WATER. 



fome time before they arrive at the greateft height of the 

 wheel ; and, therefore, the trough is of necefTity placed 

 lower than the diameter of the wheel, or a confiderable por- 

 tion of the water would be loft, and in any cafe part of the 

 water is raifed above the level of the trough. 



Span'iPi Buctet-JVheel.—^h: Townfend, in his Travels 

 through Spain, defcribes a fimple machine which is ufed at 

 Narbonne for watering of gardens. The water is raifed by a 

 vertical wheel, which is twenty feet in diameter, on the cir- 

 cumference of which is fixed a number of little boxes or 

 fquare buckets, for the purpofe of raifing water out of the 

 ciftern communicating with the canal below, and to empty 

 it in a refervoir above, placed by the fide of the wheel. The 

 buckets have a lateral orifice to receive and to difcharge the 

 water. The axis of this wheel is embraced by four fmall 

 beams, crofTmg each other at right angles, and tapering at 

 the extremities fo as to form eight little arms. This wheel 

 is near the centre of the path in which the mule walks, and 

 contiguous to the vertical axis, into the top of which the 

 horfe-beam is fixed ; but near the bottom of this axis it is 

 embraced by four little beams, forming eight arms, fimilar to 

 thofe above dcfcribed, on the axis of the water-wheel. As 

 the mule which they ufe goes round, thefe horizontal arms, 

 fupplying the place of cogs, take hold each in fuccefhon of 

 thofe arms which arc fixed on the axis of the water-wheel, 

 and keep it in rotation. This machine may be made very 

 cheap, and will throw up a great quantity of water, yet 

 undoubtedly it has two defefts ; the firft is, that part of the 

 water runs out of the buckets, and falls back into the well 

 after it has been raifed nearly to the level of the refervoir ; 

 and the fecond is, that a confiderable proportion of the water 

 to be difcharged is raifed higher than the refervoir, and falls 

 into it only at the moment when the bucket is at the higheft 

 point of the circle, and ready to defcend. 



The Perfian wheel -with f'win/wg buckets is free from fome 

 of the defeds of the laft machine. The buckets are loofe, 

 and each hangs from the circumference of the wheel by a 

 pin, on which it fwings or turns freely ; and as the bucket 

 is fufpendcd by its upper part, it will hang perpendicular, 

 with the mouth upwards, in all pofitions of the wheel. From 

 the time it dips in the water and is filled, until the bucket 

 arrives at the upper part of the wheel, it is carried by the 

 motion of the wheel againft the edge of the trough, and in- 

 clined fo far as to difcharge its contents into the trough. 

 (See Persian- Wheel.) The pins are fixed into the circum- 

 ference of the wheel, and project fideways therefrom a fuf- 

 ficient diftance to fupport the buckets, and carry them over 

 the elevated trough. Sometimes the wheel is made with 

 two rims, and each bucket is fufpended upon an axis be- 

 tween them : the end of each axis paffes through the rim of 

 the wheel, and is bent to form a (hort lever, which is carried 

 by the motion of the wheel againft a fixed rail, and thus 

 inclines the bucket to difcharge the contents into a trough 

 which is fixed to the rims of the wheel immediately beneath 

 the bucket, and has a fpout projefting at the fide of the 

 wheel, to carry the water fideways and deliver it into the 

 trough, which is fixed at the fide of the wheel for its 

 reception. 



As the Perfian wheel is a very effeftive machine in fitua- 

 tions where the elevation is required to be but fmall, the 

 following directions, given by M. Belidor for its conftruc- 

 tion, are worthy of attention : firft fix the diameter of the 

 wheel fomething greater than the altitude to which the water 

 is to be raifed ; fix alfo upon an even number of buckets, to 

 be hung at equal diftances round the periphery of the wheel ; 

 and mark the pofition of their centres of motion in fuch a 



manner, that they will ftand in correfponding pofitions in 

 every quarter of the circle. Suppofe vertical lines drawn 

 through the centre of motion of each bucket in the rifing 

 part of the wheel, and they will interfeft the horizontal 

 diameter of the wheel in points, at which, if the buckets 

 were hung, they would make the fame refiftance to the 

 moving force, as they do when hanging at their refpeftive 

 places on the rim of the wheel. Thus, fuppofing there are 

 eighteen equidiftant buckets, then while eight hung on each 

 fide of a vertical diameter of the wheel, there would be eight 

 on the other fide, and two would coincide with that diame- 

 ter : in this cafe, the refiftance arifing from all the full 

 buckets would be the fame as if one bucket hung on the 

 prolongation of the horizontal diameter, at the diftance of 

 twice the fine of 20° + twice the fine of 40° + twice the 

 fine of 60'' + twice the fine of 80°, thefe being the fines to 

 the common radius of the wheel. 



To know the quantity of water that each one fhould con- 

 tain, take four-ninths of the abfolute force of the ftream, 

 that is, four-ninths of the weight of a prifm of water whofe 

 bafe is the furface of one of the float-boards, and whofe 

 height is equal to that through which the water muft fall in 

 order to acquire the velocity with which the ftream moves. 

 This is the power which fhould be in equilibrio with the 

 weight of water contained in the buckets of the rifing femi- 

 circle. Then fay, as the fum of the fines mentioned above 

 is to the radius of the wheel to the centre of the float- 

 board, fo is the power jult found to a fourth term, one-half 

 of which will be the weight of water that ought to be con- 

 tained in each bucket. Laftly, the velocity of the float- 

 board of the wheel will be to that of the ftream nearly as 

 one to tvs"o and two-fifths, and from this the number of re- 

 volutions it will make in any determinate times may be 

 known, and of confequence the quantity of water the wheel 

 will raife in the fame time, fince we know the capacity of 

 each bucket, and the number of them which will be dif- 

 charged in every revolution of the wheel. See Persian 

 Wheel. 



The Chinefe Bucket-Wheel. — Sir George Staunton, in his 

 account of the Embaffy to China, gives the following de- 

 fcription of a bucket-wheel, which is different from any we 

 have met with in the hydraulic colleftions, and conftrufted 

 with that fimplicity which diftinguifhes the Chinefe inven- 

 tions. Two hard-wood pofts or uprights are firmly fixed in 

 the bed of the river, in a hue perpendicular to its banks. 

 Thefe pofts fupport the pivots of an axis of about ten feet 

 in length ; this is the axis of a large wheel confifting of 

 two unequal rims, the diameter of the rim which is neareft 

 to the bank being about fifteen inches lefs than that of 

 the outer rim ; but both rims dip into the ftream, while the 

 oppofite points or top of the wheel rife above the elevated 

 bank over which the water is to be raifed. This double 

 wheel is framed upon the axis, and is fupportcd by fixteen 

 or eighteen fpokes, inferted obliquely into the axis near each 

 extremity, and crofling each other at about two-thirds of 

 their length. They are there ftrengthcned by a concentric 

 circle, and are faftened afterwards to the two rims. The 

 fpokes inferted in the interior extremity of the axis reach to 

 the outer rim, and thofe proceeding from the exterior ex- 

 tremity of the axis reach to the inner and fmaller rim. Be- 

 tween the rims and the croflings of the fpokes is a triangu- 

 lar fpace, which is woven with a kind of clofe bafket-work, to 

 ferve as ladle-boards, or floats. Thefe fucceffively receiving 

 the current of the ftream, obey its impulfe, and turn round 

 the wheel. 



The buckets which take up the water are fmall tubes or 



fpouts 



