24-2 "^Icmo'tr on the Supply artel 



villi a a)ck. Each end of this pipe communicates with one 

 ol the compartments above mentioned. 



P is a table aflixed to the cafk by means of irons, which 

 are at pleaiure flid into or out of ftaples. One of thefe irons, 

 and its ftaples, mav be feen near the letter Q. They are 

 fattened to pieces of wood which rim Icncjthwife under the 

 tabic, and which arc fo grooved as to fiipport a block of wood 

 which llidcs between them. Through this block palVes the 

 fcrew S, which tlides backward and forward in the opening 

 TRV. The ftand TV, which may be obferved under the 

 lamp, is loofely put on this fcrcw, as a wheel is placed on 

 its axletrce. It rifes and falls with the fcrcw ; but is prevented 

 from turning round with it, by the upright drip of wood T. 



Having defcribed the confiruAion of the hvdrollatic blow- 

 pipe, I proceed to an explanation of the principle and man- 

 ner of its action, and to a detail of the ufes to which it may 

 be applied. 



Suppofc that as much water were poured into the cafk A, 

 lig. I, as would fill the lower apartment, and rife above the 

 partitioii B; one or two inches. Let fig. 4 be a reprefenta- 

 tion of the calk when fupplied with this neceflary quantity 

 of water. When the machine is at reft, the top of the bel- 

 lows, being loaded with lead, is dcprefled as low as the folding 

 of the leather will permit, and the fmall fpace which re- 

 mains in confequence of this folding, between the top of the 

 bellows and the bottom ot the calk, becomes filled with wa- 

 ter, which leaks through the upper valve. Let the bellows 

 be extended hv deprefling the handle at a. The upper valve 

 will (liut tight; and a quantity of water equal to the bulk, 

 which the bellows will gain by extenfion, will rife through 

 the pipe D, to the external apartment 5 and the weight of the 

 atmofphere being removed from the top of the valve in the 

 bottom of the cafk, the air will prefs through the fuftion- 

 pipe I H, lift this valve, and occupy the vacant fpace within 

 the bellows. If the hand be then removed from the handle, 

 the lead in the top of the bellows will again deprefs it, and 

 the air drawn into them, being thereby comprefled, will force 

 open the upper valve, and afcend. During its afcent it will 

 receive a ftrong lateral tendency from the hood, which will 

 make it pals out at the open fide of the hood, into that com- 

 partment which is immediately over this opening; and as by 

 turning the rod, this part of the hood mav be brought under 

 either compartment, fo the air mav be thrown into either ot 

 them; and one of them being filled with one fpecies of gas, 

 the other may be filled with another fpecies : nor can there 

 be any danger of mixture 3 becuufe, a^ the pipe D is fliorter 



than 



