ONE:So matters stood when the introduction of Aristotles entire system into western Europe brought about a revolution comparable to that effected two centuries later by the complete recovery of ancient literature. It was through Latin translations from the Arabic, accompanied by Arabic commentaries, that the Peripatetic philosophy was first revealed in its entirety; and even Albertus Magnus, living in the thirteenth century, seems to have derived his knowledge of the subject from these exclusively. But a few years after the capture of Constantinople by the Crusaders in 1204, the Greek manuscripts of Aristotle were brought to Paris; and, towards the middle of the century, a new Latin version was made from these under the supervision of St. Thomas Aquinas.536 The triumph of Aristotle was now, at least for a time, secured. For, while in the first period of the Middle Ages we find only a single great name, that of Ablard, among the Nominalists, against a strong array of Realists, in the second period the proportions are reversed, and Realism has only a single worthy champion, Duns Scotus, to pit against Albertus, Aquinas, and William of Ockham, each of them representing one of the principal European nations.537 The human intellect, hitherto confined within the narrow bounds of logic, now ranged over physics, metaphysics, psychology, and ethics; and although all these subjects were368 studied only at second-hand, and with very limited opportunities for criticism, still the benefit received must have been immense. The priceless service of the later Schoolmen is to have appropriated and successfully upheld, against Platonism on the one hand and theological mysticism on the other, a philosophy which, however superficial, took in the whole range of natural phenomena, derived all knowledge from external observation, and set an example of admirable precision in the systematic exposition of its results. If no positive addition was made to that vast storehouse of facts and ideas, the blame does not lie with Aristotles method, but with the forcible suppression of free mental activity by the Church, or its diversion to more profitable fields by the study of Roman jurisprudence. Even as it was, Aristotle contributed largely to the downfall of ecclesiastical authority in two ways: directly by accustoming men to use their reason, and indirectly by throwing back mysticism on its proper officethe restoration of a purely personal religion.
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ONE:A learner should, in fact, consider the application and operative conditions of gearing as one of the main parts of the subject, and the geometry or even the construction of wheels as subsidiary; in this way attention will be directed to that which is most difficult to learn, and a part for which facilities are frequently wanting. Gearing may be classed into five modificationsspur wheels, bevel wheels, tangent wheels, spiral wheels, and chain wheels; the last I include among gearing because the nature of their operation is analogous to tooth wheels, although at first thought chains seem to correspond more to belts than gearing. The motion imparted by chains meshing over the teeth of wheels is positive, and not frictional as with belts; the speed at which such chains may run, with other conditions, correspond to gearing.4. The cost of construction and durability.
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ONE:To make this plainer, the laws of forces, the proportion of parts, strength of material, and so on, are subjects of general knowledge that may be acquired from books, and understood without the aid of an acquaintance with the technical conditions of either the mode of constructing or the manner of operating machines; but how to construct proper patterns for castings, or how the parts of machinery should be moulded, forged, or fitted, is special knowledge, and must have reference to particular cases. The proportions of pulleys, bearings, screws, or other regular details of machinery, may be learned from general rules and principles, but the hand skill that enters into the manufacture of these articles cannot be learned except by observation and experience. The general design, or the disposition of metal in machine-framing, can be to a great extent founded upon rules and constants that have general application; but, as in the case of wheels, the plans of moulding such machine frames are not governed by constant rules or performed in a uniform manner. Patterns of different kinds may be employed; moulds may be made in various ways, and at a greater and less expense; the metal can be mixed to produce a hard or a soft casting, a strong or a weak one; the conditions under which the metal is poured may govern the soundness or shrinkage,things that are determined by special instead of general conditions.
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