CHAPTER I. 



THE HEAT OF THE SUN. 



THERE is not in the whole range of modern science a more 

 fruitful subject for. discussion than the sun and his con- 

 nection with the earth. In the first place it is the func- 

 tion of the sun's attracting power to constrain the earth 

 to follow that orbit in which she performs her annual 

 revolution. The same office is also filled by the sun in 

 the guidance of the several planets which, like our earth, 

 are controlled by the one great central power. There are 

 other functions in which the sun appears to be more 

 obviously our benefactor by contributing several of the 

 necessaries for our welfare. Chief among these is his 

 provision of the heat by which life is sustained. The 

 study of the benefits conferred on us by the sun in this 

 particular opens up most interesting questions. As the 

 great dispenser of light to the surrounding worlds, the 

 functions of the sun illustrate other branches of science. 

 Indications of the sun's interference in terrestrial affairs of 

 somewhat minor moment are not wanting. The swing of 

 the magnetic needle is connected in some occult manner 

 with sunbeams, and phenomena of this class seem destined, 



