Charles F. Brush: Kinetic Theory of Gravitation


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**Charles F. BRUSH**

**Kinetic
Theory of Gravitation**

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**["A Kinetic Theory of Gravitation"; *Nature*
86:130-132, March 23, 1911](#theory)**   
 **[Letter
to the Editor (Sir Oliver Lodge); *Nature*
(March 30, 1911)](#letter)**   
 **["Gravitation";
*Proc. Amer. Philos. Soc*. 68: 55-68 (May 1929)](#gravit)**
  
 **[Bibliography](#biblio)**

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***Nature* 86:
130-132 (March 23, 1911)**

**A Kinetic Theory of
Gravitation**

by **Charles F. Brush**

Ever since
Sir Isaac Newton enunciated the law of universal
gravitation, more than 200 years ago, philosophers have
speculated on the nature of that mysterious agency which
links every atom of mater in the universe with every other
atom. Newton found himself unable to offer any adequate
explanation.

Since
Newtons time several theories of gravitation have been
proposed; but all, of which I am aware, are open to strong
objections, and are not considered even promising by
physicists.

Study of
the nature of gravitation is beset with unusual
difficulties, because gravitation is ever with us and
about us; it is the one universal phenomenon, and we
cannot escape from its influence -- cannot obtain any
outside point of view.

Gravitation
is often described as a feeble force: and so it is, from
one point of view. It is difficult to measure, or even to
detect, attraction between two small bodies. But when the
bodies are pf planetary size the aggregate attraction of
their molecules is enormous. It is easy to calculate that
the attraction between the earth and the moon, which is
just sufficient to retain the latter in its orbit, would,
if replaced by a steel cable, require that the cable be
about 500 miles in diameter in order to withstand the
strain. Between the earth and sun, the cable would have to
be nearly as large in diameter as the earth: and
attraction between the components of double stars is
millions of times greater than between the earth and sun
(Lodge). So tremendous a phenomenon as gravitation, a
phenomenon compared with which all others seem trivial,
must have a mighty origin.

That
gravitation is a phenomenon of the all-pervading aether is
beyond reasonable doubt. This is so generally conceded
that it need not be argued. But how does the gravitative
influence originate? How is it transmitted and maintained?
What is the mechanism of gravitation? It is the purpose of
this paper to attempt an answer to these questions.

Let us
consider what happens to a falling body. We know that it
gathers kinetic energy from some source, as evidenced by
its acceleration; that this energy may do external work or
develop heat; that the amount of energy gathered is
measured directly by the distance fallen through (within
the limits of uniform gravitation), irrespective of the
time or rate of falling. When the distance fallen through
is of inter-planetary magnitude, and the attracting body
large, the gathered energy is enormous, sufficient, if
converted into heat, to vaporize the most refractory
falling body.

We are here
confronted with the question, Whence comes the energy
acquired by a falling body? Certainly it was not inherent
in the body before the fall, as evidenced by the fact that
during unimpeded fall none of the physical or chemical
attributes of the body, aside from the acquired motion,
changes in the slightest degree.

We have
been taught that before the fall the body was endowed with
"potential energy of position" which is converted into
kinetic energy during the fall. I think "energy of
position" is an unfortunate term, because it is so very
inadequate. To me it explains nothing. The case is not
like that of a flexed spring, where there is internal
molecular strain or displacement.

Let us
imagine a pound-weight of iron, for instance, raised from
the surface of the earth to a point near the moon in a
line joining the centers of the two bodies, the point so
chosen that the opposing attraction of the earth and the
moon shall exactly balance each other, leaving orbital
motion out of consideration.

On the
surface of the earth the two-pound weight had some
so-called "potential energy of position", because it was
capable of falling into a pit; but in its new position
near the moon, this potential energy not only has not been
augmented, but has disappeared entirely; the pound-weight,
left free to move, remains stationary; and yet we must
have expended more energy in overcoming the attraction of
the earth and lifting the weight to its new position. This
amount of energy would be sufficient to impart to the
weight a velocity more than 10 times greater than that of
the swiftest cannon-ball, or, if converted into heat,
would be many times more than sufficient to raise the iron
weight to dazzling incandescence and then vaporize it.
Now, in lifting the weight, this large amount of energy
has disappeared utterly. We cannot believe that the whole
or any part of it has been annihilated; it must, in some
form, be resident somewhere. I think no one will contend
that this energy is resident, in any form, in the cold,
motionless pound-weight. I believe it was absorbed by, and
is now resident in, the aether through which it falls.
This is a fundamental idea to which I invite attention.
Faraday glimpsed it long ago, and others have appreciated
it more clearly since his time. But, so far as I am aware,
no one has realized its significance.

This view
of gravitation implies that the aether is endowed with
very great intrinsic energy in some form. Many men of
science now hold that the aether is so endowed, and that
the amount of this intrinsic energy is enormous. Sir
Oliver Lodge ("The Ether of Space") appears to regard this
energy as potential in form, and estimates the intrinsic
energy of a single cubic millimeter of the aether to be
almost inconceivably vast. He says, "All potential energy
exists in the ether". Sir J.J. Thomson says, "All kinetic
energy is kinetic energy of the ether".

I conceive
the aetherial energy involved in gravitation to be kinetic
rather than potential, the latter involving strain or
stress. Newton, and later Maxwell, assumed that bodies
produce a stress in the aether about them of such nature
as to account for gravitation, but they were unable to
imagine any physical cause for the stress.

All the
past theories of gravitation of which I am aware, except
the corpuscular theory of La Sage, appear to regard
gravitating matter as the seat of the gravitative
influence, the surrounding aether, by induced stress or
otherwise, acting simply as the medium of transmission. I
cannot see that any of these theories account for the
energy acquired by a falling body.

My own view
of gravitation differs from these radically. I believe
that kinetic energy of the aether is the fundamental cause
of gravitation, and that a gravitating body plays a
secondary role only in disturbing the normally uniform
distribution of the aethers energy, in manner I shall
endeavor to explain later.

Let us
assume, then, that the aether is endowed with very great
kinetic energy normally uniform in distribution.

Kinetic
energy implies motion of something possessed of inertia.
Now, inertia is a fundamental attribute of the aether. The
aether is highly elastic also, which, with its inertia,
enables it to possess kinetic energy in wave form, as
exemplified in radiation. By the term wave, I mean
progressive motion locally periodic; doubtless the aether
as a whole is stationary. Hence we may consider the
kinetic energy of the aether as consisting in aether waves
of some kind.

These
waves, vast in aggregate energy, eternal in persistence,
without finite source or destination, are imagined as
being propagated in straight lines in every conceivable
direction. The isotropic distribution of kinetic energy,
essential to my theory of gravitation, was, for me, a
difficult conception until I reflected that isotropic
radiant energy is approximately realized in the interior
of any furnace with uniformly heated walls.

Any kind of
waves capable of exerting motive action on the atoms or
molecules of matter will fulfill the requirements; but I
shall first consider the transverse, electromagnetic waves
of radiation, because these are the kind of aether waves
we are familiar with.

Of course,
intrinsic aether waves, if of the radiation kind, cannot
be of any frequency at present known to us as radiation,
because then all bodies would become heated. But we can
easily imagine them of such extremely low frequency that
the molecules or atoms of matter cannot respond to them --
cannot vibrate in unison with them -- molecular resonance
cannot be established; hence no conversion of the aethers
energy directly into heat in the ordinary way can take
place.

We are
familiar with the dissipation or degeneration of the
higher forms of energy into heat, and the continual
degradation of heat to lower degree; that is to say, less
violent molecular vibration and more general distribution.
As is well known, it is only through this degradation or
running down of natural energy that we are enabled to
utilize some of it. Lord Kelvin called this function of
energy "motivity" (we now call it entropy), and said the
motivity of the universe tends to zero.

We know
that ordinary radiation waves in the aether persist
indefinitely and without change of frequency or direction
until they encounter matter, when they are absorbed and
converted into heat, only to be radiated again, usually in
longer waves, to some cooler body. This degradation of
wave frequency continues until we can no longer follow it.
I beg to suggest that the ultimate destination of this
wave energy is that vast reservoir of kinetic energy
intrinsic to the aether. We may liken the waves of radiant
energy, which we apprehend as light and heat, to wind
ripples on the surface of water, which continually
degenerate in wave frequency until they are absorbed into
and become part of a mighty swell of the ocean.

Thus we
may, perhaps, regard the aethers intrinsic energy as
energy in its lowest form -- Kelvins zero of "motivity".
But unfortunately we may, and do, get some of this energy
back in available form in many ways, as, for instance,
when a falling body is arrested and develops heat; some of
our wind ripples are then returned to us.

When two
gigantic astronomical bodies collide under the influence
of gravitation, as sometimes happens, we witness in far
distant space the birth of a nebula. The inconceivably
vast amount of heat developed by the collision converts
both bodies into luminous vapor, which expands with
incredible rapidity into the nebulous cloud. This heat
energy must in course of time degenerate back into the
aether whence it came, though billions of years may be
required; and during all this time the energy has
"motivity". We may picture the stupendous result of the
collision as only a local splash in the aethers mighty
ocean of energy.

Having
postulated that the aether is endowed with very great
intrinsic kinetic energy in wave form of some kind, that
the waves are propagated in straight lines in every
conceivable direction, i.e., the wave energy is isotropic,
and that this energy is distributed uniformly throughout
the universe except in so far as the distribution is
disturbed by the presence of matter, I shall endeavor to
explain my conception of the mechanism of gravitation.

For
illustration in terms of the known, let us imagine a
closed space having uniformly luminous walls of such
character that every point on their surface radiates light
in all internal directions. The enclosed space may be of
any shape, but for the sake of simplicity let it be
spherical or cubical, and large, say as large as a
lecture-room. The space will be filled with isotropic
radiant energy uniformly distributed -- any cubic
centimeter of space containing as much energy as any
other.

Next let us
picture a small opaque body suspended anywhere in our
luminous sphere. The body may be of any shape we may
imagine an atom or molecule to have; but, again for
simplicity, let it be spherical -- say a small grain of
shot, and let it be located near the center of the space.

The small
body will absorb the light which falls upon it, and will
cast a spherical shadow, the depth or intensity of which
will vary inversely with the square of the distance from
the center of the body; and the shadow will extend to the
confines of the enclosure, however large the latter may
be. We cannot perceive the shadow but we know it is there.
It is true that the body will soon acquire the temperature
of its surroundings, and radiate as much energy as it
receives; but for the purpose of this illustration let us
consider only the high-frequency light energy.

As is well
known, the aether waves of light will exert a slight
pressure on the body. But in the case supposed the
pressure will be equal on all sides, and no effort toward
translation can result.

Now let us
introduce a second small body, similar to the first, and
some distance from it. This will also cast a spherical
shadow like the first. The first two shadows will
intersect, and each body will lie within the shadow of the
other. In other words, each body will be partially
shielded by the other from the aether waves coming from
that direction. Hence the light pressure will be less on
that side of each body which faces toward the other than
on the side which is turned away, and the bodies will be
urged toward each other by the excess of light pressure on
the side turned away. This excess of pressure will vary
with the inverse square of the distance between the
centers of the bodies so long as the ratio of distance to
diameters remains large.

The aether
waves concerned in gravitation cannot, however, be like
the light wave I have just used for illustration, because
light waves heat bodies on which they fall; and their
pressure is almost wholly superficial, it does not reach
molecules much below the surface, and hence bears little
relation to mass.

But let us
substitute for the short and feeble waves of light
powerful waves, still of the radiant kind, but of such
great length and slow frequency that, as before explained,
they do not excite the molecular vibrations which we
appreciate as heat, and hence are not absorbed by matter;
they pass freely through all bodies, bathing the interior
molecules as effectively as those on the surface.

Under these
conditions each molecule or atom or unit of a gravitating
body will have its own spherical shadow or field of
influence, and the gravitative force acting on the body
will vary directly with the sum of its units, i.e., with
its mass.

The
spherical shadow which I have pictured as the field of
influence of each atom or material unit implies that the
atom has caused, principally in its immediate
neighborhood, a diminution of the aethers energy. Let us
further imagine this subtracted energy resident in the
atom as kinetic energy of translation in many paths,
almost infinitesimally short and in every direction, but
without collisions, because neighboring atoms follow very
nearly parallel paths. We may then picture the collective
atoms or molecules of matter buffeted in every direction
by the aether waves in which they are entangled, like a
suspended precipitate in turbulent water.

Each atom
or molecule may be regarded as a center of activity due to
its kinetic energy of translation, with continual
absorption and restitution of the aethers energy,
normally equal in amount. The manner in which this
molecular activity maintains, in effect, the supposed
spherical shadow, requires explanation, which I shall
attempt in a future paper.

Of the
several components into which the composite motion of each
atom can be resolved, that one lying in the direction of
an attracting body will be the greatest, because the waves
from that direction, being partially intercepted by the
attracting body, are weakest, and the atom will be pushed
in that direction by the superior waves behind it than it
restores to the weaker waves in front, and will thus
acquire additional kinetic energy of translation in the
line of fall, measured directly by the number of waves
involved, i.e., by the distance moved. Conversely, if the
atom be forced away from the attracting body, restitution
of energy will exceed absorption, and the energy expended
in moving the atom against attraction will be transferred
to the aether.

It will be
seen that gravitation is a push toward the attracting
body, and not a pull. It is clear, also, that the velocity
which a falling body can acquire tends asymptotically to a
limit, which is the velocity of the aether waves which
push it -- the velocity of light, if transverse waves are
involved

I have
already intimated that any kind of aether waves capable of
imparting motion (not internal vibration) to the atoms of
matter will fulfill the requirements of my theory, but
have thus far discussed only transverse waves.

Let us now
consider longitudinal waves -- waves of compression and
rarefaction, like sound waves in air and in elastic
liquids and solids. The "spherical shadow" conception
which I have employed in connection with transverse waves
applies equally well here.

So far as I
am aware, longitudinal waves in the aether are unknown,
but that such waves have not been observed is not
convincing argument that they do not exist.

Assuming,
then, that some, or perhaps much, of the intrinsic energy
of the aether is embodied in longitudinal waves, we have
only to find some motive action of such waves on atoms to
account for gravitation. Adequate motive connection may
perhaps be effected by the locally alternating flow and
ebb -- acceleration and retardation of the aether in which
the atoms are enmeshed, incident to its wave motion. We
have ample reason for believing that does obtain a grip of
some sort on the atoms of an accelerating (falling) body
and a retarding (rising) body, from which it follows that
accelerating and retarding aether, as in a wave of
compression, must grip a comparatively stationary atom.

Certain
facts of astronomy apparently require that gravitational
attraction between bodies, however distant from each
other, must, in effect, be instantaneous; that is to say,
the line of apparent attraction between them is a straight
line adjoining their centers. I believe my theory meets
this condition, but shall reserve discussion of the point
for a future paper.

I feel much
diffidence in presenting the foregoing rough draft of a
theory of gravitation, but I cannot avoid the belief that
it contains some germs of truth, perhaps the real key to
the great mystery, though, if this be true, I have no
doubt used the key clumsily and imperfectly.

If the
aether theory of gravitation is, in the main, the true
one, it offers some hope of experimental verification.
Provided the waves are of one principal frequency, or even
of several, we may find something, doubtless of molecular
magnitude only, which will oscillate in unison with them
so that resonance can occasionally be established and a
cumulative effect be obtained sufficient to manifest
itself as heat.

In
searching for some natural phenomenon of this nature, I
thought of the thermal condition of the upper atmosphere
as a possible case. The mean molecular velocity of a gas
at some temperature, in connection with the mean free path
of its molecules at some particular pressure or pressures,
may possibly afford the necessary conditions for
fortuitous resonance, with development of some slight
amount of heat by the increased violence of
inter-molecular collisions. I have done much experimental
work on these lines during the past year, but,
notwithstanding refinement of method and manipulation, the
results have thus far been unsatisfactory. The work is
till in progress, however, and investigation of other
phenomena is contemplated.

---

***Nature*
(March 30, 1911)**

**Letters to the Editor:
Sir Oliver Lodge**   
**Re:
A Kinetic Theory of Gravitation**

The subject
of Mr. Brushs article in *Nature* of March 23 (p.
129) is certainly of profound interest, and will continue
to be so until the problem as to the nature of gravitation
is solved. Meanwhile, a few questions raised are
comparatively simple. Anyone asked, Where lies the energy
of a raised weight? Must surely reply, "In the aether",
i.e., in the medium, whatever it is, that is driving the
weight down towards the earth. A critic who either doubts
or asserts this will not be confused -- as Mr. Brush
suggests he will be -- by the suggestion that the weight
might be raised up so high as to reach the neutral point
between the earth and moon -- a suggestion which carries
with it the tacit questions, "Where is the energy now?"
and "What has become of the work done?" -- for this case
is no more troublesome than the case of a weight raised
and hung on a hook. Something -- some opposition force --
sustains the weight, i.e., opposes the pull of the earth,
and it matters little whether the opponent be a shelf
beneath it or the moon above it. The important thing to
understand is the nature of the downward propelling force
-- indeed, of both the upward and the downward force -- in
either case.

The
question whether the energy of a raised weight is
potential or kinetic is of little or no importance. The
energy is certainly potential, according to our definition
of potential. So is the energy of a strained spring: for
there also the atoms are separated against their mutual
(cohesive) attraction, and there again the energy really
resides in the aether. But that all energy may turn out to
be ultimately kinetic -- when we come to understand what
elastive stress fundamentally is -- that proposition is
not negatived in the least.

Mr. Brush
proposes a shadow theory of gravitation, a modification of
Le Sagess theory except that the pressure is supposed due
to the non-syntonic impact of waves traveling in all
direction, instead of to a bombardment of utterly minute
particles flying at random. There is nothing new in a
shadow theory, and all such theories are faced with the
difficulty of plausibly explaining the absence of
noticeable screening -- a difficulty which is bound to
reduce them to acquiescence in an approximation.

The
contribution which Mr. Brush makes to the discussion is
the suggestion that the supposed gravitational
aether-waves are the result of accumulated thermal
radiation from all past and present suns, the wave-lengths
having automatically increased during their long storage.

To this
view several objections might be urged -- one of them
being that in that case the constant of gravitation would
be secularly increasing; another, that it should be
greater in a hot enclosure, say the interior of a sun,
than elsewhere; but a more salient objection is raised by
the inquiry as to which is cause and which is effect. How
did the bodies get hot and so radiate? Was not their heat
perhaps due to their having clashed together with
gravitational energy itself derived from the aether?

The fact is
that every question concerning origin involves us always
with insuperable puzzles, and that is just the main
difficulty about gravitation. An atom of matter, by its
very existence, sets up a fixed stress in the aether,
varying directly as the mass and inverse as the distance
-- that is only another way of stating the law of
gravitation; we are trying to understand the nature and
cause of that stress. It appears to be one of the
fundamental properties of matter, and until we can
understand what is meant by the generation or destruction
of an atom -- i.e., of an electron if that is the
fundamental unit -- we are hardly likely to understand its
gravitational influence more than any other of its
fundamental properties -- including, perhaps, existence
itself.

Let this
not be understood as a negative prediction or estimate of
impossibility -- such predictions are always absurd; it
may be that when the structure of an electron is
understood, we shall see that an "even-powered" stress in
the surrounding aether is necessarily involved. What I do
feel instinctively is that this is the direction for
discovery, and what is needed is something internal and
intrinsic, and that all attempts to explain gravitation as
due to the action of some external agency, whether flying
particles or impinging waves, are doomed to failure; for
all these speculations regard the atom as a foreign
substance -- a sort of "grit" in the aether -- driven
hither and thither by forces alien to itself. When, some
day, we understand the real relation between matter and
aether, I venture predict that we shall perceive something
more satisfying than that.

Oliver
Lodge   
University of Birmingham
  
March 25, 1911

---

***Proc.
Amer. Philos. Soc.* 68: 55-68 (May 1929)**

**Gravitation**

by **Charles F. Brush**

At the
Minneapolis meeting of the American Association for the
Advancement of Science in December 1910, I had the honor
to outline "A Kinetic Theory of Gravitation" (Ref. 1).
This was followed by a "Discussion" of the theory in 1914
(Ref. 2) A second "Discussion" came in 1921 (Ref. 3) A
third "Discussion" in appeared in 1926 (Ref 4).

The later
paper contains a concise synopsis of the theory and very
convincing argument supporting my contention of 1910, that
the energy acquired by falling bodies is derived from the
ether.

This
Kinetic Theory of Gravitation postulates that the ether is
endowed with vast intrinsic energy in the form of waves
propagated continually in every conceivable direction, so
that the wave energy is isotropic. The belief expressed is
that all energy is primarily energy of the ether.

The very
high-frequency ether waves, which embody most of the
ethers intrinsic energy, pass freely through matter
without obstruction except that concerned in gravitation,
and a very small heating effect (which will be explained
later). The ether waves exert motive action on atoms or
particles of matte whereby the latter are buffered about
in all directions with some absorption of ethereal energy.
Thus a lump of matter casts a spherical energy shadow into
space, the depth of shadow diminishing with the square of
the distance from its origin. The energy shadows of two or
more bodies interblend, so that energy density between
them is less than elsewhere, and they are pushed toward
each other by the superior wave energy from directions
beyond them. The 1926 paper (Ref. 4) explains this at
length.

To aid in
forming a mental picture of the relation of the very
high-frequency ether waves postulated as the cause of
gravitation, to other well-known classes of ether waves, I
have prepared the chart of ether-wave frequencies shown in
**Figure 1**.

![](brush1.jpg)

Each
horizontal line in the scale of frequencies represents
double the frequency of the line below it, or half the
frequency of the line above it. Thus the scale of
frequency increases upward by octaves as in music.

Starting at
the bottom of the scale with a frequency of one ether wave
per second, the second line four waves per second, the
third line eight waves per second, and so on to the tenth
doubling where we get a frequency of 1,024 waves per
second as shown. Continuing the doubling process another
ten times we get a frequency of 1,024 time 1,024, or 1,024
to the second power, and so on up the scale to the third,
fourth, and fifth, etc., powers of 1,024. Thus it is seen
that the indicated wave frequency increases with great
rapidity as we ascend the scale. At the 20th octave it is
more than a million per second; at the 40th octave more
than a million million waves per second.

I am
indebted to a chart shown a the British Exposition in
1925; to a chart by G.L. Clark in 1927, and to a chart by
W.E. Deming in 1929 for much of the material shown in my
chart. But I have arranged it somewhat differently,
emphasizing ether-wave frequency rather than wavelength.

Frequency
is converted into wavelength by dividing the velocity of
light per second by frequency of the waves per second.
Thus the frequency 1 at the bottom of the chart means one
wave per second, and its wavelength is the distance it
would travel in one second, before another wave started
after it. This is the velocity of light, about 186,000
miles, or about 300,000 kilometers. All ether waves travel
at the same velocity.

A wave
train of this very low frequency and very great wavelength
could easily be launched into the ether by revolving a
closed coil of wire on its own diameter as an axis, in a
magnetic field, at the rate of one revolution per second.
If we should increase its revolutions to ten per second,
we would get a frequency of ten, and a wavelength of
18,600 miles. Such mechanically generated electric ether
waves may be increased in frequency without much
difficulty as far up as shown in the chart.

Next above
we have Hertzian waves, covering about 28 octaves,
generated by the condensor and sparkgap method. The upper
half of of this long range of ether waves contains the
waves used in radio transmissions and music.

Next above
the Hertzian waves, of higher and higher frequency and
shorter and shorter wavelength, we find the infrared and
heat waves covering about 9 octaves. These waves embody
most of the heat received from the sun, and nearly all the
heat radiated from hot bodies below redness.

Then we
cone to the exceedingly interesting and intensively
studied light waves or rays. These cover barely one octave
of the scale, and their mean frequency is about 500
million million waves per second. It seems unfortunate
that the human eye is sensitive to such a short range of
ether vibrations only, while the human ear can perceive
about 11 octaves of sound, or air vibrations. Perhaps some
animals or insects have a wider range of vision than
humans.

Above the
light waves we find about 5 octaves of ultraviolet waves.
The suns radiation includes the last three classes of
waves, though some of the ultraviolet is absorbed by our
atmosphere and does not reach the earth. The ultraviolet
rays or waves promote chemical action and are chiefly
responsible for the ordinary photographic image.

Next in the
growing range of frequency we have the well-known x-rays,
so extensively used in x-ray photography for therapeutic
and industrial purposes. These cover a long range of
octaves in our chart, and overlap the upper part of the
ultraviolet range and the lower part of the gamma range.
X-rays, particularly those of the highest frequencies,
pass rather freely through large thicknesses of light
substances such as wood, fabric, animal tissue and metals
of low atomic weight and density; but metals of large
density and high atomic weight absorb and obstruct them
greatly. Thus a quarter inch of lead almost completely
stops x-rays of the highest frequency. The ability of
x-rays to pass deeply into or through matter, is called
"penetrating power".

Above the
x-rays in our chart are the gamma rays of radium, so
extensively used in therapy. These have a much greater
penetrating power than the highest-frequency x-rays.

All the
above described classes of ether waves have been
demonstrated experimentally, and doubtless all exist to
some extent, permanently in the ether of space.
Particularly is this true of the heat waves, as I pointed
out in my 1927 paper (*Proc. Am. Phil. Soc*. LXVI,
1927). In that paper I showed, conclusively I think, that
a lump of matter far out in inter-stellar space could not
possibly fall to absolute zero by temperature radiation of
all its heat, as commonly supposed, but would soon acquire
and then maintain the "temperature of space" which I
estimated to be something like 50\* to 100\* above absolute
zero.

Above the
gamma rays there are about 6 octaves which have not been
explored experimentally. Then we come to the cosmic rays,
so ably demonstrated and studied by Dr. Millikan. These
cover considerably less than one octave, and their mean
frequency is about 5,000 million million million waves per
second. This is 10 million times greater frequency than
light waves possess; and yet there can be no doubt that
cosmic rays are ether waves like all the rest. As might be
expected, cosmic waves, on account of their very much
higher frequency (shorter wave length), have far greater
penetrating power than the highest-frequency x-rays; in
fact, about 300 times greater, as they pass through 6 feet
of lead.

Starting
considerably above cosmic rays in the chart, I have drawn
a long bracket with indeterminate ends. Somewhere in this
region lie the isotropic ether waves of gravitation,
probably having considerable range of frequency. The
enormous frequency of these waves enables them to pass
freely through all kinds of matter without obstruction
except that concerned in gravitation.

Probably
most of the vast intrinsic energy of the ether lies in the
region of the gravitation waves.

Until about
a year and a half ago, we had no experimental evidence of
the gravitation waves other than gravitation itself. But
gravitation is a most impressive demonstration of the
ether waves which cause it, and of the very great energy
embodied in them. As illustrating both pints, I call
attention to Lord Kelvins graphic word-picture of
collision of two large astronomical bodies under the
influence of their mutual gravitational attraction, which
I have quoted in my 1914 paper ((Ref. 2) and my 1926 paper
(Ref. 4) As another illustration of the enormous
differential ether-wave push of astronomical bodies toward
each other, let us consider the case of the earth and
moon. The urge toward each other is commonly called
gravitational attraction, which is only another way of
looking at it. If this attraction were absent, and the
moon were held in her orbit by a weightless steel cable,
the cable would need to be about 500 miles in diameter to
stand the strain. Between the earth and sun, the cable
must be about 6,000 miles in diameter. And the attraction
(push toward each other) of the components of some double
stars must be thousands of times greater than this.

Obviously,
the ether waves of gravitation, and the other classes of
waves we have discussed, must be permanent attributes of
the ether; they cannot escape from either boundless or
bounded space. They must fill all space; and we may
therefore regard gravitation as a property of space,
because wherever there are two or more particles or bodies
of mater, however small or large, however near or distant,
they are urged toward each other by the ever-present
isotropic ether waves of gravitation.

Very high
up in the chart I have tentatively drawn the line marked
"Quanta waves or rays", indicating a frequency of 6.54 x
1027.

**Experimental
Evidence of the Ether Waves of Gravitation:**

A year ago
I had the honor of presenting a paper under the title
"Correlation of Continual Generation of Heat in Some
Substances, & Impairment of Their Gravitational
Acceleration" (*Proc. Am. Phil. Soc*. LXVI, No. 2,
1928).

This
division of papers is a continuation of last years paper;
and to save the reader the bother of looking up that paper
and its several references, I shall quote very freely from
it and prior papers.

The third
"Discussion" (1926; Ref. 4) contains in its title "Some
Experimental Evidence Supporting Theory; Continual
Generation of Heat in Some Igneous Rocks & Minerals".

"Heat is
often defined as an agitation of atoms and molecules of
matter, and measured by the total kinetic energy of such
agitation. The agitation consists partly in internal
vibrations of the elastic atoms and molecules and spinning
about their various axes, and partly in very rapid
transitory motion among themselves. Thus they are supposed
to dart about in every conceivable direction, constantly
colliding with each other and rebounding or glancing in
new directions. The kinetic energy of this translatory
motion constitutes sensible heat (not total heat) and is
the measure of temperature. Anything (such as absorbed
radiation) which stimulates the internal vibration of
atoms or molecules likewise increases their translatory
velocities by the increased violence of rebound after
collision, and thus increases their temperature; and vice
versa.

"All the
above is known to be true of gases and vapors (kinetic
theory of gases) and is generally believed to be true of
liquids and solids.

"The mean
free path and the mean velocity between collisions of
the molecules of many gases under stated conditions have
been computed. But it has also been shown mathematically
that the higher and lower velocities, and the longer and
shorter paths, differ greatly from the means, and may in
each respect vary 20 or more times in amount. Doubtles
this is true also of liquids and solids.

"From the
fortuitously wide variation I velocities and free paths of
the billions of vibrating atoms or molecules in their
heterogenous movement, it follows that collision
frequencies must also vary greatly, but have a wide range
of frequencies as do the well-known x-rays.

"With the
foregoing in mind it is easily conceivable that some kinds
of matter may have atoms or simple molecules or complex
molecules of occasional vibration frequency corresponding
with some gravitation wave frequency, whereby fortuitous
resonance can, for brief instants, be established at
various points. This would result in a slight increase of
vibrational activity and a cumulative rise of general
temperature.

"A body of
such matter, with some thermal insulation, would become
and remain permanently warmer than a neighboring body
similarly circumstanced, but not endowed, or less endowed
with the permissive heat-generating quality".

A carefully
designed calorimeter is illustrated and described in the
paper (1926), and details of many experiments given. These
resulted in the discovery that some rocks and minerals did
generate an easily observable amount of heat.

In April
1927, I presented another paper on "Persistent Generation
of Heat in Some Rocks & Minerals" (*Proc. Am. Phil.
Soc.* LXVI). This is a continuation of the 1926
paper. It describes a new and different calorimeter, built
in the spring of 1926, and since known as the "Ice
Calorimeter". It has been in almost continuous use down to
the present time (April 1928) and has proved very
satisfactory. With this calorimeter it has been found that
some of the natural heat-generating materials, and some of
the artificial silicates hereafter described, have
retained their heat-generating activity unimpaired; and
none of these substances is more than minutely
radioactive. Quoting from the 1927 paper:

"It is
notable that all the materials which appear to be endowed
with persistent heat generating activity are complex
silicates".

There
follows a description of the preparation, in the wet way,
of many complex silicates, and their preliminary testing
for heat generation. A silicate of the protoxide of nickel
and cobalt showed very large activity, larger than either
silicate alone: and this now appears to be permanent.
Nickel and cobalt are almost identical in atomic weight,
and differ but one unit in atomic number. Quoting again
from the 1927 paper:

"In the
absence, at present, of other explanation, it is thought
that persistent heat generation in some rocks and minerals
is due to isotropic ether waves of great penetration; very
great indeed, if the generation goes on in the interior of
the sun and planets as it does at the surface of the
earth". Quoting now from the 1928 paper (Ref. 6):

"It is now
believed that the class of isotropic ether waves
postulated as the cause of persistent generation of heat
in some substances, is the same class, perhaps of very
wide range of frequency, postulated as the cause of
gravitation.

"Conversion
into heat of some of the energy of the gravitation ether
waves, however little, might be expected to impair to some
extent the falling velocity of a heat generating
substance; and all such substances thus far tested have
clearly shown impairment.

"I have yet
found no exception to this remarkable phenomenon, though I
have already tested many natural and artificial minerals.
Substances which have shown no generation of heat in the
calorimeter show no impairment of their falling velocity
when compared with lead. Substances exhibiting small,
moderate or large generation of heat have shown
comparatively small, moderate or large impairment of the
gravitational acceleration.

"In making
the above indicated comparisons of falling velocities I
have largely used the method and apparatus described and
illustrated in my 1923 paper on "Some New Experiments in
Gravitation" (*Proc. Am. Phil. Soc.* LXII, No. 3; See
also the 1924 paper of the same title: *Proc. Am. Phil.
Soc*. LXIII, No. 1)

"Two
aluminum containers are used, alike in size, shape, weight
and smoothness of surface, and dropped simultaneously,
side by side, through exactly the same distance (about 122
cm).

"Each
container, at he end of its journey, breaks an electric
circuit. But the breaks of both containers are in series
in the same circuit, so that the break which occurs first
produces a bright spark while the belated break gives no
spark because its circuit is already open

"When the
containers are equally loaded with the same metal, there
is no visible spark at either break, or a very feeble
spark at one or the other indifferently. But when they are
equally loaded with certain different metals, one
container persistently produces a bright spark, though
containers are always reversed in position for each trial.
From this it seems clear that the container giving the
spark falls a little faster than the other. This sparking
condition is clearly manifested when the faster container
reaches the end of its free path as little as 0.0125 mm.
((0.0005 inch) in advance of its neighbor.

"The 1923
paper also describes how approximate quantitative
measurements are made. These are very tedious, especially
when falling velocity differences are large.

"To
facilitate estimation of the larger falling velocity
differences I am perfecting a photographic method of
observation. After falling about 110 cm the small lower
ends of the containers are photographed in silhouette
against a white background having many horizontal lines,
and illuminated by a very bright electric spark".

Then
follows several pages of text, with figures and pates,
describing the apparatus admits operation, too lengthy to
quote here. Resuming quotation from last years paper
(1928):

"The camera
lens is located about 37 cm in front of the white surface,
and the photographic plate about an equal distance behind
the lens; so that the image is about equal in size to
parts photographed.

"The plate
holder moves vertically in guides, and rests on a pin in
one of eight equally spaced holes 1.6 cm apart in the
backboard of the camera. This backboard has a horizontal
opening 1.4 cm wide, which limits the exposed portion of
the plate to a strip of this width. Thus eight pictures of
the falling container tips are made on one plate. The
containers are reversed in right and left position after
each exposure.

"Plate III
shows a series of photographs. Each container weighted
approximately 30.6 grams. One was marked with a white spot
on its top for identification. This one, lettered S on the
plate, was filled with silicate of nickel and cobalt,
which weighed 13.6 grams, or about 30.8 % of the total
weight of the loaded container. The unmarked container was
loaded with lead sawdust, held tightly in the lower end by
a short closely fitting cork above it, until it very
closely equaled the marked container in weight.

"Each of
the eight photographs on the plate, when magnified,
clearly shows the S container (Silicate) slower than its
companion. Six more similar plates have been made with the
same loaded containers, and all show the same effect. It
will be noticed that the amount of retardation of the S
container varies considerably in the eight exposures of
Plate III. This was principally due to small lateral air
currents in the room which acted unequally on the two
containers when one shielded the other; as was
demonstrated with another plate by purposefully increasing
the lateral air currents. I shall eliminate lateral air
currents in future work.

"Of course
I tried exchange of loads in the containers, but without
observably affecting the result; the container holding the
silicate was always slow.

"The
observed retardation o the silicate container must be due
to impaired gravitational acceleration of the silicate as
compared with the lead sawdust in the other container; and
as the silicate constitutes only 30.8% of the total mass
undergoing acceleration, we must multiply the observed
retardation by 3.25 to find the full impairment of the
silicate alone.

"In the
apparatus as set up, the centers of the container tips are
about 1.6 cm in front of the lined background; hence tips
and lines cannot both be sharply in focus of the camera
lens. In Plate III the focal plane of the camera was about
half way between the tips and the lines. Sharpness of
lowest part of the curve of the tips was greatly enhanced
by permanently covering all of the camera lens except a
horizontal strip 2 mm wide across its center.

"The
comparison lines in Plate III are spaced one mm apart
between centers. I am installing another white background
with very much finer lines spaced only half a mm apart,
and far better adapted to micrometer measurement of
container tip differences of level.

"The Bureau
of Standards, with a calorimeter of its own design, is
working with some of the heat-generating substances for
the purpose of checking my findings."

Since
writing the 1928 paper I have continued work on the
fascinating subject of "Correlation of continual
generation of heat in some substances and impairment of
their gravitational acceleration". These phenomena appear
to be related as cause and effect. I have gathered
considerable new evidence, all affirmative, so that I now
feel justified in dismissing doubt.

In the
quest for more evidence, however, I have reversed the
order of procedure; i.e., instead of hunting more or less
at random, for new substances exhibiting generation of
heat in the calorimeters, which is a very slow and tedious
process, I have first tested many new substances for
impaired gravitational acceleration, which is
comparatively rapid and easy. In these tests I have made
more than 50 new plates, and feel well rewarded for the
labor.

In my
former experiments it had appeared that silicates of the
iron group of metals exhibited much greater impairment of
acceleration than silicates and compounds of the metals of
lower atomic weight. So I chose silicates and other
compounds of metals of still higher atomic weight, viz.,
Barium, Lead and Bismuth as most promising materials to
work with.

In all the
artificial silicates there was some sodium silicate. Lead
silicate gave a moderate effect, but after ignition none.
Bismuth silicate behaved in the same way. Lead acetate
gave a moderate effect.

The barium
compounds were found very interesting, and were more fully
investigated. Barium hydroxide, Ba(OH)2, 8H2O
gave rather large effect, but required lining of the
container on account of its powerful corrosive action on
metallic aluminum. BaO (anhydrous; effect moderate. BaO,
8H2O, effect small but certain. BaCl2,
2H2O, effect small. BaBr2, 2H2O,
effect very small if any. BaSO4; effect very
moderate. Ba3(PO4)2;
effect small. Ba(SCN)2, 2H2O; effect very small
if any.

The Barium
Aluminates were the most interesting of all the compounds
examined. Three grades were prepared: (BaO)2Al2O3,
BaO, Al2O3 and BaO(Al2O3)2.
All, after air drying to constant weight, lost several %
of hydroscopic moisture when dried at 100o C.
and several more % of combined water when gently ignited.
After ignition they were but very slightly hygroscopic.
The BaO, Al2O3, dried at 100o
C., gave largest effect; but after ignition the effect was
somewhat reduced.

**Plate I**
shows the impairment of gravitational acceleration in the
BaO, Al2O3, not ignited, as compare
with lead in the usual way. The upper two of the usual
eight photographic strips are omitted, in order to permit
enlargement of the remaining six strips about 50%. The
black lines on the white background against which the
lower tips of the two falling containers are photographed,
are spaced exactly half a millimeter apart between
centers, and are as fine as it was found practicable to
make them. As before explained, neither the lines nor the
tips of the rapidly falling containers are sharply in
focus of the camera lens. The tip of the container holding
the Barium Aluminate is marked S (slow) on the plate; and
the containers were reversed in position after each
dropping as indicated. As easily seen on the plate, the S
container is unevenly slow in the six photographs, and
even very slightly fast in the first. This unevenness is
attributable to variation in the exceedingly slight
friction of the containers in their guiding tubes during
the first millimeter of their fall. The containers are
perfectly free after that.

**S**![](brush2c.gif)

For
accurate measurement of falling velocity differences of
the containers in all plates, I have used a binocular
microscope of low magnifying power, having a very large
stage provided with a high-precision micrometer specially
designed and built for this purpose.

In finding
the average impairment of gravitational acceleration of
the S container in the six photographs of Plate I, all
were measured with the micrometer, the five affirmative
values were added together, the slight negative value o
the first one subtracted from the sum, and the remainder
divided by six. This gave the mean slowness of the S
container -- 0.099 mm, say one tenth of a millimeter. This
is one part in 11,000 of the distance fallen (110 cm). But
the Barium Aluminate constituted only 40.3 % of the total
weight of the loaded container. Hence, impairment of
falling velocity of the barium Aluminate alone, as
compared with equal weight of lead in the other container,
was one part in 4450. When a companion plate was made with
the container loads exchanged (as customary in all tests),
slowness of the Barium Aluminate was found closely the
same.

Of the
several compounds described and tested for impairment of
falling velocity, only two have been tested in the ice
calorimeter for continual generation of heat. Barium
Sulphate, the first of these, was chosen because of its
undoubted stability, although it had shown but very
moderate impairment of falling velocity. It exhibited very
moderate but steady and satisfactory generation of heat
during a long run in the calorimeter. The second
calorimeter test was made with barium Aluminate like that
used for Plate I; but after preparation it was only air
dried at room temperature, to avoid any unstability that
might arise from hot air-drying, or ignition. The specimen
was prepared about two months ago, and has been in the
calorimeter during the last six weeks, where it continues
to show rather large and steady generation of heat. It
appears to be quite stable.

More than a
year ago the Bureau of Standards very kindly offered to
repeat some of my experiments on "continued generation of
heat in some substances". A special ice calorimeter, quite
different from mine, was designed and built for the
purpose. After much time spent in perfecting and
calibrating the calorimeter, a specimen of the air-dried
Sandusky clay describe din some of my earlier papers, was
tested during the last few months; and I have very
recently received official announcement that this
substance does continually generate a measurable amount of
heat. The Bureau is about to commence testing the
comparatively active Nickel-Cobalt Silicate described in
my last two papers.

Correlation
of continual generation of heat in some substances and
impairment of their gravitational acceleration, is
regarded as  very strong evidence in support of the
kinetic theory of gravitation; and we seem now well on the
way of finding out something definite about the nature of
gravitation, which has been by far the greatest of all
outstanding physical problems.

---

**Bibliography**

*Dictionary
of American Biography*, Suppl. 1,2; p. 29

*Science*(March 10, 1911)

*Nature*
86 (2160): 130-132 (March 23, 1911); *ibid.*, 
86 (2161) (March 30, 1911); Letter, Sir Oliver Lodge

*Proc.
Royal Soc.* (Series A) 93 (1917); *ibid.*, 95
(with Sir Robert A. Hadfield & S.A> Main)

*Proc.
Amer. Philos. Soc.* 50 (3), 1926; *ibid.*, 53
(213), Jan.-May, 1914; *ibid*., 54 (May-July, 1921;
*ibid*., 60 (2): 43-61 (1921); *ibid.*, 62 (3):
75-89 (Sept. 29, 1923); *ibid*., 63 (1): 57-61
(1924); *ibid.*, 66 (3): 251-166 (1927); *ibid*.,
67 (2): 105-117 (1928); *ibid*., 68: 55-68 (May
1929)

*Amer. J.
Sci.* 88: 118-128 (Jan.-May 1914)

*J.
Franklin Inst.* 206 (1232): 143-150 (Aug. 1928)

*Phys.
Rev.* 9 (2), 1917

US Patents:
  
 #337,299 (Battery)
  
#1,698,669 (Jan. 8,
1929), Piezo-electric crystals   
# 1,823,864 (Sept., 1915)

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