THE MICROSCOPE. 185 



to do al! our work over again. When the cover appears to be fixed 

 with some firmness, we apply a delicate clip made of spring bras* 

 wire, after this form, y^*^^ which exerts just 



sufficient pressure -__y^*''Sf l^J^ upon the cover to 



hold it in place dur- ^^^====^%, J~^^ ing the necessary 

 washing which must p,^ ,„ spd^Toip. follow ere a further 



application of cement can be made. These clips can be obtained 

 of the opticians very neatly made and nickel plated for a trifling 

 cost. By some, an applicance known as Smith's Mounting Instru- 



FiG. 27. Smith's Mounting Instrument. 



ment is used, but unless very carefully handled is apt to exert too 

 great a pressure upon the thin cover and thus force out the contents 

 of the cell. 



It being absolutely necessary to remove all the superfluous 

 glycerine which has run out upon the slide before beginning to seal 

 up the cell, we must now proceed to wash it off, under a running 

 tap if one is handy, if not, in a basin of water; using the large 

 camel's hair brush and soap freely; finishing with a rinse of 

 pure clean water, and drying thoroughly with a clean soft towel. 

 Then place the slide again on the turn table, and run on a layer of 

 cement; to be followed (when dry) by others, until the desired finish 

 is obtained, either with or without colored rings, as the fancy of the 

 worker may dictate. My own practice for some fifteen years has been 

 to use only the white zinc as a cement; to finish the mounting com- 

 plete with it, and then to finish off with a delicate line of French 

 blue, in the middle of the spotless white of the cell or ring. 



Having mastered the simple cell of cement as above, we next 

 come to those of greater depth, for containing specimens too thick 

 for the former. The simplest and at the same time the most 

 satisfactory of any with which I have worked are made of white 

 sheet wax, in precisely the same manner as those described in the 



