Science . uring short intervals of time, thegraphic spark apparatus is the most accurateand the pendulum apparatus the most con-venient. In the ehronoscope that is shown inthe accompanying figure, the spark method ofrecording is combined with the pendulumaction. The cut is reduced to a scale one sixth ofthe size of the apparatus. The pendulum isshovm in the starting position. The lower bobterminates in a knife edge which rests uponthe projecting edge of a mechanical releasekey. The action of this key is soundless andgives the pendulum no impetus in either direc-tion. On the other side of the a
Science . uring short intervals of time, thegraphic spark apparatus is the most accurateand the pendulum apparatus the most con-venient. In the ehronoscope that is shown inthe accompanying figure, the spark method ofrecording is combined with the pendulumaction. The cut is reduced to a scale one sixth ofthe size of the apparatus. The pendulum isshovm in the starting position. The lower bobterminates in a knife edge which rests uponthe projecting edge of a mechanical releasekey. The action of this key is soundless andgives the pendulum no impetus in either direc-tion. On the other side of the apparatus is aspring key which catches the pendulum at the • Cf. Flora, 1893; observations on the g^o^vthof the roots of Tradescantia, in my article on the Physiological Functions of Lime and Magnesiai. OCTOBEB 18, 1907] SCIENCE 513 end of the swing. When the pendulum is re-leased from this, it swings back with littleassistance to the starting point and makes allnecessary adjustments automatically. On the. back of the lower bob is an index point whichruns at the upper edge of the scale and servesas a spark point. The record is made upon a smoked paperwhich is seen through the slit above the paper is stretched upon two rollers; italso rests upon an insulated metal plate whichserves as an electrode and keeps the paperstraight and smooth back of the scale. Backof this plate is a third roller by means ofwhich the tension of the paper may be ad-justed. The paper support is built on acarriage so that it may be removed and re-placed without disturbing the rest of the ap-paratus. In preparing the paper this carriageis removed and the paper is smoked as on anordinary kymograph drum. As a completerecord consists in a single spark which maybe recorded at once, several hundred recordsmay be made with one preparation of thepaper. The paper is moved, as needed, by athumb screw at one end of the upper roller. In reaction experiments the stimulus is given automatically by the appar
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