PNEUMATICS. 299 



Thus, 



y = G 4- F sin (A 30). 



This supposes the mean heat to take place about a 

 month after the equinox, and the extremes about 

 a month after the solstices. In this latitude we 

 may suppose F = 15 . 



407. From this formula, compared with the two 

 former, one theorem may be deduced, including the 

 effects of the latitude, the elevation above the sur- 

 face, and the season of the year, viz. 



n(A 30); 

 270 



Where y is the mean temperature for any day of the 

 year, in the latitude L, and at the elevation H. 



408. The formula for the mean temperature, as 

 laid down above, would probably hold over the 

 whole globe, if it were every where covered by the 

 ocean ; but it agrees strictly only with the At- 

 lantic Ocean, and the western part of the Old Con- 

 tinent. 



The editor of MAYER'S Posthumous Works observed, 

 that his theorem applied accurately only to the 

 3 portion 



