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Published online by Cambridge University Press: 15 September 2014
In many recent publications Sir J. J. Thomson has suggested a “corpuscular” theory of light; that is, a theory which supposes that the energy of the light is done up into parcels or quanta which retain their energy undiminished as they travel out into space without the unlimited spreading which takes place with ordinary diverging waves. A corpuscular theory of light in this sense has indeed been advocated by Einstein and by many other writers: it is in fact evident that the wave-theory of optics, in its classical form, must be modified in some way in order to be capable of explaining the relations between light and electricity which have been discovered in the last thirty years. Thus, if cathode rays fall on a metallic plate and generate X-rays, which fall on a second metallic plate, electrons are ejected from the second plate whose energy is of the same order as that of the electrons in the primary cathode rays and is independent of the distance of the plates. This seems to indicate that the energy of the X-rays is retained in a compact parcel during the transmission between the plates.
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page 117 note † The credit of having first constructed fields which satisfy exactly the Maxwell-Lorentz equations, and which are propagated without spreading, is due to Professor H. Bateman. The field described in the present paper differs from the types introduced by Bateman in that it does not satisfy the ordinary Maxwell-Lorentz equations, but satisfies the extended form of the equations given here.
page 118 note * The assumption that light-pulses contain electric charge has, however, been advocated, in different forms, by W. H. Bragg in 1908–10, and by Bateman and Leigh Page in more recent years.
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page 120 note § Not necessarily a vortical motion of electrons. In fact, when we speak of “magnetism” as “existing” at a place, we really assume no more than that the magnetic vector is not solenoidal there.
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