c GENERAL SUMMARY OF SCIENTIFIC AND 



piece of apparatus; the largest hole might easily be made 

 to receive a tube, for an achromatic condenser or a polari- 

 scope." 



Cements, Staining Fluids, and Cells. A cement possessing 

 the advantage that it can be used under water, or weak spir- 

 it, so that the cover can be affixed under the surface of the 

 fluid, is highly spoken of by Mr. George Busk. It is termed 

 " caoutchouc size," and is prepared by melting pieces of 

 caoutchouc in a cup until it is reduced to a viscid tar, which 

 is to be dissolved in benzine to the consistency of thick gold- 

 size. When spread over the edges of the cell, it should be 

 allowed to dry for a quarter or half an hour, until the ben- 

 zine has evaporated. The cell with its contents may then be 

 wholly immersed, and the cover applied and pressed firmly 

 in its place ; all air-bubbles are thus avoided. When the sur- 

 faces are dry, a solution of shellac, or other varnish, will com- 

 plete the mounting. 



Mr. T. Charters White recommends to the Queckett Club 

 a cement consisting of four or five parts of common yellow 

 beeswax, melted with one part of Canada balsam; it is ap- 

 plied melted, on a hot wire, after the manner of soldering ; 

 sets as soon as cool, and hence can not run in under the cover, 

 however thin the cell may be ; and can be instantly loosened 

 by warming, if the cell is to be repaired or the object dis- 

 mounted. 



Mr. Henry F. Hailes contributed to the Queckett Club a 

 valuable application of the sand-blast process. It occurred 

 to him that this process might be employed to sink cells in 

 glass slips for microscopic mounting ; and they are now to 

 be had for this purpose. They can be sunk of any desired 

 size or shape; and although the surfaces are rough, or ground, 

 this is not a disadvantage. For opaque objects it forms an 

 agreeable background ; and for objects in balsam, since the 

 refractive power of this medium is so near that of glass, it 

 disappears. These cells are particularly available for Fora- 

 minifera. 



The following method is recommended as a remedy for 

 the uncertainty that exists in the conservation of such ob- 

 jects as are usually mounted in cells with fluid. 



Soak a few pieces of gelatine in water for about twelve 

 hours. Having cleaned the glass slip, place a small piece 



