462 Sir Oliver J. Lodge [Feb. 28, 



explained in terms of the magnetic field which necessarily surrounds 

 and accompanies every charge in motion ; since a charge in motion 

 constitutes a current. For on this view a material l)odv is but an 

 aggregate of such charges grouped according to some definite pattern, 

 positive and negative charges interlaced or somehow intertwined, and 

 so far apart in proportion to their size that they do not interfere 

 with each other or cancel each other, nor apparently overlap or 

 encroach on each other's field, to any measurable extent. Is this 

 possible ? It is. For comparing the size of an electron with the 

 size of an atom we perceive that they are relatively of the same order 

 as the size of a planet and the size of a solar system. So it becomes 

 possible to think of an atom as a sort of solar system, with a positive 

 nucleus or sun surrounded by negative electrons revolving in regular 

 orbits round it. 



On this view, or indeed in any form of the electrical theory of 

 matter, the atom of matter consists mainly of empty space ; in other 

 words, it is excessively porous ; just as the solar system is mainly 

 empty space and may be spoken of as excessively porous ; the actual 

 material lumps being almost infinitesimal in proportion to the total 

 bulk. A rapid projectile or a ray of light passing through the solar 

 system would be unlikely to hit anything, the chances would be 

 strongly against a collision. So also, if a point be thrown through 

 an atom, the chance of its hitting anything is about 1 in 10,000. It 

 might pass through 10,000 atoms before striking. This experiment 

 has been tried, by C. T. R. Wilson and others, and that is roughly 

 speaking the result. Sooner or later a radium projectile meets with 

 an obstacle and is stopped, but it traverses a good number of atoms 

 on the average ; it traverses quite a perceptible distance even in a 

 dense solid, before it strikes a nucleus. 



Matter accordingly seems to me — to us I may say, for in this 

 most physicists are I think agreed — a gossamer or milky-way 

 structure^ an impalpable accident in the substantial ether. Here a 

 speck and there a speck, but, for the great bulk of it, empty space ! 



" Impalpable " is not the right word, for matter is essentially 

 palpable. It is because it appeals so directly to our senses that we 

 attend to it so vividly. It forces itself on our attention, while the 

 ether eludes us. And why ? Clearly because our bodies are composed 

 — our sense organs are composed — of this very matter. On the 

 material side we are part of, and thoroughly at home in, the material 

 universe. Whereas the ether is elusive ; we know nothing of it 

 directly : and though our eyes are instruments for receiving etherial 

 tremors excited by agiuited electrons, we only know that fact — or half 

 know it — by rather recondite inference. Light really tells us nothing 

 about its own nature, but only about the superficial aspect of that 

 gross and palpable matter which has interfered with and scattered it 

 before it enters our eye. 



Nevertheless the atoms of this solid-seeming fiesh and matter as 



