TION OF ELECTItIC CURRENTS, it only does so at the moment the current is interrupted or broken. It is consequently necessary to have somc means of completing and break Mg the galvanic circuit in rapid alternations, so as to produce the flashes in quick suc cession. The break for this purpose is placed at I, near the battery.
In the experiments now described a great deal was found to depend upon the pecu liar way the current was broken. None of the breaks in use giving a successful result, Mr. Ilart devised a new one of an ingenious construction, which produced a more con• stant and powerful light. The difference between it and other mercury or spring breaks lies in the fact that with them the current is off and on for nearly equal spaces of time; but this one is so contrived that the %vire is three times longer in the mercury than it is out of it; consequently, the enrrent is three times longer on than it is off, and so allows the soft iron core of the induction coil to be more fully magnetized, The result of this 'is a secondary current of comparatively high intensity, and of course the production of more brilliant sparks between its two terminals. We may explain that the moment, the
wire touches the mercury the current passes, and the moment it is removed the current -stops. The Wire alternately dips and rises by the action of an ordinary electro-magnet.
By the use of more thEin one induction coil the light could be materially increased, so that there seemed a likelihood of being able to produce it powerful enough to be seen at the distance of a few miles. Another method of lighting buoys as well as beacons without the aid of electricity has lately been shown to be practicable. Coal or other inflammable gas can be so compressed that Et buoy may be made to receive at once and store up as much condensed gas as will suffice to keep a steady flame burning for a month or more. Gas for this purpose can be economically manufactured from some of the waste products of shale-oil works. Mr. Stevenson has also suggested the employ anent of electricity to ring bells, so as to give warning to sailors in foggy weather.