238 The N.Z. Journal of Science and Technology. [Jan. 
and he and Sir Joseph Larmor have since been instrumental in carrying 
the consequences of the suggestion a good deal further. 
I have said that it was originally found to be a necessary thing to sup¬ 
pose the existence of the ether in order to account for the phenomena of 
light, and I also remarked that, having had its general properties deter¬ 
mined by the phenomena of light, it was found (by Maxwell) that these 
properties were just the ones which made it suitable also for the explana¬ 
tion of electric and magnetic effects, or what are most generally known as 
electro-magnetic phenomena, and so it was perhaps not surprising that 
when difficulties began to be encountered in optical effects they should also 
not be far under the surface in electro-magnetic effects. And so, indeed, 
it proved to be. Now, Maxwell considered that the ether was fixed rela¬ 
tively to the earth ; or perhaps it would be better to say he did not concern 
himself just then with what might happen if the earth moved through the 
ether. He developed certain laws, which he expressed by equations, which 
are very well known as Maxwell’s equations, and these equations told us 
what happened under specified conditions, and enabled calculations to be 
made. I will be kind enough to spare you from following me through any 
such mathematical gymnastics. They are quite unnecessary in order to 
enable me to get where I want to ; and as, moreover, I should probably 
make mistakes, the consideration is to myself as well as to you. Let us 
leave it at this : he expressed certain relations between such things as 
electrical quantities, and lengths and times, and he found that these rela¬ 
tions were true, and expressed the observed facts of the case. But the fact 
that the earth might be moving through the ether—indeed, it seems that 
it must be—forced the consideration of the possible consequences of such 
a motion upon men’s minds, and Lorentz and Larmor, amongst other less 
brilliant investigators, took up the question. And they found a very 
astonishing thing. They found that, supposing the earth to move through 
the ether with a given velocity (which a mathematician would certainly 
call v), also that if the earth contracted in the way I have explained it 
would have to contract in order to explain the simultaneous back arrival 
of the two rays of light, then the same contraction would also fit Max¬ 
well’s equations. In other words, Maxwell’s equations are true if the earth 
and ether are at rest relatively to one another, and they are also true 
if they are not at rest relatively to each other, provided the contraction of 
lengths such as I have mentioned before takes place; but they are not true 
if the earth moves relatively to the ether, unless it does take place. Well, 
then, let us see where we are now. Maxwell’s equations are true ; they 
are only true if the earth is at rest relatively to the ether, or if it is moving 
and the proper contraction of lengths takes place. If that takes place, 
they are just as true as if the earth and ether were at relative rest. And 
we do find that they are true, so that we are forced to conclude that the 
contraction that we found necessary to account for optical results is also 
thrust upon us by electrical phenomena, and we must reckon with that 
contraction, and see what it means and what it involves. 
It is here that Einstein began to make his influence felt. He said, in 
effect, Let us accept the facts as we find them. Let us recognize that this 
compensating contraction takes place, and see where we are. In the first 
place, the admission of such a contraction amounts to a recognition of the 
conspiracy—if it be a conspiracy—in nature, and in the phenomena of 
nature, to defeat all attempts we may make to ascertain what the actual 
speed of the earth through the ether really is. Any velocity will do. The 
