22 



NA TURE 



[May$, 1883 





cumstances, very brilliant, while the spark in the broad ends is 

 wider and les bright, but does not fill the tube. On viewing 

 such a tube end on, and projecting the image of the narrow part 

 of the tube on to the slit of the spectroscope, a continuous spec- 

 trum of the width of the image of the narrow part of the tube 

 is seen, besides the lines of hydrogen given by the discharge in 

 the wide part of the tube. These lines extend above and below 

 the narrow continuous spectrum if the electrode is well placed 

 so that half an inch or so of the spark in the wide part of the 

 tube may intervene between the narrow part of the tube and the 

 spectroscope. The continuous spectrum of the narrow part of 

 the tube seems due chiefly to the ex .ansion of the hydrogen lines 

 when the discharge occurs in so confined a space, and it is much 

 brighter than the lines given by the spark in the wide part of 

 the tube. Where the latter cross the continuous spectrum a very 

 evident ahsorption occurs. The authors observed it with a dif- 

 fraction grating. The C line in the third order falls so near the 

 F line in the f.iurth that both may be observed together. F is 

 much more expanded than C, and the reversal consequently le-s 

 marked though quite plain. The other lines being still more 

 diffuse, their absorption could not be traced. 



The authors have before observed (Proc. Roy. Soc. vol. xxx. 

 p. 157) that the C and F lines of hydrogen are visible in the arc 

 of a De Meritens' magneto-electric machine taken in hydrogen-; 

 though in the arc of a Siemens' machine the C line can only be 

 detected at the in-tant of breaking the arc, the F line hardly at 

 all. When, instead of taking the arc in hydrogen, small drops 

 of water are allowed to fall from a fine pipette into the arc 

 taken in air in a lime crucible, each drop as it falls into the arc 

 produces an explosive outburst of the hydrogen lines. Generally 

 the outburst is only momentary, but occasionally a sort of flicker- 

 ing arc is maintained for a second or two and the hydrogen line 

 C is visible all the time. The lines (C and F) are usually much 

 expanded, but are frequently very unequally wide in different 

 parts of the line. F is weaker, more diffuse, and more difficult 

 to see than C, and is visible for a shorter time. There is no sign 

 of reversal. In the explosive character of the outburst and the 

 irregularity in the width of the lines the effect resembles that of 

 an outburst of hydrogen in the solar atmosphere. The elements 

 of the water are, it must be supposed, separated, but from the 

 explosive character of the effect they are not uniformly dis- 

 tributed in the arc. The arc being horizontal, and the image of 

 it projected on to the slit of the spectroscope, it was really a 

 very small section of the arc which was under observation, 

 and this renders the variation in the width of the lines the more 

 remarkable. 



April 5. — "On a hitherto unobserved Resemblance between 

 Carbonic Acid and Bisulphide of Carbon." By John Tyndall, 

 F.R.S. 



Chemists are ever on the alert to notice analogies and 

 resemblances in the atomic structure of different bodies. They 

 long ago indicated points of resemblance between bisulphide of 

 carbon and carbonic acid. In the case of the latter we have 

 one atom of carbon united to two of oxygen, in the case of the 

 former one atom of carbon united to two of sulphur. Attempts 

 have been made to push the analogy still further by the discoveiy 

 of a compound of carbon and sulphur analogous to carbonic oxide, 

 but hitherto, I believe, w ithout success. I have now to note a 

 resemblance of some interest to the physicist, and of a more 

 subtle character than any hitherto observed. 



When, by means of an electric current, a metal is volatilised 

 and subjected to spectrum analysis, the "reversal " of the bright 

 band of the incandescent vapour is commonly ob-erved. This 

 is known to be due to the absorption of the rays emitted by the 

 hot vapour in the partially cooled envelope of its own substance 

 which surrounds it. The effect is the same in kind as the absorp- 

 tion by cold carbonic acid of the heat emitted by a carbonic 

 oxide flame. For most sources of radiation carbonic acid is one 

 of the most transparent of gases ; for the radiation from the hot 

 carbonic acid produced in the carbonic oxide flame, it is the 

 most opaque of all. 



Again, for all ordinary sources of radiant heat, bisulphide of 

 carbon, both in the liquid and vapourous form, is one of the 

 most diathermanous bodies known. I thought it worth while to 

 try whether a body reputed to be analagous to carbonic acid, 

 and, like it, so pervious to most kinds of heat, would show any 

 change of depoitment when presented to the radiation from hot 

 carbonic acid. Does the analogy between the two substances 

 extend to the vibrating periods of their atoms ? If it does, then 

 the bisulphide, like the carbonic acid, will abandon its usually 



transparent character, and play the part of an opaque hody, 

 when presented to the radiation from the carbonic oxide flame. 

 This proves to be the case. Of the radiation from hydrogen, 

 a thin layer of bisulphide transmits 90 per cent., absorbing only 

 10. For the radiation from carbonic acid, the same layer of 

 bisulphide transmits only 25 per cent., 75 per cent, being ab- 

 sorbed. For this source of rays, indeed, the bisulphide 

 transcends, as an absorbent, many substances which, for all 

 other sources, far transcend it. 1 



Chemical Society, April 19. — Dr. W. H. Perkin, president, 

 in the chair. — The following gentlemen were elected Fellows : 

 T. L. Briggs. J. A. Basker, J. B. Coleman, W. H. Cannon, 

 E. C. Coniad, C. Gillett, E. C. Henning, N. K. Humphreys, 

 L. Levy, A. Ness, V. I. Schopoff, A. E.Wilson. — The follow- 

 ing papers were read :— On the gases evolved during the conver- 

 sion of grass into hay, by P. F. Frankland and F. Jordan. The 

 authors find that comparatively dry grass soon evolves consider- 

 able quantities of carbonic anhydride with mere traces of 

 hydrogen and hydrocarbons ; this evolution of gas occurs in air 

 and in an atmosphere of carbonic anhydride or hydrogen • in 

 oxygen a notable proportion of nitrogen accompanies the car- 

 bonic anhydride. Under water, grass also evolves carbonic 

 anhydride with some hydrogen, due probably to lactic fermenta- 

 tion, acetic, lactic, and propionic acids being simultaneously 

 formed. — Note on an apparatus for fractional distillation under 

 reduced pressures, by L. T. Thome. The object of this appa- 

 ratus is to facilitate the removal of the various fractions of the 

 di-tillation without breaking the continuity of the distillation. — 

 Notes on the condition in which carbon exists in steel, by Sir F. 

 A. Abel, C.B., and W. H. Deering. Two series of experiments 

 are given by the authors ; in the first the differences between cold 

 rolled, annealed, and hardened samples of the same steel are 

 investigated. The steel disks were subjected to the action of a 

 saturated solution of potassium bichromate containing 5 per cent, 

 by volume of sulphuric acid. In each case a blackish residue 

 consisting of a carbide of iron was left ; in the case of the cold 

 rolled and annealed disks, the carbon in this residue corresponded 

 pretty closely with the total carbon pre-ent ; hut in the hardened 

 disk only one-sixth of the total carbon was found in this residue. 

 In the second series of experiments, the action of various 

 strengths of bichromate solution on cold rolled steel is studied, 

 and it is proved that, if the oxidising solution be not too strong, 

 a residue consisting of a definite carbide Fe 3 C is left, and that 

 the carbon is therefore not simply diffused through the mass, but 

 exists as a definite compound capable of resisting the action of a 

 solvent which rapidly dissolves metallic iron. — On the spectrum 

 of beryllium with observations relative to the position of that 

 metal among the elements, by W. N. Hartley. From a photo- 

 graphic study of the spectrum, the author concludes that 

 beryllium is the fir-t member of a dyad series of elements of 

 which in all probability calcium, strontium, and barium are 

 homologues. 



Linnean Society, April 19. — Sir John Lubbock, Bart,, 

 president, in the chair. — Messrs. T. W. Coffin, F. H. Collins, 

 C. D. F. De Laune, D. Morris, J. Jardine Murray, and Hon. 

 J. B. Thurston were elected Fellows of the Society. — Mr. J. 

 Britten exhibi'ed and made remarks on specimens of Arum 

 italicum from Torquay, South Devon. — Mr. G. F. Angas showed 

 several vegetable products from the Island of Dominica, among 

 others an unusually large seed-pod of Cassia fistula, and other 

 examples of Leguminosae, also Polyporus fungi from the Roseau 

 Falls. — Mr. F. V. Dickins called attention to a Japanese work 

 issued by the University of Tokio, giving descriptions and illus- 

 trations of plants grown in the Botanic Gardens of Koiskikawa. 

 — A paper was read by Sir John Lubbock on the sense of 

 colour amongst some of the lower animals (vol. xxvii. p. 619). — 

 There followed a communication by Prof. P. T. Cleve of Upsala, 

 on the diatoms collected during the Arctic expedition of Sir 

 George Nares. — The Rev. A. E. Eaton gave a digest of an ex- 

 tensive monograph of the Ephemerida; or Mayflies, part i. In 

 this the subject is prefaced by an historical account and 

 general view of the group ; the genera are defined, and a 



1 Nearly twenty years ago I observed, among other changes of diathermic 

 position, the reversal of bisulphide of carbon and chloroform, when the pale 

 blue flame of a Bunsen burner was the source of heat. When, for example, 

 the rays issued from a luminous jet of gas, the absorptions of the bisulphide 

 and of chlorofotm were found to be o"8 and 12 per cent, respectively; 

 whereas when the Bunsen flame was employed, the absorptions of the same 

 two substances were in and 6'2 per cent. The cause of this reversal 

 doubtless is that in the Bunsen flame hot carbonic acid is the principal 

 radiant (Phil. Tram., 1864, p. 352).— April 6. 



