165 



WATER-WHEELS. 



WATER-WHEELS. 



766 



A bath requires, each time it it used, about . . 75 gallon!. 

 A horse requires, per day . ..... 104 ,, 



A two .wheeled private carriage, per day . . . 9 

 A fuur-wheeled ,, ... 17 ,, 



Each individual in a house, . . . 4 to 8 



A water-cl.-cet, every time it is used . . . . 1 



A yard superficial of garden ground . ' 



gallon. 



A yard superficial of garden ground .... 0*33 

 A yard superficial ol roadway, every time it is watered 0-2S 



Generally speaking, the charge for a house supply is based upon its 

 estimated rental, in England at least, and it very rarely attains 5 per 

 cent, on that value. But an additional charge is made whenever more 

 than one water-closet is in the house ; when fixed baths are used ; for 

 coach-houses and stables, according to the number of carriages and 

 horses; and for gardens. Such trades as tanners, fellmongers, hair- 

 washers, curriers, glue-makers, dyers, hatters, brewers, distillers, manu- 

 facturers, inns, public baths, and steam-engines, are considered as large 

 consumers, and are usually supplied with water by meter. The price 

 nnder the latter arrangement is, in London about 6d. per 1000 gallons. 

 The supply of water for the extinction of fires is, in this country, cast 

 upon water companies ; and it appears that in the New River district 

 of London there is at least one fire-plug in every length of sub-main 

 equal to 73 yards, on the average ; on the great mains there is a plug 

 to every 157 yards. For the purpose of street- watering, stand-pipes 

 ou;;ht to be placed at distances of about 500 yards apart : in our 

 climate it appears that the streets require watering between 120 and 

 135 days in the course of the year, sometimes even twice in the day. 

 The quantity of water varies with the nature of the road surface ; and 

 where nicety of calculation is required, it may be considered that 600 

 square yards of macadamised road will only require one ton of water, 

 whereas 400 square yards of paved road will require that quantity. 

 It may be added, that the street-plugs (the borne fonlaines) used in 

 Paris to cleanse the channels are usually placed at distances of about 

 140 yards, and that they discharge at intervals during the day a total 

 quantity of water equal to 05u gallons each : more than half the total 

 supply of Paris is thus poured into the streets. 



It would be idle to give any statistics of the capita] invested in 

 water-works, either in England or elsewhere, because new works of 

 this description are being constantly undertaken. In London alone 

 the capital invested in the various Water- Works Companies cannot be 

 considered to be much less than eight millions sterling ; and, as a 

 general rule, it would appear that the average cost of conducting a 

 water supply to the doors of the houses in a town varies between '21. 

 and 31. per head of the population ; whilst the house distribution gives 

 rise to a further outlay varying from il. to 20i. per house, according to 

 its character and to the system of distribution adopted. In newly- 

 established works, the constant-delivery system admits of considerable 

 economy in this respect. Of late years, also, it may be added that 

 more attention has been paid than was formerly the case to the pressure 

 tinder which water is delivered in towns ; and that, to a great extent, 

 the distinction between high and low service has ceased to exist. In 

 new works the mains are always laid under such conditions of pressure 

 upon the water they contain as to cause the latter to flow in the loftiest 

 rooms of the loftiest houses in the respective towns. 



In Kobison's ' Mechanical Philosophy,' in Playfair's ' Lectures,' in 

 Jamieson's ' Mechanics of Fluids,' Weisbach's ' Mechanics of Machinery 

 and Engineering,' D'Aubuisson's ' Hydraulique,' Geniey's ' Essai sur 

 les Moyens de conduire et elever les Eaux,' Darey, ' Sur les Fontaines 

 Publique* de la ville de Dijon.' Dupuit's ' Essai sur la conduite et la 

 distribution des Eaux,' and dispersed throughout the various Bluc- 

 Books and Parliamentary Evidence upon the subject of town water 

 supplies, much information upon the practical details of that branch of 

 the municipal service is to be found. Unfortunately, there is no work 

 in English, treating this subject exclusively, which can be considered 

 to be of any value ; and the reader cannot be too seriously warned 

 against accepting, absolutely, any of the doctrines lately promulgated 

 here " by authority." The French writers upon hydraulics are still 

 those who are to be the most implicitly followed in matters of theory ; 

 the practice of the best English engineers in matters of working detail 

 must be consulted, in epite of the official censure passed by a class of 

 empirics who seem to have objected to eminent engineers solely because 

 they were eminent. Dwyer's ' Hydraulic Engineering,' Neville's ' Hy- 

 draulic Formulas," Downing's ' Practical Hydraulics,' and Beardrnore's 

 ' Hydraulic Tables,' may also be consulted with advantage. 



W ATElt- W H I .ELS. The machines, by means of which the weight, 

 or the impulse of water, is converted into circular, vertical, or hori- 

 zontal motion, are known in mechanics by the name of u-ater-ichetln ; 

 and as the power ti)us employed is furnished by nature, and requires 

 but little outlay to be rendered available, these macliines have at all 

 times attracted much attention from the manufacturing interests. 

 They are of various descriptions, according to the conditions under 

 which the waters flow, or the uses to which the power thus converted 

 is t<< be applied ; but they are all alike in this respect, namely, that 

 the motion they receive is always circular, whereas in the other 

 modifications of water-power, the motion is rectilineal, and alternate. 

 Water-wheels are in fact subdivided into those with floats or blades; 

 and those with buckets. The wheels with floats are divided into 

 the cla-scn which have either straight or curved floats; and into 

 those working in free water, in races, or water troughs either straight 



or curved. The bucket-wheels may be adapted to receive the water 

 at the summit, or at an intermediate point of their height ; hut 

 the float-wheels are exclusively of the kind known as the undershot- 

 wheels, whilst the bucket-wheels are either overshot- or breast -wheels; 

 the latter distinctions depending upon the height at which the water 

 strikes the wheel, for in the undershot-wheels the water acts below the 

 horizontal line passing through the centre of the wheel : in the over- 

 shut-wheel it acts above the said horizontal line, and on the downside 

 (to the current) of the vertical line passing through the centre : and in 

 the breat-wheel the water acts at a variable angle above the horizontal 

 line through the centre, but on the same side as the stream flows 

 naturally. In addition to these are the horizontal wheels, which are 

 either set in motion by an isolated vein of water, or are placed in a 

 cylinder, or are placed around a cylinder conducting the water, in the 

 manners already described under TURBINES. Sometimes a modifica- 

 tion of the overshot-wheel is used, under the name of the ba<laliot- 

 icheel, in which the water is carried beyond the summit, and thence 

 returns to strike the wheel at a point situated a little below that level, 

 on the upper side of the vertical line passing through the centre of the 

 wheel. 



The parts of a water-wheel and its adjuncts which it may be 

 desirable to define, are as follows. In the water channel there is, 

 generally speaking, a mid-head, with tumbling bay and waste weir to 

 regulate the supply of water to the fore-bay, or the channel leading the 

 water directly upon the wheel ; this fore-bay has a hatch, or sluice, by 

 means of which the quantity of water falling upon the wheel can be 

 regulated at will. The mill-race is the part of the channel immediately 

 under the wheel ; the tail-bay is the part by which the water escapes 

 after it has produced its effect. The wheel consists of a shaft, upon 

 which are fastened the arms, bearing in their turn the periphery, to 

 which are attached the floats or the buckets ; sometimes this periphery 

 is close boarded, or soled, sometimes it has openings for the purpose of 

 ventilating the buckets ; the sides of the bucket* which keep the water 

 upun the wheel are called the shrouds. The motion is taken off from 

 the wheel either by gearing working upon the segments of the wheel, 

 or by first motion, or bevilled wheels fixed upon the axle ; the last are 

 generally known by the name of pit-wheels. 



Formerly the vertical wheel, with straight floats working in a straight 

 mill-race, was the description of undershot-wheel most generally 

 adopted, but it is now seldom used, unless in cases where there is an 

 abundance of water, and a fall not exceeding five feet (fig. 1.) In 



Fig. 1. 



these wheels, the water acts entirely by its shock, and evidently this 

 must be proportionate to the velocity with which it issues from the 

 hatch, under the pressure of the head in the fore-bay. The distance 

 between the hatch and the wheel must therefore be made as small as 

 possible, because the water in spreading out in the mill-race is exposed 

 to lose a portion of its velocity. The fore-bay should be made with 

 converging sides, upon the principle of ordinary conical ajutages, wider 

 towards the dam than to the sluice ; and from Poncelet's experiments, 

 it would appear that a great increase of useful effect is obtained by 

 making the hutches incline, so as to offer an angle, towards the darn, 

 of 45. Immediately beyond the centre line of the wheel, the race 

 must fall away, so as to leave a more uninterrupted discharge into the 

 mill tail ; its width must be regulated by the quantity of water to be 

 discharged, because it is found practically that the depth of the stream 

 ought not to exceed 10 inches when the course is clear; the depth 

 also should never be less than 6 inches, and in order to lose as little 

 of the water as possible, the space between the outer edge of the wheel 



' and the mill floor, should not be more than 4 or 3 ol an inch. In the 

 must carefully constructed mills at the present day, a great improve- 

 ment in the efficiency of the wheels is obtained by giving an inclination 

 to the Hoor of the race from the hatch, to the level of the lower edge 

 of the second float on the upside of the vertical diameter, of about 1 



I in 12, or 1 in 15; the bottom then curves away from that point, con- 



, centrically to the wheel, until it meets the vertical diameter line 

 prolonged ; and it then falls away with a sudden drop of 4 inches, and 



every precaution is taken to ensure the rapid withdrawal of the tail- 



| water. The width of the race is made somewhat smaller than that of 

 the floats until a short distance before the position of the wheel ; and 



j beyond the centre line it widens out still more than the width of the 

 floats. 



As the water, on escaping from the hatch, heaps up against the float, 



| the latter must be made deeper than the normal thickness of the fluid 



