5 1 //? WILLIAM SIEMENS, F.R.S. 317 



care than iron. If extreme toughness was required, care must be 

 taken that the material was not put partially through a process of 

 lur.li'iiing or chilling, and that its chemical constitution w;is 

 uniform. The higher material required a higher intelligence to 

 <l-il with it, and it was not sufficient that the chemist, or the 

 manufacturer, should possess a knowledge of its characters under 

 dill'rrent treatments. The engineer, also, had to be thoroughly 

 conversant with its properties, and in giving his orders for a supply 

 of the material should make out a proper specification, defining its 

 chemical constitution and its temper. Sir Joseph Whitworth had 

 proposed a method of defining steel according to its two principal 

 qualities, toughness and strength ; he had one number signifying 

 strength, and another toughness, and combining these two expressed 

 the quality of the steel. That was a rule which furnished a fair 

 standard of comparison, and might be worked out with great 

 advantage. He had repeatedly heard it stated, that mild steel, 

 such as was used for engineering purposes, ought to be rejected if 

 it had an absolute strength exceeding 27 or 30 tons. Such a 

 limit was, he thought, objectionable because it stopped the road to 

 improvement. He considered it quite possible that steel might be 

 extremely tough, and at the same time possess very great tensile 

 strength. As an instance of this he would mention wire, which 

 had undergone the process of annealing in oil at a certain tem- 

 perature. He had lately had occasion to experiment on some steel 

 containing 0'4 per cent, of carbon, which, if properly annealed, 

 was extremely strong and yet sufficiently ductile ; if hardened, it 

 would take such a temper that it could be put into the form of 

 a punch ; and if drawn into wire, and annealed by passing it at 

 a certain temperature through oil, its strength rose from 35 tons 

 per square inch to about 100 tons per square inch. That was 

 an instance of one material presenting itself under very different 

 aspects, in consequence of slightly different modes of treatment. 

 Et was necessary that the engineer, in dealing with steel, should 

 inquire into these different conditions, and should insist upon the 

 utmost care being taken in order to bring the material really into 

 the condition which he required. Cast steel was produced in the 

 Bessemer converter, or in the open hearth of a regenerative gas 

 furnace, in masses of from 5 to 10 tons ; and absolute uniformity 

 could be obtained if all conditions were properly carried out. 



