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 be investigated they axe introduced into e (between a and b) ; gases are introduced through e or d. (A later construction, in which d is continued into the apparatus and ends near e, is evidently more suitable when gases are used.) The inner and outer layers (sulphuric acid) of this Leyden jar are connected each with one pole of a galvanic battery. After introducing the substance to be investigated, c and d are closed.

Berthelot succeeded in bringing about quite remarkable actions with a potential differ- ence between the two acids of only 8 volts, although a single experiment required several months. The apparatus was afterwards used by others, but much higher potential differences ^"'- ^'■ or high-tension alternating currents were invariably em- ployed.

Electrothermic and Electrochemical Actions. — All the conditions of expeiiment mentioned — except, those applied by Berthrtot, the actions of which have not yet been explained — agree in this respect, that for an exceedingly short time a gas is heated to the glowiug point and then cools. Judging from the spectra of gases glowing under the infiuence of action of points, sparks, or electrical oscillations, the temperature at certain times is much higher than that of the arc light. This is concluded from the fact that the spark spectrum excels the arc spectrum in number of lines and brilliancy just as the arc spectrum excels that obtained with a Bnnsen burner. Of course, quantitative differences exist between the phenomena of the action of points, spark dis- charge, and vibrations in the ether, in so far as the heat effect is concerned, accoi-ding to the greater or smaUer quantity of energy possessed by the discharge ; but all must, as the spectra prove, produce, during a very short time, a higher temperature than the arc light.

At these high temperatures chemical reactions proceed in quite a different direction from that taken at the ordinary

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