779 



PLATE XXir. 



Fig. 288, Mr. Woltmann'g liydrometrical fly. Tlie 

 plates A,B, are so adjasted by experiment, as to move 

 exactly or very nearly with the velocity of the wind, a 

 few degrees being allow ed as a compensation for the 

 retardation of friction. The cord C is drawn up, and 

 the wheel D is caused to revolve, at a time observed 

 by a stop watch; and its surface is gnuluated so as to 

 number the revolutions of tlie fly. P. 319. 



Fig. 289. An apparatus fur measuring a ship's way, 

 resembling Captain Ilamilton't. A is a funnel partly 

 covered, B a part of the ship's keel, C the upper part 

 of the pipe D, in which the smaller pipe El' slides in 

 a collar of leathers, so as to have the orifice F level 

 with the surface of the water. This pipe has a small 

 aperture at the bottom, wliich limits the magnitude 

 of the stream discharged into the vessel G, the end 

 F being considerably larger. The tube II serves as a 

 gage, to measure the velocity at any given time. P. 

 819. 



Fig. 290. An overshot riheel, on which the water is 

 admitted in a retrograde direction, so as to run ofl" in 

 a continued stream ; at the lower part of the h heel it 

 is retained in the buckets partly by the assistance of a 

 sweep. P. 321. 



Fig. 291. A breast wheel, witli a sweep. P. 322. 



Fig. 292. An undershot wheel. P. 322. 



Fig. 293. A the form of the sail of a windmill : B 

 the best inclination for each part of the sail A, accord- 

 ing to Smeaton's experiments. P. 32-1-. 



Fig. 294. A kite supported by the wind, of which 

 the force acts nearly in the line A B, perpendicular to 



tlie surface of the kitQ;.and this, compounded with the 

 force of the cord A C, produci^s the result A D, which 

 sustains the weight of the kite. P. 324. 



Fig. 295. A ship working against a wind; the force 

 of the wMid acting nearly in the direction AB, per- 

 pendicular to the saijs, the sliip's real course is BC, 

 the angle C B D being the lee way. P. 320. 



Fig. 296. The auoria, or noria, used in Spain, for 

 drawing, water, by a series of earthen pitchers, con- 

 nected by ropes, and passing over a sprocket wheel. 

 P. 327. 



Fig. 297. An undershot waterwhecl, carrying fixed 

 buckets, which raise a portion of water, and deliver it 

 into a trough, furnished w ith a projection, which stands 

 under the buckets, at the upper part of the wheel. 

 P. 327. 



I'ig. 298. A throwing wheel, for draining fens, 

 worked by a windmill or otlierwise, and cairying the 

 water upon a sweep from a lower to a higher level. 

 P. 327. 



•Fig. 299. The rope pump of Vera, for raising water 

 by means of friction; the rope is kept stretched by a 

 pulley under the water, which is loaded with a weight, 

 and slides in a groove. P. 328. 



Pig. 300. The screw of Archimedes, nearly as de- 

 scribed by Vitruvius. P. 399. 



Fig. .001. The screw of Archimedes, as recom- 

 mended by I). Bernoulli. P. 329. 



Fig. 302. A waterscrew, revolving within a fixed 

 cylinder. P. 329. 



Fig. 303. the spiral i>ump of Wirtz. P. 330. 



