indicating Means far its Prevention. 151 



we have no need of the valve, but in its stead a cock only, 

 as at e ; for, when the water ceases to flow from D through 

 G into the cistern H (the cock G still remaining open), it 

 is plain that if the cock e be opened, the upper syphon DEG 

 will empty itself at <?, the lower orifice of its longest leg, 

 the air entering at the upper and open cock G allowing of 

 the same. 



The principle of the whole is too plain to require further 

 comment; and any person of ord.nary ability, acquainted 

 with the actual course of a pipe, would be at no loss to 

 apply it to any system of pipes however complicated ; only 

 remembering that the portion of pipe included between the 

 street and the cistern must become a syphon, (either by the 

 application of an air- valve at D when the cistern is at a 

 lower level, or a cock when at a higher,) air entering at 

 a higher portion of the pipe, (whether through a valve iri 

 the former instance, or the cock G in the hitter,) and hence 

 allowing the contained water to flow out at any aperture 

 lower than any point or curve formed between*. 



With regard to in-door situations, including the pipes 

 leading from the cistern downwards to the Various apart- 

 ments of the house, I cart scarce conceive it requisite to be 

 at any pains respecting them, as the frost must be intense 

 indeed to freeze the water contained in them, not only on 

 account of their less exposed situation, but also because the 

 occasional drawing of water from the cocks at the extremi- 

 ties of the pipe, carries down, by the rushing motion of the 

 water, any small particles of ice that may have begun to 

 form : but in cold aspects the same principle is easily ap- 

 plicable, placing a cock immediately at the side of the cis- 

 tern, as at f, and an air-valve directly beyond it. By this 

 disposition you are enabled, bv first closing the cock f, and 

 then opening all the cocks at the extremity, to empty the 

 pipe either every night on going to rest, or once or twice 

 during the day, as the rigour of the season and degree of 

 exposure may indicate ; but the chief utility of the plan is 

 the ensuring the constant supply of water into the cistern j 



* When the ciste-n is at a higher level, if an intermediate curve 

 should Unavoidably fall lower than the level of D the supplying tube, the 

 pipe must be either divided into two syphons bv placing an air-va;ve ate 

 D, and a cock at the lowest part of tie curve as at E (hg. a.), or else the 

 whole length may be formed into one syphon bv placing a sio;>-cock at D, 

 and a descending pipe imn.ecliat.elv beyond it, the orifice of whxh mist 

 be lower thin the level of the inttnv.ediare curve E . then, fir-r c'osing 

 the stop-cock at D and opening the lower one g, the syphon G i^D g will 

 empty itself at g ; the lower aperture of its longest leg. . 



M 2 exclusive 



