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Notice de la Vie et des Ecrits de George Louis Le Sage de Geneve, Membre de l'Academie et de l'Institut de Bologne, &c. &c. Redigée après ses Notes, par Pierre Prevost. A Geneve, chez Paschoud.

THE biographical sketch here announced, has more than an ordinary claim to the attention of the reader. The subject of it is a philosopher, who, beside the peculiarities incident to genius, had several that belonged exclusively to himself. These he was careful to study and explain; and the notes which he has left behind him, seem to entitle him to the rare eulogy, of having given an accurate and candid delineation of his own character. His biographer, too, had the advantage of being intimately acquainted with the person whom he has undertaken to describe, and has been attentive to mark whatever appeared singular in the constitution or progress of his mind.

George Lewis Le Sage was born at Geneva in 1724, to which city his father, a native of France, had for some time retired, and lived by giving private lessons in mathematicks and natural philosophy. The son was early initiated in these studies; receiving, at the same time, in all the branches of literature, as liberal a course of education as his father's limited income would allow. A marked opposition, however, in their tastes and intellectual propensities, prevented the son from reaping, from his father's instructions, all the advantages that might have been expected. The old man was well informed; but his knowledge was very much confined to facts, and was accompanied with little tendency to reason or to generalize His son, again, even when a boy, delighted in connecting his ideas by general and abstract principles, and was not more inquisitive about facts, than about the relations in which they stood to one other. This propensity arose, in some measure at least, from the weakness of his memory, which forced him to study the most just and constant connexions among things, in order to prevent both words and ideas from escaping his recollection entirely. "It was thus," says M. Prevost, "that we saw him, in his maturer years, and particularly in his old age, avoiding, with the greatest care, whatever could trouble the order of his thoughts, and substituting, with much art, a logical series of mental operations to the effort which the recollection of a single unconnected fact would necessarily have cost him.”

The history of Le Sage does, indeed, illustrate, in the clearest manner, the relation between the faculties of memory and abstraction, and the power which each has to supply the deficiencies of the other. Generalization gives us a command over our ideas more complete than we can ever derive from the mere efforts of memory. It holds in its hand the clue by which this latter faculty must be guided through the labyrinth of things; and there is room to doubt, whether the power thus given to the mind is not the main source of the delight arising from abstract and philosophick speculation. Were the memory in itself to become so perfect, as to be independent of connecting principles, generalization would not be necessary, and perhaps would rarely be attempted.

Two minds, both disposed to the acquisition of knowledge, could hardly be constituted with less conformity to one another, than those of Le Sage and his son. When the young man was labouring to classify his ideas, and to reduce them under general heads, the father was perpetually starting objections to his rules, and bringing forward the instances most difficult to be reduced to any general principle of arrangement. This seemed to proceed, not from any desire to embarrass or distress his son, but from a dislike which he had conceived (singular, doubtless, in a mathematician) to general me

thods, and to all systems whatsoever. The education, therefore, which he gave his son, was truly antiphilosophick, and certainly had no tendency to produce that love of order, system, and method, which characterized him through his whole life. But the mind may be constituted with some powers so weak, that discipline cannot improve them; and with others so strong, that discipline, when most perverse, cannot destroy them. Nothing could give to young Le Sage a memory nearly equal to that of ordinary men; and nothing could take from him a delight and skill in generalization, which were vastly superiour.

We must not imagine from this, that the whole plan of the old man, in the education of his son, was as perverse as in the case here mentioned. The information he communicated, even with so little of method and arrangement to connect the parts together, was of great value to his son, who, through his whole life, used to speak with much gratitude of his father's attention to his instruction, and of the pleasure and advantage he derived from his conversation.

The inquisitive turn of Le Sage soon displayed itself in questions, to which he did not always receive the kindest or most satisfactory answers, especially from his mother, who appears to have had none of the gentleness and patience necessary for the instruction of children. This led him to think of having recourse to trial and experience, and to interrogate nature rather than any other instructer. One of his first attempts of this sort has been recorded in his notes, and, from the singularity of it deserves to be remembered.

At the time we are now speaking of, the Sabbath was observed at Geneva, with a gloom and austerity of which we, in Scotland, can probably form a more correct notion than the inhabitants of any other country in Christendom. Le Sage felt some curiosity to know whether the Author of Nature still continued to impose on himself the same law that originally marked the institution of the day of rest. It would have puzzled the first philosopher in Europe to think of any method by which this question could be brought to the decision of experiment; but the ingenuity of our young inquirer soon suggested an expedient. He measured, with great care, the increase of a plant, day after day, in order to discover whether it would cease growing on the Sabbath. The result could not fail to solve the diffi culty, and to convince the young man, that though the work of creation might terminate, the work of Providence is never interrupted.

The pensive and contemplative turn of Le Sage was increased by the circumstance of his health being delicate, and his temperament too weak, to allow him to join in the fatiguing exercises which amused and occupied his companions. Great modesty, sensibility, and reserve, added, as far as his mother was concerned, to the want of comfortable society at home, condemned him almost to continual solitude, and rendered the acquisition of knowledge his only enjoyment. Thus, from circumstances apparently unfortunate, much of his intellectual excellence may be supposed to have arisen.

It is material to observe every circumstance that gave a determination to a mind that has in any thing attained celebrity; but it is very rarely that this can be done so well as in the instance we have now before us. The father of our young philosopher had but few books; and almost the only entire work on physicks, which he possessed, was that of Bernard Palissy. The writings of a man who was self-instructed; who had paid no regard to authority, when not supported by experience; who had made valuable discoveries, and reached some very sublime and just notions concerning the

structure and the revolutions of the globe, could not fail to make a strong impression on a young mind already inspired by the love of knowledge. However, though Le Sage became a great cosmologist, it does not appear that geology, of which Palissy was in some measure the founder, ever attracted much of his attention.

When he was not much more than thirteen, his father put into his hands the Antiquité Expliquée of Montfaucon, in order to excite in him a curiosity about researches into antiquity. It was the fate of this young man, however, to derive, from the means used for his instruction, advantages very different from those that were intended, and often of far greater value. The weakness of Montfaucon's conjectures, concerning the use of many of the instruments he has described, did not escape the observation of Le Sage; and he began, even then, to try to establish some general and certain rules for discovering the end of a workman from the inspection of his work. Such extent of view, at so early a period of life, has rarely occurred, and must be considered as a decided mark of genius and originality. Some years after this period, connecting the pursuit just mentioned with one closely allied to it, namely, the rules that must guide us when, in the works of nature, we would trace the marks of the wise design of the Creator, he formed the idea of a treatise, entitled Teleology, and of which an account will afterwards be given.

The perusal of Lucretius is one of the events that did most determine the objects of Le Sage's researches, and, indeed, the whole colour and complexion of his future speculations The precise time when this happened does not appear, though it was certainly very early, and before he had attained the age of twenty. It was then that he conceived the notion of a mechanical explanation of gravity, and of the reduction of all the motions observed in nature, to the principle of impulsion. This was suggested by the atoms of Lucretius; and the invention of a system by which such an explanation could be given, even with tolerable plausibility, must be considered as a work of great merit by all who know the difficulty with which it is attended, and its importance to philosophy. The system by which Le Sage proposed to effect this great object will be by and by considered.

Le Sage had the good fortune to study mathematicks under Cramer, and philosophy under Calendrini, two eminent professors who then adorned the university of Geneva. When it became necessary for him to make choice of a profession, he gave the preference to that of medicine. The pursuit of this study led him first to Basle, and afterwards to Paris. At the former place, he became acquainted with Daniel Bernoulli, from whom, however, his merit seems to have been completely concealed, by his awkwardness and diffidence. He says of himself, when he entered at this university—“ Ill dressed, timid, and expressing myself with difficulty, I was quite neglected In the first months of my stay at Basle; insomuch, that they did not even think it worth while to speak French before me." He undertook the study of the German; but the weakness of his memory did not permit him to succeed.

The same awkwardness could not fail to have effects at Paris yet more unfavourable, as the narrowness of his income must likewise have had ; yet he persevered, not only in pursuing medicine, but in applying to his favourite objects in philosophy. At last he returned to Geneva; but not having the freedom of a burgess of the city, he was refused the privilege of practising as a physician; and saw himself, in the end, forced to relinquish every other view of fixing himself in life, but that of following the business of his father, and giving lessons in mathematicks and natural philosophy.

For this he appears to have been well qualified. He says of himself, that the structure of his mind was such, as had fitted him for understanding the mathematicks well, but not extensively. “Propre à bien savoir les mathematiques, mais non a en savoir beaucoup." The first part of this assertion, we imagine, may be understood more literally than the last; though it is probably true that he was not quite master of all the modern improvements of the calculus. Some of his remarks on the state of the mathematical sciences in France are worth attending to. In a letter to the duke de Rochefoucault, whom he had had the honour to instruct in the mathematicks, dated in 1778, he has this observation.

In their elementary treatises of mathematicks and physicks, the French writers take so little trouble about the foundations of those calculations which they accumulate without end, that it seems as if they wanted to make all their pupils mere clerks in a banking house, or assistants in an observatory. They treat geometry the least geometrically possible, under the pretence that algebraick demonstrations are the shortest: as if the only object were to get to the end, and as if the road leading to it were of no importance. They are in haste to give a few notions, rather grammatical than intellectual, of the sublimer parts, before they have sufficiently developed the elements. They seem desirous of reducing astronomy, the science of motion, and chymistry, to be nothing but the humble attendants on navigation, gunnery, and the arts; as if all the world was destined for inspectors of the marine, of artillery, or manufactures; and as if the cultivation of reason was nothing in comparison with the art of getting wealth. This was not the proceeding of Descartes or Newton. p. 272.

This character of the French elementary writers, though, in certain respects, just, evidently has something of the air of satire, and must not be received as perfectly correct. Of too little regard to the methods of pure geometry, and too much haste to reach the more profound parts of the calculus, they may certainly be accused. But a general preference of the methods of algebra and analysis, cannot be regarded as an errour, if the foundations of those methods are carefully and accurately explained. Analytical reasonings are so much preferable to synthetical, and the art of investigation is so much more easily learned in the school of algebra than in any other, that, in a system of mathematical instruction, this latter science is undoubtedly of the first consideration. It is true, on the other hand, that the methods of analysis are not confined to algebra. Geometry has its analytical reasonings, not so extensive, nor so general, as those of algebra, but possessing a degree of simplicity and beauty that is not excelled, or rather, we think, not equalled in any other branch of science. It is a stronger proof of the neglect of geometry, among the French mathematicians, than any thing that Le Sage has alleged that in the Encyclopedie, intended to exhibit a complete picture of the knowledge of the eighteenth century, the article geometrical analysis is not to be found.

The love of accurate and precise knowledge, which Le Sage possessed eminently, probably qualified him well for a teacher of the mathematical sciences. He had several illustrious pupils, and nonę, certainly, who does him more credit than the present professor of mathematicks in the university of Geneva. M. S. L'Huilier was his relation, and was instructed by him in the science which he now professes with so much credit both to his master and himself. He is one of the few mathematicians equally versed in the simple and elegant methods of the ancient geometry, and in the profound resear ches of the modern analysis.

Le Sage, through his whole life, had to struggle with a feeble constitution, as well as the mental defects which have been already mentioned. He was particularly afflicted with sleeplessness, which, at times, used greatly to affect his intellectual powers, and reduce them to a state of extreme debility. Notwithstanding this, by employing every moment, when his mind was

clear and active, preserving such order and regularity as supplied the want of memory, committing every thing to writing, and having his papers in a state of the most complete arrangement, he was able to accomplish a great deal, and to devote much time to philosophical pursuits.

His studies, however, were rendered less useful than they might have been with the originality of his turn of thinking, the precision of his knowledge, and the extent of his views, by the number of objects to which he directed his attention, and by his frequent changes from one pursuit to another. Though he came back easily to the same object, yet this did not entirely make up for the want of the continued application necessary in all great undertakings.

Accordingly, though few men wrote so much, and so accurately, he published nothing in his lifetime but mere opuscula, and has left few, if any, of his numerous manuscripts completely ready for the press.

One of the principal pieces which appeared in his lifetime, shared the prize proposed by the academy of Dijon, in 1758, on the cause of chymical affinities. He entitled it, Essai de Chimie Mechanique, and endeavoured to explain the whole of chymical action on the principle of impulse. He supposed the impelling fluid to be composed of particles of two kinds; the one greater, and the other less: and he demonstrated, in virtue of that single supposition, that homogeneous bodies must attract one another more than heterogeneous. This, however, it must be confessed, comprehends but a small part of the phenomena of chymistry. It was connected with the work on gravity, which was the great business, and the favourite occupation of his life.

An essay, "Sur les Forces Mortes," which he sent to the academy of sciences at Paris, was never published.

In the history of the same academy for 1756, a remark is inserted from Le Sage, containing the detection of an errour committed by Euclid, in the eleventh book of his Elements, on the subject of solid angles. It is remarkable, that nearly about the same time, Dr. Simpson, of Glasgow, made a similar detection, with respect to the manner in which equal solids are treated by the Greek geometer.

The tract, entitled "Lucrece Nutonien," was published in the Berlin Memoirs for 1782.

Besides these, he published a few other occasional pieces, and seems to have kept up a pretty extensive correspondence with several of the first philosophers of the age. His manuscripts are, a large treatise “ Sur les Corpusculus Ultramondains," subordinate to which is " Histoire Critique de la Pesanteur." This contains much learning, and treats of all the notions that have been entertained on the subject of gravity, and all the theories contrived for explaining it. A treatise on cohesion, intended to show that it cannot be explained by the Newtonian attraction, is recommended by M. Prevost as a work of great merit, written during the full activity and vigour of the author's mind.

To these must be added the following: on elastick fluids; on general physicks; on logick; on moral philosophy; and on final causes: also, Melanges Dystactiques, &c. Among the latter was an Essay on Punctuation, concerning which he had a system of his own. To this system he adhered rigidly; and it is said to be very philosophical; but, perhaps, for that very reason, it has never come into use.

It may be thought extraordinary, that so much should have been done, and yet so little completed. The habit of continually amassing materials, without reducing them into form, had grown on Le Sage to an excessive

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