16 H. Goadby on making wet Preparations of Animal Substances. 
surface of the lower glass, around the top one, be made guite dry, 
when. the following cement must be applied to the clean, dry 
glasses, to shut in the fluid, and render the preparation permanent. 
Take Egyptian asphaltum and dissolve it in camphene to the 
consistence of a thick paste; this process is greatly facilitated by 
the application of moderate heat. Keep it in a well secured ves- 
sel, and label it. Then take japanner’s gold size, which may 
be obtained at the varnish makers, but generally it is too thin, — 
because new. Iuspissate it by the continued application of heat 
until it acquire the consistence of molasses, then with a muller, 
upon a marble slab, grind up with the gold-size as much lamp- 
black as you can, until you have formed a very stiff paste; this — 
should also be well secured and labelled. The properties of — 
these ingredients are as follows: 
Asphaltum is hard and brittle. 
Gold-size is highly tough, and elastic, and retains these proper- 
ties for many years. y combining elements respectively too — 
hard, and too soft, the one is made to counteract the objectiona- 
ble properties of the other, and the lamp-black not only assists to 
give good consistence to the whole, but is desirable from its in- 
destructibility. 2 
Japanner’s gold-size is composed of boiled linseed oil, dry red 1 
lead, litharge, copperas, gum animi, and turpentine. 
o use the cement, take equal parts of each of the above ma- 
terials, taking care that the gold-size composition should rather 
ponderate over the asphaltum, than the contrary ; mix them 
intimately on a slab with a small palette knife; if too thick to 
work well, add a few drops of camphene, but beware of making 
tt too thin. Apply the cement, thus made, to the outer margin 
of the top glass; do not use too much for the first coat, but 
rather by successive layers, applied at different periods, fill with 
cement the space between the lower and upper glasses of the 
preparation, until a good solid layer be formed, when the process is 
complete. It is, however, most important ¢o tsolate the several lay- 
ers of the “ black” cement, for the turpentine contained ina newly 
applied coating will act upon, and partially dissolve, the old and 
dry layer; in this case, the upper surface being exposed to the 
atmosphere will speedily dry and contract, and acting upon the 
softened cement below the surface, will drive it between the 
glasses, and spoil the preparation. 
Hither of the following compositions may be used for the pur- _ 
pose of separating the layers of the black cement. 
Gum arabic, ‘ : ‘ : . 3 drams. 
Sugar, . : ; do. 
Corrosive snblimate, 
Pasa oe 1 grain. 
Water, sufficient to make a thick mucilage. | 
