42 OBJECTS AND THEIR MOUNTING. 



into any details concerning the natural history of the objects described 

 or named. 



32. TRANSPARENT OBJECTS. The general method of preserving 

 these objects in a dried state, is between very thin plates of talc or 

 mica fitted into cells formed in ivory sliders, having a split ring of 

 wire to secure them, 



as in the following 

 outline, (tig. 30.) 

 The bottom of the 

 cells should be turn- 

 ed quite flat to Fi S- 30 - 

 afford a good bearing for the mica, and of sufficient thinness to 

 permit the magnifiers to approach the object. In using these sliders? 

 like everything else, there is a wrong and a right side, which must be 

 observed, or the student will not be able to approach close enough to 

 the object with the high powers. The ring side should always be 

 placed downwards, or from the microscope, and the other side next 

 the eye or instrument. The softness of mica prevents its being 

 cleaned like glass ; it should therefore be kept as free as possible from 

 dust, and only brushed lightly with a camel's hair pencil when neces- 

 sary, and never touched by the fingers. Generally speaking, four, 

 six. or even a greater number of cells are formed in each slider. 

 When test objects are to be mounted in this way, only one or two 

 cells should be made in each slider, which will lessen their liability to 

 injury. 



33. Another and an excellent method of mounting transparent 

 objects is on slips of glass. A. number of slips of glass of an uniform 

 size should be procured, so that they can be fitted into a cabinet or 

 otherwise. The dimensions to be employed are of course arbitrary ; 

 but it will be generally found, that the three following sizes are the 

 most useful : the first, 3-inches long and f of an inch wide j the 

 second, for smaller objects, 2-inches long and | of an inch wide ; and 

 the third, 1^ inches long and a quarter wide. The two first, when 

 used for transparent objects, have a slip of paper pasted on one side 

 with an aperture about one-third from the end ; in the centre of 

 which, beneath a plate of talc, the object is to be placed. It is better 



