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THREE:187Water-wheels, next to steam-engines, are the most common motive agents. For centuries water-wheels remained without much improvement or change down to the period of turbine wheels, when it was discovered that instead of being a very simple matter, the science of hydraulics and water-wheels involved some very intricate conditions, giving rise to many problems of scientific interest, that in the end have produced the class known as turbine wheels. FORE:Whether neutral or foreigner, no one could help being deeply moved. Men and women, boys and girls, pressed once more through the German fence, just to shake hands with someone they had recognised. No wailing followed, but when hands were gripped, with a suppressed sob, they said:

THREE: FORE:When the Academicians pass from the form to the matter of dogmatic philosophy, their criticisms acquire greater interest and greater weight. On this ground, their assaults are principally directed against the theology of their Stoic and Epicurean rivals. It is here in particular that151 Carneades reveals himself to us as the Hume of antiquity. Never has the case for agnosticism been more powerfully made out than by him or by the disciples whom he inspired. To the argument for the existence of supernatural beings derived from universal consent, he replies, first, that the opinion of the vulgar is worthless, and secondly, that men��s beliefs about the gods are hopelessly at variance with one another, even the same divinity being made the subject of numberless discordant legends.238 He reduces the polytheistic deification of natural objects to an absurdity by forcing it back through a series of insensible gradations into absolute fetichism.239 The personification of mental qualities is similarly treated, until an hypothesis is provided for every passing mood.240 Then, turning to the more philosophical deism of the Stoics, he assails their theory of the divine benevolence with instance after instance of the apparent malevolence and iniquity to be found in Nature; vividly reminding one of the facts adduced by Mr. Herbert Spencer in confutation of the similar views held by modern English theologians.241 As against the whole theory of final causes, Carneades argues after a method which, though logically sound, could not then present itself with the authority which advancing science has more recently shown it to possess. ��What you Stoics,�� he says,152 ��explain as the result of conscious purpose, other philosophers, like Strato for instance, explain with equal plausibility as the result of natural causation. And such is our ignorance of the forces at work in Nature that even where no mechanical cause can be assigned, it would be presumptuous to maintain that none can exist.242 The reign of law does not necessarily prove the presence of intelligence; it is merely the evidence of a uniform movement quite consistent with all that we know about the working of unconscious forces.243 To contend, with Socrates, that the human mind must be derived from a Universal Mind pervading all Nature would logically involve the transfer of every human attribute to its original source.244 And to say that the Supreme Being, because it surpasses man, must possess an intelligence like his, is no more rational than to make the same assumption with regard to a great city because it is superior to an ant.��245In constructing patterns where it is optional whether to employ cores or not, and in preparing drawings for castings which may have either a ribbed or a cored section, it is nearly always best to employ cores. The usual estimate of the difference between the cost of moulding rib and cored sections, as well as of skeleton and cored patterns, is wrong. The expense of cores is often balanced by the advantage of having an 'open mould,' that is accessible for repairs or facing, and by the greater durability and convenience of the solid patterns. Taking, for example, a column, or box frame for machinery, that might be made either with a rib or a cored section, it would at first thought seem that patterns for a cored casting would cost much more by reason of the core-boxes; but it must be remembered that in most patterns labour is the principal expense, and what is lost in the extra lumber required for a core-box or in making a solid pattern is in many cases more than represented in the greater amount of labour required to construct a rib pattern.

THREE:II.Perseverance is an important trait to be cultivated in first efforts at designing; it takes a certain amount of study to understand any branch of mechanism, no matter what natural capacity may be possessed by a learner. Mechanical operations are not learned intuitively, but are always surrounded by many peculiar conditions which must be learned seriatim, and it is only by an untiring perseverance at one thing that there can be any hope of improving it by new designs. FORE:"Then she will go to some of her earlier haunts on the Continent," said Prout. "They always do. We can count upon that with absolute certainty."As remarked in the case of other machines treated of, there is no use of describing the mechanism of trip-hammers; it is presumed that every engineer apprentice has seen trip-hammers, or can do so; and the plan here is to deal especially with what he cannot see, and would not be likely to learn by casual observation.

THREE: FORE:"I shall not go," Hetty cried. She was surprised at the ease with which she was working herself up into a genuine passion. "Nor shall you pass. You shall stay here as long as I please. Ring the bell and have me put out."Tempering may be called a mystery of the smith-shop; this operation has that attraction which characterises every process that is mysterious, especially such as are connected with, or belong to mechanical manipulation. A strange and perhaps fortunate habit of the mind is to be greatly interested in what is not well understood, and to disregard what is capable of plain demonstration.