OF MICROSCOPIC OBJECTS. 57 
cell or wall is upon the slide, this is quite necessary, 
otherwise the varnish will be 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. (Chapter V.): 
here gum dammar solution laid on in a very thin coating 
will be found most useful, as it dries so rapidly that it cannot 
run in unless Jaid on with an unsparing hand. 
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 II. 
When the slide is thus far advanced, there remains the 
finishing only. Should the student, however, have no 
time to complete his work at once, he may safely leave it at 
this stage until he have 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 dts 
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 ornamental paper 
is then pasted on the “ object” surface of the glass, so that 
the circle shows the object as nearly in the centre as possible, 
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 used there is no necessity for the edges of the 
slide to be ground, as all danger of scratching, &c., is 
obviated by the paper cover. 
Many now use paper covers, about one and a half inch 
long, on the upper side of the slide only, with the centre 
cut out as before, with no other purpose than that of 
hiding the edge of the thin glass where it is united to the slide. 
