726 The Outline of Science 



upon the apparently impregnable position of the "permanent 

 gases" should have been recorded in the laboratory of the 

 Royal Institution, where the first successes in this field were 

 won by Faraday. 



Transmutation of Elements 



The chemists or alchemists of the Middle Ages sought after 

 "the Philosopher's Stone," which would transmute "base metal," 

 such as lead, into gold. Some even believed that their quest was 

 successful, for the science of chemistry was not far enough 

 advanced to dispel their illusions. If a knife-blade be placed in 

 a solution of blue vitriol or sulphate of copper, it comes out like 

 copper; and, as Professor James C. Philip points out, "to the 

 alchemist the result admitted of no other explanation than that 

 the iron had been converted into copper. We know now that 

 no such change takes place: some copper comes out of the 

 solution and is deposited on the surface of the iron, while by way 

 of holding the balance even, an equivalent amount of the iron 

 passes into solution." 



The transmutation of one element into another was dis- 

 credited when the science of chemistry began to get on its feet, 

 and, just as naturalists believed in "the fixity of species," so 

 chemists believed in the immutability of the elements. Each ele- 

 ment is itself and no other. But everyone knows the change of 

 view that the discoveries of the twentieth century have brought. 

 It is now established that the element uranium may in part change 

 into radium and some other elements. A spontaneous change 

 occurs, associated with the partial disintegration of the uranium 

 atom, which leads to the formation of minute quantities of radium 

 (apparently with ionium as an intervening link) . From another 

 changeful radio-element, namely, thorium, there may also be 

 derived at a very low rate minute quantities of radium. It appears 

 that the uranium and thorium give off particles of helium, an 

 element first detected in the sun and restricted as far as the earth 



