FORE:It has, until lately, been customary to speak as if all that Aristotle knew about induction was contained in a few scattered passages where it is mentioned under that name in the Analytics. This, no doubt, is true, if by induction we mean simple generalisation. But if we understand by it the philosophy of experimental evidencethe analysis of those means by which, in the absence of direct observation, we decide between two conflicting hypothesesthen the Topics must be pronounced as good a discussion on the subject as was compatible with his general theory of knowledge. For he supposes that there are large classes of phenomena, including, among other things, the whole range of human life, which, not being bound by any fixed order, lie outside the scope of scientific demonstration, although capable of being determined with various degrees of probability; and here also what he has in view is not the discovery of laws, but the construction of definitions. These being a matter of opinion, could always be attacked as well as maintained. Thus the constant conflict and balancing of opposite forces, which we have learned to associate with the sublunary sphere, has its logical representative no less than the kindred ideas of uncertainty and vicissitude. And, in connexion with this side of applied logic, Aristotle has also to consider the requirements of those who took part in the public debates on disputed questions, then very common among educated Athenians, and frequently turning on verbal definitions. Hence, while we find many varieties of reasoning suggested, such as Reasoning by Analogy, Disjunctive Reasoning, Hypothetical Reasoning (though without a generalised expression for all its varieties), and, what is most remarkable, three out of Mills four Experimental Methods,288 we do not find that any interesting or395 useful application is made of them. Even considered as a handbook for debaters, the Topics is not successful. With the practical incompetence of a mere naturalist, Aristotle has supplied heads for arguments in such profusion and such utter carelessness of their relative importance that no memory could sustain the burden, except in the probably rare instances when a lifetime was devoted to their study.
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FORE: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.331
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THREE:Slackening speed, the seaplane raced along until, with a hand clinging to a brace and his body leaning far over the dancing waves, its passenger on the wing scooped up the life preserver.
THREE:
THREE:"To listen to your story," said Lawrence.
