[ 346 ] 
Th is method therefore of fweetening ftinking WQterj 
by blowing (bowers of air up through the (linking 
water of fome aguifh places, may be beneficial. 
72. Live fi(h may well be carried feveral miles, 
by blowing now and then fre(h air up through the 
water, without the trouble of changing the water: 
for this ventilation will not only keep the water fweet, 
but alfo enrich it with air, which is nece(Tary for the 
lite of fi(hes j with which air they fupply their blood, 
by breathing the water, thin fpread, between their 
gills i but (linking water will kill fi(h. 
73. I have found, that much of the heating oil 
may be got out of tar-water, by blowing (bowers of 
air up through it when fcalding-hot, for ly or 30 
minutes, the longer the better 3 the lefs volatile, and 
more falutary acid remaining. 
Explanation of the Figures. Plate X. 
Fig.^ I . (popr) a tin or copper air-box, fix inches ^ 
diameter, and an inch and half deep from {p to p.) 
The lid of the box full of holes, one twentieth inch - 
diameter, and about a quarter of an inch diflant 
from each other. 
'\gi kl) 2i nozel foldered to the lid of the air^box, 
into which the tin-pipe {a gikl)\% fixed fo as to 
take in and out j this pipe to be two feet long, 
and fix tenths inch diameter. 
{a b) a bend in the pipe five inches long, to which 
is fafiened the leathern pipe {c c df) fix inches 
long ; to which the nofe of tlae bellows is fixed 
Fig. 2. 
