CLIMATOLOGY. 325 



gation of this law'has always been an especial object of my 

 researches. ( 399 ) 



Since we have obtained a somewhat more exact knowledge of 

 the distribution of heat on the surface of the earth, namely, 

 of the inflections of the isothermal, isotheral, and isochim- 

 enal lines, and of their unequal distances apart in the 

 different systems of temperature of Eastern and Western 

 Asia, of central Europe, and of North America, it is no 

 longer admissible to ask as a general question, to what fraction 

 of the mean annual or mean summer temperature a change of 

 one degree of geographical latitude, taken in a particular 

 meridian, corresponds. In each system of isothermal lines 

 of equal curvatvfre, there reigns an intimate and necessary 

 connection between three elements ; the decrease of heat in 

 a perpendicular direction from below upwards, the variation 

 of temperature corresponding to a change of one degree of 

 geographical latitude, and the relation which exists between 

 the mean temperature of a station on a mountain, and the 

 latitude of a point situated at the level of the sea. 



In the system of Eastern America, the mean annual tem- 

 perature varies from the coast of Labrador to Boston 0.88 

 Cent. (1.58 Pah.) for each degree of latitude ; from Boston 

 to Charleston 0.95 Cent. (1.71 Pah.) ; from Charleston to 

 the tropic of Cancer in the island of Cuba, the variation 

 diminishes, being only 0.66 Cent. (1.19 Pah.) Within 

 the tropic the diminution decreases to such a degree that 

 from Havannah to Cumana, the variation is not more than 

 0.20 Cent. (0.36 Pah.) for each degree of latitude. 



In the system of isothermal lines of central Europe, the 

 case is quite otherwise. Between the parallels of 38 and 

 71, I find the decrease of temperature to be with considera- 



