454 THE SCIENTIFIC PAPERS OF 



internal core, but the difference between the original and final 

 diameter would depend upon the temperature to which it had been 

 heated in the interval. He would undertake to take a ring of a 

 certain diameter, and by the mere treatment of heating and in- 

 ternal cooling increase the diameter to an extent very considerably 

 exceeding the external diameter of the tube upon which it was to 

 go. Therefore, he would submit that the temperature to which 

 the rings were heated should be adjusted to the greatest nicety, in 

 order to ensure the condition upon which the safety of the gun 

 depended. The subject of " Physical changes occurring in iron 

 and steel at high temperatures " was brought before the Iron and 

 Steel Institute by Mr. Wrightson, one of their members not long 

 ago,* and the conditions there referred to applied very forcibly to 

 the case now before them. 



The paper under discussion went on to describe the process 

 followed at the Gun Factory to make the steel they used. The 

 apparatus there employed consisted of two things, a furnace, stated 

 to be Price's patent retort furnace, and a process called the open- 

 hearth process, but which was in reality as minute a description of 

 the one known by his name as though it had been taken from the 

 instructions which he was in the habit of sending out to his 

 licensees, and in accordance with which nearly half a million tons 

 of steel were annually produced in this country. Price's furnace, 

 it was stated, differed from the regenerative gas furnace in having 

 a retort gas-producer, and of that a considerable point was made. 

 He had with him a sheet which he had taken out of a patent he 

 had obtained as early as 1863, describing a very similar gas- 

 producer ; and if Colonel Maitland was present he should like him 

 to point out the essential difference, if any, between the two. 

 Although Dr. Siemens had used the retort gas-producer for some 

 time, he had come to the conclusion many years ago that it was 

 not productive of the best results ; that, in order to convert coal 

 into gas of the greatest heating power, it should be acted upon 

 energetically, so as to attain the highest possible temperature at 

 the point where the carbonic acid took up another equivalent of 

 carbon to form carbonic oxide. He felt inclined to challenge the 

 Department to make a comparative experiment, using their furnace 



* "Journal," No. II. 1879, p. 418, and No. I. 1880, p. 11 et seq. 



