EXPERIMENTS IN MOUNTING THE AMPHIPLEURA PELLUCIDA. 127 
Tl peri tedon a great J prey tions; the above 
I 1 t the best and most t. Of those alkaloids 
soluble in spirit sand having a determination to erystallize on cool- 
ing, such as santonin ; valerianate of quinine is the 
non-crystallizable to mix with them ; of those soluble in pias 
For bacteria mounting, quick work, gethseen: definition, giving 
immensity of light even to the F. eye e, 1 am certain they 
cannot be surpassed, the bacteria being on like beads of coral 
when stained with a red dye. The manipulation of the alkaloids 
is the same as for the solid biniodide of mercury, and if at any 
time crystallization should set in, melt and gently press down the 
cover-glass as before. 
T ose who attempt to work with the above preparations I 
must warn them be careful not oto inhale the fumes, as on 
heating some are volatile and commence subliming before they 
melt, such as cantharidin, which sohiieste at 212°, melts at 410° ; 
others again dasomtees a little over their melting point, such as 
narceine, nitrate of furfurine, strychnine ; some again decompose 
after being mounted as iodoform 
I am sorry to say that in my investigations I found that a great: 
many of these alkaloids are very impure and dirty, which does not 
say much for the commercial morality of the manufacturers, and that. 
the greater number of these preparations would require purifying 
before they could be used with success. 
Since reading the foregoing paper at the Bae AEN Poe Section, 
on the 14th September last, I have been experimenting on the 
chromates, iodides, bromides, chlorides, and sulphides of various 
metals. 
The chromate of lead has a very high refractive index ; accord- 
ing to Brewster its refractive index ranges from 2°50 to 2:97, but 
mixture over the flame of a spirit lamp d red fumes were given 
subject pre cover-glass to the action of 
the fumes, a examin e t under the microscope 
aim t what this agent consisted of. I then sub- 
limed the chromic acid by itself and found the same result, only 
more inte: me the lead salt had nothing to do 
with it ; and on referring to Miller and Watts’ Chemistry I came 
to the conclusion that the red fumes may be the cause, but the 
