ONE:During the two centuries that ended with the close of the Peloponnesian war, a single race, weak numerically, and weakened still further by political disunion, simultaneously developed all the highest human faculties to an extent possibly rivalled but certainly not surpassed by the collective efforts of that vastly greater population which now wields the accumulated resources of modern Europe. This race, while maintaining a precarious foothold on the shores of the Mediterranean by repeated prodigies of courage and genius, contributed a new element to civilisation which has been the mainspring of all subsequent progress, but which, as it expanded into wider circles and encountered an increasing resistance from without, unavoidably lost some of the enormous elasticity that characterised its earliest and most concentrated reaction. It was the just boast of the Greek that to Asiatic refinement and Thracian valour he joined a disinterested thirst for knowledge unshared by his neighbours on either side.5 And if a contemporary of Pericles could have foreseen all that would be thought, and said, and done during2 the next twenty-three centuries of this worlds existence, at no period during that long lapse of ages, not even among the kindred Italian race, could he have found a competitor to contest with Hellas the olive crown of a nobler Olympia, the guerdon due to a unique combination of supreme excellence in every variety of intellectual exercise, in strategy, diplomacy, statesmanship; in mathematical science, architecture, plastic art, and poetry; in the severe fidelity of the historian whose paramount object is to relate facts as they have occurred, and the dexterous windings of the advocate whose interest leads him to evade or to disguise them; in the far-reaching meditations of the lonely thinker grappling with the enigmas of his own soul, and the fervid eloquence by which a multitude on whose decision hang great issues is inspired, directed, or controlled. He would not, it is true, have found any single Greek to pit against the athletes of the Renaissance; there were none who displayed that universal genius so characteristic of the greatest Tuscan artists such as Lionardo and Michael Angelo; nor, to take a much narrower range, did a single Greek writer whose compositions have come down to us excel, or even attempt to excel, in poetry and prose alike. But our imaginary prophet might have observed that such versatility better befitted a sophist like Hippias or an adventurer like Critias than an earnest master of the Pheidian type. He might have quoted Pindars sarcasm about highly educated persons who have an infinity of tastes and bring none of them to perfection;6 holding, as Plato did in the next generation, that one man can only do one thing well, he might have added that the heroes of modern art would have done much nobler work had they concentrated their powers on a single task instead of attempting half a dozen and leaving most of them incomplete.
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ONE:The sudden and varied resistance to line shafts tends to loosen couplings, destroy gearing, and produce sudden strains that are unknown in other cases; and shafting arranged with the usual proportions for transmitting power will soon fail if applied to driving trip-hammers. Rigid connections or metal attachments ace impracticable, and a slipping belt arranged so as to have the tension varied at will is the usual and almost the only successful means of transmitting power to hammers. The motion of trip-hammers is a curious problem; a head and die weighing, together with the irons for attaching them, one hundred pounds, will, with a helve eight feet long, strike from two to three hundred blows a minute. This speed exceeds anything that could be attained by a direct reciprocal motion given to the hammer-head by a crank, and far exceeds any rate of speed that would be assumed from theoretical inference. The hammer-helve being of wood, is elastic, and acts like a vibrating spring, its vibrations keeping in unison with the speed of the tripping points. The whole machine, in fact, must be constructed upon a principle of elasticity throughout, and in this regard stands as an exception to almost every other known machine. The framing for supporting the trunnions, which one without experience would suppose should be very rigid and solid, is found to answer best when composed of timber, and still better when this timber is laid up in a manner that allows the structure to spring and [107] yield. Starting at the dies, and following back through the details of a trip-hammer to the driving power, the apprentice may note how many parts contribute to this principle of elasticity: Firstthe wooden helve, both in front of and behind the trunnion; nextthe trunnion bar, which is usually a flat section mounted on pivot points; thirdthe elasticity of the framing called the 'husk,' and finally the frictional belt. This will convey an idea of the elasticity required in connecting the hammer-head with the driving power, a matter to be borne in mind, as it will be again referred to.
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