66 THE REASON WHY. 



1 Give unto the Lord the glory due unto his name ; worship the Lord in tha 

 beauty of holiness."- PSALM xxix. 



235. What is the cause of sea Ireezes ? 



Sea breezes are also the result of convection. The land, under 

 the heat of the day's sunshine, becomes of a hig-h temperature, and 

 the expanded air on its surface fries away towards the ocean. As 

 the sun goes down, the earth cools again, and the air flies back to 

 find its equilibrium. 



Many countries by the sea are subjected to these periodical breezes, known 

 as either " land" or " sea breezes," according to their direction. About eight 

 o'clock in the morning au aerial current begins to flow from the sea towards 

 the land, and continues until about three o'clock in the day ; then the current 

 takes a reverse direction, flowing from the land to the sea. This it continues to 

 do throughout the night, until the time of sun-rise, when a temporary calm 

 ensues. 



236. Why does a soap bubble ascend in the air ? 



Because, being- filled with warm air, it is lighter than the 

 surrounding medium, and therefore ascends. 



237. Why does the bubble fall after it has been in the air 

 some time ? 



Because the air contained in it has become cool, and, as it 

 contains carbonic acid gas, it is heavier than the air. 



233. What became of the warmth at first contained in the 

 bubble ? 



It has been distributed in the air through which the bubble 

 passed. 



239. IVliat does this simple illustration of the distribution 

 of war mill explain ? 



It explains the law of convection, or heat distribution, over the 

 surface of the globe. 



240. Why does air ascend the chimney ? 



Because, being heated, it becomes lighter than the surrounding 

 medium, and therefore flies upwards, through the outlet provided 

 for it. 



211. WTiy does air fly from the doors and windows towards 

 the fire-place ? 



