446 Sir Henry Roscoe [June 1, 



give you an idea of the value attached by chemists to the results of 

 this investigation by quoting the opinion of one eminently qualified 

 to judge, namely, Professor Ostwald of Leipzig: — 



" In no other research in this domain of science," says Ostwald, 

 " do we find exhibited such an amount of chemical, physical and mathe- 

 matical dexterity, of ability in devising experiments, of patience and 

 perseverance in carrying them out, of attention given to the minutest 

 detail, or of breadth of view as applied to the grander meteorological 

 and cosmical phenomena of nature." 



In this connection I think that the following letter from Bunsen 

 to myself, now published for the first time, may interest my audience. 

 It requires only a word or two of explanation. On my return to 

 England from Heidelberg for the Christmas holidays, 1855-6, I 

 heard for the first time of Draper's previous work on a chlorine and 

 hydrogen " tithonometer," and, somewhat downcast by this discovery, 

 I wrote to Bunsen on the subject. His wise and encouraging words 

 put new heart into me, and I returned to work at Heidelberg deter- 

 mined to do my best to prove equal to the task that lay before me. 



" Heidelberg, Idth January, 1856. 

 "My deae Feiend, 



" I think that Draper's experiments will not require to be 

 repeated by us any more than Witwer's. Independently of much 

 that appears to me to be inexplicable in them, the pressure to which 

 the luting liquid saturated with H and CI is subjected constantly 

 changes. I therefore conclude that Draper's instrument will not 

 indicate proportionality, etc., especially as tbe volume of the insolated 

 gas is so small compared with that of the luting liquid. At any 

 rate I see no grounds for interrupting our experiments, still less do 

 I consider that it is a misfortune that the results which we have 

 obtained should have been to some extent previously described by 

 him. It appears to me that the value of au investigation is not to 

 be measured by whether something is described in it for the first 

 time, but rather by what means and methods a fact is proved beyond 

 doubt or cavil, and in this respect I think that Draper has left plenty 

 for us to do. Do not, therefore, let your discovery of Draper's work 

 disconcert you. I am now busy getting my Eudiometry ready for 

 press, and I hope by Easter to have made an end of it. My best 

 greetings to Williamson, in hearty friendship, 



Yours, 



R. W. Bunsen." 



In 1889 Bunsen retired from active University life, resigning his 

 professorship, and therefore his official residence, and retiring to a 

 pretty little villa in "Bunsen Strasse," which he had purchased, 

 where he spent the remainder of his days in quiet repose. His chief 

 relaxation and enjoyment throughout his life in Heidelberg was to 



