28 The Microscope. 



name of the preparation with a diamond on the glass ; 

 I prefer the little green labels, however, as they help 

 to make the slide easily seen on a table, and I put 

 these on, even if no other piece of green paper is 

 admissible. 



Many objects require special preparation, as flat- 

 tening out, cleaning in ether, etc., before they are 

 placed in the balsam. Some should be immersed for 

 some days in caustic potash, which makes them soft 

 and yielding; and all are rendered more manageable 

 by leaving them awhile to soak in spirit of turpentine 

 before placing them in the balsam. Some prepara- 

 tions will look badly, and even show air-bubbles when 

 first done, and yet some months later, from their more 

 complete hardening perhaps, be found free from de- 

 fects. For this reason it is often worth while to keep 

 apparent failures, consigning them to temporary obli- 

 vion, but scribbling upon them in ink any particulars 

 worth recording. Slides, however, which are evidently 

 hopeless failures can always be cleaned in spirits of 

 turpentine, or in wood-naphtha, which dissolves the 

 balsam very rapidly; and even the thin glasses can 

 again be made available. Turpentine which has been 

 used for cleaning purposes must not be employed in 

 making new slides. And in all plans of mounting it 

 is wise to work methodically, and have all requisites 

 neatly arranged, or various odd matters may show 

 themselves in the field of view with the object, such as 

 fibres of wool, cotton, and flax from table covers and 

 clothes; fibres of feathers from cushions, scales of 

 clothes- moths, etc. 



