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THE NATIONAL GEOGRAPHIC MAGAZINE 



bearing, but there is not much likelihood 

 of its becoming a commercial source. 



HOW DOES HELIUM GAS HAPPEN? 



It is a pity that the story of helium can- 

 not be closed with a theory explaining its 

 origin and occurrence, but no satisfactory 

 theory has yet been suggested. Geolo- 

 gists believe that natural gas itself is a 

 product of the decay of the vegetable and 

 animal remains buried in the rocks ; but, 

 as helium is found also in mineral spring 

 and volcanic gases, this seems to have no 

 special significance. 



Some believe that the helium has arisen 

 from great depths in the earth and has 

 simply mingled with whatever gases it 

 happened to meet, but the largest volumes 

 of helium are found in regions remote 

 from any known fissures through which 

 the gas could ascend, and, furthermore, 

 it is difficult to understand why the helium 

 should rise almost to the surface and 

 there remain. 



There is, of course, an enormous vol- 

 ume, in the aggregate, of helium in the at- 

 mosphere (where it is about as valuable 

 as the gold in sea- water), but there is no 

 good reason to suppose that . the helium 

 in natural gas has been absorbed from 

 that source. 



THE RADIUM THEORY 



There is a third possibility, more at- 

 tractive and fascinating, perhaps, than 

 the other two, namely, that helium is 

 derived from radium. 



Every one now knows the wonderful 

 qualities of radium — its property of giv- 

 ing off heat enough to burn the flesh if 

 a tiny grain of radium is placed on it ; 

 its faculty of being luminous in the dark, 

 and so on. Radium is ordinarily con- 

 sidered one of the chemical elements, but 

 its discovery upset all the old notions 

 about the permanency and indivisibility 

 of the elements ; for the extraordinary 

 properties of radium are due to the fact 

 that it is continually breaking down, at 

 a slow, but constant, rate, into other sub- 

 stances. 



One of these substances is a gas called 

 radium emanation, and this in turn breaks 

 down into another body, called Radium 

 A, and so on through a whole chain of 



similar substances until it finally becomes 

 the unromantic element which we call 

 lead. 



This is only half the story, however, 

 for when radium breaks down into the 

 emanation, the other substance formed is 

 helium, and as each one of the other 

 radio-elements disintegrates it also gen- 

 erates helium. It is curious to reflect that 

 these changes are constantly proceeding, 

 even in the minute quantities of radium 

 in the luminous dials of our watches, and 

 that under our watch crystals infinitesi- 

 mal volumes of helium are being gen- 

 erated hourly. 



RADIUM WIDELY DISSEMINATED 



As the world's total output of refined 

 and purified radium amounts to only four 

 or five ounces, valued at over three mil- 

 lion dollars an ounce, it may well be asked 

 how so rare and precious a substance can 

 be called upon to explain the vast ac- 

 cumulations of helium in natural gas. 



As a matter of fact, however, although 

 deposits of radium ore rich enough to 

 mine are few, the element itself is widely 

 disseminated through ordinary rocks. 

 The quantities are so exceedingly minute 

 that were it not for the great activity of 

 radium, it could never be detected ; but 

 by the use of an instrument known as the 

 electroscope, incomparably more delicate 

 than the finest assayers' balance, the pres- 

 ence of only a few trillionths of I per 

 cent of radium in a rock may easily be 

 determined. 



The amount of radium in a pound of 

 rock or in a ton is utterly insignificant, 

 but the total quantity in a cubic mile is 

 enough to generate, according to a cal- 

 culation of mine, about half a cubic foot 

 of helium a year. This, too, sounds small ; 

 but multiply the cubic mile by a few thou- 

 sand and the year by a few million and 

 the total volume of helium begins to as- 

 sume formidable proportions. 



There is really little doubt but what 

 there is enough radium scattered through 

 the earth's crust to account for all the 

 helium we know of, though whether the 

 helium actually did originate in this way 

 is a matter concerning which scientists 

 disagree. 



INDEX FOR VOLUME XXXIV- JULY-DECEMBER, 1918-WILL BE MAILED TO MEMBERS 



UPON REQUEST 



