THREE:I am well aware of the popular opinion that such subjects are too abstruse to be understood by practical mechanicsan assumption that is founded mainly in the fact that the subject of heat and motion are not generally studied, and have been too recently demonstrated in a scientific way to command confidence and attention; but the subject is really no more difficult to understand in an elementary sense than that of the relation between movement and force illustrated in the "mechanical powers" of school-books, which no apprentice ever did or ever will understand, except by first studying the principles of force and motion, independent of mechanical agents, such as screws, levers, wedges, and so on.
你最喜欢的艺术作品，告诉大家它们的------名图画，色彩，交织，撞色，线条雕塑装置当代古代现代作品的照片美我最喜欢的画群296795413进群发画，少说多发图，
荣誉榜
THREE:Considered as a mechanical agent, a hammer concentrates the power of the arms, and applies it in a manner that meets the requirements of various purposes. If great force is required, a long swing and slow blows accomplish tons; if but little force is required, a short swing and rapid blows will servethe degree of force being not only continually at control, but also the direction in which it is applied. Other mechanism, if employed instead of hammers to perform a similar purpose, would require to be complicated [104] machines, and act in but one direction or in one plane."But it is not in the least beyond me," Lawrence remarked coolly, as he reached for a cigarette. "To a certain extent I hold the key to the situation. Accident strengthens my hands, as it generally does in dealing with people of this kind. And I am going to make a powerful new ally in this new business. I need not ask you if you are personally acquainted with Maitrank, Isidore?"
THREE:In operating by elastic blows, the steam piston is cushioned at both the up and down stroke, and the action of a steam-hammer corresponds to that of a helve trip-hammer, the steam filling the office of a vibrating spring; in this case a hammer gives a quick rebounding blow, the momentum being only in part [111] spent upon the work, and partly arrested by cushioning on the steam in the bottom of the cylinder under the piston.
