XVJII ABSTRACT OF VOLUME. 



drift sheet is then given, which is followed by a description of the moraines and 

 other drift aggregations back from the border. 



Remarkable instauces of the transportation of rock ledges are noted. The stria? 

 pertaining to this invasion are discussed iu 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 uuderlie 

 the Ulinoian drift sheet. 



Chapter V. The Yarmouth soil and weathered zone. — A well-defined 

 soil and weathered zone which appear between the Kansan and Ulinoian drift sheets 

 in the overlap of the latter upon the former are described, and sections are presented 

 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 iu 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 Ulinoian 

 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 Illi- 

 nois and were there first noted by Worthen in the early reports of the Illinois geological 

 survey. 



Chapter VII. The Iowan drift sheet and associated deposits. — The 

 name Iowan was applied by Chamberliu 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 relation of each to the great loess deposit of the 

 Mississippi Basin are then considered, after which the loess is discussed. The problem 

 of the mode of depositiou of the loess forms the closing topic. 



Chapter VIII. The*Peorian soil and weathered zone (Toronto forma- 

 tion 1 ?). — The name Toronto formation, suggested by Chamberliu, for interglacial 

 deposits exposed in the vicinity of Toronto, Canada, may prove to be applicable to a 

 soil and weathered zone which appear between the Iowan drift sheet or its associated 

 loess and the Shelbyville or earliest Wisconsiu drift sheet which overlies the Iowau. 

 Exceptionally good exposures of a soil and weathered zone at this horizon in the 

 vicinity of Peoria, Illinois, make it seem advisable to apply the name Peorian, while 

 the relations of the Toronto formation remain uncertain. Other exposures as well as 

 those near Peoria are discussed. A marked interglacial interval between the Iowan 

 and Wisconsin stages of glaciation may also be inferred by a comparison of the out- 

 line of the ice sheet at the Iowan stage of glaciation with that of the outline at the 



