288 MANIPULATION. 



together on a slab and laid on the slide as soon as possible, as 

 this mixture quickly becomes hard. In the second, where 

 deeper cells are necessary, marine-glue is used : this must be 

 melted and dropped upon the slip of glass, and flattened when 

 warm with a piece of wet glass, and what is superfluous cut 

 away with a knife, so as to leave only the walls of the cell ; 

 these, if they have become loosened, may be made firm again 

 by warming the under surface of the slip of glass. The sur- 

 faces of these cells may be made flat by rubbing them on the 

 metal plate with emery and water. The plan of laying down 

 and of cementing the thin cover is the same as that for the 

 flat and other cells before described. 



Mr. Topping prepares cells for receiving minute prepara- 

 tions in the following manner : — He takes a slip of glass and 

 lays on it two thin pieces of mahogany of the size of the glass ; 

 each has a hole of the required figure cut in the centre ; in 

 one piece the hole is the size of the outer margin of the cell, 

 in the other of the inner margin. These, when laid over the 

 glass, afford the means of marking out with a writing diamond 

 the space to be occupied by the cell, which must be filled up 

 with black japan. The glass is now to be transferred to an 

 oven, the heat of which should be raised gradually to prevent 

 the japan from blistering, and if care be taken in this part of 

 the process, a cell so made will resist the action of proof spirit. 

 For the construction of cells for mounting objects in fluid, the 

 following very simple and efficacious method is adopted by 

 Mr. G. Shadbolt, having the threefold advantages of neatness, 

 rapidity of execution, and great economy. 



It frequently happens that it is desirable to preserve in fluid 

 an object of such extreme thinness, that even the thin glass 

 cell is too thick, such as the cuticles of some vegetable pre- 

 parations, desmidieae, &c. To make cells adapted for such pur- 

 poses, and others somewhat thicker, as a complete substitute 

 for thin glass cells, a little instrument contrived by Mr. Shad- 

 bolt, and shown at fig. 182, will be found highly useful. It 

 consists of a piece of weU -seasoned mahogany or other wood, 

 about an inch in thickness and of about 9 inches by 3^. To 

 this are attached two flat mahogany wheels, a a, both | inch 



