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XII. Intelligence and Miscellaneous Articles. 



ON THE SPECTRUM OF THE AURORA BOREALIS. 

 BY JOHN BROWNING, ESQ, 



DURING the display of the Aurora Borealis which occurred on the 

 evenings of the 24th and 25th of October, I confined my atten- 

 tion to observing the spectra of the light, taking it in different parts 

 of the sky. When the spectroscope was directed to the more lumi- 

 nous portions, which were generally of a silvery white, the spectrum 

 appeared to me to consist of only one line. I could not succeed in 

 rerifying the position of this line ; but it appeared to be situated be- 

 tween D and E in the spectrum. When observing the light of the 

 red portions of the sky, a faint red line became visible. I had no 

 means of verifying the position of these lines with any degree of ex- 

 actitude ; but I was able to throw into the field of view a faint con- 

 tinuous spectrum from a distant light, and also the bright yellow 

 sodium-line produced by a spirit-lamp. 



The colour of the green line was very peculiar ; had I not bee 

 able to observe it by comparison, I could not have formed any idea 

 of its position. It was an exceedingly light silvery green, or greenish 

 grey, and often seemed to flicker. Besides the two lines I have 

 particularly described, I occasionally suspected others, one in the 

 red and one in the blue ; but I could not be at all sure of this. The 

 colour of the light of the aurora seen over the greater portion of the 

 heavens resembled exactly that of the discharge of electricity from 

 an induction-coil through a vacuum formed from atmospheric air. — 

 Monthly Notices of the Royal Astronomical Society, November 11, 

 1870. 



NOTE ON THE USE OF EYE-SCREENS IN TELESCOPIC AND OTHER 

 RESEARCHES. BY RICHARD A. PROCTOR, B.A. 



Most observers with the telescope keep the unemployed eye open 

 while studying with the other the features of an object in the tele- 

 scopic field of view. Closing the unemployed eye produces, in fact, 

 palpably injurious effects. But I suppose every one must have no- 

 ticed how much better the features of a faint object are seen, when 

 with the hand or any screen the unemployed eye is protected, 

 even though it be only from the luminosity of the star-lit sky. I find 

 that much better results are obtained when the unemployed eye is 

 guarded from the access of all light whatever by a screen lined with 

 black velvet. Yet better vision is secured if the screen is so con- 

 trived as to guard the employed eye also from all light except what 

 reaches it from the object. This can easily be managed by having 

 a screen covering both eyes, but with sliding doors, by which a 

 small circular aperture opposite either eye can be opened or shut 

 at will. Each aperture can have outside it a small tube passing 

 over the eye-tube of the telescope. Or (preferably for some pur- 

 poses) a small sleeve-curtain with an elastic circular opening at one 

 end can be attached at the other over either eye-aperture. Then if 



