198 FOOD FOR PLANTS 



foot of the earth amounts to two thousand one 

 hundred and sixty pounds. An ordinary sized man, 

 supposing his surface to be fourteen square feet, sus- 

 tains the enormous pressure of thirty thousand, two 

 hundred and forty pounds. 



The barometer falls one-tenth of an inch for every 

 seventy-eight feet of elevation. 



The violence of the expansion of water when freez- 

 ing is sufBcient to cleave a globe of copper of such 

 thickness as to require a force of 27,000 pounds to 

 produce the same effect. 



During the conversion of ice into water one hun- 

 dred and forty degrees of heat are absorbed. 



Water, when converted into steam, increases in 

 bulk eighteen hundred times. 



In one second of time — in one beat of the pendu- 

 lum of a clock — light travels two hundred thousand 

 miles. Were a cannon ball shot toward the sun, and 

 were it to maintain full speed, it would be twenty 

 years in reaching it — and yet light travels through 

 this space in seven or eight minutes. 



Strange as it may appear, a ball of a ton weight 

 and another of the same material of an ounce weight, 

 falling from any height will reach the ground at the 

 same time. 



The heat does not increase as we rise above the 

 earth nearer to the sun but decreases rapidly until, 

 beyond the regions of the atmosphere, in void, it is 

 estimated that the cold is about seventy degrees be- 

 low zero. The line of perpetual frost at the equator 

 is 15,000 feet altitude; 13,000 feet between the 



