SIX WILLIAM SIEMENS, l-.R.S. 



405 



1 1 solute strength of such steel is only twice as great as that 

 of iron, the girders themselves, if of considerable length, may be 



'(1 in section in a much greater proportion as compared 

 with iron, because a considerable portion of the duty of a 



inn girder consists in its having to carry its own weight. 



Blueing that weight to a half in taking advantage of the 

 extra strength of steel, a greater proportion of the total strength 

 Incomes available for carrying load, which latter being a fixed 

 i|iiantity renders a further diminution of scantling possible. It 

 is in consequence of this compound effect, resulting from the 

 use of high-class material, that its great advantage in large 

 structures arises, and it is difficult to assign the limit of size 

 which skilful treatment may not accomplish by its use. These, 

 however, would be exceptional instances, and the more important 

 question after all is : How does steel compare with its old rivals, 

 iron and wood, in ordinary construction ? I would venture to 

 say that the use of steel in certain portions of ordinary build- 

 ings is not only better and safer, but absolutely cheaper than 

 the use of such a material as wood. In using steel girders instead 

 of wooden beams in the construction, for instance, of a ceiling, 

 what is the comparison as regards efficiency and cost ? The 

 flooring, supported on steel girders, would be more permanent, 

 being both fire-proof and not subject to gradual decay ; it 

 would, moreover, if made as rigid as a wooden flooring, be four 

 to six tunes as strong when subjected to exceptional loads. As 

 regards price, granting the material would be dearer, we should 

 have to take into our calculation an element which is not at 

 once apparent. Whereas the depth of wooden beaming of suffi- 

 cient strength would be, say twelve inches, if constructed of steel 

 a depth of seven or eight inches would amply suffice ; and if we 

 were to repeat this, say five times in a house, a total saving in 

 height of two feet would be the result. Now comparing the cost 

 of the cubical contents in the structure built in the two ways, we 

 should find that in a house of an area of thirty feet by sixty, in 

 taking the price of construction of one cubic foot of capacity at 

 Is. 2d., without taking into consideration fittings and ornamenta- 

 tion, we should save 210, to be placed to the credit of the steel 

 girders. If allowance were made for this or even half of this it 

 would be found that the steel girder would probably be the cheaper 



