Mechanics

“ Many of our illustrations will be designedly drawn from very commonplace sources: by this means I would try to impress upon you that mechanics is not a science that exists in books merely, but that it is a study of those principles which are constantly in action about us. Our own bodies, our houses, our vehicles, all the implements and tools which are in daily use—in fact all objects, natural and artificial, contain illustrations of mechanical principles. ”

“ Mechanics went on inventing "perpetual motions," but, however plausible they looked, somehow or other they wouldn't work. Do away with friction to the greatest possible extent; overcome one obstacle here and another there; increase the time the machine would run indefinitely—still, to a state of equilibrium would it come at last. From these empirical observations mechanics learned, what philosophers might have learned years ago, that experience affords the only sure test of the validity of our notions. ”

“ The sciences we have been considering under the general name of mechanics, which is derived from a Greek word that means to contrive, invent, construct, have much to do with machinery, with the methods of construction, the propelling forces, and the phenomena produced. There were machinists and some simple machines propelled by human or brute force, by weights and springs, by falling or running water, and air in motion before the laws of motion and forces were understood, or the rude mechanic arts began to assume the character of a science. ”

“ Mechanics are still living who firmly believe in the possibility of realizing a mechanical perpetual motion,—to spin, pump, or drive carriages or machinery, by means of a constantly descending weight. ”

“ If the beautiful and skilful structures of the middle ages prove that mechanics then existed as a science, mechanics must have existed as a science also among the builders of the Cyclopean walls of Greece and Italy, or of our own Stonehenge; for the masses which are there piled on each other, could not be raised without considerable mechanical skill. ”

“ If we accept this account of mechanics, we are at once puzzled by the fact that most mechanical theories make assumptions about the forces at work in the world, and that all of them predict coming facts. But forces form no part of the experience or of the mere description of motion. ”

“ Sequel to the Generalization of the Principles of Mechanics.—Period of Mathematical Deduction.—Analytical Mechanics. WE have now finished the history of the discovery of Mechanical Principles, strictly so called. The three Laws of Motion, generalized in the manner we have described, contain the materials of the whole structure of Mechanics; and in the remaining progress of the science, we are led to no new truth which was not implicitly involved in those previously known. ”

“ And in order that the student may possess this idea in a precise and manifest shape, he must pursue the science of Mechanics in the mode which this view of its nature demands;—that is, he must study it as an independent science, resting on solid elementary principles of its own, and not built upon some other unmechanical science as its substructure. He must trace the truths of Mechanics from their own axioms and definitions; these axioms and definitions being considered as merely means of bringing into play the Idea on which the science depends. ”

“ Such a science is the science of Mechanism, independent of force, and considered as the solution of a problem which may be thus enunciated: ‘To communicate any given motion from a first mover to a given body.’ The science which should have for its object to solve all the various cases into which this problem would ramify, might be termed Pure Mechanism, in contradistinction to Mechanics Proper, or Machinery, in which Force is taken into consideration. ”

“ The mechanical formulas of science are admirably adapted to the purpose for which they were designed, that is, the handling of matter, but they are misleading as applied to living beings, and especially to the human mind, which is the farthest removed from the realm of material mechanics. ”

“ Few mechanics have any distinct knowledge of the method to be pursued for obtaining it, nor do practical men sufficiently advert, either to the immense importance, or to the comparative facility of the acquisition. ”

“ The ancients considered Mechanics in a twofold respect; as rational, which proceeds accurately by demonstration, and practical. To practical Mechanics all the manual arts belong, from which Mechanics took its name. But as artificers do not work with perfect accuracy, it comes to pass that Mechanics is so distinguished from Geometry, that what is perfectly accurate is called Geometrical, what is less so is called Mechanical. But the errors are not in the art, but in the artificers. ”

“ Yet in mechanics, whatever the mechanicians might think, both energies acted as interchangeable forces on man, and by action on man all known force may be measured. Indeed, few men of science measured force in any other way. ”

“ And the same is the case in the more recent progress of that subject, in the hands of Gauss, Bessel, Hansen, and others.
But yet the science of Mechanics as applied to terrestrial machines—Industrial Mechanics, as it has been termed—has made some steps which it may be worth while to notice, even in a general history of science. ”

“ Your work on 'Applied Mechanics' is a great illustration of your power to grasp, to connect, and to apply the definite principles of exact science with the less definite known elements of practical problems. Abstract principles are valueless, except in application to the wants of man, and this work occupies that field with great eminence. Your work on the 'Steam Engine and other Prime Movers' deals with the principles involved in that important subject in a masterly manner, that renders comparison with any other similar work impossible. ”

“ That this bet would have been a perfectly safe one must be quite evident to any person who has the slightest knowledge of practical mechanics, and yet the fundamental idea which is embodied in this and the other examples which we have just given, forms the basis of almost all the attempts which have been made to produce a perpetual motion by purely mechanical means. ”

“ Statics and Dynamics.—We must first turn our attention to a technical distinction of Mechanics into two portions, according as the forces about which we reason produce rest, or motion; the former portion is termed Statics, the latter Dynamics. If a stone fall, or a weight put a machine in motion, the problem belongs to Dynamics; but if the stone rest upon the ground, or a weight be merely supported by a machine, without being raised higher, the question is one of Statics.
3. Equilibrium.—In Statics, forces balance each other, or keep each other in equilibrium. ”

“ Those interested in mechanics will discover for themselves the mechanical defects and unnecessary complications introduced into them. I was working under the supervision of fairly good mechanical engineers, so that defects might not be made too glaring. ”

“ There is no harm done, for example, in directing attention to mechanical actions, such as that of gravity, the lever, &c., even in departments, notably in physics and in physiology, beyond the range of mechanics proper. ”

“ All arts and manufactures are derived from science. Thus the doctrine of mechanics is an application of the law of gravitation. Every thing we are capable of doing by [Pg 3] means of the steam-engine is derived from our knowledge of the properties of water in steam; all the great effects of gunpowder we owe to our knowledge of the composition, and chemical properties, of that substance. ”

“ Practical Mechanics is, in the most pre-eminent sense, a scientific art; and it may be truly asserted, that almost all the great combinations of modern mechanism, and many of its refinements and nicer improvements, are creations of pure intellect, grounding its exertion upon a moderate number of very elementary propositions in theoretical mechanics and geometry. ”

“ It might be difficult to point out the deficiency of this reasoning; but those acquainted with the true principles of mechanics will not hesitate to bet a hundred to one, that the machine, when constructed, will not answer the intended purpose. ”

“ Immediately, mechanics ceased to be a separate science and became an organ for attacking nature. The mechanics of the lever, wheel, pulley and inclined plane told accurately what happens when things in space are used to move one another during definite periods of time. ”

“ His driving-wheel, the heart, acts in response to some stimulus as truly as does the piston of the engine, and the principles involved in circulation are all mechanical; and yet the main thing is not mechanical, but vital. Analyze the vital activities into principles of mechanics and of chemistry, if you will, yet there is something involved that is neither mechanical nor chemical, though it may be that only the imagination can grasp it. ”

“ The knowledge so required as a general and commonplace equipment requisite for the pursuit of these modern skilled occupations is of the general nature of applied mechanics, in which the essence of the undertaking is a ready apprehension of opaque facts, in passably exact quantitative terms. ”

“ The influence of theory on practical development is much greater than is usually supposed and conceded. The discovery and settlement of the laws of mechanics had to precede their application to engines, railways, steamboats, and so on. ”

“ The influence which forces have upon the form, state, arrangement, and motions of material substances is the principal object of physical science. In its strict sense, Mechanics is a term of very extensive signification. According to the more popular usage, however, it has been generally applied to that part of physical science which includes the investigation of the phenomena of motion and rest, pressure and other effects developed by the mutual action of solid masses. ”

“ Nor do we maintain that the application and development of principles is a matter of so much importance to the philosophy of science, as the advance towards and to them. Still, there are many circumstances in the latter stages of the progress of the science of Mechanics, which well deserve notice, and make a rapid survey of that part of its history indispensable to our purpose. ”

“ As, however, the actual machinery itself, deriving its existence from various sources, and having its own characteristic features and methods of classification and treatment, forms a quite distinct and special subject, a separation of its scientific mechanical problems from those of Mechanics in general is possible, and indeed has already been made. ”

“ I then told them that God, to compensate for the weakness of man, had bestowed on him reason, invention, and skill in workmanship. The result of these had produced a science which, under the name of Mechanics, taught us to increase and extend our limited powers incredibly by the aid of instruments. ”

“ To investigate the powers of Nature is the object of rational mechanics, while active mechanics is solely confined to a combination of particular powers, and consequently the art of constructing machines. ”

“ We do not mean, therefore, to undervalue either the application of strict demonstration to problems in mechanics, or the exhibition of the most accurate machinery in philosophical lectures; but we wish to point out a method of giving a general notion of the mechanical organs to our pupils, which shall be immediately obvious to their comprehension, and which may serve as a sure foundation for future improvement. We are told by a vulgar proverb, that though we believe what we see, we have yet a higher belief in what we feel. This adage is particularly applicable to mechanics. ”

“ The field of pure or classical mechanics is limited to the above two kinds of energy, work and kinetic energy, though these do not exhaust the manifoldness of the mechanical energies. Accordingly, other branches of mechanics dealing with the corresponding phenomena are added to the classical mechanics described above. ”

“ If he goes further and analyzes the reasons for this impression of power, he will see that it is not merely a mental suggestion, but a realization of the actual existence of tremendous mechanical power, under complete direction and control.
In mechanics we get a definition of power, which, like all definitions in mechanics, is clear, definite, and correct. ”

“ Mechanics deals with the laws of energy and motion, physics with molecular changes of matter, but neither physics nor mechanics would have gone far, had they stopped to answer the questions as to what motion, energy, matter are in themselves. ”

“ On the subject of the second law a great deal more has to be said before it can be in any proper sense even partially appreciated, but a complete discussion of it would involve a treatise on mechanics. It is the law of mechanics. ”

“ These teachers will find nothing more important, in teaching elementary mechanics to their scholars, than to inform them that this mechanics has had its day, that a new mechanics where the notions of mass and of time have a wholly different value replaces it ”

“ And these men had developed a high civilization, a civilization different from ours, in that they learned early about mechanics, but chemistry and physics merely developed from the needs of the great mechanical engineers. ”

“ There is no subject of such importance as Mechanics, as its principles are founded upon the properties of matter and the laws of motion; and in knowing something of these, the tyro will lay the foundation of all substantial knowledge. ”