26 Dr Brewster on the Register of the Thermometer kept 



considered as giving nearly the mean of the year, and there- 

 fore as resembling each other in temperature, yet there is a 

 singular difference in the mode of its distribution. In Octo- 

 ber the mornings and evenings are comparatively warm, while 

 in April these times of the day are remarkably cold. April, 

 in short, unites the low temperature of a winter month with 

 the great range of a summer month ; while October unites 

 the temperature of a summer month with the low range of a 

 winter one. 



II. On the Determination of the two times of the Day when 

 the Mean Temperature occurs. 



I am not aware of any observations made in our climate, 

 by which the hours, when the mean temperature of the day 

 occurs, could be determined. It has generally been believed 

 that it occurs at 8 o'clock in the morning ; and Professor 

 Playfair not only considers this as nearly the hour of mean 

 temperature for Edinburgh, but he regards the maximum as 

 occurring " from 1 to half-past 2, or even 3 o'clock ;" and 

 upon these principles he has selected his three periods, viz. 

 8 a. m., the time of maximum, and 10 o'clock p. M. 



It appears, however, from Tables II. and IV., that the 

 mean temperature of the 24 hours occurs at the following 

 times : 



H. ' H. ' 



1924, 9 13 a. m. 8 26 P. m. 



1825, 9 13 8 28 



Mean of two years, 9 13 8 27 



This very extraordinary agreement between the results of 

 1824 and 1825, shows how nearly we have approximated to 

 the true form of the daily curve, and how much confidence 

 may be placed in the general result. The following may 

 therefore be regarded as the leading points of the annual daily 

 curve. 



Time of Minimum Temperature, a little before 

 Time of the Morning Mean Temperature, 

 Time of Maximum Temperature, - 



Time of Evening Mean Temperature, - 

 Interval between Minimum and following Maximum, 



