272 Water Supply. 



It will be necessary to notice separately surface and subter- 

 ranean water, The former comprehends all water retained in 

 ponds whether natural or artificial, that received or collected 

 from roofs of buildings, stored in tanks and the like, or water 

 thrown from the surface of the soil ; subterranean water, all 

 that sinks below the surface, accumulates in permeable strata, 

 and thence issues in springs where vent is given to it. 



Surface-Water. 



First, as to water collected from the roofs of buildings. This 

 is obviously a simple process, requiring good and well-arranged 

 spouting, with sufficient tank-storage. In the construction of 

 farm-buildings where this supply is needed, it may repay the 

 outlay to increase the area of water-catch beyond the absolutely 

 necessary extent of roofing, and to adopt the covering from which 

 rain-water is most readily and copiously thrown. Thatched roofs 

 are beyond the scope of any calculation. Zinc, iron, lead, or 

 any metal, slates, hard-burned Staffordshire tiles, will throw off 

 the 'greater portion of all rainfall. Ordinary tiles, when dry, 

 absorb a considerable amount of water : a shower represented by 

 3-lOOths of an inch would be thrown from the surface of the first- 

 named substances and absorbed by a tile. This would be 

 repeated on the falling of every summer shower ; and a calcula- 

 tion based on the known daily rainfall of the summer of 1864, 

 allowing for only one shower on the days when rain was noted, 

 gives for the 5 months from June to October inclusive, an 

 aggregate loss of 1 inch of rain by the absorption of tiles, or about 

 25 gallons for every 100 square feet of roofing. 



If we take the Flemish Farm at Windsor — which is covered 

 with tiles — as an instance, the roofing may be estimated at 

 15,000 square feet ; there Avould then be a loss of 7500 gallons 

 of water, filling a tank 12 feet square by S feet deep. This may 

 seem a trifling quantity, but it would be of great value in some 

 places in seasons such as 1864. 



In retentive soils, tanks for cottages may be made at a small 

 cost by sinking casks into the ground, though brick-built tanks 

 will necessarily be cheapest in the end ; this is one of the im- 

 provements in cottage homes which never should be omitted, 

 even where well water is abundant. Open ponds, sunk into a 

 clay subsoil, will, at certain seasons, receive the soakage from 

 the surrounding soil ; even those which are artificially puddled 

 retain their water in a way difficult to explain when the natural 

 evaporation and artificial exhaustion by cattle and other uses is 

 taken into account. This phenomenon, for such it may be called, 

 is very remarkably illustrated by surface ponds on the highest 

 ridges of the chalk downs, known as dew-ponds. 



