indicating Means for its Prevention. 11&! 



in the most gradual manner, leaves the particles of such 

 substance in that equable state with respect to each other, 

 as proves, in the subsequent use of the article, the surest- 

 safeguard from casualties arising; either from change of tem- 

 perature or mechanical extension. Thus the durability of 

 feaden pipes, relative to the freezing of their contained fluid, 

 is proportional to their thickness, and the uniformity in the 

 yielding of each portion of the cylinder, which uniformity- 

 depends on the accurate and equable cooling originally ob- 

 served in their manufacture. 



The compression of air exerted by the mechanical im- 

 pulsion of the water, is another source of injury to 

 pipes : thus, before water flows into a cistern, a hissing and 

 undulating noise is heard for some time to issue from the 

 cock supplying such reservoir, occasioned by the flux and 

 reflux of air confined in the pipes, such air being urged to 

 escape by the engine, or height of the head of water, power- 

 fully throwing forward the water, whose progression is re- 

 tarded till the air before it is made to escape at various out- 

 lets. If no vent were any where allowed to this air, that 

 is to say, if every copper cock was air-tight as well as water- 

 tight, and each kept shut, the progress of the water would 

 be not only prevented, but weak pipes in many instances 

 would be burst by the mechanical power of the engine thrust- 

 ing forward the water, and therefore proportionally compres- 

 sing the air before it. Thus, in frosty weather, all pipes sup 4 

 plied by any powerful machine have a double hazard of rup- 

 ture from cylinders of ice retained in them, so closing the 

 v. -hole number as to prevent the escape of the air, more and 

 more compressed by violent alternate propulsions exerted in 

 the water. 



So long then as we remain unacquainted with any su!;h 

 stance conjoining, at ordinary temperature, elasticity with 

 the ductility and hardness of metals, we can scarce look 

 to other methods of preventing the freezing of water in 

 conduits, than by the radical resource of keeping them full 

 only during the short interval of supplying the cistern or 

 reservoir of each dwelling or manufactory. 



The air-valve here suggested for the purpose, as facile of 

 construction as its mode of action, bears with it its own 

 demonstration, consonant to the most simple of hydrosta- 

 tical laws, and in most situations applicable as a self-acting 

 principle, is delineated in fig. 3, wherein AB represents the 

 body of the valve formed of pewter; being of six inches 

 height, and having in the centre of it's summit a small hole 

 l-4th of an inch diameter. The upper cylindrical portion 



Vol. 19. No. 74. July 1S04. M A, 



