ALLISON FLUCTUATION OF THE BAROMETER. 159 



month excepting March and April ; in the former of which it fell 

 considerably, and in the latter slightly below the average. None 

 of the excesses were large, and consequently the whole year's mean 

 of 8.67 miles per hour was but .83 over the average mean. 

 November was absolutely the most windy month in 1875 ; which 

 result accords with my previous 13 years observations, although the 

 normal of March approaches very closely. But last year as noticed 

 that was comparatively a quiet month. August was, as usual, the 

 month of least wind. 



While from the large rain-fall of the summer 1875, may be 

 remembered for its wetness, the total precipitation of the year was 

 in reality very close to the average 52 inches of Halifax. The 

 whole rain was nearly an inch deficient, owing to the abnormal 

 scarcity in January, March, September and December, which the 

 excess in June and July, and, remarkably, in October did not com- 

 pensate. Snow, on the contrary was very plentiful in January and 

 February, but scarce in March and notably wanting in December. 

 The whole depth exceeded 87 inches dry, being 5. 5 above the 

 normal; this when melted raised the total precipitation to 51.480. 

 The number of days of rain was 134. Snow fell on 54 days, while 

 198 days were completely dry — a dry day is that on which the pre- 

 cipitated moisture does not reach ; .01 of an inch is in fact inappre- 

 ciable ; of such days 204 is the normal annual allowance in Halifax, 

 10 days more than the average number in London, about the driest 

 district of Great Britain. 



The aurora borealis was seen much less frequently than usual- 

 Since October, 1874, there has been a remarkable scarcity of these 

 displays, which still continues. Several years ago I laid before this 

 Institute what I believed to be the causes of the visibility of this 

 phenomenon, noting that it was invariably accompanied by a fall 

 in temperature, generally great and frequently sudden. Longer 

 experience has confirmed this belief. I have said that the display 

 is not simply electric; because, however, the existence of the aurora 

 is due to electric force, we on this earth can only know of its exist- 

 ence — can only see it, in short — when a lately decreased tempera- 

 ture of our atmosphere brings the display to our vision. In how 



