132 EXPERIMENTS IN MOUNTING THE AMPHIPLEURA PELLUCIDA. 
Metallic tin.—On holding a prepared cover-glass over tin in in a 
molten state, an impression is given to the valves which om 
mounting in piperine the striz are as well defined if not better 
than with the biniodide of mercury. 
Metallic lead.—The same as the metallic tin. ei two last 
preparations will prove what little is required to impres- 
sion which may wonderfully increase the resolution of the striz of 
delicate diatoms, and in taking the whole of the previous media 
in consideration, will show how a ua, homogeneous lens 
may do the work of a high-angled on 
Disulphide of arsenic with sulphw a a experimented on 
the disulphide by itself, I found that it is very refractory. By 
adding an equal part of sublimed sulphur, and intimately mixing 
and gently fusing the mixture; and on subliming it on to a prepared 
cover-glass, and then remelting the sublimate, a medium is obtained 
which far excels the sulphur by itself, giving a yellow amber- look- 
e 
valves will be found to have as showy an appearance as the tellurium 
preparations, and quite as good. 
Disulphide of arsenic with buniodide of mercury. __'These two 
preparations intimately mixed, and sublimed = melted as with 
the sulphur preparation, is almost as good as the preceding one ; 
in the first instance a little of the black sulphide of mercury 
may be formed, but on remelting the sublimate it entirely disap- 
pears. 
Trisulphide of antimony.—Pentasulphide of antimony. —Both 
these preparations give a splendid se and must be manipu- 
lated in the same way as the disulphide of a — Viz. , a 
mination 
investigations up to the present pes but I 
feel that I am only on the threshold = this importan rtant subject, 
would necessitate laborious chemical oat besides microscopical, 
and a I must leave it to younent and more able hands to oe 
go on - 
