OF MICROSCOPIC OBJECTS. 31 



The thin glass, then, is to be united to the slide, so as to form 

 a perfect protection from dust, dampness, or other injurious mat- 

 ter, and yet allow a thoroughly distinct view of the object. This 

 is to be done by applying to the glass slide round the object some 

 adhesive substance, and with the forceps placing the thin glass 

 cover (quite dry and clean) upon it. A gentle pressure round the 

 edge will then ensure a perfect adhesion, and with ordinary care 

 there will be little or no danger of breakage. For this purpose 

 gold-size is frequently used. The asphalt and india-rubber varnish 

 also will be found both durable and serviceable. Whatever 

 cement may be used, it is well to allow it to become in some 

 measure "fixed" and dried; but where no cell or "wall" is upon 

 the slide, this is quite necessary, otherwise the varnish will be al- 

 most certain to extend, as before mentioned, and ruin the object. 

 It may be stated here that gold-size differs greatly in its drying 

 powers, according to its age, mode of preparation, &c. (Chap- 

 ter IV.) 



Should any object be enclosed which requires to be kept flat 

 during the drying of the cement, it will be necessary to use some 

 of the contrivances mentioned in Chapter I. 



When the slide is thus far advanced, there remains the " finish- 

 ing " only. Should the student, however, have no time to com- 

 plete his work at once, he may safely leave it at this stage until 

 he has a number of slides which he may finish at the same time. 

 There are different methods of doing this, some of which may be 

 here described. 



If ornamental papers are preferred, a small circle must be cut 

 out from the centre a little less than the thin glass which covers 

 the object. Another piece of coloured paper is made of the same 

 size, and a similar circle taken from its centre also, or both may 

 be cut at the same time. The slide is then covered round the 

 edges with paper of any plain colour, so that it may extend about 

 one-eighth of an inch over the glass on every side. The orna- 

 mental paper is then pasted on the "object" surface of the glass, 

 so that the circle shows the object as nearly in the centre as pos- 

 sible, and covers the edges of the thin glass. The other coloured 

 paper is then affixed underneath with the circle coinciding with 

 that above. And here I may observe, that when this method is 



