Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

that the decomposition that is brought about is the same as in Becquerel's. The next improvement made in the galvanic battery was by Grove ; and his is one of the most powerful that has ever been constructed. In this battery a small plate of platinum takes the place of the copper, and a strong solution of nitric acid is used in the place of the solution of sulphate of copper. The amalgamated zinc is plunged into a strong solution of sulphuric acid, which is contained within the inner cup of unglazed or porous porcelain. The zinc is amalgamated, or covered with a coat of mercury, by dipping it into a vessel containing a strong solution of sulphuric acid with quicksilver, or by pouring these on the plate, and then brushing it with a tooth brush until amalgamated. Thus the surface of the zinc is cleared by the acid, when the mercury will readily adhere and coat it. In this arranged battery, the nitric acid has the double advantage of containing much oxygen, which first increases the intensity of the current; and second, being a better conductor than the so- lution of sulphate of copper, it transmits the current through the batteries more readily. Here the hydrogen is not developed upon the platinum, but changes the nitric acid into nitrous acid, and the liquid therefore becomes of a brown color, and then soon passes into a green color, while the surface of the platinum always remains the same — that is, clean. The zinc is oxidized, and sulphate of zinc is found in solution. But after a certain time, this furious battery is fairly self-arrested by the fur- ther changes which are going on so rapidly in the nitric acid, re- sulting from the development of hydrogen and heat, until the acid actually enters into ebullition at last, and like the back water of the flooded milldam stops action because there is so much action. In this stage, it is absolutely necessary to stop the action imme- diately ; i. e., to take it apart in order to save the battery. Banseiis battery is another powerful apparatus for particular purposes, and this differs but little from Grove's, only as carbon is substituted for platinum. It was formerly found that plat- inum was more negative than copper, that is, still less attacked by the liquid; so is carbon still more negative than even plat-