242 J. W. GOLDTHWAIT ALGOKQUIK AND IROQUOIS BEACHES 



conclude, therefore, that the Peterl)oro delta and the Iroquois beach are 

 synchronous, and consequently that the Iroquois beach, the Algonquin 

 Eiver, and the Algonquin beach are synchronous. Indeed, Gilbert's ob- 

 servation that the channel of Algonquin Eiver continues down the Trent 

 Valley below the plane of the Iroquois beach to Lake Ontario may be 

 quoted as evidence that Lake Iroquois had already disappeared before 

 the Algonquin River ceased to drain Lake Algonquin ;^^ in other words, 

 that the Iroquois beach is of earlier date than the xilgonquin beach. On 

 figure 2 the Iroquois shoreline is drawn as a dotted line, because of this 

 evidence that the two lake stages are not strictly synchronous. 



The question, therefore, arises : "How niucli older is tlie Iroquois beach 

 than the Algonquin beach?" Some light can be thrown on the question 

 by examining and comparing the respective water-planes. 



1 80 BASE 8 OF THE IROQUOIS PLANE 



For plotting isobases of the Iroquois beach, measurements have been 

 selected from those made by Gilbert,^^ Spencer, ^^^ Coleman,^^ and Fair- 

 child.^* Of these, Coleman's paper is of peculiar interest because his 

 conclusions concerning the attitude of the Iroquois plane are matched 

 very closely by those since reached for the Algonquin plane. The meas- 

 urements are as follows: 



Feet 



Hamilton 363* Spencer. 



Waterdown 365* Spencer. 



Cooksville 400 Spencer. 



Toronto Junction 422-425* Coleman. 



York 442* Coleman. 



Kingston Road 459* Spencer. 



Whitby 507* Spencer. 



«> Gilbert: loc. cit. 



31 G. K. Gilbert: Old shoreline of Lake Ontario. (Abstract.) Science, vol. 6, 1885, 

 p. 222. 



Old shorelines in the Ontario basin. Proceedings of the Canadian Institute, 3d ser., 

 vol. 6, 1888, pp. 2-4. 



^ J. W. Spencer : Deformation of the Iroquois beach and birth of Lalje Ontario. 

 American Journal of Science, 3d ser., vol. 40, 1890, pp. 443-451. 



On. the focus of regional post-glacial uplift. Transactions of the Royal Society of 

 Canada, sec. 4, vol. 7, 1889, p. 129. 



Evolution of the falls of Niagara. Geological Survey of Canada, 1907, pp. 203-204. 

 208, 277-284. 



as A. F. Coleman : op. cit, especially pp. 358 and 359-362. 



^ H. L. Fairchild : Pleistocene geology of western New Yorlj ; report of progress for 

 1900. Twentieth Annual Report of the New Yorls State Geologist, 1902, pp. 103-139. 

 Gilbert Gulf (marine waters in the Ontario basin). Bulletin of the Geological 

 Society of America, vol. 17, 1906, pp. 712-718. 



Glacial waters in central New York. Bulletin of the New York State Museum, no. 

 127, 1909, pp. 54-55. 



The measurements at Albion, Rochester, Auburn, Sodus, Rome, and Farrs were sup- 

 plied by Professor Fairchild from his unpublished data. 



