44 LETTEES OF BEEZELIUS 



Faraday and de la Eive ; but I hope that this will 

 not prevent my work from contributing something 

 towards the agreement of physicists on a question 

 which has so long been the subject of controversy. 

 In the second part of the book I have given some 

 conjectures as to the chemical constitution of the so- 

 called hydrated acids and bases, as well as of many 

 double salts. I am really very curious to hear what 

 you think of the hypotheses which I have pro- 

 pounded, and you would be doing me the greatest 

 kindness if you would take an opportunity of letting 

 me know in a letter what is your frank opinion of 

 them, and also of the contents of the first section, 

 dealing with contact action. I have been much 

 interested to learn, from a communication l of yours 

 to the Stockholm Academy, that you are inclined to 

 ascribe the passivity of iron to an allotropic condi- 

 tion of the metal. The only remarkable thing about 

 it is that the allotropy should be confined to the 

 surface, and not extend in any degree to the interior 

 of the iron; for the current which determines the 

 passivity of the surface goes through every part of 

 the iron, which serves as positive electrode. The 

 statements which Martens of Brussels has quite 

 recently made to the Academy of that town, 2 accord- 

 ing to which a red heat, irrespective of any oxidation, 

 is sufficient to secure the passivity of iron, are quite 



1 Stockholm Acad. Handl. (1843) p. 1 ; and Poggend. Annal., 

 vol. Ixi. (1844) p. 14. 



2 Bruxelles Acad. Sci. Bui (1843) [Pt. 2] p. 406 ; [Supple- 

 ment in Poggend. AnnaL, vol. Ixi. (1844) p. 121]. 



