364 REVIEWS 
sheet are then discussed, its topography as well as its structure being con- 
sidered. In connection with this drift sheet a very adhesive clay known as 
“ gumbo,”’ which caps it, is described and the questions of its relation to this 
drift sheet and to the overlying loess are considered. A detailed description 
of the border of the Illinoian drift sheet is then given, which is followed by a 
description of the moraines and other drift aggregations back from the 
border. 
Remarkable instances of the transportation of rock ledges are noted. 
The striz pertaining to this invasion are discussed in some detail. The 
effect of this ice invasion and its drift deposits upon the outer-border 
drainage is touched upon, but the detailed discussion of the influence of the 
drift upon drainage is deferred to a later chapter. The chapter closes with a 
discussion of the deposits which underlie the Illinoian drift sheet. 
Chapter V. The Varmouth sotl and weathered zone—— A well-defined 
soil and weathered zone which appear between the Kansan and Illinoian 
drift sheets in the overlap of the latter upon the former are described, and 
sections are represented which show clearly the relations to these drift sheets. 
The amount of erosion effected during the interglacial stage is also considered. 
The name Yarmouth is taken from a village in southeastern Iowa, where the 
interglacial features were first recognized by the writer. 
Chapter VI. The Sangamon soil and weathered zone.— Another well- 
defined soil and accompanying weathered zone which appear between the 
Illinoian drift and the overlying loess are described. The name Sangamon 
is applied because these features are exceptionally well developed in the 
Sangamon River basin in Illinois and were there first noted by Worthen in the 
early reports of the Illinois Geological Survey. 
Chapter VIL. The lowan drift sheet and associated depostts— The 
name Iowan was applied by Chamberlin to a sheet which is well displayed in 
eastern Iowa and which had been brought to notice by McGee. The chapter 
opens with the discussion of a drift sheet of a similar age which was formed 
by the Illinois lobe, its extent, topographic expression, and structure being 
considered. The relation of this ice lobe to the Iowa ice lobe, and the rela- 
tion of each to the great loess deposit of the Mississippi basin are then con- 
sidered, after which the loess is discussed. The problem of the mode of 
deposition of the loess forms the closing topic. 
Chapter VIII, The Peorian soil and weathered zone (Toronto formation). 
The name Toronto formation, suggested by Chamberlin, for interglacial 
deposits exposed in the vicinity of Toronto, Canada, may prove to be applica- 
ble to a soil and weathered zone which appear between the Iowan drift sheet 
or its associated loess and the Shelbyville or earliest Wisconsin drift sheet 
which overlies the Iowan. Exceptionally good exposures of a soil and 
weathered zone at this horizon in the vicinity of Peoria, Ill., make it seem 
