80 The Microscope. 



some other cement, it adds an attractive finishing touch. It is 

 perfectl}^ transparent and usually almost colorless; that which I 

 now have, however, has become a dark reddish brown, although 

 it has been kept in the dark. When drj^ this is also slightly 

 colored. It maj' be used to fasten the cover in place over a 

 mount in glj'cerine, as I have several times done, 3'^et it is rather 

 more trustworthy when added over a ring of shellac or other ce- 

 ment to give a glossy transparent surface, and to add its little 

 quota of strength to the cell. Even when used alone to fasten 

 down the cover, when the cell has been made of some other ma- 

 terial, it has little tendency to run under, especially if only a 

 small drop be used at a time. It dries rapidly, and almost any 

 number of applications may be made in somewhat rapid succes- 

 sion. The reader should be told, however, that too much fric- 

 tion of the brush is likely to give the finished ring a milk}', semi- 

 opaque appearance. With care it is capable of doing good work, 

 and is to be commended. The microscopist cannot readily make 

 it himself, but must buy it of the dealers. 



After using this cement the brush should be cleaned with gas- 

 oline rather than with alcohol. The latter will produce a whitish, 

 curdy deposit that is not easy to remove. 



GOLD SIZE. 



This is a liquid cement used chiefly for building up cells, and 

 for attaching metal rings or other objects of the kind to glass. 

 It dries with exceeding great slowness,but is highly commended 

 by some microscopists, although it is not now very generally 

 used, the slowness with which it dries being one objection to it. 

 But when once its volatile parts have evaporated the remaining 

 product is said to have wonderful tenacity. I have never used 

 it; my report is therefore dependent upon the experience of 

 others. It is made by taking 



Linseed oil, 35 ounces ; 



Red lead, 1 ounce; 



Powdered white lead and 3^ellow ochre, of each a suflTicient 

 quantity. 



Boil the oil and red lead together carefully for three hours ; 

 pour off the clear liquid and boil with a mixture of equal parts 

 of the white lead and yellow ochre added in small successive 

 portions. Let it stand and pour off the clear liquid^for use. 



