328 HERMANN VON HELMHOLTZ 



ear. The variety of costumes and of nakedness is indescribable. 

 The turbans, which are only worn by the Moslems, are kept 

 scrupulously clean, and make a good effect ... as also the white, 

 or black and white striped burnous, with the extraordinarily 

 characteristic eyes and sharp features of the older men beneath 

 them. The women, so far as they appear in the streets, are 

 veiled in not over clean and coarse rough sheets, which they 

 are not too particular in drawing over their faces/ 



Helmholtz then returned by Seville, Bordeaux, and Paris to 

 Berlin, where he immediately resumed his lectures. 



At this time he was already occupying himself with the 

 arduous work in thermodynamics which stood in the closest 

 relation with his later discoveries in the principles of mechanics, 

 but was not published for another two years. He was, however, 

 obliged seriously to consider his health a little more in his 

 enormous undertakings. Even in Seville a slight fainting fit 

 had alarmed his travelling companion, and again after the 

 fatigues of the summer session, a few days before the holidays, 

 he met with an accident by slipping, due probably to a sudden 

 swoon, which might have had the most serious consequences. 



By August 8, however, he was able to announce to Ludwig 

 that he was so far better that he should begin the journey to 

 Munich with his wife in a few days by easy stages, and would 

 come first to Leipzig, to rest there a little. The projected 

 journey was carried out, after which he went for a few weeks' 

 rest to Switzerland, returning then to Berlin to resume his 

 thermodynamic work. In the meantime Hertz had been ap- 

 pointed his Assistant in the Physical Institute, and remained 

 there till the year 1883. Helmholtz was also working out 

 certain points that were intimately connected with his earlier 

 researches in electrodynamics and electrochemistry. 



The fact that a certain distribution of magnetism occurs in 

 the molecules of soft iron in the vicinity of a magnet, so that the 

 soft iron itself attracts and repels small magnetic bodies, was 

 known not to be peculiar to iron. Faraday had shown that this 

 effect is visible in almost all bodies, and that similar phenomena, 

 indicating a distribution of the opposing kinds of electricities 

 in the molecules of electric insulators, are called out by electric 

 forces. The phenomena were treated mathematically for the 

 motions of rigid magnets and magnetizable iron by Poisson ; 



