274 MANIPULATION. 



CHAPTER IV. 



ON CEMENTS. 



The cements employed to fasten down the covers of cells and 

 boxes for containing microscopical preparations mounted in 

 fluid, are of many kinds, the most useful of them being as 

 follows : — 



Japanneri Gold- Size. — This consists of a mixture of boiled 

 linseed-oil, dry red-lead, litharge, copperas, gum animi, and 

 turpentine; the first ajid last ingredients being its principal 

 constituents, it can be purchased at most shops where varnishes 

 are sold, but, as its drying properties increase with its age, it 

 is necessary that it be two or three years old before it is 

 employed. It should be laid on with a camel or sable-hair 

 pencil, and be kept in a wide-mouthed or other vial, closely 

 corked. A thin coating should be laid on at first, and when 

 this is dry another rather thicker. If the gold-size be very 

 thin, a small quantity of lamp-black or litharge may be mixed 

 with it on a slab by means of a palette knife, and as this 

 mixture very soon dries it should be used quickly. The brush 

 employed with either of the above cements may be cleaned 

 with turpentine. 



Sealing-wax Varnish. — This is made by dissolving sealing- 

 wax of any colour in alcohol, it having previously been broken 

 into small pieces. This cement is not so good as the gold-size, 

 in consequence of not sticking readily to damp surfaces, but 

 it forms an excellent material for giving a shiny coloured 

 coating as a finish to the mounting of an object. It is laid on 

 with a small brush, and should be tightly corked to prevent 

 the spirit from evaporating ; the brush may be cleaned with 

 alcohol. Some persons prefer shell-lac to sealing-wax for a 

 cement, but it wUl be found rather too brittle ; the method 

 of using and keeping it is the same as in the case of the seal- 

 ing-wax. 



