157 



as a certain proportion of sulphur communicates the same quality to 

 iron, so are the effects of phosphorus found to be ; phosphoret of iron 

 being, in this respect, much the most powerful, at least when con- 

 sidered comparatively with sulphuret of iron. 



8 ; and lastly. That as carbon, sulphur, and phosphorus, produce, 

 by their union with iron, many chemical effects, of much similarity, 

 so do each of them, when combined with that metal in certain pro- 

 portions, not only permit it to receive, but also give it the peculiar 

 power of retaining the magnetical properties ; and thus henceforth, 

 in addition to that carburet of iron called steel, certain sulphurets 

 and phosphurets of iron may be regarded as bodies peculiarly suscep- 

 tible of strong magnetical impregnation. 



Among the observations which are subjoined to this paper, we find 

 some remarks on the vitriolization of pyrites ; from which we collect, 

 that, contrary to the opinion of Mr. Proust, who thought that only 

 those pyrites in which the proportion of sulphur is very small are 

 liable to this change, the vitriolization is not so much owing to the 

 proportion as to the state of the sulphur in the compound ; and that 

 this state is probably the effect of a small portion of oxygen, pre- 

 viously combined with a part or with the general mass of the sul- 

 phur at the time of the original formation of the substances ; so that 

 the state of this ingredient is tending to that of oxide. 



It is, no doubt, remarkable, that the magnetical properties of the 

 sulphuret of iron, which forms the principal subject of this paper, 

 should never have been adverted to by any of the writers on mag- 

 netism. The few who observed it in the natural magnetical pyrites 

 chose to ascribe it to particles of common magnetical iron interspersed 

 in the ore : but from what has been stated, it is evident that this 

 opinion must be relinquished ; since there are certain known propor- 

 tions of sulphur, as well as of carbon and phosphorus, beyond which 

 the magnetical property will not be obtained, though the proportions 

 beyond this maximum would by no means exclude the interposition 

 of particles of iron. How far the combinations of magnetical sul- 

 phurets, carburets, and phosphorets may contribute towards the 

 making artificial loadstones of greater strength than those hitherto 

 known, is a subject recommended to the attention of future ob- 

 servers. 



Remarks on the voluntary Expansion of the Skin of the Neck, in the 

 Cobra de Capello or hooded Snake of the East Indies. By Patrick 

 Russell, M.D. F.R.S. With a Description of the Structure of the 

 Parts which perform that Office. By Everard Home, Esq. F.R.S. 

 Read June 14, 1804. \Phil. Trans. 1804,^. 346.] 



The information we gather from this paper is, that the remarkable 

 expansion of the skin of the neck, which constitutes a principal cha- 

 racter in this species, is a voluntary action, distinct from that infla- 

 tion which all serpents, when irritated, are more or less capable of : 

 that it is owing to a particular set of ribs situated at the neck of the 



