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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 
