10 LIFE: ITS NATURE AND ORIGIN 



Faith in experiment developed, however, and Leonardo da 

 Vinci, Copernicus and Galileo are among the predecessors of Rob- 

 ert Boyle (1627-1691) who, in his book "The Sceptical Chymist" 

 (1661), espoused the view that unalterable atoms exist, which sur- 

 vive in various chemical combinations. 1 



The Electron 



Sir William Crookes' electric experiments with vacuum tubes, 

 together with the work of Hittorf, Goldstein, Varley, and others, 

 helped develop the concept of radiant energy as a "fourth state 

 of matter." This resulted in the modern concept of the electron, 

 a term suggested in 1891 by Dr. G. Johnstone Stoney for the 

 natural unit of electricity to which he had called attention in 

 1874. 2 



The name electron was later applied to subatomic particles 

 having negative electric charges. Sir J. J. Thomson (Nobel prize, 

 1891) first called them "corpuscles," when in 1897 he proved them 

 to be constituents of cathode rays, so named by Goldstein in 1876. 

 This led to the conception of an electric current as a stream of 

 electrons. 



Professor Robert A. Millikan (Nobel prize, 1917) actually weighed 

 single electrons and showed that they are all of identical mass — that is 

 that they all contain the same quantity of matter. In principle, his 

 method is quite simple. He caught electrons on tiny ultramicroscopic 

 oil droplets, and observed how much faster a droplet would fall in still 

 air when one or more electrons were added to the drop. On some 

 droplets he had as many as 150 electrons, stuck like currents on a bun, 

 and each of them added the same increment of fall. Millikan's "elec- 

 trical balance" could weigh accurately and easily to one ten-billionth 

 of a milligram, whereas the quartz-fiber balance of Ramsay and 

 Spencer, in a vacuum, was 10,000 times less sensitive. The most deli- 

 cate chemical balance of fifty years ago could weigh only about 1/100 

 milligram — for example, your pencilled signature on a card. Accord- 

 ing to Millikan's estimate, the number of electrons contained in the 

 1/100,000 of a cent's worth of electricity passing in one second through 

 a 16-candlepower carbon-filament incandescent lamp is so enormous 

 that if the (then) 2^ million inhabitants of Chicago were to count 

 them at the rate of two per second, and were to keep counting steadily 

 day and night, they would take 20,000 years to finish the count. 



Roentgen and X-rays 



In 1895 Professor Wilhelm Konrad Roentgen (Nobel prize, 

 1901) of Wurtzberg found that when the cathode rays in a Crookes 



