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the Creator, in the beginning of its existence, ens dowed with certain active and perceptive powers, sufficient to produce all the changes which it undergoes, from the beginning to eternity; which changes, though they may seem to us to be the effects of causes operating from without, are only the gradual and successive evolutions of the monads own internal powers, which would have produced the same motions and changes, although there had been no other being in the universe. He supposed, farther, that the universe is completely filled with monads, without any chasm or void, and thereby every body acts upon every other body, according to its vicinity or distance, and is mutually reacted upon by every other body; hence he considered every monad as a kind of living mirror, which reflects the whole universe, according to its point of view, and represents the whole more or less distinctly. The adoption of this visionary system led LEIBNITZ to oppose, with considerable warmth, several of the leading doctrines of NEWTON, and especially his great principle of gravitation. The hostility of the German philosopher toward the illustrious Briton, was particularly displayed in his controversy with the learned and acute Dr. SAMUEL CLARKE. The papers which gave rise to this controversy, together with the various answers, replies, and rejoinders which took place in the course of it, were transmitted from the one party to the other, through the hands of Queen CAROLINE, consort of GEORGE I. and the patron and correspondent of LEIBNITZ. They were afterwards published, and hold an important place in the philosophical history of the age.

Soon after the theory of monads was published, CHRISTIAN WOLFE, a philosopher of Breslau, formed, on the foundation of this theory, a new system of Cosmology, digested and demonstrated

in a mathematical method. He was one of the most voluminous writers in philosophy which the century afforded, and is considered as the great interpreter and advocate of the Leibnitzian system.

Another theory of matter, which distinguished the eighteenth century, was that of Father BoscoVICH, a learned Jesuit of Italy.-NEWTON paid little attention to the individual atoms of which matter is composed. The attraction and repulsion of which he spoke, appear to refer chiefly to the laws of motion of the larger bodies which we behold. He expressed a suspicion, indeed, that "As the great movements of the solar system are "regulated by universal gravitation; so the mutual "actions of the particles of matter are produced " and regulated by tendencies of a similar kind, "equally, but not more inexplicable; and the principles of which are to be discovered by as "careful an attention to the phenomena, and by "the same patient thinking which he had em"ployed on the planetary motions." But he seems to have willingly yielded to some able and diligent inquirer who should come after him, both the labour and the honour of exploring this extensive field of speculation.

Such an inquirer was the illustrious BOSCOVICH, a man equally distinguished for the purity of his moral and religious character, the depth of his erudition, and the native vigour and acuteness of his mind. A few years after the death of the great British philosopher, he published a new theory of matter. In this theory, the whole mass of which the bodies of the universe are composed, is supposed to consist of an exceeding great, yet finite, number of simple, indivisible, inextended atoms. These atoms are endued by the Creator with repulsive and at

tractive forces, which vary according to the distance. At very small distances the particles of matter repel each other; and this repulsive force increases beyond all limits, as the distances are diminished; and will, consequently, forever prevent actual contact. When the particles of matter are removed to sensible distances, the repulsive is exchanged for an attractive force, which decreases in an inverse ratio with the squares of the distances, and extends beyond the sphere of the most remote comets. Besides these repulsive and attractive forces, the particles of matter have that vis inertie which is admitted by almost all modern philosophers. These atoms, endued with these forces and properties, form the basis of this celebrated system a system unquestionably among the most remarkable that have been proposed to the world in modern times, and which leads to consequences in a very high degree interesting. This system has been, in substance, adopted by many of the learned in various parts of Europe; and is supposed, by those who embrace it, to afford a very satisfactory solution of many difficulties to which former theories evidently gave rise; to explain most happily the various phenomena of matter to which its principles extend; and to receive confirmation by the experiments and discoveries of every day. If we may rely on the doctrines of the ingenious Italian, the stumbling blocks of the infinite divisibility and impenetrability of matter will be taken out of the way; many of the most fruitful sources of perplexity and dispute respecting extension, elasticity, &c. will be cut off; a large portion of the difficulties attending the affinities, attractions and combinations in chemical philosophy, hereafter to be noticed, will diminish, if not disappear; and the path to a just under

standing of all the physical sciences will be simplified and smoothed to a most pleasing degree.

But besides these new theories, and ingenious discussions, respecting the general principles and properties of matter, almost all the particular departments of mechanical philosophy have been investigated with great diligence and success, throughout the whole of the period under consideration.

ELECTRICITY.

Concerning Electricity, that powerful and still mysterious agent, the philosophers of the last age have made splendid discoveries. At the beginning of the eighteenth century, this branch of science could hardly be said to have a place in systems of philosophy. Its phenomena had been so little the subject of experiment, and its laws had been so little comprehended or methodized, that scarcely any thing which deserves the name of theory, on the subject, was then presented to the world. It is true, a number of facts were then known, and some experiments had been made, in order to elucidate this dark recess of science. But they were known, for the most part, only as insulated facts, without any correct idea of the relation subsisting between them, or of the general principles upon which they depended. The principal of these facts had been brought to light by Dr. GILBERT, Mr. BOYLE, and Sir ISAAC NEWTON;

ƒ The author has never yet been able to procure a copy of the Theoria Philosophie Naturalis of BoscovicH, published in 1758; but a very satisfactory abstract of the work is given in the Supplement to the Encyclopædia, lately published by Mr. Dobson. The system is, in some of its parts, so intricate, and throughout so involved in mathematical calculation, that a more full account of it could not be given in the present sketch. It is charged, by some, with having an atheistical foundation and tendency. Of the ground of this charge too little is known by the writer to attempt a discussion of it.

but they continued to lie in uncertainty and con fusion, until 1709, when Mr. HAWKSBEE, an English gentleman, wrote on the subject, and distinguished himself by the experiments and discoveries which he announced. He first took notice of the great electric powers of glass, together with a variety of phenomena relating to electrical attraction and repulsion; insomuch that his writings and experiments form a grand æra in this branch of knowledge. From the time of Mr. HAWKSBEE'S publication, near twenty years elapsed before any farther discoveries or improvements were suggested.

In 1729, the fundamental distinction between conductors and non-conductors was first ascertained by STEPIIEN GRAY, a British philosopher, who had for some time before amused himself with electrical experiments, and who was now accidentally led to the discovery of this important principle. Soon afterwards M. DuU FAY, member of the Academy of Sciences at Paris, in repeating Mr. GRAY's experiments, unexpectedly perceived, for the first time, that difference in the attractive powers of different bodies, which he supposed to arise from two different species of electric fluids, and which he denominated the vitreous and resinous electricities. The drawing a spark from the living body was also first observed by this gentleman, and his companion, the Abbé NOLLET, The next person who distinguished himself in this part of science was Dr. DESAGULIERS, who, though he added but little to the knowledge before possessed, yet made some valuable experiments, and invented some technical terms, such as conductor, electric per se, &c. which have proved highly convenient, and are still in use. About 1742 electricity began to excite attention, and became the subject of much inquiry in Germany. Professor Boze, of Wittem