THE SEASON WHY. 107 



If the clouds be full of rain, they shall empty themselves upon the earth." 

 ECCLES. xi. 



It is also supposed that the electrical state of the air and of the 

 clouds influences the formation of hail. 



449. Why is it supposed that the electrical state of the 

 air and the clouds affects the formation of hail ? 



Because hail is more common in the summer than at other 

 seasons, and is frequently attended by storms of thunder and, 

 lightning. 



450. Why do Tiail-storms most frequently occur ~by day ? 

 Because the clouds, being charged with vapour to saturation, 



favour the formation of hail by sudden electrical or atmospheric 

 changes. In the gradual cooling of night, the clouds would expend 

 themselves in rain. 



Astonishing facts respecting hail-storms are upon record. In 1719 there fell 

 at Kremo, hailstones weighing six pounds. In 1828 there was a fall of ice at 

 Horsley, in Staffordshire, some of the pieces of which were three inches long, by 

 one inch broad ; and other solid pieces were about three inches in circumference. 

 Hail storms are most frequent in June and July, and least frequent in April 

 and October. Hail clouds float much lower in the sky than other clouds ; their 

 edges are marked by frequent heavy folds ; and their lower edges are streaked 

 with white, the other portions being massive and black. (Fig. 10.) 



CHAPTER XXII. 



451. What is light ? 



Light, according to Newton, is the effect of luminous particles 

 which dart from the surfaces of bodies in all directions. According 

 to this theory, the solar light which we receive would depart from 

 the sun and travel to the earth. 



According to Huyghens, light is caused by an infinitely elastic 

 ether, diffused through all space. This ether, existing everywhere, 

 is excited into waves, or vibrations, by the luminous body. 



The theory of light is so undetermined that neither the views of Newton, 

 nor those of Huyghens, can be said to be exclusively adopted. Writers upon 

 natural philosophy seize hold of either or both of those theories, as they present 

 themselves more or less favourably in the explanation of natural phenomena. 

 In " The Reason Why," as we have to speak of the effects of light rather than 

 of its cav&e, we shall avoid, as far as possible, the doubtful points. But let no 



