Letters On Different Subjects In Natural Philosophy PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1837 edition. Excerpt: ... LETTER LIII. Continuation. Of the Mutual Attraction of the Heavenly Bodies. The Newtonian System, you will easily believe, made at first a great noise, and with good reason, as no one had hitherto hit upon a discovery so very fortunate, and which diffused at once such clear light over every branch of science. It has been expressed by several names, of which it is proper you should be informed, because it is frequently the subject of conversation. It has been denominated the system of universal gravitation; for Newton maintained, that not only the earth, but all the heavenly bodies in general, are endowed with this property--of attracting those which surround them with a power similar to that of weight or gravity; hence is derived the term gravitation. This power is, however, totally invisible; for we see nothing acting upon bodies, and pressing them towards the earth, and still less towards the heavenly bodies. The loadstone, by which iron and steel are attracted without our being able to discern the cause, presents a phenomenon somewhat similar. Though it be now certain that this is produced by a substance extremely subtile, which penetrates through the pores of the loadstone and of the iron, it may, however, be affirmed, that the loadstone attracts iron, and that iron is attracted by it, provided this manner of speaking does not exclude the true cause. It may likewise be affirmed, then, that the earth at tracts all bodies that are near it; nay, those which are at very great distances: and we may consider the weight or gravity of bodies as the effect of the attraction of the earth, which acts even upon the moon. Again, the sun and all the planets are endowed with a similar power of attraction, which extends to all bodies. In conformity...