AVy JURE 



2>:-.7 



THURSDAY, FEBRUARY 8, 1900. 



FARADA Y AND SCHONBE/jV. 

 T/ic Letters of Faraday and Schonbein, 1836-1862 ; 

 -uith Notes, Comments and References to Contem- 

 porary Litters. Edited by Georg W. A. Kahlbaum 

 and Francis V. Darbishire. Pp. xvi + 376. With 

 two frontispiece portraits. (Bale : Benno Schwabe. 

 London : Williams and Norgate, 1899.) 

 ""T^HE correspondence which has passed between the 

 J- great pioneers of modern science must always be 

 of interest to the present generation of workers. The 

 interest is enhanced for us in the present case through 

 the circumstance that one of the correspondents was our 

 eminent countryman, Michael Faraday. The custom 

 which has grown up of late years of allowing our 

 illustrious dead to speak for themselves through their 

 own letters is in every way a good one — particularly 

 when the correspondence enables us to trace the history 

 and follow the development of discoveries which have 

 now become incorporated in the general stock of 

 scientific knowledge. There is a living reality about a 

 man's description of his own work, which inspires the 

 reader to a degree quite incapable of being produced by 

 any bald text-book statement or formal lecture-room 

 utterance. Such correspondence is even as valuable in 

 ^lome cases as the original memoirs in which the final 

 results are set forth, because we are enabled to follow 

 the actual working out of the various lines of thought, 

 and to stand at the elbow of the investigator as he gropes 

 iiis way towards the truths which he finally gives to the 

 world. 



The present volume contains 155 letters, of which 

 eighty one are by Schonbein ; the whole correspondence 

 rovers a period of over a quarter of a century. Some of 

 1 araday's letters have been published in Bence Jones's 

 life of that philosopher, but the majority have never been 

 made public before. Much of Schonbein's correspond- 

 ence also has been published, because Faraday was 

 in the habit of communicating to the Philosophical 

 Magazine results of scientific importance announced by 

 Schonbein in his letters. But the value of the present 

 work is in no way impaired by this circumstance, because 

 we have now the whole correspondence brought together 

 chronologically, the letters being left intact as originally 

 written, and made more valuable by a most complete 

 series of explanatory notes giving references to the 

 papers alluded to, as well as short biographical notices 

 of people mentioned in the correspondence. The care 

 and trouble which has been bestowed upon this most 

 essential adjunct to a set of letters containing references 

 to memoirs which for us represent the scientific litera- 

 ture of a former generation, has thus resulted in a dis- 

 tinct contribution to the history of science, and the 

 editors have laid all workers in the domains of physics 

 and chemistry under a debt of obligation. 



The human side of Faraday's nature has been so 

 thoroughly dealt with by his biographers, Bence Jones, 

 Tyndall and Gladstone, and, more recently, by S. P. 

 Thompson, that very little new light is thrown upon his 

 character by these letters. It is painful to be reminded 

 NO. 1580. VOL. 61] 



so frequently of his failure of memory, and of his bad 

 health leading to periodical remc^vals from London and 

 temporary cessation from all work. As in the case of 

 another of our illustrious countrymen, Charles Darwin, 

 one can only marvel at the magnitude of the labours 

 achieved under such disadvantageous conditions. 



On comparing the letters of the two correspondents, 

 it will be found that from the social point of view both 

 Faraday and Schonbein are equally communicative ; but 

 while the Swabian chemist gives his scientific thoughts 

 and results in such fulness that they are in many cases 

 capable of being published as written, Faraday, on the 

 other hand, does not give much detailed information 

 about his work, but only alludes incidentally to his dis- 

 coveries when these appear to him to be of sufficient 

 interest to mention to his correspondent. 



We are thus enabled to follow Schonbein's work in a 

 very systematic manner, and the development of the 

 leading discoveries with which his name will always be 

 associated can be traced from year to year as he unfolds 

 them to the English philosopher. Speaking generally, 

 it may be said that the three main lines of work which 

 engaged his attention were the " passive " state of iron, 

 ozone and hydrogen peroxide, and gun-cotton. Inci- 

 dentally, many interesting side issues are raised, and 

 passages can be gleaned here and there from his letters 

 which show the wide grasp of, and philosophical insight 

 into, the principles raised by his experimental skill. The 

 first communication refers to "passive" iron (1836), and 

 this subject is brought forward again and again for over 

 six years. The explanation of the phenomenon was 

 obscure to its discoverer, and led to his bringing the 

 subject under the notice of Faraday and other contem- 

 porary men of science. Even if Schonbein did not find 

 the true explanation, there can be no doubt that his work 

 in this field had a great influence in directing his thoughts 

 towards the action of the voltaic current and electrolysis 

 in general, as he frequently refers to his speculations on 

 these subjects. With regard to the explanation it may 

 be said, as Kahlbaum points out in the introduction :— 



" Even at the present day we have not succeeded in 

 gaining clear insight into the cause from which this 

 phenomenon proceeds." 



The first reference to ozone is contained in a long 

 letter dated April 4, 1840, in which Schonbein tells 

 Faraday : — 



"The phosphorus smell which is developed when elec- 

 tricity (to speak the profane language) is passing from 

 the points of a conductor into air, or when lightning 

 happens to fall upon some terrestrial object, or when 

 water is electrolysed, has been engaging my attention 

 the last couple of years, and induced me to make many 

 attempts at clearing up that mysterious phenomenon. 

 Though baffled for a long time, at last, I think, I have 

 succeeded so far as to have got .the clue which will lead 

 to the discovery of the true cause of the smell in 

 question." 



This letter was communicated to the Royal Society on 

 May 7, and an abstract published in the Philosophical 

 Mas^azine. From that time ozone is frequently referred 

 to, and the vicissitudes through which the new "odor- 

 iferous principle " passed can be followed with interest 

 throughout the correspondence. At one period Schon- 



Q 



