Page:Scientific Memoirs, Vol. 1 (1837).djvu/515



great discovery of M. Oersted, which has so much extended the limits of physical science, promises to open a new career to practical mechanics. The motive powers which have hitherto served for the movement of machines are not, properly speaking, forces; they are only masses animated by forces. These masses are made to act upon the point of application of a machine, and they consequently can only give it a velocity conformable to their own moving principle. But magnetism enables us to employ immediately a force; the point of application is the force itself. We thus perceive a considerable active force produced without any external influence. The interest of such a phænomenon is increased extremely by the simplicity of the apparatus and by the facility of conceiving its mode of action. But on examining it more closely, we find that the forces which are active in producing the movement present a great complication of circumstances. The study of the phænomena of electricity and magnetism is still in its infancy; and we are not surprised that every day makes us acquainted with new phænomena at once striking and unsuspected. The views which I had conceived of these forces have in part been confirmed during the course of my researches, and they have in part been shaken and even completely changed; as soon, however, as I was obliged to abandon one view, another presented itself which led to the disclosure of fruitful results. For example, the remarkable reaction which prevents the movement from becoming accelerated to infinity has become a new source of power; the exact knowledge of the galvanic action leads to a minimum of the expense attending its maintenance. I have restricted myself in my researches to such experiments as touch immediately upon the object itself; and from the number of these, I shall only publish those which have given results, or at least lead us to hope for them: I have suppressed as much as possible all purely theoretical considerations. As to the practical application, it appears to me decided by my experiments; to go further will be only to augment an effect, with which, laying aside sanguine expectations, we may already be content. It is no unusual thing to have electro-magnets which lift 2000lbs.; mine carried