1852.] THE AURORA NOTICED. 173 



ment of drift snow preventing the floating or curvature 

 of the ice at the crack, where it appeared to be very 

 thick ; it gaped about eighteen inches above, but it was 

 too close below to admit of measurement. 



On the evening of the 2nd of December, about nine 

 P.M., the first well authenticated aurora was observed. 

 All our instruments being then available, I was anxious 

 to ascertain its effect on them. Mr. Cheyne was di- 

 rected to report on the electrometers, and I add his re- 

 marks, as I believe he was called in time to see it in part. 



" SIR, Last night, at 9.20, I observed an Aurora : a light narrow 

 streak extended from the summit of the Observatory Hill, passing im- 

 mediately through the zenith, in a direction south-by-east true, termi- 

 nating in a feather about 25 north of the zenith (?). Four cumulus- 

 shaped masses appeared as though only about a couple of hundred feet 

 from the mast-heads ; these masses lasted about three minutes, and 

 then suddenly disappeared, having apparently shifted their position 

 about twenty feet during that time ; the long streak gradually vanished 

 in about eight minutes. 



" The magnetometer read 116 '50, was perfectly steady, nor was the 

 electrometer in the least affected. The sky was perfectly clear. 



" (Signed) J. P. CHEYNE, Lieutenant. 



"Decembers, 1852." 



Mr. Cheyne was not an observer : he probably took 

 this 116'50 from the register for nine hours,* which is 

 there so recorded, but he could not judge of the steadi- 

 ness of the magnetometer: at eight it was 117'30; at 

 ten, 120-60. But it is not clear to my mind that it 

 was not affected, and that the causes which produced 

 this aurora had not been in action the last eight hours, 

 viz. from four P.M. until midnight, when it reached 



* All terms of time refer to astronomical periods from noon to noon. 



