a means of transmitting force already perceived as force in some other form (as where a dynamo-electric machine receives motion from a steam-engine or waterfall and turns this motion into electricity, which is conveyed by wires or rails to an electric dynamic engine that reconverts it into motion) and its use as a primary means of utilising the cosmic stores of force. Before we arrive, therefore, at the point of using electricity as a source of power in itself, our mechanicians will have plenty to occupy them in the task of devising safer and more convenient methods of transmitting force, and even at the end of the century, supposing the use of electricity not to have been entirely superseded by the discovery of some entirely new force as yet not even conceivable, invention will doubtless be still busy with further improvements in the transmission as well as in the production of electricity. It has been hinted that "wireless" transmission of power will no doubt by that time have become practicable, and Signor Marconi's achievement of wireless telegraphy was mentioned as a proof that such transmission is at least imaginable. In Marconi's invention an enormous electrical impulse is launched into the æther, and if the very smallest token of it can be "picked up" in any way at the receiving station, the wireless telegram is satisfactorily received. But the important fact for our present purpose is that some product of the original impulse can be picked up: and though the effort of imagination required to see in this a starting-point for entirely new inventions, capable of gathering up a practicable modicum of the transmitted power in a form capable of being converted into motion, is severe, we shall bring but a poor imaginative equipment to a task so colossal as that of guessing what the next century will be capable of if we refuse to believe that something in the nature of Hertzian waves, or something propagated as these are propagated, can be used to carry impulse to machinery at a distance from the source of power. The imaginative faculty which boggles at this effort will probably overlook the fact that the mere transmission is only a part of the difficulty which is pretty sure to have been overcome by this time next century. It will not be enough to launch waves capable of being used where they are intended to be used. We must also discover how to launch them so that they may be incapable of being used anywhere else. I read the other day the report of a police-court case in which a man was charged with "stealing electricity" (which seems a rather doubtful indictment from the point of view of the lawyer) by obtaining the use of a public telephone station without paying the usual fee. The electricians of a hundred years hence will certainly have to find out how to prevent the purloining of wireless force, and perhaps the police will have to devise means of detecting this at present somewhat recondite crime.