APPLICATION OF ELECTRO-MAGNETIC POWER TO RAILWAY TRANSIT. One of the most wonderful characteristics of scientific discovery is the singular way in which every advance connects itself with past phases of progress. Each new victory over the stubborn properties of matter not only gives man increase of power on its own account, but also reacts on older conquests, and makes them more productive. Thirty years ago, Davy and Arago observed that iron-filings became magnetic when lying near a wire that was carrying a current of galvanic electricity. Since then powerful temporary magnets have been made for various purposes by surrounding bars of soft iron by coils of copper-wire, and transmitting electric currents through these. In fact, it has been ascertained that iron always becomes a magnet when electricity is passed round it. The alarm-bells of the electric telegraphs are set ringing by a simple application of this principle. A conducting wire is made to run for hundreds of miles, and then coils itself round an iron bar. Electric currents are sent at will through the hundreds of miles of wire, and the inert iron becomes an active magnet. Observe the clerk in the Telegraph Office at London. When he jerks the handle that is before him, he turns on a stream of electricity that runs to Liverpool or Edinburgh, as the case may be. In either of those places a piece of iron that is twisted round with the extremity of the wire becomes a magnet for an instant, and attracts to itself a steel armature that is connected with a train of wheel-work. The motion of the armature, as it is drawn up to the magnet, sets free a spring that was before kept quiet; and this gives token of its freedom by making an alarm-bell to ring. The clerk in London awakens the attention of the clerk in Edinburgh by turning a piece of soft iron placed near to the latter into a magnet for a few seconds. He is able to do this because currents of electricity induce magnetism in iron. This, and this alone, is the secret principle to which he is indebted for the wonderful power that enables him to annihilate space when he instantaneously attracts the attention of an ear hundreds of miles away.