THE ROYAL ARTILLERY INSTITUTION. 
Ill 
The question of the best method of drying powder has received some 
attention of late at Waltham Abbey, and in order to gain some information 
to aid in the construction of a new stove, an experimental stove was built of 
8 ft. square internal floor and about 10 ft. high. Colonel Younghusband 
wished to have the hot air pass from above downwards, as that is evidently 
the best method of drying, and is used in some places where drying is carried 
on—as at Enfield Lock, for drying wooden stocks. In the stoves in ordinary 
use at Waltham Abbey it is found that the powder sweats very much during 
the first 10 or 12 hours, and evidently that there is not sufficient circulation 
to carry off the moisture. The hot moist air seems at first to rise and get 
heavy with moisture, and then come down again to the bottom of the stove, 
circulating only in the stove itself. 
But if the hot air come in at the top and descend, it has no tendency to 
rise again, as it absorbs moisture, cools, and becomes heavy. Evidently also 
pebble-powder gives special facilities for drying, as the large interstices can 
be used for making the current of heated air pass through the powder. 
The plan adopted, therefore, was to make the current pass down through a 
thick layer of the powder, which for this purpose was placed in bins. No 
other passage was allowed for the air. An idea of this stove will be obtained 
from the following figure :— 
Fig. 12. Scale 
C 
It will be observed that the pipes have been placed underneath the stove. 
The object of this is to ensure circulation. Hot air tends always to rise, as 
water tends to fall. But as water will always when confined in any case rise 
to its original level, so the author conceived hot air when confined to a 
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