I40 THE MICROSCOPE. 



other, so that when the ordinary glass sHp is placed upon the plate, 

 with one end in contact with the two strips, this mark is 

 seen exactly in the centre. The slip is held firmly in 

 place, and the white surface of the plate serves ad- 

 mirably as a background upon which to arrange the 

 object. 



At last we seem to be really done with all our pre- 

 liminary work, and ready for mounting. But wait 

 another moment. Though as before stated, the oil 

 of cloves is perfectly miscible with the balsam, and 

 a specimen may be transferred directly from the one 

 to the other, it is a very slow drier, and an object so 

 I -^ mounted might be months in hardening sufficiently 

 to handle, even if the utmost precaution be taken to 

 drain off all the superfluous oil. Fortunately we have 

 Collapsible tube ^^ excellent remedy for this trouble close at hand. 



containing mount- •' 



ing material. Pouring a Small quantity of benzole into a watch 

 glass, we place in it one of the specimens, say a wing, and imme- 

 diately cover it with the small bell glass to exclude dust, and pre- 

 vent the evaporation of the benzole, which is exceedingly volatile. 

 And now at last we are ready for the mounting. 



One of the cleaned slips having been placed upon the mount- 

 ing plate, and its surface dusted off with the brush, a drop of bal- 

 sam of exactly the proper dimensions, is to be placed in its centre, 

 indicated by the mark upon the plate. And here, practice alone 

 mugt be our guide, for the amount must be varied according to the 

 diameter of the covering glass and the thickness of the object. In 

 mounting our present specimens, say with covers of ^8 inch diam- 

 eter, it will be found that more of the balsam will be required to fill 

 up evenly to the edge of the cover, with one of the legs than 

 with a wing. The great aim should be to get exactly the right 

 amount dropped on the slide at first, so that it will fill to the edge 

 of the cover when the latter is pressed down, without any excess 

 exutling, or any additional filling being required. No rule can be 

 given for doing this; only continuous practice can give one the 

 necessary skill; but it is worth trying for, since a mount thus made 

 possesses an artistic appearance, which cannot be equalled by any 

 other means. — Hut to return to our muttons. — The drop of balsam 

 having been placed in the centre of the slide, the wing is taken from 



