Galvanometer throws. Galvanometer throws. 1st closing 1° 1st opening 18° 2nd ” 64° 2nd ” 100° 3rd ” 146° 3rd ” 140° _Effects of Passing Continuous Currents of High E.M.F._--If a continuous current of high E.M.F. is employed, it renders a sensitive substance conducting. The phenomenon may be shown in the following manner. A circuit is made up consisting of a battery, a sensitive substance, and a galvanometer. The E.M.F. of the battery is first one volt, then 100 volts, then one volt. Below I give the galvanometer deflections obtained with an E.M.F. of one volt for three different substances before and after the application of the E.M.F. of 100 volts:-- Before application of current. After application of current. 16 100 0 15 1 500 In the case of some measurements taken on a Wheatstone bridge a prism of aluminium filings interposed between two copper electrodes offered a resistance of several million ohms before a high E.M.F. was applied, but only offered a resistance of 350 ohms after the application of this pressure for one minute. The time during which the powder should be interposed in the battery circuit should not be too short. Thus, in one instance, the application for 10 sec. of 75 mercury sulphate cells produced no effect, but their application for 60 sec. resulted in the resistance being reduced from several megohms to 2,500 ohms. It should be observed that the phenomenon of suddenly increased conductivity occurs, even if the sensitive substance is not in circuit with a battery at the time it is influenced. Thus, the metallic filings, after having been placed in circuit with a Daniell cell, and its high resistance observed, may then be completely insulated and submitted in this condition to the action of a distant spark, or of a charged rod, or of induced currents. If, after this, the filings are replaced in their original circuit, the enormous increase in their conductivity is immediately apparent.