404 THE POPULAR SCIENCE MONTHLY 



SIMPLE LESSONS FEOM COMMON THINGS 



By Pbofessob FRANCIS E. NIPHER 



WASHINGTON UNIVERSITY 



THEEE has long been a feeling which is still more or less strongly 

 pronounced, that matter is not worthy of very serious attention 

 from mind. Some have had the feeling that matter was the source of 

 all our woes. Although all conscious beings are embodied in masses 

 of matter, it was thought to be a prison-house which served mainly to 

 quench those higher feelings to which we should aspire. The world, 

 the flesh and the devil were all put in one class, and we were advised 

 to have as little as possible to do with any of them. 



In the meantime there have been many who have given their 

 undivided attention to the study of the material things which surround 

 us, and with which we must deal. The chemist and the physicist have 

 undertaken to study the structure and the composition of matter. And 

 the more minutely it has been studied, the more wonderful does it seem 

 when it is considered as a specimen of engineering and architectural 

 construction. We were formerly told that the varied forms of matter 

 which surround us were composed of a comparatively few elementary 

 substances, each of which was composed of particles called atoms; that 

 these atoms were all alike for the same substance, and that they exist 

 everywhere as far as the astronomer can penetrate, into the infinite 

 space which the stellar systems occupy. To give some idea of the size 

 of these atoms as determined by the army of men who in various ways 

 have indirectly measured their dimensions, Lord Kelvin made this 

 illustration. If a rain drop were increased in volume, until its volume 

 equaled that of the earth, the molecules of the substance being propor- 

 tionately enlarged, the water molecules would then be larger than fine 

 shot, and not larger than cricket balls. ■ 



But during the last decade another great step has been taken. A 

 study of radioactive substances has shown that the atom itself is a 

 structure of wonderful complexity. A radioactive substance is one 

 whose atoms explode into their more elementary constituents. There 

 are a number of substances which do this, radium being the most con- 

 spicuous of the group. Each of these substances yields one kind of 

 corpuscle or particle which is common to them all. Each atom is com- 

 posed in part of minute particles having a mass of about one thousandth 

 that of the hydrogen atom. These particles have apparently been iden- 

 tified as negative electricity. They constitute what Franklin called the 



