BROWN, ON MICROSCOPICAL MANIPULATION. 153 



preparing and mounting objects; these are kept in their 

 place by a raised half-inch bead. The circle (at 2) are per- 

 forations to half the thickness of the wood, for the reception 

 of pill-boxes, which contain various sizes of cylinder glass, 

 glass cells, &c, the contents of each box being specified on 

 the outside. At 3 will be seen three separate pieces of 

 coloured paper, pasted upon the board, with the length and 

 breadth of a slide (3x1) traced upon them, as also a circle of 

 half and three-quarter inch, for fixing down the cylinder glass 

 upon the slide after the application of heat. I place it upon 

 the colour that will best show the object, and holding the 

 slide true to the square lines, the thin glass can be applied 

 exactly central by using the circle, as a guide. At 4 are 

 two compresses made of " spring brass," (a description of 

 thin brass, varying in thickness, to be procured from printers, 

 who use it to separate type) . These are for mounting either 

 in balsam or fluid, and both correct centering and permanent 

 compression may be kept up ad libitum. Another species of 

 self-acting compress, and one that 1 have found most useful, 

 is made of the same description of brass, and figured below 

 in the diagram. This is slid on to the end of the glass, 



generally with a thin piece of kid to protect the slide, and 

 by raising the hooked portion it may be dropped upon the 

 thin glass, the amount of pressure dependent upon the 

 thickness of the brass. 



The microscopic cell-plate is a circular plate of brass one 



twelfth of an inch thick, perforated to the diameter of the 



