133 
of Edinburgh, Session 1875-76. 
seen once in a crystal of sulphate of magnesia, and have not been 
able to reproduce anything of the kind, hut the crystallisation of 
that salt is so varied and irregular that many things may pass 
unobserved. 
The only other point I shall lay before the Society is, that I have 
succeeded in producing a crystallisation very similar to that of frost- 
pictures on a window pane, and I hope to be able to make the 
imitation more perfect. For this purpose I have employed the 
sulphate of copper and magnesia, — a salt that crystallises under the 
rhombohedral system, the same with that of ice. This salt crystal- 
lises in the films from centres in a most remarkable manner in four 
different modes, viz., the true circular, the laminate, a branched or 
dendritic form, and another that I hardly know how to designate, 
unless it may he called the ostrich plume form. All these different 
forms may be observed on the plates, either simply or in combina- 
tion, and produce most varied and singularly beautiful effects. 
3. Preliminary Note on the Flame produced by putting 
Common Salt into a fire. By C. M. Smith, Esq. (Com- 
municated by Professor Tail). 
