230 ANNUAL OF SCIENTIFIC DISCOVERT. 



faccttes,} fer miroirtant, and in the smallest quantity in bar iron, steel 

 may be placed between these ; in none, however, is a constant pro- 

 portion between the iron and carbon maintained, and it is impossible, 

 therefore, to give an exact classification of the different sorts of iron 

 according to the quantity of carbon contained in them, which appear- 

 ed to prove that the combination of iron and carbon cannot be really 

 a chemical combination. We may not, however, infer from this that 

 the different conditions of this metal depend only on the larger or 

 smaller proportions of carbon contained therein, and this has been en- 

 tirely confirmed by a number of very interesting analysis made by 

 M. Fuchs of the different sorts of iron. Persons desirous of becoming 

 acquainted with the nature of various descriptions of iron, which dif- 

 fer so much in other respects, have, by merely directing their atten- 

 tion to the quantity of carbon contained in iron in its different states, 

 generally overlooked another essential property or consideration, viz., 

 the crystallization. M. Fuchs is of opinion that iron is a dimorphous 

 substance, presenting itself under two distinct general forms or sys- 

 tems of crystallization, viz., the tesseral and the rhombohedral (or its 

 modification, the hexagonal :) and consequently there may be said to 

 be two classification species of iron, which may be distinguished as 

 tesseral and rhombohedral iron, and which are sometimes combined in 

 different proportions. M. Fuch's experiments have proved decisively 

 that the malleable or bar-iron belongs to the tesseral crystallization 

 form, and it may be conjectured that all the malleable metals may be 

 classed under that system of crystallization. The crystallization sys- 

 tem of pig-iron is not so exactly determined, but it is very likely that it 

 belongs to the rhombohedral system, because facette iron particularly 

 is one of the perfectly brittle metals which generally belong to the rhom- 

 bohedral form. The difference between bar and facette iron is based not 

 only on the difference of the system of crystallization, but also in the 

 great difference between their physical and chemical properties ; such 

 as the tendency of the molecules of metal to burst, and become dis- 

 placed ; hardness, liability to oxidization, solubility, fusibility,* &c. 

 M. Fuchs is of opinion that steel is an alloy of tessaral and rombohe- 

 dral iron ; and he thinks that hardening and tempering consists only 

 in the transformation of all the molecules, or a portion of them from 

 one system of crystallization to the other; the rhombohedral iron 

 being predominant in hardened steel, and the tesseral in non-hardened 

 steel. Pogyendorf's Annalen. 



COKE FOR THE MANUFACTURE OF IRON. 



M. Calvert, in the Comptes Eendus, XXXV., communicates the 

 following respecting the manufacture of iron by means of coke. 

 It is well known to scientific and to practical men, that the presence 



* Wohler has already directed his attention to the fact that every dimorphus 

 substance has two different degrees of fusibility. 



