78 



THE MICROSCOPE. 



to exclude any excess of fluid, which remove with strips of blotting- 

 paper, being careful to do all this with a light hand, that small bubbles 

 of air may not insinuate themselves to replace any lost fluid: air- 

 bubbles are at all times unsightly, and liable to spoil an object when 

 allowed to remain. Lastly, cement the edges of the cover to the bottom 

 glass with japanners' gold-size, or sealing-wax varnish, carefully 

 drawn around the edges with a camels'-hair pencil. Mr. John 

 Gorham has lately proposed the use of a " Brass cementing 

 Pencil,'" 1 fig. 62. It is a brass tube, six inches long, with a 

 conical bore, having a lid to screw on. A small portion of the 

 cement crumbled into fragments is shot into the tube, which is 

 then ready for use. In using this instrument, the extremity is 

 gently heated in the flame of a spirit-lamp; and when the cement 

 begins to ooze out, holding the pencil like a pen, the point is 

 traced along each side of the cover, leaving a line of cement in 

 the angle. It is thus laid on much easier than with ^a brush, 

 and after a little manipulation, it will be found that the point 

 will suffice to polish off, instead of using the flattened wire. 

 The cement recommended by Mr. Quekett for cementing deep 

 cells is made by melting together two ounces of black resin, 

 one ounce of bees'-wax, and one of vermilion. Mr. Hett pre- 

 fers dark-coloured and old japanners' gold-size for securing the 

 cells of his beautifully delicate injected preparations.* Mr. 

 Brooke uses Brunswick black, to which has been previously 

 fig ' ' added a little India-rubber dissolved in mineral naphtha, to 

 prevent its cracking when dry. 



Mr. Gorham's drawing and description of a " holder" is similar to 



fig. 63. 



one long used by the author, fig. 63, for the purpose of pressing toge- 

 ther objects mounted in the dry way, and during the drying process, 



* For methods of making various good cements, consult Ure's Dictionary of Arts 

 and Manufactures. 



