140 



through countless ages of time is not given a moment's thought. Figuring 

 this way, if we can manufacture ice a penny a ton cheaper than we can 

 harvest the natural ice, we proceed to burn coal to make it. Think of 

 the waste. Burning coal to make ice, when all the ice we need could be 

 had for the harvesting. You say that natural ice is not produced in the 

 tropics. Neither is artificial ice. in any quantities. 



We flood our streets with oil. because we think it a cheap way of 

 keeping down the dust ; cheap only because we fail to consider the energy 

 content of the oil and what it has cost Nature to produce it. The time 

 will come when such extravagance will be prohibited by statute. 



The fact is that we fail to realize that oil and coal are a legacy 

 that has come to us from bygone ages, deposited in Nature's bank. We 

 are spending our substance in riotous living, but unlike the prodigal have 

 no place to go when it is all spent. Doubtless something will fall on 

 our neck, but there will be no fatted calf. 



The writer has painted a gloomy picture, such a picture as would have 

 been painted twenty years ago, with dark clouds hanging everywhere 

 about the horizon. However, the picture needs but one change to represent 

 the conditions today. There is a rift, a small rift, in the clouds ; a rift 

 that may close and leave us again with leaden and ever darkening skies ; 

 a rift that may open wider and wider and leave us finally with the glorious 

 sunshine of a cloudless sky. Whence the rift? 



The energy content of matter depends on position and motion, not 

 only on the position and motion of the mass as a whole, but upon the po- 

 sition and motion of the constituent parts. Experience tells us that the 

 energy liberated during any change is relatively greater the smaller the 

 parts taking part in the change. For instance : the energy required to 

 change a gram of water into steam, a change of position of the molecules, 

 is twenty times as great as the energy of a speeding rifle bullet of the 

 same mass. To effect an atomic change, that is, to separate the hydrogen 

 and oxygen atoms which form the water molecules, requires five . times 

 the energy involved in the molecular change. When the atom itself 

 breaks up, disintegrates, relatively enormous quantities of energy are 

 liberated. 



Radium is a substance in which this electronic or sub-atomic change is 

 going on continuously and spontaneously. It is continually throwing off 

 or radiating minute particles, and so we say that radium is radioactive. 

 A mass of radium gives off enough energy every hour to melt more than 



