132 



The method I have adopted in the employment of Glycerine, is sim- 

 ply to mount the object in the manner it is usually performed when 

 spirit of wine or creosote water is used as a medium, and hav- 

 ing covered the immersed object with the thin glass and removed all 

 excess of liquid, to cement the margin with a coating of shell-lac var- 

 nish ; the one I usually employ consists of the ordinary black sealing- 

 wax dissolved in rectified spirit of wine. Care must be taken during 

 this operation to maintain the slider in a flat position until the varnish 

 has become dry from the evaporation of the spirit, and also until a 

 sufficient number of coatings or layers of the varnish have been 

 applied to render the subject perfectly secure and prevent any 

 escape of the fluid. Gold-size or copal dissolved in oil of lavender 

 may be employed to effect the same purpose, and the second 

 and third coatings may, with advantage, consist of either of these, 

 which yield a tough varnish above the lac, which is otherwise liable to 

 become brittle. The Glycerine may be used in its concentrated 

 treacly state, or it may be diluted with distilled water to any required 

 extent, according to the object of the operator and the subject to be 

 mounted; if there be extremely fine markings on the subject it is bet- 

 ter to add about four or five times its volume of water, as otherwise the 

 thick fluid may prevent these from being so sharply defined as may 

 be desired. I have had a number of slides of Desmidece which have 

 been mounted from four to ten months by this means, and they have 

 kept excellently. The Glycerine may also be used with the addition 

 of a small portion of culinary salt, corrosive sublimate, creosote or spi- 

 rit of wine, if considered desirable. 



While on this subject, I may, perhaps, be allowed to describe 

 shortly to the Society the method I have adopted for using castor oil 

 as a medium for mounting certain classes of objects ; this method was 

 described in a paper, read before the Chemical Society, in January, 

 1844,* entitled 'A means of preserving the Crystals of Salts as per- 

 manent objects for microscopic investigation ;' and as I have been fre- 

 quently questioned on this subject by members of the Microscopical 

 Society, I hope its brief abstract may not be deemed out of place 

 here. 



The object required to be mounted is placed on the slider in 

 its dry state, or deposited wet and allowed to dry, or if in solution, a 

 drop of the liquid is to be placed on the slip of glass and allowed to 

 crystallize by spontaneous evaporation ; in the latter case I prefer 



* • Proceedings and Memoirs of ibe Chemical Society,' vol. ii. p. 71. 



