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Crescograph, Bose Institute, Kolkata

A crescograph is a device for measuring growth in plants. It was invented in the early 20th century by Sir Jagadish Chandra Bose - a Bengali polymath, physicist, biologist, botanist, archaeologist.

The Bose crescograph uses a series of clockwork gears and a smoked glass plate to record the movement of the tip of a plant (or its roots) at magnifications of up to 10,000. Marks are made on the plate at intervals of a few seconds, demonstrating how the rate of growth varies under varying stimuli. Bose experimented with temperature, chemicals, gases, and electricity.[1]

The Electronic Crescograph plant movement detector is capable of measurements as small as 1/1,000,000 of an inch. However, its normal operating range is from 1/1000 to 1/10,000 of an inch. The component which actually measures the movement is a differential transformer. Its movable core is hinged between two points. A micrometer is used to adjust and calibrate the system. It could record plant growth, magnifying a small movement as much as 10,000,000 times.