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The following diagrams illustrate the method: L'exemplaire filmi fut reproduit grAce h la ginArositt de i'ttablissement prAteur sulvant : La bibliothAque des Archives publiques du Canada Les cartes ou les planches trop grandes pour Atre reproduites en un seul cllchA sont filmAes A partir de i'angle supArleure gauche, de gauche A droite et de haut en bas, en prenant le nombre d'Images nAcessaire. Le diagramme suivant lllustre la mAthode : 1 2 3 1 2 3 4 6 6 'mw;m:^mm.m^mf 1 ,4 ■ .JiilAiDX. THK 6IlTIMiB«0Fmt.MWill(iB By A. T. I^RUMMOND. 'tii|"tOi'ri iiifJi Bcaats 7" ! r,;v,,i'i i i.i!u.;.ri:*. W'.-' ^^ • When examining attentively the general geological fea- tures of the country sun-ounding the Groat Lakes, the care- ful student will not fail to observe that three great centres, as it wei-e, of depression existed in its bygone history. One occupies nearly the western half of Lake Superior, the floor of which hero is vwerlaid by the Cambrian and upper division of the Keweenawan rocks. Beyond these, on the north-west and south-east hides of this part of the lake there occur, in successive debcending order, the lower division of Keweenawan, the Animikie division of the Huronian, and what are supposed ',o be the Laurentian rocks. Eastwai-d of Lako Superior, it will be observed that as far onward as the Carboniferous period, there were, neai* the present lakes, two other groat centres, as it were, of depression, the one in Northern Pennsylvania, the other in Michigan. In passing southward from the Laurentian region lying between the Georgian Bay and the Upper Ottawa, the formations are mot with in a regular, almost unbroken, ascending order, from the Laurentian of Canada, through the Lower and Upper Silurian and Devonian, until the Carboniferous rocks of Northern Pennsylvania appear. The strata representing these formationf^ occur in this regu- lar succession, all within a distance from north to south of one hundred and seventy-five miles. The outcrops of several of these formations are, on the south side of Lake Ontario, more or less parallel to the length of the lake and to each other, whilst the outcrop of the Trenton and Black River limestones to the north of the lake runs in a lino dia- gonally from the east end of Lake Ontario to the Georgian Bay. That the area presently occupied by Lake Ontario was overlaid in part by Trenton limestones and Utica slates, but perhaps more by rocks of the Hudson River and Medina age, is apparent from the way in which these strata on the north-western side are again represented to the eastward and southward of the lake. Thus, the interesting questions 252 Canadian Record of Science. '0 to consider are : Do these strata presently form the floor of the lake, or have they within the lake area beer removed by some vast erosive force acting at a recent period ? In other words, is the lake the result of a synclinal depression or of erosion, or both ? Again, is the apparent parallelism in the outcrops of the formations due to successive, gradual, permanent elevations of the land from the Laurentian period onward, each elevation stretching farther south than its predecessor, or is it due to a great erosive force which exposed in succession the upturned edges of the different strata, and as a farther result produced Lake Ontario? In Michigan, again, the Carboniferous area which there at one time was the centre of depression, is even more con- spicuous in its relations to both the surrounding geological features and the adjacent lakes. Here, on every side, there is a regular series of formations whose outcrops, after making every allowance for estimations, appear each in proper geological succession within the other, and in Michigan, form, as it were, irregularly concentric areas around the Carboniferous. Again, the contours of the shores of Lakes Michigan, Huron and St. Clair, and of Lake Erie at its western end, present the same idea of arrange- ment around the Hame central area. The interesting ques- tions arising are ; Were these formations originally laid down here with this more or less concentric arrangement which in Michigan they presently possess, or have they in recent or earlier times been the subject of some denuding force, which has given them this peculiar arrangement, and which probably has also aided in the creation or enlarge- ment of the adjacent lakes ? Again, as certain of these for- mations were evidently originally more or less continuous across the area now occupied by Lakes Huron and Michi- gan, has some vast erosive force created these lakes by re- moving the strata where they occupied the lake area, or do the strata underlie the waters of these lakes as a result of a depression, or, are there here the effects of both denuda- tion and depressiou ? The central area of Michigan was, as far onward as the ' - Great Lake Basins of the St. Lawrence. 253 close of the era of the coal meaHures, generally underwater, and unless Michigan has been the subject of extreme denu- dation, those portions of the State which surround the coal measures were dry land when these measures were de- posited. Since that period the State has been entirely above water, if wo except any depression during quaternary times. Whatever the oscillations have been at diflf'erent periods, the fact remains that the State is now in consider- able sections elevated between one thou«and and two thou- sand feet above the sea, the areas between the central and northern portions of the State forming the highest levels. In the country on the immediate west side of Lake Michi- gan, the land has, with the same exception, been above water since about the j)eriod of the Niagara limestones and shales, and is now there, in many sections, also between one and two thousand feet above the sea. In the Ontario penin- sula, on the east side of Lake Huron, there is an elevation reaching on the anticlinal at the Niagara escarpment as high as seventeen hundi-ed feet. There is, however, good evidence, as will be shown farther on that at some former time there have been certain marked disturbances in the general level of the Michigan, Erie, Huron and Ontario areas, operating probably simultaneously, and that these disturbances had much to do with the more general defining of the contours of these lakes. In following the history of the Great Lakes, the physical features of the lake bottoms att'oixi some interesting chapters. The soundings undertaken by Cols. Meade, Comstock, and other engineers ot the United States War Department, and those of Capt. Baytiekl and Commander Bolton of the Cana- dian Marine Service, enable us to form some important con- clusions, especially when taken in connection with the physi- cal and geological features of the coasts of the lakes. That the lakes have to even a moderate extent a glacial origin does not appear to be borne out by the facts which these sound- ings reveal, however much icebergs and glaciers have con- tributed their quota of results to the outlines of some portions of the coasts and to the character and disposition of the material upon these coasts and upon the lake bottoms. 264 Canadian Record of Science. Let us examine each lake in tnm. Lake Supxbiob. This lake is so distinct from the other lakes in its origin, that it must be separately considered. The point of greatest depth is not in the centre, but forty miles north-east of Duluth, and about six miles off the west shore, where, in a small area, 1,026 feet is reached, or 426 feet below ocean level. The depression to this low level at this point is, as frequently occurs elsewhere, very sudden, the depths at the immediate sides being 690 and 816 feet. The line of deepest depression at this end of the lake does not lie along or near the central line of the lake, but follows somewhat irregularly the west shore from near Duluth until it reaches the entrance to Thunder Bay. Between this bay and Isle Boyale the maximum depth is 990 feet. From that part of this line of deepest depressi* i, lying south-west of Isle Boyale, the lake bottom shallows, at first somewhat gradually, but finally more rapidly to the south shore east and west of the Apostle Islands. Along the west shore of the lake the coast line is often high, being in frequent places from 90U to 1100 feet, and at Thunder Cape attaining over 1300 feet. Below the water- line, for nearly the whole distance between Thunder Bay and Duluth, there is at or within a mile of the shore a sud- den descent to depths varying from 100 feet in some locali- ties to over 600 feet in others, whilst in one instance along- side the islands, off the east side of Thunder Cape, the bottom is only reached at 780 feet. Two miles further away from this general coast line the depth becomes 500 to 1000 feet. Thus along this west coast shore, from the sum- mit of the heights overlooking the lake to the deeper points in the line of the depression, which is generally about five miles distant, there is a total descent varying from 1600 to 1900 feet, except at Thunder Cape, where it is increased to 2140 feet. These soundings suggest that between Black Bay and the westerly end of the lake there are, running I I, Great Lake Basins of the St. Latarence, 255 somewhat parallel with and close to the coast, great sub* aqueous cliffs, some probably like Thunder Cape, and of irregular outline and at different levels, and which give rise to the sudden increase in the depths of the lake hero. There is, however, the possibility that a great downthrow, or dislocation, of the upper division of the Keewenaw Series, exists here, the hinge, as it were, of the depression being towards the south shore of the lake, and the rocks gradually sloping from this hinge to the line of deepest de- pression near the western shores. These cliffs lie in a gen- eral way parallel with the axis of the western end of the lake. Is it not suggestive that here we have the eflfects which gave rise in time to certainly the westerly half of this greatest of the inland seas ? And may not the forces which resulted in these cliffs, or in this great dislocation, if such it be, have been simultaneous with some of those volcanic forces which at different periods produced the ab- rupt overflows, or great dikes, or interstrata, of the main- land in the Huronian or Keweenawan rocks, and gave direction to the heights which at its south-western end form there the rim, as it were, of Lake Superior. The Western sandstones of the south-west shore give further clue to their period of operation. Parallel with those cliffs is another sub-aqueous escarp-, mentin Keweenaw Bay, about twenty-five miles long, lying near the south-east shore and facing in the opposite direction. Here there is an abrupt descent from depths of 100 and 150 feet to depths var3nng fi'om 300 feet to 552 feet. In the large outer bay the maximum depth is only 366 feet, and the average does not probably exceed 270 feet. At the upper end of White Fish Bay the waters of Lake Superior converge, and flowing over the rocky rim of the lake here, result in the rapids of the Sault Ste. Marie, as they descend to the level of Lake Huron. The lake bottom in the bay has points of great interest. Eunning about due northward from near Pt. Iroquois, on the Michigan shore, past Parisian Island, on its western side, to opposite Pan- cake Point, on the Ontario side of the lake, a distance of 256 Canadian Record of Science. about thirty-five miles, is a marked depression in the floor of the bay of from throe to four milee in width, flanked on both sides by more or less abrupt, continuous cliflB of probably Potsdam age. From a depth varying on the top of the cliffs from 30 to 150 feet, the descent is quickly made to depths reaching a maximum of 612 feet, and aver- aging from 350 feet to 400 feet. Whilst the summits of these subaqueous cliffs form, on either side of the depression, a relatively level surface of about two to four miles in width for the whole thirty -five miles, beyond that width the lake bottom once more, but more gradually, slopes in the one case to the eastward, in the other to the westwai'd, so as to form two other depressions paiallel to that above described, but of much less depth. Beyond Pancake Point the middle depression leads to the general depths of the lake bottom outside of the bay, but with a somewhat decreased depth at the immediate outlet. In White Fish Bay the lake bottom is, like the coast near at hand on the southern side, com- posed chiefly of beds of sand, and it is clear that these de- pressions are now partially filled up with this material and with clay. These subaqueous cliffs and depresnions lie in a general direction parallel to the eastern coast 'ine of the lake, and have probably their origin in the same cause, though subse- quently more defined by inver action. The conspicuous subaqueous ridge between Michipicoten Island and the higher division of rocks of Caribou Island has apparently also the same direction. The forces which contributed to the formation of Lake Superior appear to have taken three principal directions : the first in a line from Michipicoten Island eastward and westward, parallel with the extreme northern and general line of the southern shores of the lake, and with the north- ern coast of Keweenaw Point, where profound depths almost skirt the shores ; the second, already referred to, operating in the line of the western coasts, of the subaqueous depression near these coasts, and of the axes of Isle Eoyale and Kewee- naw Point, and of the Keweenaw Bay depression ; and the ■ Great Lake Basins of thelSt. Lawrence. 257 third, in a direction parallel with the eastern coast line, the White Fish Bay subaqueous cliffs and depression, and the ap- parent ridge between Caribou Island and Michipicoten Island. Other less important foreen acted in other direc- tions in forming Thunder Bay, Black Bay, with its deeply- channelled entrance, and the eastern and deeper side of Nepigon Buy. These forces probably opei'ated at different times, each in its turn contributing to the further enlarge- ment of the lake, which originally was no doubt of modest dimensions compared with the present area. It is just probable that the operation of the second force in the order given above was more recent than that of t le first, as a very marked subaqueous anticlinical in a line wiih and forming a continuation under the lake of the Keweenaw Peninsula, crosses to the centre of the lake, somewhat ab- ruptly severing in two the deep, lake depression which runs from Michipicoten Island westward. There is a presump- tion that this anticlinal was formed subsequently to the de- pression, and, considering also the sandstones on the south-west coast, that the central part of the lake may thus be older than the south-western. Again, the Cariboo Island anticlinal apparently likewise crosses the deep, lake depres- sion, and thus the central parts of the lake may also be older than the eastern. The White Fish Bay river channel being cut through the Potsdam sandstones, will also be more recent. If we regard these earlier forces as having a common source with some of those which resulted in the eruptive rocks, forming so prominent a feature in, and so conspicu- ously interstratified with, the Huronian and Keweenawan Series, then we may date the origin of Lake Superior as far back as it may be Huronian and Keweenawan times. And this is by no means improbable. Foster and Whitney, and especially and more recently, E. D. Irving, have shown that the lake is, in both its eastern and western halves, a great synclinal trough or depression. This conclusion has been arrived at from — particularly in the western half — the gen- erally constant dip of the Keweenawan rocks towai-ds and 258 Canadian Record of Science. under the lake ; the frequent dip of the Hnronian as well ; the re-appearance of these strata on opposite side.^ in the western half of the lake; the regular oi-der of succession of Keweenewan rocks, Huronian rocks and gjeiss, granite and crystalline schists on all sides when proceeding inland from the coast, and the parallelism between the courses of the Keweenawan belts on the north and south shores, and of the coast line with these belts. At the eastern end of the lake, Cambrian rocks overlie the Keweenawan and Huronian, and now form the rim over which the lake waters flow in their course to Lake Huron. It is conceivable that the submerged channel fractured through these rocks here was, for ages, the outlet of Lake Superior into the Trenton, Hudson River, and later seas, and that even in more recent times it joined the submerged river channel in Lake Huron, coursing its way across the sandstones, limestones, and shales of the north peninsula of Michigan by a connecting valley which subsequent eleva- tion of the land has cut off. Now, all these facts appear to effectually dispel the idea that Lake Superior has a glacial origin. It is undoubtedly the oldest of the Great Lakes, and has preserved its present general contour through vast periods and for countless ages before the glacial period. That glaciers prevailed on the mountains and hills on its coasts during the ice age, polish- ing and grooving the I'ocks and dotting the united inland sea with ice and icebergs at certain seasons is probable, but they merely added to the effect of previous ages in toning down the rough edges of these mountains and hills, and scattering the loose material thus produced over the broad surface of the bottom. Great areas of this lake's bottom around the Apostle Islands, the west side of the Keweenaw Peninsula, and within and on the west side of White Fish Bay, are surfaced with sand derived undoubtedly from the wear of the sandstones of these localities, whilst the general character of the bed of the lake, especially in its most profound depths, is clay. Dr. Selwyn thinks that the geological features of the Great Lake Basins of the St. Lawrence. 259 Lake Nepigon country may bo explained by that lake now occupying the crater of an ancient volcano, and he is in- clined to take the Hame view of Lake Superior. Whatever may be said of Lake Nepigon, the features of the present floor of Lake Superior hardly boar out this ?ouclusion, although thei'e can bo no question of the exi8^ence of enor- mous volcanic forces at different points. Whilst the history of Lake Superior, during the vast iigos which have elapsed between the Cambrian period and the close of the Tertiary, is in most respects a complete blank, yet, from the latter time, its history begins once more. Apart from the facts which the superficial deposits supply, some reference to which will hereafter arise in connection with the other lakes, the fauna of the lake itself and the flora now existing around its shores afibrd some interesting chapters. On the jutting headlands of the lake, and along the shores of the bays of its northern coasts, there are both subarctic and boreal plants which appear to foim a completely iso- lated gi-oup in these localities. Their original presence, there, it is difficult to disassociate from a migration before the close of the glacial era, when, with the somewhat colder climate, and under the influence of the low equable temper- ature of the great inland sea south of the glacier-clad Lau- rentian and Huronian mountains, subarctic and boreal plants found a natural highway along the coasts. With lofty mountains to the immediate northward, such plants, as well as *perhap8 arctic species, were doubtless not un- common. As the waters receded and the climate became milder, these northern plants were driven to localities like the headlands of Lake Superior, where the low temperature and moist atmosphere were favorable to the continuance of some of them in a struggle for life, in which probably most became extinct. The inland maritime plants of Canada, which occur along the coasts of all the Great Lakes, and on saline ground in New York State, and far westward, appeal- to be the rem- nants of a larger maritime flora which margined the coast 260 Canadian Record of Science. probably befot-e the close of glacial timew, and certainly at a period when the great inland seaM were saline, or in a state of transition from saline to fresh water, which the gradual change in the elevation of the land would have brought about. Their presence so far inland seems a direct argument for the saltness of this interior sea at these times, and under any circumstances proves, in connection with the subarctic and boreal plants of Lake Superior, that the cli- mate, at the time of their migration, was not, along the shores of that lake more severe than on the coasts of the Lower St. Lawrence at the present day. These inland maritime plants are all now found there or on the (loast of Nova Scotia. In further proof of this question of climate, does not the comparatively limited flora of the summits of the White Mountains, and other considerable heights in New England and New York, comprising chiefly four or five really arctic and a fev7 subarctic and boreal plants, nearly all also found on the coasts of the Lower St. Law- rence, of the Gulf of St. Lawrence, or of the adjacent por- tions of Labrador, show that the true arctic flora had hardly, in glacial times, reached as far south as these mountains? Profs. Verrill and 8. J. Smith, in 1871, published in the American Journal of Science a list of the deep-water fauna dredged by them in Lake Superioj*. The list is interesting as shewing the existence in that lake as well as in Lake Michigan of the marine crustaceans Mysis relicta. Loven and Pontoporeia affinis, Lindst., previously detected in Lake Wetter in Sweden. Both species were discovered in the profound depths of the lake, as well as in the shallower waters. Species of Gammarus, which might possibly be marine, were also found. They are no doubt the survivors of a larger marine fauna which inhabited the St. Lawrence basin in glacial times, and would seem to afford proof of the saline character of the water of the great inland sea which occupied this basin when the subarctic, boreal and inland maritime plants migrated to the neighborhood of Lake Supe- rior. The Mysis is a denizen of the Greenland seas, and suggests strongly that when the great inland sea prevailed Cheat Lake Basins of the St. Lawrence. 261 thfl temperature of itH water wtis maintained at a low point by cold inflowing wti-eama, by ourrentH, and by icebergs. Those cruHtaceanH thus aid in identifying the conditions under which the northern and maritime plants exiwied on the inland coiists. Lake Huron. This lake presents u totally different set of circumstances from those of Lake Superior. Its floor is laid in the Arch- aean Silurian and Devonian formations whilst the Niagara escaj'pment, continued across the Ontario peninsula, gives shape to the two groat divisions into which the lake surface is separated in its northern half. In its profound depths the lake really forms three great basins — the Georgian Bay, the Central, and the Southern basins. The continuation of the great Niagara oscai-pment in an irregular, subaqueous lidge connecting Capo Hurd, the Grand Manitoulin Island, and the vai-ious islands between them, gives the Georgian Bay a distinctive character. This ridge appears to present, underwater, bold, precipitous cliffs facing the Georgian Bay, similar to the heights from Cabot's Head to Owen Sound, and with similar deep inlets, though penetrating the ridge in somewhat different diiections. Whilst the cliffs on the islands foi-m the real summit of the ridge, and its subaqueous portions lise to an average of within 30 to 40 feet of the lake surface, the depths on its immediate eastern sides often reach 250 feet. At Over- hanging Point, between Cabot's Head and Cape Hurd, the depth at half a mile from the cliff" reaches 540 feet, the deep- est point of the Georgian Bay. Through this subaqueous ridge there does not appear to be any break permitting direct access from the deeper waters of the bay to those of the central parts of the lake beyond. Further, the dip of the strata forming the ridge appeal's by the soundings to fall gradually to the westward and south-westward, just as the same strata on the Bruce Peninsula slope to the west- 262 Canadian Record of Science. ward, and those on the Manitoulin Islands in the carve which the outcrop of the Niagara limostonos there takes, slope to the southward. The Georgian Bay in this part appears to l>e subsiding, according to Bolton's survey. North-East Shingle, off Lonely Island, presently 2 to 5 feet below water, was in Bayfield's time, 3 to 4 feet above, whilst White Shingle, off Snake Island, now 1 foot below, was formerly 2 to 3 feet above. As Bayfield's survey was made in 1822, the max- imum subsidence has been afx)ut one foot in each nine years. Commander Bolton, however, has personally sug- gested to me the possibility that floating ice may have been the cause. On the eastern banks of the St. Glair Biver there are also evidences of subsidence, but these may be local. It is possible that in some sections the Niagara escarp- ment, including under this term the whole strata exposed, may result partly from a fault. The country at the foot of and approaching the escarpment is in Canada, almost in- variably either obscured by heavy superficial deposits, or covered by the waters of the lake, rendering exact observa- tion difficult. It is quite possible that could the profound depths of the lake adjoining the east and north side of the Bruce Peninsula be Htudied, such a fault or faults might be discovered. Whilst the escarpment atCabot'is Head towers 324 feet above the water, the depths close at hand in the G-eorgian Bay reach about 498 feet, giving a total of 822 feet, and along the face of the escarpment lie the deepest parts of the Georgian Bay. From this line of depression the slope is upwai-d towards the north-eastern shores of the bay, where the depths outside of the islands average about 60 feet, excepting in Parry Sound, where there is a maximum of 354 feet. Prom Cabot's Head southeastward, at every point and island, and sometimes also in the bays, Mr. Alex. Murray found a fringe of reefs close to the cliffs, all apparently com- posed of loose blocks, and probably all derived from the destruction of the olifls by rapid currents, by the action of ^ V I Great Lake Basins of the St. Lawrence. 263 waves, as well as by the forces of the atmosphere. These reefs also extend a short distance eastward of Owen Sound. Two or three miles to the eastward of these cliflfs Com- mander Bolton has found at least two abrupt elevations quite near to the surface and covered with loose rocks. Whether, however, there has been any special subsidence in the strata on the eastern side of the escarpment or not, the escarpment itself has been the subject of elevation, greatest at the edge of the cliff and gradually lessening to the westward on the Bruce Peninsula, and to the southward on the Manitoulin Island, until all of the strata are lost under the waters of Lake Huron proper. The soundings along the whole eastern coast of the lake from Cape Hurd to Goderich, and southwai-d, and off' the southern coasts of the Manitoulin Islands, show that the strata continue to slope gradually towards the central parts of the lake. Another somewhat parallel escai-pment occurs on the west side of Matchedash Bay, and along islands at the extremity of the peninsula there. This is, however, in the area of the Trenton and Black River limestones, near or at their junc- tion with the Laurentian rocks. The strata slope from Nottawasaga Bay upward to Matchedash Bay, where they present bold cliff's facing to the north-east. The depth of water adjacent to the cliff's on these islands is very consider- able, reaching a maximum of 267 feet. The central and southern deop-water basins of Lake Huron are readily distinguished. The former, which is the deeper of the two, lies in the Upper Silurian strata, and is separ- ated from the latter, which rests on the Devonian rocks, by a well defined escarpment evidently of Corniferous limestone. This escarpment, starting from the Canadian side south of Kincardine, crosses Lake Huron in a north-westerly direc- tion in, generally, a lino with the Straits of Mackinac until near Presqu'isle Point, where it approaches the shallower waters of the Michigan coast. If 180 feet in depth of water were uniformly removed from Lake Huron, it would com- pletely separate these two basins and leave the summit of this separating ridge in some cases 120 feet above water. 19 264 Canadian Record oj Science. While thus this ridge approaches in some places within 60 feet of the pi-esent level of the lake, the profound depths on the immediate north-easterly side vary from 360 to 588 feet. The deepest point in the lake is 750 feet, or 172 feet below ocean level, and is found in this central basin about thirty miles south-west of Cape Hurd. It is a sudden depression, as the depths a short distance on either side are 426 and 366 feet, and it does not occur in the general line of deepest de- pression. This line, starting from near the Canadian shore, takes a direction irregularly parallel with the Corniferous limestone escarpment to a point somewhat more than half- way across the lake, when its direction is diverted north- ward towards Grand Manitoulin Island. A branch of this line of deepest depression runs from off' Kincardine almost due north in an irregular line towards Cape Hurd. Lake Huron is thus somewhat deeper in its Canadian half, and the central basin gradually shallows to about 180 feet near the Straits of Mackinac. The southern basin comprises all that part of the lake south of the subaqueous Corniferous escarpment, and is much shallower than the central basin. The summit of the escarpment has an average breadth of about four miles, after which, on the south-western side, the slope becomes more distinctly to the south-west or west, and is somewhat gi-adual, though the greatest depth in this southern basin is reached at 330 feet in an abrupt depression at one point, at the beginning of this slope, about midway across the lake. The depth over the greater portion of this southern basin is very moderate, and about its centime is a lai'ge area, lying somewhat north-west and south-east, whore, though almost surrounded by deeper water, the depth does not ex- ceed 180 feet, and is generally less. Whilst the bottom of the central basin is chiefly clay, with gravel in places, that of the southern basin is largely sand, especially in its lower third towards the outlet at the St. Clair Eiver, and in Saginaw Bay. Saginaw Bay appears to be a subaqueous continuation of Great Lake Basins of tJie St. Lawrence. 266 the depression which crosses the State of Michigan along the Grand Valley and which, Kotninger points out, seldom presents surfaces exceeding 100 f^iet above the lake. It does not average 30 feet in depth and it is suggestive whether it is not really a very shallow synclinal ti'ough in the Carboniferous and Devonian rocks. Now, all these facts, with others, have their bearing oa the origin of Lake Huron. The abrupt, subaqueous Corni- ferous ridge diagonally crossing the lake ; the different lines of direction of the Bruce Peninsula, its subaqueous exten- sion and the Manitoulin Islands, and of their deep bays and inlets ; the abrupt cliffs, both above and under water, show- ing rather the effects of undermining by waves and currents ; the directions of the lines of deepest depression ; and the varying and often sudden depths of the lake, showing that there has not been any general filling up of the hollows and depressiono in the lake bottom, all militate against the idea that a great glacier from the north or north-east, gradually, in the course of ages, formed the depths and out- lines of Lake Huron, nor do the directions of the ice grooves suggest what were evidently the travelling lines of the forces which gave rise to the above described and other physicial features of the lake. A reasonable conclusion) quite compatible with the existence of a i'ault, and with the elevation of the Niagara escarpment and of the land to the cast of the Geoi-gian Bay, would appear to be that the de- pression fronting this escarpment is in part the result of river excavation, and that through it flowed across Ontai'io, the drainage of the countiy to the northward and north- westward, until the waters joined the preglacial river which, as Spencer and Claypole point out, occupied the bed of Lake Ontario. This — supplemented by subsequent lake action — would account for much of the disintegration of the escarpment. The course of the river through Lake Huron was then, as shown by the line of depression, first to the south of eastward for some distance, then south towards the corniferous escarpment parallel to which it flowed, until, by a diversion to the north, it reached Cape Hurd and turning 266 Canadian Record of Science. oaatward, joined this I'iver channel in a great fall over the sub- aqueous ridge now worn back to a line between Cape Hurd and Grand Manitoulin Island. Another strr m from the north joined it at this point. Tliese groat proglacial rivers would continue their flow until the elevation of the anticlinal between the Georgian Bay and Lake Ontario blocked their course, and filling the Georgian Bay with water, created a new outlet, not by the St. Clair River, but to the south- eastward of Lake Huron as hereafter referred to. Though the eastern coasts, between the Bruce Peninsula and the County of Lambton, present bold clay clift's of con- siderable height, the general dip of the strata from the Niagara escarpment which crosses Lake Ontario to the Georgian Bay, is towaixls and under the main body of Lake Huron. As already mentioned, this is also the case on the Manitoulin Islands, and south-eastward across the suba- queous escarpment to the Bruce Peninsula. Again, the strata on the Canadian side of Lake Huron proper appear on the Michigan side in the same relative positions. These facts tend to prove that the lake is in part now a synclinal trough which has been further depressed, in common with the surrounding country, at the time when the superficial deposits were formed, but which, in its rise to its present levels, has left behind the great clay cliffs now lining its eastern sides, which have been gradualy worn backwards by the action of waves and atmospheric causes. The subject will be further referred to when discussing Lakes Michigan and Ontario, for the final shaping of the contour of these three lakes was in part due to one com- mon cause. • ■ Lake Michigan. This lake rests, to a limited degree, on the Lower Carboni- ferous rocks, but chiefly on those of Upper Silurian and Devonian age. Its depth has been said to reach even 1,800 feet; ' but the soundings made under the direction of the ' Encyclop. Britann. 9th ed. vol. 21, p. 178. Great Lake Basins of the St. Lawrence. 267 engineers of the United States War Department, do not in- dicate a greater depth than 870 feet, which is 292 feet be- low ocean level. This deepest point lies in the latitude of 44° 30' and rather nearer the Michigan than the Wisconsin shore. But a relatively limited portion of the lake has a depth exceeding 600 feet, and all of this portion is located in its northern half. The most northern parts of the lake are comparatively shallow, but there is clear evidence of a broad river channel cut through the rocky bed of the lake and running along the north side of the Beaver Island group to the Straits of Mackinac. Whilst the depth of the lake waters everywhere on either side is under 100 feet, this ancient river channel registers from 100 to 302 feet, the deepest points being in the narrowest parts of the Straits. From the Lake Huron side, another river channel entering the Strait, and with depths of from 154 feet to 210 feet, almost completes a circle around the Island of Mackinac, but is presently disconnected from the Michigan river channel by a narrow ridge or anticlinal, about two miles in width — the result of more recent warpings in the strata there — running from Point St. Ignace south-eastward, and over which there are now from It to 70 feet of water. These two subaqueous river channels were, without doubt, at one time connected, and at a previous period of these lakes' history, formed the outlet for the waters of Lakes Superior and Michigan. Both of these channels are flanked by the rocks of the Onondaga, Helderburg and probably Niagara groups, and have no doubt been enlarged by water action. It is at the same time a coincidence that in Lake Michigan the channel runs almost parallel with the northern coast of the lower peninsula of Michigan west of Mackinac and of the subaqueous ridge which connects the Helderbei'g rocks hero with those of the Beaver Island group. Whilst this course is nearly due east and west, it will be noticed in this connection that the line of direction of the jutting headlands and islands immediately near them on the north shore, at ai\d east of Mackinac Straits, is almost due south-east, and must be attributed to other causes. 268 Canadian Record of Science. The two peninsulas which defend the entrance to Gieen Bay are formed of the Niagara limeHtones which here curve to the south-west, and at Burnt Bluff and neighbouring points on the west side of the northern peninsula rise into an esc^arpment facing however to the north-west and west. Whilst at the base of this escarpment the water is, as a rule, comparatively shallow, the western side of the headland of the southern peninsula and of the adjacent islands carries deep water close to the shore, showing that the escarpment, continuing there, is in part, subaqueous, and faces also the north-west and west. It is important to observe these directions. Green Bay is however relatively shallow. The 100-foot line encloses a very limited area which, on the northern side, extends in a narrow, river-like prolongation, into Little Bay de Noquette, giving color, to that extent, to the possibility which Winchell has suggested, that in pre- glacial tinids there was a connection between the Lakes Superior aud Michigan basins by this bay and the Whitefish and Chocolate Eivers. On the eastern side of the lake. Grand Travei-se Bay in its upper half is divided by a long, narrow isthmus into two bays, each about twenty miles in length, and from one to two miles in width, with a general direction somewhat west of south. Though the outer bay which rests on the black shales has an average depth of 180 feet, these two inner bays are in reality narrow but abrupt and deep depressions varying in depth, in the one case, from 300 to 448 feet, and in the other from 300 to 612 feet. The lake bottom hei-e is either clay, sand or rock. Lying almost parallel with these depressions are on the one side the long narrow lake known as Torch Light Lake, and on the other, the promontory which separates Grand Traverse Bay from the lake, and presents high bluffs on the western side. Originally these depressions were great fractures in the Devonian rocks, created by the elevation of the land here, just as the Niagara escarpment has been similarly fractured. Between the Beaver Island group and the Manitou Islands is another extensive preglacial depression, in the rocky Great Lake Basins of the St. Laivrence. 269 bed of the lake, and with deep inlets joining it from the north, north-east, north-east by east, south and south-west sides, and the whole connected towards the south-west end with the deeper parts of the lake beyond. The descent is generally so abrupt from the shallower parts of the lake on either side to the depths of this depression and its inlets as to convoy the idea of escarpments or bold clift's almost sur- rounding the depression. The Helderberg anticlinal separates it from the old subaqueous river channel. On the other hand, Little Traverse Bay — another fracture in the Michigan coast — which has 130 to 230 feet of water everywhere within half a mile of its shores, may be said to lie about due east and west. It is important to thus note the vai-ying directions of the forces which have given rise to these different depi'essions or great fractures. The southern half of Lake Michigan has a generally uni- form appearance. Its coasts are not indented with deep bays, but presei-ve an outline somewhat straight at the sides and curved at the southern end; the waters, though shal. lower towards this southern end, have on the eastern and western sidcH a gradually increasing depth towards the cen- tral plateau of the lake ; the lake tlooi-, excepting the anti- clinal or warp in the strata between Milwaukee and Grand Haven, is comparatively level and somewhat, but uot alto- gether, free from abrupt depressions ; and whilst the lake floor in the northern half of the lake is frequently rocky, it is in the southern half almost entirely overlaid with clay or sand. Tiiese deposits of sand are much more general along the whole western and southern than on the eastern coasts, indicating at the time of deposition stronger currents to- wards these sides. In fact, the southern end of the lake in its general contour and depths, and in the character of its floor, corroboj-ates the view that whilst an outlet to the Mis- sissippi valley from the united lakes existed here, it also for a considerable time was an outlet of the present lake before its waters had receded to their present limits. The section of country to the south and west of the southern end of the lake is largely prairie, that part imme- m Canadian Record of Science. I diately suiTOunding the lake being but slightly elevated above its waters. At a very recent period these waters ex- tended in shallows over the prairie country, giving it a marshy character. Parts of the land are still so low lying and wet as to be chiefly suited for grazing purposes. All of the level black-loam prairies of Northern Illinois and In- diana have at one time been of this mai'shy character, but by the annual growth and decay of the grasses, sedges and aquatic plants generally, the black loam soil has in the long lapse of time accumulated and the land has gradually ap- peared above the water. This extreme southern section of Lake Michigan has thus had its boundaries defined in their present outline within a period probably as recent as exist- ing times. Like Lake Huron the main portion of the lake is pre- glacial. The Wisconsin geologists, especially Winchell, Chamberlain and Salisbmy, have strongly insisted not only on a continental ice-sheet covering Northeastena and Central North America in the glacial times, but on a great glacier having, dui'ing what they denominate the later glacial period, occupied among others, the Lake Michigan basin, whilst a separate smaller glacier overspread Green Bay and its sur- rounding country. Chamberlain thinks that Lake Michigan, in its regular outline and great depth and breadth, is due to glacial action, though it might have been deeply channelled by running waters in pre-giacial times. Like others of these geologists, he points to the so-called moraines running through Wisconsin, Illinois, Indiana and Michigan, some distance from but irregularly unilbrm with the coast line of the lake, as proof of the existence of the glacier. Now, it seems to me that the small extent of these moraines, if their, in general more or loss, stratified appearance allows them to be called such, is ample evidence that if a glacier did occupy, for an immense period of time, the basin of the lake, its eroding power was small. If the great superficial area and depth of Lake Michigan had been excavated by the glacier, the accumulated debris forced to its edges would have been vastly greater than the moraines indicate, more especially < > Great take Basins of the St. Lawrence. 2tl when wo consider the extensive arean crossed by the glacier between the lake and the moraines, and the vast Laurentian and Iluroniun country to the northward, then more or less glacier-clad and supplying debris, apart from the accumu- lated debris of ages previous to this time. Prof. Claypole has encountered the same difficulty in discussing the so- called moraines to the south of Lake Erie. The character of the floor of the northern half of the lake also presents difficulties. The direction of the old river channels aiid of the depressions, varying from east and west to north and south, the frequent abruptness of the descent to them, the directions of the axes of the promontories and neighbouring islands, and the absence of an 3' general filling up of the hollows and depressions of the lake bottom in its northern half, all indicate that the glacier, if it existed, did not contribute to the forming of many of the leading out- lines of the coast, or to the stamping of the chief features upon the lake floor. The subject will, however, be further discussed when refemng to Lake Ontario in connection with this lake and Lake Huron. Lake Ontario. An important fact which at once strikes the observer, when noting the soundings in this lake, is that the areas of greatest depth are all towards the southern side of the lake. The deepest point is 738 feet or 506 feet below the ocean level, and is located about fifteen miles otf the New York State side, between Rochester and Oswego. The 600- foot line here encloses an area of about thirty-eight miles long and ten miles broad, lying about parallel to the coast, and within eight miles of it. To this deep depression there is a fall of about 300 feet in two and a-half miles on its im- mediate southern side. On the northern side the descent is more gradual. Another depression exceeding 600 feet, but very small in area, exists about the seventy eighth meridian of longitude, but similarily towards the United States side. Again, the 300-foot line encloses an area about mmmmmmm 272 Canadian Record of Science. 150 miles long and 24 miles broad, and in outline very like that of the present lake, but approaching the Houtborn side within three to seven miloH for the whole distance. The line of deepest depression along the length of the lake is also located al)0ut two-thirds of the way across the lake towards the New York State side. South of Port Credit and Toronto it takes the centre of the lake, but after that swerves towards the southern side. Preserving a depth of 540 to 570 feet for over sixty miles, it reaches the 600-f(K)t line area, and linall}' begins to shallow at about nine miles off Os.vego, where the depth is 576 feet. The evidence afforded by the terraces on either side of Lake Ontario would appear to show that, on the elevation of the land to its present limii, the rise was greater towards the north of the lake than to the south. This would cause the strata on the north side to dip towards the south, and. force the waters of the lake more towards the southern side. The lake bottom within the 600-foot line is chiefly mud, whilst outside, within the 300-foot line, it is largely clay and mud, with sand in occasional places. Close to the southern and eastern shores, rock is met with for the whole distance, but, with one exception, not elsewhere. The only large con- nected stretches of sand occur off and to the north-east oi' Oswego, suggesting, though not necessarily, an old outlet there. Between Stony Point, off Sackett's Harbor, and South Bay Point, on the Canadian side, there is a rise in the level of the lake floor, culminating in the Duck and Galloo Islands. Between this limiting line and the outlet of the lake at Kingston, not only is the depth shallower — not exceeding 120 feet except in what may be two river channels, on either side of Duck Island, running inwards for ten miles towards Kingston — but its bottom is in nearly all directions rocky, and the contour of its shores — unlike the rest of the lake — is irregular, with deep bays and channels, which with the islands lie in a general north-east and south-west direction. The absence of the mud or clay which overspreads the lake elsewhere, and the two river channels opening towards the Cheat Lake Basins of tJie St. Lawrence. 278 lake, suggest that this section of the lake in more recent than the main banin beyond, and that the coast at one time may have been between South Bay and Stony Point. The conformation of the chores, the lino of axis of the islands and the direction of the .strisB at Kingston and of the lime- stone escarpment and striated Laurentian hills und gorge at Kingston Mills also suggest the action of a glacier from the north«east, whilst the whole would seem to show that at that time thu lake outlet at Kingston did not exist. The absence of strit© on the surface of the limeHtones on the summit of the anticlinal at Fort Henry, near Kingston, tht)ugh present in frei^uent places at the waterline, would indicate that the glacier here was not very thick. That the country ai-ound the present lake outlet has been in places subject to abrupt changes of level is shown by the heavily dipping limestones at Fort Henry and eastwai'd, and the eruptions of granite through the syenitic gneiss und the limestone both here and farther down the river. There is some evidence to show that an eruption took place during the deposition of the Black Eivei* limestones, but the abrupt upheaval of these limestones at Fort Henry and Barriefield is conclusive that there were forces at work, operating in a somewhat westerly direction, nubsequent to the Trenton and Black River, and possibly in recent, times. That Lake Ontario has had a pre-glacial origin seems beyond question. Several causes have contributed to bring about its present outline and depth, and it may be that one or more of these causes operated aftei" the glacial epoch. Towards the western and on the southern side the Medina sandstones and the Hudson Eiver shales sink apparently north-westerly under the lake^ at the eastern end the Trenton and Black River limestones dip to the east of south, and the general slope of these limestones between Kingston and Belleville is perceptibly towards the lake. There is thus some ground for the assumption that the Trenton limestones, Utica and Hudson River shales and Medina sandstones descend both ways under the lake waters, foi-ming perhaps originally, in at least a part of the lake, a synclinal trough 274 Canadian Record of Science. m which was affected by after chaiif^es. The relative poHitions of these strata around the lake further HU^^uBt this. Anothei' feature, however, has played an important part in the formation of not only Lake Ontario but also of Lakes Huron and Michigan, and even had its strong influence on Lake Erie as well. The Niagara escarpment, which nearly fronts the southern side of Lake Ontai-io, passes around its immediate westerly end, and then, facing to the north-east, continues in a somewhat irregular north-westerly direction until it eventually forms the prominent features of the Bruce Peninsula between the Georgian Bay and Lake Huron. At Cabot's Head, at f,ho end of this peninsula, there is a break, but this is only apparent as there is a subaqueous ridge hei-e, commencing near Gape Hurd, with deep water on the Georgian Bay side This ridge, through the neigh- bouring islands, connects the peninsula with the Manitou- lin islands. The same limestones re-appear, crossing these islands, in bold escarpments facing to the northward, and extend uninterruptedly to the State of Michigan, the height diminishing to the westward. Along the northern shores of Lake Michigan they continue until Green Bay is reached, where, facing to the westward, they once more in places rise into an escarpment. Here they form two horns of the bay, with islands and another subaqueous ridge connecting them. Thence these limestones are found in the country skirting the western shores of Lake Michigan and they probably form the floor of its southern end beneath the supei*ficial deposits. The dip of the strata is, from the escarpment north of Hamilton and on the Manitoulin Islands, to and under the waters of Lake Huron. From Dundalk station on the Toronto, Grey and Bruce Eailway, on the summit of the escarpment, there is a fall of 1,119 feet to the level of Lake Huron at Kincardine, seventy miles distant. South of the valley of the River Thames, which lies on the Cincinnati anticlinal, and at Niagara Falls, the slope is towards Lake Erie. To the north of the cliffs, on the Grand Manitoulin 7 'and, are parallel escarpments of Hudson River age, form- Great Ldke Basins of the St. Lawrence. 276 in^ the bluttrt on the northern HJdo of the island, and with the HtruUi dipping Houthward similarly to those of the Niagara ago thoro. Again, tho clitlH of Green Hay face to the westward, and the dip is easterly towards and under Lake Michigan. This Niagara escarpment, in its course easterly from tho western end of Lake Ontario, lies parallel to the axis of that lake, whilst in the other direction, it conforms in a general way to the course that more or less characterizes the out- crops of all the formations which, as it wei-e conc"ntrioally, surround and underlie tho coal measures of Michigan. The contours of Lakes Michigan and Jluron and the Georgian Bay, and tho subaqueous Corniforous oscarpment crossing Lake Huron, also conform to this arrangement. At the wostorn end of Lake Ontario, the Niagara lime- stones in their outcrop suddenly change from an east and west course to one which is north-west and south-oast. When these limestones were elevated into an escarpment, two separate lines of force appear to have operated — tho one taking an easterly direction and causing the strata on the southerly side of the lake to dip in a southerly direction — the other taking a somewhat north-westerly course resulting in the strata thence to the Georgian Bay dipping more to the westward. These two forces appear to have, at the point of meeting, created a vast fi-acture in tho escarpment near Hamilton, forming what ultimately became, chiefly through tho eroding force of water, the Duudas valley. Again, between the Bruce Peninsula and the Manitoulin Islands, another change in the direction of the outcrop of both the limestones and underlying shales, caused, when the escarpment was elevated there, a series of great fractures which, by the action of the waves and curi'ents and of atmospheric forces, and possibly of glaciers and icebergs as well, became, ultimately, the interrupted subaqueous ridge there. To similar fractures were no doubt originally due the narrow straits which divide the Manitoulin Islands from each other and the most westerly of them, Drummond Island, from the State of Michigan. Such fractures may 276 Canadian Record of Science. perhaps be found on the upper peninsula of Michigan, but much less pronounced in character, as the strata there have not been elevated to the same extent. Finally, there are the fractures which afford the entrance to Green Bay, and those which constitute the various bays around the whole front of the escarpment. Now, these different facts are not mere accidental oc- currences, and their conformity to each other is not a mere coincidence. They show that the oscillations of the earth's crust in this particular area, covering the State of Michigan, the larger part of Lake Huron, and the immediate country to the east of Lake Huron, and to the west of Lake Michigan have, from the Trenton period and probably earlier, been of a peculiar nature. These oscillations were confined to this area, and the forces which gave rise to them appear to have operated in conformity, in a general way, with the curved outline of the area and towards its centre. It is im- possible to ascribe to glacial forces the varying directions of the outcrops of the different formations within this area, from the Trenton to the Carboniferous, nor do the glacial striae or the alleged directions taken by the glaciers suggest it. it is most reasonable to assume that this area, located as it is close to Lake Superior, whore during Huronian and Keweonawan or probably later times wei-e vast volcanic eruptions, has been subject to repeated oscillations in level around a central area. That these oscillations have con- tinued to more recent periods is shown by the uplifting, west of the longitude of Hamilton, of the Niagara escarp- ment with its face always away from, whilst the dip is towards, the central area of the State of Michigan or of Lake Huron, as well as by the depression and re-elevation of this whole area when the present superficial clays were laid down. That the Niagara rocks did not extend much farther north of their present position near tbo southern coasts of Lake Ontario, nor much farther eastward than the escarpment be- tween Lake Ontario and the Georgian Bay, is shown by the present general position and direction of these and the Great Lake Basins of the St. Laurence. 27*7 underlying rocks to the immediate east, south and west of the lake, and the way in which they converge at the south- em extremity of the Georgian Bay. A similar opinion may be ventured regarding the Medina sandstones. Prof. Bell, referring to Lake Ontario and certain other lakes, thinks that the glaciers descending from the higher grounds against the upturned edges of the softer rocks, tore them up rapidly, and carried away the debris, thus leaving the lake basins. The sharply defined edges of the escarpment, its generally bold face, and the comparatively short distance it has apparently receded, would, however, i-ather indicate in its case atmospheric effects, the wearing force of rivers, and the undermining action of waves upon an open lake or sea coast. Sir William Logan, in the Geology of Canada, points out the resemblance of the Niagara escarpment, in places, to an ancient sea cliff. He also shows that it merely requires a depression of 442 feet to bring the ocean into Lake Ontario by way of the Hudson Eiver and the Mohawk Valley, as well as by the St. Lawi-ence, and to inundate the whole of Central Ontario, although he did not then think that there was evidence thai such an inroad had taken place. Such a depression would lead to the ocean penetrating as far west iis the Niagara escarpment, and as far northward, in some places, as the Laurentian hills. The Georgian Bay would still be 140 feet above the ocean level, but if the thick de- posits of sands, gravels and clays, between it and Lake Ontario, the positions of some of which are attributable to relatively very recent times, had not then existed, or were cut through at any point, the Georgian Bay would have been lowered to the ocean level, and have formed part of the same interior ocean as Lake Ontario. This would bring to the surface the presently submerged ridge between the Bruce peninsula and the Manitoulin Islands, owing to the lowering of Ijakes Huron and Michigan to the level of the surface of the ridge. The outlet of these lakes would there- after be over this ridge, and not by way of Lakes St. Clair and Erie. Now, the deep water cliffs on the eastern side of 21S Canadian Record of Science. the subaqueous ridge, between the Georgian Bay and Lake Huron, and those which are immediately beneath the escarpment of the Bruce peninsula, would seem to indicate that the waters of this bay have been at much lower levels than now to admit of the denuding action of waves and atmosphere on these subaqueous cliffs, and further, as already mentioned, that these cliifs formed the western boundary of a large and rapidly flowing pre-glacial river which, before the upheaval of the ridge between the Georgian Bay and Lake Ontario, connected these two basins, the denuding of the escarpment being due largely to it. Without further here discussing the question of a connec- tion between this bay and Lake Ontario, this fact is clear that at a period comparatively recent, and yet so far dis- tant that the mammoth (Euclephas Jacksoni) then living, has since become extinct, the Niagara escarpment formed the western and southern boundaryof a large interior fresh- water sea. The terraces and ridges around Lake Ontario show that this basin was considerably depress od or its out- let blocked, or that both causes intervened, raising- the water to levels probably more than 400 feet higher than now. These terraces and ridges are found resting against the Niagara escarpment at Hamilton and Dundas, rising, ♦ Logan says, to a height of 318 feet, but they must in some cases be much higher there, as they nearly reach the sum- mit of the escai-pment along the line of the Grand Trunk railway ; and whilst Bayfield mentions heights of 460 feet, Spencer gives the highest point on the summit near Ham- ilton as 516 feet. To the northward of Lake Ontario there are ridges of clay, sand or gravel, reaching varying heights. The summit on the Northern railway is attained at t55 feet above the lake, at twenty-six miles north from Toronto,^ but the levels after falling nearly 300 feet, rise again at fifty- seven miles to 641 feet, passing first through a gravel ridge at fifty-three miles. Again, on the Toronto and Nipissing railway, the summit station is reached at 893 feet, at . '■ Spencer's Elevations in Canada. ■■HMi Great Lake Basins of the St. Lavrrence. 2*79 twenty-seven miles back from the lake. Farther eastward on the Midland railway, in rear of Whitby, clay ridges are met with at twelve miles, attaining 649 feet, at fourteen miles 781 feet, and at thirty-three miles 674 feet. On the Port Hope section, further eastward, the heights are some- what less. But let us not be led astray. Being so much higher than other ridges surrounding the lake, it is clear that the underlying Hudson River, Utica and Trenton strata, have been elevated during or since the deposition of these clays, sands and gi-avels, and in a direction roughly parallel with the lake. These superficial deposits obscure the strata, but this elevation, continued in a line towards Lake Huron, is noticeable on a greater scale at and beyond the townships, where it strikes the Niagara escarpment, whose summit near Dundalk station, on the Toronto, Grey and Bruce railway, has a height of 1,462 feet above Lake Ontario, and 1,127 feet above the Georgian Bay. On the south side of Lake Ontario, where the subsequent elevation has been less than on the north side, an extended ridge of 188 feot has been thrown up. The American geo- logists have observed a gradual rise of 130 feet in this ter- race, from the western end of Lake Ontario to Oneida Lake, and a I'ise of 170 feet more from Oneida Lake north to Jefferson County, beyond which it was not observed. This would imply a previous depression, increasing in depth with the south-easterly and easterly sides of Lake Ontario, and would show that its waters, now deeper towards the south-eastern end, were relatively more so in certain pre- vious periods of the lake's history. The present levels have, as indicated, been largely influenced by the gi*eater eleva- tion on the northern than on the southern side, causing the waters to be thrown more towards the southern side. At this period the outlet of the lake at the Thousand Islands was undoubtedly crossed by the Adirondack Moun- tains in a broad, rugged, irregular ridge, now partly de- pressed under the water to a maximum depth of about 250 feet. Some sand deposits occur towards Rockport, near Brookville, and in rear of Kingston, and naay indicate the ■i if 280 Canadian Record of Science. i I eastern and western sides of the ridge, but this is, presently, mere conjecture. The height of the marine terraces on Montreal Mountain and elsewhere, as compared with the level of Lake Ontario, the absence of the Leda clays with their marine shells and fish farther west than Packenham, and the direction of the ice grooves which have a trend to the west of south on the Lake Ontario side, and, generally speaking, to the east of north or of south, on the St. Lawrence and Ottawa River sides, all tend to suggest this former higher altitude of the Laurentian ridge at the Thousand Islands. In this connection it may be noted that whilst it is usual to refer to the direction of the ice grooves as being either to the east or west of south, it is quite in consonance with the direction of the St. Lawrence Valley that these grooves should sometimes be referred to as having a course to the east of north. With the elevation of the Niagara escarpment came the first record we have in the history of Lakes Ontario, Huron and Michigan as independent basins with the contours of to-day. Previous to and after this elevation, the present basins of these lakes were the seat of a great river system, with probably lake expansions smaller and different in out- line from those now existing. Profs. Spencer and Claypole suggest that Lakes Ontario and Erie in part formed the valleys of a great pre-glacial river which, Spencer thinks, crossed from Lake Huron through the counties of Larabton, Middlesex and Elgin, and swerving around Long Point to the deepest portion of Lake Erie, trended thence northward to the Dundas Valley. Through this valley it entered the present basin of Lake Ontario, the line of deepest depression in which it formed by cutting down into the Hudson Eiver shales, along the escarpment of which it flowed. There is much in the features of the lake floors and of the superficial deposits to support some such view, if more recent local warpings in the strata are considered. The great fracture in the strata at Dundas would give the required direction to the river there, and would be greatly enlarged by its eroding aciion. The outlet of this river by way of the Mohawk Great Lake Basins of the St. Lawrence. 281 i Valley, is considered by some to be debatable ground, but it is difficult to now predicate what the levels were in the land surrounding these ancient rivers and seas. There have since been general changes in elevation extending over large areas, and there have also been local warpings within re- stricted areas which have completely altered within these areas the former levels in their relations to each other. Prof. Spencer's \'iew of this ancient river was limited to a connection between the southern end of Lake Huron and the eastern end of Lake Ontario by way of Port Stanley, Long Point and the Dundas Valley. It seems most probable, however, that the subaqueous escarpment which diagonally crosses Lake Huron from opposite Kincardine in the direc- tion of the Straits of Mackinac, and which parallels the deepest depression there, may have been the south-western boundary of an npper section or expansion of this pre-giacial river valley. The hai-d Corniferous rocks would form an ettective protecting side for such a river valley. Allusion has already been made to the probably earlier north wai-d direc. tion of this river in the line of depression toward Cape Hurd and over the subaqueous ridge there. The sub aqueous river channels, already referred to, on each side of the Straits of Mackinac and in Whitefish Bay, in Lake Superior, also indicate higher sections of this preglacial river, and if the view be accepted that Lake Superior had its outlet in these older times across the upper peninsula of Michigan, it is most in consonance with facts that the waters of this great and ancient inland sea found their coui"se to the ocean at, at least, one period of its history, by way of these broad rivers of Tertiary and antecedent times, though the St. Croix valley has, probably, at another time, also formed an outlet. At what time, however, was this Niagara escarpment elevated ? This is a question difficult of answer. And yet the facts already given would indicate that it was prior in time to the deposit of the clays, sands and gravels against the escarpment in the Dundas Valley, at the Bruce Peninsula and elsewhere ; prior to the deposit of the 282 Canadian Record of Science. Artemesia gravels, which for long distances crown the sum- mit of the escarpment parallel to its face, and are largely derived from its debris ; prior to the elevation of the ridge or anticlinal which lies between Lake Huron and the Trent Valley, and gives to the escarpment its highest elevations above the lakes ; prior to the Niagara Falls ; and prior to the erosion which widened the fractures in the escarpment at the Dundas Valley and at the points of meeting of the waters of the Geoi-gian Bay with those of Lake Huron proper, as well as the waters of Green Bay with those of Lake Michigan. On the other hand, this period of eleva- tion of the escarpment was contemporaneous with the ap- pearance in their present outlines of Grand Manitoulin, Cockburn and Drummond Islands in Lake Huron, and viewing all the facts was undoubtedly pre-glacial. Whilst the elevation of the escarpment gave in general tcnns the outlines of the basin of the three lakes, it is not to be in- ferred that these basins were at once filled with water to present levels. The countiy surrounding the lakes must have been higher than now to enable the pre-glacial river to cut the deep channels in Lakes Ontario and Huron which now exist. M Laejbs Erie and St. Clair. These two lakes have undoubtedly been within a veiy recent period more intimately united than now, and are probably the most recent in origin of the St. Lawrence Great Lakes. They lie in a Devonian basin with the Silurian rocks forming the portion of the rim of Lake Erie between Sandusky and Toledo. This basin is, however, over- laid with superficial deposits to such an extent that both lakes really fill shallow depressions on the surface of these deposits, and appear rather to be overflows caused by the restricted passage now of the waters over the Niagara escarpment in the one case, and through the Detroit River in the other, than to be due to physical forces which operating in past ages excavated preparatory basins. Oreat Lake Basins of the St. Laivrence. 283 Lake St. Clair has an average dejbth of about 12 feet and a maximum depth of 22 feot. The floor, except some limited areas of mud and clay in the centre, is overlaid everywhere with Hand. The coast lines are low and often marshy, and, along the Canadian side fronting the counties of Essex and Kent, the land is barely elevated above the lake surface. The whole country here has quite the char- acteristics of the modern prairie, and its formation is un- undoubtedly due to similar causes which are still in opera- tion. Centuries of gi'owth and decay of tall grasses, rushes and sedges in the extensive shallow marshes border- ing the lake gradually contributed a black loamy soil which even now is not much above the level of Lake St. Clair. And not only has there been a more intimate con- nection with Lake Brie, but that the lake has at one time been somewhat deeper and is gradually filling up, is shown by the character of the deposits on its floor and by the ex- tensive, progressive delta of the St. Clair River. The heavier sediments in the waters coming from Lake Huron have been deposited in this lake, whilst the lighter silt appears to have been carried onwards towards and to Lake Erie. The Detroit Biver, which now connects Lakes St. Clair and Erie, flows through a flat prairie-like country, but slightly elevated in most of its course above the water level. At the outlet of the river, on the Michigan side, extensive marshes prevail for some distance along the lake coast. The soil, however, is a fine yellow or drab-coloured silt containing minute grains of sand — the filterings no doubt fi'om the coarser material deposited in Lake St. Clair. For a lake of such wide area, Lake Erie is remarkably shallow. A line drawn from the City of Erie in Pennsylvania to Port Rowan, near Long Point, would have on its western side more than two-thii-ds of the lake area, and yet the maximum depth there does not exceed 84 feet. Again, a line from Pt. Pel^e to Sandusky would form the eastern boundary of a large section, the greatest depth of which, 284 Canadian Record of Science. except in one isolated spot, is only 48 feet, and the average M only al>out 30 feet. Whilnt thus shallow, the main body of the lake east of Pt. Pel^e is remarkably level. The general depth is between 60 and 84 feet to within four or five miles of the shore on each side. The deepest point in the lake lies in its eastern third about ten miles south-east of Long Point, and registers 210 feet. Here, parallel with the axis of the lake, there is a depression about twenty-seven miles in length by a width of from five to six miles, the depth everywhere in which exceeds 180 feet. Surrounding this and about forty miles long by twenty-five miles wide is an irregular area which has a minimum depth of 120 feet. This wider depression approaches within six miles of the south shore and thirty- five miles of Buffalo, towards which city it gradually shoals to 24 feet at the entrance to the Niagara Eiver. The level plateau on which the main body of the lake rests is gener- ally clay, whilst for the ten miles adjoining the United States side, the lake bottom is sand or sand and clay, with, occasionally, gravel, and, near the shore, rock. In the deeper parts off Long Point, which evidently included a wider area in preglacial times, the bottom is clay or mud. This is frequently replaced by sand towaixis the Niagara River, whilst near the shore there on both sides the bottom is rock. The currents of the lake have, in the past, played an im- portant part in shaping the contour of the Canadian side. The American coast line has a uniformity which the Canadian has not. The direction of these currents is seen in the out- lines of Point Pel^e, Eondeau Harbour and Long Point and in the arched contour of the long coast line fronting the County of Elgin, whose high clay cliffs have been worn gradually backward through great distances to their pre- sent position by the eroding action of waves, frosts and rains, and have supplied material for shallowing the lake in front and building up Long Point. This process is still going on. Within the barriers created by Point Pel^e, Bondeau Harbour and Long Point it is, however, being 1 a- le in it- id he rn re- nd kke till i6e, ing Great Lake Basins of the St. Lawrence. 285 supplemented by the shallows becoming marHhes which in time will till up with mould ariHing from the annual growth and doeiiy ol' the reeds, rushes and grasses which flourish in profusion there. Leaving out of view the above subsequent changes in parts of its area. Lake Erie probably dates the outlining in a general way of its present limits back to the time when the Ontario Lake ridges were being formed, and when the clays and gravels wore being piled up against the Niagara escarpment and had blocked the Dundas valley. The entire Ontario peninsula had been under water for a long period, and by the deposition of the clays over it, the courses of the pre-glacial rivers had been partly filled up. The united lakes, as their terraces show, had at first a high level, and their wutcj's found here, as NewbeiTj' has shown, outlets to the southward through the gaps furnished by the river valleys in Ohio. On the elevation of the land, new drain- age channels had to be cut by the water. It was then that the outflow from Lake Huron began by the St. Clair and Detroit Eivers and of Lake Erie by the Niagara Eiver, the channels of the old glacial river having been blocked and the waters being kept back, not merely by the superficial deposits, but probably by warpings of the strata beneath as well. It may be that the lake level was at first retained at a higher point than now, the escarpment at Lewiston being 38 feet above Lake Erie. This would have prevented a separation then between that lake and Lake Huron. It is most probable, however, that the Niagara did not fall over the escarpment at Lewiston but found at this point, as at St. David's, a great fracture in the cliff, affording it a natural gorge down which its watei-s ran, and which they gradually further eroded. Other such fractures are found in the escarpment both south of Lake Ontario and between it and the Georgian Bay, some of them forming great ravines several miles in length, and presently, in some cases, the beds of streams. Such fractures were a necessary con- sequence of the elevation of tho escarpment and of the direc- tions which this elevation followed. 286 Canadian Record of Science. Conclusions. In summing up the conclusions of this paper it may be said : That glaciers, whilst contributing some results, had not much effect in eroding the lake basins proper, or in shaping the present genei'al outlines. That the superficial deposits are the accumulations of denudation during immense periods of time since the Car- boniferous and earl'^r eras, and are not to be specially credited to the opor...;ion of glaciers. That Lake Superior is the most ancient of the lakes, dating "'ts origin as far back as Cambrian, Keweenawan and Huronian times ; that it is, in part at least, a synclinal trough , that volcanic action has had most to do with its origin and the shaping of its coasts; that its early outlet was through the depression in Whitefish Bay and that its waters joined the great pro-glacial river system at or near the Straits of Mackinac. That Lakes Michigan, Huron and Ontario wore originally the bed of a pre-glacial river which first crossed the Ontario peninsula along the Niagara escarpment, and afterwards was diverted to a course by way of Long Point, on Lake Erie and the Dundas valley ; that their basins were largely defined by the elevation of the Niagara and Hudson Eiver escarpments, and in more recent times by warping of the strata and deposit of superficial sands and clays which blocked the old river channels and resulted in the lake basins retaining their water on the final elevation of the land to its present general levels. That the pie-glacial river system expanded in time into smaller lakes in each of the present basins of Lakes Michi- gan, Huron, j::jrie and Ontario. That Lakes Erie and St. Clair are the most recent of the lakes, and hav«) at on© time been more closely united, and that the formation of this united lake was due to the blocj^ing of the old outlets bojth by superficial deposits and warping of the strata, and to the water being thus retained Note on Balanus Hameri. 287 in the basin on the final elevation of the land to the levels oi to-day. That great fractures at or near the outcrops of the strata occasioned by the directions of the forces which elevated the strata, originated, in many instances, the deep bays and inlets which indent the Niagara and Hudson Biver escai-n- ments and rocky coast lines of Lakes Michigan and Huron these effects being afterwards supplemented by the action of waves, cuiTents, atmospheric causes and probably local glaciers. •' That since the elevation of the land to the levels of to- day, the action of waves and currents on the clay cliffs and Band deposits has, in many places, greatly rounded off the general outlines of the coast, and the material from this and other sources has been spread over the lakes, or hag served to create new features in the coast line elsewhere.