136 THE SEASON "WHY. 



' He directeth it under the whole heavens, and his lightning unto the ends of 

 the earth. 



589. WJien is the flash of lightning straight ? 



When the distance between the clouds whose electricities are 

 meeting 1 , is small. 



590. What is the cause of the aurora borcalis ? 



The mingling of the electricities of the higher regions of the 

 atmosphere. 



591. \Vhen does the flash of lightning appeal blue? 



When the degree of electrical excitement is intense, and general 

 throughout the atmosphere. 



592. Why does lightning sometimes appear red, at othert 

 yellow, and at others white ? 



Because of the varying humidity, which affects the refracting 

 power of the atmosphere. 



593. Does lightning ever pass upwards from the earth to 

 the clouds ? 



Yes ; when the earth is charged with a different electricity to 

 that which is in the clouds. 



594. Does lightning ever pass directly fi-om (he clouds to 

 the earth ? 



Yes ; when the electricity of the clouds seeks to combine with 

 the different electricity of the earth. 



The mingling of the electricities of the earth and the air must he continually 

 going on. But lightning does not attend the phenomena, because all natural 

 bodies, vapours, trees, animals, mountains, houses, rocks, &c., &c., act more or 

 less as conductors between the earth and the air. It is only when there is a 

 great disturbance of the electrical forces, that terrestrial lightning is developed. 

 AVhen lightning strikes the earth with great force, it sometimes produces what 

 are called fulgurites in sandy soils; these are hollow tubes, produced by the 

 melting of the soil. 



595. What is the extent of mechanical force of lightning? 

 Lightning has been proved, in one instance, to have struck a 



church with a force equal to more than 12,000 horse- power. A 

 single horse-power, in mechanical calculations, is equivalent to 

 raising a weight of 32,000 Ibs. one foot in a minute. The force of 



