662 SCIENCE PROGRESS 



is counterbalanced by the low cost of the motive power which is derived 

 from its use. The foot-valve at the bottom of the suction-pipe will require 

 periodical examination, as it is liable to become choked by the sand which 

 is silted into the well by the flow of water. If this is neglected the pump 

 will ultimately be put out of action, or the sand will be drawn up into the 

 barrel, and will damage the bucket-leather. 



The storage reservoir can be constructed either above or below the ground 

 according to the difference in level between the well and the highest draw- 

 off tap which has to be served. The maximum fall which can be obtained 

 should be given to the supply-pipe from the reservoir in order to expedite 

 the distribution of the water by gravitation. When the point of delivery 

 is at a higher level than the well, the water can be raised into an elevated 

 tank, which must be constructed at a sufficient altitude to generate the 

 necessary pressure. If this is impracticable the only alternative will be to 

 drive the water to its destination by mechanical means. This necessarily 

 increases the initial outlay as well as the working expenses, and should be 

 avoided if other arrangements can be made. 



Particular care should be observed when laying the pipe-line, especially 

 when it is of considerable length, as neglect may result in perpetual annoy- 

 ance through the interruption of the flow arising from air-lock. The pipe 

 should slope continuously from the reservoir to the house as far as possible ; 

 but if the contour of the land is undulating and precludes the possibility 

 of obtaining an unbroken fall over the whole distance, the inclination of 

 the pipe should be divided into sections with variable gradients, each pro- 

 ceeding in the same direction. When a rise is unavoidable, an automatic 

 valve should be inserted at the highest point, to permit the escape of accumu- 

 lated air which naturally collects at the apex of the angle formed by the two 

 sections of the pipe, and which, if not vented, might entirely obstruct the 

 flow of water in either direction. If the fall is continuous along the whole 

 line, the air is automatically vented into the reservoir, even though the 

 gradient varies, and no trouble can arise from this source. 



The construction of the reservoir can be carried out in brick, stone, con- 

 crete, or any other suitable material which can successfully withstand the 

 stresses to which it will be subjected. Concrete is peculiarly adapted for 

 the purpose, and i! carefully manipulated and reinforced with expanded 

 metal, will make a thoroughly strong and satisfactory job. The interior 

 will need to be plastered with a i-in. coat of Portland cement and sand to 

 prevent leakage of the contents, or considerable waste may take place. 

 Absolute security against percolation can be ensured if the cement is water- 

 proofed by the addition of 5 per cent, of " Pudlo" before it is used. This 

 closes the pores of the mortar and makes it quite impervious, and is an 

 effective preventive against the admission of foul matter from the soil out- 

 side, even when it is under considerable pressure. 



A small sand-filter, 4 ft. or 5 ft. square, can be arranged in one corner 

 of the reservoir by means of thin dividing walls. Openings should be left 

 at the bottom connecting with the main chamber, for the passage of the 

 water, which enters at the top and percolates downwards through the fil- 

 tering material. The most suitable filtering medium is clean, sharp gravel 

 of varying sizes, the largest being at the bottom, and graded to pass a f-in. 

 ring. This layer may be 1 ft. in depth, and should be covered with a number 

 of old slates laid loosely over the top to separate the pebbles from those of 

 a smaller grade. The intermediate layer, graded to the size of peas, will 

 need to be of a similar depth, and the top should consist of 18 in. of coarse, 

 sharp sand, which has been thoroughly washed to remove all dust and vege- 

 table matter. Sand filters are more in the nature of mechanical strainers 

 in their effects ; but, after being in use for some little time, a film is deposited 

 on the surface, which assists in arresting the passage of bacterial life. 



