274 



THE TROPICAL AGRICULTURIST. [October i, 1885. 



couUl not be made equal to working an Excelsior 

 roller. "The capacity of the buckets can be in- 

 creased, " we insisted, "and a fly-wheel can be add- 

 ed, to increase momentum," and finally we made 

 a "paction" with our good friends M-essrs. John 

 Walker & Co., that if a member of their firm would 

 make the alterations and additions we wished, the 

 responsibility of failure to work the Excelsior, if 

 failure accrued, should be ours, not their's; and, 

 accordingly, the experiment of adapting a Ifi-feet 

 diameter coffee pulper wheel to the working of an 

 Excelsior roller will be shortly tried at Abbotstord 

 and the result published. The letter of "D. K. M. " 

 which reached us while writing, which will be 

 found elsewhere, and which impeaches Mr. Ai'm- 

 strong's infallibility as to hydraulic laws, or at any 

 rate the principles on which the power of water- 

 wheels depends, gives us fresh hopes of success. 

 In fact, we believe our good, though at first scept- 

 ical friend, Mr. Walter Lamont, of Messrs. John 

 Walker & Co., is himself now convinced that suc- 

 cess is possible and is determined to achieve suc- 

 cess even if he has to gratify our whims of en- 

 larging the wheel buckets and having a fly-wheel 

 attached. 



We feel bound, after some observation and 

 reading, entirely to agree with Mr. Armstrong's 

 preference for the upright water-wheel as com- 

 pared with the turbine. But we cannot help 

 believing that Mr. Armstrong has not sufficiently 

 appreciated the value to Ceylon tea planters of 

 what our American cousins call "water privileges." 

 To a very large number of the mountain plant- 

 ations of Ceylon can be applied the dictum of 

 the Scotchman about a place in Ambagamuwa. 

 Addressing the proprietor, he said, " I dinna ken 

 aboot yer breed, [bread] , but, my certy, yer 

 water will be sure." It is not simply the volume 

 of water but the fall which can be secured that 

 tells in the obtainment of power, and we think 

 our readers will sympathize with the feeling 

 which led us to resent the suggestion of import- 

 ing a steam engine to an estate which is known 

 to the Tamil coolies as Anivi Tottam, the Water- 

 fall Ciarden. A steam engine requires skilled 

 attendance, and if not carefully managed is apt 

 to " burst up." Of course steam power must be 

 employed where water is scanty and the fall slight 

 or nil. 



But on the vast majority of the hill plantations, 

 at least, of Ceylon, water jjower is abundant, 

 and we may be doing some of our readers a 

 service, by quoting a few details regarding the 

 force of element, and how that force can best 

 be utilized: — 



(From Mohsv^oTilCs Pocket Book of EnfjinenruKi Fovnr 

 •ulce 31st Edition.) 

 Theoretical power being 100 



Undershot water-wheels '35 



Poncelct'.s undershot water wheel "60 



Breast wheel '55 



High breast 'GO 



Overshot wheel '68 



Turliine "70 



From the above it will be seen that the super- 

 iority in power of the turbine is not such as 

 to compensate for its admitted greater liability 

 to accident. Where there is abundance of water, 

 there is, clearly no motor so effective and at 

 the same time so simple and so little liable to 

 get out of order as the overshot water-wheel. 

 But the effectiveness of the overshot wheel de- 

 pends not only on the number and capacity of 

 the buckets and the mass of water projected on 

 to the wheel, but also on the direction in which 

 the water is made to fall, so that in running 



away it may offer the least amount of resistance 

 to the movement of the wheel in its lower portion. 

 This is very clearly explained in the well-written 

 article on water power in Cliumbers's Encijclo- 

 piedia : — 



The most usual, and generally the most eligible, 

 mode of applying water to the driving of machinery 

 is by means of a vertical wheel ; and the wheel is 

 put in motion either by the water acting on blades 

 or floats by impulse derived from its velocity acquired 

 in fading, or by the weight of water being applied 

 to one side of the wheel. The former mode of ap- 

 plying the water is generally adupted in low falls, 

 say under six feet or thereabout, and to what is 

 called an undershot whctl— i. e., a wheel where the 

 effective head of water is below the level of the centre ; 

 and to make the applicatinn efficient, that portion 

 of the periphery of the wheel measuring from the 

 point of impact of the water to a point directly 

 below the centre, requires to be surrounded by a 

 casing generally of stone, but sometimes of cast-iron, 

 called the arc, closely fitted to tbe rxtremiti of the 

 floats, so as to prevent any considerable escape of water. 

 The other mode of applying the waler to a vertical 

 wheel hy making it act by its gravity, is the more 

 perfect and economical mode, where circumstances 

 will admit of it, and is generally adopted in falls of 

 any considerable height, say of six feet and upwards, 

 and where the water can he let on above the level 

 of the centi'e. The wheels are called respectively 

 hi'east and oecrsliot wlieih, according as the wati r is 

 let on more near to the level of the centre cr to the 

 crown of the wheel ; and they have, instead of 

 straight floats curved or kneed buckets, according as 

 they may be made of iron-plate or of wood, and of 

 such a shape as to retain the water down to the lowest 

 p issihie point. There are generally in good wheels 

 ventilating openings in the sole for the escape of air. 

 The overshot wheel has this disadvantage that, as the 

 water has little or no power until considerably past the 

 top centre, the wheel is burdened with a useless weight 

 of water. 



The direct overshot wheel without changing its di- 

 rection, right over the top, which arrangement has 

 this advantage that as the top of the wheel moves 

 in the same direction as the stream, it gets the benefit 

 of the whole initial velocity and impulse of the water ; 

 but, on the other hand, the bottom of the wheel, if 

 at all immersed in water, which it generally is to some 

 extent meets with obstruction by moving ag.allist the 

 current. 



Tho pitch-hack overshot is a modification of the last, 

 making the water to pass alongside tho wheel, and 

 then to return and be let on the top of the whejl 

 hi a contrary direction. This requires longer and more 

 complicated troughs, and by the change in direction, 

 part of the impulse from the water is lost, but the 

 bottom ol the wheel moves in the dh-ection of the 

 tail-water, and is not liable to be impeded by being im- 

 mersed in it. 



On the whole, it is generally thought better to apply 

 tho water at about 30 degrees from the top of the 

 wheel. In such high-breast or n>arly over-.shot wheels, 

 the water is let on the buckets over the top of the 

 sluice, which is made to open by lowering, and shut 

 by lifting. In this way, however small may be the 

 quantity of water, it is always applied the highest 

 possible lei'el, which is of importance when it is its 

 weight multiplied by the height of decent, and not its 

 impulse, that yields the effective power. 



The structure of the overshot and breast wheel is 

 nearly the same as that of the undershot, excepting in 

 the substitution of curved buckets, or angular buckets, 

 for straight floats; but even in the undershot wheel the 

 floats are sometimes made with a slight curvature. 



In reckoning the power of water, its weight being 

 e2i lb. to a cubic foot ; theoretically, 528 feet falling 

 vertically 1 foot a minute, would he cijual to 1 Boulon 

 and Watt horse-power of 33,000 lb. lifted 1 foot a 

 minute ; but the effective power is far short of that, and 

 60 per cent of it, requiring 880 cubic feet, falling 1 foot 



