Perry.] 57 [February 28, 
erogeneous material in a disorderly state of accumulation, and 
spreads like a thick uneven blanket over the region, from the sea- 
shore far up the sides of the highest mountains. Overlying limited 
parts of this vast expanse of jumbled elements, for it is of far less 
extent, is another portion, which is composed of clays and sands, 
and is more or less stratified. It constitutes in the main the surface 
of the low plains, while it occurs very generally in the valleys, in 
some cases in those which are even high up among the mountains. 
The former is known as drift, drift proper, or typical drift; the latter 
is often called modified drift, and appears in many localities, espe- 
cially along the principal streams, in the form of terraces. These 
two masses of material are regarded as. characteristic of the Plisto- 
cene times, the divisions of which, with their distinctive hey pOl) 
may be considered separately. 
fi The Wee Period. 
This portion of the past may be called, according to the Lyellian 
terminology, the Older Plistocene period, and the inferior mass of 
matter which was just referred to as revealing its character, the 
Lower Plistocene deposit. ‘This material, however, is conveniently, 
and perhaps just as fitly, designated Drift, and the time of its accum- 
ulation the Drift, the Glacial, or the Ice period, for during its 
progress, as is admitted on almost every hand, ice in some form or 
other was predominant ; and, on its thawing, the deposit, now known 
as Drift, almost everywhere made its appearance. Although the 
latter word be usually associated with matter supposed to come from 
the wasting of icebergs, which once drifted along the ocean, or were 
drifted over its bottom, it may no doubt equally well refer to masses 
of material which glaciers have dragged, or drawn forward in their 
course. But, whatever be the term chosen for the designation of the 
times, ice in some shape or condition is generally supposed to have 
been largely prevalent during their continuance, and to have been 
their most marked and distinctive feature. In order to determine 
whether such were the case, in order also to a right understanding 
of the period, and of the work wrought duriug its progress, it is 
needful to secure at the outset a thorough familiarity with the facts. 
Let us accordingly pass a few of the more prominent particulars per- 
taining to the Glacial times, in rapid review, noticing as we advance 
some of Professor Dana’s statements. ; 
= 
