i6o 



POPULAR SCIENCE MONTHLY. 



deposits before reaching the solid strata, yet, perhaps in prox- 

 imity, the bedded rocks appear near the surface of the country. 

 These depressions are portions of ancient valleys which have been 



filled often to depths of 

 ..* K 1 five hundred feet, and in 



some cases probably to a 

 thousand feet. By chains 

 of borings the buried 

 valleys may be traced. 

 Their general course is 

 frequently shown by the 

 surface features ; but 

 without the borings their 

 great depth would not 

 be suspected. Thus the 

 Dundas Valley may be 

 taken as an example. It 

 is situated at the head 

 of Lake Ontario and 

 bounded by mountain 

 walls, but is also deeply 

 buried by drift, as shown 

 in Fig. 4. Some of the 

 filled valleys are chiefly 

 occupied with bowlder 

 clay ; in other cases with 

 both till and stratified 

 materials ; so that their burial is not always alike. Not merely 

 have many of the old valleys been filled with the sweepings of 

 the highlands, but they have been further obscured by the sub- 

 mergence of the district beneath the modern lake waters. 



The Course op the Ancient St. Lawrence compared 

 with that op the Modern Eiver. In seeking for the explana- 

 tion of the drowned and buried valleys, discoveries have been 

 made showing that some of them can be connected, and thus is 

 the change in the course of the ancient Laurentian (so named to 

 distinguish the old water way from the modern) River established. 

 The modern St. Lawrence River is characterized by the most re- 

 markable system of lakes in the world. The basins are very deep, 

 and not mere expansions of a river having no noteworthy depth. 

 In the soundings of the lakes and in the buried valleys the con- 

 necting links of a great chain of evidence are welded together, 

 showing that the ancient water way did not pursue the present 

 eccentric course, but was an ordinary river valley of large size, 

 yet its course was not everywhere coincident with that of the 

 modern stream. 



Pig. 4. 1, Hudson River formation ; 2, Medina shales ; 

 3, Niagara and Clinton dolomites with some shales ; 

 A, C, D, B, modern valley at meridian of Burling- 

 ton Heights ; a, C, D, i, modern valley at meridian 

 of Dundas ; a, c, d, e, 6, sections across, deeply ex- 

 cavated in beds of streams in western part of the 

 Dundas Valley ; 4, howlder clay filling ancient val- 

 ley ; 5, Erie clay ; 6, talus from sides of escarpment ; 

 7, old beach, one hundred and sixteen feet above lake 

 at Burlington Heights ; G, Desjardin's Canal leading 

 from Dundas marsh to Burlington Bay ; W, W, well 

 at Eoyal Hotel, Hamilton ; W, another well at 

 Dundas ; L, 0, level of Lake Ontario ; L, E, level 

 of Lake Erie. Valley at Dundas two miles and a 

 half wide and depth five hundred feet. 



