53 
lowing whole prisms. In this way the dispersion of fourteen 
prisms is made use of, and the results obtained superior to 
what has been got in any other manner. Although some- 
what indistinct in detail, the photographs show the promi- 
nences in a satisfactory manner, as to outline. 
Pror. C. A. SEELY called attention to a property of Gun 
Cotton which he considered new, or at least, unrecorded. It 
was well known, that Gun Cotton was soluble to a very con- 
siderable extent in alcohol, which held Gum Camphor in so- 
lution. A knowledge of this fact had been made use of in 
the arts, for the manufacture of an artificial ivory, which was 
reported to be fully equal, if not superior, to the genuine 
article. In making this substance, the Gun Cotton is ground 
up with the Gum Camphor, by means of water into a pulp, 
and then pressed into a solid mass, whilst being heated to a 
temperature of about 300° F. Taking this fact into consider- 
ation, he had thought of ascertaining what would be the 
effect of exposing Gun Cotton to the action of the vapor of 
Gum Camphor. Therefore a small quantity was thus exposed 
in a glass tube; the Camphor being heated to a temperature 
just high enough to volatilize it. He was surprised to find 
that after a short time the tube became filled with red vapors, 
aud ultimately the Gun Cotton exploded. Now, as in the 
manufacture of the artificial ivory mentioned, the mixture of 
Gun Cotton and Camphor is exposed to a much higher heat 
than that he had made use of, it was a fact worth taking into 
consideration, as to whether there might not be danger of 
explosion resulting. It is true, that ordinarily there is water 
present, but towards the end of the process this is all pressed 
out, and a dry mass is left. Therefore as a precaution, it is 
as well to remember this fact thus ascertained. 
