MOUNTING AND PRESERVING OBJECTS. 59 



of fluid, which can be removed by strips of blotting-paper. 

 Then cement the edges of the cover to the bottom glass. Care 

 must be taken to exclude all air- bubbles from between the 

 glasses. Objects mounted thus do not keep long, and it is 

 best to make a thicker cell. This may be made by painting a 

 round or square ring on the slip with some sort of cement 

 which will not be acted upon by the fluid employed. White 

 lead worked with 1 part linseed oil and 3 of spirits of turpen- 

 tine is well adapted for this purpose. In this ring, the fluid 

 and object are placed and the cover put on. 



Pieces are also cut off the ends of glass tubes and cemented 

 on the slips with marine glue, so as to form very neat cells. A 

 square piece of glass, with a hole drilled in it, cemented on 

 the slip, forms an excellent cell. Such cells, ready prepared, 

 are imported and kept by McAllister & Co., Chestnut Street 

 above Second, Philadelphia ; together with slips, thin glass for 

 covers, mounted preparations, a good variety of instruments 

 themselves, and other things interesting or useful to the micro- 

 scopist. 



Holes may be drilled in square pieces of glass, when a num- 

 ber of them are cemented together with marine glue, by means 

 of a copper tube (or drill) on a lathe, which is used with fine 

 sand or emery and water. This form of cell, as well as the 

 built-up cell, as it is called (which is a glass box, the edges of 

 whose sides are cemented with marine glue), was first contrived 

 by Dr. Goadby. 



Pieces of gutta-percha tubes, cemented on to the slips by 

 heat, may sometimes be used for cells, and answer a good pur- 

 pose. Excellent cells may be made by using narrow slips of 

 glass for the sides, cementing them with marine glue: They 

 are oblong or square, and are well suited for the larger class of 

 objects. 



The thin glass cell, which is made by cutting or drilling a 



