164 Walker’s Statistical Atlas of the United States. 
to have tested the temperature of the water at the top and the 
foot, to see if the entire fall of 2,550 feet sensibly heated the 
water. We became convinced that the rapid evaporation then 
taking place would vitiate any results obtained, so the experi- 
ment was not tried as it involved too much labor to be expended 
for so unsatisfactory a result. And on examining this hail, the 
cause of its formation, which immediately suggested itself, was 
evaporation. 
The stream was then swollen by the melting snow which was 
still deep on the heights, and was abundant in niches to the 
very crest of the fall (which has an altitude of about 6,600 feet 
above the sea). The volume of water each day was least in the 
by its expansion, freezes a part of the spray. 
Art, XXIII.— Walker's Statistical Atlas of the United States. 
(Second paper.) 
In a former notice of this excellent work we sketched its 
plan and scope, reserving for another article some further notice 
of its first part. This relates to the “Physical Features of the 
United States,” and is the part to which students in the physical 
sciences naturally turn with most interest. 
e first map relates to the ‘‘ River Systems,” and the first me- 
moir to the “Physical Features.” The map was prepared by Gen. 
A. von Steinwehr, and the memoir by Prof. J. D. Whitney, these 
authors having worked independently of each other. About 
seven-eighths of Professor Whitney's sketch is devoted to the 
mountain frame-work or skeleton of the country, and that of the 
River Systems supplements this. One may be said to describe 
the anatomy of the country, the other its ae . This map 
