78 THE HAMILTON ASSOCIATION. 
An amateur can easily construct a polariscope, and the production 
of these gorgeous colors is extremely interesting. Again, common 
glass when put in the polariscope does not exhibit colors, but when 
strained in a press shows them beautifully. No test for annealed 
glass is comparable with the polariscope. The very inner arrange- 
ment of the molecules seems to be thus revealed. Ifa sample of 
rock be ground to about the thickness of ordinary writing paper it 
will show in the polariscope most beautiful colors, and, what is more 
important, will show to the petrologist the precise composition of 
the specimen. Another application of polarised light is in the 
analysis of sugar and sugar solutions. The levying of duty is pro- 
portional to the strength of the sample, and the polariscope is in 
daily use in the custom house to determine this. There are many 
other applications of polarised light of commanding importance in 
science and industry, and in many cases extremely beautiful as well. 
In addition to the Society’s projecting lamp, a powerful lantern 
polariscope, with its numerous accessories, belonging to the Univer- 
sity of Toronto, was used to exhibit the various effects described, 
and in the management of the apparatus the lecturer was most 
efficiently assisted by Mr. W. P. Near, B. A., who accompanied him 
from Toronto. | 
