120 Disturbance of the Needle during an Aurora. 



at twenty five minutes past twelve, vanishing, after appearing to move 

 westward, about 60° west of north. The general light to the north 

 was still bright, and at half past twelve the most luminous point was 

 about 15° west of north. At one o'clock, the aurora had almost 

 ceased, there being still a feeble and diffuse light to the north. A 

 dark cloud (cumulo stratus) occupied a portion of the horizon, hav- 

 ing above it two smaller clOuds of the same description ; in the inter- 

 vals between these clouds, and to the eastward of the one in the hor- 

 izon, the feeble light was seen. 



In the following table of observations on the magnetic needle, the 

 results which belong to the horizontal needle are referred to the same 

 point, as a zero, to which those in May were referred ; this point is 

 not the mean of the days immediately preceding and succeeding the 

 tenth of July, but a reference to it renders the resuhs of the pres- 

 ent series immediately comparable with that for May. In the obser- 

 vation of the dipping needle, I have been perplexed by a defect, of 

 which this is not the place to give an account, but which it is neces- 

 sary for me to allude to, as explaining why the observations of that 

 needle, made prior to half past ten P. M., are not given : those which 

 are set down, I have referred to the first observation recorded, as a 

 zero ; as differential results, I believe them to be worthy of confi- 

 dence, although not in the same degree with the corresponding ones 

 for the horizontal needle. The differences marked + correspond 

 to an increase of dip, and those marked — to a decrease. In the 

 column of remarks the different phases of the aurora are briefly re- 

 ferred to. 



