STELLAR SYSTEMS AND NEBULA. 209 



tected in the spectrum of the Orion nebula the 

 yellow ray of helium. On February 13, 1890, 

 Scheiner announced an important discovery, 

 namely, the possession by both the nebula and 

 the stars in Orion with the exception of Betel- 

 geux of a line, which appeared bright in the 

 nebular spectra and dark in the stellar. This 

 line was identified by Vogel, Lockyer, and others 

 with that of helium. 



Nebular photography was inaugurated in 1880 

 by Draper, who obtained a remarkably good 

 representation of the Orion nebula in that year. 

 His work in this direction, cut short by his 

 death in 1882, was taken up by Janssen at 

 Meudon, and by Common in England, who 

 obtained, in 1883, several excellent photographs. 

 Later photographs have shown the Orion nebula 

 to be much more extended than visual observa- 

 tions would lead one to expect. A photograph 

 secured in 1890 by W. H. Pickering revealed 

 the nebulous matter in Orion in its true form, 

 that of a gigantic spiral, starting from near 

 Bella trix, sweeping past K Orionis and Rigel to 

 17, and joining with the great nebula surrounding 

 0; the entire constellation being thus shown to 

 be enwrapped in nebulous haze. 



In 1885 nebular photography was commenced 

 by Isaac Roberts (1829 - 1904), the English 



