8o 



THE HOUSE AND ITS EQUIPMENT. 



poisonous nature of the gas ; hence, special care required to ventilate power-room, and producer is best 

 placed out of doors with only a roof over. Producers for small sizes not very satisfactory. 



Public Gas. Advantages : No expense except when running engine. Easily and promptly started. 

 No plant but engine required. A minimum of first cost. Will run well on small powers. 

 Disadvantages : Public gas often expensive, but usually cheaper than a lamp oil engine. 



Electricity. Advantages : Fairly cheap if made on premises for lighting. Motor started any time 

 and from any distance. No cost when standing. Disadvantages : The high speed requires special gear 

 for reduction. Current apt to be expensive if purchased from an outside supply. 



Water. Advantages : Costs nothing for motive power. Disadvantages : May dry up in summer 

 or freeze in winter. May cost a considerable amount to build dam or other head works. 



Wind. Advantages : Costs nothing for motive power. Disadvantages : Mill expensive. Power 

 intermittent ; large storage capacity necessary. 



In Fig. 113 is shown an approximate section north and south through London, in order to 

 illustrate how the rain falls on the high ground of Hampsteacl Heath at H and sinks down until it is 



stopped by the 

 London c 1 a y C, 

 which lies below 

 the capping of 

 B a g s h o t sands 

 which form the 

 gravelly Heath. 

 The water thus 

 caught on the clay 

 travels along the 

 junction until it 

 issues at S in the 

 finally as the river Fleet, 



113. SECTION OF LONDON SOIL. 



form of the springs which produce the ponds in Parliament Fields and issue 

 which flows into the Thames, T, at Blackfriars Bridge when in flood only. 



Now there are many parts of the country where no water can be got from wells of any reasonable 

 depth. This is the case over large areas of &quot; clayey &quot; Essex. A house may, however, produce its own 

 imitation of Hampstead Heath. Every acre of ground receives 100 tons of water annually for each inch 

 of rainfall. Taking a household of ten persons at 2Ogal. each per day, this amounts to 326 tons annually. 

 Allowing it to be possible to save 14111. of the rainfall of Essex, which amounts to 2401. annually or there 

 abouts, then one-fourth of an acre would yield 350 tons per year. That is to say, the household named 

 could be supplied from an area of 

 ground 4oyds. by 3oyds. Selecting 

 this at the highest point, the 

 ground would be stripped and 

 levelled and covered with a layer of 

 concrete suitably channelled to a 

 central channel of half tiles. The 

 whole area would be covered as 

 deeply as expense would allow with 

 clean sand, or gravel, fenced round 

 to keep off animals, and a suitable 

 tank would be sunk in the ground to 

 contain the water which would filter 

 through the sand. There are many 

 localities where such a scheme could 

 be easily arranged, and if low cost is a consideration and rough water for rough purposes is available, the pure 

 water-collecting area may be reduced to that necessary for potable water only, or for that for the toilet. 

 Such a plan is at least well worth consideration in localities where, as over so much of Essex, a well must 

 pierce a great thickness of London clay to reach the chalk, and the water-level may then be far down. 

 Such a bored well may be very expensive. No underground water-level in its natural condition can ever 

 be so far below the surface as the sea-level. All the fissures of the earth s crust must be full of water to 

 that level. By prolonged pumping, however, the level may be reduced, as it has been in London, where 

 the artesian water-level is now far below sea-level. Were not the chalk outcrop under the sea well 

 puddled over with clay, there would long ago have been an influx of the sea into the chalk below London. 

 This is a risk to which these low-pumped London-bored wells stand constantly exposed. 



It will naturally be suggested to the mind that any pumped water supply will require some amount 

 of storage capacity, for it is not desirable to work a pump continuously, and storage sufficient to tide over 



IIJ. SECTION AT BENNETS END. 



