Oct. 20, 1887] 



NATURE 



585 



Iang together by reason of the attraction between their 

 pposite charges. It is also certain that when an electro- 

 lotive force— /.^. any force capable of propelling electri- 

 ity — is brought to bear on the liquid, the hydrogen 

 toms travel on the whole in one direction, viz. down hill, 

 nd the oxygen atoms travel in the other direction, viz. up 

 hill ; using the idea of level as our analogue for electric 

 potential in this case. The atoms may be said to be driven 

 along by their electric charges just as charged pith balls 

 would be driven along ; and they thus act as conveyers 

 of electricity, which otherwise would be unable to move 

 through the liquid. 



Each of this pair of opposite processions goes on until 

 it meets with some discontinuity — either some change of 

 liquid, or some solid conductor. At a change of liquid 

 another set of atoms continues the convection, and 

 nothing very particular need be noticed at the junction ; 

 but at a solid conductor the stream of atoms must stop : 

 you cannot have locomotion of the atoms of a solid. 

 The obstruction so produced may stop the procession, 

 I and therefore the current, altogether; or on the other 

 I hand the force driving the charges forward may be so 

 j great as to wrench them free, to give the charges up to 

 the electrode which conveys it away by common conduc- 

 y, tio n, and to crowd the atoms together in such a way that 

 ^■bey are glad to combine with each other and escape. 

 I^B Now notice the fact of the two opposite proces- 

 ^Bsions. One cannot have a procession of positive 

 atoms through a liquid without a corresponding proces- 

 sion of negative ones. In other words, an electric current 

 in a liquid necessarily consists of a flow of positive electri- 

 city in one direction, combined with a flow of negative 

 electricity in the opposite direction. And if this is thus 

 proved to occur in a liquid, why should it not occur 

 everywhere ? It is at least well to bear the possibility in 

 mind. 



Another case is known where an electric current cer- 

 tainly consists of two opposite streams of electricity, viz. 

 the case of the Holtz machine. While the machine is 

 being turned, with its terminals somehow connected, the 

 glass plate acts as a carrier conveying a charge from one 

 collecting comb to the other at every half revolution ; but, 

 whereas it carries positive electricity for one half a rota- 

 tion, it carries negative for the other half. The top of 

 the Holtz disk is always, say, positively charged, and is 

 travelling forward, while the bottom half, which is travel- 

 ling backward at an equal rate, is negatively charged. 



In the Holtz case the speeds are necessarily equal, but 

 the charges are not. In the electrolytic case the charges 

 are necessarily equal, but the speeds are not. Each atom 

 has its own rate of motion in a given liquid, independently 

 of what it may happen to have been combined with. This 

 is a lawdiscovered by Kohlrausch. Hydrogen travels faster 

 than any other kind of atom ; and on the sum of the 

 speeds of the two opposite atoms in a compound the 

 conductivity of the liquid depends. Acids therefore in 

 general conduct better than their salts. 



Oliver J. Lodge. 

 ( To be continued.^ 



JOSEPH BAXENDELL, F.R.S. 



"tlTE have already announced the death of Joseph 

 * ' Baxendell, an event which took place on Friday, 

 the 7th inst., at the Observatory, Southport. 



Born at Manchester in 181 5, he had not the advantage 

 of a thorough scientific training, such an education being 

 much less frequent at that early period than it is at the 

 present day. On the contrary, he had to make his way 

 in the world, and went to sea when quite a youth. We 

 are all of us moulded by circumstances, and while Baxen- 

 dell no doubt inherited an aptitude for science, yet the 

 particular bent which this took was unquestionably deter- 

 mined by the circumstances of his profession. An in- 



telligent seaman cannot fail to be impressed with the 

 importance of astronomy and meteorology, and it was 

 in these two sciences that Baxendell especially distin- 

 guished himself in after life. 



Meanvyhile, notwithstanding the engrossing duties of a 

 sailor, his energy and perseverance in the pursuit of 

 science were such that he was enabled to supplement the 

 deficiencies of his limited education, acquiring a know- 

 ledge of mathematics which was of great service to him 

 in his investigations. A training of this kind is well 

 qualified to produce a mature and thoughtful student of 

 Nature, and it had this effect upon Baxendell. Owing to 

 a retiring disposition, he was not much seen in general 

 scientific society, but was, on the other hand, very highly 

 esteemed by students like himself. A gathering of such 

 students usually takes place once a fortnight during the 

 winter months at the rooms of the Manchester Literary 

 and Philosophical Society. At these meetings Baxendell 

 was a most regular attendant, and he ultimately became 

 Secretary of the Society as well as editor of its publications. 

 It is in the Memoirs and Proceedings of this Society 

 that most of his scientific contributions will be found, and 

 in astronomy it is only necessary to notice his catalogue 

 of variable stars, which is very highly esteemed by all 

 observers. 



Baxendell's contributions to meteorology are very im- 

 portant, and in one branch of this science he may claim 

 to be the pioneer. In 1 871, from an analysis of eleven 

 years' observations of the Radclifte Observatory, Oxford, 

 he came to the conclusion that the forces which produce 

 the movements of the atmosphere are more energetic in 

 years of maximum than in years of minimum sun-spot 

 activity. This conclusion has now been confirmed in 

 various directions by other observers. We have heard it 

 objected that Baxendell generalized from a comparatively 

 small number of observations, but in a question like this 

 such a procedure is essential to the pioneer. His task is 

 to deduce with a mixture of boldness and prudence some- 

 thing of human interest out of the mass of observations 

 already accumulated, and thus to stimulate meteoro- 

 logists not only to go on with their labour, but to cover 

 more ground in the future than they have covered in 

 the past. Baxendell's procedure in this respect has been 

 abundantly justified by the fact that many other men of 

 science are now following in his footsteps. 



It is believed that he was the first to propose the use of 

 storm- signals which are now universally adopted by all 

 maritime nations. He likewise foretold the long drought 

 of 1868, and enabled Manchester to take precautionary 

 measures which had the effect of rendering the inconve- 

 nience less severe. As an astronomer and meteorologist 

 Baxendell was naturally interested in a study of the sun, 

 and was an independent discoverer of the fact that the 

 faculae which accompany sun-spots are for the most part 

 thrown behind them — the word behitid having reference 

 to the direction of rotation of our luminary. It was, we 

 believe, his opinion that the behaviour of sun-spots is 

 intimately connected with that of meteoric matter around 

 the sun. Without asserting the exact nature of the bond 

 between these two phenomena, we think that various 

 students of the sun's surface are now inclined to be of this 

 opinion. 



He was a Fellow of the Royal Society and of the Royal 

 Astronomical Society. He was likewise a corresponding 

 member of the Royal Society of Konigsberg, of the 

 Scientific and Literary Academy of Palermo, and of the 

 National Observatories of France, Germany, and Italy. 

 For some years he enjoyed the use of his friend Mr. 

 Robert Worthington's observatory at Crumpsall. On the 

 death of the Rev. H. H. Jones, in 1859, he was appointed 

 Astronomer to the Manchester Corporation. Latterly his 

 health forced him to reside at Southport, in the neigh- 

 bourhood of which he continued his observations until 

 his death. Balfour Stewart. 



