AMERICAN INSTITUTE. 643 



soft iron in right proportions, in the form of filings or turnings, 

 were mixed and subjected for a sufficient length of time to the 

 proper degree of heat, a portion of the carbon of the softer iron 

 would leave it, and combine with the harder, so that, when 

 melted, the whole would be of uniform quality, and constitute a 

 No. 2 iron. 



But this result cannot be attained, when pieces of several 

 pounds weight, of each quality, are thrown together into a fur- 

 nace, and melted down in the course of twenty or tliirty minutes. 

 In that case, the two kinds are mechanically mixed, it is true, 

 and tlie mixture may be so intimate, that neither the workman's 

 tool nor the chemisfs most powerful microscope can detect the 

 least inequality in its composition : but if exposed to air and 

 moisture until the surface is slightly oxidized, it will be seen that 

 the oxide, instead of being distributed over the surface in a uni- 

 form coating, as upon castings made from pig iron of uniform 

 quality, will appear in numerous small patches; and if these are 

 removed, shallow indentations remain, resembling marks pro- 

 duced by small pox. This effect is supposed to be produced by 

 the different galvanic conditions of the different qualities of metal, 

 which are only meclianieally mixed without being chemically 

 combined. 



Pipes cast from iron of this description, have frequently as 

 good an external appearance and stand the required proof, as well 

 as those made from the best No. 2 pig iron; but when acted upon 

 by water, an irregular oxidation begins, and exliibits itself in the 

 interior, in small patches and nodules, which in some cases, have 

 increased in number and size, to such an extent, as seriously to 

 reduce the amount of water passing through them. In some 

 large pipes, belonging to the Boston waterworks, the flow was 

 diminished from this cause twenty per cent in less than three 

 years ; and at the waterworks in Grenoble, in France, some of 

 the pipes were found, after seven years use, to be diminished iu 

 capacity, from the same cause, nearly one half. 



The cause of this rapid oxidation, appears not to have been sus- 

 peetedj until a conii^arati vely recent period; Mr. Faraday having 



