REVIEWS 109 
ward, and thus invites filling from above. It is furthermore often the 
case, perhaps indeed the rule, that the bark of roots decays more 
slowly than the interior, thus preserving the tube for a time after it is 
open to intrusion from above. In the growth of the trees the roots 
heave the earth about the base of the trunk, and this raised position is 
obviously the first to collapse on the initiation of decay. Now there 
are special reasons why implements were somewhat more likely to be 
lost about the base of a tree than elsewhere, for its shade was naturally 
soucht for rest, for shelter, for sedentary work, such as the making and 
repairing of implements, for the gathering of nuts, for climbing, and 
for a multitude of incidental reasons. Missiles, though not in point 
in this case, were likely to be arrested by trees, especially as they were 
often directed at game in them. The mounds and intrusive burials 
mentioned by Mr. Huston imply that this was a frequented spot, and 
that lost and discarded implements would be not uncommon. Articles 
lost at the immediate foot of a tree would be liable to fall into the 
stump cavity on its decay, or to be trodden into it, and to follow down 
the root tubes as the rotting progressed. With the prolonged decay of 
the centuries the organic matter disappears in such porous beds, and 
the signs of intrusion become exceedingly obscure. It would be a 
rash geologist who would claim that he had detected all of the multi- 
tude of refilled root-tubes of a possible three score or more of genera- 
tions of forests in an inspection of a gravel bank, unless he most 
assiduously searched for them. It is no detraction, therefore, from the 
assumption of fair competency or perfect honesty on the part of the 
observer, to withhold complete confidence in the inspection of Mr. 
Huston, so far as it is supposed to exclude intrusion by the more 
occult methods of which this is a type, though his observations may 
fairly be assumed to exclude intrusion by burial, to which his attention 
was directed. 
Following the statement of Mr. Huston, the author discusses the 
vital question of the age of the gravels. He calls attention to a line 
of terraces resting on rock shelves about 300 feet above the river (?. ¢., 
220 feet above the implement-bearing terrace). These bear granitic 
pebbles, and are appropriately referred to the glacial period. They 
occur at intervals along the Ohio up to its head, and follow the Alle- 
gheny River so far as it skirts the glacial border. He notes the oppos- 
ing views entertained respecting the age of these, rejecting that which 
involves two glacial epochs separated by the erosion of the gorge in 
