ONE:The race was out of their hands.It may be noticed that the carriages of some lathes move on what are termed V tracks which project above the top of lathe frames, and that in other lathes the carriages slide on top of the frames with a flat bearing. As these two plans of mounting lathe carriages have led to considerable discussion on the part of engineers, and as its consideration may suggest a plan of analysing other problems of a similar nature, I will notice some of the conditions existing in the two cases, calling the different arrangements by the names of flat shears and track shears.
THREE:It was at this juncture that the voluntary withdrawal of an older fellow-pupil placed Arcesilaus at the head of the Academy. The date of his accession is not given, but we are told that he died 241 or 240 B.C. in the seventy-fifth year of his age. He must, therefore, have flourished a generation later than Zeno and Epicurus. Accomplished, witty, and generous, his life is described by some as considerably less austere than that of the excellent nonentities whom he succeeded. Yet its general goodness was testified to by no less an authority than his contemporary, the noble Stoic, Cleanthes. Do not blame Arcesilaus, exclaimed the latter146 to an unfriendly critic; if he denies duty in his words, he affirms it in his deeds. You dont flatter me, observed Arcesilaus. It is flattering you, rejoined Cleanthes, to say that your actions belie your words.230 It might be inferred from this anecdote that the scepticism of the new teacher, like that of Carneades after him, was occasionally exercised on moral distinctions, which, as then defined and deduced, were assuredly open to very serious criticism. Even so, in following the conventional standard of the age, he would have been acting in perfect consistency with the principles of his school. But, as a matter of fact, his attacks seem to have been exclusively aimed at the Stoic criterion of certainty. We have touched on this difficult subject in a former chapter, but the present seems a more favourable opportunity for setting it forth in proper detail.
THREE:Most of the difficulties which formerly pertained to drilling are now removed by machine-made drills which are manufactured and sold as an article of trade. Such drills do not require dressing and tempering or fitting to size after they are in use, make true holes, are more rigid than common solid shank drills, and will drill to a considerable depth without clogging.
THREE:
