5. As the strength of shafts is determined by their size, and their size fixed by the strains to which they are subjected, [45] strains are first to be considered.
"Latest society scandal!" came the shrill voices. "Latest society sensation! Flight of the Countess Lalage!"By assuming this or any other well-proved example, and estimating larger or smaller shafts by keeping their diameters as the cube root of the power to be transmitted, the distance between bearings as the diameter, and the speed inverse as the diameter, the reader will find his calculations to agree approximately with the modern practice of our best engineers. This is not mentioned to give proportions for shafts, so much as to call attention to accidental strains, such as winding belts, and to call attention to a marked discrepancy between actual practice and such proportions as would be given by what has been called the measured or determinable strains to which shafts are subjected.There is one more aspect deserving our attention, under which the theory of Nature has been presented both in ancient and modern times. A dialogue which, whether rightly or wrongly attributed to Plato, may be taken as good evidence on the subject it relates to,65 exhibits Hippias in the character of a universal genius, who can not only teach every science and practise every kind of literary composition, but has also manufactured all the clothes and other articles about his person. Here we have precisely the sort of versatility which characterises uncivilised society, and which believers in a state of nature love to encourage at all times. The division of labour, while it carries us ever farther from barbarism, makes us more dependent on each other. An Odysseus is master of many arts, a Themistocles of two, a Demosthenes of only one. A Norwegian peasant can do more for himself than an English countryman, and therefore makes a better colonist. If we must return to Nature, our first step should be to learn a number of trades, and so be better able to shift for ourselves. Such was the ideal of Hippias, and it was also the ideal of the eighteenth century. Its literature begins with Robinson Crusoe, the story of a man who is accidentally compelled to provide himself, during many years, with all the necessaries of life. Its educational manuals are, in France, Rousseaus mile; in England, Days Sandford and Merton, both teaching that the young should be thrown as much as possible on their own resources. One of its types is Diderot, who learns handicrafts that he may describe them in the Encyclopdie. Its two great spokesmen are Voltaire and Goethe, who, after cultivating every department of literature, take in statesmanship as well. And its last word is Schillers Letters on Aesthetic Culture, holding up totality of existence as the supreme ideal to be sought after.
FORE:Machinery of transportation.The next and perhaps the most important point in favour of Epicureanism is its theory of pleasure as the end of action. Plato had left his idea of the good undefined; Aristotle had defined his in such a manner as to shut out the vast majority of mankind from its pursuit; the Stoics had revolted every instinct by altogether discarding pleasure as an end, and putting a purely formal and hollow perfection in its place. It must further be admitted that Epicurus, in tracing back justice to the two ideas of interest and contract, had hold of a true and fertile principle. Nevertheless, although ethics is his strongest ground, his usual ill-luck pursues him even here. It is where he is most original that he goes most astray. By reducing pleasure, as an end of action, to the mere removal of pain, he alters earlier systems of hedonism for the worse; and plays the game of pessimism by making it appear that, on the whole, death must be preferable to life, since it is what life can never bea state of absolute repose. And by making self-interest, in the sense of seeking nothing but ones own pleasure or the means to it, the only rule of action, he endangers the very foundations of society. At best, the selfish system, as Coleridge has beautifully observed, stands in a similar relation to the law of conscience or universal selfless reason, as the dial to the sun which indicates its path by intercepting its radiance.210 Nor is the indication so certain as Coleridge admitted. A time may come when116 self-sacrifice shall be unnecessary for the public welfare, but we are not within a measurable distance of it as yet.
FORE:Bruce caught his breath sharply. He had scarcely time to consider what it all meant when the light flared up again, and the fair woman returned with a kettle and basin and a tin of mustard.
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CHAPTER XXI. MECHANICAL DRAWING.The last mentioned principle gives one more illustration of the distinction between Aristotles system and that of the evolutionist, properly so called. The continuity recognised329 by the former only obtains among a number of coexisting types; it is a purely logical or ideal arrangement, facilitating the acquisition and retention of knowledge, but adding nothing to its real content. The continuity of the latter implies a causal connexion between successive types evolved from each other by the action of mechanical forces. Moreover, our modern theory, while accounting for whatever is true in Aristotles conception, serves, at the same time, to correct its exaggeration. The totality of existing species only imperfectly fill up the interval between the highest human life and the inorganic matter from which we assume it to be derived, because they are collaterally, and not lineally, related. Probably no one of them corresponds to any less developed stage of another, although some have preserved, with more constancy than others, the features of a common parent. In diverging from a single stock (if we accept the monogenetic hypothesis,) they have become separated by considerable spaces, which the innumerable multitude of extinct species alone could fill up.29The teleology of Aristotle requires a word of explanation, which may appropriately find its place in the present connexion. In speaking of a purpose in Nature, he does not mean that natural productions subserve an end lying outside themselves; as if, to use Goethes illustration, the bark of cork-trees was intended to be made into stoppers for ginger-beer bottles; but that in every perfect thing the parts are interdependent, and exist for the sake of the whole to which they belong. Nor does he, like so many theologians, both ancient and modern, argue from the evidence of design in Nature to the operation of a designing intelligence outside her. Not believing in any creation at all apart from works of art, he could not believe in a creative intelligence other than that of man. He does, indeed, constantly speak of Nature as if she were a personal providence, continually exerting herself for the good of her creatures. But, on looking a little closer, we find that the agency in question is completely unconscious, and may be identified with the constitution of each particular thing, or rather of the type to which it belongs. We have said that Aristotles intellect was essentially descriptive, and we have here another illustration of its characteristic quality.333 The teleology which he parades with so much pomp adds nothing to our knowledge of causes, implies nothing that a positivist need not readily accept. It is a mere study of functions, an analysis of statical relations. Of course, if there were really any philosophers who said that the connexion between teeth and mastication was entirely accidental, the Aristotelian doctrine was a useful protest against such an absurdity; but when we have established a fixed connexion between organ and function, we are bound to explain the association in some more satisfactory manner than by reaffirming it in general terms, which is all that Aristotle ever does. Again, whatever may be the relative justification of teleology as a study of functions in the living body, we have no grounds for interpreting the phenomena of inorganic nature on an analogous principle. Some Greek philosophers were acute enough to perceive the distinction. While admitting that plants and animals showed traces of design, they held that the heavenly bodies arose spontaneously from the movements of a vortex or some such cause;222 just as certain religious savants of our own day reject the Darwinian theory while accepting the nebular hypothesis.223 But to Aristotle the unbroken regularity of the celestial movements, which to us is the best proof of their purely mechanical nature, was, on the contrary, a proof that they were produced and directed by an absolutely reasonable purpose; much more so indeed than terrestrial organisms, marked as these are by occasional deviations and imperfections; and he concludes that each of those movements must be directed towards the attainment of some correspondingly consummate end;224 while, again, in dealing with those precursors of Mr. Darwin, if such they can be called, who argued that the utility of an organ does not disprove its spontaneous origin, since only the creatures which, by a happy accident, came to possess it would survivehe334 answers that the constant reproduction of such organs is enough to vindicate them from being the work of chance;225 thus displaying his inability to distinguish between the two ideas of uniform causation and design.