70 



NATURE 



[May i8, 1893 



SCIENTIFIC SERIALS. 



American jfournal of Science, May. — Deportment of char- 

 coal with the halogens, nitrogen, sulphur, and oxygen, by 

 W. G. Mixter. The tenacity with which charcoal retains 

 hydrogen even after ignition in chlorine makes it difficult to 

 decide whether certain gases absorbed by charcoal are occluded 

 or chemically combined with it. Experiments performed on 

 sugar-charcoal, gas carbon, and "Diamond Black," a variety 

 of lampblack derived from natural gas, indicate that chlorine 

 does combine with charcoal, but that the combination is 

 brought about by a replacement of the hydrogen. Pure native 

 diamond and graphite do not take up chlorine, while iodine 

 and bromine are not absorbed even by impure charcoal. 

 Nearly pure amorphous carbon takes up but little sulphur, 

 while a soft charcoal containing much hydrogen and oxygen 

 combines with a considerable amount, taking it up even from 

 carbon bisulphide. — Note on some volcanic rocks from Gough's 

 Island, South Atlantic, by L. V. Pirsson. An examination of 

 beach pebbles from the shores of this craggy island, 240 miles 

 S.E. of Tristan da Cunha, establishes its recent volcanic nature, 

 and thus adds one more to ihe line of mid-Atlantic volcanoes 

 which, sweeping southward through the Azores, Cape Verde 

 Islands, Ascension, St. Helena, and Gough's Island, terminates 

 on Bouvet Island on the confines of the Antarctic Ocean. — The 

 influence of free nitric acid and aqua regia on the precipitation 

 ofbarium as sulphate, by Philipp E. Browning. In the presence 

 of nitric acid to the extent of 5 per cent, very little solvent 

 action is shown, and the sulphate may be safely filtered after an 

 hour's time. Even with 20 to 25 per cent, the solubility does 

 not exceed 0001 grm. on the average. Aqua regia has even 

 less solvent effect, and the presence of ten per cent, of either is 

 a positive advantage since it gives the precipitated sulphate a 

 coarsely crystalline form. — On a rose-coloured lime-and-alumina 

 bearing variety of talc, by \Vm. H. Hobbs. A talcose mineral 

 was found developed in some specimens of white crystalline 

 dolomite from Canaan, Conn., on lines evidently corresponding 

 to fracture planes in the rock. One of the specimens had a 

 deep rose colour, the other was nearly white, having lost its 

 colour by exposure to light. The mineral was shown to belong 

 to the talc family by its chemical composition and its physical 

 properties, but it differed from known varieties by its colour, 

 its high percentages of lime and alumina, its low fusibility, and 

 by its being easily decomposed by acids. — Also papers by 

 Messrs. A. M. Edwards, A. W. Whitney, S. T. Moreland, 

 S. L. Penfield, N. H. Darton, and M. I. Pupiu. 



Bulletin of Ihe New York Mathematical Society, vol. ii. No. 7 

 (New York, April 1893).— The contents are a review, by J. 

 Harkness, of Prof. Greenhill's " The Applications of Elliptic 

 Functions" (pp. 151-57), in which, though there is much ap- 

 preciative commendation, there is also the amari aliquid to add 

 pungency to the criticism. — Next comes a further contribution, 

 the third, on the non-Euclidian Geometry (pp. 158-61), this 

 time by Prof. W. Woolsey Johnson. — The remaining articles 

 are a notice of the Lehrbuch der Ausgleichsrechnung nach der 

 Methode der Kleinsten Quadrate of Dr. Bobek, and the theory 

 of errors and method of least squares of W. Woolsey Johnson, 

 by Mansfield Merriman (pp. 162-63) ! *"d '*o notes (i) on the 

 definition of logarithms (i.e. the definition givt-n by Prof. 

 Stringham in the Amer. Joxrn. of Math., vol. xiv.), by Prof. 

 Haskell ; (2) a note on the preceding note, by Prof. Stringham 

 (pp. 164-70). — The number closes with general nutes and list of 

 new publications. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, March 9. — "The Electrolysis of Steam." 

 By J. J. Thomson, M.A., F.R.S., Cavendish Professor of 

 Experimental Physics in the University of Cambridge. 



The following explanation of the results of the experiments 

 seems to the author to be that which agrees best with preceding 

 investigations. 



When an electric discharge passes through a gas the proper- 

 ties of the gas in the neighbourhood of the line of discharge are 

 modified. Thus, as Hittorf and Schuster have shown, the gas 

 in the neighbourhood of the discharge is no longer an insulator, 

 but can transmit a current under a very small potential difference. 

 Faraday's remark, that when once a spark has passed through a 



NO. 1229, VOL. 48] 



of 



of j^B 



I 



gas the passage of another following it immediately afterwards 

 is very much facilitated, is another example of the same thing. 

 We have thus good reasons for believing that when a spark 

 passes through a gas it produces a supply of a modification of 

 the gas, whose conductivity is enormously greater than that of 

 the original gas. I have shown (' Phil. Mag.,' November 1891 

 that the conductivity of this modified gas is comparable will 

 that of strong solutions of electrolytes. When the discharge 

 stops, this modified gas goes back to its original condition. I 

 now the discharges through the gas follow each other so rapidl; 

 that the modified gas produced by one discharge has not time t( 

 turn to its original condition before the next discharge passeSi 

 the successive discharges will pass through this modified gas. If, 

 on the other hand, the gas has time to revert to its original con- 

 dition before the next discharge passes, then the discharges pass 

 through the unmodified gas ; we regard this as being accom- 

 plished by means of successive decompositions and recombina- 

 tions of its molecules, analogous to those which, on Grotthus' 

 theory of electrolysis, occur when a current passes through an^ 

 electrolyte. 



We regard the arc discharge as corresponding to the first 

 of the preceding cases where the discharge nasses through the 

 modified gas, the spark discharge corresponding to the second' 

 when the discharge goes through the gas in its unmodified con- 

 dition. 



From this point of view, the explanation of the results of the 

 experiments on the electrolysis of steam are very simple. The 

 modified gas produced by the passage of the discharge through 

 the steam consists of a mixture of hydrogen and oxygen, those 

 gases being in the same condition as when the arc discharge 

 passes through hydrogen and oxygen respectively, when, as we 

 have seen, the hydrogen behaves as if it had a negative charge, 

 the ovygen as if it had a positive one. Thus, in the case of 

 the arc in steam, the oxygen, since it behaves as if it had a 

 positive charge, will go to the negative, while the hydrogen, 

 behaving as if it had a negative charge, will go to the positive 

 electrode. We saw that this separation of the hydrogen and 

 oxygen took place. 



The correspondence between the quantities of hydrogen and 

 oxygen from the electrolysis of the steam and those liberated by 

 the electrolysis of water shows that the charges on the atoms 

 of the modified oxygen and hydrogen are the same in iamount, 

 but the opposite in sign to those we ascribe to them in ordinary 

 electrolytes. 



In the case of the long sparks where the discharge gees 

 through the steam, since the molecule of steam consists of two- 

 positively charged hydrogen atoms and one negatively charged 

 oxygen one, when the molecule splits up in the electric field' 

 the hydrogen will go towards the negative, the oxygen towards- 

 the positive, electrode, as in ordin.iry electrolysis. 



April 27. — "On the Coloration of the Skins of Fishes, 

 especially of Pleuronectidfe." By J. T. Cunningham, M.A. 

 Oxon., Naturalist on the Staff of the Marine Bioloi^ical -Associa- 

 tion, and Charles A. MacMunn, M. A., M. D. Communicated^ 

 by Prof. E. Ray Lankester, F. R.S. 



The anatomical analysis of the structural coloration elements- 

 having not previously been adequately carried out, we have de- 

 scribed these elements as they are found in the Pleuronectidaeand 

 various other fishes. In the former family there are two kinds of 

 chromatophores, the black and the coloured, the latter usually 

 of some shade of yellow or orange. The coloured elements in - 

 the skin on the upper side are chiefly developed in the more 

 superficial layer immediately beneath the epidermis and for the- 

 most part outside the scales, and on the inner side of the skin in- 

 the subcutaneous tissue, the rest of the skin being almost destitute 

 of these elements. In the superficial layer the iridocytes are 

 somewhat polygonal plates of irregular shape, distributed 

 uniformly, and separated by small interspaces. The chromato- 

 phores are much larger, and farther apart, and are superficial to 

 the iridocytes, although sections show that their processes often 

 pass down between adjacent iridocytes. The coloured chromato- 

 phores have less definite outlines than the black, and as a rule 

 radiating processes are but indistinctly indicated in them. The 

 external part of the coloured chromatophore consists of diffused 

 yellow pigment, while in the centre the concentration of the 

 pigment produces a deeper colour, varying from orange to red, 

 as in the plaice and flounder. On the upper side of the fish the 

 subcutaneous coloration elements are quite similar, but not so 

 uniformly distributed ; the iridocytes are larger, and the 

 chromatophores not so symmetrical in shape. 



