130 EXPERIMENTS IN MOUNTING THE AMPHIPLEURA PELLUCIDA. 
Lodide of barium, biniodide of mercury, iodide of cadmium. 
—These three preparations are very good, and cleaner than when 
the biniodide is dissolved in the piperine, giving a better definition 
than the watery preparation of the bini 
Lodide of antimony is prepared by intimately mixing the 
powdered metals iodine and antimony, keeping in a well-cor 
vial, and when it is required to be used, a small portion of the 
powdered metals is sublimed off the mica slip on to the cover-glass 
and mount as ate The above four iodides are not as good as 
the iodide of ars : 
0. savijnse iodide of zine are not so good, but 
still the definition is very fair. 
Lodide of silver.—Formed by first depositing a film of silver as 
in the silver film process, then heating the cover-glass, and then 
holding the cover-glass over a cell containing a little iodine; a 
very small quantity of iodine vapour is sufficient—if too much is 
used the whole of the film of silver will be dissolved. Heat the 
cover-glass before mounting 
Bromide of silver. Prepared in the same way as the iodide, 
but using the vapour of bromine. These two preparations, with a 
little manipulation, will rival any of the phosphorus and sulphur 
mounts. 
Iodide of ammonia—This salt is good, but refractory. 
liable to leave a brown stain over the diatoms if the resublimation 
is not complete; the strive well defined ; the refractive index of the 
cyrstal is very high. 
Lodide of cyanogen.—Made by intimately mixing Bier: and 
ilies = silv er. = as ema quantity in a vial ; n heat a 
before. The striz well define 
Chloridz of tellurium.—This preparation, manipulated in the 
same way as the chloride of tin, is the best medium for showing 
the A. pellucida that I have experimented with. The richness of 
the colouring is something grand to look at: the beautiful steel- 
grey striz bold and well- defi ned, with the golden-y bert edge 
of the valve, makes this the most showy slide that ca 
exhibited, and in my opinion surpasses Professor Smnith’s American 
slide,* the medium of which has a refractive index of 2° ‘4 ; however, 
you will be able to judge for yourselves, as it is intended ‘to exhibit 
them both to-night. 
__ * Professor Smith’s slide shown under a Tolles 1-10th, Powell and Lealand 
microscope and condenser ; the tellurium slide under a Larehe 1. a 
ce Mio a Swift's small working microscope, ca: Powell and Lealand’s ensel 
ee All agreed that t t the tellurium slide was far the best exhibit. — 
* 
