46 PREPARATION AND MOUNTING 



made by dissolving gum dammar in benzole, and adding 

 about one-third of gold size : it dries verj readily, and is 

 specially useful when mounting objects in fluid, taking care 

 that no moisture extends beyond the covering glass, which 

 would prevent the complete adhesion of the cement. In 

 those cases where glycerine is employed as the mounting 

 medium, a ring of liquid glue put round the cover first, and 

 when that is dry, a second coat of gum dammar will keep 

 the cover very secure, and no leakage take place. 



LIQUID GLUE is another of these cements, which is made 

 by dissolving gum shellac in naphtha in such quantity that 

 it may be of the required consistency. This cement appears 

 to me almost worthless in ordinary work, as its adherence 

 can never be relied upon ; but it is so often used and recom- 

 mended that an enumeration of cements might be deemed 

 incomplete without it. Even when employed simply for 

 varnishing the outside of the glass covers, for appearance's 

 sake alone, it invariably chips. Where, however, oil is used 

 as a preservative liquid, it serves very well to attach the 

 thin glass ; but when this is accomplished, another varnish 

 less liable to chip must always be laid upon it. (See 

 Chapter Y.) Yet it makes excellent cells. 



BLACK JAPAN. This is prepared from oil of turpentine, 

 linseed oil, amber, gum anime, and asphalt. It is trouble- 

 some to make, and therefore it is much better to procure it 

 at the shops. It is a really good cement, and serves very 

 well to make shallow cells for liquids, as will be described in 

 Chapter IV. The finished cell should be exposed for a 

 short time to the heat of what is usually termed a " cool 

 oven." This renders it very durable, and many very careful 

 manipulators use it for their preparations. 



ELECTRICAL CEMENT. This will be found very good for 

 some purposes hereinafter described. To make it, melt 

 together 



5 parts of resin. 



1 beeswax. 



1 red ochre 



