TRANSACTIONS OF SECTION G. 769 



pumping, leaving until later the consideration of its distribution, which, after it 

 leaves the service reservoir, is common to both gravitation and pumped water. 



Pumping supplies may be divided into two sections — first, those where the 

 water is drawn from a source only slightly below the level of the pumping engines, 

 such as where the water is taken from a stream or lake, or from culverts formed 

 in gravel beds, or is discharged from impounding reservoirs situate at too low 

 a level to enable the water to gravitate to the point of distribution ; and secondly, 

 where the water is raised from deep wells sunk in the sandstone, chalk, or other 

 water-bearing strata. 



In the first-mentioned cases the water has usually to be filtered, when it is 

 generally found convenient to place the filter-beds at the pumping station, the 

 water being firstly lifted (unless it will gravitate) on to the filter-beds, and 

 secondly, after filtration, and by means of a separate pump, forced through pipes 

 up to the service reservoir whence it is to be distributed. 



In the case of deep wells, the water seldom, if ever, requires filtration, and is 

 usually raised either directly or through pipes into the service reservoir, the total 

 lift being frequently divided between lift pumps and force pumps with the object 

 of balancing the work to be done by the engine. 



Sometimes the well alone will yield a sufficient supply of water, but often 

 it has to be aided by boreholes or by drifts or headings driven horizontally in the 

 water-bearing strata near the level of the bottom of the well, and occasionally 

 continued for a considerable distance, even as much as a mile or more from the 

 well, the length of the headings depending on the quantity of water which can be 

 profitably obtained from them, and also on other considerations too various to 

 be mentioned here. There are cases in which it is possible to obtain sufficient 

 water by boring from the surface of the ground and lowering a pump down the 

 borehole. The expense of a large weU is thus saved, but it is, of course, 

 impossible to augment the supply by drifting. 



The time at my disposal will not admit of any observations on the merits of 

 the various kinds of engines and pumps employed in raising water ; they are not 

 only very numerous, but each has to be considered in relation to its suitability for 

 the particular circumstances of the case in question. Suffice it to say that, although 

 most of the water pumped in the United Kingdom is raised by means of steam 

 engines, water turbines, gas engines, oil engines, and (to some slight extent) 

 electric motors are also employed. It may be mentioned that one of the largest 

 oil engines in this country is engaged in pumping water from a deep well, and it 

 is not improbable that gas and oil engines will in the future become more largely 

 employed for waterworks purposes. 



It should here be mentioned that there are a few instances in this country, 

 and many in the United States of America, in which a service reservoir is 

 dispensed with, and water is pumped directly into the main and distributing pipes 

 of the district to be served, a method which, although employed with success 

 should not, in my opinion, be adopted where the circumstances admit of the use 

 of a service reservoir. Where direct pumping is used, provision must be made to 

 ensure continuous pumping day and night without intermission, so as to avoid 

 interruption to the supply of the district, and the speed of the engines must be 

 constantly varied to meet the demands of the consumers for the uaoment. The 

 maintenance of uniformity of pressure in the main pipes may be assisted by the 

 employment of large air vessels, or by accumulators such as are used for the 

 supply of hydraulic pressure, or preferably by a combination of air vessels and 

 accumulators. 



We will now return to the service reservoir. When this reservoir is situate 

 between the source of supply and the district to be supplied, it receives the wliolo 

 of tlie water and delivers it into the district as needed for use ; but when the 

 district lies between the source and the service reservoir, it receives the excess of 

 supply over consumption, and on the other hand makes good any deficiency during 

 those hours when the consumption exceeds the supply. In either case tliis 

 reservoir has the effect of equalising the flow from the source to the reservoir 

 throughout the twenty-four hours of the day. 



1903. 3 D 



