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THREE:It is interesting to observe how, here also, the positive science of the age had a large share in determining its philosophic character. Founded on the discovery of the earth��s true shape, Aristotle��s metaphysics had been overthrown by the discovery of the earth��s motion. And now the claims of Cartesianism to have furnished an exact knowledge of matter and a definition of it whence all the facts of observation could be deduced �� priori, were summarily refuted by the discovery421 of universal gravitation. The Cartesians complained that Newton was bringing back the occult qualities of the Schoolmen; but the tendency of bodies to move towards one another proved as certain as it was inexplicably mysterious. For a time, the study of causes was superseded by the study of laws; and the new method of physical science moved in perfect harmony with the phenomenism of Locke. One most important consequence of this revolution was to place the new Critical philosophy on a footing quite different from that occupied by the ancient sceptics. Both restricted certain knowledge to our own states of consciousness; but it now appeared that this might be done without impeaching the value of accepted scientific conclusions, which was more than the Academic philosophy would have admitted. In other words, granting that we were limited to phenomena, it was shown that science consisted in ascertaining the relations of these phenomena to one another, instead of to a problematic reality lying behind them; while, that such relations existed and were, in fact, part of the phenomena themselves, was what no sceptic could easily deny.The third plan of boring with bars resting in bearings is more extensively practised, and has the largest range of adaptation. A feature of this plan of boring is that the form of the boring-bar, or any imperfection in its bearings, is communicated to the work; a want of straightness in the bar makes tapering holes. This, of course, applies to cases where a bar is fed through fixed bearings placed at one or both ends of a hole to be bored. If a boring-bar is bent, or out of truth between its bearings, the diameter of the hole being governed by the extreme sweep of the cutters is untrue to the same extent, because as the cutters move along and come nearer to the bearings, the bar runs with more truth, forming a tapering hole diminishing toward the rests or bearings. The same rule applies to some extent in chuck-boring, the form of the lathe spindle being communicated to holes bored; but lathe spindles are presumed to be quite perfect compared with boring bars.