21 "Nevii Appllcatitn of the Syphtt. 



IV. 



Supplementary Letter on the Syphon^ to the Communication at page ^47 of the lafl Volumt. 



By Mr. William Close. 



To Mr. NICHOLSON. 

 S I R, 



V. 



ALVES covered with leather may be adapted to the ends of the fmall pipes, and they 

 may be opened by drawing a wire after the external valve has clofed its tube. For this 

 purpofe along fmall pipe muft be fixed into the bottom of A W, (PI. XXIV. Fig. i.) muft rife 

 to near the top of that veflel, and its lower end be immerfed in a veflel of water below the 

 loweft part of the fyphon. The wire muft pafs through this pipe,' and be fixed to one lever 

 within the veflel for raifing the valves, and to another below the bottom of the pipe, con- 

 nefled with the moveable veflels above. When the fecond and fourth veflels afcend, the valves 

 will open, unlefs they are prevented by the weight of water in the fyphon, and water will 

 rife in the fmall wire pipe, but cannot enter the veflel A W. The afcent, however, will 

 extend through a fpace nearly equal to the length of the defcending column in the 

 fyphon. 



A very eafy and extcnfive method of rendering aftive the preflure of the atmofphere is 

 here prefcnted to our notice. The veflel A W may be filled with water through a fmall 

 vertical pipe, without receiving any from the fyphon, to which it need only be connefled 

 by an air pipe. 



By the fame principle water may be raifcd to a confiderable height above the fyphon. 

 To return, however, to our former fubjedt, the water in the pipe will completely prevent 

 the admiflion of air into the receptacle of raifed water: it ferves the purpofe of packing 

 or leathering. 



The water in the vefTel A W, will never reach the higher end of this pipe, becaufe it 

 cannot rife above the air pipe conne£ted with the fyphon. 



If fuch a long pipe (hould be inconvenient, a much fhorter one may be ufed, if its 

 lower end be immerfed in mercury inftead of water; it may then alfo be confiderably wider 

 'than the other, and an iron rod of a rather lefs diameter may be placed within it to pu(h 

 up the valves. If the valve of the water tube be made light, it will open and fhut without 

 any aflfiftance. 



The veflTel A W. fhould not be large ; the top part of it fhould be fixed on with fcrews, to 

 allow the valves to be eafily taken out and repaired. Two cocks in the fmall pipes oppoGtc 

 A and W will then be ufeful to prevent the depreffion of the columns in the branches of 

 the fyphon. 



It 



