162 
A projection of the observations given above is shown in 
the following diagram : — 
Mr. E. Bowman, M.A., and Mr. A. Brothers, F.R.A.S., 
illustrated the phenomena of “sonorous” and “sensitive” 
flames by a series of interesting experiments. 
“ On the Casting, Grinding, and Polishing of Specula for 
Reflecting Telescopes, Part IV.,” by James Nasmyth, Esq., 
C.E., Corresponding Member of the Society. 
In this part of his paper the author gives detailed 
descriptions, illustrated by diagrams, of his methods of 
mounting the specula of reflecting telescopes, and of testing 
the figure of the great speculum ; he also offers some very 
useful remarks on the general management of Newtonian 
reflecting telescopes, and on the atmospherical circumstances 
which affect their performance. 
