BAROMETER. 349 



the level of the sea, is the same all over the earth, 

 amounting to the average of about thirty inches. 



2. The density or specific gravity of the atmos- 

 phere, increases gradually from the equator to the 

 regions of loivest mean temperature, corresponding 

 with the decrease of temperature ; the consequence 

 of which is, that the height of the atmosphere must 

 diminish from the equator to the poles. 



3. Within, the tropics, the temperature is always 

 nearly the same : the range of the barometer is also 

 small, varying from two lines to a quarter of an 

 inch. 



4. The range of temperature augments from the 

 equator to the regions of maximum cold : the vari- 

 ation of the barometer augments in a corresponding 

 ratio, amounting to about three inches in the 

 coldest latitudes. 



The range of temperature is much greater in 

 North America than in the same latitudes of 

 Europe, as will appear from the following facts. 

 During the winter of 1831 and 32, the thermome- 

 ter fell to -- 20 at Florence, in the State of Ala- 

 bamo, lat. 35 N. and 40 at Plattsburg, lat. 

 44, where it sometimes rises to 95, and even 

 100 during summer, making its extreme annual 

 range from 130 to 140 F.* The diurnal variation 



* It is however but seldom, that the temperature falls below 

 in the States, south of Philadelphia and New York ; so that 

 the usual annual range of temperature does not much exceed 

 that of England, which is about 80, according to Mr. Daniell ; 



