Spencer.] ^^^ TMarch 18, 



Vienna, at a depth near its known margin of 300 feet, but at a probable 

 depth in the centre sufficiently great to drain Lake Huron. 



6. The Preglacial valleys (now buried) of Ohio and Pennsylvania — for 

 example ; the Cuyahoga, Mahoning (reversed), and Allegheny (deflected), 

 formed tributaries to the great river flowing through the Erie basin and 

 the Duudas valley. 



7. The bays and inlets north of Lake Huron are true fiords in character, 

 and are of aqueous origin. 



8. The Great Lakes owe their existence to sub- aerial and fluviatile agen- 

 cies, being old valleys of erosion of great age, but with their outlets closed 

 by drift. Glaciers did not excavate the lakes and had no important action 

 in bringing about the present topography of the basins. 



9. The old outlet of the Niagara river, by the valley of St. David's, was 

 probably an interglacial channel. 



I. Introduction, 



"Whilst residing in Hamilton, Ontario (1877-89), a portion of my time 

 was devoted to studying the geology of the neighborhood. At first it began 

 in connection with Lieut. Col. Grant, H. P., Sixteenth Regiment, and 

 some otber gentlemen, in making collections of fossils ; as this locality 

 is one of the best for obtaining Niagara Fossils (and also those of the Hud- 

 son River Formation from the drift pebbles in the beaches) in Canada. In 

 1874, the present writer published in the Canadian Naturalist a sketch of 

 the local geology. In 1878, he laid the plan of collecting the information 

 necessary for preparing an exhaustive paper on the Geology of the region 

 about the Western End of Lake Ontario. "When systematic work was 

 commenced, the information gained required so much time for its study 

 that it has long delayed the publication. A large number of new species 

 of Niagara fossils (twenty-nine of the Graptolite familj- alone) were ob- 

 tained. The present state of the work is, that a paper on the Palseozoic 

 Geology, and another on the Palaeontology, containing descriptions of 

 many new fossil species, are ready for publication. A third portion, on the 

 Surface Geology, is under way ; and the investigations on this subject have, 

 step by step, carried the writer outside of his original field, — having as- 

 sumed an importance never anticipated ; and have resulted in this advance 

 notice of a few of the most striking facts concerning the origin of our great 

 lakes. The completion of the work will be further delayed until oppor- 

 tunity will have been afibrded to study some questionable points, espe- 

 cially such as relate to the drift deposits of the region, and others hav- 

 ing a broader bearing on the physical geography of the- lake regions in Pre- 

 glacial times. 



In the present paper, all discussion relating to the vexed glacial hypothe- 

 sis is scrupulously avoided, except those questions bearing on a true expla- 

 nation of the origin of our great lakes. 



In the study of the surface geology, the first great question that pre- 

 sented itself was, "What is the origin of my native valley, Dundas?" The 



