~~ 9 SP Cee eee 
F > Ye Pee 
sit 
Geology and Natural History. 149 
sents to us a not unfaithful picture of what Northern Siberia must 
have been like from the Urals to Bebring’s Straits.” 
4, imatic Changes of later Geological times: a dis- 
cussion based on observations made in the Cordilleras of North 
erica; by J. D. Wurrney. Memoirs of the Museum of Com- 
parative Zoology at Harvard College. Vol. VI, No. 2. Part I. 
120 pp. 4to. Cambridge, 1880.—This volume commences with a 
chapter on the glacial and surface geology of the Pacific Coast. 
It discusses the action of glaciers, argues that they cannot make 
lake basins, except through the inclosures its moraines may have 
formed, and attributes the erosion of glacier valleys chiefly to the 
latitude 36°; but owing to declining height northward, they are 
less extensive north of the Tuolumne (37° 30’) than to the south. 
: ting’ : 
as 
never entered that valley. Its walls bear no glacier-made mark- 
ings. The glacial appearances of localities farther north are also 
treated of with many interesting details. In no part of the Sierra 
Nevada are they met with below a level of 2,000 feet above the 
sea, * 
closing chapter of the work. The facts are mentioned with regard 
the former wide limits of existing lakes between the Sierra 
k 
