Iron ships, on the other hand, were found to be well adapted to withstand the racking stresses, the localized loads and the vibrations which were introduced by steam machinery; they were lighter than wooden ships, more capacious, more easily shaped to give the fine lines necessary for speed, cheaper and immeasurably stronger. In course of time the objections to them gradually vanished; by aid of the scientists the derangement of their compasses was overcome, the dangers from lightning were obviated, and the extent of the fouling to which their surfaces were liable was kept within limits. In course of time, in spite of natural preference and vested interest, and since the advantages of iron were confirmed by continuous experience, wood became almost entirely superseded by the metal for large mercantile construction. But in the case of warships, as we have seen, insuperable objections seemed to prohibit the change of material. No sooner had a step been taken by the Admiralty, in the ordering of a group of iron paddlewheel frigates in ’43, than an outcry arose; the wooden walls of England were in danger, the opponents of iron declared, and iron ships were wholly unsuitable for warlike purposes. More were ordered in ’46. Sir Charles Napier, whose opinion naturally carried great weight with the public, led the opposition, and when, in ’49, the artillery trial demonstrated the dangerous effects of shot and shell on thin iron plates, the advocates of iron were fain to admit the error of their opinions. The iron frigates were struck from the establishment and transformed--such of them as were completed--into unarmed transports. As experience with iron ships accumulated, the feeling grew in certain quarters that the artillery trials, the results of which had been claimed as being decisive proof of the unsuitability of iron for warships, might not have been the last word upon the subject. The events of the Crimean War tended to emphasize the doubt and uncertainty. A few there were who saw in that war clear proofs of the superiority of iron over wood; who argued that, though iron had proved to be dangerous in the form of thin plates in certain circumstances, yet it had shown itself to be impervious both to shot and shell, and indeed an indispensable defence in certain circumstances when applied in sufficient thickness; that thicker plates than those condemned as dangerous might therefore prove to be a great protection against shell fire; and that, even as regards thin plates, the splintering effect of shell against these was small, from all accounts, compared with the _incendiary_ effect of shell against timber. And in what other respects were the advantages of iron contested?