PROFESSOR AT BONN 163 



the King of Bavaria, and he was invited to draw up a brief 

 report on the result of his discoveries in the Theory of Tone 

 for the King's edification. On April 15, 1858, he writes to 

 du Bois-Reymond : 



' I have now put together a complicated apparatus at the 

 King of Bavaria's expense, by which one is able to control 

 the vibrations of a tuning-fork at will by an electro-magnet, with 

 complete command of intensity and difference of phase. This 

 is in order to regulate the production of timbre (Klangfarbe).'' 

 The cost of this apparatus was 400 gulden, paid by the King. 



After he had commenced his lectures and scientific work for the 

 winter session, Bunsen again approached him on December 15, 

 1857, stating that the Baden Ministry had not given up hopes 

 of persuading Helmholtz to come to Heidelberg, since the 

 postponement of the building of a new Institute at Bonn 

 seemed to cancel some of his reasons for refusing, and that 

 they had therefore taken no steps as yet in other directions. 



Helmholtz consulted his father, who urged him strongly to 

 go to Heidelberg: 'Your scientific life and satisfaction in your 

 official career will have widely different prospects in Heidel- 

 berg as compared with Bonn; the mere fact of your being 

 able to confine yourself to physiology will be valuable to your 

 own scientific projects. Your obligations to science are greater 

 than to the State.' 



Helmholtz finally accepted the invitation from Heidelberg; 

 and on February 27, 1858, Kirchhoff writes to him : ' All 

 Heidelberg is rejoicing at your decision, and I hope you will 

 find a congenial atmosphere here.' On March 5, Helmholtz 

 informs du Bois that he had forwarded his resignation to 

 v. Raumer, as the Senate and Ministry had taken no steps 

 since his first refusal of the call to Heidelberg to carry out their 

 promises. On the same day he writes to his father : 



'At last I have accepted the call to Heidelberg. I have 

 already sent in my resignation to the Minister, v. Raumer. 

 The correspondence over the rebuilding of the Anatomy Depart- 



ent was left four months before the Prussian Ministry 

 nded to it, at the end of which time an undecided, pro- 

 crastinating answer was sent, and the feeling of the Academic 

 Senate, who were to cover a portion of the cost by selling 

 some of the land belonging to the University, is quite uncertain, 



M 2 



