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15 J On the Freezing of JVatcr in leaden Pipes, 



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exclusive of the advantage it gives us of a command of a 

 pipe when requiring repair, without being obliged to empty 

 the cistern before the plumber can solder a rupture in the, 

 tube; as also the further resource of pouring down hot 

 water into the same, through the valve, to melt any ice that 

 may have been formed accidentally therein ; cylinders of 

 ice so contained w r ou Id be melted' by the water, because the 



!ead encircling such cylinders of ice would conduct the heat 

 Vom the boiling fluid, and the ice, now surrounded by a, 

 heated body, would gradually receive an augmentation of 

 temperature sufficient for its liquefaction. 



Pumps are less frequently found frozen than leaderi 

 ipes, chiefly because the water in the upper chamber of 

 ie pump is occasionally renewed and violently agitated by 

 the working of the piston at every draught of water, and 

 that, perhaps^ several times in an hour; and partly because 

 the Wetter raised from the well, being of a higher tempera- 

 ture than the external air, requires some time to cool to the 

 freezing point ; and also in the case of wooden pumps, the 

 thickness of the wood, as a bad conductor of heat, prevents 

 any speedy transmission of temperature from the water to 

 the surrounding air. 



The supply of water through the streets from the public 

 water-works is very rarely, if ever, obstructed by frost, how- 

 ever intense. The reason of this hinges on the fact, as 

 ascertained by accurate observers, that in this country the 

 temperature of the earth at two feet depth docs not mate- 

 rially diminish throughout the year, and is scarcely ever, 

 even in rigorous, winters, lower than 40° of Fahr. This is 

 about the depth at which the wooden pipes, running under 

 the street, are usually laid. We have therefore at all 

 times a certain supply from them in the severest seasons, 

 by placing plugs over orifices immediately in the pipes 

 themselves: it is only the smaller leaden tubes proceeding 

 from their sides that are usually frozen, and that not till 

 they emerge into such situations as to be unprovided with 

 that shelter from the cold which a stratum of earth, of two 

 feet in every direction, before afforded them. 



Mr. Boyle, after a fortnight's hard frost, found the same 

 to have penetrated only 14 inches depth; and at Moscow 

 the frost is never known to penetrate, in the most severe 

 seasons, more than two feet. Hales also found the earth at 

 two feet depth to be unaffected by the continued cold of 

 a rigorous winter. Exclusive of the non-conducting qua- 

 lity of earthy matters, there appears to 4}e a source. of heat 

 at about this depth, which diminishes as we proceed further 



till 



