8 



Mr. T. C. Porter. 



[Nov. 9, 



and sulphur in the proportions necessary to the sulphides FeS, Fe9S 3 , 

 and FeS 2 . In each experiment two tubes of the mixture were made, 

 one for the magnet, and one to be fired at a distance from the magnet ; 

 this was done to find out whether there were any persistent differences, 

 other than magnetic, between the two. The mixture for FeS2 refused 

 to burn in both the tubes, as indeed might have been expected. The 

 polarity of the Fe 2 S 3 bar was decided, that of the FeS distinct, though 

 very weak. In every case the magnetised bars have remained unmis- 

 takable magnets, but this may be due to part of the soft iron remaining 

 uncombined, or possibly to the formation of small quantities of 

 magnetite from the air between the particles of the powder at starting. 

 The bars were powdered very finely, and their specific gravity taken, 

 with the results shown in the table given in the addenda. 



It is scarcely necessary to point out that though there is no doubt 

 that one or more of the compounds FeS, Fe 3 Si, and Fe 2 S 3 was really 

 formed, we do not know the proportion of each present in each case. 

 Probably the products were purer in the first and last cases. The 

 specific "gravities were taken with all care, and the first two places of 

 decimals are reliable ; the powders were thoroughly well mixed, and 

 the experiments were made from the same samples of mixture, in 

 similar tubes. The writer hopes to repeat them, and will not comment 

 at present on the differences of density in the magnetised and 

 unmagnetised products. 



Similar experiments were next tried with the magnetic oxide of 

 iron Fe 3 4 . 



(a) By allowing a considerable quantity of the levigated iron to 

 form a thick chain between the solid conical poles of the electro- 

 magnet, and pressing them together until they formed a dense mass 

 between the poles, and then burning them in situ, in one experiment 

 with the flame of an ordinary Bunsen burner, and in another by that 

 of an oxy-coal gas flame, blowing on the still very hot mass with pure 

 oxygen to complete the oxidation as far as possible; in both cases 

 the resulting mass of magnetic oxide was of very marked polarity. 



(b) By placing between the poles of the electro-magnet, so that its 

 upper surface was in the strongest part of the field, a charcoal block, 

 having cut in it, parallel to the lines of magnetic force, a shallow 

 groove, which was filled with previously prepared magnetic oxide, and 

 whilst the current traversed the magnet coils, fusing these fragments 

 into one bar, by means of the oxy-gas blow-pipe, afterwards blowing 

 on the still white hot mass with pure oxygen. On cooling the mass 

 and testing it, it proved distinctly polar, but far less so than in the 

 experiments (a). In this experiment the oxide had been heated to a 

 brilliant whiteness, and cooled somewhat quickly by being wetted 

 with water. 



These experiments seem to prove that it is possible to prepare in 



