21 G THE MICROSCOPE. 



should be taken to have no draught of air through the 

 room while handling very delicate objects; many a beauti- 

 ful object has been wafted from under the hand of the 

 microscopist in this way, sometimes, even by his own 

 breath. 



The preparation of very minute objects which require 

 particular chemical treatment before mounting, will be 

 more fully described hereafter. To this class belong the 

 diatomaceae, whose delicate structure forms one of the most 

 beautiful objects which can be exhibited. In mounting 

 entomological specimens, the first thing, of course, is the 

 dissection of the insect. This is best accomplished by 

 the aid of Collin s's Dissecting Microscope, a pair of small 

 brass forceps, and very finely-pointed scissors ; the parts 

 to be prepared and mounted should first be carefully 

 detached from the insect with the scissors, then immersed 

 in a solution of caustic alkali (Liquor Potassse) for a few 

 days, to soften and dissolve out the fat and soft parts : the 

 length of time it is necessary to immerse them can only be 

 ascertained by experience, but, as a general rule, the objects 

 assume a certain amount of transparency when they have 

 been long enough in the alkali ; when this is ascertained 

 to be the case, the object is to be placed in a flat receptacle 

 (a shallow pomatum pot is as good a thing as can be used), 

 and put to soak for two or three hours in soft or distilled 

 water. It is then to be placed between two slips of glass, 

 and gently pressed till the softer parts, &c. are removed. 

 These will frequently adhere to the edge of the object ; it 

 will, therefore, be necessary to wash the latter carefully 

 in water to get rid of the superfluous matter, a process 

 which will be much aided by delicate touches of a camel's- 

 hair brush. Place the object now and then under the 

 microscope to see that all extraneous matter is removed, 

 and when this is accomplished take the specimen up care- 

 fully with the camel's-hair brush, and lay it on a piece of 

 very smooth paper (thick ivory note is very good for 

 the purpose), arrange it, if necessary, to its natural appear- 

 ance with the brush and a finely-pointed needle, place a 

 second piece of paper over it, and press it flat between 

 two slips of glass, and compress it by one of the American 

 clips which may be bought for a few pence per dozen. 



