148 OUTLINES OF FORESTRY. 



ance of several layers of dark, grayish clouds. In 

 most all cases, before the beginning of a hail-storm, 

 a violent movement is seen to take place between 

 these layers, apparently of a whirling character. 

 Generally, too, hail-storms are attended by violent 

 disturbances in the electrical equilibrium of the 

 atmosphere, as is evidenced by the frequent dis- 

 charge of the lightning-bolt and the almost con- 

 tinual roar of thunder. Then follows a fall of 

 hailstones, the size of which is much larger at the 

 beginning and towards the middle of the storm 

 than towards the close. Towards the close of the 

 storm, however, the quantity of hail which falls is 

 greatest. 



If a hailstone be examined by cutting it in two, 

 it will be seen to consist of alternate layers of ice 

 and snow laid over one another in successive coats 

 like the layers of an onion. A cross-section of a 

 hailstone can be made by holding it against the 

 surface of a hot plate until half of the stone has 

 been melted away. 



Hailstones vary in weight from a few grains to 

 several pounds. Records exist of hailstones weigh- 

 ing many pounds, sometimes of even several hun- 

 dred pounds. In such cases, however, it is more 

 than probable that the stones were produced by 



