i8o The American Geologist. September, isay 
maximum at a period subsequent to the commencement of 
the disappearance of glaciations in temperate latitudes. 
(e) The accession of solar heat by the trapping process 
being the result of a positive difference between the rate of 
receipt and the rate of loss, and not being a function of Ihe 
orbital distance, a rise in temperature may as certainly follow 
in one position as another. 
(f) That glacial conditions although imposed upon lines 
independent of solar exposure, must have reached their maxi- 
mum upon areas subject to maximum precipitation, and as 
the movement of the atmosphere in temperate latitudes is 
towards the east, the west coasts of continents are more ex- 
posed to the m.oist winds and hence were more deeply glaciat- 
ed than the east coasts. The narrow North American conti- 
nent was thus more exposed to glaciation from the wide 
P'acific than was the broad Euroasian continent from the nar- 
row Atlantic. 
(g) That the northern hemisphere of low specific heat has 
progressed further in climatic development than has the south- 
ern hemisphere of high specific heat. Similarly, the Atlantic 
has been warmed to a greater extent than the Pacific* 
\To be continued. \ 
REVIEW OF RECENT GEOLOGICAL 
LITERATURE. 
On the Phenocrysts of Intriisiz'e Igneous Rocks. By L. V. PiRS- 
SON. Am. J. Sci., 157, 271-280. ■ 
The objections to the hypothesis of an intratelluric origin of the 
phenocrysts are discussed, and evidence pointing to an origin by 
crystallization "in place" is presented. The supposed manner in which 
the development takes place is as follows: As the temperature of an 
intruded aqueotts magma falls, centers of crystallization are set up, the 
intervals of crystallization of the component minerals becoming pro- 
gressively shorter as the magma becomes viscous from the escape of 
*It will probably be noted that no mention is made of light rays; 
these can be filtered by clouds and pass through in greatly dimin- 
ished intensity. It is not considered necessary to discuss their influ- 
ence at this point, as their effect is slight at temperature Approximating 
the freezing point. The gradual development of visual organs and the 
development of all other senses prior to that of sight are lines of in- 
vestigation which the author has not been permitted to make. 
