METEOROLOGY. 



289 



Table of the Hours of Mean Temperature and the ^^ critical interval" 



between those hours. 



Date. 



1857. 



January 22 



February 23 



March 22 



April 29 



May 22 



June 22 



July 22 



August 28 



Septemlier 23 



October 21 



Novemlxr 27 



Decerabt-r 23 



Mean. 



Daily mean. 



4S. 50 

 53. 75 

 50.38 

 Gl 88 

 62.46 

 69.83 

 75.63 

 05. 21 

 64. OS 

 58.50 

 53.58 

 43.50 



Morning hour. 



30 



10 45 



8 41 



9 53 

 7 30 



7 33 



8 54 



7 36 



8 42 



9 38 

 10 47 

 10 45 



Evening hour. Critical intervaL 



It. m. 

 12 30 

 10 15 

 9 19 

 9 7 

 8 16 

 6 

 41 

 47 



12 

 9 



8 



8 



8 



9 55 



9 15 



35 

 30 



10 46 



12 20 



One of the most striking features of tlie climate, seen on the accom- 

 panying chart of diurnal variations, is the greatest reduction of tem- 

 perature after the hour of maximum elevation. Howsoever high the 

 wave of temperature towers up under the influence of a vertical sun 

 and cloudless sky, it sinks proportionately low during the night, 

 rendering it conl and chilly. As an instance of the reliability and 

 freedom from exaggeration of the curves of temperature in this respect, 

 we would remark that the record of the thermometrograph for July, 

 1857, reveals a range of 41 degrees, and a mean daily range of 18.68'. 

 degrees, while the chart of diurnal observations describes a curve of. 

 only 24 degree-. The following table exhibits the successive hourly 

 ranges during one day of each month in the year. 



19 s 



