256 Mr. Mallet on ihe Physical Conditions 



would at length be found ranged round the interior circumference of the barrel, 

 leaving an empty cavity in the middle, in the line of the axis. 



218. If we are to seek for future great extensions of our power, of producing 

 vast masses of malleable iron (for whatever purposes) that shall give greater 

 assurance of internal soundness, and preserve in the large all the quahties of uni- 

 form and determinate disposition of fibre, — in a word, all the valuable qualities of 

 the best wrought-iron, as now known in small bars, — it must be by some vast 

 extensions or modifications of the rolling process, accompanied by such improve- 

 ments in the furnaces and modes of heating, as shall enable the largest masses of 

 prismatic forms, to be produced out of more slender rolled bars, laid or " fag- 

 goted," and heated together, and at one welding operation, rolled (or otherwise 

 pressed in the same constant direction at successive points) into one gigantic bar 

 which, for artillery, might be then twisted by suitable machinery, such as that 

 patentedbyMelling. Tothe subsequent operations of bending, cutting, or shaping 

 such prismatic masses, however, so as to fit them, on a large scale, for the many 

 general purposes, to which forged pieces or " uses," as they are called, are now 

 applied, narrow limits of practical disadvantage and difiiculty can be foreseen ; 

 and as regards the fabrication of artillery, it scarcely admits of doubt, that the 

 limit of useful size has been already far surpassed, and that it is to a slcilful and 

 judicious combination of parts, each formed of malleable iron of moderate and 

 manageable dimensions, rather than to forging in one huge piece, that we should 

 look for the production of guns of the largest class in this material. We shall 

 return to the consideration of the best modes of attempting this hereafter. 



26. — Change of Crystalline Axis in Wrought- Iron^ Cold. 



219. Much has been loosely written of late years, on the supposed "loss of 

 fibre," and change to a confusedly crystalline structure, in wrought-iron, by the 

 mere effects of long-continued jarring or vibration, or very slight bending to and 

 fro at ordinary temperatures, — many affirming stoutly the fact, but without 

 bringing forward any instance or experiment that amounts to proof, and others 

 denying it, asserting in explanation, that in the instances adduced the " crystal- 

 lized iron was never fibrous," and which very probably has been the fact in 

 most of the cases adduced. 



