TUBE-CELLS. METALLIC PJXG-CELLS. 



229 



faces of these rings to the desired thinness, and then cementing 

 them to the glass-slides "with marine-glue. Not only may round 

 cells (Fig. 106, a, b) of any diameter and any depth that the Mi- 

 croscopist can possibly require* be made by this simple method, 

 but oval, square-shaped, or oblong cells (c, d) are now made of the 

 forms and sizes that he is most likely to want, by flattening the 

 round glass-tube whilst hot, or by blowing it within a mould. — 

 Instead of sections of Glass Tubes, it is less costly, and not in other 



Fig. 105. 



Plate-Glass Cells. 



respects disadvantageous, to employ Metallic Rings, which being 

 cemented to Glass-slides in the usual way, form Cells fitted to re° 

 tain any liquids which do not act chemically upon them. After a 

 trial of different metals, Tin has been found most suitable ; and 

 rings of several different sizes and thicknesses are now made of 

 this metal for the use of the Microscopist. They are even prefer- 

 able to rings of glass in this respect, that a perfectly flat surface 

 may be given to them by slight friction with water on a TVater-of- 



< * The Author has employed gigantic cells of this construction, 10 inches 

 in diameter and li inch deep, for the preservation of Star-fish in 

 Glycerine ; but for such purposes he is disposed to think that rings of 

 Porcelain, which might be made at a much less cost, would be equally 

 effective. 



