78 



'NA TURE 



[November 22, 1900 



notions, that " certain diseases might be due to ozone." 

 The reply from Berzelius is chiefly remarkable for the 

 cogency of the reasons which he urges against the view that 

 nitrogen is a constituent of ozone, and the friendly spirit 

 in which he urges Schonbein to follow up his investiga- 

 tion " with true Bunsen perseverance." 



The letter from Schonbein dated January 15, 1845, 

 contains an account of the production of an " electro- 

 negative oxidising substance '' by the slow combustion 

 of ether vapour and phosphorus, by a hydrogen flame 

 and by a candle flame. This was read to the Academy 

 at Stockholm, and Berzelius in his reply considers his 

 correspondent to have proved that ozone is always formed 

 during combustions in atmospheric air. He then goes 

 on to criticise most frankly some of Schonbein's conclu- 

 sions in a detailed paper published in 1844, he makes 

 excellent suggestions for testing certain points experi- 

 mentally, and winds up with the remark : — 



" It would, therefore, be better to put on one side all 

 theoretical conjectures as to the constitution of ozone and 

 nitrogen, and to study the properties of ozone itself. 

 When once you have caught it, it will be easier to theorise 

 about it." 



In his reply Schonbein explains that much of his 

 coi^espondent's criticism had arisen from the misrepre- 

 sentation of his views owing to the bad rendering of his 

 paper into French, but he candidly and gratefully accepts 

 the remainder. He still clings, however, to the possi- 

 bility of nitrogen being a compound, and adds a remark 

 to the effect that even if this hypothesis were baseless, 

 it had guided him in all his experiments and had led 

 him to many discoveries. 



A letter of Schonbein's dated March 22, 1845, is of 

 particular interest from several points of view. It was 

 communicated by Berzelius to the Stockholm Academy, 

 together with another letter from Plantamour, of Geneva, 

 which contained a description of Marignac's first experi- 

 ments and conclusions respecting ozone. Schonbein in 

 his letter refers also to the work of his friend Marignac, 

 and describes the results to Berzelius. He considered 

 that his and Marignac's experiments confirm one another, 

 and he adds : — 



" I think we may fairly conclude from them that oxygen 

 and hydrogen are the constituents of ozone." 



Thus he had by that time abandoned the view that 

 nitrogen had anything to do with ozone, and it is quite 

 exciting, even at the present time, to read in this letter 

 how near he was to the explanation of the true nature 

 of ozone, and yet how he missed the path. He gives 

 convincing reasons for believing that ozone and Thenard's 

 hydrogen peroxide were distinct, and he proves by ex- 

 periment that ozone is destroyed by passing through a 

 hot tube. Yet it seems to have been first suggested by 

 Plantamour, in a letter to Berzelius dated April 20, 1845, 

 that ozone was not a compound, but only a form of 

 oxygen, although in the paper printed as an appendix 

 to the present volume Schonbein speaks of this view as 

 having been originated by De la Rive. 



The subsequent letters teem with interest especially 

 when, as in that dated June 20, 1846, the practical 

 applications of gun-cotton begin to figure in the corre- 

 spondence. The King of Sweden, at the instigation of 

 Berzelius, sent Schonbein the Vasa Medal in February, 

 NO. I 62 I, VOL. 63I 



1847. On March 12 of that year Berzelius addressed a 

 long letter to Schonbein full of the most friendly and 

 candid criticism of his views on the chemical nature of 

 nitric acid and ozone. From this it appears that 

 Schonbein still believed that ozone contained hydrogen, 

 for his correspondent says : — 



" But does ozone really contain hydrogen ? This 

 question we can answer most emphatically in the 

 negative. If oxygen gas collected during the last third 

 of its evolution from potassium chlorate be exposed to a 

 series of short electric sparks, ozone is formed just as 

 readily and to precisely the same extent as during the 

 first third of the operation. In this case, however, it is 

 physically impossible for water to be present. This 

 constitutes the most indisputable proof that ozone does 

 not contain hydrogen. Hence it follows that ozone is an 

 allotropic modification of oxygen itself, &c." 



The criticisms in this letter are altogether very 

 vigorous, and Berzelius lays down a principle at the 

 outset of his attack which it would have been well to 

 have kept in view in many " modern instances " of 

 theorising : — 



"The test of the truth of a theory is that it should 

 harmonise the particular instance with the whole system 

 of science ; for the laws of nature are always consistent 

 v^ith one another. Now if you advance a principle which 

 makes an exception of what was before consistent with 

 scientific ideas, logic pronounces against you." 



He concludes by begging his correspondent to excuse 

 his preaching, and hopes he will not refuse to learn. It 

 is, no doubt, only a coincidence, but this, the last letter 

 from Berzelius, is the only one in which the Swedish 

 chemist winds up with the subscription, " Farewell, yours 

 sincerely." The reply by Schonbein, dated March 29, 

 1847, contains a further defence of his views concerning 

 the nature of ozone and nitric acid, and begs in con- 

 clusion for a letter from Berzelius stating that he 

 (Schonbein) was the first discoverer of gun-cotton. He 

 had patented this explosive in England, and says that 

 his patent " will undoubtedly be contested." 



Berzelius died August 7, 1848, and the editor has dis- 

 covered a short sketch of an obituary notice by Schonbein 

 which was apparently never published, but which had 

 been hastily written on a sheet of paper partly covered 

 by the draft of a letter to Faraday. The position 

 occupied in the world of science by the illustrious Swede 

 needs no further definition at the present day, but this 

 short estimate of his achievements by his contemporary 

 Schonbein will still be read with interest. 



We have once again to express our obligations to Dr. 

 Kahlbaum and his colleagues for a remarkably interest- 

 ing little contribution to the history of chemistry. 



R. Meldola. 



SOME OBSERVATIONS ON ANIMAL 

 HYPNOTISM. 



Beitrd^e zur Physiologic des Centralnervensysiems, 

 Von Max Verworn, a.o. Professor an der Universitat 

 Jena. Erster Theil. Die sogenannte Hypnose der 

 Thiere. Pp. iv -f 92 ; and 18 figures. (Jena : J. 

 Fischer, 1898.) 



THIS volume by Prof. Verworn, on the phenomenon 

 of so-called hypnotism in the lower animals, is a 

 clear and exhaustive account of the subject. Paucity 



