PROFESSOR IN BERLIN 309 



they have expressed, whether in their writings, or in verbal 

 commerce with their students, acquire a fuller content and more 

 consistent form as they are more thoroughly worked out, 

 bringing new instruction to themselves also. The entire 

 conceptual world of civilized humanity comes before them as 

 a living and growing whole, which in comparison with the brief 

 life of the individual appears to be eternal. Such a one regards 

 himself, in his own small efforts towards the building up of 

 science, as a minister in an eternally righteous cause, with 

 which he is linked by the closest bands of love. Thus, even to 

 himself, his work is consecrated.' 



This is the temper which Helmholtz describes to the young 

 students as fostered by the German Universities, and which he 

 holds to be unrealized in other nations, while he does not deny 

 that Germany might well imitate England in her encouragement 

 of a keen sense of the beauty and freshness of antiquity, the 

 refinement and precision of language, and the physical weal of 

 the students. But the untrammelled freedom of the German 

 student, which amazes all foreigners, is a treasure that has to be 

 guarded; it depends on the judgement and reasonableness ol 

 those to whom the freedom is granted. Then, and then only, 

 is liberty of scientific teaching necessary and free from danger. 



' In the German Empire of to-day, the most extreme conse- 

 quences of materialistic metaphysics, the boldest speculations 

 on the basis of Darwin's evolutionary theory, can be promul- 

 gated as freely as the extreme deification of Papal Infallibility.' 



At the close of the same year (November 26, 1877), Helmholtz 

 presented a paper to the Academy, 'On Galvanic Currents, 

 caused by Differences of Concentration ; Deductions from the 

 Mechanical Theory of Heat,' which inaugurated the series of 

 his important researches in electrochemistry. After convincing 

 himself by his electrical work that the Faraday- Maxwell hypo- 

 thesis for electrodynamics (to the confirmation of which he did 

 not return for two years) was the most probable, he now turned 

 to Faraday's electrochemical theories, of which, as also of their 

 development by Hittorf, Wiedemann, and F. Kohlrausch, he 

 gave a full discussion in the Faraday Lecture delivered some 

 time later in England. 



Faraday gave the name of ions to the atoms or groups of 

 atoms that are carried along with the current, calling those that 



