2S'l The American Geologist. April, 1894 
model; the streams have the greatest development possible. 
no part of the land mass is undrained and the drainage flows 
off quickly without hindrance on floodplains or delay in lakes. 
A fourth model brought out the effect of a glacial accident 
upon such a land mass as the last. The perfect drainage has 
been entirely disarranged; streams in old valleys struggle 
with the glacial detritus, some are unable to follow former 
courses and from lakes escape in new directions. Lakes 
everywhere abound, on main streams, on side streams, and 
among the hills; some have no visible outlet. 
Meteorology, a subdivision of physical geography, was 
noted by specimen weather maps, foreign and American 
charts of temperature and rainfall, diagrams of vertical tem- 
perature gradients, and photographs of clouds, storm surf, and 
lightning flashes. Photographs of clouds loaned by this de- 
partment appeared in the exhibit of the U. S. Weather Bureau. 
A product of advanced student work in meteorology was a 
chart of isonomalous temperatures. The diagrams of verti- 
cal temperature gradients were perhaps more characteristic 
than the other materials of the method followed in the ele- 
mentary course. One of them showed the strong departure 
of the vertical temperature gradient from the adiabatic gra- 
dient in winter anticyclones, thus explaining the marked in- 
versions of temperature that accompany these weather areas ; 
the other exhibited the close agreement of the two kinds of 
temperature gradients in foehn or chinook winds; the differ- 
ence between the two diagrams being referred to the differ- 
ence in the rate of descent of air masses in the anticyclone 
and the foehn. 
The opportunities and methods of studying the petrograph- 
ical side of geology were made evident by samples of rocks 
with accompanying thin sections, selected from the various 
large collections of both foreign and American materials 
available for study; sample models suggested the study of 
optical mineralogy ; photographs of optical instruments, ma- 
chines, workshops, and laboratories, completed the exhibit of 
resources. A photograph showing a large electric microscope 
together with its projection on the screen of a rock slide, 
manifested an important method of illustrating lectures, 
though, of course, specimens, maps and photographs arc also 
