226 
Village Sanitary Economy. 
and store roof-water. The cjuantity and quality of the water to be 
obtained from the roofs of buildings, when the covering is slate, 
has not been generally appreciated. In the cases of thatch and. 
tiles, the same remark does not apply, as much of the rain is ab- 
sorbed by the roof itself, and that which is thrown off is not so pure 
as that discharged from slate roofs. Taking an ordinary middle- 
class house in a village, with stabling and outbuildings, the space 
of ground covered by the roofs will frequently reach 10 poles ;. 
while the space covered by a farm labourer's cottage and out- 
building will be 2J poles. Assuming that the roof is slate, and 
the water dripping from it is properly caught by eave-troughing 
and conducted by down-pipes and impervious drain-pipes into a 
watertight tank, sufficiently capacious to prevent overflow under 
any circumstances, and that by this method 20 inches of water 
from rain and dew is collected in the course of the year, the 
private house will have the command of 28,280 gallons, and 
the cottage 7,070 gallons in a year. To make it clear that this 
quantity of water can generally be obtained, it should be stated 
that the proportion lost by evaporation, &c., from a slate covering 
will not exceed one-sixth of the total quantity of rainfall with the 
deposition of dew added, which, together, may be taken at an 
average of 24 inches. The quantity of water due to an inch of 
rain falling upon every pole of surface is 141-;^ gallons, which, 
if multiplied by 10, the number of poles covered by the roofing 
in the one case, and by 2i in the other, and again multiplied by 
20, the number of inches of rainfall and dew collected, we arrive 
at the quantities stated. From such a supply an average daily 
quantity of 77-pi„ gallons for the house,* and lO-fV gallons for the 
cottage, will result. These respective quantities would not be 
sufficient for all purposes, but they would form a very good 
resource in the absence of a more copious supply. To secure 
them, however, it would be necessary to have tanks to hold half 
the year's amount, so as to provide against those extraordinary 
seasons of drought which occasionally take place, and which in 
the year 1868 extended over three months without any inter- 
ruption. But a tank to hold even half the quantity obtainable 
from roofs would be considered so large and costly as only to be 
within the reach of the wealthy. A tank to hold 14,140 gallons 
would have to be 15 feet square and about 10 feet deep, while a 
tank for the cottage quantity of 3535 gallons would have to be 8 
feet square and 9 feet deep. The cost would vary with locality ; but 
the recent adoption of concrete for the walls of tanks, and the greater 
* The writer uses in his house roof-'n-ater only, and the daily gauged quantity 
averages 90 gallons. The driiiking--n-ater is filtered. Well-water is used in the 
stables, outbuildings, and garden. 
