XVI INTRODUCTION. 



temporary struggle that the author places before the reader, 

 the casus belli being neither more nor less than the nature 

 of the chemist's atom. The nature of the atom may seem 

 at first sight to be too abstruse and remote to enter into the 

 sphere of practical interest. Such a hasty judgment would 

 be unwarranted. The atoms of matter are the bricks of 

 the universe, out of which you and we and the Milky Way 

 and the Dog Star are all made up. What affects the atom 

 affects us. As a matter of fact, there is nothing esoteric 

 about it and little that is abstract. The knowledge is ap- 

 prehendable enough and vastly important. Locked up in 

 it is the cause of the heat of the sun, together with the nature 

 of electricity, the evolution of a universe and the birth and 

 decay of matter. There are also, possibly, a cure for tubercu- 

 losis, light without heat, a demonstration of vast stores of 

 energy hitherto unsuspected, beside which the forms of en- 

 ergy with which we are acquainted are absolutely insignifi- 

 cant, and a whole series of radiations heretofore unknown 

 from matter in the natural state. Ten years ago men talked 

 with extreme positiveness about this and that; a famous 

 litterateur, even, wrote a comprehensive treatise on "The 

 Bankruptcy of Science " in which he proved (sic) that every- 

 thing essential and possible of knowing was known, and that 

 all that remained was mere detail. It is proper to say that 

 the answer of science to this tremendous indictment was in 

 deeds, not words, for there came in rapid succession Hertz' 

 discovery of electro-magnetic waves, Moissan's revolu- 

 tionary work with the electric furnace, Rontgen's X-rays, 

 Rayleigh's and Ramsay's discovery of the rare gases of the 

 atmosphere, and Dewar's liquefaction of hydrogen. Finally, 

 there has come, as most upsetting to all preconceived ideas, 

 the famous discovery of Becquerel and the Curies, which in 

 itself and in its consequences forms mainly the subject- 



