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NOVEMBER 19, 1896] 
NATURE 
67 
concerned in all the different phenomena, and who pointed out 
that the arrangement of iron filings about a magnet was in- 
dicative of the direction of the stresses in the ether. This 
suggestion did not meet the approval of the mathematical 
physicists of his day, for it necessitated the abandonment of the 
conceptions they had worked with, as well as the terminology 
which had been employed, and made it needful to reconstruct 
all their work to make it intelligible. 
It has turned out that Faraday’s mechanical conceptions were 
right. Every one now knows of Maxwell’s work, which was to 
start with Faraday’s conceptions as to magnetic phenomena, and 
follow them out to their logical conclusions, applying them to 
molecules and their reactions upon the ether. Thus he was led 
to conclude that light was an electro-magnetic phenomenon ; 
that is, that the waves which constitute light and waves pro- 
duced by changing magnetism were identical in their nature, 
were in the same medium, travelled with same velocity, were 
capable of refraction, and so on. Now, that all this is a matter 
of common knowledge to-day, it is curious to look back no 
further than ten years. Maxwell’s conclusions were adopted by 
scarcely a physicist in the world. Although it was known that 
inductive action travelled with finite velocity in space, and that 
an electro-magnet would affect the space about it practically 
inversely as the square of the distance, and that such phenomena 
as are involved in telephonic induction between circuits could 
have no other meaning than the one assigned by Maxwell, yet 
nearly all the physicists failed to form the only conception of it 
that was possible, and waited for Hertz to devise apparatus for 
producing interference before they grasped it. It was even then 
so new, to some, that it was proclaimed to be a demonstration 
of the existence of the ether itself, as Well as a method of pro- 
ducing waves short enough to enable one to notice interference 
phenomena. It is obvious that Hertz himself must have had 
the mechanics of wave motion plainly in mind, or he would not 
have planned such experiments. The outcome of it all is, that 
we now have experimental proof, as well as theoretical reason, 
for believing that the ether, once called luminiferous, is concerned 
in all electric and magnetic phenomena, and that waves set up 
in it by electro-magnetic actions are capable of being reflected, 
refracted, polarised, and twisted, the same as ordinary light 
waves can be, and that the same laws are applicable to both. 
Phenomena of the ether are so utterly unlike the phenomena 
of ordinary matter that it is apparent the name matter ought not 
to be applied to this medium. Furthermore, it is also apparent 
that all attempts to describe the properties of the ether in the 
terms applicable to matter will be misleading. Here is a sub- | 
stance which, experimentally, shows itself to be illimitable, 
continuous, homogeneous, isotropic, non-atomic, frictionless, 
incompressible, incapable of transforming its own energy, 
gravitationless, and insensible to all nerves, compared with what is 
limited, discontinuous, heterogeneous, eolotropic, atomic, friction- | 
able, compressible, capable of transforming energy, gravitative, 
and upon which all nerve action depends. Are not these dis- 
tinctions wide enough to make one beware of thinking of them 
and describing their phenomena in the same terms? 
ANTECEDENTS OF ELECTRICAL PHENOMENA. 
When we would give a complete explanation of the pheno- 
mena exhibited by, say, a heated body, we need to inquire as to 
the antecedents of the manifestation, and also its consequents. 
Where and how did it get its heat? Where and how did it lose 
it? When we know every step of those processes, we know all 
there is to learn about them. Let us undertake the same thing 
for some electrical phenomena. 
First, under what circumstances do electrical phenomena 
arise? (1) Mechanical, as when two different kinds of matter 
are subject to friction. (2) Zherma/, as when two substances 
in molecular contact are heated at the junction. (3) AZagueti, 
as when any conductor is in a changing magnetic field. (4) 
Chemical, as when a metal is being dissolved in any solution. 
(5) Phystological, as when a muscle contracts. Each of these 
has several varieties, and changes may be rung on combinations 
of them, as when mechanical and magnetic conditions interact. 
If one confines his attention to the only variable factor in the 
energy in al! these cases, and traces out in each just what 
happens, he will have only motions of one sort or another, at one 
rate or another, and there is nothing mysterious which enters 
into the processes. 
We will turn now to how electricity manifests itself, and what | 
| 
occasionally been stated, but whick, in my judgment, has not 
received the philosophical attention it deserves, namely, that 
electrical phenomena are reversible, that is, any kind of a 
physical process which is capable of producing electricity, 
electricity is itself able to produce. Thus, to name a few: If 
mechanical motion develops electricity, electricity will produce 
mechanical motion ; the movement of a pith ball is a simple 
case. If chemical action can produce it, it will produce chemical 
action, as in the decomposition of water and electro-plating. As 
heat may be its antecedent, so will it produce heat. If magnet- 
ism be an antecedent factor, magnetism may be its product. 
What is called induction may give rise to it in an adjacent 
conductor, and, likewise, induction may be its effect. c 
Suppose we have a series of active machines. An arc lamp, 
radiating light waves, gets its energy from the wire which is 
heated, which in turn gets its energy from the electric current, 
that from a dynamo, the dynamo from a steam engine, that 
froma furnace and the chemical actions going on init. Let 
us call the chemical actions a, the furnace B, the engine c, 
the dynamo p, the electric lamp E, the ether waves Fr. 
Chemical Steam Arc Ether 
er ——urnace,—<—" a Dram o——= sa = = 
energy ae engine Dynamo lamp waves 
A B c dD E F 
The product of the chemical action is molecular motion, called 
heat in the furnace. The product of the heat is mechanical 
motion in the engine. The product of the mechanical motion 
is electricity in the dynamo. The product of the electrical 
current in the lamp is light waves in the ether. Nobody 
hesitates an instant to speak of light waves as forms of motion, 
for they are described as undulations in the ether at right angles 
to the direction of the radiation. No one hesitates for an in- 
stant to speak of the heat as being molecular motion, nor of the 
motions of the engine as being mechanical ; but when we come 
to the product of the dynamo, which we call electricity, behold, 
nearly every one says, not that he does not know what it is, 
but that no one knows! Does any one venture to say he does 
not know what heat is, because he cannot describe in detail 
just what goes on in a heated body as it might be described by 
one who saw with a microscope the movements of the mole- 
cules? Let us go back fora moment to the proposition stated 
early in the address, namely, that if any body of any magnitude 
moves, it is because some other body in motion and in contact 
with it has imparted its motion by mechanical pressure. There- 
fore, the ether waves at F imply continuous motions of some 
sort from A to Fr. That they are all motions of ordinary matter 
from A to E is obvious, because continuous matter is essential 
for the maintenance of the actions. At E the motions are 
handed over to the ether, and they are radiated away as light 
waves. 
ROTATION IN ELECTRICAL CONDUCTORS. 
A puzzling electrical phenomena has been what has been called 
| its duality—states which are spoken of as positive and negative. 
Thus, we speak of the positive plate of a battery and the nega- 
tive pole of a dynamo, and another troublesome condition tc 
idealise has been, how it could oe: na., n an ereccric circuit, 
there could be as much energy at the most remote part as at 
the source. But, if one will take a limp rope, eight or ten feet 
long, tie its ends together, and then begin to twist it at any 
point, he will see the twist move in a right-handed spiral 
on the one hand, and in a left-handed spiral on the 
other, and each may be traced quite round the circuit; so 
there will be as much twist, as much motion, and as much 
energy in one part of the rope as in any other; and if one 
chooses to call the right-handed twist positive, and the left- 
handed twist negative, he will have the mechanical phenomenon 
of energy distribution and the terminology analogous to what 
they are in an electric circuit. So far, there is no trouble ; but 
one can see the rope as a whole twisting, and nothing can be 
seen in an electric conductor. Are not the cases more dissimilar 
than the mechanical analogy would make them seem to be? — 
Are there any phenomena which imply that rotation 1s going 
on in an electrical conductor? There are. An electric arc, 
which is a current in the air, and is, therefore, less constrained 
than it is in a conductor, rotates. Especially marked is this 
when in front of the pole of a magnet ; but the rotation may be 
noticed in an ordinary arc by looking at it with a stroboscopic 
disc, rotated so as to make the light to the eye intermittent at 
the rate of four or five hundred per second. A ray of plane 
it can do. It may be well to point out at the outset what has | polarised light, parallel with a wire conveying a current, has its 
NO. I412, VOL. 55 | 
