\\VVU THE MICROSCOPE. C>1 



lit. Marine Glue Cells may be made according to the same plan. 

 In order to make such a cell, a glass slide is warmed upon the brass 

 phte, 72, and when hot enough a small piece is allowed to melt 

 upon the slide, and moved round and round in the position in which 

 the wall of the cell is to be. When the glue has been allowed to 

 cool, any superfluity may be removed from the slide with a sharp 

 knife. The surface may be made level by rubbing it gently upon a 

 piece of emery paper laid on a plate glass or other perfectly flat 

 surface. 



118. Cells made of Tinfoil. A piece of tinfoil may be cut out, 

 so as to form a slightly thicker cell, and may be fixed upon the slide 

 with marine glue, as in fig. 102, pi. XVII. Tin cells are now made of 

 every thickness by Mr. Collins, Titchfield Street. They form the 

 cheapest kind of cell. 



Of Glass Cells. 



119. Cutting and Grinding Glass. In the manufacture of cells 







presently to be described, glass is required to be cut with a diamond 

 and ground perfectly smooth at the edges. Moderately thick glass 

 is cut with the ordinary glazier's diamond, pi. XVI, fig. 92, but 

 when we require to cut plate glass, a larger diamond than that in 

 ordinary use is necessary. 



The thin glass is cut with the writing diamond, pi. XVI, fig. 94, 

 which makes a scratch sufficiently deep to permit of the glass being- 

 broken off very smoothly. The circles of thin glass may be cut by carry- 

 ing the diamond round openings which have been turned in pieces 

 of brass. Of these many different sizes may be made so that circular 

 pieces of thin glass of any required diameter, may be easily cut, 

 fig. 95, pi. XVI. 



120. stone for Grinding. Glass can be ground upon a perfectly 

 fiat stone with emery powder or fine sand and a little water, or, 



instead of the stone, a flat //<?/<? composed of pewter may be used, as 

 was recommended by Dr. Goadby. The emery after a time becomes 

 embedded in the pewter, and thus a very efficient surface for grinding 

 results. 



The pewter plate may be cast in the form of a flat circular disk, 

 which can be placed upon a pivot and made to revolve rapidly in a 

 horizontal direction by means of a multiplying winch connected with 

 it an arrangement which is desirable when it is important to save 

 labour as much as possible. 



121. Of Drilling Holes in Glass. In the construction of many- 

 forms of cells it is necessary to drill holes through thick glass. This 



