258 Iron and Steel in the Construction of Ships and Bridges. 



amount that was practically limited ; and such was the imper- 

 fection of the machinery employed in moulding it to the forms 

 it was subsequently required to assume, that it could be worked 

 only in masses of a size which at the present day would be 

 considered utterly insignificant. The possibility of using it 

 on the present immense scale supposes a combination of cir- 

 cumstances which did not formerly exist, and which could be 

 brought about only by long- continued exercise of enterprise 

 and ingenuity. 



Iron is .the most generally diffused of all the metals. This, 

 looking to the ordinary economy of Providence, evidently 

 points to its wide-spread application. It is, however, one of 

 the metals most difficult of reduction. This arises from its 

 powerful affinities, which also cause it to be so extremely 

 perishable. The difficulty which attends the extraction of iron 

 from its ores prevented its use until long after mankind had 

 attained a considerable amount of civilization. Hence in pre- 

 historic, and even in the earlier portions of historic times, 

 recourse was had to metals which are still both scarce and 

 dear. Bronze was the universal substitute for iron; but, 

 though great hardness was imparted to it — greater, perhaps, 

 than is possible to us — its attendant brittleness, in some cases, 

 and a limited supply in all, placed very narrow bounds to its 

 application. Iron possesses a combination of good qualities 

 which, taken in connection with its abundance, causes it to 

 leave every other metal far behind, when there is question of 

 utility. 



One of the most valuable properties of iron — its capability 

 of being cast in moulds — and one which it still retains in its 

 best form, that of steel, was most probably unknown, and 

 most certainly was unapplied in former times. Cast iron, with 

 us, is far cheaper than malleable, and for a great variety of 

 purposes answers at least as well. But, by the modes of 

 manufacture anciently practised, it could not easily have been 

 obtained ; and were it even attainable with facility, the 

 methods of manipulating it, now employed with such succoss, 

 were then undiscovered. Casting iron is, with us, a very simple 

 operation : it could not have been so in former times, on 

 account of the difficulty of forming suitable moulds. This 

 difficulty has been entirely overcome, within a comparatively 

 recent period, by the adoption of sand, an improvement due 

 to a Welsh shepherd boy. The use of sand for the purpose 

 had been previously attempted, but without success : its gene- 

 ral application to this most important purpose afforded facilities 

 in the manufacture of cast iron which had been until then 

 unknown. 



Tho exclusive use of wood in the manufacture of iron, in 



