i 



^ 



»< 

 \ 



»* 



^ 



I 



Sect. IX.] 



METEOnOLOGY 



303 



The observer will find it botli interesting and instructive 

 in a high degree to project the reduced observations (as 

 fast as reduced, or monthly) of the barometric pres- 



(the value of F 



iL^ 



mentioned), 



curves, by the aid of a paper of 

 engraved' squares, divided into inches and tenths by 



and temperature, m 



vertical and horizontal lines. 



The comparison of the 



case 



tension is of especial interest, since there is great reason to 

 believe that the diurnal fluctuation of the barometer is 

 mainly, if not entirely, a hygrometric phenomenon arising 

 from the superaddition of a variable hygrometric pressure 

 to the otherwise uniform pressure of the dry atmosphere. 

 The course of the barometric curve too will show far 

 better than simple observation the chief maxima and 

 minima which indicate the passage of the crests and 

 troughs of atmospheric waves. And its continuance at a 

 high or low level, or its gradual diange, corresponding 



over Ion 



progressive 



latitude and longitude, will enable the observer to trace 

 out the limits of those deviations from the simple law of 

 statical equilibrium which the researches of Schouw, 



Humboldt, and others have proved to exist more or less 

 over the whole globe, and which those of Ermann in the 

 Arctic, and King and Ross in the Antarctic regions have 



local 



to the 



enormous amount of a whole inch in the mercurial column. 



* Such papers may be obtnined from Messrs. W, H. Allen and Co., 

 Booksellers to the Honourable East India Company, No. 7, Leadenhali- 

 street, London. 









J ^* 



