Masterpieces of Science 



travelling away from us at the rate of twenty- 

 five and one-tenth miles a second. In this 

 unique power oi detecting motion in the line of 

 sight, the spectroscope when furnished with a 

 sensitive film enormously enhances the revealing 

 power of the telescope. 



The sun was, of course, the first heavenly body 

 to have its spectrum caught on a sensitive plate. 

 In 1863 Dr. (now Sir) William Huggins attempted 

 to photograph the spectrum of a star. He ob- 

 tained a stain on his plates, due to the spectra of 

 Sirius and Capella, in which, however, no spec- 

 tral lines were discernible. In 1872 Dr. Henry 

 Draper, of New York, obtained a photograph 

 of the spectrum of Vega, in which four lines were 

 shown ; this was the first successful picture of the 

 series which Dr. Draper gave to the world during 

 the following ten years. Since his death, in 1882, 

 Mrs. Draper has established the Draper Memorial 

 at Harvard Observatory, for the continuance of 

 his labours on an extended scale. The photo- 

 graphs by this memorial owe much to the Vogel 

 method, by which the plates are sensitized for 

 green, red and yellow rays. Were this sensibility 

 to colour still further increased, the photographs 

 of stellar spectra would tell a yet fuller story than 

 they do to-day. Owing to irregular atmospheric 

 currents, the image of a star dancing around the 

 narrow slit of a spectroscope may elude even a 

 practised observer. Photography, with its 

 summation of recurrent impressions, gives a 

 perfectly uniform image of the composite type 

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