RADIUM, ATOMIC ENERGY, AND ATOMIC STRUCTURE 547 



disputable fact. It is true that we have not yet discovered any 

 simple means of disintegrating the more common elements (see, 

 however, p. 17). We cannot even control in any way the rate of 

 disintegration of radioactive elements (see p. 545). If, however, 

 some method of inducing or hastening radioactive changes on 

 a large scale is devised in the future, a wonderful new source of 

 power will be put into our hands, namely, atomic energy. 



The energy change in radioactive disintegrations is enormously 

 greater than in ordinary chemical reactions. One gram of radium, 

 as already mentioned, would evolve about 120 cal. per hour, and 

 would continue to evolve this heat, at a gradually decreasing rate, 

 for centuries. The total heat available would be over 2,000,000,000 

 cals. per gram, whereas a gram of carbon burning to C02 gives 

 only 8040 cals. The disintegration of a pound of uranium salts 

 would furnish enough power to drive an ocean liner across the 

 Atlantic, but 8,000,000,000 years is entirely too long to wait 

 for the completion of the trip. Chemists are already looking 

 forward, however, to the possibility of using the enormous stores 

 of energy here available so soon as a catalyst for the reaction is 

 obtained. 



Another interesting by-product of this subject is the calcula- 

 tion that the heat given off by the disintegration of the radium 

 known to exist in the earth (niton is found in the soil and in well 

 waters) is sufficient alone amply to account for the maintenance of 

 its temperature. A globe the size of the earth, possessing orig- 

 inally only heat energy, and cooling from a white-hot condition 

 to the temperature of interstellar space, would have passed 

 through the stage of habitable temperatures in a much shorter 

 time than that which geological deposits and fossils show to have 

 been actually available. The discovery of the enormous, but 

 gradually released, disintegration energy of radium, enables us 

 now to explain the prolonged period during which life has existed 

 irl the earth. 



This energy is derived from within the atom itself, by re-arrange- 



