318 THE MECHANICS OF THE EARTH'S ATMOSPHERE. 



■when be reflects that all the hypotheses introduced into the computa- 

 tion (the neglect of the vertical motion, of the friction, and of the dif- 

 ference bet wnen a day and the interval between two lunar cnlmina- 

 tions) contribute to increase the computed tidal ebb and flow. \Vitl> 

 reference to the last mentioned diflerence, I might further remark that 

 it is easily introduced into the computation. The ratio 3 to 1 betweeu 

 the lunar tide and the solar tide as assumed by Laplace holds good 

 only so long as the value i/c (in which the dei)th of the ocean or the- 

 temperature of the air enters in the respective i)roblems) is far from a 

 certain critical value which lies between 11.1 and ll.li. With 4A = 10 

 the ratio in question is 2.11 to J, but with 4A = 11.1 the ratio becomes 1 

 to 5. 



1 tlo not carry out the computation here, because it seems too liyi)0- 

 thetical to compare the atmosphere with a si)herical shell of i)erfectly 

 detinite temperature, and under this assumption then to consider tins- 

 semi-diurnal variation of pressure as a consequence of the solar attrac- 

 tion. Much more probable is it that it arises from a regular constitu- 

 ent of the semi-diurnal variation of temperature. 



