General physiology; an outline of the science of life . the metals be joined by a wire sothat a closed circuit exists, an electric currentcan be led off from them, the presence ofwhich is shown by the deviation of a mag-netic needle in the vicinity. For the demon-stration of very feeble currents especiallysensitive apparatus is needed, such as themultiplier and the galvanometer, the mag-nets of which are moved by very delicatecurrents. The multiplier consists of a suspended and easilymoved astatic system, , two horizontal magnetic needleswhich are fastened together parallel one above the o
General physiology; an outline of the science of life . the metals be joined by a wire sothat a closed circuit exists, an electric currentcan be led off from them, the presence ofwhich is shown by the deviation of a mag-netic needle in the vicinity. For the demon-stration of very feeble currents especiallysensitive apparatus is needed, such as themultiplier and the galvanometer, the mag-nets of which are moved by very delicatecurrents. The multiplier consists of a suspended and easilymoved astatic system, , two horizontal magnetic needleswhich are fastened together parallel one above the other, so thatthe north pole of the one lies above the south pole of the the region of the lower needle the wire of the circuit is woundinto a coil consisting of an exceedingly large number of turns, sothat when the current goes through it, all the individual turnstend to deviate the needle in the same direction. The upperneedle hangs above a disc divided into degrees, so that here thedeviation of the needle can be measured (Fig. 115). In the. Fjg. 114.—Apparatus fordemonstrating the riseof temperature in thesprouting of peas. Undera bell-jar is a funnel con-taining sprouting peas,into which projects athermometer. .(AfterSachs.) ELEMENTARY VITAL PHENOMENA 259 galvanometer (Fig. 116) the magnet has the form of a ring whichis suspended by a silk fibre in the space within the coil; a smallmirror is connected with the ring and accompanies all the move-ments of the latter (Fig. 116 /3 7). At some distance from theapparatus stands a telescope bearing a scale, the image of whichby careful adjustment can be observed through the telescope inthe mirror of the galvanometer (Fig. 116 7). The slightestdeviation of the ring-magnet is shown in the telescope by ashifting of the image of the scale. According to the extent ofthis shifting the strength of the electric current can be computed,
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Keywords: ., bookcentury1800, bookdecade1890, bookidgen, booksubjectphysiology
