involved in the Construction of Artillery. 279 



265. The first of these Tables (Table xiv.) embraces results sufficiently 

 ■within the limits of extreme experiments to be reliable in practice. The blanks 

 and interrogations in some of the columns, especially as regards gun-metal, indicate 

 how little the attention of experimenters has been directed as yet, to answer the 

 many important questions, needed to fix upon an exact foundation the principal 

 data for fabricating cannon of that material. (Note S.) TVe perceive, however 

 how completely the fancied superiority of steel, as a material for ordnance, 

 vanishes, on comparing columns 11, 12, 13, and 14; and that, with properly 

 proportioned guns under service charges, wrought-iron stands superior to all other 

 materials — three times stronger than gun-metal., four times stronger than cast-iron, 

 and about one-third stronger than steel; while at the ultimate strain of rupture, it 

 is not far below steel, double as strong nearly as cast-iron, and about a third 

 stronger than gun-metal ; the forces being in all cases impulsive. 



In Table xv. the general distortibility of the four metals, is compared with 

 cast-iron as unity ; and here again the superiority of wrought-iron is apparent. 



In Table xvi. various molecular conditions for the same metals are com- 

 pared, and as in the preceding Tables, the conditions of strength, so in this, 

 those of durability, and of those conditions in service, discussed in the earlier 

 part of this work, are put in comparison. 



266. While lastlj', in Table xvir , the results are brought to the test of money 

 value. We find that wrought-iron guns are more than five-fold as durable as 

 those of gun-metal, and twenty-two times as durable as those of cast-iron, without 

 taking any credit, whatever, on the side of wrought-iron, for the deterioration 

 of cast-iron due to mere repetition of discharge, as referred to in chap. 17 ; 

 while the first cost of wrought-iron guns (at a large estimate), is not more than 

 double, that now paid for cast-iron, and immensely below the price of either gun- 

 metal or steel ; and, taking first-cost and durability together., gun-metal cannon, 

 are about seventy-seven times, and cast-iron guns, about thirty times, as dear as 

 7crought-iron artillery. Again, the cost of horse-labour, or other means of transport 

 for equal .strength (and of course, therefore, for equal effective artillery power) is 

 above five times as great for gun-metal, and nearly three times as great for cast-iron 

 as for wrought-iron guns. This last consideration puts out of view, the assumed 

 necessity, for a determinate large dead weight in guns, for the mere purpose of 



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