STANDS SCIENCE WHERE SHE DID? THOMAS 243 



lias measured the intensity of cosmic radiation 750 feet below the 

 surface of Lake Constance; and he has sent up balloons with self- 

 recording instruments to a height of ITI/2 miles. Professor Piccard, 

 of Belgium, has himself made two personal ascents into the strato- 

 sphere at great risk to his life. Professor Compton, of the United 

 States, has organized expeditions to 81 stations all over the world 

 at heights from sea level to 20,000 feet. Professor Kolhorster has 

 gone down into a Prussian salt mine and brought back evidence 

 of cosmic rays, four times as hard as the most penetrating discov- 

 ered by Professor Regener, which are capable of maintaining the 

 electric charge of the earth. 



But the mystery of the cosmic rays is still unsolved. A few years 

 ago it was confidently thought that cosmic rays were of the same 

 nature as light, only with very much shorter wave length. They 

 were placed at the lower end of the gamut of radiation which was 

 thought to run : wireless waves, heat waves, infrared ray3, light, 

 ultraviolet rays, X-rays, gamma rays, and cosmic rays. On this basis 

 several novel theories to account for their origin were proposed. 

 Sir James Jeans thought they were the product of tlie complete 

 transformation of matter into energy " annihilation." Professor 

 Millikan thought they were liberated when helium was formed out 

 of hydrogen somewhere in space. The Bishop of Birmingham 

 thought it " not wholly improbable " that mixed up with the cosmic 

 rays were messages from beings on other planets in a more advanced 

 state of development than ourselves. 



Since then physicists have become less confident of the nature of 

 cosmic rays. Most investigators now think they are not of a wave 

 nature, but consist of electrified particles, possibly electrons. That 

 takes away the ground from under those who would see in cosmic 

 radiation the birth-cry or death-rattle of an atom, or an interstellar 

 broadcasting service. If cosmic radiation does consist of electrified 

 particles, it will be attracted towards the earth's magnetic poles, 

 and it becomes important to decide by experiment whether that is so. 

 Professor Compton's ex[)editions do show that the intensity of cosmic 

 radiation is greater in temperate than in tropical latitudes. The 

 result is not wholly decisive, but what we know as cosmic radiation 

 is almost certainly a mixture. Apart from the primary cosmic rays 

 there are the secondary rays formed when the primary rays strike 

 the earth's atmosphere. Cosmic radiation may consist not only of 

 many rays of different intensity, but may include corpuscular and 

 wave parts. The radiation, it may be added, appears to be nearly 

 constant in time at any one place; as it is the same by night as by 

 day, the sun can hardly be its origin. 



Another reason for the in decisiveness of the theory of cosmic rays 

 is the compaiative rarit}' of the rays on the earth's surface. But when 



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