BAGATELLES RELATING TO THE PNEUMATIC APPARATUS. £ 



any gas is immediately transferred from the difengaging veffel 

 to the gazometer; for if the apparatus be fufficiently air-tight 

 as it ought to be, and the gas rapidly difengaged, an explo- 

 fion may be occafioned for want of a fufficient paflfage for the 

 gas. 



Fig. 4. The piece c, Fig. 1 . Its companion b ends in a 

 male fcrew to be united to the gazometer. 



Fig. 5. A perfpeclive view of the flop-cock, the above enu- 

 merated parts being put together. 



Fig. 6. A nut provided with a female fcrew foldered to the 

 gazometer, by means of which the flop-cock may be applied 

 or removed as ufual. 



Fig. 7. reprefents two brafs cylinders. One end /is fitted 

 by grinding to the orifice of the flop-cock ; and to the other 

 ends g and h 3 between x, is faflened a flexible tube for expe- 

 riments with the blow-pipe. 



This flexible tube was made by twifling a brafs-wire fpi- Cheap and very 

 rally round a long thin cylinder, covering this with oiled filk u <fful flexible 

 twice wrapped round, and faflened by means of thread between ga f e s. 

 the grooves of the wire. It was then again varnifhed and co- 

 vered in a fpiral manner with flieep-gut flit longitudinally, and 

 again fecured with thread. Laflly, to protect the whole from 

 external injury, it was covered with leather in the fame man- 

 ner as the tubes of the inhalers. Thefe flexible tubes anfwer the 

 fame purpofe as the very coflly ones made of elaflic gum, fi- 

 milar to the hollow bougies made for furgeons. 



Fig. 8. A (broken) blowpipe, put in this place merely to 

 fhew how its end k is connected with the gazometer, by fitting 

 into the end (f) of the brafs end of the flexible tube. 



§ 2. In pneumatic experiments for transferring any gas, for Defcriptkm of a 

 inflance oxigen, from the air-holder to another veffel, it is j 01 "' for meta l lic 

 frequently neceflary to have tubes which can be joined in cer- 

 tain directions and inclinations ; and for this purpofe a con- 

 trivance has been adopted, which is well known, and is re- 

 presented Fig. 1. Plate II. where a and b are fpherical feg- 

 ments, and c their junction by means of a fcrew. But as this 

 apparatus, befides that its parts are with difficulty well ground 

 together, is liable to become imperfect, more efpecially by 

 flrong preffure, or a blow received on the edges of the feg- 

 ments, or a grain of dufly fand interpofed between the frnall 

 flat furfaces, the writer of thefe trifles has contrived another, a better con- 

 delineated fcnafao. 



