124 EXPERIMENTS IN MOUNTING THE AMPHIPLEURA PELLUCIDA, 
which will allow the heat rays of light to pass through, absorbing = 
the luminous rays, and others again allowing the luminous rays to 
i through, intercepting the heat rays. For instance, a of 
s from an electric light properly focused and passed through @ 
cell. filled with a solution of iodine in bisulphide of carbon will 
Ba 
solution no action takes place whatever. The solution of iodine 
absorbs the sor rays, only allowing the heat rays to pass 
through ; the solution of alum intercepts the heat rays, only 
allowing the acaba: rays to pass. This will explain why some 
media tire the eye and often damage the sight. Over and over 
again I have had to stop work from this cause alone. 
Solution of phosphorus in bi-sulphide of carbon.—In a former 
article published in the August number of the Journal of the Royal 
Microscopical Society of London for the year 1882, page 579, you 
will find a detailed account for the preparation and mounting in 
phosphorus ie me, to which I have very little to add except that I 
have now got over the difficulty of preventin tion of what 
I had always looked upon as a a i aa Ae in the bi-sulphide of 
carbon. This watery element would separate and form round the 
diatoms, as globules, to use an expressive term drowning them. 
This I now obviate by subjecting the slide after mounting to the 
direct rays of thesun according to the intensity of the rays of heat 
and light the time of exposure varies from afew minutes to half 
an hour. When a smoky metallic lustre just begins to form on 
the cover-glass the process must be stopped, the action of the sun’s 
rays converts the ordinary phosphorus into the r a 
i ed under 
Sulphur.—The difficulty to get over in mounting in sulphur is to 
sikieierst its crystallization. In my first experiments I employed 
camphor, about 7}5 part to the quantity of sulphur; this process 
proved to be very unsatisfactory, as the sulphur after a few days 
would become — or opalescent, from the formation of minute 
als. n tried mentho , thymol, and iodine, and a variety 
of ebhur er anaoolls The thymol is the best and answers fairly 
well, but still a little haziness is liable to form, 
and by r - 
melting and pressing the diatoms get broken up, and the aides 
almost become valueless by the time crystallization has been 
_ overcome. 
Not being satisfied, I again commenced experimenting with the = 
1) : 
sulphur ; and knowing the effect sul hur has upon india-rubber 
determined to y f a 
5 gta ate ee, 
