236 SCIENCE AND THE HUMAN MIND 



their straight path, Thomson was able to calculate 

 their velocity and their mass. The velocity proves 

 to range round a value of about 18,000 miles a second, 

 or one-tenth that of light, while the mass of each of 

 them is about the eight-hundredth part of the mass 

 of the lightest chemical atom known the atom of 

 hydrogen. These " corpuscles " seem to be identical 

 from whatever source they come, and whatever be 

 the conditions of the experiment. They form a 

 constituent part of all chemical elements, while the 

 charge of electricity they carry seems to be the true 

 natural unit of negative charge. They approach, 

 at all events, the old conception of a common basis 

 for matter formulated by Greek thinkers two thousand 

 five hundred years ago. 



But, at this point, the ideas we have been following 

 come in contact with those suggested by another 

 and independent enquiry, set on foot by the mathe- 

 maticians Lorentz and Larmor. Maxwell's work had 

 shown long ago that light was to be regarded as a 

 series of electromagnetic waves. It followed that the 

 waves must be started by the oscillations of minute 

 electric charges, and that every substance capable 

 of emitting light when raised to incandescence must 

 contain electric charges ready to be set in oscillation. 

 But moving electric charges carry electromagnetic 

 energy and momentum with them in the surrounding 

 space, and thus themselves possess inertia or mass. 

 Now these two properties are sufficient to endow 

 matter with its known characteristics, and thus 

 matter itself may be explained as an electrical pheno- 

 menon, while the ultimate electric charges or " elec- 

 trons " may be identified with the corpuscles of the 



