Page:Life Movements in Plants.djvu/186

156 conditions that the disturbing effect of after-vibration of the lever could be obviated.

This particular contrivance consists of an eccentric rod actuated by a rotating wheel. A cylindrical rod is sup- ported, eccentrically, so that semi-rotation of the eccentric causing a pull on the crank K (Fig. 57) pushes the plate

Flti. 57. — Eccentric for oscillation ot plate. K, crank ; S, slide ; P, holder for glass plate G. A, adjusting screws; L, recording lever. Clock releases string C tor lateral movement of the plate. (From a photograph.)

carrier gradually forward. On the return movement of the eccentric, a light antagonistic spring makes the plate recede. The rate of the movement, of the crank itself is further regulated by the device of the revolving wheel. This is released periotUcally by clockwork at intervals of one, two, five, ten, or fifteen seconds respectively, according