THE RATE OF DECREASE OF TEMPERATURE, ETC. 83 



atmosphere with increase of height is least in low, and 

 greatest in high latitudes ; and 2nd, that the rate of de- 

 crease is greatest in the summer, and least in the winter 

 months. Some results, however, which I obtained in the 

 course of an investigation of the relations which exist 

 between falls of rain and changes of barometric pressure, 

 and of the decrement of temperature of the atmosphere in 

 different localities, led me to doubt the general correctness 

 of the second of these conclusions, and I have therefore 

 examined all the observations that were accessible to me 

 that seemed likely to throw any light on the subject ; and I 

 have obtained some results which seem to prove the existence 

 of a belt in the temperate latitudes of Europe and Asia, 

 in which the decrease of temperature for a given ascent in 

 the atmosphere is greatest in the winter months, while at 

 stations north or south of this belt, so far at least as ob- 

 servations have yet been made, the decrease is greatest in 

 the summer months. 



This belt passes over Portugal, Spain, Sicily, Southern 

 Italy, the Caucasian provinces, and Southern Siberia. 



Bywell and Allenheads Stations. 



The only trustworthy observations made in England at 

 stations differing considerably in altitude, and not too far 

 apart in a horizontal direction, which I have yet met with, 

 are those made at Bywell and Allenheads in Northumber- 

 land, under the direction of Mr. T. Sopwith, F.E.S. The 

 difference of elevation of the two stations is 1273 ^^^^y 

 and the mean temperatures of the winter and summer 



quarters and the differences are — 



Winter Summer 



Quarter, Quarter. 



ByweU 387 58-5 



Allenheads 34*9 53*4 



Differences 3*8 5'i 



o2 



