438 Notes. 



ter attains its maximum elevation about 9 o'clock A, M., after which 

 it descends till about 4 P. M., when it is at its minimum ; from this 

 time it rises till near 11 P. M. when it reaches its maximum again, 

 after which it commences a downward motion till 4 A. M. ; and 

 thence it begins to return to the state first mentioned. This march 

 is often deranged in European climates, where the atmosphere is so 

 variable ; but under the tropics where the causes which act upon 

 the atmosphere are more constant, the periodical changes are regu- 

 lar, and to such a degree that, according to Humboldt, one may 

 almost predict the hour of the change at any time from a single ob- 

 servation ; and what is very remarkable, these changes, according 

 to the same distinguished philosopher, are not affected by any atmo- 

 spherical circumstance ; neither the wind, nor rain, nor fair weather, 

 nor tempests, disturb the perfect regularity of these oscillations. They 

 are found to be the same in all weathers and at all season?. For 

 further particulars relative to the construction of the barometer and 

 the theory of its fluctuations, the student is referred to Daniel's 

 Meteorological Essays. 



THE END. 



