In the long delay attendant upon the application to mechanics of the unknown force which John Ernest Worrell Keely has discovered in the field of vibration, the question is often heard, "What has Keely done?" with the remark, "He has never done anything; he is always promising to do something, but he never keeps his promises." Let us see what Keely, in his researches, has done for science; although, as yet, he has done nothing for commerce. We are quick to forget the experiences of history, which show what a length of time has invariably elapsed between the discovery of a new force and its use in mechanics. Watt commenced his experiments on the elastic force of steam in 1764, obtaining about forty pounds total pressure per square inch. (It has been stated that it was thirty years before he succeeded in perfecting his safety-valve, or governor, which made it possible to use steam without running great risks.) Fifty years later, in 1814, the first steam locomotive was built; but it was not until 1825 that the locomotive was used for traffic--travelling at a speed of from six to eight miles in an hour. Keely commenced his experiments with ether in the winter of 1872-73, showing a pressure of two thousand pounds per square inch. It does not look now as though half a century would elapse before Keely's discovery will supersede steam in travel and traffic. In experimenting with ether, he has shown, from time to time, since 1873, a pressure of from twenty thousand to thirty-two thousand pounds per square inch; but he was occupied many years in his researches before he obtained sufficient control over the ether to prevent the explosions which made wrecks of his machines, bursting iron and steel pipes, twelve inches in circumference, as if they were straws. He has now arrived at a stage in his experimental research in which he can, without danger of explosions, exhibit to scientists such manifestations of an unknown force as to place him before the world where he would have stood many years ago, had it not been for the calumnious attacks of those men of science who found it easier to denounce him than to account for the phenomena which they witnessed in his workshop. Professor Ira Remsen, in his "Theoretical Chemistry," writes, "As regards the cause of the phenomena of the motion of the heavenly bodies, we have no conception at the present day. It is true we say that these phenomena are caused by the attraction of gravitation; but, after all, we do not know what pulls these bodies together." Let us see what Keely knows on this subject?