126 NOMOS. 



earth to the depth of 185 feet. Of this amount, it 

 is calculated that the sun supplies as much as would 

 melt 100 feet, and the stars the rest. What, then, 

 may we ask, will be the effect of this amazing 

 amount of heat upon the earth ? That it must melt 

 ice and convert water into vapour is 

 obvious, but is this the sole effect ? Is 

 there no action upon the land ? In con- 



?robabieef- sidering this question we may leave out 

 fects of this altogether the effects of sidereal heat, not 

 because these effects are inconsiderable in 

 themselves, but because they do not present those 

 appreciable alternations of action which of necessity 

 belong to the solar heat. In the case of the heat 

 proceeding from the sun, it is evident that all parts 

 of the earth cannot be acted upon at once, and that 

 the differences of action cannot be inconsiderable if 

 the amount of heat be as great as there is reason to 

 believe it to be. In other words, the hemisphere of 

 the earth which is exposed to the light will be 

 affected very differently to that which is in the 

 shadow. But there can be none of these differences 

 in the action of the sidereal heat, because this heat 

 streams equally and constantly upon all sides of the 

 earth at once, and not upon a single hemisphere, as 

 is the case with the solar heat. 



In estimating the action of solar heat upon the 

 earth, it is evident that the action upon land will 

 differ from the action upon water. In a hot day, as 

 every bather knows, the land is very much hotter 

 that the water. Nor is this to be wondered at, for 

 the water is converted into vapour almost as fast 



