82 president's address — section a. 



got one with one and a half hour's exposure. Two superposed 

 spectra are shown — one a continuous spectrum of reflected sun- 

 light extending from F to a little beyond H : the other two sets 

 of bright lines from the comet's own light, with a suspicion of the 

 Ijresence of a third set of lines. 



Dr. Henry Draper^* su.cceeded in photographing the comet b in 

 Aurigae on June 24th, 1881, in one exposure of two hours forty- 

 two minutes ; the comet is shown w4th tail about 10° long, and 

 several stars showing through it. He tried to get its sjDectrum 

 first, wdth a direct vision spectroscope and an exposure of eighty- 

 three minvites, which gave a spectrum of nucleus coma and tail, 

 then used a two-prism spectroscope, vpith three exposures, 180, 

 196, and 228 minutes. There is in the spectrum a heavy band 

 above H, which is riivisible into lines between G and h, and 

 another between h and H. 



M. Janssen*'* also secured a photograph of comet b on July 

 1881. He vised a telescope half a metre in aperture and r60m. in 

 focal length. The photograph was exposed for thirty minvites, 

 and shows a tail 2A^" long, in which were some rectilinear rays, 

 which Avere revealed by the camera, but not visible. It will be 

 remembered that, seven days before. Dr. H. Draper, vising a larger 

 telescope and more than five times the exposure, found the tail on 

 his photograph 10° long. 



On the 7th March, 1882, Dr. Huggins'^'' succeeded in taking a 

 photograph of the spectrum of the great nebulse in Orion. He 

 vised the 18in. reflector metallic speculum, and the exposure was 

 limited by clouds to forty-five minutes. The photograph shows 

 a spectrum extending from a little below F to beyond M in the 

 ultra violet ; there are five bright lines as well as a narrow^er con- 

 tinuous spectrum, which Dr. Hviggins thought was due to stellar 

 light. It may be mentioned that only four bright lines had been 

 seen by the eye. 



Dr. Draper", of New York, had been for eighteen months 

 taking photographs of the nebula in Orion — to see, first, if it 

 was changing, and, second, for the spectra of the various parts. In 

 March, 1H82, he made two good photographs with two hours' ex- 

 posure. On these he saw four of Dr. Huggins' lines, but not the 

 ■fifth (\3730). In one of the plates is the spectrum of a tenth- 

 magnitvide star — the smallest star that had so far had its spectrum 

 ;photographed. 



On May 31st, 1882, Dr. Huggins^^ obtained a photograph of the 

 spectrum of comet (Wells). It showed an essential difference 

 between the spectrum of this comet and others. The nucleus 

 shows a distinct spectrum, in which five brighter parts are seen, 

 .probably due to bright lines. The spectrum extends from F to a 

 little beyond H, and no Fiaunhofer lines can be seen in it. 



Professor Schuster's photographs of the eclipse of May 17th, 

 J-882, show the coronal light is very strong from about G to H ; 



