324 Mr. J. Rand Capron on the Auroral 



In the foregoing schedule of particulars I have not given 

 the dates of the ' Standard ' and ' Times ' newspapers ; but the 

 letters appeared within a few days of the 17th. 



Mr. Munro's letter (obs. 9) was addressed to the Secretary 

 of the Royal Astronomical Society (to whom I am indebted for 

 its loan), and contains a good deal of interesting matter in 

 connexion with the " beam " beyond the particulars abstracted. 



A primary question which presents itself in the subject 

 is, whether the "beam " was really and truly a part of the 

 auroral display, or a " meteor/' " meteoroid/' " cometary 

 body/' or something allied to any of these in contradistinction 

 to an auroral beam. Independently of other considerations, 

 two spectroscopic observations which have been recorded put, 

 I think, this point well beyond a doubt. In my own case 

 (obs. 2) I was using the spectroscope (a large Browning 

 direct-vision one) upon the aurora northwards, but, accidentally 

 turning and seeing the beam, I at once applied the instrument 

 to it. The spectrum (not to be found on the adjacent sky) 

 was observed to consist of the well-known principal citron 

 auroral line (W.L. 5569), and a faint greenish-white conti- 

 nuous spectrum extending from about D to F. No other 

 bright line than the principal one was visible ; and the con- 

 tinuous spectrum showed no trace whatever of Fraunhofer 

 dark lines — indicating an absence of solar reflected light. 

 The second observation was made by Mr. F. W. Cory, of 

 Buckhurst Hill, Essex, who in a letter to ( Knowledge ' 

 (vol. iii. no. 62) says: — "I think there can be no doubt in regard 

 to the connexion between the torpedo-shaped body that was 

 seen on November 1 7 at 6 h 5 m p.m. and the aurora, as the 

 spectroscopic examination gave the same line for both ; and 

 this was situated between D and E in the spectrum, but nearer 

 the former." That the aurora of the 17th was of the same 

 spectroscopic character with previously examined ones is 

 shown by the observations of (1) Mr. Cory, as above men- 

 tioned; (2) my own, I finding in the brighter parts the citron 

 line, and a few others indistinctly shown; (3) Mr. T. G. Elger's 

 (obs. 12), who in the pink portions of the aurora found the 

 usual red and green lines; (4) Dr. Wm. Roxburgh, of Bourne- 

 mouth, who, in a letter to Prof. Piazzi Smyth, states he found 

 five lines agreeing in position with those given by Prof. Smyth 

 in his plate of the auroral spectrum figured in the i Royal 

 Observatory of Edinburgh Observations/ vol. xiii.; and (5) Mr. 

 Henry Robinson (' Nature' p. 85), who saw the green line and 

 some others less distinctly in the blue and violet. 



Having disposed of this preliminary point, we will now turn to 

 the other incidents of the " beam " detailed in the twenty-six 



