_a._ A stick of sealing-wax excited A glass tube similarly excited.
by friction with flannel or silk.
A glass tube excited by rubbing
it with fur.
_b._ The zinc disc of an arrangement The copper disc of the same, the
of two zinc and copper discs odometer being held over against
moistened with salt and water, the the surface of the copper disc;
odometer being held opposite to the for again, if it be held to the
middle of the zinc disc; for if it edge of the copper disc, the
be held beyond the disc, half an opposite result follows, and the
inch from and on the exact level rotation is clock-rotation.
of the zinc disc, versed-rotation
is manifested round the whole
circumference.
_c._ A mixture of half a drachm of A mixture of half a drachm of
bicarbonate of soda and five grains tartaric of bicarbonate
acid and five grain of tartaric acid, of soda.
when effervescing upon a plate after
the addition of water.
_d._ The northward pole of a horse-shoe The southward pole of the same.
magnet, or of a magnetic
needle freely suspended.
_e._ One pole of a large crystal, which, The opposite pole.
is to be found out by this
experiment.
_f._ The root of a garden weed freshly The leaves of the same.
taken from the ground.
_g._ The stalk end of an orange, and The opposite points of the same.
of an apple, and of an orange pip.
_h._ The small end of an egg. The large end of the same.
_i._ The tips of the fingers on either The top of the thumb and great
hand, and of the toes of either toe.
foot.
_k._ Right side of the head of a Left side.
sparrow.
The last holds likewise with the greater part of the human body;
but the results of trying the odometer with the human frame are so
complicated, that I shall reserve their consideration for a separate
section.
V. The mechanical solution of these phenomena is simple enough. The
odometer must be under the influence of two constant and unequal
rectilinear forces, operating at right angles to each other on the gold
ring, the effects of which are modified by the centripetal force of its
gravitation. All that is required is, to determine by observation the
place, direction, and limits of the two forces.
It will render the description which follows easier, to suppose that
the pole of the Od-subject which causes clock-rotation be turned
directly from the experimenter; for example, that an egg be placed
longways to the experimenter with its small end from him, or a bar
magnet with its northward pole from him. In the case of a horse-shoe
magnet, both poles are then turned from you. So, too, in the case of
the hand, the fingers and thumbs are both to be turned away.
_a._ Odometer held immediately before, and a quarter of an inch from,
the small end of an egg. _Result_—Distad motion, or motion in the
direction of the long axis of the egg, from the egg.
_b._ Odometer similarly held to the great end. _Result_—Proximad
motion of the odometer—that is, again, motion directly from the axis
of the egg.
_c._ Hold the odometer near either side of the egg, one-fifth of the
distance from either end. _Results_—Transverse sinistrad oscillations.
The same current may be detected above the egg on the same parallels.
The effects described are given in fig. 17. Then here are, at either
end of the egg, two rectilinear currents acting at right angles to each
other. Fig. 18 represents the complementary motions to the above,
which are obtained by touching the odometer finger with the thumb. A
parallel combination of rectilinear motions is produced, but in another
way.
The next three figures exemplify the composition of forces necessary to
produce the rotatory motion of the odometer.
Figs. 19 and 20 are intended to represent the large ends of two eggs,
so placed that the axial currents of the two shall cross at right
angles, at a point equidistant, let us say at half an inch exactly,
from the end of each egg. If the ring be suspended exactly at the point
of meeting of the two forces, it will be driven off in the diagonal,
and continue simply to oscillate in the line A B. But if either of the
eggs is moved back to double its former distance from the point of
intersection of the two forces, the forces will be rendered unequal,
and new results will ensue. The two experiments by which the results
of this arrangement may be tried are represented in figs. 21, 22, and
figs. 23, 24. The longer current is necessarily thereby the weaker of
the two in each combination. Accordingly, rotatory motion supervenes
in each case instead of diagonal oscillation; and the direction of the
rotation is from the stronger towards the weaker current.
Figure 25 represents the various motions which may be elicited by
holding the odometer at the sides or over different parts of a
horse-shoe magnet. The continued lines in all the diagrams represent
the primary motions, the dotted lines their complementary motions.
Figures 26 and 27 represent, in the same way, the primary and secondary
oscillations obtainable over the centre of, or parallel to the needle.
Figures 28 and 29 represent the motions displayed by the odometer,
when it is held above various points in the interval between two
sovereigns, placed upon the table an inch and a half asunder. Compound
effects follow, produced by the joint influence of the two bodies.
* * * * *
VI. I will finally describe the phenomena elicited by the odometer
from the living human frame, including those which are dependent on
difference of sex.
Parties to experiments with the odometer may be in the position either
of Od-subjects, or of reversers of its effects in the hands of others,
or they may be themselves components of the odometer.
I can discover absolutely no difference in the results obtained by the
odometer on men and women, when treated as Od-subjects. The following
results appear to me equally obtainable with persons of both sexes.
With the exception of the arms below the elbows, the wrists and hands,
and of the legs below the knees, the ankles and feet, the two sides
of the person display the polar differences already noticed. If the
odometer be held over the right side of the head, (either front or
back,) over the right side of the face, over the right shoulder or
elbow, or right knee, it exhibits clock-rotation. Held over the same
parts on the left side, it exhibits versed-rotation. On touching the
odometer-finger with the thumb, these effects are of course reversed.
If the odometer be held over the middle and outside of either arm, or
over the middle and back of either fore-arm or hand, it oscillates
longitudinally and towards the hand or foot. On reapplying the
thumb, these longitudinal oscillations are replaced by transverse
oscillations, having a direction _outwards_—_i. e._, away from the
mesial plane of the frame.
The phenomena last described show that the primary idea of a
transverse polarity for the whole frame is still verifiable, even in
the extreme parts of either limb. But below the elbows and knees a
second polarity is superinduced upon the former. Below the elbows and
knees, one side of each limb repeats the phenomena of the right side of
the body, the other those of the left. The odometer held over the tips
of the fingers of either hand exhibits clock-rotation, over the thumb
of either hand versed-rotation; and with these, as I have mentioned,
all the other effects that can be elicited out of the two limbs of
a horse-shoe magnet. The same rotatory movements may likewise be
obtained by holding the odometer near the two edges of the hand, wrist,
fore-arm. The latter singularity, which contrasts with the simpler
effects on the upper arm, must result from the combination of the two
polarities—the systemic and the submembral one.
The odometer, held over the back of the neck or throat, oscillates
transversely. When versed, longitudinally.
It appears to me now that women generally are incapable of eliciting
the movements of the odometer when held by themselves, without touching
a second party.
I have already, in the introductory part of this letter, given a
summary of all the modes I am acquainted with of reversing the motions
of the odometer.
Perhaps I have presumed too much in heading this letter with the title
of “The Solution.” But what is the solution of physical phenomena
but the displaying of the forces which compel their sequence? As an
inquiry progresses, a few general expressions take the place of the
first imperfect and complicated explanation. But the first step made
was still a solution; and the highest solution ever yet obtained has
probably still to be merged in some expression yet more general. So the
attraction of gravitation is probably connected with, or balanced by,
a corresponding repulsive force, coming into operation at some enormous
distance from the centre of each planetary sphere, and the two may
eventually prove to form one law.
But I had hoped that I was not presuming in asserting that the present
inquiry has immediate practical applications, such as seldom fall to
the lot of so young an investigation. The odometer may prove a useful
test of the presence and qualities of electric, chemical, and magnetic
actions; it will probably help to determine the electrochemical
qualities of bodies; and in large or small crystalline masses—in the
diamond, for instance—will serve to show the axes and distinguish the
opposite poles. In reference to biology, it will probably furnish the
long-wanted criterion between death and apparent death; for I observe
that, with an egg long kept, but still alive, though no longer likely
to be very palatable, the odometer freely moves in the way described in
the fourth section. But it treats the freshest egg, when boiled, as if
it were a lump of zinc.
Nevertheless I am not without certain misgivings. I suspect that the
divining-ring will be found to manifest genuine Od-motions in the hands
of as small a number as succeed with the divining-rod. And I fear that
overhasty confidence in results only seemingly sound, may lead many
astray into a wide field of self-deception.