AMERICAN 
JOURNAL OF SCIENCE AND ARTS, 
[THIRD SERIES] 
Art. XVIL—On the great Lava-flood of the West ; and on the strue- 
ture and Age of the Cascade Mountains ; by Josep LeConrz, 
Professor of Geology, University of California. 
Dvrine the past summer, I made a geological tour through 
Portions of central and eastern Oregon, the principal object of 
Which was to examine the great lava-flood which covers this 
region, and more especially to study the structure and deter- 
tine the age of the Cascade Mountains. In this tour I was 
‘Accompanied and greatly assisted by Rev. Mr. Condon of the 
I. The great Lavajflood.* 
Ertent—As already stated in my paper on the “great fea- 
tures of the earth surface,”+ this is probably the most extraor- 
dinary lava-flood in the world. Commencing in middle Cali- 
prila as separate streams, in northern California it hecomes a 
flood Howing over and completely mantling the smaller ine- 
qualities, and flowing around the greater inequalities of surface, 
While in northern Oregon and Washington it becomes an abso- 
*] 3 Be 
Wunlive rece, te lava here, and elsewhere in this paper, as synonymous 
* This Journal, vol. iv, p. 470. 
Am. Jour. ules 7 Vou. VII, No. 39.—Manca, 1874. 
