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    Software name: appdown
    Software type: Microsoft Framwork

    size: 731MB

    Lanuage:Englist

    Software instructions

      "If you have no objection, sir, I should like to give evidence," he said.


      350In cutting screws it is best not to refer to that mistaken convenience called a wheel list, usually stamped on some part of engine lathes to aid in selecting wheels. A screw to [127] be cut is to the lead screw on a lathe as the wheel on the screw is to the wheel on the spindle, and every workman should be familiar with so simple a matter as computing wheels for screw cutting, when there is but one train of wheels. Wheels for screw cutting may be computed not only quite as soon as read from an index, but the advantage of being familiar with wheel changes is very important in other cases, and frequently such combinations have to be made when there is not an index at hand.


      VII.In the preceding chapter we traced the rise and progress of physical philosophy among the ancient Greeks. We showed how a few great thinkers, borne on by an unparalleled development of intellectual activity, worked out ideas respecting the order of nature and the constitution of matter which, after more than two thousand years, still remain as fresh and fruitful as ever; and we found that, in achieving these results, Greek thought was itself determined by ascertainable laws. Whether controlling artistic imagination or penetrating to the objective truth of things, it remained always essentially homogeneous, and worked under the same forms of circumscription, analysis, and opposition. It began with external nature, and with a far distant past; nor could it begin otherwise, for only so could the subjects of its later meditations be reached. Only after less sacred beliefs have been shaken can ethical dogmas be questioned. Only when discrepancies of opinion obtrude themselves on mans notice is the need of an organising logic experienced. And the minds eye, originally focussed for distant objects alone, has to be gradually restricted in its range by the pressure of accumulated experience before it can turn from past to present, from successive to contemporaneous phenomena. We have now to undertake the not less interesting task of showing how the new culture, the new conceptions, the new power to think obtained through those earliest54 speculations, reacted on the life from which they sprang, transforming the moral, religious, and political creeds of Hellas, and preparing, as nothing else could prepare, the vaster revolution which has given a new dignity to existence, and substituted, in however imperfect a form, for the adoration of animalisms which lie below man, the adoration of an ideal which rises above him, but only personifies the best elements of his own nature, and therefore is possible for a perfected humanity to realise.

      There was a continuous coming and going at the bridge-command, for when I left the shrubberies a great many soldiers of high and low rank, with portfolios and documents, were waiting outside. The soldiers were to escort me back across the bridge, so that I might go on to Vis along the other bank.

      CHAPTER XI. THE NOTES ARE TRACED.With a thorough knowledge of practical machine operation, and an acquaintance with existing practice, an engineer proceeding upon such a plan, will, if he does not overlook some of the conditions, be able to generate designs which may remain without much modification or change, so long as the purpose to which the machinery is directed remains the same.


      Nevertheless Bacons own attitude towards final causes differs essentially from Descartes. The French mathematician, had he spoken his whole mind, would probably have denied their existence altogether. The English reformer fully admits their reality, as, with his Aristotelian theory of Forms, he could hardly avoid doing; and we find that he actually associates the study of final with that of formal causes, assigning both to metaphysics as its peculiar province. This being so, his comparative neglect of the former is most easily explained by the famous comparison of teleological enquiries to vestal virgins, dedicated to the service of God and bearing no offspring; for Mr. Ellis has made it perfectly clear that the barrenness alluded to is not scientific but industrial. Our knowledge is extended when we trace the workings of a divine purpose in Nature; but this is not a kind of knowledge which bears fruit in useful mechanical inventions.553 Bacon probably felt that men would not be very forward to improve on Nature if they believed in the perfection of her works and in their beneficent adaptation to our wants. The teleological spirit was as strong with him as with Aristotle, but it took a different direction. Instead of studying the adaptation of means to ends where it already existed, he wished men to create it for themselves. But the utilitarian tendency, which predominated with Bacon, was quite exceptional with Descartes. Speaking generally, he desired knowledge for its own sake, not as an instrument for the gratification of other wants; and this intellectual disinterestedness was, perhaps, another aspect of the severance effected between thought and matter.

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      Eighth.Rapping plates, draw plates, and lifting irons for drawing the patterns out of the moulds; fallow and match boards, with other details that are peculiar to patterns, and have no counterparts, neither in names nor uses, outside the foundry.

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      Cores are employed mainly for what may be termed the displacement of metal in moulds. There is no clear line of distinction between cores and moulds, as founding is now conducted; cores may be of green sand, and made to surround the exterior of a piece, as well as to make perforations or to form recesses within it. The term 'core,' in its technical sense, means dried moulds, as distinguished from green sand. Wheels or other castings are said to be cast in cores when the moulds are made in pieces and dried. Supporting and venting cores, and their expansion, are conditions to which especial attention [95] is called. When a core is surrounded with hot metal, it gives off, because of moisture and the burning of the 'wash,' a large amount of gas which must have free means of escape. In the arrangement of cores, therefore, attention must be had to some means of venting, which is generally attained by allowing them to project through the sides of the mould and communicate with the air outside.


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