194 THE MECHANICS OF THE EARTh's ATMOSPHERE. 



Moreover, a is determined by the same equation as before, 



Finally, from the equation (9) 



C K3 = ('0 1 1 S t + t's — K- 



dz 



there results the followiuo-.- 



c-V3=coust+6i^'' j (-^+Xi ) cos'^ '9— x\ cos^ H \ 







This last equation allows of a direct comparison with the above-men- 

 tioned observations of the distribution of pressure. 



IV. 



The average values of the pressure of the air in the Southern Hemi- 

 sphere are given in the following table (under the column of observa- 

 tions) as a function of the latitude.* 



Air pressure at the earth^s surface. 



These pressures are fairly represented by an expression of the form 



p = 2)^-{- a cos^ d—h COS'* 6. 



If we determine the constants a and b from the observed values for two 

 difierent polar distances, for which I have used ^=50° and 6=20°^ 



then we obtain 



j; = 7oS+31.295 cos- ^-61.094 cos" 6. 



By the means of this formula the values given in the second columDy 

 under " computed," have been obtained. 



* See A. Sprung, Lehrbuch der Meieorologie, p. 193 ; J. van Bebber, Handbiich der 

 Witterungskunde, 11, p. 136. [These figures are taken originally from Ferrei, "'Meteo- 

 rological Researches," i, 1880. — C. J.] 



