1890.] 
467 
[General Meeting. 
scoring and grinding action of the ice-sheet, proves to be the most 
prominent constituent of the till, amounting usually to from forty 
to fifty per cent of the whole mass ; while only from ten to fifteen 
per cent of the till is found to be true clay, the remainder consist- 
ing of sand and coarser materials of mechanical origin. This small 
proportion of clay is no more than it is necessary to regard as be- 
longing to the preglacial sedentary soil of this region. Therefore, 
we are forced to the conclusion that, although the ice age is sup- 
posed to have lasted many thousands of years, the chemical action 
of air and water upon the rocks during that time must have been, 
probably, on account of the intense cold, almost nothing. 
It was also pointed out that while the exposed surfaces or nat- 
ural ledges of even the more acidic rocks, like granite, show appre- 
ciable or considerable decomposition in postglacial times,, this 
action is usually less marked or entirely inappreciable where the 
rocks have been covered by the till, and that even the fragments 
and minute grains of feldspar disseminated through the till, being 
hermetically sealed in the well compacted clay, have almost en- 
tirely escaped subsequent chemical change. The conclusion is thus 
reached that the glacial climate was not only very cold, but that 
free access of warm meteoric waters is essential to the rapid chem- 
ical decay of the silicate rocks. 
Prof. W. M. Davis discussed the probable climate of the glacial 
period from a meteorological standpoint, and Mr. T. T. Bouve 
spoke of the formation of conglomerates in azoic rocks. 
General Meeting, February 5, 1890. 
The President, Prof. F. W. Putnam, in the chair. 
Mr. Samuel H. Scudder called the attention of the Society to a 
small collection of the elytra of Coleoptera made by Prof. G. J. 
Hinde in the postpliocene clays of the neighborhood of Scarboro’, 
Ontario. 
These clays had been carefully studied by Mr. Hinde , 1 and re- 
garded by him as interglacial in character ; the assemblage of in- 
sects found there is the largest ever obtained at such a spot, and 
K^an. journ. sc., n. s., xy : 388-413 (1887). 
