TANKS AND CISTERNS. 



519 



of brick or rubble stone ; and in it a man- 

 hole should be left, for the purpose of 

 cleaning out the tank at seasons when it 

 may be dry ; — or the walls may be built 

 with good mortar, and the surface covered 

 with cement a quarter of an inch thick, 

 or the whole may be covered with two or 

 three coats of coal-tar, as a cheaper sub- 

 stitute. In some cases tanks formed of 

 plates of cast or malleable iron, strongly 

 riveted together, may be found more 

 economical : these, if properly put toge- 

 ther, will require no puddling, and they 

 are certainly the best if placed on an in- 

 clined plane, or where much of their sur- 

 face is above the ground-level. Timber 

 is sometimes used ; but, from its liability 

 to decay, it is undoubtedly the dearest 

 material in the end. 



In counties like some parts of Caith- 

 ness and other parts of Scotland, and 

 Yorkshire, where pavement abounds of 

 almost any size, it will be found an 

 excellent and cheap material for tank- 

 making. We have several so construct- 

 ed, one of which we have already alluded 

 to in sect. Water. It is constructed 

 as follows : — The space being dug out 

 18 inches longer and broader than the 

 intended internal size of the tank, and 

 the same proportion in regard to depth, 

 a bed or floor of well-prepared clay is 

 laid all over the bottom b, fig. 736, 16 

 inches in thickness. Along the sides 



Fig. 736. 



and ends are laid square blocks of stone 

 c c, 4 or 5 feet apart centre from centre — 

 (this distance depends on the lengths of 

 the pavement to be used.) These blocks 

 are firmly set on, or rather in, the 

 puddle, and kept exactly level along 

 these tops. On these the pavement d d, 

 forming the sides of the tank, is set on 

 edge, and close-jointed at the ends : 

 puddle to the thickness of 7 inches is 

 rammed between their back surface and 

 the sides of the excavation, so as to make 



it solid, and impervious to water. The 

 same operation is carried on all round, 

 and up to the top of the tank — the pave- 

 ment being kept in its place during the 

 process by pieces of wood wedged tightly 

 across the tank, but not placed opposite 

 the joints, which should stand directly 

 opposite to each other, for the following 

 reason : As soon as the bottom and sides 

 of the tank are finished, and the puddle 

 fairly set and dried, iron stretchers e are 

 fixed, of a size and strength proportionate 

 to the width of the tank, palmed at each 

 end, the heels of the palms being let into 

 each piece of pavement about an inch, 

 and run in with lead. The flat part of 

 the palm comes exactly opposite the 

 joints, thus keeping the sides from 

 ever moving inwards ; and" as they meet 

 with a corresponding resistance from the 

 puddle and soil on the opposite side, they 

 cannot be displaced. As no such secu- 

 rity could be given the end pavements, 

 they are selected as long as possible — say 

 from 6 to 8 feet— which will suffice for 

 a large-sized tank, as its length may be 

 extended to any amount. These end 

 pavements are half-checked into the end 

 side ones, or they may be secured by 

 iron bats. It is not desirable to make 

 such tanks too broad, on account of the 

 great size of the pavement required to 

 cover them. The covering stones are 

 laid in puddle, as they are thus easily 

 removed for the purpose of cleaning the 

 tank : if closely laid, and the surface 

 over them covered with gravel, no dis- 

 agreeable effluvia will escape. In the 

 case of the one alluded to, we have 

 earthenware shoulder -jointed tubular 

 drain-pipes, 3 inches in diameter, laid 

 from within a few inches of its bottom, 

 provided with a stopcock, by which the 

 contents are made to flow to another 

 pavement-tank : from thence they are 

 carried to any distance by means of 

 flexible pipes, which can be shortened or 

 lengthened at pleasure. 



In the case of the above tank we have 

 not divided it as yet, although we are 

 aware of the utility of having two com- 

 partments — one to receive the drainage 

 of a town, farmyard, or even a dwelling- 

 house, which, as soon as the compartment 

 is full, is allowed to undergo fermenta- 

 tion while the other is filling, and so on 

 alternately. With such care do the Bel- 



