ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
523 
most appropriate and convenient, but if a dry lens is to be used then 
the objective is surrounded by a conical glass or metal case n, fig. 
61, to the end of which a cover-glass is cemented on. The case is 
adjusted to the objective by packing it on with cotton-wool. For 
Fig. 61. 
Vertical section through the objective, the water vessel g, the slide o, copper 
plate k , and Micioscope-stage b. At e are shown the clamps, but these really lie in a 
different plane. About two-thirds natural size. 
constructing an air-chamber suitable for most purposes, the author 
uses a couj)le of slides with central circular apertures. When these 
two slides are fixed or cemented together, and closed in above and below 
with a cover-glass, a fairly large air-chamber is obtained. If renewal of 
Fig. 62. 
Vertical section through the water-vessel, as in fig. 61, showing the moist 
chamber with air-passaue through z. The glass tube 6, drawn in dotted line, is only 
used when the object is to be inspected through air. About two-thirds natural 
size. 
the air be required, this is obtained in the manner depicted in fig. 62. 
A glass tube z communicates with the air-chamber by means of a 
passage i ground out of the uppermost slide. The tube is protected 
by inverting over it a test-tube. 
2 o 2 
