781 

 PLATE XXIV. 



Fig. 824, Tlic cupping instrument of Hero. The 

 cavity A was partly exhausted by applying the mouth 

 repeatedly to the pipe D, the stopcock U being turned 

 after each application. When the stopcock C was 

 opened, the air at D in contact w ith the skin was also 

 rarefied, and the effect ot" suction was produced. P. 

 539,053. 



Fig. 3H5. Mr. Cuthbertson's air pump. When the 

 piston rod A is depressed, it leaves the piston B a 

 little behind it, so as to make an opening betwetn two 

 conical parts which arc ground togetlier, and the air 

 escapes from the lower part of the barrel into the 

 Tipper part; when it is elevated, the whole piston is 

 raised, and a wire, which slides through the axis of the 

 rod, raises a small valve at the bottom of the barrel, 

 which leads to the receiver C, by the tube DE: the 

 air is forced from the upper part of the barrel through 

 a valve in the oil vessel F, wlience the oil runs back, 

 when it overflows, by a tube leading to the mouth of 

 the barrel; and if this tube be stopped by turning its 

 cock, the air may be condensed into a receiver fixed 

 at G. At U is a long gage, with a barometer im- 

 mersed in the same bason of mercury. The piston rod, 

 which is hollow, has a perforation a little above A, to 

 admit the oil, in order that the wire may work freely 

 in it. P. 340. 



lig. 326. Tlie two flics A and B being caused to 

 revolve with equal velocities V)y the descent of the 

 weight C, they continue to move for an equal length 

 of time in the vacuum of the air pump. P. 341. 



I'ig. 327. The air in the bottle A expands, when the 

 receiver B is exhausted, and causes the water to rise 

 in a jet, P. 341. 



Fig. 328. A pear gage ; to be suspended in a receiver 

 by a book like that which is shown in fig. 325. P. 

 342. 



Fig. 329. A condenser, with screws, for confining 

 the receiver. A is a gage for showing the degree of con- 

 densation; B the piston of tlie Syrinire, with a valve 

 of the best kind, which is conical, and is coiyfined by 

 a spiral spring. But iu common, the valves are made 

 of leather, wjth a phite of metal to strengthen it. P. 

 342. 



Fig. SSO. A diving bell. A is the forcing pump, 

 B a stopcock for letting out the heated air, C a strong 

 glass for giv ing light, D a float for the security of tlie 

 diver. P. 343. 



Fig. 331. Laurie's hydraulic bellows. When the 

 yessel A is raised, the air enters at the valve B; when 

 it is depressed, the valve B shuts, and the air is forced 

 through the pipeC D, which conducts it to the reser- 

 voir E,whei"e it is confined by the valve F, and forced by 

 the pressure of the water through the pipe G. P. 343. 



Fig. 332. Mr. Watt's gasometer. The pressure is 

 regulated by the magnitude of the weights A and B, 

 which act by the spiral fusees C, D, so as to guslain a 

 part of the weight of the inverted vessel, represented 

 by the exterior dotted line. The gas is admitted at E 

 or F, and is delivered at 0. G H is a gage for show- 



ing the height of the water within and without the 

 moveable vessel. I is a cock for lettii^ off the water 

 P. 344. 



Fig. 333. The shower bellows. The stream A, 

 passing through the strainer B, carries with it a quantity 

 of air through the pipe C, which rises to the upper 

 pait of the air vessel D, and is discharged by the piue 

 E. P. 344. 



Fig. 334. The centrifugal bellows. By the revolu- 

 tion of the fly, the air is caused to enter at A, and is 

 discharged at B. P. 345. 



Fig. 335. The original steam engine of Savery. Tlie 

 vessel A being filled with steam from the boiler B, and 

 the stopcock being turned, the steam cools and is con- 

 densed, and water is forced into its place by the 

 pressure of the atmosphere, through the valve C : 

 the steam is then readmitted, and forces the water to 

 ascend through the valve D and the pipe U E. The 

 vessel F acts alternately with A. P. 317. 



F'ig. 836. The common steam engine of Xcwcomen 

 and Beighton. The steam being admitted into the cy- 

 linder A below the piston, tlic weight B is allowed to 

 descend: a jet of water is then admitted by the pipe 

 C, which condenses the steam, and the pressure qf 

 the atmosjihere then depresses the pi^ton: a part of this 

 water is admitted by the pipe i) into the boiler, in 

 order to keep it suliiciently lull. P. 347. 



Fig. 337. Mr. Watt's steam engine. The steam, 

 which is below the piston, is suffered to escape into 

 the condenser A by the cock B, which is opened by 

 tlie rod C, and at the same time the steam is admit- 

 ted by the cock D into the upper part of the cylinder; 

 when the piston has descended, the cocks 11 and F act 

 in a similar manner in letting out the steam from above 

 and admitting it below the piston. Tlie jet is suppli- 

 ed by the water of the cistern G, which is pumped 

 uj) at H from a reservoir : it is drawn out, togetlier 

 with the air that is extricated from it, by the air pump 

 I, which throws it into the cistern K, whence the 

 pump L raises it to the cistern M; and it enters the 

 boiler through a valve, which opens whenever the 

 float Jvi descends below its proper place. The pipes 

 O and P serve also to ascertain the quantity of water 

 in the boiler. The piston rod is confined to a motion" 

 nearly rectilinear by the frame Q; tlie fly wheel R is 

 turned by the sun and planet wheel S,T; and the strap 

 U turns the centrifugal regulator W, which governs 

 the supply of steam by the valve or stopcock X. P. 

 349. ,, 



F'ig 338. Mr. Symington's steam boat. A is the 

 boiler, B the cylinder, C the piston, D the conden- 

 sation pipe, E the air pump, F stampers for break- 

 ing ice. V. 349. 



Fig. 339. An air gun. The air is fiirced by the 

 syringe A into the cavity surrounding the barrel, whence 

 it is discharged by the valve B, which is opened either 

 immediately by the action of the trigger C, or by a 

 spring, which is bent by cocking the gun, and set at 

 liberty by the trigger. P. 351. 



VOX. I. 



5e 



