16 MOUNTING. 



been mounted for some time, the liquid creeps be- 

 tween the cement and the slide or cover, at some spot, 

 and evaporates ; and if the cement be not quite hard, 

 the inner and more liquid portion of it runs into the 

 cell, and spoils the object. A solution, containing a 

 grain of salt and a grain of alum to the ounce of dis- 

 tilled water, is as good as any other ; or simply distilled 

 water in which a piece of camphor has been kept. 

 In use, the cell is first formed by making a circle or 

 outline square on the slide with black japan, and 

 heating this carefully until it becomes solid when cold. 

 The object is then laid in the cell, the liquid added, 

 and the cover applied, any excess being removed with 

 blotting-paper. The cell is to be closed with old 

 black japan or gold-size, applied round the margins 

 of the cover with a hair pencil. A second and a third 

 layer of the varnish may be applied upon the first, 

 when it has become hard outside. Although black 

 japan and gold-size are generally used for the cement, 

 I prefer that mentioned below. 



When large preparations are mounted in liquid, 

 the cell-walls are either formed of glass rings, or 

 they are built up with four oblong pieces of glass, 

 cemented to the slide and to each other with marine 

 glue. A very good preservative liquid for large spe- 

 cimens is a solution of chloride of zinc, in the pro- 

 portion of 20 grains to the ounce of distilled water. 

 A mixture of spirit of wine and water, in the propor- 

 tion of 1 part to 2, or 1 to 4, is often used for the 

 same purpose. 



When preparations are mounted, the cement and 

 the adjacent parts of the slide and cover should be 

 coated with a solution of sealing-wax in spirit, which 

 hardens the exterior of the cement. 



The cement above alluded to is made by melting 

 together 5 parts of rosin, 2 parts of balsam, 1 part of 

 bees' -wax, and 1 of red ochre. The cement is best 

 kept in a little metallic cup, and melted over a spirit- 



