PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 403 



then mixed with mercury. He should not consider the fact that 

 it was to be subsequently formed into an amalgam as doing away 

 with his objection to the broad terms of Dr. Wood's patent. 



STEEL CANNON AND THE NATURE OF STEEL. 



Prof. Seely said that it had been supposed, until recently, 

 that certain barbarians knew, practically, more about the manu- 

 facture of steel than we do, and that there were certain lost arts 

 with reference to steel. There has been much doubt among 

 scientific men as to what steel really was. During the present 

 century, and until within ten years, steel has been considered a 

 carburet of iron. Some ten years ago, an Englishman by the 

 name of Binks, showed conclusively, that nitrogen is necessary 

 for the production of steel. He did not show plainly that there 

 is nitrogen in steel, but showed that we knew no way to produce 

 steel without bringing nitrogen in contact with iron. He put 

 pure iron into a porcelain tube with carbon, and heated it long 

 enough to produce steel, under other circumstances. But he 

 could not obtain steel ; the carbon came out carbon, and the iron 

 was as soft as when put in. He tried various elements, with car- 

 bon, and found that he could produce no steel except when nitro- 

 gen was present; while, if nitrogen was present, no matter in 

 what shape, whether as a simple gas, in atmospheric air, or in 

 organic compounds, steel was invariably produced. The amount 

 of nitrogen in steel is so small that it cannot be detected by the 

 most expert chemists. It is less in weight than carbon, and the 

 carbon is less than. one per cent, generally. Steel is therefore a 

 compound of iron and carbon, and probably nitrogen ; certainly 

 nitrogen must be present in its formation. The credit of this 

 discovery is due to Mr. Binks, although within the last year two 

 or three Frenchmen have obtained all the glory of it. 



Cast iron and steel are nearly the same thing, chemically. 

 Pure iron melts with great difficulty, and hence other matters 

 which melt at high temreratures mix wath it. Silicium, sulphu- 

 rets of iron, phosphurets of iron, alumina, and other substances, 

 combine with it. Cast iron is a mixture of steel with all kinds 

 of impurities. It usually contains a little more carbon than 

 steel. The more carbon it contains the more fusible it is. For 

 ordinary purposes steel is not required to have much fusibility, 

 especially as this property is obtained at the cost of others more 

 useful. Cast iron may be made having precisely the same 

 amount of carbon and nitrogen as any steel ; yet, it would not 



