28o The American Geologist. May, i9ou 
The till there lying on the rock was of an olive-gray color, being 
probably of northwestern origin. 
On Hennepin island, above the paper mill S . 22° E . 
On Nicollet island S. 5°E. 
West of the river, nearly opposite to the University, observed 
by Herrick on an exposed surface of about 100 feet by 40 
feet, mostly S. 15° E.; 
intersected by other striae bearing S . 28° E . 
On Central avenue, east of the river, at the corner of Second 
street, many directions, confused; with one exceptionally 
deep groove bearing S . 1 5" E . 
The rock at this place was covered by a compact red till, of north- 
eastern origin, brought from the region of Lake Superior. 
In an excavation for the old city market, at the corner of Washing- 
ton avenue and Second street, the bed rock was "promiscuously 
scratched, with no prevalent direction discernible." 
Changes of Glacial Currents. 
As the striatioii noted in St. Paul, in my paper already 
cited, records the latest general course of ice movement, and 
even its final deflection and almost reversal toward the open 
area of lake Hamline, so these striae of Minneapolis record not 
the early and principal course of glaciation here, but a later 
current of this part of the ice-sheet. During the culmination 
of the lowan and Wisconsin glaciation, its direction here was 
from northeast to southwest, as is known by the fact that the 
transportation of the low-er and greater part of the till was from 
the northeast. Afterward a relatively larger snowfall on the 
west than on the east changed the currents of the ice-sheet on 
this area and on a large district stretching thence many miles 
north and northeast, to the Snake and St. Croix rivers, bring- 
ing bluish gray drift from the northwest to overlap the red- 
dish drift from the northeast.* 
The Minneapolis striae all belong to the later direction of 
glaciation; or, where many courses of striation occur on the 
same surface, they testify of confused and varying motions ad- 
joining the irregularly and varyingly indented and crenate 
margin of the waning ice-sheet, fast melting away in the sum- 
mers, but doubtless sometimes readvancing slightly in the 
*Proc. A. A. A. S., vol. xxxii, for 1883, pp. 231-234; Bulletin of the 
Minnesota Academy of Natural .Sciences, vol. iii, pp. 51-56, read May 
8, 1883, published 1889; Geol. and Nat. Hist. Survey of Minnesota, vol. 
ii, 1888, pp. 409-415, 622, 625, 642, etc. 
