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

nent and even-working galvanic battery known, and for medi- cal purposes it is invaluable, particularly for the so-called con- stant galvanic current. The arrangement is in large, strong quart glass jars, by using porous diaphragms of pipe-clay cups. Within this porous cup is the solid pound of zinc, say an inch or so in diameter and some four inches long. Then a bit of sheet copper, say four by six inches, is so rolled and bent as to just drop inside the glass jar, and the jar is then packed nearly full of crystals of sulphate of copper. Indeed, it is bet- ter to bruise the sulphate a little in a mortar, so as to work it in without getting it also inside of the pipe-clay cup. The copper is thus buried in the sulphate, and the zinc is placed within the pipe clay ; then the whole is filled to within a half inch or so of the top of the porous cup with water. It is better not to fill the inner cup quite as full of water as the outside of it is, for this will allow the battery to get at work within a few hours. Some thirty to fifty of these cups connected consecutively form a battery sufficiently powerful for any remedial purposes, and yet, if well managed, will so run for a year in good working order without replenishing except with water. In fitting up this battery, I find it very advantageous to place a strip of stout brown paper or oil-cloth about the tops of all the cups, to prevent the capillary attraction in the rc-crystallization of the sulphate driven on by the process, from running over the outside of the glasses. This has caused me a deal of trouble, as, in the course of every few months, we would find great quantities of the cop- per solution crystallized all over and between the glass cups; but by pasting strips of rubber cloth tightly and carefully around the tops of the cups, so as to be some half inch above them, it will stop it; (for these cups are without lips or rims,) and then the paper should be varnished on the outside. This appears to be the most effectual means I can find to pre- vent this dirty and wasteful inconvenience. Some one hundred and seventy cups thus prepared have been running now nearly a year in my office, and they have only been replenished with water every three months; and now they are as clean on the outside as at first, without exception.