TWO:Artistic drawing is addressed to the senses, geometrical drawing is addressed to the understanding. Geometrical drawing may, however, include artistic skill not in the way of ornamentation, but to convey an impression of neatness and completeness, that has by common custom been assumed among engineers, and which conveys to the mind an idea of competent construction in the drawing itself, as well as of the machinery which is represented. Artistic effect, so far as admissible in mechanical drawing, is easy to learn, and should be understood, yet through a desire to make pictures, a beginner is often led to neglect that which is more important in the way of accuracy and arrangement.No computations, drawings, or demonstrations of any kind will be employed to relieve the mind of the reader from the care of remembering and a dependence on his own exertions. Drawings, constants, formul?, tables, rules, with all that pertains to computation in mechanics, are already furnished in many excellent books, which leave nothing to be added, and such books can be studied at the same time with what is presented here.
THREE:"Ay, I should. I should have put you from my path. Make no mistake about that. But it is no use repining over that. Go on."Among the systems of ancient philosophy, Epicureanism is remarkable for the completeness with which its doctrines were worked out by their first author, and for the fidelity with which they were handed down to the latest generation of his disciples. For a period of more than five hundred years, nothing was added to, and nothing was taken away from, the original teaching of Epicurus. In this, as in other respects, it offers a striking contrast to the system which we last reviewed. In our sketch of the Stoic philosophy, we had to notice the continual process of development through which it passed, from its commencement to its close. There is a marked difference between the earlier and the later heads of the school at Athensbetween these, as a class, and the Stoics of the Roman empireand, finally, even between two Stoics who stood so near to one another as Epicttus and Marcus Aurelius. This contrast cannot be due to external circumstances, for the two systems were exactly coeval, and were exposed, during their whole lifetime, to the action of precisely the same environment. The cause must be sought for in the character of the philosophies themselves, and of the minds which were naturally most amenable to their respective influence. Stoicism retained enough of the Socratic spirit to foster a love of enquiry for its own sake, and an indisposition to accept any authority without a searching examination of its claims to obedience or respect. The learner was submitted54 to a thorough training in dialectics; while the ideal of life set before him was not a state of rest, but of intense and unremitting toil. Whatever particular conclusions he might carry away with him from the class-room were insignificant in comparison with the principle that he must be prepared to demonstrate them for himself with that self-assurance happily likened by Zeno to the feeling experienced when the clenched fist is held within the grasp of the other hand. Epicurus, on the contrary, did not encourage independent thought among his disciples; nor, with one exception hereafter to be noticed, did his teaching ever attract any very original or powerful intellect. From the first a standard of orthodoxy was erected; and, to facilitate their retention, the leading tenets of the school were drawn up in a series of articles which its adherents were advised to learn by heart. Hence, as Mr. Wallace observes,108 while the other chief sects among which philosophy was dividedthe Academicians, the Peripatetics, and the Stoicsdrew their appellation, not from their first founder, but from the locality where his lectures had been delivered, the Epicureans alone continued to bear the name of a master whom they regarded with religious veneration. Hence, also, we must add with Zeller,109 and notwithstanding the doubt expressed by Mr. Wallace,110 on the subject, that our acquaintance with the system so faithfully adhered to may be regarded as exceptionally full and accurate. The excerpts from Epicurus himself, preserved by Diogenes Laertius, the poem of Lucretius, the criticisms of Cicero, Plutarch, and others, and the fragments of Epicurean literature recovered from the Herculanean papyri, agree so well where they cover the same ground, that they may be fairly trusted to supplement each others deficiencies; and a further confirmation, if any was needed, is obtained by consulting the older sources, whence Epicurus borrowed most of his philosophy.
TWO:These are but a few of many influences which tend to irregular cooling, and are described with a view of giving a clue from which other causes may be traced out. The want of uniformity in sections which tends to irregular cooling can often be avoided without much loss by a disposition of the metal with reference to cooling strains. This, so far as the extra metal required to give uniformity to or to balance the different sides of a casting, is a waste which engineers are sometimes loth to consent to, and often neglect in designs for moulded parts; yet, as before said, the difficulty of irregular cooling can in a great degree be counteracted by a proper distribution of the metal, without wasting, if the matter is properly understood. No one is prepared to make designs for castings who has not studied the subject of cooling strains as thoroughly as possible, from practical examples as well as by theoretical deductions.
