4.2, PREPARATION AND MCUNTING 
be steeped in any liquid; and the use of them saves much 
trouble in examining cursorily under the microscope, whether 
the air-bubbles are expelled from insects, &c. &c. They are 
readily cleaned, and serve very well as covers, when turned 
upside down, to protect objects from dust. For this latter 
purpose Dr. Carpenter recommends the use of a number of 
bell-glasses, especially when one object_must be left for a 
time (which often happens) in order that another may be 
proceeded with. Wine-glasses, when the legs are broken, 
may thus be rendered very useful. 
As heat is necessary in mounting many obejects, a lamp 
will be required. Where gas is used, the small lamp known 
as “ Bunsen’s” is the most convenient and inexpensive. It 
gives great heat, is free from smoke, and is readily affixed 
to the common gas-burner by a few feet of india-rubber 
tubing. The light from these lamps is small, but this is 
little or no drawback to their use. Where gas is not avail- 
able, the common spirit-lamps may be used, as they are very 
clean and answer every purpose. 
In applying the required heat to the slides, covers, &c., it 
is necessary in all cases to ensure uniformity, otherwise 
there is danger of the glass being broken. For this purpose 
a brass plate at least three inches wide, somewhat longer, 
and one-eighth of an inch thick must be procured. It 
should then be affixed to a stand, so that it may be readily 
moved higher or lower, in order that the distance from the 
lamp may be changed at will, and thus the degree of heat 
more easily regulated. This has also the advantage of 
enabling the operator to allow his slides, &c., to cool more 
gradually, which, in some cases, is absolutely necessary,— 
as in fusing some of the salts, &c. | 
In order to get rid of air-bubbles, which are frequently 
disagreeable enemies to the mounter of objects, an air-pump 
is often very useful. This is made by covering a circular 
plate of metal with a bell-glass, both of which are ground so 
finely at the edges that greasing the place of contact renders 
it air-tight. The pump is then joined to the metal plate 
