366 NATURE-STUDY REVIEW [14:9— Dec, 1918 



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In the full moon these shadows are shortened and the light 

 places we see are the white shining rock of mountains while the 

 dark places are rocks of a different color. The old astronomers 

 gave them very fanciful names, such as the Bay of Rainbows, the 

 Lake of Dreams. They did not know as we do now, that all 

 these valleys, lake beds, or craters as they may chance to be, were 

 without a drop of water. 



We are told and it has been proven that our atmosphere is 

 about 200 miles high, some parts of it being much thicker than 

 others because it is compressible, pressing on us, as they will teach 

 you in physics class, with a pressure of nearly 15 pounds to the 

 square inch. 



A good way to realize what it is like on the moon without any 

 blanket of atmosphere is to know some of the things our cushion 

 of air does for us. If we were to climb up some exceedingly high 

 mountain, like Mt. Everest, or go up in an aeroplane we should 

 find that the farther up we went the colder it would become; 

 we should notice this more after we were above the clouds, for 

 they act as heat curtains to us, keeping in the heat that comes down 

 to us from the sun and acting at the same time as a screen to 

 protect us from its scorching rays. Many a traveler's face has 

 been scorched by the sun, even in those high places where the air 

 is so bitterly cold. We know that water in a blackened bottle, 

 has been boiled by the sun's rays at a height of about 1 100 feet. 



Now if through our air blanket 200 miles thick, we can be 

 scorched by the sun, or frozen with the cold, how terrible it must 

 be on the moon, which has no blanket of air, and no screen of 

 clouds. The heat of the sun's rays is 500 degrees above zero, 

 and they would fall on the moon five times hotter than they do 

 here on the hottest day of summer when the thermometer stands 

 at one hundred in the shade, and horses and people fall dead from 

 sun-stroke. How long do you suppose they could stand the heat 

 on the moon? Then at night because the moon has no blanket 

 to keep the heat from getting away from her quickly, she cools 

 down to 250 degrees below zero. This is cold enough to freeze 

 air solid. 



Here is a jar with an air pump, which I have borrowed from the 

 physics department, it has a bell in it suspended from a string. 

 Can you all hear the bell ringing ? Now one of you may use this air 

 pump and pump the air out of the jar ; now ring the bell. What, 



