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KNOWLEDGE cV SCIENTIEIC NEWS. 



(■June, 1904. 



ji rays of radium exhibit just these properties, only 

 they move even more rapidly, sometimes, indeed, 

 several times as rapidly as the electrons in the cathode 

 stream, and are more penetrative. Hence the ,3 rays 

 may be considered to be " electrons." 



The a rays were the last discovered. These are far 

 heavier than the others, and are very easily stopped. 



Fig. S- — Taken without bags, at a distance of 4 cm. and with 

 5 hours' exposure. The dark shadow on the reader's left was 

 produced by uranium : above it was a crystal of fluor spar 

 The rectangle at the top was caused by glass, and the dark 

 object below this was a threepenny bit. 



They can be deflected by powerful magnets, and the de- 

 flection is in the opposite sense to that of the rays of the 

 cathode stream, which shows they carry positive charges. 

 Sir \\'illiam Crookes has shown us how to recognise 

 them by letting them strike screens covered with phos- 

 phorescent zinc sulphide, as in the " spinthariscope." 



Such substances as fluor-spar, kunzite, diamond, 

 willemite, and barium platino-cyanide become luminous 



Fig. g. — .\ necklace of various jewels set in metal. No bag. Taken 

 with a rapid plate in three and half hours at a distance of 44 cm 



if the rays of radium fall upon them, much as they do 

 under the influence of cathode rays, the effects produced 

 being exceedingly beautiful. 



The Emanation of Radium. — If radium be heated strongly, 

 or if it be dissolved in water, a substance is given ofT which 

 mixes with gases, and which, when freed from impurities, 

 has the properties of a gas. This substance can be con- 

 densed at the temperature uf liquid air in a glass tube, 

 and is then phosphorescent. It can be re-evaporated. 



Its removal deprives the radium of 70 per cent, of its 

 heating power, and the energy of the emanation is so 

 great that it is calculated that if a whole cubic centimetre 

 could be collected in one place it would probably melt the 

 containing vessel. It is radio-active, and therefore must 

 be supposed to be in a state of change, like radium. 



The transformation of radium into its emanation and 

 the connection between this change and the radio-active 

 phenomena which accompany it have been investigated 

 by Professor Rutherford. The phenomenon, as it appears 

 to him, occurs in several successive stages. The heavy 

 atoms — for radium has very heavy atoms — of radium dis- 

 intregrate, throwing off positively charged particles, whose 

 masses compare with those of hydrogen atoms, whilst 

 new forms of matter lighter than radium remain behind, 

 occluded as it were in the remaining radium. These re- 

 sidues are also radio-active and undergo further change of 

 a similar kind stage after stage until at last a, ,if, and 7 rays 

 are all expelled. 



Professor Rutherford suggested on certain grounds that 

 probably helium would be found among the products of the 

 disintegration of radium, which led Sir William Ramsay 

 ind Mr. Soddy to seek it. They find that though the 



FiG. 10.— No bag was used in this case Rapid plate. Distance 

 44 cm. Time of exposure, two hours. 



emanation of radium when first liberated by dissolving a 

 radium salt in water contains no helium, yet this element 

 may be detected in the same emanation after a few days. 

 For the present, therefore, we regard helium as the ulti- 

 mate product of the disintegration of radium, or at least 

 as the only such product yet detected. 



The discovery of radium and of its unique properties 

 raises some important questions : — 



I. — Whence does radium derive its vast supply of 

 energy ? It has been suggested by some that it acts as 

 a transformer, picking up energy in some way from its 

 environment and giving it out again as light, heat. Sec, 

 in the course of its disintegration. Another school (and 

 this predominates at present) regards radium as a 

 form of matter endowed with relatively vast stores of 

 potential energy ; and it has even been suggested, origi- 

 nally, I believe, in order to compose certain differences 

 between the physicists and the geologists on the subject 

 of the age of the sun, that the energy of the sun would be 

 accounted for by the presence of no more than three or 

 four grams of radium in each cubic metre of its substance. 

 Though, except such evidence as may be derived from 

 the presence of helium in the sun, we have not much 

 actual fact to support this latter hypothesis. 



One of the latest contributors to this most interesting 

 problem is Lord Kelvin, who finds the second hypothesis 



