946 The American Naturalist. [October, 
themselyes, and therefore cannot well have been transported from a 
distance. 
Prof. Shaler: Organic deposits may possibly occur very near the ice 
sheet, which allows an interweaving of organic and glacial deposits. 
. K. Gilbert remarked on the observation of I. C. Russel in 
Alaska, that where the movement of the ice is very sluggish it may 
become covered with soil, or even with a growing forest, in which such 
animals as bears still live. 
Dr. Diener remarked that intercalated beds of sand were no positive 
proof of interglacial periods. In the Austrian Alps moraines no more 
than twenty years old are covered with pasture, and in the Caucausas 
the rhododendron grows to the very edge of the ice. 
Dr. Holst mentioned two moraines separated by interpolated sand, 
and thought that they might both have been formed by the same ice 
sheet. The melting of the ice leaves un unoxidized (blue) ground 
moraine, with an overlaying oxidized (yellow) upper moraine. This 
also occurs in Northern Sweden, where there is no indication of a 
retreat of the ice, 
Baron de Geer could not understand the occurrence of thirty or forty 
feet of stratified sand between two moraines of the same glacier. The 
colors are sometimes the reverse of what has been stated by Dr. Holst, 
and the boulders in the two moraines have been derived from different 
sources. 
Mr. Christie described the section of peat and silt between two layers 
of till occurring on the river Clyde, above Glasgow. 
Mr. Cadell described some five distinct layers of till occurring in a 
pre-Glacial river channel in Eastern Scotland; and also mentioned — 
another river channel, filled with coarse gravel derived from rocks 
occurring farther north in Scotland, which was covered with a later 
layer of boulder clay. 
_ Mr. McGee mentioned the importance of land forms in interpreting 
geological processes. Any primary geological classification must be 
genetic. He discussed in detail the following scheme of classification 
_ of Plistocene deposits : 
Classification of Plistocene Formations and Land Forms. 
"Á. Aqueous : 
1. Below base level. : 
t; Lacustral. 


