176 



Capt. H. P. Dawson. 



[Dec. 20, 



limits of their scales. On the first of these days the difference 

 between the extreme easterly and westerly positions of the declino- 

 meter magnet exceeded 10°. 



Aurora. 



Aurora was observed on almost every clear night, and was usually 

 attended by more or less magnetic disturbance. It did not appear to 

 me, however, that the two phenomena stood in the relation of cause 

 and effect, but rather that they were both due to a common cause. 

 The most marked instance of connexion between the two phenomena 

 consisted in a rapid decrease in both vertical and horizontal magnetic 

 forces which attended a sudden outburst of aurora in the zenith. This 

 was observed on several occasions. The bifilar almost always showed 

 a reduction of horizontal force during a display of aurora. I also 

 think that the declinometer magnet tended to point towards the 

 brightest part of the aurora, but I have not yet had time to make 

 that careful comparison of the auroral and magnetic observations 

 which will be required to decide this point. It was found impossible 

 to obtain photographs either of the aurora or of its spectrum — the 

 latter invariably presented the characteristic yellowish-green line, and 

 occasionally but rarely several other bright lines were visible for a 

 few moments towards the violet end of the spectrum, and once a 

 bright band was seen in the red. 



I was also unsuccessful in my attempts to measure the height of 

 the aurora, chiefly from the want of a well-defined point to measure 

 to, also from the fact that some hours were required to prepare for 

 this observation, whereas the appearance of a suitable aurora could 

 not be predicted, and was, in fact, not of frequent occurrence, and 

 then often only lasting a few seconds. For this observation two 

 stations some miles apart should be connected by telegraph and 

 occupied for many days, or even weeks in succession. 



Although I paid attention to the point, I never heard any sound 

 from the aurora, save on the occasion mentioned in a former memo- 

 randum, but I made many inquiries on the subject from residents in 

 the country, both English and French, and their statements agree so 

 well, both with one another and with what I myself heard, that I am 

 forced to conclude that the aurora is at times audible, and that on 

 these occasions it appears to be, and probably is, very near the 

 earth. 



Meteorological Observations. 



With regard to the meteorological observations, the station was 

 somewhat unfavourably placed for observations of wind, on account 

 of the hill to the north-east, but as winds from this quarter were rare 

 the effect on the results will not be great, especially as one of the 



