776 



PLATE XIX. 



Fig. 239. The surfaces of the fluid in the bent 

 tube A B lemBin on the same level, in the same man- 

 ner as if the tube were absent, and the fluid made a 

 part of that which is contained in the reservoir C D, 

 P. 260. 



Fig. 240. The bucket A being suspended by the 

 rope B, and made to revolve rapidly round its axis, the 

 surface of the water assumes a panibolic form. P. 

 261. 



Fig. 241. A heavier fluid being contained in the 

 upper part of the bent tube A li, which is immersed 

 in the lighter fluid filling the vessel CD, the fluid in 

 the tube remains in a state of tottering equilibiiura, 

 when its surfaces arc in the same level. P. 261. 



Fig. 242. The fluid ABC presses on the bottom of 

 the vessel BC with the same force as if the vessel were 

 of the form B C D E. P. 261. 



Fig. 243. The portion A B C D of the fluid being 

 supposed to be congealed, and then to fonn a part of 

 the vessel, the pressure oji the bottom would remain 

 unaltered. P. 263. 



Fig. 244. The weight A may be supported by the 

 pressure of a small quantity of fluid, either by making 

 the surface of the vessel B C very large, and the height 

 of the tube D E moderate, or, while the vessel F re- 

 mains of a moderate size, by making the height of the 

 tube G H very great. P. 263. 



• Fig. 245. The pressure on any small part of the side 

 of the vessel A B, at C or D may be represented by 

 the line C E,D F, and the whole pressure on the side 

 by the triangle BG, of which the centre of gravity is 

 at II; and if the side A I be supported by a single 

 prop, it must be placed at the point K, the height of 

 *hich is equal to that of II. P. 265. 



Fig. 246. If the heiglit of the surface A above B he. 

 to BC as tlie specific gravity of tiie {iuid in BC to that 

 of the fluid in A B, the fluids will support each other. 

 r. 265. 



Fig. 247. Two square beams floating at the depths 



shown at A and B, will have a certain degree of sta- 

 bility, but if they sink, as at C, they will overset. But a 

 beam of the breadth shown at D will always float 

 securely. P. 26r. ^ 



Fig. 248. A jar containing images of fishes, with 

 bubbles of air in them, which sink when tlie cover of 

 the jar is pressed with the hand. P. 268. 



Fig. 249. Dr. Ilookc's semicylindrical counter- 

 poise, by means of which a vessel is kept always full. 

 P. 268. 



Fig. 250. The form into which the flexible bottom 

 of a cistern would be bent by the jjressure of the water: 

 the curve is the same as that into which an elastic rod 

 would be bent by forces acting at A and B. P. 269. 



Fig. 251. TTiebottle A, containing air and mercury, 

 has the tube AB fitted into it: and when the jar 

 C D, in which it is enclosed, is exhausted by means of 

 the air pump, the elasticity of the air in the bottle 

 forces the mercury up the tube. P. 270. 



Fig. 252. An instrument for showing the buovanS 

 effect of the iiir, called by Boyle a statical baroscope; 

 the index A shows, on the scale BC, tlie degree in 

 which the ball D is obliged to descend, by the di- 

 minution of the weight of the air. P. 272. 



Fig. 253. The line denoting the natural density 

 of the air, the line 1 A next above it shows the degree 

 in .which the air is expanded at the height of a mile, 

 and 1 B the density of the air at the same height: in 

 the same m.inncr 10 C shows the expansion of the air 

 at the height of 10 miles, .ind 10 D its density; and 

 51'", below the line, the density which it would acquire 

 at the depth of 5 miles below the earth's surface. The 

 lines AC,DBE, are of the kind called logarithmic 

 curves. P; 272. 



Fig. 954. The box or bason, in which the mercury 

 of the common b:iromcter is contained : A is a float 

 for adjusting the luiglit, by means of the screw B, 

 operating on th(: leather which forms the bottom of 

 the cavity. P. 376. 



