BETA- AND GAMMA- RAYS. 109 



tubes, and the beta-rays from radium is one of velocity. 

 The beta-rays fly faster, for they reach the enormous average 

 velocity of more than one hundred thousand miles a second. 

 We have here, not an analogy nor a similarity, but an identity. 

 The beta-rays from radium are corpuscles, for they possess 

 the same properties and in the same degree within the limits 

 of experimental error. What a wonder, then, have we here ; 

 an innocent looking little pinch of white salt not so different 

 in its general properties from ordinary table salt and yet 

 possessed of special properties utterly beyond even the 

 fanciful imaginings of men of past time; for nowhere do we 

 find in the records of thought even the hint of the possibility 

 of things which we now regard as established fact. This 

 pinch of salt projects from its surface bodies possessing the 

 inconceivable velocity of over 100,000 miles a second, a 

 velocity sufficient to carry them, if unimpeded, five times 

 around the earth in a second, and possessing with this ve- 

 locity masses a thousand times smaller than the smallest 

 atom known to science. Furthermore, they are charged with 

 negative electricity; they pass straight through bodies con- 

 sidered opaque with a sublime indifference to the properties 

 of the body, with the exception of its mere density; they 

 cause bodies which they strike to shine out in the dark; they 

 affect a phototgraphic plate ; they render the air a conductor 

 of electricity; they cause clouds in moist air; they cause 

 chemical action and have a peculiar physiological action. 

 Who, to-day, shall predict the ultimate service to humanity 

 of the beta-rays from radium! 



THE GAMMA-RAYS. 



The gamma-rays from radium are still to a certain extent 

 a mystery. Unlike the alpha- and the beta-rays they can- 

 not be bent by a magnet, and their most remarkable prop- 



