Sxperments on the Blow -Pipe. 35 



ihat when the pipe was (luck in the neck of the bottle previoufly filled with water, the 

 %phole could be inverted without any portion running out, though, from the fize of the 

 notch, a flight agitation was fuIHcient to produce that event. In this fituation the mouth 

 was applied to the blow-pipe, and the air llrongly blown into the bottle. The water im- 

 mediately flowed out, that is to fay, in eighteen feconds. The experiment was twice re- 

 peated, and the aperture of the nozlc of the blow-pipe was -^Vth of an inch. Hence it 

 follows, that the quantity of air emitted from the blow-pipe was not quite one cubic inch 

 in a fecond. For it was 17^ cubic inches in eighteen feconds. It will appear alfo from 

 an eafy calculation, that the velocity was not quite four feet in a fecond. 



The nozle ufed in the foregoing experiment was adapted to the flame of a lamp : but 

 it was too large for the flame of the candle called a fliort eight, which is of tallow, nine 

 inches long, three qrs. inch in diameter, having (Ixteen yarns of cotton in its wick, and 

 weighing 4th part of a pound avoirdupois. The experiments were repeated with a nozle well 

 fuited to the flame of this candle. The aperture of this laft was rather more tban j'^th of 

 an inch in diameter. The bottle was emptied once in 20 feconds, and twice with uncom- 

 fortable exertion in 18 feconds each time. If Ae velocity of emiflion had been the fame 

 in both experiments, this laft would have required about 36 feconds. It may therefore be 

 inferred, that in the experiment with the largeft aperture, the efcape of air was fo fpeedy 

 as confiderably to diminifh the preflurc by wl^ch it was driven out. 



In order to afcertain the condenfation of the air in the blow-pipe, a fmall quantity of 

 water was put into the bottle, and the blowing continued for a few feconds beneath the 

 thumb, which was applied to the orifice of the neck. Air was fufFered to efcape at the 

 fame time through the lips, fo as nearly to produce the fame efi^eft vvith regard to the 

 mufcles of the mouth, as if the fame had been emitted through a blow-pipe. When the 

 aclion was at its utmoft, the thumb was fuddenly clofed on the aperture, and the bottle 

 inverted. In this fituation the line of the upper furface of the water was carefully marked, 

 after which the thumb was gently withdrawn, and a portion of the water flowed out in 

 confequence of the fprlng of the included air. By the depreflion of the water, it was 

 found that the air had been condenfcd by about ^th part of the whole, and confequently 

 would have fuftained a little more than an inch of mercury in a fimple gage. It feemed 

 probable, however, that the exertion of blowing into a bottle by a fliort temporary effort, 

 might be very different from the fteady aftion of blowing through a pipe. To prove this 

 more clearly, I bended a glafs tube nearly of the fame internal diameter as the blow-pipe 

 into a fyphon, the legs of which formed an angle of about 45 degrees of each other. Into 

 this, mercurywas poured to occupy feveral inches in length, and the tube was fixed fo that 

 one of its legs continued vertical, while the other was acceffible to the mouth. Upon 

 blowing into the latter orifice, it was found that, by an eafy or moderate a£lion, the mer- 

 cury was fuftained to the height of about -,*oths of an inch above its level ; that when the 

 preflTure was ftrong, the height was about half an inch ; and that it was pofTible, by very 

 ftrong exertion, to keep the mercury at one inch : but the lips foon became tired. The 

 mercury might indeed be urged to near two inches, but not in a way that could have been 

 maintained for even an extremely fhort time in a<5tual work. 



From thefe fa£ts, if we take half an inch for the medium ftation of the gage, the preflurc 



F 2 for 



