660 The American Naturalist. (July, 
remains of calcareous organisms, which are cemented together by chal- 
cedony exhibiting a tendency to form concretionary granules. In some 
specimens, genuine spherocrystals of this mineral were detected. Chem- 
ical analysis of both classes of cherts show the absence of opal. The 
author regards the rocks as chemical precipitates. 
GEOLOGY AND PALEONTOLOGY. 
The Californian Coast.—A. G. Lawson presents the following as 
the sequence of events which have led to the present topography of the 
Coast of California north of the Golden Gate: 
I. A development in Pliocene time of a great coastal peneplain 
with correlative accumulation of marine sediments. 
II. The orogenic deformation of parts of this peneplain and folding 
of the Pliocene strata. 
III. The reduction of the soft upturned Pliocene strata to base level. 
IV. The progressive uplift of this peneplain to an-elevation of from 
1600 to 2100 feet above sea land, the adjacent mountainous tracts par- 
ticipating in the same movement. 
V. The advance in the new geomorphic cycle to a stage of early 
maturity. 
VI. A very recent depression of about 100 miles of the coast ad- 
jacent to the Golden Gate, and the consequent flooding of the stream 
valleys by the ocean. 
- This history is in harmony with the disastrophic record of the coast 
south of the Golden Gate presented by Mr. Lawson in a former paper. 
(Bull. Univ., Cal., Vol. I., 1894). 
Disintegration of Granite.—Of the agencies concerned in the 
disintegration of the granite rocks in the District of Columbia, U. S., 
Mr. G. P. Merrill considers hydration the most pronounced and uni- 
versal in its effects. During an examination of material from the 
region under discussion, both granite and dioritic rocks with smooth 
even faces taken from depths of a hundred feet or more were examined, 
and many, which under casual inspection showed no signs of decom- 
position, were found to disintegrate rapidly into coarse sand after a 
short exposure to the atmosphere. The author’s explanation of this 
behavior is that the minerals composing the rocks (with the exception 
