MOHR AND REDWOOD'S PRACTICAL PHARMACY. 123 
in fig. 15. This would prevent the escape of steam under 
ordinary circumstances, and would act as a safety-valve by 
Fig. 15. 
allowing it to escape, if unusual pressure were applied, 
while at the same time it might be used as a water bath for 
the reception of an evaporating dish. The water joint 
would be inapplicable, however, if the steam were required 
to be used under more than a very slight pressure. It 
would be the most simple and inexpensive way of fitting 
the boiler, but tight joints and a proper safety-valve would 
render it more completely and generally useful, and would 
be necessary for some of the applications we are about to 
notice. The ash-pit door should be made to fit as close as 
possible, so that the admission of air here may be shut off 
at pleasure. The furnace door should be close to the top 
plate, as shown in the drawing; and there should be a small 
opening B, immediately over the furnace bars, to admit of 
the clearing of the bars with a poker, of sending a blast of 
air into the fire from a bellows or blowing machine, of in- 
troducing a tube into the fire, warming a plaster spatula, 
&c. Between the drying closet and the ash-pit, there is a 
communication which may be opened or closed by means 
of the sliding door or damper G, and at M, there is an air- 
channel passing round the back of the fire and under the 
boiler to the drying closet. The course of this air-channel 
is further shown in fig. 16 at F. When the furnace is in 
action, if the ash-pit door be shut, and the damper G drawn 
out, the air supplied to the fire will be necessarily drawn from 
the drying closet, while fresh air, warmed by its proximity 
to the fire, will at the same time enter the closet through 
the channel M. A constant current of warm dry air will 
thus be maintained through the drying closet, which will 
render it very efficient for the purposes to which it is ap. 
