AMETRIGAN GEA CIAL DEPOSITS. 2y7al 
the earliest known glacial invasion, but whether the accumula- 
tion was immediately antecedent (and so contemporaneous with 
some of the advancing stages of glaciation, or with some of the 
deglaciation stages that may have interrupted tlhe advance), or . 
whether it was more distantly antecedent, is an altogether open 
question. The perishable nature of such deposits offers some pre- 
sumption that they were not very greatly antecedent to the maxi- 
mum ice invasion, and, to that slight extent, offers a presump- 
tion that they were contemporaneous with the earliest stages of 
the glacial period in the larger application of the term. 
The Kansan formation (=Saxonian ?).—The earliest forma- 
tion which has been worked out into sufficient definiteness to 
merit specific recognition in the United States is an expansive 
sheet which reaches southward nearly to the junction of the Ohio 
and the Mississippi and southwesterly beyond the Missouri. The 
term Kansan has been applied to it because of its great extent 
in the direction of the arid plains and because it appears in the 
State of Kansas free from complications with other formations. 
It consists essentially of a sheet of till with associated assorted 
drift. Only the assorted material which was essentially contem- 
poraneous with the till is here included. That which overlies it 
and was not formed at the same time is referred to the succeeding 
horizon. 
There is a striking similarity between the Kansan formation 
and the Saxonian of Dr. Geikie. They both alike represent the 
greatest extension of the ice sheet. They are alike in terminat- 
ing in an attenuated and worn border, inthe main. They are 
neither corrugated by great peripheral moraines, as a rule, nor 
by longitudinal drumloidal ridges, nor, in general, by great esker 
systems, or kame aggregations. None of these features are entirely 
absent, but they have a relatively inconspicuous development. 
The relations of the two to succeeding formations are essentially 
identical. 
While no correlation across so great an interval as the Atlan- 
tic can command the utmost confidence until the cause of gla- 
ciation shall have been demonstrated, and shall have been shown 
