Progress of Invention. 383 



turbing circumstances came into operation, but their influence was 

 calculated and allowed for. Thus the water absorbed, not only the 

 calorific, but 0*13 of the luminous rays also ; six sevenths of the 

 radiant heat and light of a flame are carried away by the heated air 

 — the amount being modified, however, by the intensity of the heat 

 and light. Light obtained from various artificial sources was 

 used ; and it was found that a flame, the intensity of which is equal 

 to that of a candle which burns 8'2 grammes of spermaceti per hour, 

 radiates per minute, light which, if changed into heat, would raise 

 the temperature of 4*1 grammes water, one degree Cent. It 

 has been calculated, from the results afforded by these experiments, 

 that the light emitted by the sun would lift thirty-five billions of 

 tons one billion of kilometres high per second, and that it would 

 raise the earth twenty feet in the same time. 



Ferrosum and Ferricum, — The striking difference between the 

 salts of the protoxide and those of the peroxide of iron has always 

 attracted the attention of chemists ; but, until recently, it was not 

 suspected that they were in reality salts of metals which, except 

 that they are capable of being converted into each other, are as 

 different as they could be. Berzelius first ascertained their sepa- 

 rate existence : he termed that found in the protosalts ferrosum, that 

 found in the persalts ferricum. These allotropic states of iron 

 are as different in their properties as the two varieties of phos- 

 phorus, or those of sulphur. Their atomic weights are not 

 the same ; that of ferrosum being 28, and that of ferricum 56. 

 The one combines with a single atom of oxygen, the other with 

 not less than three. Hitherto only ferrosum had been obtained. 

 M. de Cezancourt has demonstrated the existence of ferricum in the 

 metallic state ; and during his researches on the subject has dis- 

 covered facts which may have a serious influence on the iron manu- 

 facture. Before he proved the contrary, it was believed that cast 

 iron, steel, and wrought iron, differed only in the quantity of com- 

 bined carbon : although it had been observed that their properties 

 were not always in accordance with their constitution. Specimens 

 of cast iron of the very same composition are often very dissimilar 

 in quality and appearance ; cast iron and steel sometimes contain 

 the same elements in the same proportions ; specimens of steel and 

 malleable iron are found occasionally, of the very same composition. 

 M. de Cezancourt has ascertained that, in reality, the difference is 

 due to the degree of oxidation in which the iron exists in the ore. 

 The salts of the protoxide furnish one kind of iron, and those of the 

 peroxide another. Different ores will furnish different kinds of 

 iron or steel, according as they contain ferrosum or ferricum, or 

 both. Malleable iron contains a mixture of ferrosum and ferricum, 

 the ferrosum being changed by a high temperature into ferricum : 

 and its quality is dependent on their relative amounts. Steel, if 

 stable, and of a good kind, contains ferrosum and ferricum in the 

 proportion of their atomic weights ; and hence magnetic oxide of 

 iron will afford excellent steel. In black and grey cast irons, the 

 ferricum has abandoned, while cooling, the charcoal it dissolved 

 at a high temperature ; ferricum generally predominating in the grey. 



