498 report — 1879. 



of a strength at least three to four times that of the strongest iron castings, the 

 importance of this experimental discovery can scarcely be over-rated. 



Nor must I pass over the application of these processes to the production of 

 boiler plates, bridge girder plates, and ship plates, in which, as a result of the 

 greater tensile resistance of such plates (reaching for ordinary uses a figure of about 

 twenty-eight to thirty-four tons to the square inch), the engineer is not only enabled 

 to lighten°his structure, but to expect from it greater durability — an expectation 

 not diminished by its greater capability of resisting corrosion, especially where 

 care is taken to exclude manganese from the mixture of the metals employed. 



For specific purposes, and where price is not so much an element of consideration 

 as great tensile or percussive resistance, a more costly mode of manufacture has been 

 adopted by Sir Joseph Whitworth, whose attention was probably drawn to the 

 necessity for obtaining sueh a metal, during the _ construction of cannon and tor- 

 pedoes, but which has now been extended to objects of a very varied character. 

 The method of manufacture, which has been in use upwards of ten years, is by 

 casting ingots under very heavy hydraulic pressures, from very carefully selected 

 materials, the result being the production of a metal of enormous tensile resistance, 

 reaching in some instances the high figure of 100 tons per square inch, while at 

 the same time the bubbles and air vesicles which sometimes appear in metal pro- 

 duced in the ordinary methods are entirely or almost entirely got rid of, and the 

 consequent striations and imperfections of internal structure and external surface 

 disappear. 



It is hoped that ere long we shall be able to procure in this way cylindrical 

 boiler plates rolled solid from the ingot, much after the fashion in which weldless 

 steel tyres are now obtained, and that the weakening of these plates by the existing 

 necessity for forming horizontal riveted joints may thus be avoided. 



It is desirable before closing this, I fear, already somewhat long address, to call 

 attention to the most recent development of the steel manufacture as exhibited in 

 the processes of Messrs. Snellus, Gilchrist, & Thomas, by which iron containing a 

 considerable proportion of say T44 per cent, of phosphorus, may, in the course of 

 its manufacture into either Bessemer or Siemens-Martin steel, have this deleterious 

 matter entirely removed, or reduced to an inconsiderable proportion. 



The method of carrying out this operation was exceedingly well described at 

 the recent meeting of the Iron and Steel Institute in London, and it was shown 

 that where such irons were melted in vessels lined with a slag having twenty per 

 cent, of silica and thirty per cent, of lime and magnesia, the phosphorus was 

 gradually and effectually absorbed by this lining, and a steel of good quality, com- 

 paratively free from phosphorus and silica, was produced. 



The result to the community will naturally be that, as henceforth a much more 

 extended area of our iron fields both at home and abroad will become available for 

 the production of steel, the use of that metal will be still further extended and its 

 price reduced mainly by means of the methodical researches of our scientific me- 

 tallurgists, and entirely independently of those accidental combinations which have 

 in less scientific days led to the adoption of new and improved methods in the 

 production of metals required by the progress of mechanical and economic science. 



Since writing the above address two other matters have been brought before 

 me which may, I think, be interesting to this meeting. 



One is the specification for the steel to be used in the construction of the great 

 railway bridge over the Forth, the plates for the main girders and braces of which 

 are to be of ' mild steel,' giving a tensile resistance of 26 tons per square inch of 

 section ; while for the rivets, not only is the same tensile resistance to be given, 

 but the minimum of elasticity is to be 16 tons to the square inch, and the 

 elongation before breaking not less than 25 per cent. 



The bars and rods, which are to be made from ' high-class steel,' are to have a 

 tensile resistance of 40 tons per square inch, and a minimum of elasticity of 20 

 tons, while the elongation is to be 12£ per cent, before breaking. 



It will be seen from these figures that not only will the structure itself be 

 enormously lighter than if materials such as have been hitherto employed for such 



