264 THE POPULAR SCIENCE MONTHLY. 



looking at the corona through, screens of colored glass or other 

 absorptive media had not been satisfactory. The author had 

 therefore undertaken to use photography, and had satisfied him- 

 self that under certain conditions of exposure and development, 

 a photographic plate could be made to record minute differences 

 of illumination existing in different parts of a bright object, 

 which was so subtle as to be at the very limit of the power of 

 recognition of a trained eye, and even, perhaps, of those that sur- 

 passed that limit. Describing his apparatus and method, he 

 showed that it was possible, by isolating through properly chosen 

 absorbing media, the light of the sun in the violet part of the 

 spectrum, to obtain photographs of the sun surrounded by an 

 appearance distinctly coronal in its nature. He afterward found 

 that, by using plates sensitive to violet light only, it was possible 

 to do away with absorbing media and remove the difficulties that 

 occurred in sifting the light. In 1886 Dr. Huggins accounted 

 for his failure to obtain in England, since the summer of 1883, 

 photographs showing satisfactory indications of the corona, by 

 the existence in the atmosphere since the autumn of 1883 of finely 

 divided matter which caused an abnormally large amount of 

 glare. Mr. Ray Woods had met the same trouble in Switzerland 

 in the summer of 1884. 



In his British Association address, 1891, Prof. Huggins re- 

 peated a conclusion which he had expressed in 1885, that the 

 corona is essentially a phenomenon similar in the cause of its 

 formation to the tails of comets consisting for the most part 

 of matter going from the sun under the action of a force, pos- 

 sibly electrical, which varies as the surface, and can therefore 

 in the case of highly attenuated matter easily master the force 

 of gravity even near the sun as according with the lines along 

 which thought had been directed by the results of subsequent 

 eclipses. 



In the early part of 1868 Prof. Huggins presented to the Royal 

 Society some observations on a small change of refrangibility 

 which he had remarked in a line in the spectrum of Sirius as com- 

 pared with a line of hydrogen, from which it appeared that the 

 star was moving from the earth with a velocity of about twenty- 

 five miles a second, if the probable advance of the sun in space 

 were taken into account. The thought of discovering motion in 

 this way was not wholly new, though Prof. Huggins was the first 

 to apply it in practice. The Rev. John Mitchell, of the Royal 

 Society, presented an ingenious paper, in 1783, On the Means of 

 discovering the Distance, Magnitude, etc., of the Fixed Stars, in 

 Consequence of the Diminution of the Velocity of their Light, in 

 which he suggested that by the aid of a prism " we might be able 

 to discover diminutions in the velocity of light as perhaps a hun- 



