of them are of great 
 siz»«, Thev « lO chiefly d(!rived from the Laurentian and Huronian 
 
 r<' are also many of wliiU' limestone. Dr. Bigsby 
 
 ; (*i 
 
 t' ■ 
 
 to the north; but 
 
 2s2 
 
CIO 
 
 U. U. DAWSON ON THE HUPEnPICIAL GROLOOT OF 
 
 has jfiven an Account of tho fffolop^- of tho Ijikoof the Womls and of 
 tli»' distribution and orijjin of the crriitics thtro, in formrr volumos of 
 the Journal of this Sooifty ((iuart. Jouni. (Jc(d. Soc. I Sal and lsr)2.) 
 Its shoHH* and islands iiro oovrnul with bouldrrs, mast of whicli can 
 be traccHi to out<ro|)s of similar rocks not far to tho north-oast ; but 
 here too a considfrahlo quantity of limc.dono is found. It in not 
 generally in such larpc frapnu-nts as tho nu>tamor]»hir nw'ks, and is 
 often wvn ill small pchhlcs only, but occurs in son' places in great 
 profusion. The limostone driti is entirely confined to the southern 
 and wwitcrn shon^a of the lake ; and it« ori<rin is a (juestion of some 
 difficulty. No similar rook is known to exist to the north-ea«t, 
 unless tho limestones of the shores of Hudson's Hay are of this 
 chanicter. Limestone is known to occur on the western side of the 
 I^mrcntian axis '><» miles further north-west, and beyond that iM)iut 
 in pnvit abundance. The limesloiie there found, ht)wever, is of Lower 
 Silurian and l)(>vonian age, while the fossils itj some, at least, <»f 
 the erratics prove them to bo UpjM>r Silurian. A south-eastern 
 drift (»f tloating ice nay account for some of the specimens ; but I anj 
 iiiclin(Hl to believe, with Dr. KiRsby, that an outcrop of l'p]M>r Silu- 
 rian is concealed by the drift -deposits along tho base of tho Lauren- 
 tian iu the Luke-of-the-Wools region. 
 
 t 
 
 TAjwest Prairie- Level muf Valleif of (he ]!nl Rivrr. 
 
 Descending the western side of tho drift plateau of Northern 
 Minnest)ta, we enter the valley of the Ibd Uiver (I'l. XXX I L, h) ; by 
 which term I mean to express not the wliole drainage-nn'a of the streani 
 iti a strict geographical sense, but the w<'ll-<letined and comjiarativt'ly 
 narrow trough holding the main stream, and here constituting the first 
 prairie-level, which is bounded westward by the front of the second 
 prairie-steppe. This trough runs nearly due north and soTith, and, 
 from the south shore of Lake Winnipeg to the source of the Jtcd 
 River in Lake Traverse, is .SI") miles in length. It does not end 
 here, however, but passes by a continuous gaj), never more than 
 690 feet above the sea-level, to the source of the Minnesota River, a 
 tributary of the Mississipjii. Uu the bo>indary-linc the valley is 4() 
 miles wide, and it narrows verj- gnidually southwards. The floor 
 of the valley, though it slopes upwards towards the sides, does so 
 at so small an angle as to be (juite imiwrccptible to tho eye. It 
 presents an appearance of perfect horizontality, and is perhaps tho 
 most absolutely level prairie-region of America. Ix)oking down, 
 towards evening, through one of the breaches in the edge of the 
 western escarpment, it requires little irajigination to suppose that 
 the bluish level expanse is that of the sea ; and, indeed, the whole of 
 this valley must, at a time geologically modern, have been occupie<l 
 by a great lake, the tine silty deposits of which now form its level 
 floor. On examining these deposits they are found to be arranged 
 in thin horizontal beds, which together constitute a great thickness, 
 and rest upon till or boulder-claj. Some of tho layers immediately 
 overlying the till may correspond with those already described in tho 
 
 i 
 
V 
 
 TIIK CKNTUAL KKOIO.V OF NOBTII AMERICA. 811 
 
 Bnnio roluUvo position on the drift plateau ; but I beUove thot nearly 
 the who.o thickness of the horizontal deposit belongs to the great lake 
 ot a later period. Stones of any kind are very seldom found on this 
 prairie ; they are so rare, indeed, that those which I have seen during 
 uU my excursions over it probably do not exceed twenty in number. 
 1 hey have no doubt been brought to their present position by the 
 8horc-ico of the lake itself, and are similar to those associated with 
 the drift-deposits of its bounding escarpments. 
 
 Ascending the front of the west<5m escarpment, it is found, as 
 might almost have been foresc^on, to bo terraced ; and on leaving the 
 alluvial tlat, boulders are again found abundantly, both strewing the 
 teriHces and the sunnuit of the "mountain" or second prairie- 
 Htcppc. Tiio terraces not imly occur on the front of this escarp- 
 '„'' * *^"^ t'xtend westward along the l)ank8 of tiie great valley of 
 I'enioina River, which al the time of their formation must have been 
 an inlet of the lake, and is therefore probably of prcglacial ago. 
 
 Second Prairie-Plateau. 
 
 The Hurfucoof the second plateau or steppe of the plain(Pl. XXXII., 
 <•) appears to be almost overjwliere verj- thickly covered Avith drift 
 dejiosits ; and tlie undulations and slight irregularities of its contour 
 seem in the main due to the arrangement of these surface-materials, 
 which, tliough no doubt somewhat modified by subsequent denudation, 
 do not si'om to have suffered much. Over large areas no systems of 
 '• coulees" or stream-volleys are to be found ; and the generally un- 
 dulated surface must be due to original ine(iuaUty of deposition, 
 thougli a certain quantity of material has no doubt been removed 
 from the rounded hillocks into the intervening basin-like swamps and 
 hollows. Such an arrangement not only impUes the porous .lature 
 of the subsoil, but is in accordance with the comparatively very 
 small rainfall of the region, and would tend to show that at no time 
 since its emergence has the precipitation been great. It was ob- 
 served that in many places boiddcrs and gravel are equally abundant 
 on the crests of the gentle ridges and hillocks and in the hollows, 
 while they are comparatively seldom seen on the intervening slopes. 
 A similar observation has been made by Prof. Bell in a part of the 
 second steppe considerably further north, and would tend to show 
 slight erosion of the surface by marine currents subsequent to the 
 deposition of the heavier materials. 
 
 The drift mat<<rial is found generally to consist in great part of 
 local debris derived from the immediately underlying soft formations ; 
 but this is always mixed with a considerable quantity of far-trans- 
 IK>rted material, wb'ch is generally most abundant in the upper 
 layers. Largo erratics are in some localities very plentifully strewn 
 over the jilains, but they seem to bo almost always superficial. They 
 are generally of Laurcntian rocks ; but whitish and yellowish lime- 
 stone, derived from the Silurian flanking the western base of the 
 I^urentian region, is abundant. A bank in Long-River Valley 
 shows in an interesting section, about 30 feet of drift, resting on 
 
«)12 (.. M, l»\Wf«(iN OK TIIF. Hl'l'MlKIClAI, (iEOLOUV t>K 
 
 Crrtnccous olny (»r slialc. Of \hv drift tlir lower jMtrtion In (■oni])ofi(d 
 ofstratiriod sands and gruvelp. wliioh nrv cvidtntly false- hrddod. The 
 ]M'lililes are ehietly of the undiilyin;; rock, whiclt, thoutch soon sjilit- 
 tiiiir \t\> under sul>aerial iiitiuences, has heeii hard enoujrh to bear 
 rmindin^ underwater. There are also a few sanipleH of roektt ♦rf 
 foreiijn orijrin, and the whole an'anjjed in a manner implying a very 
 Ptrtin}» llow of eurrents in diHerent directions. Ahout I 1 feet from 
 the toj) of the bank the false-be<lded layers end abruptly, beinj; eut 
 off by a we';i-niarked horizonUil plane. Above this the 1h dding [a 
 neni h<»rizontal, and the drift includes many travelled boulders of 
 Laurentian nnd white limestone, some of them larjje, togptlur with 
 nuuh small C'retacions stuff. Large boulders are also abundant, 
 I)i(itrudinp Irom tlu' surface of the prairie above. 
 
 In other places similar hard yellowish sandy clays are m<'t with, 
 but with little sign of stratification, holding many well glaciated 
 stones, and thus resembling truf till or boulder-day. I do not thijik 
 tliat the boulder-day and mori' perfectly stratified materials are here 
 es.sentially distinct ; but. ;is they Were never seen in the same section, 
 I caTinot sp<'ak iwsitivcly on this |K)iiit. In order to ;us(i'rtaiu as fur 
 as possible the origin of the foreign material of the drift and the 
 relative proportions of the different eonstittients. I adopted the follow- 
 ing metJio<l : — An average collection of polibU"* taken at random froUi 
 the gravel of any hx-ality was made, stones nl)Ove of below a certain size 
 Ix'ing rejected for convenience, and (are b« ing taken, where iM)ssibl<'. 
 to combine gatherings frniu two or three spots for each loeidity. and 
 to make the eolleetio)! a large one. The i>d)liles so obtained were 
 then carefully enumerated and divided lithologically into groups, 
 which were n terred as far sis possible to their form.-itions. From 
 the uumlKTs thus obtaiiicfl penentage ratios have been calculated. 
 The comi)arative simplicity of the geological features of the in- 
 terior of the continent, the similarity of the lithological diaractcrs 
 of tbe formations over great areas, and the al'sence of hanler 
 metamorjthic rocks in the strata of the plains are specially 
 favourable to such an investigation : and the results servo to show 
 the general courso of the drift in a region where rock-surfaces 
 eapaide of j»reserving glacial stria^ are entirely absent. It was at 
 first intended U> enumerate the })oulders and larger erratics in this 
 way, but the criterion of smaller pebbles was fouiid more frctjuently 
 applicable ; and wherever comparison wjus iMjssilde, the residt ob- 
 tained from them apiK'ared to agree closely with the proportional 
 importance of the larger masses. 1 shall jiresent here only tht^ 
 general avenigc deduced from the second prairie-steppe as a whole, 
 which is na follows : — 
 
 Laurentian 2>-4!> 
 
 llurouiaii n-Tl 
 
 limestone ">l-<tl 
 
 (iuart/ite Drift Mi 
 
 The Lisurentian material, consisting of granites and gneisses, is 
 cudily distinguitihable. Those dasaod as Huronian are chiefly hard. 
 
 V 
 
 % 
 
 i 
 
' 
 
 THK CKNTKAI, UKOION OK NOUTII AJIKUIC.V. 
 
 i 
 
 013 
 
 K'rc.uisli, opidoUo, and hornhloiidic ultoml locks. Jt is intcrestiiiK 
 to ubscrvc that tlio proj.oitioniil importance of the Laiircntian and 
 Huroman, tluw aseortainci ior the drift, is nearly that of their 
 areas where they liave been nuppod. The propoitiojiH in the drift 
 are respectively three to one. Trof. Uel!, of the Geological Snrvey, 
 has stated the pro|K)rtiou by area of Laun-ntian and Hnronian in the 
 rc-rion north-west of Lake Superior as two to one, leaving a slight 
 preponderance oltlu- fornu'r ovi>r the latter in the drift, as compared 
 with the areas in thi' inetaniorphic axis, whidi arises no donbt 
 from the greater i)roniineinf of thi; harder Laurentian rocks. The 
 liinestone is that of the thinks of the l.aiirentian axis; and its great 
 aUun(hince is an inleresling feature, and one tending to prove that 
 this r<K-k must iti prej^Iacial times have lapped far up on theLiuren- 
 tian. These three classes are derived from the north-east or east. 
 'I'he fourth or Qaarlzile «//•//'/ is a general name which [have ajjplied 
 to that coming from the Rocky Mountains, which, although not 
 entirely ctmiposed of t|uartzite, is characterized liy the great abun- 
 dance of that material, and has a peculiar and distinctive appearance. 
 This drift was met with al)undantly in many jdaces further west ; 
 but it was only in August last tliaV 1 was able to trace it to its 
 origin in the mountains. It occurs, as will Ik^ noticed, very spa- 
 ringly on this second prairie-level, and is not found over its whole 
 area. The first clearly recognizable fragments were met with near 
 thi- Inlst meridian, rnSi) mili-s from the Kocky Mountains, and over 
 200 from the nearest part of tlie Laurentian region. 
 
 On the surface of this prairie-level tliere occur some remarkable 
 elevated regions, which seem to )»e entirely com})osed of accumulated 
 drift materials (see .^ia|), I'l. X.XXll.). The most prominent of these 
 are included under ihe names of Turtle Mountain, Moose Mountain, 
 antl tlie T'ouchwoo.l Hills. Though (piite unconnected, these elevations 
 follow in a general way a conlour-lmo of the surface, and form a 
 range roughly parallel to tlie (!oteaii, to which in their appearance and 
 material they also l)ear the closest likeness. Of these elevations the 
 only one whicli I have ])ersonally examined is that known as Turtle 
 Mountain, which is bisected by the forty-ninth parallel and forms 
 the most southern of tlie series. It is u region of broken hilly 
 ground, whi(!h may be about. 1J(» miles square, and is for the most 
 part thickly wooded— a circumstance which renders it a specially 
 prominent feature when viewed across tlie prairie. Its extreme 
 lieight is not more than oOO feet above the prairie at its base ; and 
 its general elevation is a little more than 2000 feet above the sea, 
 or nearly the same as that of the surfacie of the Coteau. On ap- 
 proaching it from the east the already gently-swelling plain becomes 
 more markedly undulating, small basin-like swamps and ponds 
 are more frequent, and its junction with the region of the " !Moun- 
 tain " would be undelinable but for the limiting border of the woods. 
 Tlie western end of the mountain is more abrupt towards the ])lain, 
 and is much diversiHed with ridges, between which lie swamps and 
 lakes, which show a general tendency to arrangement in north-and^ 
 south lines. Towards the eastern end there are somowhut extcusivo 
 
6U 
 
 U. M. n.VWSON ON TIIK SUrKUKICIAI. 0KOI^)OY OK 
 
 aroiis of gently uudulatinp; land, though always characterized hy the 
 abundance of ik>o1« and swamps. Notwithstanding the apparent 
 abundance of water, there are few brooks or drainage-valleys, and 
 the streams which do o(otir are quite small. The surface seems 
 ver)' nearly that of the dritt as originally deposited, though sutticient 
 tine nijiterial has been waslu'd from the ridges to render the inter- 
 
 vening hollows tlat-bi>ttonu'd. 
 
 f, 
 
 \ 
 
 Eilije of (he Third rralne-Vlatniu. 
 
 One hundred and twenty miles west of Turtle Mountain the second 
 prairic-i>lutcau comes to an end against the foot of the great belt of 
 drift dcpt>sils known as the MisMturi ("oteau. lieyond this ]H)int 
 three diverse zones <»f country cross the forty-ninth parallel ob- 
 litpiely \s\\\\ a wcst-noitlj-wcsl coursr, in tlie order subjoined : — 
 
 1. Tuniuhuously hilly <'ountry based on a great thickness of 
 drift, and linining tlie C'oteau de MisMouii ]tr<»perly so called. 
 
 2. Flat-t»ip])etl wtihrshc(( plateau, fornu'd ot rocks of the Lignite 
 Tertiary, and c«mstiluting a part of the tirst transverse wati'ixhed 
 alread^• described. 
 
 3. lx)wer, broken-down region, south td" the ])laleau, partly based 
 on the Lignite Tertiary, and characterized by gorges and large 
 valleys draining towards the Mis.si»uri. 
 
 The second region can j)erhaps hardly be said to cross the line, 
 but apjK-ars immediately north of it. On the line and southward 
 the streams tlowing to the Mis.souri rise Jiear the southern edge of 
 the tirst division, the greater part of the jjlatcau having succumbed to 
 denuding agt'iicies. 
 
 The Missouri Coteau (fig. 2, an«l Maj) and section IM. XXXI L, z) 
 is one of the most important features <d' the western jtlains, and is 
 terlaiidy the most renuirkable monument of the (Jlacial period now 
 existing there I have had the opportunity of examining more or 
 le«8 caretuUy that portion of it which crosses the forty-ninth parallel, 
 norlh-w«'stward for a length of about ln(» miles. On the j»arallcl, 
 the breadth of the Coteau, measured at right angles to its general 
 course, is about iiU miles ; and it widens soniewliat nortliward. 
 
 On a[)proaching its base, which is always well defined at a dis- 
 tance, a gradual asciiit is made, amounting in a distance f>f li't 
 niiles to over ir>o fVct. The surface at the same time becomes 
 mori- markcnlly undulating, iw on Hearing Turtle Mountain from 
 the eu«l, till, almost l>efore i)ne is awaro of the change, the trail is 
 winding among a confusitui of abrnjttly rounded and liunultuous 
 hills. They consist entirely of drift mat<-rial; and manj- of them 
 seem to be f«»rmed idmost altogether of boulders and gravel, tho 
 finer matti-r having been to a great extent washed down into the 
 hollows and biu>»in-like valleys without outlets with which this dis- 
 trict abounds. The ridgi-s and vidleys have in general no very 
 determine*! direction; but n slight tendency to arrangement in north- 
 and-south lines was observable in kuhh" places. 
 
 The boulders and gru'.el of Ihi- Coteau aie chiefly "f Lauren tian 
 
 t 
 
 I 
 
 1 
 
I 
 
 mm 
 
 r 
 
 I 
 
 
 J I » I 
 
 THE CKNTU.VL REGION OF NORTH AMERICA. 
 
 origin, -with, however, a good doul of the \jr;|t»bf 
 U8uul white liracstonc and a slight admix- 
 ture of the quartzite drift. The whole of 
 the Cotcau-belt is characterized by the 
 absence of drainage-valleys ; and in con- 
 80(iucr.ce its pools and lakes are often 
 charged with salts, of which sulphates of 
 soda and magnesia are the most abundant. 
 1'hc saline lakes frequently dry up com- 
 pletely towards the end of the summer, 
 and present wide expanses of white efHo- 
 reseent crystals, which contrast in colour 
 with the crimson Sulicornia with whicli 
 they are often fringed. 
 
 Taking the diU'erence of level between 
 the la*it Tertiary rocks seen near the 
 eastern base of the Coteau, and those hrst 
 found on its western side, a distance of 
 about 70 miles, we find a rise of (iU<) feet. 
 The slope of the surface of the underlying 
 rocks is therefore, assuming it to be uni- 
 form, a little less than lOU feet per mile. 
 On and against this gently inclined plane 
 the immense drift deposits of the Coteau 
 hills are piled. 
 
 Tlu; average elevation of the Coteau 
 above the sea, near the forty-ninth parallel, 
 is about 2(IUU feet; and few of the hills 
 rise more than 100 feet above the general 
 level. 
 
 between the south-western side of the 
 Coteau belt and the Tertiary ])lateau is a 
 very interesting region with characters of 
 Hh own. Wide and deep valleys with sys- 
 tems of tributary coulees luive been cut in 
 tlie soft rocks of the northern loot of 
 the plateau, some of which have small 
 streams still flowing in them fed by its 
 draiiiagi' ; but for the most part they are 
 dry, or occui»ied by chains of small saline 
 lakes which dry u]) early in the summer. | ^ 
 Some large and deep saline lakes also c| 
 exist wbiih do not disappear even late in \i 
 the nutnnui. They have a winding, river- 
 like form, atul fill steep-sided valleys. These 
 great old valle} s have now no outlet ; they 
 are evidently of preglacial age, and have 
 formed a part of the former sculpture of 
 the country. The heaping of the great 
 mass of debris of tho Coteau against the 
 
 (115 
 
 to 
 
 pj (% 
 
 &; 
 
(iKi 
 
 (;, M. 1)VW«(>N ON TIIK sn'KRKIflU, «iKn|,(MiV OK 
 
 loot of the IVrtiiiry ])lat<'au lias l)I(>«k('<I tln'm uj) aiul provcnU'tl 
 tlu! walon* Hndiii;:: their way northward as Ix't'orr ; ami siiic»^ jrlucial 
 tiiiH't* the rainfall of llu' distrirt has nrvcr ht'cn surtiricntly ^rcat 
 in |iro|K)rtion to th«' rvaporation to cnaMcthc streams t«> cut thron{j;h 
 tho harrier thus formed. The existence of these t)ld valleys, and 
 the arranjjemcnt of the dnft-deposit-s with repird to them, throw 
 inii>ortant lisjlit on the fornior history of the plains. 
 
 Ner'.hward, the t'otcaii ceases tu he identified w ilh the Tertiary 
 ])lateau. and rests on a sli»]>e (»t ('retaee<tus roeks. It can he followed 
 hy ralliser's ami H'Htoi's descriptions v»f the country to IhtM-lhow 
 *<i' the S)uth SjiskatchewaTi, and tlwnce in a line nearly due north 
 tliron^h the Kajrlc antl TliickwtMul Hills; heyond the North Sas- 
 kalclu'wan, however, it appears to lu-come more l»roken and less 
 detiiiitr. In l)r. Hector's deseript ion of certain j^reat valh-ys with- 
 (>ut outlet in this northern region. 1 Jwlieve I can re(»);.;ni/e there 
 tiKi the existence of old hlockcd-up ri\cr- courses sijuilar to tho.so 
 just deserilK>d. 
 
 South of the forty-ninth jtarallel the continuation of the Kdt ot 
 drift material can also I e traced. It runs south-eastward, eharac- 
 leri/iii}; the hiirh jjround lM'twe«'n the triltularies of the Missouri 
 and the 11«'<1 Kiver. which ha.s already In-en noticed in connexion 
 with the watershed of ti\o continent ; hut wantinj^ the hackiii}^ of 
 the l,i^Jiit<'-Tertiary plati'iiu. it appears to lieroine nior»' di(liis«', and 
 ••pread more wid«'ly over tiie country, 'i'liat the drift -deposits <lo 
 not fonn the hijjfh ^r«»und of the watershed, hut are merely piled 
 n|w»n it, is evident, as Cretaceous roeks are frcipienlly seen ii. its 
 nei;rhbourho<)<l at no threat d:.'pth. From what I »an learn of tho 
 iej;i(»n it would apjM-ar that the so-e died (otean des I'rairies and 
 Coteau de Mis.s^mri. iK'tweou whieh a distimtion is nuide on the majis, 
 are jtarts of the same ;ireat feature. Their elevation is similar, and 
 nearlv the same its that of tluCoteau on the line: and thev are 
 eipially characteri/ed hy the immense profusirtn ot erratics with 
 which they are strown, and hy ha.sin-Iike swamps and lakes, 'i'he 
 ('ot4'au des Prairies, however, stretehes furthest, and dies away oidy 
 in the s<»uth- western corner of Minin-sota. 
 
 In the Coteau, then, we have a natural feature of Uie first ina;.!;ni- 
 tude — 11 mjuw of glacial tlehris and travilled hhnks with un aver- 
 ap' hre;ulth of perhaps .'it t to 4i> miles, and t-Ntendinj.'; dia;ronally 
 across the central rej^'ion of the continent for a distance of al)out 
 bUU milus. 
 
 Third or I/i'jhest Prairif- Plateau. 
 
 PiLssing the Coteau and a«eendin}» the plateau of tlie Tertiary (PI. 
 XXXII., <h, we n«»tic<' at onee a ch.an^je in the character of the drift 
 <lejH)sit«. They are muih thinner, ami, area lor ana, perhaps do not 
 <M|Uul oiH' twentieth t»f those on the Heeoiid prairie-st*'ppe. They are 
 also now largely eom|Mi!H'd uf'/z/iw/ji'/i (//vyVfrom the Kocky Mountains, 
 of the nature of shingle, and s«'ldom showing much trac«' of glaciation. 
 With this western drift, howoer, j» smaller pro|Kjrlion of that from 
 
 "• 
 
 i 
 
rHK CENTRAL KKOION 0|.' North amkuica. 817 
 
 the east ..r lujilh-t-ast is mingled. South of the wutor.hHl-],hitcuu 
 tu> third iTgion (that 8loj)iiig to the Missouri, whore it is well 
 sh.-l ercd to the north) shows the ijuartzite ,lrifl in even greater 
 purily. Whore, however, gaps or lower places iu the watershed- 
 plateau occur, incursions of Laurentian rocks and of eastern limo- 
 stoiies are also found to a greater or less extent. 
 
 The general cliaracter of the travelled drift of the third stcmiuj 
 may he setMi from its percentage composition, derived iu the same 
 way as already shown for the second steppe. 
 
 Laurentian 27'0o 
 
 Huronian ■/ 
 
 J-imestonc 15-84 
 
 Uuartzite Drift 52-10 
 
 Though llic i)erceutage of Laurentian matoi'ial appears nearly the 
 sane as lu-fore, the much smaller total (juantity of drift on this level 
 must be remembered. A mark of interrogation is put after Huro- 
 nian, to indicate that a few specimens of this formation may be pre- 
 sent, but, if so, are undistinguishahle from some varieties of the 
 QmrtzlU- di'ifl. The great decrease in limestone is at once seen ; 
 and even tlu' percentage here given includes some specimens of 
 lU.cky-Mountain limestone which has travelled eastward with the 
 Qmrtzitc ilrifl. Tlie limesttmes of Die thinks of the Laurentian 
 were jjrobably completely subnuTged ere the water reached the level 
 of the third steppe, (iuartzile and similar rocks now form over half 
 of the entire travelled portion of the drift deposit. 
 
 Some of the lower parts of this stepi)e show thick deposits of true 
 till or boulder-clay, which holds in a hard yellowish sundy matrix 
 well glaciated stones, both from the mountains and from the cast, 
 and also a great (piantity of debris from the softer imderlying beds, 
 among which are fragments of lignite from the Ti-rtiary. These 
 deposits of till, though generally massive and weathering into rudely 
 eoliimnar forms in perpendicular baidcs, often show traces of bedding 
 and arrangement in water ; and fdse-bedded sandy masses are found 
 abruptly cut off above the confused bouldery clay. The shingle de- 
 posits of the higher levels may perhaps be formed partly from the 
 rearrangement of this material ; they are at least superior to it. 
 
 'I'he width of the third steppe, on the line, is about 450 miles ; but 
 it narrows rapidly northward. Its surface is more diversified and 
 worn than that of either of the other prairie-levels ; and the occur- 
 rence and features of the drift are less constant. Following it west- 
 ward, and in the nuiiu slowly rising, Laurentian and Eastern lime- 
 stone bcjulders contiiuie to occur to within about 25 miles of the 
 base of the Rocky Mountains, at a height of about 42()0 feet. The 
 distance of these travelled blocks from the nearest part of the Lauren- 
 tian region is over 70() miles. Beyond this point eastern and north- 
 ern rocks Were not found : but that the depression of the continent 
 ceased hen- cannot be argued from this fact ; for by this time the 
 wlude of the Laurentian liighlands would be submerged. 
 On the higher prairie, sloping up towards the mountains, the 
 
018 
 
 0. M. DAWSON ON THE SVPERFTCIAL OEOLOOT OF 
 
 (Irifl is oiiliri'ly coiniutsi'd of inatoriiil tltrivod from them, mid con- 
 sists of (luartzito. with sottor nlialy und slnty rocks, and limcstoiH', 
 which is goMcrally distii;frui«habh' from that of eastern origin. No 
 jjraiiitic or pncis.sic ro«'lis occur in the vicinity of the forty-ninth 
 Itiiriillcl, or nortliwards in )lrifisli America, in the eastern ranjjes, bo 
 far as is known. Southwards, in il(»ntana, granites and gneisses are 
 found underlying all the other formatious, but they do not appear to 
 1)0 vorj' extensively ex]>o»ed. 
 
 Th<' Jiocli/ Movntiti)is. 
 
 The brook issuing eastward from the inoutli of the South Koofanie 
 Pass has cut through a gn'at thickness of clean gnivei drift, comi)oscd 
 of large and unitonn well-rounded pcl>hles, Alutve the Itrook, on 
 the tlanks oi the niounlaiiis un the south side, are s(>veral well-jire- 
 sorved terrace-levels ionii)osed of similar material. The liighest of 
 of thcM', though its Jiltitude was ntl actually meiusured, was esti- 
 mated from tlu' known altitude of the I'ass to l»e about 4-lUU feet 
 aUive the sea. From the iK)sition of these terraces, in the open 
 eastern throat of the pas8, from which the whole surface of the 
 country falls rapidly away, they can hardly be other than old sea- 
 marks. The topograjdiy of the region would not allow nu> to explain 
 them on any hyjiotht>is of a former moraine blocking up the valley. 
 
 I>r. Hector has measured similar terraces at several points .'dong 
 the Ho( ky Mi'untains north of the region now more especially iinder 
 coiisidiration. and statis that tluv may be said to range from .'ioUO 
 to i.")Oit fcft abovi" the sea. He al><» ^tat<•s that in the region ex- 
 aniimHl by him the ordinary I^iurentiai. •-rratic« were not observed 
 above Itoou ffot, Imt mintious a very rennirkablc line of boulders 
 of rod granite dejHisitt d on the ])lains at a height of ;i7<'<> feet, which, 
 knowing what \\c now do of the country, can hardly Im' 8Up}M>sed 
 to have other origin than the Laurent ian axis. It will Ik? t>bserved 
 that my nuasuri'mcMtii tally closely with Dr. Hector's for the more 
 nortliern jtart u{ the region. 
 
 Among the Itocky Mountaitis themsidvt's tmces of tlic former ac- 
 tion of glaciers are everywheii' abundant, thoiigh in the part of the 
 range near the forty-ninth jKirallel glaciers do not at present exist. 
 The endence here met with so closely resembles that found in many 
 other mountain-regions lus to render it unnecessary that it should be 
 gone over in detail. Nearly all the vaUeys hold remnants of mo- 
 rain"", some of them still very perfect. The harder rocks show the 
 usual rounded forms ; butstriation W!U< only observed in a single hx-a- 
 lity, and there coincided exactly with the main direction of the valley. 
 
 The valleys radiating from the summits of greatest elevation 
 hold long lakes, many of which appear to Ije deep, and are filled 
 with the most i)cllucid water. Whether they arc in all caaes dammed 
 in by moraine' matt<T 1 was unable to determine. These longer 
 valleys very generally t*.'rminat<i in clnjiuit, or amphitheatres, with 
 almost iK'r|Kndiculur back and sides, which overlook small but deep 
 '^rmiiial lakeLts, held in by moraine-matter and shattered rock. 
 
 t 
 
THR CENTUAt KEOION OP NORTH AMERICA. 
 
 (119 
 
 In these nhcltcTod hollovs, nnd on the shady aides of the higher 
 poiika, are jmi?.si'S of perennial snow, which have no doub^ kept 
 up the direct succession from the time when great neves tilled the 
 heads of the valleyp and the mountains aroui\d tliem were com- 
 ph»tely Huow-chil, and arc only Wfviting some change in the climatic 
 conditions, to advance again down the old valleys and occupy the 
 places they formerly filled. 
 
 t 
 
 State of the Inferior Reijion of the Continent previous to the Glacial 
 
 Period. 
 
 Having briefly stated the main ])honomcna of the Glacial period 
 in the eijntral ri'gion of North America, it may be well to rceajntu- 
 late and to give some of the conclusions to which 1 have been led by 
 their study. 
 
 iJefore the onset of glacial conditions we find tho continent stand- 
 ing at least at its present elevation, with its complete system of 
 drainage from tho larger river-valleys to many of their less impor- 
 tant tributaries already outlined. Subaerial action must before this 
 time have been in operation for a vast period, all tho great features 
 of the western plains having been already marked out, and the re- 
 moval of a truly enormous mass of the soft and neariy horizontal 
 Tertiary and (■retace(m3 rocks effected. That some very con- 
 siderablt! changes in tlie directioii of the drainage of the country 
 in preglacial and in modern times took jjlace, liowcvcr, is probable. 
 An examination of the l.ake-of-the-Woods region and a compai-ison 
 of levels render it almost certain that the waters of the area now 
 <lrained by its tributary streams then found their outlet southward 
 and westward, towards the present valley of the Red Eiver, and 
 that only after the blocking up of the southern region with the de- 
 posits of the drift did the waters flow over the preexisting breach 
 in the northern rim of the lake, nnd descend over the surface of tho 
 Laurentian to Lake Winnipeg. The Winnipeg Iliver does not show 
 any of tho characters of a true river-valley, but consists of eroded 
 and glaciated rock-hollows, from one to another of which the stream 
 falls.*^ There is also some evidence to eliow that the lied River 
 itself agreeing with the general structure of the country, flowed 
 simth'wards ; and if so, the Siiskatchewan. too, would probably with 
 it join the former representative of the Mississippi. 
 
 'This subject, however, requires a more detailed discussion than 
 can bo granted it in this place. 
 
 Mode of Glaciation and Formation of the Drift Deposits. 
 
 To the precise manner in which tho Glacial period was initiated, 
 the area now in question gives no clue ; but I have not fonnd, either 
 in the Laurentian region, or over the area of the plains, or in the 
 Rocky Mountains, any evidence necessitating tho supposition of a 
 ereat northern ice-cap or ita southward progress. 
 
 Tlv ^eat drift ridge of tho Missouri Coteau at first sight resem- 
 
02<1 
 
 c. M. i>\ws<i\ ow THK «<ri'KUKirr\r, oFor.ooY ok 
 
 !>l<'s n frijrfintic pi iritT-mnnino ; nnd, luarkiiip: its ooni-si^ in the ium]), 
 it nii;:lit l»«' ;ir,t;iifil that tlu- nearly par illfl liiir of elevations, of 
 M liieli Turtle Mountain forms one, arc remnants of a second line of 
 moraine j»ro(lure(l a.s a feel)ler «>t!ort In the retinn<; ice-slu'et. 
 
 Suth a glacier must i-illu-r have heen the southern extension of n 
 l>i.lar iee-eaj). or derivtMl from the elevated l.aurentian region to the 
 east and north ; hut 1 think, in view of the jiliysieal featnroH of the 
 country, neither of tins,' theuries can he sustained. 
 
 To reach tlu' country in the vicinity of the forty-ninth parallel a 
 northern ice-slu-rt would liave to move up the long slojie fr..in the 
 Arctic Ocean and enws the second transverse uatershetl, then, aflei- 
 descending to the level of the Saskatchewan v.iHey, again to ascend 
 the slope (amounting, as has hcen shown, to over 4 fe»'t \)cr mile) to 
 the Hrst tran^veiTse watershed and plateau of the Lignite Tertiary. 
 Such an ice-sheet, moving tliroughout on hroad plains of soft, uncon- 
 solidated Cretareous and Tirtiary rocks, woidil lie expcctecl '. > niaik 
 the sTirficewith hroad tint ings jtarallel lo its direction, and to ohlite- 
 rato the transverse wati'i-sheds and valleys. 
 
 If it bo supposed that a huge glacier resting on the Laureiitian 
 axis spre.-.d westward a( rosa the plains, the physical dilHcullies are 
 even more serious. The ice moving southward, after having cK'- 
 sconded intt> tlie He<l-Uiver trough. wouM l»ave had to asc«'nd the 
 ea.stein escarpment of soft Cretaceous rocks fnrming its western side, 
 which in one place rises over IMm) feet ahove it. Having gained the 
 second prairie- sti'j»iK', it wouhl have Iiad fo ]»ass westward up its 
 slojiing surface, surmount the soft edge of the third stcpp(> withi>ut 
 muih aUering its form, and finally terminate over 7""niilrs fiom its 
 source, and at a height t'xcei'diiig the jtre^eiit t'lcvation of the I/uiren- 
 tian a\is hy ovi-r I'tu'O feet. The distrihiition of the drift e<iually 
 negatives eillur of these theories, which would suppose tlie passage 
 of an immense ijlai i'-r acro-'S tlu- jdains. 
 
 In atfrilmting the glacial phenomena of the great i>lain to tlm 
 acti<m of tloatii\g ice. I find myself in accord witli Dr. Hector, who 
 lias studiiKl a great part of the hiisin of the Saskatchewan — and also, 
 so far as I can judg>' from his reports, with Dr. llaydcu. who, more 
 than anv other geologist, has had the oj)portunity of becoming 
 familiar with all parts of the Western States. 
 
 The glaciating agent of the Laurentian plateau in the Lake-of- 
 the-Woods reginn. however, cannot have been other than glacier-ice. 
 The rounding, striation, ai.d i)oli>hing of tlu- rocks there, are glacii'r- 
 work ; and icebergs tloating, with however steady n current, cannot 
 bt* Kuppos«'d to have passecl over tlu- higher region of the walei-shed 
 to the north, and then, f.tllowing the direction of the stria^ and 
 gaining ever deeper water, to liave borne down on the subjacent 
 rocks. Tlie slopo of the axis, however, is too small to account for 
 the spontaneous descent of ordinary glaciers. In a distance of about 
 ;U) miles, in the vicinity of the Lake of the Woods, tlu- fall of the 
 general surface (tf the c(mntry is only about 'A\ fe<'t to the mile. 
 The height of the watorshed-regii.n north-east of the lake has not 
 h»'en actually mcasure<l: but n*- ir Lac Scul, which closely correaponds 
 
 i 
 
\' 
 
 Tnr, rriKTUAT, rkoton op noktu vMiniicA. 
 
 021 
 
 with tho direction rcniircd hy glacialion, iipcnrdiii": fn ^fr. Solwyn's 
 iiiras\in'ni(Mit.s it cmiunf ho ever 14(»(» lect. The lK'i<,^ht of limd in 
 otluT parts of tlu' I.aun'ufian rcy:ioii i.s very uiiifornily l>c>t\veon about 
 KJOu.iiid li>(M»ft'(>t. Allowing:. thon. Hldo'fiTtas n maxiiimm for tho 
 rofiioii Tiorth-oast of the F-akc of tlu' Woods, and lakinj? into account 
 tlu' liciglit of that lake and the distance, the general slope is not 
 greater tiian ahout Mfeet ju'r mile — an estimate agreeing closely with 
 the last, which is for a smaller area and obtained in a diiferent 
 way. This slope cannot b(! considered sutK(ient to impel a glacier 
 over a rocky surface which Sir William J.ogan has well eharacter- 
 i/etl as '• niamiliated," unltvss the glacier l)e a continent one pi'essed 
 outwards maiidy l>y its own weight and mass. 
 
 Such u glacier, I c(ine(>ive, must have occujiied the Laurentian 
 highlands; and from its wall-like front were (h-tached the icebergs 
 which strewed tlis di'liris over th(< then sid»mcrge(l jilains, and gave 
 rise to the various monuments of its action now f(nni(l there. 
 
 The sea, or a body of water in (tomnnmication with it, which may 
 have been (hiring the tirst stages of the dei)ression ]>artly or almost 
 entirely fresh, crept slowly ui)ward and spread westward across the 
 plains, carrying with it icebergs from the east and north. During 
 its progress most of the features of the glacial deposits were im- 
 pressed. In the section described at I^ong River we tind evidence 
 of shallow current-depoi-itcd banks i.i" local material, afterwards, 
 Nvith deepening water, planed otf by heavy ice depositing travelled 
 l)o\dders. 
 
 The sea reaching the edge of the slope constituting the front of 
 the higlu'st prairie-level, the deposition of the Coteau began, and 
 must have kept pace with the increasing depth of the water and 
 prevented the action of heavy ice on the front of the Tertiary 
 plateau. The water m;iy also liave been too much encumbered with 
 ico to allow the formation of heavy waves. 
 
 The iscdated drift highlatuls of the second ]dateau, including the 
 Touchw«)0(l Hills, Moiise Mttuiitain and Turtle Mountain, must also at 
 this tinu' have been formed. With regard to the two former, I do not 
 kiu)W whether then; is any preglacial nucleus round which drift- 
 bearing icebergs may have gathered. There is no reason to suppose 
 that Turtle Mountain had any such predisposing cause ; but it would 
 appear that a shoal once formed, by currents or otherwise, must have 
 been peri)etuated and built up in an increasing ratio by the ground- 
 ing t»f the tloating ii e. 
 
 The Hoeky Mountains were i>robably also at this time covered 
 with des«ending glac'ers ; but thesi> would appear to have been 
 smaller than those oi the Laurentian axis, as might, indeed, be pre- 
 supposed from their jiosition and comparatively small gathering- 
 surface. The sea, when it reached their base, received from them 
 Hmaller icebergs ; and bv these and tht> shore-ice the qmrtzite-ihift 
 doi)Osits appear to have been spread. That t^'is material should have 
 travelled in an opj)osite direction to the greater mass of the drift is 
 not strange ; for while the larger «>astern and northern icebergs may 
 have moved with the diM-per currents, the smaller western ice may 
 
4 LWU" 
 
 022 
 
 O. M. DAW«0!» ON THB flrPKRPlCIAL OKOLOOT OF 
 
 have taken dirortions cnuscd by 8iirliin«-ctirrontn from the south and 
 west, or oven Imh^h impelled by the i)reviulinj; winds. Some of the 
 liiiurentian debris, an we have wen, reached alm«»«t to the mountains, 
 while wmje of the ijuaitzitf ttrift can be distinj^uiHhed far out to- 
 wardfl the Ijiurentian axis. 
 
 The occurrence of Luirentian fnijjnuMits nt a utajje in the sub- 
 si(hMiee when, makinj; e'ery aUowance l«»r subsequent depradation, 
 the Laurentian axis must have bn'n far below waU-r, wouKI ten«l 
 to show that tlie weight and masH of the ice-enp was such as to en- 
 aible it to renuiin as a f;laeier till subnierf^ence was very deep. 
 
 The emerj^'uce of tlu' land would seem to liave been more rapid ; 
 or at least I do nut find any phenomena re(|uinnjj lonf; action at 
 this |>«*riod. Tiie water in retreat must havi- rearranged to some 
 extent a part of the surface-materials. The (|uartzit»' drift of tlie 
 thinl ste]»jx» was probaltly nu)re uniforndy sj)read at this time, and 
 apart of the surface-sculpture of the drift -deposits of the second 
 plateau may have been produced. It seems certain, however, that 
 the Uo<ky .Mountains still held eomj)aratively small glaciers, aiul 
 that the Laurentian region on it.s emergence was again clad to some 
 exti'nt with ice. for at least a short time. The closing episode of the 
 (ilat'ial p<'riod in this n-gion was the formation of the great fresh- 
 water lake of the Ited-Uiver valley, (»r first prairie-level (which 
 was oidy gradually drained), and the reexcuvation of the river- 
 courses. 
 
 It must not be concealed tliat tluTe arc diftieult'cs yet unaccounted 
 for Ity the theon»' of the glaciation and de])osit <'f drift on the plains 
 by icelx-rgs ; and chief am()ng these is the absence, wherever I have 
 examined the deposits and els<>where over the West, of the renuiins 
 of marine !kIollu;ica or other forms of marine lif»'. With a subnuT- 
 gence as great as that necessitated by the facts it is impossible to 
 explain tiie exclusion of the sea ; for, besides the evidence of the 
 higher western plains and llocky Mountains, there are terraces b<»- 
 tween the Lake of the Woods and Lake Superior nearly to the 
 summit of the laurentian axis, and corresjtonding beach-marks on 
 the face of the northern part of the second prairie escarpment. 
 
 Mr.lk'lt,in an interesting paper ((iuart.Journ.tieol.Soc. Nov. 1S74), 
 deals with similar difficulties in explaining the glaciation of Siberia. 
 The northern part of Asia apjuars in many ways to reseniltle that 
 of Americii ; surrounded by mountain-chains on all sides save the 
 north, it is n sort of interior continental basin covered with " vast 
 level sheet-s of sand and loam." As in the interior regions cjf Ame- 
 rica, marine shdla are absent, or are only found along the low 
 ground of the northern coast. To account for these facts, Mr. Uelt 
 resorts to a theory first suggested by him eight years ago, by which 
 he 8upi>08«'8 the existenc*' of a polar ice-sheet capable of blocking up 
 the entire northern front of the country, and damming back its 
 waters to form an immense freshwater lake. The outfall of this lake, 
 during its highest stage, he supjwses to have been through the de- 
 pression between the southern termination of the Ourals and the 
 western end ot the Altai to the Aral and Caspian Seas. 
 
nil: ( KNTiai. iiKfJioN oi- xoinii amkhica. 
 
 6S8 
 
 I'n-f. N. II. Wiiicli.'ll, ill nil nrticlc in llic • Topular Scionoo 
 M.ntlily' lor .Inn,- l>7;{. cntill.'-l " Tiic Drill D.'posit.s of the iXcitli- 
 wcM, broiidiy aocouMtH lor llio -liicial i.hcnonu'nii on the supposi- 
 tii.ii ot ii pol.ir -iiicicr. Ilis illnsinilioiis arc cliicllv borrowed IVoni 
 .•1 ijwtnl >inily of llio rc^nun .south ol' Ihc (ircat l',iik( s of lli(> Sf. 
 l..niron,v; hut MS li,. inclnd.s the \',inry of the llrd J{iver and tlio 
 ••ntire .Xortli-we.st in his doduclions, ;i "brief note unv not be inap- 
 propriate. Th.< niosl su--.stiv.' portion of the jKijier in that in 
 \\hirh, hke Mr. lieM. lie traces tlie necessary pro(hiction of a f>reat 
 iidand hike or sea of ficsh Maler whih' the foot of .such an iee-.slieet 
 as tliat supposed -r;i(hialiy retreats towards the north, (h)wn tho 
 gentle inclined plane of the surfice of the country. In this manner 
 the Hner stratilie(l deposits of certain re^aon.s south of the (u'cat 
 Lakes are arci.iinted fur, and also those of tho great valley .south of 
 Lake Winnipeg. 
 
 Ingi'nions as this hypothesis of a great gl.icial lake undoubtedly is, 
 it.H inapplicability to the phenomena and physical features presented 
 by the region under consideration is at ouce apjiarent. Ju achiition 
 to what lias already been said. I need pi-rhaps mention but one addi- 
 tion.'il circiinistaiici- which .appears discordant with it. 
 
 I-'roni the physical geography of the region it will lie evident that 
 Ihe entire drainage of the suppos<'d ininu'iise lake must have passed 
 southward by the Ked-Hivcr vallev. There i.s here no ranges of 
 iiioiinlaiiis to be crossed : ;iiid no reason c;:n be assigned why a clia'.i- 
 iiel once formed should not jiave been eiii down through tho gentle 
 swell of the watershed and remained the iternianent. as it a])pears 
 to have been the jirimitive, exit of the drainagi^ ol'the country. 
 
 Th(> whole (piestion is a very interesting oiii' ; and it would seem 
 probable that the solution once arrived at will bo found to apply 
 equally to Northern America and Xoithern Asia. 
 
 FAi'i.AN ATfOX (W TLATE XXXTI. 
 
 Fij^. ]. Miipof |>iiil of till' interior r('L,'iiiii of Nortli Aincritw, sliowinjj thowntcr- 
 Hlicds Mild l!ii-('i' iifiiiKiry levels of llic jiliiiii?. liie general clianu'ter of 
 tlio (Irifl, and the .Missouri Cotciii. /'. The Pril't pliiteaii of Nortlicrn 
 Minncsot;!, with drift cliicllv of Morllierii iiiid iiortli-oiKslerii origin. 
 f>. Lowest jirairic-U'Vi'l and valley of llic Hed River, r. iSet'orid pniirio- 
 |>!,ileaii, drift derived eliietlv from tlic cast and norlh-rast. (/. Tliirdor 
 Iruliest |irairie-|)lateau, Irifl I'liielly coni)H)s;'d fif qimrtzite from the 
 Hockv Sloiinlaiiis. .v. r. Mi-^souri ( 'otcati. 
 2. General .section along tlic -I'.ttli parallel from llie liocky Mountains to 
 the Liurentitni axis, \ertieal scale nnich exaggerated. a,b,c,dx, 
 and t U.I in fig. I. >/. Tiirlle .Mountain. 
 
 Q. J. G. S. Xo. 124. 
 
 2t