[Illustration: FIG. 15.--HARLACHER'S APPARATUS FOR STUDYING DEEP CURRENTS IN RIVERS.]
We have now exhausted the subject of the apparatus of precision that were comprised in the Munich Exhibition. In general, it may be said that this class of instruments was very well represented there as regards numbers, and, on another hand, the manufacturers are to be congratulated for the care bestowed on their construction.--_La Lumiere Electrique_.
[Illustration: FIG. 16.--HARLACHER'S APPARATUS FOR STUDYING DEEP CURRENTS IN RIVERS.]
[Illustration: FIG. 17.--VON BEETZ'S CHRONOGRAPH.]
Dr. Hammerl, of the Vienna Academy of Sciences, has made some experiments upon the disturbing influences on the correct indications of a copper voltameter. He investigated the effects of the intensity of the current, the distance apart of the plates, and their preparation before weighing. The main conclusion which he arrives at is this: That in order that the deposit should be proportional to the intensity of the current, the latter ought not to exceed seven ampères per square decimeter of area of the cathode.
Speaking of steel ropes as transmitters of power, Professor Osborne Reynolds says these have a great advantage over shafts, for the stress on the section will be uniform, the velocity will be uniform, and may be at least ten to fifteen times as great as with shafts--say 100 ft. per second; the rope is carried on friction pulleys, which may be at distances 500 ft. or 600 ft. so that the coefficient of friction will not be more than 0.015, instead of 0.04.
We have succeeded in forming a new battery with a single liquid and with a solid depolarizing element by associating oxide of copper, caustic potash, and zinc.
This battery possesses remarkable properties. Depolarizing electrodes are easily formed of oxide of copper. It is enough to keep it in contact with a plate or a cell of iron or copper constituting the positive pole of the element.
Fig. 1 represents a very simple arrangement. At the bottom of a glass jar, V, we place a box of sheet iron, A, containing oxide of copper, B. To this box is attached a copper wire insulated from the zinc by a piece of India rubber tube. The zinc is formed of a thick wire of this metal coiled in the form of a flat spiral, D, and suspended from a cover, E, which carries a terminal, F, connected with the zinc; an India-rubber tube, G, covers the zinc at the place where it dips into the liquid, to prevent its being eaten away at this level.