REPORTS FROM THE SECTIONS. 177 
. The essential oil of cedar-wood is as thin as alcohol, 
druns most vilely. It is, unfortunately too, a solvent of most 
f the cements usually employed in fixing the covers of dry 
nounts, Brunswick black and asphalt being readily dissolved by 
Ite To protect our slides, therefore, we must re-ring them with 
Hlae varnish or gold-size. The use of the oil, too 
compressorium, or temporarily mounted on a slip with the 
‘Placed loosely over them. It would be difficult or almost 
ple of its construction, the objects examined should be 
eve yet seen of this difficult diatom. The illumination 
from a high angle, achromatic condenser by Crouch, of 165 . 
der 
lave a slide of W. sigma, belonging to Mr. Sharp, of Adelong, 
that gentleman, who is experienced in the resolution of 
tests, inform he considered to be more difficult than 
4%, a8, with the exception of one abnormally coarse 
the slide, he had failed to resolve it at all, using for the 
Zeiss’s water lin. and ;;in. and Powell and Lealand’s 
ula din., these objectives having, in his hands, resolved 
T Valve og _ Succeeded in sharply resolving with the oil lens 
Sy igh 0 this slide with so little trouble that I anticipated an 
ie With pellucida. I prepared a slide for the purpose by 
0 pieces a dry mount of that diatom, and mounting it in 
