TABLES OF DIFFERENCES OF MEAN TEMPERATURES. 157 



4| A. M. or about one hour and a half he/ore sunrise. The epochs of mean daily 

 temperature are subject to less variations with respect to latitude than the epochs 

 of the daily extremes. In the Arctic regions the mean temperature of the day is 

 reached about 8 A. M., in the temperate regions about 9 A. M., and again about 

 7J P. M. arid about 8 P. M. respectively. 



The material for the discussion of the daily fluctuation for stations in the Missis- 

 sippi valley and in the western states and territories is yet wanting. 



The annual variation in the range of the daily fluctuation is shown in the follow- 

 ing table. From want of completeness in the records the tabular numbers, in many 

 instances, are the result of interpolation, and they can only be considered as close 

 approximations. 



Monthly means of the range of the daily fluctuation. 



GRour I. 

 Arctic Regions. 



Group II. 

 Alaska. 



Canada and N. 

 New York. 



4 Stations. 



Groups IV &V.' 



Mass., Conn., 

 Penn.,D. of C. 



Group VI. 

 Gulf Coast. 



January- 

 February 

 March . 

 April 

 May . . 

 June 

 July. . 

 August . 

 September 

 October 

 November 

 December 



3-0 

 9-2 

 8.6 

 8.6 

 7.8 

 5-7 



4.2 



3-5 



2.2 



1-7 

 I.O 



6-3 



8.9 



10.9 



12.0 



14.0 



14.9 



iS-4 



14.6 



12.5 



10.3 



5-9 



5-3 



10 4 

 II. 2 

 13.6 

 14.8 

 17.0 

 17.2 

 15.8 

 14.9 

 16.6 

 16.2 

 II. I 

 9.8 



Omitting Brooklyn as too irregula 



Diagram C. 













Diagram 



D. 

















— 





— 







^= 



=3 



=d 



= 



:= 



iS 



16 



1 



1 



^ 



1 



^ 



§ 



^ 



P 



i 



^ 



= 



= 



14 



ID 



^ 



1 



M 



M 



= 



^ 





M 



M 



== 



1 



^ 



8 







— 



— 



— ' 



^ 



M 



= 



M 



1 





M 



m 



6 



M 



= 



= 



^ 



4 



— 



: 





== 



= 



— 



: 



— 



= 



=^ 



^= 



^^^- 



2 

 





M 



M 





^= 



^= 



= 



— 



^ 



== 



= 



Group 

 IV &V. 



Group 

 VI. 



J. F. M. A. M. J. J. A. S. O. N. D. J. 



J. F. M. A. M. J. J. A. S. O. N. D. J. 



At all stations, of the above table, between the Gulf of Mexico and the Arctic 

 Sea, the daily range is a minimum in December ; this, however, is the only feature 



