could not be published by any other means. In this respect alone, the society confers an important benefit on the science of the country: and the high character and extended celebrity which the volumes of its Transactions have acquired, again reacts upon the cultivation of science, and affords a powerful stimulus to those engaged in such pursuits, to produce papers which may obtain the honour of insertion in those select depositaries. The interchange of ideas, and the personal acquaintances formed or kept up at the meetings of such bodies, are advantages also of no small value; while the concentration of scattered information, and the directing to one centre the energies of many minds, each powerful in its own way, affords the means of mutual assistance in their researches, and thus increases the light thrown upon particular points of enquiry in an almost incalculable ratio.

Bacon, in proposing his new scheme of a philosophical institution, is of necessity led to justify the proposal by a reference to the services of existing institutions, and by showing how little they had done, or by their very nature and constitution were likely to do, towards the real advancement of science. He censures with severity, indeed, but without bitterness, in strong terms, but with a masterly exposition of the facts, which evinces the perfect justice of his condemnation, the system of the colleges and universities of his day. He observes, that the lectures and exercises were all of such a nature, that no deviation from the established routine was likely to be thought of;— that if a solitary attempt were made, the whole burden of it would rest on the individual, who would, moreover, find such attempts a serious impediment to his own advancement. The studies of these places were confined to a certain set of authors, as it were imprisoned within those limits: any one who should venture to deviate from this course, would be immediately condemned as a turbulent innovator. "But," he adds, “in the arts and sciences, as in mines, the * Nov. Organon, i. Aph. 90.

whole region ought to resound with new works and further advances." Such was the state of the case in his day; nor shall we find it much better in later times; for the present it must suffice to remark, that (in regard to Oxford) when the scholastic forms were in a great measure broken up under the reign of Cromwell, the favourable opportunity which was afforded for establishing a better system in their place, was, as we have seen, not lost by a few ardent friends of true science: owing, however, to a variety of causes, their partial attempts failed, as far as the university was concerned; and, with the return of the Stuarts, the old system was re-established in all its authority.

Approaches to the Theory of Gravitation.

Boulliaud, as we have observed, introduced the elliptic orbits in his astronomical system. It is not a little remarkable, that in the same work he should also have broached an idea respecting gravitation, the connection of which with the form of the orbit was of course hidden from him. He remarks, that "if attraction exist, it will decrease as the square of the distance." The scattered elements of the truth were thus being brought together from all quarters; but there still was wanting the master genius to perceive their connection, and to combine them into a whole.

The influence of gravity was, perhaps, yet more distinctly recognised by Borelli, in his work on "Jupiter's Satellites," in 1666. He here maintains expressly, that all the planets perform their motions round the sun according to a general law; that "the satellites of Jupiter and of Saturn move round their primary planets in the same manner as the moon does round the earth, and that they all revolve round the sun, which is the only source of any virtue, and that this virtue attaches them, and unites them so that they cannot recede from their centre of action."

In the same year, Dr. Hooke read to the Royal So

ciety an account of a series of experiments for determining whether bodies experience any variation in their weight at different distances from the centre of the earth. His first experiments (as he himself confesses) were very unsatifactory; but they led him to the ingenious idea of measuring the force of gravity by observing the rate of a pendulum at different altitudes. How far he put this in practice does not appear. He also gave a sort of mechanical illustration of motion in an orbit, by a weight freely suspended by a string, and thus made to oscillate either in an elliptic or circular course.

In 1674, Hooke resumed the subject in a dissertation entitled "An Attempt to prove the Motion of the Earth from Observation," in which the following remarkable passage occurs:

"I shall hereafter explain a system of the world differing in many particulars from any yet known, answering in all things to the common rules of mechanical motions. This depends upon three suppositions. 1st, That all celestial bodies whatsoever have an attraction or gravitating power towards their own centres, whereby they attract not only their own parts, and keep them from flying from them, as we may observe the earth to do, but that they also do attract all the other celestial bodies that are within the sphere of their activity, and consequently, that not only the sun and moon have an influence upon the body and motion of the earth, and the earth upon them, but that Mercury, Venus, Mars, Jupiter and Saturn also by their attractive powers have a considerable influence upon its motion, as in the same manner, the corresponding attractive power of the earth hath a considerable influence upon every one of their motions also. The 2d supposition is this; That all bodies whatsoever, that are put into a direct and simple motion, will so continue to move forward in a straight line, till they are by some other effectual powers deflected and sent into a motion describing a circle, ellipsis, or some other compounded curve line.

The 3d supposition is, That those attract

ing powers are so much the more powerful in operating, by how much the nearer the body wrought upon is to their own centres. Now what these several degrees are,

I have not yet experimentally verified: but it is a notion which, if fully prosecuted, as it ought to be, will mightily assist the astronomers to reduce all the celestial motions to a certain rule, which I doubt will never be done without it. He that understands the nature of the circular pendulum and circular motion will easily understand the whole of this principle, and will know where to find directions in nature for the true stating thereof. This I only hint at present to such as have ability and opportunity of prosecuting this enquiry, and are not wanting of industry for observing and calculating, wishing heartily such may be found, having myself, many other things in hand, which I would first complete, and therefore cannot so well attend to it. But this I do not promise the undertaker, that he will find all the great motions of the world to be influenced by this principle, and that the true understanding thereof will be the true perfection of astronomy."

This passage (though much misunderstood by Delambre,) is extremely interesting, both as showing how nearly Hooke approached to a correct conception of the truth so soon afterwards developed by Newton, and also as giving his own confession as to the points in which he had failed in gaining possession of the whole truth.

Dr. Wallis, in 1666, also threw out some ideas of the same kind, and remarked, "to the objection that it appears not how two bodies that have no tie can have one common centre of gravity, I shall only answer, that it is harder to show how they have it than that they have it."

In 1683, sir C. Wren stated that, several years before, he had endeavoured to explain the planetary motions by the composition of a descent towards the sun, and an impressed motion, but he at length gave it over, not finding the means of doing it."

Establishment of Observatories.

To the period under review belongs the establishment of some of the most celebrated national observatories. If the formation of philosophic societies be a matter of national importance, much more must the institution of observatories be so. To be effective to the great purposes for which they are destined, these establishments must be constructed and fitted up upon a scale far beyond the means of any individual to attain. And the character of the results deduced from the observations made in them, so essential to the purposes of navigation (and in this respect alone, therefore, of immediate national utility), ought to be such as can hardly be secured, unless that responsibility attach to the observer which belongs to a public functionary. But, in a higher point of view, the science which has the heavenly bodies for its objects of contemplation, demands, as far as possible, to be exempted from the vicissitudes of sublunary things. As it is a science

which gains strength but slowly, and requires ages to complete its discoveries, the plan of observation must not be limited by the life of the individual who pursues it, but must be followed out upon the same system for a long succession of years. We have before noticed the munificence displayed by several sovereigns of former ages in this respect. The breaking up of Tycho Brahe's observatory, on which such vast sums had been spent, and which might have continued to be more gloriously employed than it was even under his superintendance, became a sad memorial of the instability of whatever depends on individual greatness, and the necessity of erecting such institutions on the more substantial basis of public endowments. Both the English and French governments had the wisdom to see this, and the national observatory of Greenwich was established in 1675, that of Paris in 1667. In the