400 



NATURE 



\Sept. 6, 1877 



the cells, and their being moistened with good conducting 

 liquids, insulation was destroyed, and no static effects at 

 the terminal, or very feeble ones, were perceptible. This 

 re'^ult, by far the most important of Mr. Ga-siot's labours, 

 was published in the Phil. Trans, of the Royal Society 

 for 1844, p. 39. It got rid of the strongest objection to 

 the chemical theory of the pile, and broujht into harmony 

 results which up to that time had appeared discordant. 



In 1852 Mr. Grove had published in the Phil. Trans. 

 of the Royal Society, in a paper " On the Electro-Chemical 

 Polarity of Gases," an account of transverse dark bands 

 or striae, which he was the first to observe in the electric 

 discharge. The discharges were obtained from a Ruhm- 

 korf cnil, and made to pa-s through attenuated gases, or 

 what were comm >nly called vacua. Mr. Gassiot made a 

 vast number of experiments on these strije, the most 

 important of which was that he obtained them in a 

 Torricellian vacuum with the voltaic arc, showing that 

 they did not depend on the intermittence of the discharge 

 (occasioned by the contact-breaker), but accompanied all 

 electric discharges in vacuo. There is, perhaps, some 

 doubt whether the voltaic arc is absolutely continuous, or 

 whether it does not produce, by its action on attenuated 

 gas, somelhintr like waves (a stone thrown into water may 

 be a lOugh simile), but at all events it is continuous in its 

 inception, and in that respect quite different from the 

 interrupted discharges of the contact-breaker apparatus, 

 or the common electrical machine. 



Mr. Gassiot devoted himself for a long time to procuring 

 vacua as perfect as they could be obtained, for the 

 examination of the electric or voltaic discharges, and 

 proved distinctly that when the attenuation was pushed 

 to a high degree of rarity, the electric discharge would 

 not pass at all, a result which had been observed by 

 Morgan {Phil. Trans., vol. Ixxv.), the accuracy of whose 

 experiments was impugned by Davy. 



Mr. Grove, as an answer to the contact theory of the 

 voltaic pile, had shown that if two polished plates, one of 

 zinc, the other of copper, were approximated, but kept 

 from contact by a thin film of paper or mica, and then 

 separated, the electric effects, alleged to be due to the 

 contact of dissimilar metals, were produced ; it was ob- 

 jected to this experiment, and not without reason, that 

 these effects might be produced by friction of the paper 

 or mica. Mr. Gassiot effectually got rid of this objection 

 by bringing the plates into close proximity by a delicate 

 micrometer apparatus and then quickly separating them ; 

 the same electrical results followed {Phil. A/aq., October, 

 1844). 



The above are the principal of many curious results 

 obtained by Mr. Gassiot. While thus giving up his 

 leisure time to science, he was a diligent and successful 

 man of business and a liberal promoter of, and contribu- 

 tor to, all useful scientific and benevolent objects, some of 

 which we mentioned in our previous notice. 



TNE SPECTRUM OF NOVA CYGNI 



IN the Monatsbericht of the Royal Academy of Sciences 

 of Berlin (May, 1877), Herr Vogel, the eminent 

 astronomer, publishes the details of his investigafons of 

 the spectrum of the new star in Cygnus, and whdst ex- 

 pressing his own views with regard to the physical con- 

 dition of the star, enters upon a criticism of those of 

 other observers. Herr Vogel observed the spectrum on 

 sixteen different nights ; the first observaton was made 

 on December 5, v. hen the star was of 4'5 magnitude; 

 the last on March 10, when the magnitude was only 



8'3- 



Herr Vogel's observations show that the spectrum of 

 the new star was a continuous one, showing numerous 

 dark lines and bands and several bright lines. The 

 intensit\ of this continuous spectrum, which at first was 

 very brilliant, decreased rapidly, so that three months 

 after the di-covery of the star it was only partly visible, 

 and even that part was very faint. The decrease of in- 

 tensit) did not spread evenly over the whole spectrum ; 

 the blue and violet rays grew fainter far more rapidly 

 than the green and yellow rays. The red part of the 

 spectrum, which already during the first observations was 

 very dim a' d crossed by broad absorption bands, soon dis- 

 appeared altogether, so th.'it a bright line in the red seemed 

 to reniain quite isolated. At first a dark band in the 

 green, and, later on, a very broad dark band in the blue, 

 were particularly conspicuous. With the exception of a 

 bright line in the red, the other bright lines at first sur- 

 passed the continuous spectrum but very little in brilliancy ; 

 they could therefore be seen only with difficulty. During 

 the rather rapid decrease of intensity of the continuous 



spectrum they, however, became more easily discernible, 

 and, as results from the measurements made, the hydro- 

 gen lines Ha and H/3 were particularly bright, and, later 

 on, a line of 499 mill. mm. wave-length. This latter line 

 remained longest when the spectrum faded away, and 

 finally surpassed the hydrogen lines in intensity ; the red 

 hydrogen line was the first to grow fainter. The weather 

 not having been very favourable, the measurements which 

 Herr Vogel made have no ciaim to very great accuracy, 

 but they at least prove that the following bris;ht lines 

 have appeared in the spectrum : — 



1. The hydrogen lines uo ! beyond doubt. 



Hy most probably. 



2. A line of 499 mill. mm. wave-length (± i mill. mm.). 

 This line coincides tolerably well with the brightest line in 

 the nitrogen spectrum under ordinary pressure ; it is the 

 same line which is brightest in the spectra of nebula;. 



3. An indistinct line of 580 m. mm. wave-length. 



4. An indi'itinct line of 497 m. mm. wave-length. This 

 nearly coincides with a close group of lines in the atmo- 

 spheric spectrum. 



5. Some bright lines were seen in the neighbourhood of 

 b and E, but their position could not be measured. On 

 December 5 two lines were measured in the blue (of 474 

 and 470 wave-lengths', and were also observed on Decem- 

 ber 8, but, later on, only the second one has again been 

 seen as an indistinct band of 467 wave-length. 



In the accompanying illustration (Fig. 2) we reproduce 

 Herr Vogel's drawings, which supplement his observa- 

 tions, and, as he points out, contain many a detail which 

 could not well be described in words. 



Herr Vogel, in discussing the views of other astrono- 



li... i.-Coinu's .Sptcirum of ^ov.^ Cjg,.i. 



mers, first deals with M. Cornu's observations. M. Cornu several bright lines in the spectrum, viz., wave-lengths, 

 made his first observations on December 2 and 5 (see 661 (Ha), 588, 531, 517, 500, 483 (H /i), 451, 435 (Hy). 

 Nature, vol. xv. p. 158); he succeeded in measuring He saw no dark bands distinctly in the] continuous 



