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Show 110 WEIGHT AND MAGNITUDE; thing that can speed our advancement, or prevent , our turning aside from it. Those who would be profitable observers of nature must have very clear and co:rect noti~ms on the subjects of weight and ma~mtude., whi~h are the general qualities of matter m all Its varJed forms, whether living or dead: they are the standards by which all things are determined, and the only means by which one thing can be accurately co~pared with another: and when we come to any thmg, be it what it may, that we cannot determine either.by weight or by measur~, our knowledge of that thmg is always vague and Imperfect. . Weight is nothing more than the tendency whiCh all portions of matter have towards eac? other; not in the formation of crystals of a certam shape, as was mentioned in the case of common salt, or in the formation of drops of water, masses of stone, plants, animals, or any thing else that has a specific, or individual form and character; but a more general property, common to all matter, and, in fact, the only test by which matter is known, or its real quantity ascertained. In material bodies, near the earth's surface, where all the productions of nature that we can more immediately observe are, weight means the same thing as the tendency which those bodies have to fall to the earth when not supported, and to remain on its surface after they have fallen or when they are once there, if not raised up by some other force powerful enough for counteracting that tendency. As this weight is, as we may say, a universal property, it should be understood by even the most unpretending observer, if he is to apply his observation to any useful purpose, how simple soever th'it purpose may be. Its laws are as simple as itself is universal; and as they can be stated in very plain language, every one should bear them in mind. They are these:- }..,irst, the tendency which any piece of matter FIRST LAW OF GRAVI'l'ATION. 111 fm.s to gravitate, or, as it i~ termed, to f~ll, is ex~ctly in proportion to the quanht.y of matt~r m that .P1ece; and thou()"h its effects may be vaned by circumstances, i~ itself it remains unaltered. So that, if the piece were broken into the gre~tes~ nu~ber of smaller pieces the amount of grav1tat10n m them would be exact~ly the same as that i!l the lar~e piece before it was broken. So also, If any ptece or pieces of matter be joined to another piec~ or other pieces the gravitation of the collectwn IS always exactly equal to the sum of all the gravitations of the individual parts. This property is indestructible ; and not. only forms part of the constitution of matter, but IS the property by means of which alone we acquire any knowledge of matter at all. That which the tongt?-e tastes or the nose scents, we cannot measure, or In anywi'se know but by inference; and it is by inference that we know what the ear hears, and even what the eye sees, though after long practice we take no notice -of, and therefore forget, the process of inferrinO". Our knowledge of extension or magnitude to~ is an inference ; and it is impossible for any 'one' to say how many millions of feelings a child must sum up before it can feel the length of its own finger, or make sure of touchin~ the fing~r of the left hand with the finger of the nght. It IS clear howev·er, that in this dawn and birth of knowledge~ this fountain and day-spri~g of all ingenuity and of all action, we borrow nothmg from the eye ; {Qr we can lay our finger upon any reachabl~ point of our own body with our eyes shut as accurately as we can with the eyes open, if, indeed, not more accurately. Any one may be convinced of the truth of this, by extending his arms, clinching his hands, except the forefingers, and then bringing these to touch each other, in front where he sees them, and behind hi~ or over his head, where he sees them not ; and, |