John Playfair

“ The education, therefore, which he gave his son, was truly antiphilosophic, 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 ”

“ The result could not fail to solve the difficulty, 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. ”

“ 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. ”

“ It is a good remark of Le Sage, speaking of the analogy between light and the gravific atoms, that if all bodies were transparent, so that light was never stopped in its course, it (light) would not be perceived by us, nor apprehended to exist anymore than the corpuscles to which he ascribes the cause of gravity. We are, in truth, indebted to darkness, or the absence of light, for our idea of the latter, as a separate and independent substance. ”

“ It is impossible not to recognize, in the works of Le Sage, and his manner of thinking, a strong character of originality; and, if a cautious and regulated invention be characteristic of genius, this philosopher must be numbered with those whom nature has particularly distinguished. ”

“ 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 gravitation of a heavy body, in a room, to the roof above it, must, on the common hypothesis of attraction, diminish its weight just as much as it would be diminished by the roof's obstructing some of the gravific atoms. In both cases, the effect would be precisely the same, but too small to make any sensible diminution of the gravitation toward the great mass of the earth.
The obstruction which the gravific atoms would give to the motion of bodies, by producing a kind of resisting medium, was also objected to the doctrine of Le Sage. ”

“ The only difference is, that the bodies, instead of approaching, recede from one another. Whether attraction and repulsion may not be regarded as one and the same law, acting under different circumstances, we do not at present inquire: the object of Le Sage was to reduce them both to impulse; and, could this be done, it would no doubt be a great advance in science, and we might seem, in one quarter at least, to have pushed our researches to their legitimate and proper termination. Our idea of the communication of motion by impulse, is not without difficulty ”

“ Boscovich, who had a system concerning the different forces which are the cause of motion, the very opposite of what has now been laid down , one in which all contact and immediate impulse are denied, could not possibly admit the theory of gravific atoms, and has stated an objection to it, which appears to us of considerable weight. The action of these atoms supposes a vast superfluity of matter, and an infinity of corpuscles, created, each, to give, at most, only a single blow, and many of them never to have any effect whatsoever. ”

“ 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. ”

“ By using the resources which nature had bestowed, and compensating, by much skill and labour, the want of the qualities she withheld, he was able to make no small progress even as an inventor in science. ”

“ 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. ”

“ Such an attempt is undoubtedly attended with difficulty; and perhaps we are destined to remain for ever ignorant of the cause which produces the phenomena of attraction. There can, however, be no impropriety in endeavouring, while there appear to be two kinds of causes that produce motion, to try to reduce them to one. If this is maintained to be impious, it must be on the same principle that Anaxagoras was charged with irreligion, for affirming that the planets are bodies like the earth. The same mistaken zeal has in every age opposed the same obstacles to the advancement of true philosophy. ”

“ Now, it is easy to prove that this angular space is proportional to the square of the distance of the bodies inversely. Therefore, the force with which the bodies will be urged toward one another, will be inversely as the square of the distance; which is the law followed by gravity. This will be true if the bodies are equal in quantity of matter; so as to intercept equal quantities of the atoms. ”

“ A theory of ENDS, or FINAL CAUSES, might be given, exempt from these great defects; embracing the objects both of nature and art; furnishing, first, rules of synthesis for the composition of a work, when the ends and means were both given; and, next, rules of analysis for discovering the intention of an artist, from the examination of his works. M. Reverdil has given us only a few fragments from the treatise which had been drawn up conformably to this plan Those that follow will show in what manner Le Sage had endeavoured to avoid the faults which he has reprobated in others. ”

“ He entitled it Essai de Chimie Mechanique, and endeavoured to explain the whole of chemical action on the principle of impulse. He supposed the impelling fluid to be compared of particles of two kinds, the one greater and the other less; and he demonstrated, in virtue of the single supposition, that homogeneous bodies must attract one another more than heterogeneous. This, however, it must be conceived, comprehends but a small part of the phenomena of chemistry. If was connected with the work on gravity, which was the great business, and the favourite occupation of his life. ”

“ Impulse acts by contact; one moving body communicates motion to another body and the rule by which this [146] change is produced, is, that the motion communicated in any given direction, and that which is lost in the same direction, are precisely equal. The motions that we ourselves impress on the bodies around us, are of this nature.
Again, when a stone falls to the ground, or when iron approaches a magnet, motion is produced without contact; both the bodies acquire motions which are equal, but in opposite directions. ”

“ 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 mathematics 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. ”

“ Suppose that, through anyone point of space, innumerable straight lines are drawn in all different directions, each making a very small angle with those that are nearest it; and let a torrent of particles, or indivisible atoms, move continually in a direction parallel to each of these lines, the section of each torrent, in a transverse direction to its motion, being equal to the section of the sensible world in the same direction. ”

“ Indeed the analogy between those atoms and the particles of light as emitted from bodies, affords the means of refuting the greater part of the objections alleged against the existence of the former. This, however, supposes that the phenomena of light are interpreted in the Newtonian manner, or by an emanation from luminous bodies. If light is considered as an elastic fluid, the vibrations of which communicate to the eye the impressions which give rise to vision, the analogy referred to has no place. ”

“ This, we must observe, is quite a new doctrine. Newton, who was a man of true and sincere piety, thought that he was doing nothing more inconsistent with his duty, when he was endeavouring to explain the action of gravity by that of an etherial [151] fluid, than when he demonstrated that the planets revolve in ellipses, and describe round their common focus areas that are proportional to the time. Dr Clarke was of the Same opinion, and has admitted, that a mechanical explanation of gravity would be of great importance in philosophy. ”

“ The means here employed seem greater than the end, great as it is, can justify; and Le Sage must be allowed, if his system is rejected, to have had the merit of imagining a species of machinery more powerful and extensive than even the preservation of the universe can be supposed to require. ”

“ The more numerous the phenomena, and the greater the degree of precicion, with the more confidence do they conclude, that no other supposition will account for the appearances. It is on such a foundation as this, that the theory of gravitation is established. ”

“ For it is evident, that it either cannot be improved, or that the improvement is highly improbable.
' When all the good of a system can easily be traced to general principles; and when all the evils appear to be exceptions closely connected with some good, the excess being evidently, though perhaps but in a small degree, on the side of good, the contriver must be regarded as beneficent. ”

“ If, now, it be supposed that these atoms are unable to penetrate the solid and indivisible particles of bodies, and, when they enter bodies, can only pass through the intervals or vacuities between their particles, it is evident that they must strike against those particles, and must therefore communicate a certain degree of motion to them, or to the bodies of which they tire composed. ”

“ It may be true, that it imports little to the universe, whether a scarabaeus fly, with more or less ease, or a bee, employ its wax with the greatest possible frugality. It imports much, however, to the scarabaeus or the bee, and, on that account, is an object not unworthy of the attention of the Creator. ”

“ His manuscripts are, a large treatise, Sur les Corpuscules 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. ”

“ 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 ”

“ Such remedies are sometime to be met with in the arts. It was thus that a hint of Monsieur the Prince of Conti, furnished Reaumur with the means of admitting the necessary quantity of air into his furnaces for hatching chickens, by making the heat of the furnace open the door of a register. ”