OF ARTS AND SCIENCES. 



238 



rectiug lens fitted to be placed in front of the object-glass to adapt it 

 to photographic work. 



At fii-st, and until 1879, wet collodion plates were Uf^ed iu all these 

 experiments; after that date, he used exclusively the dry plates of 

 Wratten and Wain w right, to which, during a visit to England in 1879, 



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the attention of Dr. Draper wa"^ called by Dr. Huggins, whose ad- 

 tnirahle work in the same line of research is so well known to every 

 one interested in 8uch matters. 



As will be easily unrlerstood. these operations upon stellar spectra 

 were by no means carried on continuously, but only during Di- Draper's 

 summer residence at his country place, and in the intervals of other, 



