LOCAL CLhMATOLOGY. 91 



day, tilikc in suinmcr juul in winter, the earth receives more Iiejit 

 than it radiates, and in the night it radiates or sends oil' more than 

 it receives, as is shown by the fact that it is warmer in the evening 

 than in the morning. 



As showing the ratio of heating and cooling, I have made a 

 comparison and average for the twelve years during Avhich niv 

 records are complete. I subtracted the average for the mornino- 

 for each month from its average for the evening, and then made 

 an average for all the tAvelve years, with the following result : 



Month. Ditfcrcnce. Month. Difference. 



Jan. 1.5(r'F. July o.04^ F. 



Feb. 1.72 Aug. 2.23 



Mar 2.05 Sep. 2.22 



Apl 3.42 Oct. 1.55 



May 2.32 Nov. 1.5() 



June 2.50 Dec. 1.01 



The morning observation is taken at seven o'clock, and there- 

 fore in winter before the air has begun to get warmer, though in 

 summer some change has doulitless taken place in that direction. 

 If, therefore, we w^ere to take the observation earlier, it would 

 diminish the subtrahend for the summer; but the observation for 

 the evenin<r is taken at nine p. m., after coolinsr has been o:oin<x on 

 much longer in the winter than in tie sununer. If, therefore, w^e 

 were to take the observation earlier in the eveninij for the winter, 

 it would add something to the minurend for that season ; and 

 thus probably the result would be about as it now stands, if the 

 observation "were taken in summer before the heating of the day, 

 and in winter before the cooling for the night had made any con- 

 siderable progress. We see that the average difference between 

 the night and the morning temperature for the summer, 2.89 deg., 

 is nearly double that for the w^inter, 1.64 deg. 



The most remarkable phenomenon presented b^'the above com- 

 parison, however, is the great difference betw^een the morning and 

 evening temperatures in the month of April, being then 3.42 deg. 

 greater than at any other time in the year. I am not of course 

 able to say w^hether that be a pecnliarity of this special locality, 

 or not. During the month of INlarch there are usually more 

 cloudy days than in April, and also much snow and ice to thaw 

 away ; both of wdiich causes would prevent the atmosphere from 

 becomino^ so warm at eveniuf^ as it would otherwise be. These 

 obstacles being removed, the topmost stratum of the earth's crust 



