Professor A. Graham Bell, the inventor of the telephone, read a paper giving a possible method of communication between ships at sea.  The simple experiment that illustrates the method which he proposed is as follows:  Take a basin of water, introduce into it, at two widely separated points, the two terminals of a battery circuit which contains an interrupter, making and breaking the circuit very rapidly.  Now at two other points touch the water with the terminals of a circuit containing a telephone.  A sound will be heard, except when the two telephone terminals touch the water at points where the potential is the same.  In this way the equipotential lines can easily be picked out.  Now to apply this to the case of a ship at sea:  Suppose one ship to be provided with a dynamo machine generating a powerful current, and let one terminal enter the water at the prow of the ship, and the other to be carefully insulated, except at its end, and be trailed behind the ship, making connection with the sea at a considerable distance from the vessel; and suppose the current be rapidly made and broken by an interrupter; then the observer on a second vessel provided with similar terminal conductors to the first, but having a telephone instead of a dynamo, will be able to detect the presence of the other vessel even at a considerable distance; and by suitable modifications the direction of the other vessel may be found.  This conception Professor Bell has actually tried on the Potomac River with two small boats, and found that at a mile and a quarter, the furthest distance experimented upon, the sound due to the action of the interrupter in one boat was distinctly audible in the other.  The experiment did not succeed quite so well in salt water.  Professor Trowbridge then mentioned a method which he had suggested some years ago for telegraphing across the ocean without a cable, the method having been suggested more for its interest than with any idea of its ever being put in practice.  A conductor is supposed to be laid from Labrador to Patagonia, ending in the ocean at those points, and passing through New York, where a dynamo machine is supposed to be included in the circuit.  In Europe a line is to extend from the north of Scotland to the south of Spain, making connections with the ocean at those points, and in this circuit is to be included a telephone.  Then any change in the strength of the current in the American line would produce a corresponding change in current in the European line; and thus signals could be transmitted.  Mr. Preece, of the English postal telegraph, then gave an account of how such a system had actually been put into practice in telegraphing between the Isle of Wight and Southampton during a suspension in the action of the regular cable communication.  The instruments used were a telephone in one circuit, and in the other about twenty-five Leclanche cells and an interrupter.  The sound could then be heard distinctly; and so communication