LITMIR.BIZ

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      OK Publishing, 2020

       [email protected] Tous droits réservés.

      EAN 4064066396589

Table of Contents

       PREFACE.

       LECTURE I. THE FORCE OF GRAVITATION.

       LECTURE II. GRAVITATION—COHESION.

       LECTURE III. COHESION—CHEMICAL AFFINITY.

       LECTURE IV. CHEMICAL AFFINITY—HEAT.

       LECTURE V. MAGNETISM—ELECTRICITY.

       LECTURE VI. THE CORRELATION OF THE PHYSICAL FORCES.

       LECTURE ON LIGHT-HOUSE ILLUMINATION—THE ELECTRIC LIGHT.

       NOTES.

PREFACE.

       Table of Contents

      Which was first, Matter or Force? If we think on this question, we shall find that we are unable to conceive of matter without force, or of force without matter. When God created the elements of which the earth is composed, He created certain wondrous forces, which are set free, and become evident when matter acts on matter. All these forces, with many differences, have much in common, and if one is set free, it will immediately endeavour to free its companions. Thus, heat will enable us to eliminate light, electricity, magnetism, and chemical action; chemical action will educe light, electricity, and heat. In this way we find that all the forces in nature tend to form mutually dependent systems; and as the motion of one star affects another, so force in action liberates and renders evident forces previously tranquil.

      We say tranquil, and yet the word is almost without meaning in the Cosmos.—Where do we find tranquillity? The sea, the seat of animal, vegetable, and mineral changes, is at war with the earth, and the air lends itself to the strife. The globe, the scene of perpetual intestine change, is, as a mass, acting on, and acted on, by the other planets of our system, and the very system itself is changing its place in space, under the influence of a known force springing from an unknown centre.

      For many years the English public had the privilege of listening to the discourses and speculations of Professor Faraday, at the Royal Institution, on Matter and Forces; and it is not too much to say that no lecturer on Physical Science, since the time of Sir Humphrey Davy, was ever listened to with more delight. The pleasure which all derived from the expositions of Faraday was of a somewhat different kind from that produced by any other philosopher whose lectures we have attended. It was partially derived from his extreme dexterity as an operator: with him we had no chance of apologies for an unsuccessful experiment—no hanging fire in the midst of a series of brilliant demonstrations, producing that depressing tendency akin to the pain felt by an audience at a false note from a vocalist. All was a sparkling stream of eloquence and experimental illustration. We would have defied a chemist loving his science, no matter how often he might himself have repeated an experiment, to feel uninterested when seeing it done by Faraday.

      The present publication presents one or two points of interest. In the first place, the Lectures were especially intended for young persons, and are therefore as free as possible from technicalities; and in the second place, they are printed as they were spoken, verbatim et literatim. A careful and skilful reporter took them down; and the manuscript, as deciphered from his notes, was subsequently most carefully corrected by the Editor as regards any scientific points which were not clear to the short-hand writer; hence all that is different arises solely from the impossibility, alas! of conveying the manner as well as the matter of the Lecturer.

      May the readers of these Lectures derive one-tenth of the pleasure and instruction from their perusal which they gave to those who had the happiness of hearing them!

      W. CROOKES.

      THE

       VARIOUS FORCES OF NATURE.

LECTURE I.

       THE FORCE OF GRAVITATION.

       Table of Contents

      It grieves me much to think that I may have been a cause of disturbance in your Christmas arrangements1, for nothing is more satisfactory to my mind than to perform what I undertake; but such things are not always left in our own power, and we must submit to circumstances as they are appointed. I will to-day do my best, and will ask you to bear with me if I am unable to give more than a few words; and as a substitute, I will endeavour to make the illustrations of the sense I try to express as full as possible; and if we find by the end of this lecture that we may be justified in continuing them, thinking that next week our power shall be greater—why, then, with submission to you, we will take such course as you may think fit—either to go on, or discontinue them; and although I now feel much weakened by the pressure of illness (a mere cold) upon me, both in facility of expression and clearness of thought, I shall here claim, as I always have done on these occasions, the right of addressing myself to the younger members of the audience. And for this purpose, therefore, unfitted as it may seem for an elderly infirm man to do so, I will return to second childhood and become, as it were, young again amongst the young.

      Let us now consider, for a little while, how wonderfully we stand upon this world. Here it is we are born, bred, and live, and yet we view these things with an almost entire absence of wonder to ourselves respecting the way in which all this happens. So small, indeed, is our wonder, that we are never taken by surprise; and I do think that, to a young person of ten, fifteen, or twenty years of age, perhaps the first sight of a cataract or a mountain would occasion him more surprise than he had ever felt concerning the means of his own existence—how he came here; how he lives; by what means he stands upright; and through what means he moves about from place to place. Hence, we come into this world, we live, and depart from it, without our thoughts being called specifically to consider how all this takes place; and were it not for the exertions of some few inquiring minds, who have looked into these things and ascertained the very beautiful laws and conditions by which we do live and stand upon the earth, we should hardly be aware that there was anything wonderful in it. These inquiries, which have occupied philosophers from the earliest days, when they first began to find out the laws by which we grow, and exist, and enjoy ourselves, up to the present time, have shewn us that all this was effected in consequence of the existence of certain forces, or abilities to do things, or powers, that are so common that nothing can be more so; for nothing is commoner than the wonderful powers by which we are enabled to stand upright—they are essential to our existence every moment.

      It is my purpose to-day to make you acquainted with some of these powers; not the vital ones, but some of the more elementary,

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