524 Experiments refpc&ing Heal. 



on the plate O), filled with atmofpherie air: at it9 greateft 

 height its mouth is exactly on a level with the mouth P of 

 the tube P,Q, R,S, bent at right angles at Q. and R, and 

 joined at the end S to the tube ab, each end of which is 

 Iikewife bent at right angles and furnifhed with a ftop-cock. 

 The tube TU, fitted air-tight to the end b of the tube ab, 

 can be taken off" at T without deranging the end U. This 

 being taken off, and the ftop-cock b being opened, a com- 

 munication is made between the air in the room and that in 

 the receiver ; which being now prefled down, either by 

 the hand applied, or weights put on at O, discharges the air 

 it contains at the opening at T ; the place of which thus be- 

 comes {applied with water np to the top of the internal tube 

 at P, which almoft touches the upper part of the receiver. 

 If the experiment require that the portion of atmofpherie air 

 contained in the tube PQRS fhould be alfo removed (as 

 when oxygen and hydrogen are to be combined in the form- 

 ation of water), all that is neceflary is to pour water into the 

 tube, through the opening T, till all the air be driven out of 

 the tube, and its place be occupied bv water up to the open- 

 ing T. Fill alfo the tube TU with water. By this means 

 the receiver and the tubes are entirely deprived of atmo- 

 fpherie air. To clear the tubes from water, that the oxygen 

 gas (or any other, according to the intention of the experi- 

 ment) may find no oburu6r.ion when the receiver is wifhed 

 to be charged, a large tin Malic, having a neck ground to lit 

 the cock Q, and charged with oxvgen gas, is joined to the 

 cock Q,, which muft then be opened : the gas aicends from 

 the 8a(k, and the water in SR and PQ takes its place. The 

 coek U mufi then be opened, to allow the water in the tube 

 TU to delcend into the calk V. 



Oxygen gas is then to be transferred to the receiver from 

 a calk V, previously filled with it. The cock a is kept {hut, 

 and b opened, and water is made to defcend from the funnel 

 W into the calk bv turning the cock c. The water, of 

 courfe, difplaces an equal volume of gas in the calk, and 

 forces it through the tubes UT, ba, and SRQP into the 

 receiver E. difplacing the water contained in it. While the 

 gas is pafling into the receiver, the funnel \\ mufi never be 



allowed 



