The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks.

  • Notter, J. L. (James Lane), 1843-1923.
Date:
1900
Catalogue details

Licence: In copyright

Credit: The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

    32/1146 (page 10)
    Kain-water is very soft, owing to the absence of salts of lime and magnesia ; it is therefore good for washing or cooking purposes, although it is less palatable than other kinds for drinking. The amount of water given by rain can be easily calculated, if two- points are known, viz., the amount of rainfall and the area of the receiving surface. The rainfall can only be determined hy a rain-gauge (the mode ot constructing which is given in the chapter on Meteorology) ; the area ot the receiving surface must be measured. The following formula is the one generally used :— Aren in square feet x 144 x rainfall in inches _p„^^;p fg^^.. ^728 Cubic feet x 6-23 = gallons. Cubic inches X -003607 = gallons. The calculation may be much simplified by multiplying the area of receiving surface in square feet by half the rainfall in inches, the result is. in gallons ; here the error is only about 4 per cent. To calculate the receiving surface of the roof of a house we must not take into account the slope of the roof, but merely ascertain the '^^ea of the flat space actually covered by the roof. The joint areas of the g^ound-fl^^^^^^ rooms will be something less than the area of the roof, which also covers, the thickness of the walls and the eaves. ^„r^^^n^■ In most English towns the amount of roof space for each pe^;^^ be estimated higher than 60 square feet and m some P^^ ^^^^f^^^^^^^^^ less. Taking the rainfall in all England at 30 inches, and a sum g that all is saved, and^that there is no loss from evaporation, ^^^^^^^f ^^^S ^^^^^^^^ for each person would give 935 gallons, or 21 gallons a day. ^ut as tew town houses have any reservoirs, this quantity runs ^^ S;«=^\.Pf ^Vsu^^^^^^^^^ in urban districts. In the country it is an /^f ^^/^i/^^^;/Jj^^^^^^^^^^ being stored in cisterns or water-butts. If instead of ^^^^ ^^^^^f JJ^^^'^^^^ the receiving surface be a piece of land the ^^^^^^^^^^^^^ the same ^vay It must be understood, however, that th s is tne tocai tue same way. xu mu»u available; some wiU will vary with the soil .and the season from the one-hall to se^ en ei„nin5. ^^'tI^ ™.tTon'L>e by the available to the tofal rainfall varies very mncrbehTiSeSV /p^ity of the '^'-^yZ^^S^a^l porosity of the soil, the steepness » f ^^^^J^ST'^^^^^ air, r tSt^»S En^ana rrcirc„n.sta„ces. The following Sfof pound and available proportion of total rainfall Steep surfaces of granite, gneiss, and slate, nearly • • ^.^ ^.g Moorland and hilly pasture, from • • ' , 0*5 to 0-4 Flat cultivated country, from . - • ' q Chalk, J Of) n T One inch of rain deliver ^6^3 g^^onB c,n^^^^ gallons (101 tons by weight) on each squaie acie. = millions of gallons per sfpiare mile ^^^^ .^^^