EL. Desor on the Drift of Lake Superior. 97 
for instance, in the plains of Wisconsin and Illinois, which from 
this feature, have been denominated rolling prairies, in opposi- 
tion to the level prairies, which are mostly alluvial. ‘The shores 
of Lake Superior are, in this respect, less striking—owing, no 
doubt, to the fact that the country is less level, and also in con- 
titres 
Eedtly, 
, striking on the lake shore. 
There can be no doubt that, as a whole, the drift sand and 
gravel is a stratified deposit, although the stratification is perhaps 
more imperfect than in auy other sedimentary formation. . The 
strata are generally most distinct where the mass is composed - 
of fine sand. They are less conspicuous in the gravel, except 
the alluvial sand.. They are less frequent where the deposits as- 
| re loamy character. It is well known that this dis- 
a 
oan Stratification is not limited to the quarternary deposi ts, 
toceurs in sandstone of every age. Along ke Superior, 
ary formations, side by side, thus showing that the same laws of 
deposition, even in minor details, have prevailed at all times in the 
formation of the earth’s crust. Some doubt still exists as to. the 
“atse of these singular stratifications. The attention of geolo- 
os Was first directed to them in the recent deposits of the val- 
They Switzerland, where two rivers (the Rhone and Arve ) meet. 
eee of two currents of variable strength, contending 
from each other in the same bed, whence the strata. resulting 
pe this conflict were called stratifications torrentielles.. In this 
¥ the Swiss geologists succeeded in explaining, not only the 
terials inclination of the strata, but also their difference of ma 
.s; When it happens that one of the currents carries coarser 
vanes than the other. It is evident, however, th — 
tne does not apply to. the similar structure of the sand - 
) along th ; | w ere th co! f 5 
an 
Sttoxo Seats, VoL XIII, No. S7—Jan, 1852, wee 
