DESCARTES, HUYGENS, &C.
Descartes flourished about this period, and has the merit of being the first who under took to give an explanation of the celestial motions, or who formed the great and philo sophic conception of reducing all the phenomena of the universe to the same law. The time was now arrived when, froth the acknowledged assimilation of the planets to the earth, this might be undertaken with some reasonable prospect of success. No such at tempt had hitherto been made, unless the crystalline spheres or homocentric orbs of the ancients are to be considered in that light. The conjectures of Kepler about a kind of animation, and of organic structure, which pervaded the planetary regions, were too vague and indefinite, and too little analogous to any thing known on the earth, to be en titled to die name of a theory. To Descartes, therefore, belongs the honour of being the first who ventured on the solution of the most arduous problem which the material world offers to the consideration of philosophy. For this solution he sought no other data than matter and motion, and with them alone proposed to explain the structure and constitu tion of the universe. The matter which he required, too, was of the simplest kind, pos sessing no properties but extension, impenetrability, and inertia. It was matter in the abstract, without any of its peculiar or distinguishing characters. To explain these cha racters, was indeed a part of the task which he proposed to himself, and thus, by the sim plicity of his assumptions, he added infinitely to the difficulty of the problem which he undertook to resolve.
The matter thus constituted was supposed to fill all space, and its parts, both great and small, to be endued with motion in an infinite variety of directions. From the combination of these, the rectilineal motion of the parts become impossible ; the atoms or particles of matter were continually diverted from the lines in which they had begun to move ; so that circular motion and centrifugal force originated from their action on one another. Thus matter came to be formed into a multitude of vortices, differ ing in extent, in velocity, and in density ; the more subtile parts constituting the real vortex, in which the denser bodies float, and by which they are pressed, though not equal ly, on all sides.
Thus the universe consists of a multitude of vortices, which limit and circumscribe one another. The earth and the planets are bodies carried round in the great vortex of the
solar system ; and by the pressure of the subtile matter, which circulates with great rapidi ty, and great centrifugal force, the denser bodies, whit& have less rapidity, and less cen trifugal force, are forced down toward the sun, the centre of the vortex. In like manner, each planet is itself the centre of a smaller vortex, by the subtile matter of which the phe nomena of gravity are produced, just as with us at the surface of the earth.
The gradation,of smaller vortices may be continued in the same 'manner, to explain the cohesion of the grosser bodies, and their other sensible qualities. But I forbear to enter into the detail of a system, which is now entirely exploded, and so inconsistent with the views of nature which have become familiar to every one, that such details can hardly be listened to with patience. Indeed, the theory of vortices did not explain a single pheno menon in a satisfactory manner, nor is there a truth of any kind which has been brought to light by mealy of it. None or the peculiar properties of the planetary orbits were taken into the account ; none of the laws of Kepler were considered ; nor was any explanation given of those laws, more than of any other that might be imagined. The Philosophy of Descartes-could explain all things.equally well, and might have been accom modated to the systems of Ptolemy or Tycho, just as well as to that of Copernicus. It forms, therefore, no link in the chain of physical discovery ; it served the cause of truth only by exploding errors more pernicious than its own ; by exhausting a source of decep tion, which might have misled other adventurers in science, and by leaving a striking proof how little advancement can be made in philosophy, by pursuing any path but that of ex periment and induction. Descartes was, nevertheless, a man of great genius, a deep enlarged views, and entirely superior to prejudice. Yet, in as far as the ex planation of astronomical phenomena is concerned (and it was his main object), he did good only by showing in what quarter the attempt could not be made with success ; he *as the forlorn hope of the new philosophy, and must be sacrificed for the benefit of those who were to follow.