412 



Prof. D. E. Hughes. 



[Mar. 6, 



on the exterior by polishing with emery paper, or dissolve this first 

 in acidulated bichromate of potass. 



A perfect curve of these opposing polarities can be obtained by 

 placing a glass vessel containing the steel and solvent in the balance 

 itself, taking continual observations during its solution, and we may 

 thus observe the gradual rise ill force to a maximum, then its fall to 

 zero, to an opposing polarity, completely verifying all previous obser- 

 vations. 



Supposing the magnetised steel previous to heating gave 200° we 

 should reduce it to 50° if heated to dull red, a bright red heat would 

 probably reduce it to 20° ; we should then start from an almost 

 perfect neutrality to find, on dissolving its exterior (and allowing 

 for the reversed polarity of the reversed portion), all its previous 

 polarity. 



Faraday remarked that the magnetic qualities of iron disappeared 

 at yellow-red heat (1050° 0.), reappearing gradually when cooled to 

 red heat (700° C). I have found that if we heat the steel to yellow- 

 red heat the whole previous structure disappears, and does not re- 

 appear on cooling. No satisfactory explanation, as far as I am aware, 

 has been offered relative to the disappearance of the magnetic qualities 

 of iron and steel at certain temperatures, but noticing that its internal 

 structure is also changed, the following hypothesis may explain the 

 phenomenon. 



Assuming that increased heat increases molecular vibration, and 

 that molecules would oscillate to a degree dangerous for the stability 

 of any previous structure, a moment would arrive when the oscilla- 

 tions were so great that all structural formations disappear ; and 

 precisely at this instant there would be no external evidence of 

 polarity, or magnetic quality, as the molecules would be oscillating 

 through a range on both sides of external neutrality. On cooling (the 

 previous structure having disappeared) they would satisfy their 

 mutual attractions by the shortest path, forming probably, if perfectly 

 free, a closed circuit of two, grouping themselves as a double mole- 

 cule ; but if a directing influence, such as a continuous current of 

 electricity, was passed through the bar, then they would obey this 

 influence, and in the latter case the closed magnetic circuit would be 

 in concentric circles, as I have demonstrated in previous papers. 



A similar effect is caused by mechanical vibrations. I have already 

 shown that we increase the internal curves by gentle blows of a 

 mallet, thus allowing the molecules sufficient freedom to follow their 

 path, as in the case of red heat ; but if we strike violently upon the 

 end of the rod, the whole structure is broken down by the violent 

 oscillations of its molecules, and the neutrality now resembles exactly 

 that produced at yellow-red heat. 



The theory of symmetrical neutrality which I have demonstrated, 



