'Know first, the heaven, the earth, the main,
The moon's pale orb, the starry train,
Are nourished by a soul,
A bright intelligence, whose flame
Glows in each member of the frame,
And stirs the mighty whole.'
Kepler was no cosmogonist, but he aspired to found a 'physical astronomy,' and in his gropings for a mechanical power that might suffice to regulate the movements of the heavenly bodies, he stumbled upon a mode of action highly appropriate for the explanation of their growth. His ignorance of the laws of motion precluded him from the conception of velocities persistent in themselves, and merely deflected from straight into curved paths by a constant central pull. Hence he was driven to the twofold expedient of creating a whirling medium for maintaining the revolutions of the planets, and of supposing the sun to exercise a 'magnetic influence,' by which they were drawn into closed orbits. Here, then, central forces made a definitive entry on the astronomical stage, although with scarcely a discernible promise of their brilliant future. But it was otherwise with the clumsy machinery they helped to animate. Kepler's simple modus operandi, adopted, or more probably re-invented by Descartes, was published as an epoch-making discovery in his Principia Philosophica (1644), and sprang under its new aspect into swift notoriety. The wide acceptance of the theory of vortices was at least in part due to the impressive largeness of its framework. Descartes left nothing out. The spacious scope of his speculations embraced all that was knowable—nature, animate and inanimate, life and time:
'Planets and the pale populace of heaven,
The mind of man, and all that's made to soar.'
A philosophy, a metaphysic, and a cosmogony were linked together in a single plan. Its author distinguished in matter three gradations of fineness. The coarsest kind was that composing the earth and other opaque bodies; the more sublimated materials of the sun and stars came next; finally, there was the ethereal substance of the skies, so delicately constituted as to be luminous or luminiferous. This last variety was regarded as of subordinate origin. It represented, in fact, a kind of celestial detritus. Interstellar space had gradually become filled with intangible dust, the product of molecular attrition among originally angular solar and stellar particles. Ether was thus supposed to bear to the subtlest description of ordinary matter very much the same sort of relationship that ions presumably do to atoms.
Enough has been said to show that the Cartesian universe was based on crude atomism. Its mode of construction, moreover, evinced a total disregard of mechanical principles. Yet some acquaintance with the laws of motion was by that time easily within reach. The first of the three, at any rate, had been unmistakably enounced by Galileo in 1632, and Descartes himself strongly championed its validity. Yet he thought it necessary, in order to keep the planets moving, to immerse them in one great self-gyrating vortex centred on the sun, each being further provided with a similar subordinate whirlpool for the maintenance of its domestic system. Comets were left in a singularly anomalous position. They circulated freely on the whole, their exemption from planetary restrictions being tacitly recognized; nevertheless, they took advantage of every encountered swirl to help themselves on towards their destination.
Among the fables of pseudo-science Delambre declared that, had the choice been offered to him, he would have preferred the solid spheres of Aristotle to the tourbillons of Descartes. 'The spheres,' he added,[2] 'have proved helpful both for the construction of planetariums representing in a general way the celestial movements, and for their calculation by approximate rules deduced from them; but the system of vortices has never served any purpose whatsoever, whether mechanical or computative.'
Its vogue had, nevertheless, been brilliant and sustained. Advanced thinkers in the time of Louis Quatorze piqued themselves upon being Cartesians. The vortical hypothesis was novel—it seemed daring; and though it might not be true, it had plausibility enough for fashionable currency. Nor did it deserve the unmitigated contempt with which it was treated by Delambre. A glance at the skies makes us pause before condemning it to scornful oblivion. Just two centuries after its promulgation the first spiral nebula was identified in Canes Venatici. That the heavens swarm with analogous objects is certain, and their status as partially developed systems is visible in every line of their conformation. Our own planetary world may, or may not, have traversed the stage they so copiously illustrate; but in any case they prove beyond question that vortices variously conditioned are prevalent among the forms assumed by cosmic masses advancing towards an orderly arrangement.
Mystical cosmogonies belong to the period of ethnic infancy. They have not ceased to be current. World-fables must be invented wherever the obscure wonder of savage communities is excited by the mysterious spectacle of Nature's apparently designed operations and irresistible power. But they were superseded among peoples in the van of progress by philosophic cosmogonies at the epoch when Thales began to diffuse throughout Ionia the wisdom of the Egyptians and Chaldeans. Schemes, however, such as he and his successors elaborated result from the discourse of reason unfettered by any close attention to facts. They have been mostly wrought out by men who, in Delambre's words, 'Dissertaient à perte de vue, sans jamais rien observer, et sans jamais rien calculer.'
The insubstantial fabrics reared by them were then fatally discredited by Baconian methods and the Newtonian reign of law; they survived—forms of thought die slowly—but insecurely, with noticeably undermined foundations. Swedenborg was the last eminent reactionary, and his restoration in 1734 of the Cartesian gyrating medium as the motive power of the solar machine was a palpable failure. It could not be otherwise, since its inceptive idea had grown superannuated. The modern era of scientific cosmogony was at hand.
It was preceded by some remarkable attempts at sidereal generalization. Cosmology is the elder sister of cosmogony. What is must be studied before what was can be inferred. Precedent states remain visionary unless they can be closely linked to actual and observable conditions. Now about the middle of the eighteenth century an intelligible plan of the stellar universe, so far as the telescope had then disclosed it, began to be a desideratum. And the enterprise of supplying the need was undertaken independently by two men of obscure origin and imperfect education—one English, the other German.