130 
WAT ORE 
[DECEMBER 10, 1903 
The experiments of Crookes had shown they were de- 
flected by a magnet, while Perrin much later showed 
that they carried with them a negative charge. If 
the rays consisted of negatively charged particles, they 
should be deviated by their passage through an electric 
field. Hertz had tried such an experiment, but with 
negative results. The remarkable experiments of 
Lenard and the connection in some way between 
Rontgen and kathode rays made the elucidation of 
the true nature of these rays a matter of the first im- 
portance. It was at this stage that J. J. Thomson 
attacked the problem. He showed that the rays were 
deviated by an electric field, and explained the cause 
of the failure of Hertz to detect the same. By two 
distinct methods he proved that the rays consisted of 
negatively charged particles projected with a velocity 
of about one-tenth the velocity of light. The value of 
the glowing carbon filament of an incandescent lamp, 
had the same value of e/m as the corpuscle in the 
vacuum tube. These results indicated that the corpuscle, 
or electron as it is sometimes called, was the protyle or 
fundamental unit of which matter is built up. He 
suggested that the atoms of matter were very com- 
plex systems, consisting of a great number of cor- 
puscles and corresponding positively charged bodies. 
It is remarkable that corpuscles only carry with them 
a negative charge. The positive charge appears 
always to be associated with matter atomic in size. 
This work was followed by a series of investigations 
in the laboratory on that most complicated of all types 
of discharge—the passage of electricity through a 
vacuum tube. Anyone who has witnessed the gradual 
exhaustion of a vacuum tube from atmospheric: 
pressure to the lowest vacuum cannot fail to have been 
Fr eal 
eee 
3 
} s 
4 
Fic. 1.—Prof. J. J. Thomson in the Laboratory. 
e/m, the ratio of the charge on the particle to its | struck with the variety and complexity of the pheno- 
mass, was about 1000 times greater than the value of 
e/m for the hydrogen atom in the electrolysis of water. 
If the charge is the same for both, this shows that the 
mass of the kathode ray particle, or corpuscle as it 
was termed, is only about 1/1000 of the mass of the 
hydrogen atom. The great penetratine power of the 
corpuscles and the law of their absorption in matter 
all supported the idea that the corpuscle was small 
compared with the molecules of matter. The value 
of e/m of the corpuscle was found to be independent 
of the gas in the vacuum tube. 
A series of experiments was then undertaken which 
led to very remarkable results. J. J. Thomson found 
that the negatively charged particles, released by the 
action of ultra-violet light on a zine surface, and from 
No. 1780, VOL. 69] 
mena displayed by the electric discharge through it. 
While much work still remains to be done, it may 
safely be said that the main phenomena are now fairly 
well understood, and can be satisfactorily explained on 
the ionisation theory of gases. 
In addition to this work on the passage of electricity 
through gases, J. J. Thomson has also attacked the 
allied problem of the passage of electricity through 
metals. A theoretical paper on this subject was con- 
tributed by him to the International Scientific Congress 
at Paris in 1900, in which the negatively charged cor- 
puscles in the metal were considered to be the chief 
factors in the transmission of electricity. Two 
possible experimental methods of attack on the ques- 
tion were suggested—the effect of a transverse mag- 
