236 MODERN VIEWS ON MATTER. 



The spectrum of radiuiii has several well-detined lines; these I have 

 photoo-raphed and have also measured their wave lengths. Two espe- 

 cially ai-e stronj^- and characteristic — one at wave length 3649.71, and 

 the other at Wave length 3814.5s, These lines enal)le radium to be 

 detected spectroscopically. 



The most striking property of radium is its power to pour out tor- 

 rents of emanations l)earing a certain resemblance to llcintgen rays, 

 but differing in important points. 



The emanations of radium cause soda glass to assume a violet color, 

 and they produce many chemical changes. Their physiological action 

 is strong, a few milligrams brought near the skin in a few hours 

 producing a wound difficult to heal. 



The emanations from radium are of three kinds. One set is the 

 same as the cathode stream, now identified with free electrons — atoms 

 of electricity projected into space apart from gross matter — identical 

 with "matter in the fourth or ultragaseous state," Kelvin's "satel- 

 lites," Thomson's " corpuscles" or "particles;" Lodge's " disembodied 

 ionic charges, retaining individuality and identit}"." These electrons 

 are neither ether waves nor a form of energy, but substance possess- 

 ing inertia (probably electric). Liberated electrons are exceedingly 

 penetrating. They will discharge an electroscope when the radium is 

 10 feet or more awa}', and will affect a photographic plate through 

 5 or 6 millimeters of lead and several inches of wood or aluminum. 

 They are not readil}^ filtered out by cotton-wool; they do not behave 

 as a gas, i. e., they have not properties dependent on intercollisions. 

 mean free path, etc. ; they act more like a fog or mist, are mobile and 

 carried about by a current of air to which the}^ give temporary con- 

 ducting powers, clinging to positively electrified bodies and thereby 

 losing mobility and difl'using on the walls of the containing vessel if 

 left (piict. 



Electrons are deviable in a magnetic field. They are shot from 

 radium with a velocity of about one-tenth that of light, but are grad- 

 ually obstructed liy collisions with air atoms, so that some become 

 much slowed, and then are what 1 formerly called loose and erratic 

 particles, which diffuse about in the air and give it temporary con- 

 ducting powers. These can turn corners, can be concentrated by mica 

 cones into a bundle and then produce phosphorescence. 



Another set of emanations from radium are not affected hy an ordi- 

 narily powerful magnetic field and are incapable even of passing 

 through thin material obstructions. These emanations have al>out one 

 thousand times the energ}^ of those radiated ])y the deflectable particles. 

 They render air a conductor and act strongly on a photographic plate. 

 Their mass is enormous in comparison with that of the electrons, 

 and their velocit}^ is probably as great when they leave the radium, 

 but, in consequence of their greater mass, the}^ lire less deflected by 



