88 PREPARATION AND MOUNTING 



although the whole ring may have been previously wet. The 

 outer edge of the thin glass and cell must now be perfectly dried, 

 and a coating of gold-size applied. When this is dry, the process 

 must be repeated until the cement has body enough to protect 

 the cell from all danger of leakage. When some preservative 

 liquids are used, a scum is frequently found upon the surface when 

 placed in the cell, which must be removed immediately before the* 

 cover is laid upon it. 



I believe this method to be perfectly secure against leakage 

 when carefully performed ; and some of my friends have told 

 me that their experience (some years) has been equally satis- 

 factory. 



In using some of the particular kinds of preservative liquids, it 

 will be found necessary to make slight change in the manipulation. 

 This will be best explained by mentioning a few objects, and the 

 treatment they require. 



For the preservation of the Mosses, Algae, &c., Deane's com- 

 pound is much used, and considered one of the best media. The 

 specimen to be mounted should be immersed in the compound, 

 which must be kept fluid by the vessel containing it being placed 

 in hot water. In this state the whole should be submitted to the 

 action of the air-pump, as it is not an easy matter to get rid of 

 the bubbles which form in and around the objects. The cell and 

 slide must be warmed ; and heat will also be necessary to render 

 the gelatine, &c., fluid enough to flow from the stock-bottle. The 

 cell may then be filled with the compound, and the specimen im- 

 mersed in it. A thin glass cover must then be warmed, or gently 

 breathed upon, and gradually lowered upon the cell, taking care, 

 as with all liquids, that no bubbles are formed by the operation. 

 The cover may be fixed by the aid of gold-size, Japan, or any of 

 the usual varnishes, care being taken, as before, that all the com- 

 pound is removed from the parts to which the varnish is intended 

 to adhere. 



The glycerine jelly of Mr. Lawrance, before mentioned, requires 

 almost a similar treatment. " The objects to be mounted in this 

 medium should be immersed for some time in a mixture of equal 

 parts of glycerine and dilute alcohol (six of water to one of 

 alcohol). The bottle of glycerine jelly must be placed in a cup 



