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352 or depressing nature of an agent on growth. The desideratum is to compensate the up-movement of growth by some regulating device, by which the plant is made to descend exactly at the same rate at which the growing tip of the plant was rising, whatever that rate may be. The special difficulty encountered was in obtaining exact balance for widely varying rates of growth in different plants, and even in the same plant under different conditions. In the Balanced Crescograph, (fig. 111) a train of revolving clockwork actuated

by the fall of a weight, lowers the plant at the same rate at which it is growing. The exact adjustment is obtained by the gradual turning of a screw to the right or to the