AMERICAN 
JOURNAL OF SCIENCE AND ARTS, 
[THIRD SERIES.] 
Art. XXIX.—On the great Lava-flood of the Northwest; and on 
the structure and Age of the Cascade Mountains; by JOSEPH 
LeConre, Professor of Geology, University of California. 
[Continued from page 180.] 
V. Some important points suggested by the previous discussion. 
A. Successive outflows of Cascade lava.—Mountain-making, 
Whether by the up-swelling of sediments or the out-squeezing 
e 
Ws, Occupying a very long period ot time. I believe it pos- 
le to detect these successive outflows—to detect in its ex- 
genous structure the lines of mountain-growth. 
. It is well known that columnar basalt, when in thick masses, 
'S often divided into horizontal layers by planes which inter- 
Tupt the continuity of the vertical columns. Magnificent ex- 
_ &tnples of this structure are found in the basalts of the Cascade 
