Life of Zadock Thompson.—Perkins, 71 
Northern Guide, 1857, pp. 45. 
History of the State of Vermont. For the use of Schools and Fam- 
ilies. 1858, pp. 252. This appears to be only a reprint of the work 
published in 1833, and the preceding a reprint of the Guide published in 
1845. 
THE DURATION OF THE TORONTO INTER- 
GLACIAL PERIOD. 
By A, P. CoLemMan, Toronto, Canada, 
In an article on the Toronto and Scarboro Drift Series in 
_the American Geologist for November Mr. Warren Upham in- 
terprets the facts which have been demonstrated regarding the 
Toronto interglacial formation as proving that there was only 
a brief recession of the ice followed by a short readvance, the 
whole requiring “only a few hundred years, or perhaps a 
thousand years more or less.” He believes that the whole 
history of the deposits was subsequent to the beginning of the 
formation of the Niagara gorge, and probably “in companion- 
ship with the great glacial lakes, Agassiz, Warren, Algonquin 
and Iroquois.” 
His conclusions are so entirely opposed to my own and to 
those of other geologists who have studied the formation in the 
field that a brief statement of the other side of the question 
seems called for; and all the more, since Mr. Upham’s long ex- 
perience and excellent work as a pleistocene geologist enable 
him to speak with authority on many points in the glacial 
and post glacial history of America. Interglacial periods he 
seems to have studied much less carefully. 
As Mr. Upham apparently accepts without hesitation my 
detailed statement of the facts,* quoting several pages of it, 
one may take it for granted that the difference between us is 
purely one of interpretation. All that is necessary then is to 
refer to points bearing on the length of time required to form 
the deposits, and on the climate and other factors, showing 
the extent to which the ice receded during interglacial time. 
In the sections near Toronto we find the following series 
of events recorded: 
An older deposit of boulder clay resting on the preglacial 
surface of Hudson River shale has been eroded by streams, 
*Jour. Geol., vol. ix, No. 4. 1901, pp. 285-310. 
