WATER. 



inner end or central part of the fpiral paflage communicates 

 with the axis, which is hollow at one end, and communi- 

 cates with the vertical pipe which is to convey the water to 

 the elevated refervoir. The outermoft turn of the fpiral 

 paflage begins to widen at about three-fourths of a circum- 

 ference from the open end, and this gradual enlargement 

 continues for nearly a femicircle ; this part being called the 

 horn. The paflage then widens fuddenly in form of a 

 fcoop or fliovel. The cylinder is fo fupported, that this 

 fcoop may, in the courfe of a rotation, dip feveral inches 

 into the water, and take up a certain quantity of water be- 

 fore it emerges again. This quantity is fufficient to fill the 

 enlarged part called the horn, and is alfo nearly equal 

 in capacity to one turn of the outermoft uniform fpiral. 

 The vertical pipe is connefted with the axis by a turning 

 joint, fo as to admit of the rotation of the axis, at the fame 

 time that it will not allow of the efcape of any water. 



When this cylinder is turned round by a handle applied 

 to the extremity of the axis, a portion of water which the 

 fcoop takes up at every turn, will continually advance in the 

 fpiral, imtil it arrives at the centre ; it wiU then pafs through 

 the hollow in the end of the axle, and will rife upwards in 

 the vertical pipe ; and in the intervals between the periods 

 when the fcoop dips into the water, the horn will become 

 filled with air, and the fucceeding portion of water which is 

 taken in will carry the air before it, fo that the water rifes 

 in the vertical pipe mixed with air. See Screw. 



Dr. Robinfon, in his account of this machine, recom- 

 mends the rifing pipe to be of fmall bore ; for if the pipe is 

 fo large as to allow the air to efcape freely upwards through 

 the water, the machine will raife the water to a certain 

 height, proportioned to the number of turns of the fpiral, 

 and to their diameter ; but if the pipe be narrow, fo that 

 the air cannot rife freely, it will rife in the pipe almoft as 

 flowly as the water. By this circumftance, the water 

 mixed with the air becomes of a lefs fpecific gravity, as it 

 were, and can be raifed to a much greater height than it 

 could be raifed by the mere preffure of the columns of water 

 and air in the different turns of the fpiral. This is effefted 

 with hardly any augmentation of the power, but if the 

 air, after being comprefled, is fuffered to efcape, all the 

 force exerted to comprefs it will be loft. The entrance into 

 the rifing pipe ftiould be no wider than the laft part of the 

 fpiral ; and it would be advifeable to divide it into four 

 channels by a thin partition, and then to make the rifing 

 pipe very wide, and to put into it a number of flender rods, 

 which would divide it into feveral flender channels, that 

 would ferve completely to entangle the air among the water. 

 This procedure will greatly increafe the height to which the 

 heterogeneous column may be carried. 



Jlnother Form of the Spiral Pump. — When the main pipe 

 is very high, the former conftruftion will require either an 

 enormous diameter of the drum, or many fpiral turns of a 

 very narrow pipe. In fuch cafes, it will be much better to 

 make the fpiral in the form of a cork-fcrew, than of a flat 

 form like a watch-fpring ; or, the pipe which forms the 

 fpiral may be wrapped round the fruftum of a cone. 



We regret that we have had no opportunity of making 

 experiments upon a machine of this kind, as its principles of 

 aftion, though treated of by many authors, are not defcribed 

 in a fatisfaftory manner in any works which we have read. 



The chain pump is an effeftive means of raifing water, and 

 with the advantage of a continuous motion. It is generally 

 made with a fquare or round barrel, placed in a perpendi- 

 cular pofition. The chain is furniflied with feveral piftons 

 of the fame figure as the barrel, which are fixed at fmall 

 diftances afunder upon the links of the chain. The ends of 

 Vol. XXXVIII. 



the chain are united togetlier, and it is extended between two 

 wheels, one fixed at the upper end of the barrel, and the 

 other at the lower end ; but fometimes only the wheel at the 

 top is ufed. Thefe wheels have forks fixed on the circum- 

 ference, wliich are fo contrived as to receive one half of each of 

 the fiat piftons in the intervals between the forks, whilft the 

 forks take hold of the hnks of the chain, and draw them up, 

 when the wheel is turned round by means of a handle ap- 

 plied to the axis. The piftons on the chain are made accu- 

 rately to fill the feftion of the barrel, at the lower part near 

 the water, and alfo for a few feet upwards ; but above this, 

 the barrel is made larger, fo that the piftons rife up frse : 

 indeed, the upper part of the barrel is only to conti!:! the 

 water which is brought up by the piftons, and may, there- 

 fere, be fquare, or of any other figure. The lower end of 

 the barrel is immerfed in water, and the chain being caufed 

 to circulate by turning the wheel, each pifton, as it enters 

 into the lower or bored part of the barrel, will bring up 

 water before it in the barrel ; which water will rife in the 

 upper part of the barrel, till it runs over the top ; and as the 

 piftons fucceed each other in a regular fucceffion, they pro- 

 duce a conftant ftream. Chain pumps are chiefly ufed in 

 fliips, where they are worked by the force of men turning 

 winches. ( See Pump. ) In other fituations they are moved 

 by horfes, and fometimes by the impulfe of a ftream of water. 

 They are fo contrived, that by the continual folding in of the 

 piftons, when they enter into the bottom of the barrel, 

 ftones, dirt, or whatever comes in the way, may be cleared 

 off. On this account they are often ufed to drain ponds 

 and fevvers, or to remove foul water, when no other pump 

 could be employed. 



The greateft difadvantage in the chain pump is the fric- 

 tion of the chain, and of the piftons, which is greater than 

 in other pumps ; becaufe feveral piftons are moving in the 

 barrel at the fame time, and alfo becaufe the piftons do not 

 admit of the application of the cup-leathers, which we have 

 defcribed. The edges of the cups would fold up when 

 they enter into the barrel, and get between the edge of 

 the pifton and the barrel. The piftons are, therefore, 

 made with a thick piece of leather, which is placed be- 

 tween two round plates, which form the pifton or faucer, 

 as it is called ; the leather is cut round to the fize of the 

 barrel, fo that the edge of the leather may be applied to 

 the infide of the barrel. In this way, its tightnefs muft 

 depend wholly upon the force with whicli tlie leather is 

 fqueezed into the barrel, and it occafions great friftion to 

 make the piftons fufficiently tight. 



Another variety of the chain pump is an endlefs rope, 

 with ftuffed cuftiions faftened upon it at regular intervals. 

 By means of two wheels or drums, the rope is made to cir- 

 culate, and the cufliions are drawn up in fucceffion through 

 the barrel, and each one carries fome water before it. 



The chain pump is found to raife a greater quantity of 

 water to the fame height, when the barrel is placed in an 

 inchned pofition, than when vertical. M. Behdor recom- 

 mends the barrel to be placed at an angle of 24 degrees with 

 the horizon, and the diftance between the piftons to be 

 equal to their diameter. The reafon of this advantage is, 

 that an inclined pump afts with lefs friftion, becaufe the 

 piftons need not be fo exactly fitted, but they will, by their 

 weight alone, apply clofely to the bottom or loweft fide of 

 the inchned barrel ; whereas the piftons of the vertical pump 

 muft exaftly fill the barrel, or the water will leak down 

 from one to the next in a conftant ftream. 



Bello-ws-Pump A pair of leathern bellows may be em- 

 ployed as a pump, if a fuftion-pipe is apphed to the lower 

 valve, and another pipe to the nozzle, with a valve to 



G prevent 



