Crescograph
Device for measuring plant growth, invented by Jagadish Chandra Bose.
A crescograph measures plant growth. Jagadish Chandra Bose invented it in the early 1900s. The original Bose model uses clockwork gears and a smoked glass plate to track the movement of a plant’s tip or roots. Two levers achieve magnifications up to 10,000 times: the first magnifies 100 times, and the second magnifies that image another 100 times. Marks on the plate are made every few seconds, showing how growth rate changes under different conditions. Bose tested the effects of temperature, chemicals, gases, and electricity.
The electronic version detects movement as tiny as 1/1,000,000 of an inch, though it normally operates between 1/1000 and 1/10,000 of an inch. A differential transformer with a movable core hinged between two points senses the movement. A micrometer adjusts and calibrates the system. This device can magnify small growth movements up to 10,000,000 times. Because it is so sensitive, Bose placed India-rubber sponges under the table legs to cancel vibrations that could skew results.
- Inventor
- Jagadish Chandra Bose
- Invention period
- early 20th century
- Field
- plant physiology
- Known for
- measuring plant growth at high magnification
- Key feature
- magnification up to 10,000 times (mechanical) or 10,000,000 times (electronic)
Lore & Background
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). It is 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. 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 along with a movable core hinged between two points. A micrometer is used to adjust and calibrate the system. It can record plant growth, magnifying a small movement as much as 10,000,000 times.
This machine is highly sensitive; Bose padded the legs of the table on which the crescograph was being used with India-rubber sponges. This negated any vibration which could affect results.
Reader's Guide
The crescograph represents a significant early 20th-century innovation in plant physiology, allowing precise measurement of plant growth responses to environmental stimuli. By magnifying movements up to 10,000 times mechanically and later 10,000,000 times electronically, it enabled observations of growth rates under varying conditions such as temperature, chemicals, gases, and electricity. The device's sensitivity required vibration-dampening measures, such as India-rubber sponges under the table legs. The electronic version, using a differential transformer and micrometer calibration, could detect movements as small as 1/1,000,000 of an inch. This instrument provided a quantitative method for studying plant behavior, contributing to the understanding of how plants respond to their environment. Its legacy lies in demonstrating that plant growth can be measured with extreme precision, influencing later developments in plant physiology and instrumentation.
Did You Know?
- The Bose crescograph uses two levers to achieve magnifications of up to 10,000 times.
- Bose padded the table legs with India-rubber sponges to negate vibration.
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