298 OUTLINES OF NATURAL PHILOSOPHY. 



This line at the equator is elevated 15577 feet above 

 the level of the sea ; so that for determining n we 



n KPJ77 



have 32 = 58 + 37 or n _ 394 

 w 



Thus, H = 7642 + 7933 cos 2 L, and this seems 

 nearly to agree with actual observation. 



Professor LESLIE has given a different equation, found- 

 ed on the law of the diminution of heat mentioned at 

 339. In the table calculated from it, heights 

 come out rather below what observation requires. 

 Elements of Geometry, 2d edit. p. 495. 



On great elevations, the variations of temperature 

 from day to night, and from summer to winter, ap- 

 pear to be less than at the surface. SAUSSURE, 

 torn. iv. p. 



406. The temperature of the latter end of April 

 is observed, at least in the temperate zone, to be 

 nearly the mean temperature of the year. From 

 that time the heat increases, and is at its maxi- 

 mum about the 21st of July ; it goes on decreasing 

 from that time till it come to the mean in the end 

 of October, and it passes from thence to the great- 

 est cold about the 21st of January. All these vi- 

 cissitudes may be nearly represented by the for- 

 mula in which G is the mean temperature for the 

 given place, F a constant co-efficient to be found 

 by observation, X the mean longitude of the sun 

 computed from the first of Aries, for any day of 

 the year, the mean temperature of which is y. 



Thus, 



