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. * * * * * A NEW OXIDE OF COPPER BATTERY. By MM. F. DE LALANDE and G. CHAPERON. 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. The jar is filled with a solution containing 30 or 40 per cent. of potash. This arrangement is similar to that of a Callaud element, with this difference--that the depolarizing element is solid and insoluble. [Illustration: FIG. 1.] To prevent the inconveniences of the manipulation of the potash, we inclose a quantity of this substance in the solid state necessary for an element in the box which receives the oxide of copper, and furnish it with a cover supported by a ring of caoutchouc. It suffices then for working the battery to open the box of potash, to place it at the bottom of the jar, and to add water to dissolve the potash; we then pour in the copper oxide inclosed in a bag. We also form the oxide of copper very conveniently into blocks. Among the various means which might be employed, we prefer the following: We mix with the oxide of copper oxychloride of magnesium in the form of paste so as to convert the whole into a thick mass, which we introduce into metal boxes. The mass sets in a short time, or very rapidly by the action of heat, and gives porous blocks of a solidity increasing with the quantity of cement employed (5 to 10 per cent.). [Illustration: FIG. 2.]