486 



Dr. and Mrs. Hugging. 



[May 19, 



I. "On Nova Aurigee." By William Huggins, D.C.L., LL.D., 

 F.R.S., and Mrs. Huggins. Received May 16, 1892. 



[Plate 4.] 



We had the honour in February last of communicating to the 

 Royal Society a short preliminary note on the remarkable spectrum 

 of this temporary star. We beg now to present a fuller account of 

 our observations, together with two maps of the spectrum of this star, 

 and some theoretical suggestions as to its nature. One map represents 

 the result of our work by eye in the visible region ; the other map 

 has been drawn from a photograph of its spectrum, taken without 

 its light having passed through glass, and which extends into the 

 ultra-violet nearly as far as the absorption of our atmosphere permits 

 even the solar rays to pass. 



On the Visible Region of the Star's Spectrum. 



The kindness of Professor Copeland in sending us a special 

 telegram on February 1 enabled us to commence our observations of 

 the star on February 2, when it was of about the 4'5th magnitude. 

 These observations were continued on the following evening, and on 

 the 5th, 6th, 22nd, and 24th February, and on the 15th, 18th, 19th, 

 20tb, and 24th March, when the sky was more or less sufficiently clear 

 for further observations to be made by eye. On the two ends of the 

 spectrum the observations were usually made with a spectroscope 

 containing one dense prism of 60°, but the comparisons in the 

 brighter parts of the spectrum were observed with a more powerful 

 spectroscope containing two compound prisms. 



Comparisons ivith Hydrogen. — Three bright lines of great brilliancy, 

 about the positions H«, H/3, and H y , left little doubt that they were 

 due to hydrogen. The corresponding lines of a hydrogen vacuum 

 tube were found to fall upon these lines, showing that they had 

 their origin in this gas; but the line in the star at F, which 

 could be best observed, showed a large shift of position towards the 

 red. The line from the vacuum tube fell not upon the middle of the 

 line, but near its more refrangible edge. The star line was brighter 

 on the more refrangible side, so much so, indeed, that our first im- 

 pression was that this side of the line only might be truly Hjs, and 

 the less bright part towards the red, a line of some other substance 

 falling near it. Subsequent observations of the hydrogen lines in 

 the star left no doubt that though they presented the unusual 

 character of being double, and sometimes triple, they were due wholly 

 to hydrogen. These lines were rather broad, but defined, especially 

 so at the more infrangible edge. Similarly to what is observed in 



