Geology and Natural History. 309 
tion, interference rays are observed which pass over the spectrum 
om the red toward the blue. The angles of incidence having 
by thin films.— Bid. Univ., eciv, 340 
Il. Grotocy anp NATURAL HIsToryY. 
miles south and west is more than 100 feet higher than heretofore 
‘Teported ; Omaha 31 feet higher; Indianapolis about 100 feet. The 
following are a few of the levels ascertained : 
Mean level of Lake Ontario above mean tidelevel. 249°99 ft. 
s Lake Erie 
Se ie ee ea, ak aca 573°08 
ry me ee eee 
- PSkG Macean. oo Oe Be 
Low water in Ohio at Cincinnati_............-.. 440 
Cairo city base, ordinary low water _......------ _ 291°23 
Saint Louis dieebnk .. ES 
sha, low water base of U. P. R. BR. _...-...-. 977°90 
ee ODO OUGUGGN oo ea ee tee ee ee ,060°40 
Denver, Col., O. P. & K. P. R. R. passenger depot 5,196°58 
Cheyenne, U. P. passenger depot ..------.-- acne 075°28 
Golds: Qeletade. 3... ee 5,728°98 
Ogden, Utah, depot track.........-.------.---- 4,803°30 
Pike's Poak oo, eee 
The level of mean tide at Albany, N. Y., above mean tide at 
New York City, was taken at 4°84 feet, as ascertained by the Coast 
