478 Brief Notices. 
rock-falls. Further, the oversteepness of the valley-walls that existed 
in a great many places after the final retreat of the ice of the Glacial 
epoch has had a potent influence on landslides. Earthquakes in some 
instances have been the immediate cause of the breaking away of 
rock-masses. 
The author draws particular attention to ‘rock streams’, which 
have certain features in common, both with landslides and ordinary 
talus. In general appearance these accumulations resemble long 
tongues or lobes of talus stretching far out from the base of the cliffs 
from which they were derived, over the nearly level or gently sloping 
floors of the glacial cirques. The deposits are usually bounded by 
a sharply defined steep front; their surfaces are marked by irregular 
hummocks or wave-like ridges; and the material consists of angular 
blocks of rock, averaging about one foot in diameter, with finer and 
coarser material. They characterize tracts where the rocks are much 
shattered. Ice and snow may have influenced the formation of these 
rock-streams, but the author ‘‘ believes that they are strictly land- 
slides and owe their present form entirely to the nature of their fall 
and to the character or physical condition of the rocks involved in the 
fall”. They appear in the main to be due to the rapid slipping of 
surface material. 
3. Tue JournaL oF Grotogy (Chicago) maintains its reputation for 
original essays on subjects of wide interest and importance. In the 
number for May—June, 1910, Mr. E. 8S. Bastin writes on the ‘‘ Origin 
of the Pegmatites of Maine”’, and concludes that the broader field- 
relations suggest that the large areas characterized by pegmatite 
intrusions constitute in reality the roofs overlaying granite batholiths. 
Mr. 8. R. Capps, jun., deals with the ‘‘ Rock Glaciers in Alaska”. 
These are formed of angular talus and occupy cirques, or the bottoms 
of cirque-like valleys, that were excavated at the time of the maximum 
glaciation of the region. Small glaciers still exist at the heads of 
some of the valleys, but in most cases conditions for ordinary glacial 
activity have ceased, the winter’s snows having all melted away 
during the summer. The base of the talus, however, has been filled 
with interstitial ice, and the movement of the mass in a glacier-like 
way has continued. In some respects these ‘rock glaciers’ are allied 
to the ‘rock streams’ described by Mr. Ernest Howe as essentially 
due to surface landslides. In the number for July—August, Mr. H. M. 
Eakin contributes an article on ‘‘ The Influence of the Earth’s Rotation 
upon the Lateral Erosion of Streams’; and Mr. R. E. Hore writes 
‘©On the Glacial Origin of Huronian Rocks of Nipissing, Ontario ’’. 
4, American PurnosopHtcaL Socrrty.—In the Proceedings for January 
to April, 1910 (vol. xlix, pp. 57-129) there is an important memoir 
by Mr. W. H. Hobbs on ‘‘ Characteristics of the Inland Ice of the 
Arctic Regions”. The author contrasts the physical conditions of the 
North and South Polar areas, and the differences between mountain 
and continental glaciers. The ice-cap glacier, while of smaller 
dimensions than the true inland ice or the continental glacier, is 
regarded as distinctly allied with this type, having few affinities with 
mountain glaciers. Descriptions are given of the ice-cap glaciers of 
Norway and Iceland, of the ice-covered archipelago of Franz Josef 
