56 TREES AND TREE-PLANTING. 
heat radiated from the earth is retained within ten feet 
of the earth’s surface by the vapor held in the atmos- 
here. 
“4, It is found that during the night-time the atmos- 
phere becomes sensibly warmer to the height of one 
hundred and fifty feet, as shown in the following 
table: 
“Let the thermometer upon the grass represent zero, 
and at one inch above the grass it will read three degrees 
higher; and 
At 6 inches above the grass it will read 6 higher. 
“ 1 foot “ “ Oe ‘e q “ 
«© 42 feet “ “ 6 sc “ce 8 “ce 
oe 50 feet “ “ss ce ce 6k 6c 10 zi 
6é 150 feet oe ce “a 46 £¢ oe 12 he 
You will notice that two thirds of the entire rise of tem- 
perature occurs below twelve feet, and five sixths of the 
increase in temperature below fifty feet. That is, the 
vapor within fifty feet of the earth is five times more 
important to vegetable life than that contained within 
one hundred feet above that point, and the vapor within 
twelve feet of the earth’s surface has twice as much in- 
fluence upon climatic conditions as one hundred and 
thirty-eight feet of atmosphere above that point. 
“These facts lead us at once to the conclusion that, 
as far as vegetable life is concerned, we are most inter- 
ested in the condition of the air within twelve or fifteen 
feet of the earth’s surface, and that a vapor-laden atmos- 
phere near the surface of the earth, not subject to vio- 
lent commotion, must be a matter of the gravest moment. 
“Now it is well known that vegetable life, as well as 
the earth itself, is sending off continually a vast amount 
of vapor into the atmosphere. Every spear of grass 
and every leaf is pumping up the moisture from the 
earth, and sending it forth into the air in the form of 
vapor, thus giving the earth a glassy covering, opaque 
to radiated heat of a low intensity. The amount of wa- 
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