RADIUM AND ITS PRODUCTS 189 



influence of the /3-rays. On investigation, it was proved 

 that more than one substance had been produced. For 

 on bubbling air through the water, a radioactive gas 

 passed away along with the air ; it had the power of dis- 

 charging an electroscope, but its life lasted only a few 

 seconds. It was only while the current of air was passing 

 through the electroscope that the gold-leaves fell together; 

 on ceasing the current, the leaves remained practically 

 stationary. Now had radium emanation been introduced 

 into the electroscope, its effect would have lasted twenty- 

 eight days ; had the emanation from thorium been intro- 

 duced, it would have taken about a minute before it ceased 

 to cause the gold-leaves to fall in. There is an emanation, 

 however, that from actinium, which is very short-lived, 

 and it looks probable that one of the substances produced 

 from the /3-rays is actinium. But it is not the only one. 

 For the water with which the glass was washed gives a 

 radioactive residue after evaporation to dryness; and it 

 contains a substance which forms an insoluble chloride, 

 sulphide, and sulphate, though the hydroxide is soluble in 

 ammonia. Either, then, the /S-rays have so altered the 

 constituents of the glass that new radioactive elements are 

 formed ; or perhaps it is the air which surrounds the glass 

 which has yielded these new elements; or it may be, 

 though this appears less probable, that the /3-rays them- 

 selves, which are identical with electrons, or ' atoms ' of 

 negative electricity, have condensed to form matter. 



Such are some of the results which have been obtained 

 in a chemical examination of the products of change of 

 radium. The work is merely begun, but it leads to a 

 hypothesis as regards the constitution of radium and 

 similar elements, which was first put forward by Ruther- 

 ford and Soddy. It is that atoms of elements of high 

 atomic weight, such as radium, uranium, thorium, and the 

 suspected elements polonium and actinium, are unstable ; 



