566 



HYDRODYNAMICS. 



Throwing 

 Wheels. 



and Chain 

 Pump. 



Throwing 

 wheels. 

 PLATS 

 cccxxiv. 

 Fig. 3. 



a current of water is brought in at a side to fill buckets 

 placed on the concave side of the rim. 



11. On Throning Wheels, or Flash Wheels. 



A throwing wheel, which is commonly driven by a 

 windmill, and used for draining fens, is nothing more 

 than an undershot wheel, the floatboards of which push 

 the water up a curvilineal plane, inclined from a lower 

 to a higher level. One of these wheels is -represented 

 in Plate CCCXXIV. Fig. 3, where WW is the wheel, 

 MN the inclined plane, N the water to be raised or 

 pushed up the declivity MN, and M the drain which is 

 to carry it off. 



'12. On the Chain Pump. 



Chain pump The chain pump, represented in Plate CCCXXV. 

 with plugs. 'Fig. 4, consists of an endless chain WWBA, passing 

 F 'g- * round the wheel WW, and after entering the water to 

 be raised, returning through the tube BA into the 

 cistern MN. This chain carries a number of flat cylin- 

 drical pistons a. b, c, of nearly the same diameter as 

 the tube AB, one half of each piston being received in 

 to openings in the circumference of the wheel. When 

 the wheel is put in motion, the pistons enter the barrel 

 BA, and pushing the water before them, raise it into 

 the reservoir MN. When the wheel is turned with 

 great velocity, the barrel is generally filled with water. 

 Pumps of this kind are frequently placed in an in- 

 clined position, and they raise the greatest quantity of 

 water in this position, when the distance of the flat pis- 

 ton is equal to their breadth, and when the inclination 

 of the barrel is about 24 2 1 '. The Spanish noria is the 

 same as a chain pump, having a number of earthen 

 pitchers placed between two ropes in place of a chain. 



These machines are sometimes called cellular pumps, 

 and when stuffed cushions are used in place of pistons, 

 they are called Paternoster pumps. 



Chain pump Chain pumps are sometimes construe' ed without the 

 with buck- pi s ton a, b, c. In this case, the barrel AB is also re- 

 Fjg. 5. moved, and they have the form shewn in Fig. 5, 

 where W, W are two wheels with a set of buckets fixed 

 to an endless chain, which passes round their circum- 

 ference. By turning the upper wheel, the buckets dip 

 into the water with their mouths downwards, and rising 

 on the other side, convey the water into the reservoiratM. 



13. On the Hair Rope Machine of the Sieur Vera. 



Vcra's hair The hair rope machine of the Sieur Vera is shewn 

 rope ma- in Fig. .6. It consists merely of a rope AB made of 

 *J me ' hair, passing round a wheel W, and kept stretched 

 by going round a pulley P, fixed in the water. By 

 turning the handle H, the rope rises loaded with the 

 water that adheres to it, and when it reaches the top, 

 it passes through a small tube which rubs the water 

 from it, into a cistern. In a machine of this kind, 

 where the wheel was .three feet in diameter, the rope 

 half an inch in diameter, and the well 95 feet deep, 

 a labouring man could produce only 60 revolutions 

 in a minute, and could not continue the exertion long. 

 This raised 6 gallons in a minute. A great deal of 

 water was raised when the wheel made 50 turns in 

 a minute, but very little when it made only 30 turns. 

 The rope soon decays if it is not made of hair. See 

 Rozier's Journal de Physique, torn. xx. p. 132 ; and Ca- 

 vallo's Natural P/nlosop'iy, vol. ii. p. 441. 



14. Description of Whilehurst's Engine. 



Whitr- Mr Whitehurst, an ingenious watchmaker of Derby, 



appears to have been the first who entertained the in- 

 genious idea of raising water by means of its momen- 



turn. A machine upon this principle was erected at White- 

 Oulton in Cheshire, and was described in the Trans- hum's 

 actions of the Tloyal Society for 1775. This machine 

 is represented in Plate CCCXXIV. Fig. 7, where AM pTTriT" 

 is the reservoir of water, whose surface at M is on a, CCCXXIY 

 level with B, the bottom of the reservoir BN. The Fig. 7. 

 main pipe AE is about 200 yards long, and 1| inches 

 in diameter, and the branch pipe EF is of such a size 

 that the cock F is about 16 feet below the surface of 

 the water at M. A valve box with its valve a is shewn 

 at D, and C is an air vessel into which are inserted 

 the extremities m n of the main pipe, which are bent 

 downwards for the purpose of preventing the air from 

 being driven out when the water is forced into it. 

 Now, when the cock F is opened, the water will rush 

 out with a velocity of nearly 30 feet per second. A 

 column of water, therefore, two hundred yards long 

 and 1^ inch diameter, is now put in motion, and must 

 have a considerable momentum. Hence, if the cock F 

 is suddenly shut, the water will rush through the valve 

 n into the air vessel C, and condense the included air. 

 This condensation will take place every time that the 

 cock is opened, so that the included air being com- 

 pressed, will press upon the water in the air vessel, 

 and raise it into the reservoir BN. This simple and 

 ingenious machine is obviously the same in principle 

 as the hydraulic ram invented by Montgolfier.and which 

 differs from it only in this, that the operation analogous 

 to that of opening the cock F is produced by the mo- 

 tion of the water itself, as will be seen in the following 

 description of this ingenious contrivance. 



15. Description of Montgolfier's Hydraulic Ram. 



This interesting machine was first constructed by 

 Montgolfier about the year 1 797, and has been brought d 

 to a very perfect state by a series of improvements yigs. 8, 9 

 which he has successively made upon it. The rams 10, 11. 

 which we have represented in Plate CCCXXIV. Fig. 8, DebCriptiOT 

 9, 10, and 11, contain the improvements which have O t the m- 

 been made so late as 1816. The large pipe AB called chine, 

 the body of the ram, passes through the side of the re- Fig. -8, 

 servoir PQ, from which the fall of water is obtained. *dfrig. * 

 It has a trumpet mouth at one end A, and at the other 

 end an opening HH, which can be closed by valves 

 C or D. When these valves are open, the water will 

 issue at HH with a velocity due to the height AP; but 

 when the internal valve C is closed, as in the figure, 

 the water is prevented from issuing. When the valve 

 C opens, it descends into the position shewn by the 

 dotted lines GG, being guided between three or four 

 stems g g, which have hooks at the lower ends for 

 supporting the valves. In this case the water has a 

 free passage between these stems, and the width of the 

 passage can be increased or diminished by the screws 

 with which the stems are fixed. The valve C is made 

 of metal, and has a hollow cup or dish of metal attached 

 to its lower surface. The seat HH of the valve is wider 

 than the diameter of the pipe AB. It consists of a 

 short cylinder or pipe screwed by its flanch hh into 

 the opening of the upper surface of the head R of the 

 ram; and the cylinder is .so formed as to have an in- 

 verted cup or annular space i i round the upper part of 

 it for containing air, which cannot escape when it is 

 compressed by the water. A small pipe k I, leading 

 from this annular space to the open air, is furnished 

 with small valves, k, I, one of which, k, opens inwards 

 to admit the air into i, i, but to prevent its return, 

 while the other valve, /, admits a certain quantity of air, 

 and then shuts and prevents any farther entrance. The 



