BRADLEY'S estimate of the velocity of light, founded upon his study of "the aberration of light," is even less worthy of consideration.

Any effort to measure such an inconceivable velocity as that claimed for light, by any means or appliances which may be devised by human ingenuity, must be regarded as futile. DESCARTES says: "Light reaches us _instantaneously_ from the sun, and would do so, even if the intervening distance were greater than that between the earth and heaven."

FOOTNOTES:

[5] Appendix, p. 99.

[B] This term is employed as being most exact and comprehensive, as this fluid is now known to be the source of all life and all attractions.

CHAPTER V.

SUN-HEAT.

_Its Source and Limits._

Sun-heat is another product of the same retro-action between the sun and earth; consequently it has the same range and the same boundaries as when it is viewed as light.

_Tendencies to unsettle in Science._

The scientists of to-day may well look after the soundness of their favorite theories of the great physical forces; for the uncertain tenure of old theories, by reason of recent discoveries, is becoming but too manifest. New phenomena are now observed which require solutions not met by present hypotheses. The nebular hypothesis which has so long possessed the scientific mind has, by the discovery of the moons of Mars, become a thing of the past. According to M. MAICHE, water is found to be no longer the old-fashioned conventional oxygen and hydrogen, but essentially a new element must be considered in estimating its composition.[6] Light is ascertained to be as veritable a substance as water. The sun is recognized to be dark, cool, and habitable. Messages go through the air from kite to kite ten miles apart without visible agency. Telephonic sounds leap from wire to wire through quite ten feet of s.p.a.ce.

_Present theories of Supply of Sun-heat._

The present theories of the production and dissemination of sun-heat, are simply accepted for want of better, and not because they account satisfactorily for the phenomena.

The first and most prominent is the combustion theory, which, though bearing the seal of ages, is obnoxious both to common and philosophic reasoning. This theory presupposes a consumption of material beyond all conception, and the supply of which has been no small tax upon the scientific imagination. The source of this supply has been claimed to be the subsidence of useless worlds, and of asteroids, and meteors, showered down upon its surface. Estimates have been carefully made, and we are gravely informed of the probable amount of combustive material required to supply the sun's demands for given periods. It is said that the coal-fields of Pennsylvania, which would supply the world's consumption for centuries, would keep the sun's rate of emission for considerably less than 1/1,000 part of a second. POUILLET estimated the quant.i.ty of heat emitted by the sun per hour to be equal to the supply of a layer of anthracite coal ten feet thick, spread over the whole surface of the sun.

The theory advocated by HELMHOLTZ, and by many other scientists, of "the gradual contraction of the solar orb," and that of SECCHI, "the dissociation of compound bodies in the sun's substance," are attempts after a more consistent philosophy.

The foregoing theories pre-suppose the sun to be a glowing fiery ma.s.s, from which, in all directions, issue radiations of heat and light into s.p.a.ce. Of this enormous quant.i.ty of radiated heat, the earth is supposed to receive but 1/2,000,000,000 part.

MEYER observes: "_A general law of nature which knows no exception_ is the following: _In order to obtain heat, something must be expended._"

This combustion theory therefore calls for an enormous expenditure of material for generating heat and light, together with a still further expenditure of force for projecting these into all s.p.a.ce, at all distances. All these theories are therefore inconsistent with the immutable law of the Conservation of Force.

_The true Source of Supply._

In seeking the source of supply of heat and light, we are compelled to look for a philosophy more consistent than any hitherto advanced.

Controlled too much by the literal evidence of the senses and the superficial appearance of things, we have ever regarded the sun as ALL ALONE in developing and exercising these great forces.

The law of conservation compels us to look to the _earth_, a heretofore neglected factor in this problem. This factor being introduced we shall find the problem to be wonderfully simplified.

All s.p.a.ce may rationally be regarded as complete vacuum, thus presenting no resistance nor obstacles to the free progress of the retro-acting elements. Distance is then virtually annihilated, and Mercury, 37,000,000 of miles from the sun, and Neptune, 2,800,000,000 of miles, stand alike in their relations with the great central orb.

_The Earth's part in the Process._

The earth may no longer be regarded as having a merely pa.s.sive part to play. The forces in operation as between the earth and sun, are purely co-operative, and the one precisely counterbalances the other. The earth, therefore, must have a _vis viva_ within itself, capable of reciprocating in the organic functions of the great vito-magnetic circuit. We certainly know that it possesses a marvellous wealth of resources. The following are the most important of its sources of _vis viva_.

1st. The great reservoir of vito-magnetic fluid, the vast incandescent earth-core. The presence and activity therein of mighty force,--of heat, and motion, in the highest degree, are abundantly shown by various terrestrial phenomena. These phenomena, while perfectly familiar to observers, seem never to have received any fitting interpretation.

2d. Motions and frictions of every kind;[C] the motions of the waters of the earth, the great oceans, with their rolling tides sweeping the whole circ.u.mference of the earth twice in twenty-four hours, at a speed of one thousand miles per hour; with its frictions upon itself, the bottom, and the sh.o.r.es; its great storms lashing it into fury, and its gentler motions from lesser winds; also the motions of all seas, rivers, and rain-falls.

3d. So all motions of the air, in form of hurricanes, lesser winds, or zephyrs; tearing their way through forests, and hills, and through s.p.a.ce; or causing gentlest flutter of leaflet. We have witnessed their goings forth, but have neglected to calculate their mission.

4th. All chemical actions.

5th. All combustions.

6th. All evaporations.

The _earth_ is thus elaborating in all her gigantic processes, the materials and forces, which _she_ furnishes in the great interchange.

How strangely have these great sources of _vis viva_ remained practically unheeded until the present time.

_The Sun's part in the Process._

The part performed by the sun may but feebly be conceived.[7] Within its vast proportions (being 1,000 times as large as all the planets combined) may be found every element suited to all requirements.

_We seek a new Philosophy._

The construction of a true philosophy of the physical forces must depend now upon our rightly understanding the _modus operandi_ of the conveyance, and utilization, of these sun-elements, and the workings of this sun-power.

The presence of a veritable flood of light, heat, and magnetic force, as in motion from the sun to the earth, has ever been recognized. _The line of greatest intensity of this solar, or vito-magnetic current, is found along the line of greatest diameters of those bodies._ The centre of this current reaches the earth at, or near the equator.

It is a well-established fact that from the equator to the poles a continuous magnetic flood is ever in motion.[8]

In thus tracing the course of the magnetic current from the sun to the equator, and thence to the poles, a physical necessity, made imperative by the inexorable law of conservation, indicates that a _retro_-current from the earth back to the sun, must now have part in the process.

Should such be the case, as all reason and philosophy affirm, we have a completed _"Grand Magnetic Circuit," in and through which all physical phenomena have their origin_. But aside from the logical necessity, we hold that there are terrestrial phenomena, which, rightly interpreted, point to just such a retro-acting inter-communication.

_Old Phenomena, and new Interpretations._

The phenomenon, the aurora borealis, or polaris, has never been satisfactorily explained. It is acknowledged as purely magnetic in character, and to be due to the pa.s.sage of currents upward from the earth. It has received the regard due to a mere negative though brilliant exhibition, whereas the character, extent, and significance of its manifestations should have caused it to be greeted, and studied, as the index of the operation of very positive cosmical functions.

HUMBOLDT regarded this process as "the restoration of a disturbed equilibrium;" and so indeed it is, but it is an equilibrium, not simply as between the earth, and atmosphere. Various observers have estimated the alt.i.tude to which the aurora sometimes reaches, at from 80 to 265 miles. The fact that the _bulk_ of the atmosphere reaches but _three miles_ above the earth's surface, forbids it to be regarded as purely a terrestro-atmospheric phenomenon.

While viewing the more striking and brilliant exhibitions of the aurora, the more undemonstrative and by far the most important and vital operations have been disregarded. The former may not be observed, except occasionally, and fitfully, _can_ only be present when favoring meteorological conditions admit of its disclosure. The latter, more un.o.btrusive and even invisible to the naked eye, are incessantly, and at all seasons, in action, by day as well as by night.[9] May not this auroral display then be regarded in a measure as confirmatory of what the law of conservation had already suggested to us; the existence of a _retro_-current?