J. Lawrence Smith on'the Inverted Microscope. 237 
With this arrangement we need not hesitate to employ hydro- 
fluoric acid among our re-agents, as Prof. Bailey has already done, 
for the purpose of settling in a most ingenious manner, that the 
markings on certain microscopic siliceous animalcule are eleva- 
tions and not depressions, as they appear last under the action of 
this acid. 
_ On the supporting ring V, are placed the diaphragms, palaras- 
cope, achromatic condenser, &c. I have also arrange 
ring of ivory, through the edge of which two Wires pass that can 
e poles of a galvanic battery, and thereby subject any- 
thing to an electric action while on the microscope. ‘The ex- 
tremities of the wires may be united with a spiral of small plati- 
num wire, which would become heated by the passage of the 
electricity, and in this state can be brought immediately over the 
object under examination.. 
There is another and very simple method which I have adopt- 
ed for heating or evaporating liquids while on the stage of the 
microscope ; it consists of a thin plate of brass about five inches 
long and an inch wide, witha hole in the centre. About aninch 
and a half each side of the hole, there are two screws projecting 
about the tenth of an inch. When required it is placed on the 
stage with the projecting screws downwards, that prevent the 
plate from touching the stage, and the part of the plate projecting 
beyond the stage is heated by a small lamp; the heat is readily 
propagated along the plate, and imparted to the glass that may be 
placed along it. : 5 
In using this instrument for chemical purposes, it is very neces- 
sary to be able to apply the re-agents conveniently, and for this 
purpose I place such of them as are used in two ounce phials, 
in the neck of which there is a small drop tube as represented 
in fig. 3, over the top of which is stretched a piece of sheet india- 
tubber, and by pressing and relaxing it, the liquid is drawn in, 
and by pressing the same the smallest possible quantity can be 
discharged on the object subject to examination. The tube also 
Serves as a stopper to the phial, for the length of the capillary ex- 
tremity is such that it reaches nearly to the bottom. 
The acids and ammonia used are always diluted to about one 
half their ordinary strength, to prevent any unnecessary Cisen- 
' Sagement of vapors. ; 
_ A moveable stage under many circumstances 1s very conven- 
lent, and I have adopted one of a very simple character, and quite 
equal to any of those where the motion is prod y Screws or 
strument, and an eight of an inch thick, witha hole in the centre 
of nearly an inch diameter. This is laid in the stage of the in- 
strument, the glass sustaining the object placed on it, and when 
