52 ANDREW JACKSON HOWE. 



example of the kind. In elevated places where the 

 atmosphere is diffuse, the resistance ottered to the 

 passage of solar rays is inconsiderable, but'^n valleys 

 where the air is condensed through pressure of the 

 mass above, the friction is great, and the resultant 

 heat is intense. 



The old theory of solar combustion as a source of 

 heat is untenable for several reasons, the most prom- 

 inent of which is that the great luminary would have 

 burnt itself out long ago; and another is that as only 

 its planetary bodies and their satellites are recipients 

 of the benefit, stellar space would consume much the 

 larger amount. 



In the summer when the sun is overhead, the 

 impact of solar rays is greater than in winter when 

 the>un shines slantingly. A sun-glass converges solar 

 rays into a focus, and thus multiplies the friction, 

 intensifies the heat at a given spot. The moon has 

 no atmosphere, hence solar rays falling upon it meet 

 with no resistance evolve no heat. 



The suggestion of Proctor that the sun's fires are 

 fed by inflowing meteors as fuel, is also a gratuity. 

 As meteorites become scarce, the heat would decrease 

 a lack of supplies would have been felt long ago. 

 Besides, in the combustion of so much coarse material, 

 what would become of the ashes or debris ? 



There seems to be but one rational account of the 

 origin of solar heat, and that is through friction. If 

 that be the source of the sun's beating energy, it is to 

 last as long as our atmosphere does, hence may be re- 

 garded as abundant and eternal. 



