Proceedings of Learned Societies. 317 



air, in passing into the fluid metal, divides itself into innumerable 

 small globules, which pervade the whole of the metal. As atmo- 

 spheric air contains oxygen, and fluid cast iron contains about four 

 per cent, of carbon, it results that the oxygen of the atmosphere at 

 once unites with the carbon of the iron, producing an intense com- 

 bustion. By this means a very rapid increase of heat takes place. 

 The iron thus acquires a continual increase of temperature until it 

 arrives at a point hitherto wholly unknown in metallurgical opera- 

 tions. The greatest heat of our furnaces only suffices to render 

 malleable iron sufficiently soft to be indented with the heavy blows 

 of a powerful hammer ; but in this process the temperature is so 

 immensely increased beyond that point as to retain the malleable 

 iron in a fluid state. While this increase of temperature has been 

 going on, the large quantity of carbon present in cast-iron, to which 

 it owes its black and brittle character, is removed ; and when the 

 whole of the carbon has been thus eliminated from the metal, a 

 known weight of carburet of iron — i. e., pig-iron of a pure quality 

 — is added, so as to restore such an amount of carbon as will con- 

 stitute steel of the desired quality. The metal, after this admix- 

 ture, is poured into a casting ladle, and run into moulds. By this 

 means blocks of steel of any desired shape or size are rapidly made. 

 The steel in a heated state can be taken to the rolling-mills or 

 hammers and then fashioned in the ordinary manner. 



An interesting paper was read in the chemical section on the 

 action of light on sulphide of lead, having especial reference to the 

 preservation of paintings in picture galleries. Dr. D. S. Price 

 found that white lead pigments were not darkened by sulphuretted 

 hydrogen except where they were shielded from the direct action of 

 light, and he also ascertained that a white painted board that had 

 been exposed to sulphuretted hydrogen until it had acquired a dark 

 brown colour, was bleached in eight days by exposure to light, and 

 that portions covered by opaque objects remained unchanged in 

 colour, and that those parts protected by coloured glasses were pro- 

 tected from the bleaching action of the light in proportion to the 

 opacity of the tint. 



Dr. Price also found that the bleaching effect of light or 

 darkened white lead was much more strongly marked when the 

 pigment had been mixed with drying oils, as is the case in oil 

 paintings, and that when employed in water-colours the effect is 

 slower and less decided. In order to show the advantageous effect 

 of light in the preservation of oil paintings, Dr. Price had a picture 

 painted, and then exposed it to the action of sulphuretted hydrogen 

 till it became much discoloured, and apparently destroyed. Strips 

 of dark paper were then secured across the picture so as to cover 

 some parts, and it was exposed to light for a long time. The parts 

 of the picture exposed were perfectly restored to their original 

 appearance, but those protected by the paper remained deeply dis- 

 coloured and obliterated. 



From these experiments Dr. Price came to the conclusion that it 

 is most advantageous to have picture galleries well lighted, especially 

 in towns were the air is charged with sulphur compounds, and that 



