so visionary, and so inconsistent with every principle of mechanical and chemical science. Whence arose that immense chaotic ocean, within whose bosom the summits of the Himmalaya and the Andes were crystallized? Whither did it retire in measured stages of descent, to allow the primary and secondary rock formations, to lay their successive platforms, in the amphitheatre of the globe? The atmosphere has a finite extent, not expanding into space beyond a limited distance from the earth; and thus that world of waters could not escape into another sphere, in vaporous exhalations. The quantity of water requisite to cover the globe to the height of the Himmalaya, or 27,000 feet, would be as great as the whole mass of our actual ocean. Werner was too little of a philosopher to calculate that his crystallization plan called on him to provide a receptacle for 1000 millions of cubic miles of water. The great density of the interior body of the earth, precludes the possibility of that receptacle being subterranean. Since neither celestial nor terrestrial space will admit his retiring chaotic ocean, itself must be deemed an inadmissible supposition. Even granting its reality, and allowing moreover that this water was adequate to dissolve the now insoluble granitic mountains, so as to form a clear and tranquil fluid, we may ask, why the solvent that then exercised so marvellous an affinity for the siliceous and aluminous earths, came so soon to discard them altogether from its bosom? The attractive force that made the solution, should have maintained it. To imagine an effect to come to pass without a cause, is sufficiently ridiculous, though not without a parallel in modern philosophy; but to expect a solidifying action, a stony deposit, from a liquefying agent, unabated in force and magnitude, is truly absurd. The other assumption of the clear and tranquil solution becoming spontaneously muddy and disturbed, as it parted with its solid contents, is repugnant no less to common sense, than to chemical experience. A still liquid containing soluble and

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insoluble matter, usually deposits the insoluble, which is mechanically diffused, before the crystals appear, provided the latter be regularly aggregated, as occurs in granite. We shall not waste more words on this analysis; but conclude with expressing astonishment that the theoretic dreams of Werner should ever have been regarded as realities, in the present age. The old Cosmogony of Leucippus is not more irrational at bottom, and would appear equally plausible, if decked out in fashionable technology.

Buffon's wild fancy of the planets having been originally ignited masses, thrown or struck off in fusion from the sun, and afterwards left revolving round him at distances, and with velocities proportional to the detaching forces, seems to have suggested the geological hypothesis of Cordier. These theorists agree in supposing that an indefinite period of refrigeration had elapsed before the crust had become cool enough to suffer the vapours to condense into water, and to maintain vegetable and animal beings. Fourier has exercised his profound mathematical skill in proving, that the state of calorific equilibrium is now nearly attained, or that the waste by radiation into celestial space is nearly compensated by the expansion of heat from the central parts of the earth, and the absorption of heat from the sunbeams at its surface. This proposition is possibly just, though it will require a century at least of exact thermometric observations, to place it among the inductive truths of science. This for the future; but for the past, we have not the slightest evidence that our terraqueous globe first existed as a molten mass ejected from the solar furnace. Such an assumption is undeserving of place or respect in natural philosophy.

From a long series of observations, made with powerful telescopes, Herschel concluded that the solar light and heat do not emanate from the body or nucleus of the sun, but from certain phosphoric and pyrophoric clouds, which are produced and developed in its atmosphere. He thought

that this immense light-exciting ocean is violently agitated over its whole surface, causing those corrugations of its disc which he has so well described, and which indeed may be observed through a telescope of moderate powers, by an even unpractised eye. When this superficial stratum is broken through, and widely separated, we may discern either the black veil of subjacent solar clouds, or even the solid dark nucleus of the sun itself. Hence Herschel accounts for the dark spots which frequently bestrew the sun's disc, and for the shelving margins which surround them. Across these excavations of the phosphoric film, bridges of luminous matter are seen to stretch, which extending in breadth, finally cause the dark chasm to disappear, and restore to the sun all its original brightness. The area of one of these black spots is often much greater than the whole surface of the terrestrial globe. storm subsides in the solar atmosphere, its parts replaces the luciferous layer. that these spots, first observed by Galileo, led to the discovery of the sun's motion round its axis, and showed that this motion is accomplished in twenty-five days and a half. Had Buffon been acquainted with these great excavations of luminous matter, he would probably have ascribed them to a projection of the solar substance giving origin to some new planet or comet, and causing diminution of the sun's heat proportional to the darkened portion of its orb. But Herschel has shown, on the contrary, that the seasons in which the solar spots are most abundant, are characterised not by decreased emanation of light and heat to the earth, but apparently by an opposite result. We hence infer, that these spots correspond, and are owing to an increased activity in the vibratory motions, by which the sun excites the luminiferous ether, diffused through space.

When the eruptive the equilibrium of Is is well known

The new improvements in optics afford a very unexpected means of determining whether it be true, as Herschel imagined, that the solar light does not issue from an incande

SUN NOT THE MOLTEN PARENT OF THE PLANETS. xxxvii

scent solid or fluid. In fact, when such a body raised to a very high temperature, becomes luminous, the rays which fly off in all directions, do not come from the outer surface only, but also proceed, as the rays of heat do, from a multitude of material points placed beneath or within the surface, to a certain depth, extremely small indeed, but actually existing. Now, such of these rays as traverse the envelope of the heated mass obliquely, acquire and preserve a peculiar property, which can be rendered sensible by experiment; they are polarised. But if the same mass, instead of being rendered luminous by its proper temperature, be only covered with an exterior film of flame, which is the source of its light, the rays do not then possess this property.

Science has thus been enabled to submit to this singular test, the light which the sun sends to us. M. Arago, the author of this beautiful experiment, and by whose labours physics and astronomy have been often enriched, has in fact discovered, that the rays of the sun, when transmitted even obliquely, are not polarised. It is therefore obvious, that in regard to the point in question, the opinion proposed by Herschel is immediately deducible from the latest discovered properties of solar light.

These results are fatal to Buffon and the various Vulcanists of his school. Such theorists can no longer have recourse to the sun as a furnace out of which to scoop ignited spheres; for the nucleus of that luminary may possibly enjoy a habitable planetary temperature.

Two motives have engaged me to undertake the present work. First, a desire to lay before the world a view of certain intrinsic sources of change in the constitution of the earth, which seem to have escaped the observation of philosophers, but which appear to me deducible from modern physical and geological discovery. Second, a wish to lead popular students of philosophy, to the moral and religious uses of their knowledge.

Science has lately gained a vast accession of votaries. During the first twenty years of this century, the only public endowment in Europe for teaching the scientific principles of the Arts to Artisans, by regular courses of lectures, was that founded by Professor Anderson, first administered for three years by Dr. Birkbeck, and ever since by myself. M. Dupin's favourable report of the beneficial results of my tuition among the Glasgow Artisans, published in his Tour through Great Britain, in 1817, drew general attention to the diffusion of science among the people; and within a few years of this date, the Edinburgh School of Arts, the popular lectures in the Conservatory of Arts in Paris, and the Mechanics' Institutions of London and other cities were established. Such is the spirit now diffused among the multitude, that from the capital to the hamlet, Newton and Laplace, Lavoisier and Davy, have become household words. The plodding mechanic fancies himself suddenly grown an adept in Dynamics, and the apprentice boy a master of Statical problems. We are not to wonder, that when physics first unfolds its Diorama to their view, it should raise their minds to a state of morbid excitement, and give birth to strange imaginations. We may even expect to encounter much of that dangerous dogmatism, which a little learning is apt to inspire. But these transition disturbances will subside, as sound knowledge is gained.

Were nothing but substantial inductive science presented in these seminaries, neither the mental nor moral constitution of the multitude would be exposed to any hazard. During the first 17 years of my popular courses, till about the year 1820, most of the Proprietors of our great Factories encouraged the attendance of their Journeymen and Apprentices on the Lectures, and frequently distributed tickets of admission to the most deserving, under a conviction that both their dispositions and talents were thereby improved. About this period, a general schism between the Masters and Workmen began to spread through the manu