440 TROPICAL NATURE VIIl 
than twenty feet of frozen gravel and earth capped by a foot 
of turf. This being near the shores of the Arctic Sea may 
be a comparatively recent beach-formation and of no very 
great antiquity; but the remaining discovery was more im- 
portant. Mr. W. J. M‘Gee, a gentleman who has specially 
studied the Glacial and post-Glacial formations for the U.S. 
Geological Survey, described the finding by himself of a spear- 
head in the quaternary deposits of the Walker River Cajion, 
Nevada. These beds consist of several feet of silt and loose 
material at the top, then a layer of calcareous tufa lying upon 
twenty to thirty feet of white marl, containing remains of 
extinct mammalia, and resting unconformably upon somewhat 
similar beds of earlier date. The spear-head was found with 
its point just projecting from the face of the marl about 
twenty-six feet below the surface. Before removing the im- 
plement, he carefully studied the whole surroundings, and 
finally came to the conclusion that it had been embedded in 
the marl during its formation. The beds were deposited by 
the ancient Lake Lahonton. They have been thoroughly in- 
vestigated by able geologists, and have been referred to the 
close of the Glacial period, or about the same time as the 
hearth described by Mr. Gilbert. The spear-head is three 
and a half inches in length, finely made, and well preserved. 
About a hundred miles north-west of St. Paul, in Central 
Minnesota, a thin deposit has been discovered containing 
numerous quartzite implements. They occur at a depth of 
from twelve to fifteen feet in an old river terrace of modified 
drift, and the deposit marks an ancient land surface on which 
the implements are found, and which must have been de- 
posited at about the close of the last Glacial epoch.1 Mr. N. 
H. Winchell, State geologist of Minnesota, has found similar 
chips and implements in the upper part of the same deposit ; 
and also human bones in the eastern terrace bluffs at Minne- 
apolis, in a formation of about the same age as the above. 
The same writer reports a still more remarkable discovery 
of a fragment of a human lower jaw in the red clay and 
boulder drift, but resting immediately on the limestone rock. 
This red clay belongs to the first or oldest Glacial period, and 
1 “Vestiges of Glacial Man in Minnesota,” by F. E. Babbitt, Proc. of Am. 
Assoc., vol. xxxii. 1883. 
