USEFUL APPARATUS. 213 
glass “light modifier,” which is secured by a bayonet joint, and 
may also be removed when necessary. 
D is the cooling evaporator, constructed of thin bronzed cop- 
per, and covered by a lid of perforated copper. A layer of thick 
felt is placed inside for saturation. ‘This vessel, filled with water, 
and placed over the shade as soon as the lamp is lighted, at once 
checks the usual accumulation of heat, and its use, during a long 
evening, will prevent an annoyance which is often felt by the 
microscopist. 
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Fig. 42. 
With regard to the light given by this lamp, it may be remarked 
that the reflector, being parabolic, transmits nearly parallel rays, 
which is a great advantage when low powers are used ; at the same 
time, in consequence of more perfect combustion, resulting from 
shape of chimney and arrangement for the ingress of air, an abund- 
ance of light is supplied for the higher powers, and, if necessary, this 
may be concentrated by placing an ordinary stand condenser be- 
fore the tinted glass front. 
We have seen several of these lamps in use, and can testify to 
their coolness during working. 
