52 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



At a November meeting of the Royal Astro- 

 nomical Society, the Royal Astronomer Airy 

 showed a sketch of the comet made by Mr. 

 Carpenter, of Greenwich, giving the impres- 

 sion of a somewhat shuttlecock-shaped nebu- 

 lous haze, extending on either side, and im- 

 parting a flattened appearance to the head of 

 the comet. Dr, Huggins had made a drawing 

 which coincided in all essential particulars 

 with that of Mr. Carpenter. He thought that 

 he had detected a very minute but distinctly- 

 marked nucleus in the paraboidal-shaped head 

 of the shuttlecock. The whole light of the 

 comet was very faint, but he had succeeded 

 in obtaining its spectrum, which, as in the 

 case of that of Comet II., 1868, consisted of 

 three bands, apparently identical with the 

 bands in the spectrum of the vapor of carbon. 

 The middle band situated near "little b" was 

 much brighter than the other two, and he 

 was quite satisfied of its identity with the 

 middle bands of carbon-vapor: the two out- 

 lying bands were much too faint for him 

 to speak with confidence of their identity, but 

 they appeared to correspond. The Astron- 

 omer Royal showed a celestial globe, on which 

 he had fixed a small white wafer in the place 

 occupied by the sun, and a piece of white pa- 

 per cut out to represent the comet. He point- 

 ed out that its longer axis was directed almost 

 exactly to the sun, and that its head and nu- 

 cleus were turned away from the sun. This 

 appears to be the almost universal rule with 

 the smaller class of comets. 



Comets' Tails, etc., as Electrical Phenomena. 

 Prof. Osborne Reynolds, of England, ad- 

 vances the theory that the tails of comets are 

 merely examples on a large scale of the famil- 

 iar action known as the " electric brush," which, 

 as seen in the Geissler tubes, exhibits appear- 

 ances remarkably like the former. But it is 

 quite clear that the tail of a comet cannot be 

 due to a discharge between two electrodes 

 situated in the comet itself. If the tail is elec- 

 trical, that fact is attributable to a discharge 

 of electricity of one kind or another from the 

 comet, which for the time answers to one of 

 the electrodes only. This electricity the au- 

 thor supposes to be more and more set free 

 by the inductive action of the sun as the comet 

 approaches, and it would also be driven off 

 by induction in a direction opposite to that of 

 the sun, and combining with the positive elec- 

 tricity in the ether would form the comet's 

 tail in a manner analogous to that in which 

 a negative spark is given off by the lid of 

 the electrophorus. Upon the same general 

 hypothesis as serving to explain all the phe- 

 nomena he accounts for the exhibition of the 

 eolar corona, and also of the auroral light. 

 Upon the last-named point he says : 



If we could observe the aurora from a point dis- 

 .antfrom the earth, it is very probable that we should 

 find the same to be the case ; but whether this would 

 be so or not, an assumption has been made as to the 

 cause and nature of the aurora, which will answer 



just as well for the corona and comets' tails : it is, 

 that the sun, acting by evaporation or otherwise, 

 causes continual electnc disturbance between the 

 earth and its atmosphere, the solid earth _being nega- 

 tively charged and the atmosphere positively, and 

 that the aurora is the reunion of these electricities 

 taking place in the atmosphere. 



Now, as has been already said, this 'assumption 

 will serve for the comets and the sun as well as for 

 the aurora. If there is a continual electric disturb- 

 ance between the sun and the medium in which it is 

 placed, so that the sun becomes negatively and the 

 medium positively charged, the reunion of these elec- 

 tricities would form the corona. It must not be sup- 

 posed that I assume the sun to be a reservoir of elec- 

 tricity which it is continually pouring into space. I 

 consider that the supply of electricity in the sun is 

 kept up by some physical action going on between 

 the sun and the medium of space, whereby the sun 

 becomes negatively charged, and the medium posi- 

 tively. 



This may be well illustrated Ly reference to the 

 common electrical machine ; here the motion of the 

 glass against the rubber causes the glass to become 

 positively and the rubber negatively charged ; and 

 these electricities do not unite instantly there and 

 then, but remain and accumulate in the respective 

 bodies, until collected and brought together again by 

 the conductor. 



Assume, then, that the sun is in the position of the 

 rubber, while the ether is in that of the glass : then 

 the corona corresponds to the spark or brush which 

 leaves the conductor. 



If the corona be an electric discharge, the elec- 

 tricity will be continually carrying off some of the 

 elements of the sun into space, where they will be 

 deposited and condensed. May not this stream of 

 matter be the cause of the existence of small meteors, 

 and supply the place of those which, continually fall 

 into the larger bodies ? 



The Spectrum of Uranus. Dr. Huggins has 

 read before the Royal Society a paper on the 

 spectrum of Uranus. The light from the plan- 

 et is too faint to be satisfactorily examined 

 through most telescopes, but with an equa- 

 torial refractor of 15 inches he had obtained 

 good results. The most refrangible band in 

 the spectrum appeared to coincide with the 

 bright line of hydrogen, a comparison being 

 made with the light from a tube containing 

 rarefied hydrogen rendered luminous by an 

 induction-spark. Dr. Huggins says that there 

 is no strong line in the spectrum of Urnnns 

 in the position of the strongest of the lines 

 of air. namely, the double line of nitrogen. 

 As carbonic-acid gas might be considered, 

 without much improbability, to be a con- 

 stituent of the atmosphere of Uranus, he took 

 measures with the same spectroscope of the 

 principal group of bright lines which pre- 

 sent themselves when the induction-spark is 

 passed through this gas. The result was to 

 show that the bands of Uranus cannot be 

 ascribed to the absorption of carbonic-acid gas. 



The Spectroscope and, the Nebular Hypothe- 

 S 2*g. In the American Journal of Science, for 

 September, appears a paper from Prof. Kirk- 

 wood, arguing that the nebular hypothesis has 

 been greatly strengthened by the researches 

 and discoveries of the last twenty years 

 (or since Lord Rosse partially resolved the 

 great nebula in Orion and thereby, as some 

 have claimed, injured the standing of the 



