What is a crescograph?

A crescograph is a device for measuring the growth in plants. It was invented in the early 20th century by Sir Jagdish Chandra Bose. The Bose crescograph uses a series of clockwork gears and a smoked glass plate to record the movement of the top of a plant (or its roots).

Crescograph was able to record at magnifications of up to 10,000 times through the use of two different levers. One lever records at 100 times magnification while the other lever takes that image and records at another 100 times magnification. 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.

The electronic crescograph plant movement detector is capable of measurements as small as 1/1,000,000 of an inch.The component which measures the movement is a differential transformer along with a core hinged between two points. It can record plant growth, magnifying a small movement as much as 10,000,000 times.

Sir Jagdish Chandra Bose (Nov. 30, 1858 - Nov. 23, 1937) was one of India's greatest scientists who is best known for his work in biophysics and science of plants and made various contributions in the field of physics, biology, botany and archaeology. India, in 1958, issued a commemorative postage stamp in honour of the centennial of his birth.