LOCAL CLIMATOLOGY. 101 



except for a single clay, November 8th, when it is 41.13 (leg., with 

 extremes 64.5 cleg, and 29.5 cleg., and the average for the whole 

 twelve days is 45.64 deg ; but unlike the spring frost, the autunni, 

 or Indian summer grows warm to its centre, reaching an average 

 of 48.25 deg. on the first days in November, and then gradually 

 declining again to the temperature of the 27th of October. 



I have no means at my command for ascertaining how extensive 

 these phenomena of summer-frost and autunni-snnnner may be ; 

 nor is it easy to assign a cause for them that will bo, entirely mid 

 altogether satisfactory. I am inclined to think, however, that it 

 may be peculiar to our part of the Northern continent, as the 

 monsoons are to the Indian ocean. This inference, which I make 

 in the absence of all definite statistics, is of course purely theo- 

 retical, and derived from the views which I proceed to suggest of 

 the cause of this phenomena. 



Before proceeding, however, Avilh the theoretical explanation, 

 I would make a remark on the state of meteorological statistics 

 in this respect. Mere vague impression, based on personal feel- 

 ings and recollections, is a foundation for opinions in meteorology 

 at least, which one learns the more to distrust the more he has 

 occasion to deal w^ith it. Scarcely anything in my experience has 

 been more common than to find people's impressions of the gen- 

 eral average of the weather for a given period in conflict with the 

 observed and recorded facts. But again : the statistics as recorded 

 and summed up and reported in the published works on Climate, 

 afford no indication of such a retardation and retrocession of the 

 advance of the seasons ; nor do they, on the other hand, furnish 

 any indication that such phenomena do not occur ; for no average 

 but one like that I have made — an average for every day, day by 

 day, through a series of years — could show whether such an 

 event occurs or not ; and to m}^ knowledge, no such average has 

 before been made. An average for each month or each half- 

 month ; nay, an average for each week, even, would hardly draw 

 attention to the phenomena. 



And now for the explanation. I have referred to the ''wari- 

 ness " of the line of real temperature in the accompanying Diagram. 

 By referring to the Diagram again, we shall see that these two 

 chancres in the curvature of the line occur as the first iji'eat wave- 

 reactions after the equinoxes, when the sun, with the " balance of 

 loinds,''^ passes from one hemisphere to the other. Coming north 

 in the spring, the sun brings, or rather drives before it, the 



