or eee `S , 
/ #t 
I6) Peculiarities of the Local Drift of the Rocky Mountains. 925 
mergence of some 450 feet. The supposed glacial drift about 
Birmingham and the concentration of boulders at Wolverhamp- 
ton were regarded as due to the former agent, while the deposits 
at Cromer and the distribution of Lincolnshire chalk across 
Southern England was due to the latter. The supposed esker at 
Hunstanton was held to be simply a sea-beach, and the London 
drift deposits to be of aqueous origin. Thus the rival theories 
_ Of floating icebergs and of land glaciers were both true, the one 
for Middle and Southern England, the other for Scotland, Wales 
and the north of England ; and the line of demarkation was fixed 
by great terminal moraines, 
‘ The paper closed with an acknowledgment of indebtedness to 
= the many geologists of England. and Ireland who had uniformly 
_ tendered most generous assistance during the above investi- 
gation. 
| 
a ie 
SOME PECULIARITIES OF THE LOCAL DRIFT OF 
THE ROCKY MOUNTAINS} 
i : BY DR. THEO. B. COMSTOCK. : 
: LL authorities upon the subject of the glacial deposits of the 
ES Rocky Mountain region agree in describing them as local or 
h restricted in extent. Somie writers dismiss the matter with 
: vg remark, leaving it to be inferred that in other respects the 
Char 
muc 
_ “e Eastern United States. Others have been more explicit and 
have shown how special conditions of topography have affected 
the accumulations in certain localities. In all cases where the 
‘etails have been given the evidence is strong of excessive ero- 
‘Sion, b "i 
‘in the gulches and gorges which can be traced to such an 
deposits a resemblance to alluvium which is quite striking. On 
th 
of boulders which have evidently rolled down the steep 
read before the A. A. A. S., Section E, Buffalo, 1886, a 
acter of the drift is quite similar to the well-known débris of 
ut almost invariably the transportative effects have been 
ly slight. As a natural result we meet with much vari- 
n, while the diluvium of the subsequent melting period is 
-S Up of homogeneous materials in each instance, but wholly. 2 
local detritus. This gives to many of the unmodified morainal 
ther hand, in some places (as notably near the head of Wind ; o T 
= Wyoming) iceberg deposits are well simulated by the col- 
ra 
