16 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



Scotland. He saw Angstrom's line very constantly, and also 

 a red line of wave length 635. He notes as very curious that 

 the blood-red, lurid red, and tragedy red of the painters ap- 

 peared very markedly to the naked eye, and yet were not 

 seen at all in the spectroscope, either as a new ingredient or 

 an altered place of the red line. Excessively faint greenish 

 and bluish lines appeared at wave lengths 490, 510, and 530, 

 but 8-10ths of the light in the spectroscope came from Ang- 

 strom's line, and most of the remainder from the red line 635. 



M. Cornu, of Paris, makes nearly the same remark with 

 Professor Smyth, that, notwithstanding the aurora was of a 

 brilliant red to the naked eye, when the light was analyzed 

 by the spectroscope the green line was far brighter than the 

 red line. He undertook to compare the lines with those of 

 hydrogen, but before his apparatus could be got ready the 

 display had vanished. 



Mr. Prozmowski saw, besides these lines, two other bands 

 in the blue and violet, near F and G. These were seen in the 

 white parts of the aurora ; they disappeared or became very 

 faint in the parts having an intense red tint. 



Great difficulty is found in identifying these lines with any 

 produced by artificial means. Angstrom considered that for 

 this reason the theory that the aurora was simply electricity 

 moving through rarefied air would have to be given up. But 

 other physicists are not disposed to go so far as this until 

 more careful experiments are made on the influence of the 

 temperature and pressure of gases upon their spectra. It 

 was once supposed that the Angstrom line in the aurora was 

 identical with that seen in the solar corona, and on this sup- 

 posed identity w T as founded a theory that the corona is a so- 

 lar aurora. But it is now known that the two lines are en- 

 tirely different, the w T ave length of the coronal line being 530, 

 while that of the auroral line is 557. 



DETERMINATION OF HEIGHT OF AURORAS. 



Dr. J. G. Galle, director of the observatory at Breslau, cele- 

 brated as being the first to recognize the planet Neptune in 

 the telescope, has lately given a new method of determining 

 the height of the aurora. It is founded upon the hypothesis 

 that the rays which form the auroral crown are parallel to 

 the magnetic pole. The deviation from apparent parallelism 



