2/4 PRACTICAL MICROSCOPY. 



nation. All kinds are generally fairly clean when received 

 from the dealer, but must, nevertheless, be beautifully 

 polished before any object can be mounted upon them. 

 The thorough cleansing of the glass is an important step, 

 as the slightest film of grease is a preventive of perfect 

 adhesion of any varnish or cement which may be subse- 

 quently used. Ammonia has the power of converting 

 grease into soap, and spirits of wine will dissolve the two, 

 and as some kinds of dirt require friction to remove, the 

 following is perhaps the best formula for a mixture for 

 cleaning slides : 



Liquid ammonia (sp. gr. '880) 10 drops. 



Methylated spirit 2 oz. 



Water oz. 



Rouge, sufficient to make a thin cream. 



Rose-wood slips, also 3 inches long by I broad, are 

 also used for mounting objects, either with sunk cells or 

 with holes bored right through ; but the student will find, 

 perhaps only after a valuable series has been spoiled, that 

 wooden slides possess no advantages over those of glass, 

 and have very many objectionable qualities. 



FIG, 224. 



In mounting objects, a slide-centerer should be employed, 

 in order to make the finish as presentable as possible, as it 

 will generally be found that a slovenly finish means a bad 

 preparation, though this is by no means always the case. 

 The most simple form of centerer is shown in Fig. 224, 



