in their powers, and how disproportioned the instruments! Man can only make use of the power he possesses. Confined to a small quantity of motion, which he can only communicate by impulsion, he can only exert himself upon surfaces; since the power of impulsion in general is only transmitted by superficial contact. He only sees and touches, therefore, the surfaces of bodies, and when he attempts to proceed further, though he opens, divides, and separates, he still touches nothing more than surfaces. To penetrate the interior parts of bodies, he should be possessed of a portion of that power which acts upon the mass, or of gravity, which is Nature's chief instrument. It is, therefore, the defect of instruments which prevents the art of man from approaching that of Nature. His figures, his pictures, his designs, are only surfaces, or imitations of surfaces, because the images he receives by his senses are all superficial, and he is unable to give them the internal parts. What is true with regard to the arts is the same as to sciences, only that the latter is less confined, because the mind is the instrument, and which in the former is subordinate to the senses. But in the sciences the mind commands the senses, as its only endeavour is to search into objects, and not to operate on them; to compare, and not imitate them. The mind, though thus cramped by the senses, though often abused by their false reports, is, notwithstanding, neither less pure nor less active. Man, who has a natural desire to knowledge, began by rectifying, and demonstrating the errors of the senses. He has treated them as mechanical organs, as instruments, the effects of which must be left to experience. Pursuing still his desire of knowledge, he has travelled on with the balance in one hand, and the compass in the other, and has measured both time and space. Thus, he has recognized all the exterior parts of Nature's works, but not being able to penetrate her internal parts by his senses, he has drawn his conclusions and formed a judgment of them by analogy and comparison. He discovered that there exists a general force in matter, quite different from that of impulsion; a force which does not come within the compass of our senses, and which, though we are unable to make use of, Nature employs as an universal agent. He has demonstrated, that this force belongs equally to all matter, in proportion to its mass or real quantity; that its action extends to immense distances, decreasing as the space augments. Afterwards, turning his eyes upon living beings, he found, that heat was another force necessary to their production; that light was a matter endowed with an unbounded elasticity and activity; that the formation and expansion of organized beings were the effects of a combination of all these forces; that the extension and growth of animal or vegetable bodies, follow exactly the laws of attraction, and are effected by an increase of all three dimensions at