32 THE MICROSCOPE 



for a few hours, and then removed to absolute alcohol. After the 

 lapse of a few more hours, pour off the spirit, and add Oil of 

 Cloves or Cajuput. The latter is quite equal to, and much cheaper 

 than Clove Oil ; Creosote and Turpentine may be used if pre- 

 ferred. From this the object may be placed upon a clean slide, 

 and any surrounding oil should be absorbed by the hand or 

 blotting or filter-paper; a drop of Balsam and Benzole being 

 then put upon it. The slide may be left for a few seconds, 

 and then a warmed cover-glass placed upon it (which must 

 be held in position by a wire clip), and the operation of 

 mounting is so far complete. The slide now requires deposit- 

 ing in a warm place for a few days before the later finishing 

 touches can be applied to it. If it be Polycistina, Foraminifera, 

 Sponge or Gorgonia spicules, etc., or any such object that it is 

 wished to mount, a thin smear of gum should be placed on one 

 side of the centre of the slip, when, if the thumb be drawn firmly 

 over the slide, a very thin, almost invisible film will remain, which 

 must be allowed to dry. If then a small heap of the dry material 

 be put on the centre of the smear, and the slide, while held in the 

 fingers at one end, be gently tapped on the other by the forceps, 

 or anything hard that happens to be handy, the material will be 

 seen to spread itself over the gummed surface, and its disposal 

 may, with a little practice, be greatly controlled. The slide now 

 requires breathing upon, and when again dry a drop of the Balsam 

 and Benzole must be put over the object, a warmed cover-glass 

 placed in position, and held with a wire clip. The slide should be 

 gently heated over a spirit-lamp until the medium just begins to 

 boil, when it must be quickly removed to a moderately cool spot. 

 This boiling has the effect of driving out the air from in or around 

 an object, and should any bubbles appear about the slide, they will 

 almost invariably disappear if the slide is left in a warm place. 



In mounting starches in Dammar, for polariscope, a similar plan 

 may be adopted to spread the material ; but in this case no gum is 

 required, the breath upon the slide being enough to hold the gran- 

 ules as they move over the slide. When the breath has evapo- 

 rated, it is not advisable at once to drop on the Dammar, but, first 

 placing over the starch a clean cover-glass, put at each edge of the 

 cover, but not exactly opposite, a drop of Dammar, which, run- 



