32 



SCIENCE. 



[Vol. I., No. 2. 



of his own hands. It was intended and nsed 

 successfully for the purpose of photographing 

 the spectra of stars. As President Barnard 

 has said, " it was probably the most • difficult 

 and costlj'' experiment in celestial chemistrj'' 

 ever made." It was with this instrument 



that in August, 1872, he first succeeded in 

 obtaining a photograph of a star-spectrum, 

 showing its characteristic lines : the star 

 was Vega, and the lines were those of hj'dro- 

 gen. Since then he has taken the spectra of 

 more than a hundred stars, and at the time of 

 his death was preparing to push the work 

 much farther. Most of the later photographs 

 were made with an exquisite refractor of eleven 

 and a half inches aperture, by Clark & Sons. 



This telescope, which he has found much more 

 convenient than the reflectors, is provided 

 with a special correcting lens for photographic 

 work ; and it was with this that he made those 

 wonderful photographs of the nebula of Orion, 

 which were the fruit of his long and weary 



labors during the two last winters. For the 

 most part he was accustomed to carrj- on his 

 astronomical work in the summer, while resid- 

 ing at his country-seat on the Hudson ; in the 

 winter he generally- spent most of the time in 

 the cit3", and ga^■e himself mainlj' to labora- 

 tory research. In 1872, as a first step towards 

 the interpretation of stellar spectra, he made 

 a photograph of the diffraction spectrum of 

 the sun, extending from below G to O. Others 

 have since then taken pictures of small por- 

 tions of the spectrum on a larger scale ; but 

 his photograph still remains classical and 

 standard, and is recognized as such, abroad as 

 well as here. 



In 1874 he was invited hj the Transit of 

 Venus commission, to superintend its photo- 

 graphic department ; and he did so with such 

 success, that on the completion of his labors 

 the United-States government caused a spe- 

 cial gold medal to be struck in his honor at the 

 Philadelphia mint. Upon the face it bears 

 the inscription, " Decori decus addit avito ; " 

 on the reverse, " Famam extendere factis, 

 hoc virtutis opus." 



Next he took up his famous research as 

 to the presence of the non - metals in the 

 solar atmosphere, and in 1877 published his 

 jDaper announcing the discover}" of oxygen iu 

 the sun. The investigation was exceedingly 

 protracted and laborious, and involved an 

 expense of several thousand dollars : it w'as 

 carried out by means of photography, several 

 hundred plates having been made, which show 

 the solar spectrum confronted with that of the 

 gas. In these plates we find the diffuse, hazj', 

 bright lines of the oxygen spectrum coincid- 

 ing, not with dark lines of the solar spectrum, 

 but with certain brighter bands or interspaces. 

 How this can be, it is far from easy to explain, 

 — Yi\\j oxygen alone should act in this unpre- 

 cedented waj-. Naturall}' there has been 

 some scepticism and discussion as to the cor- 

 rectness and soundness of his conclusion ; 

 but no one with an unprejudiced mind can, 

 we think, resist the evidence after careful 

 examination of the plates, especially those 

 obtained during his second, and still more 



