CALIFORNIA ACADEMY OF SCIENCES. { 
SAME si ss a AS MER Eg pO 
| 
| 
' 
| 
MISSISSIPI 
Mete rie Tron. Central mass, 
Basalitic Lavas. 
A 
B 
” ; 
C, Porpltyry Trachytes, Pumice, ete, 
D Granj te Zone, 
£. 
Strati fied or Secondary Rocks, 
v 
IDEAL SECTION ON FORTIET}1 PARALLEL, N, (AFTER PROF. HITCHCOCK.) 
(SEE Pace 123.) 
