42 PREPARATION AND Me UNTING 



be steeped in any liquid ; and th.e 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 knowin 

 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 



