66 Scientific Intelligence. 
length, the reverse of what takes place with transparent bodies. 
The diminution, however, is very different with different metals. 
The prime azimuths partly increase and partly diminish as the 
wave-lengths become less. Platinum shows a maximum value for 
the line D, cobalt and bismuth for the line Z#, and tin for the 
line # 
Observations were also made with thin transparent layers of 
gold, silver and platinum of thicknesses varying from 8 to 75 
millionths of a millimeter. They show that the prime angle of in- 
cidence and the prime azimuths increase as the thickness increases, 
ut in different degrees for different colors, With silver the prime 
azimuth exhibits a maximum value for a certain Fraunhofer line, 
which maximum moves toward the red end of the spectrum as the 
IL GroLtoay AND NATURAL HIsToRY. 
1. Small size of the Brain in Tertiary Mammals, by Prof. O. C. 
Marsu.—At the last meeting of the Connecticut Academy of Arts 
and Sciences, June 17th, Prof. Marsh of Yale College made a com- 
munication on the size of the brain in Tertiary Mammals. His re- 
age size of that in existing Rhinoceroses. In the other genera 0 
this order, Zinoceras Marsh and Uintatherium Leidy, the small- 
had small brain cavities, much smaller than their allies, the Mio- 
cene Rhinocerotide. The Pliocene representatives of the latter 
up had well developed brains, but proportionally smaller than 
ving species. similar progression in brain capacity seems to 
be well marked in the equine mammals, especially a the Eocene 
Orohippus, through Miohippus and Anchitherium of the Miocene, 
