300 



(IN Till', l'i:i:i(tlil('\L RISE A.\l> PALL <>K THE LAI 



| 1854. 



lationa may 1h-. mode sufficiently accurate to determine nearly 

 tin' amount of surface drained ; and if our climate, as i .-ill'' [ed, 

 allows a successive Beries of cold and moi I reai , and of warm 

 and dry ones, mutually following each other, variations in the 

 volume of water cannol bul I"- great. Taking into occounl only 

 the central ami upper divisions of the St Lawrence valley, from 

 Niagara to the North weal angle of Lake Supeiior, embracing all 

 tli.' i-iiiuilry whose streams are tributary I" the Lakes, tin; sur- 

 face drsiincd is ralrulatinl (as slu-wa by a table of sections) at 

 248,775 square miles, besides 86,760 square miles occupied by 

 the Lakes; and it is further calculated that the enormous accu- 

 mulation of water discharged through the Kiwr Detroit during 

 high floods, allowing a current of only one mile an hour, is not 

 less than 95,1. "55,000 cubic feet per hour, or 1,585,558 cubic 

 feet per minute. The floods on Lake Ontario, however, are 

 generally the highest by about two feet; and lor this obvious 

 reason, that it receives the successive accumulations of all the 

 Lakes, from the Niagara to tho St. Louis Rivers, at the head of 

 Lake Superior. 



According to Mr. Mather's report for 1841, which is the next 

 testimony to be adduced: "The preceding year (1840) was the 

 second since the unusual elevation of the waters of the Lakes, 

 since which time there had been a remarkable coincidence in 

 the ratios of subsidence, the more unlooked for when taken in 

 connection with the causes which tend to equalize the amount of 

 falling water in the form of rain, snow, and dew, with the con- 

 stant action of evaporation." * * * * 



"The diminution in a given quantity of water exceeds by evapo- 

 ration all the supplies which it receives from rain — i.e., the average 

 amount of falling water is equal per year to thirty-three inches; 

 but the evaporation will reduce it to forty-four inches, when fully 

 exposed to the sun and air. One season of extreme drought 

 would, upon the expanse of these Lakes produce an extreme 

 depression, while the contrary would produce a corresponding 

 rise. It cannot then be matter of much astonishment that such 

 expanded areas of water, subject to such influences should bo 

 greatly affected. The/ w< inder is that they do not often qr present 

 greater fluctuations. The equal and almost unvarying stage at 

 which w'e find them is due to the conformity of the seasons, and 

 tiic systematic order in which nature conducts all her works., 



" The semi-annual alterations observable in summer and winter 

 arise from other well known causes. In summer the supply is 

 unchecked, and the consequence is an increase to the height of 

 about thirty inches; when in winter these supplies are again 

 checked, a consequent depression follows. Measures to ascertain 

 exactly the semi-annual fluctuations have never been thought 

 necessary. Besides it is not uncommon for ice in large bodies 

 to collect at the outlets Of the Lakes, and for a time prevent the 

 usual discharge, as was the case at the outlet of Lake Huron in 

 connection with a west wind in 1824 and 1831, when the depth 

 in the Detroit River opposite the City of Detroit was diminished 

 over ten feet." * * * * * 



" Besides all this, the effect of w-inds acts sometimes in favour as 

 well as against the other irregularities. The geographical position 

 of the Lakes is such as, that allowing them to prevail from the 

 same pointat the same time, over them all, which is by no means 

 always the case, they produce a variety of results. A west wind 

 forces the waters of Lake Erie into the Niagara River, at the 

 same time that the waters from the foot of Lakes Huron and 

 Michigan are forced into the straits of Michillimackinac, and there 

 again are met by the waters of Lake Superior, through the straits 



of Ste. Marie. Hence the straits which connect Lakes Huron 

 and Erie have all the indications of a tide, though irregular as 

 to lime, as well as to the amount "in elevation and depression; 

 and it baa often both risen and fallen in aboul 

 lion, and sometimes in the bs ids as the lunar tides of 



tl Rivers which empty into the Ocean. But when even 

 tin e tides take plaee, either in the Lakes themselvi , or in the 

 straits connecting them, they are E the results of 



accidental disorder mmiiioii throughout the Lake region. — 

 Another feature may be observed of the Lakes, different in 

 nothing from the ground swell of the Ocean — the reaction of the 

 water — after having been pressed by the wind a few days "r 

 hours in one direction; — the most favourable point for noticing 

 whichis at an outlet or bay, and Lake Superior having the 

 largest surface presents the most favourable traits of such reac- 

 tion." 



Having thus nearly exhausted my scattered extracts and 

 notes, derived from American authorities, it now remains to refer 

 to a few more memoranda on the same interesting subject, de- 

 rived from British writers, such as Sir Richard Bonnycastle, Mr. 

 McGregor, Mr. Talbot and others. Among these I turn first to 

 Sir Richard's work on Canada, from.which I find taken the fol- 

 lowing disjointed extracts.* 



"The Lakes of Canada have not engaged that attention at 

 home, which they ought to have had ; and there is much infor- 

 mation about them which is a dead letter in England. Their 

 rise and fall is a subject of great interest. The great sinking 

 of their levels of late years, which has become so visible, and in- 

 jurious to commerce, deserves the most attentive observation. 

 The American writers attribute it to various causes; and there 

 are as many theories about it as there are upon all hidden mys- 

 teries. Evaporation and condensation, woods and glaciers, have 

 all been brought into play. If the Lakes are supplied by their 

 own Rivers, and by the drainage streams of the surrounding 

 forests; and all this is again and again returned to them from 

 the clouds, whence arises the sudden elevation or the sudden 

 depression of such enormous bodies of water which have no 

 tides? AY here do the Lakes receive that 



enormous supply which restores them to their usual flow? or are 

 they permanently diminishing? I am inclined to believe that 

 the latter is the case, as cultivation and the clearing of the forests 

 proceed; for I have observed within fifteen years the total drying 

 up of streamlets since the removal of the forest; and these 

 streamlets had evidently once even been rivulets, and even rivers 

 of some' size, as their banks cut through alluvial soils plainly in- 

 dicate. * * * Perhaps, whenever a 

 cycle of years occurs, in which the north-east wind prevails dur- 

 ing a year, or a series of years, the lakes lose their level ; f< >r 

 the direction being north-east by south-west such is the usual 

 current of the air, and therefore either north-east or south- 

 westerly winds are the usual ones which pass over the surface. 

 Whenever southerly winds prevail, — and in the cycle of the gyra- 

 tion of atmospheric currents this is certain, and will be reduced 

 to calculations, — the great Lakes are filled to the edge ; and when- 

 ever north and north-easterly winds take their appointed course, 

 then these Mediterraneans sink, and the valley of the Mississippi 

 is filled to overflowing. But the 

 most curious facts are that the different Lakes exhibit different 

 phenomena: the Board of Works of Ohio having stated that in 

 1837-8, the water desendiug from the atmosphere did not exceed 



* See Bonnycastie's Canada in 18-fo, pp. 270, 201 to 300 



