Robert Hooke (1635 - 1703)
The Englishman Robert Hooke (18th July 1635 - 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke's law), his book Micrographia, published in 1665 and for first applying the word "cell" to describe the basic unit of life. It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some fifteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor.
Here, we focus on his pioneering work using the microscope to document observations of a variety of samples in his book Micrographia, published in September 1665.
Hooke began his famed career by initially studying at Wadham College, Oxford, where he worked closely under John Wilkins with other contemporaries, including Thomas Willis and Robert Boyle, for whom he built the vacuum pumps used in Boyle's gas law experiments. He also built some of the earliest telescopes, observing the rotations of Mars and Jupiter, and, based on his observations of fossils, was an early proponent of biological evolution. If that wasn't enough, he investigated the phenomenon of refraction, deducing the wave theory of light, and was the first to suggest that matter expands when heated and that air is made of small particles separated by relatively large distances, yet curiously Robert Hooke is somewhat overlooked in his contributions to science, perhaps as there were many people who wrote of Hooke as a difficult personality, being described as of "cynical temperament" and of "caustic tongue". There were also disputes with fellow scientists, including disputes with Isaac Newton over credit for work on gravitation and the planets. Though it must be remembered that Hooke lived at a time of immense scientific progress and discovery and none of the above diminish Hooke's inventiveness, his remarkable experimental facility, and his capacity for hard work.
In 1662 Hooke became Curator of Experiments of the Royal Society, meaning that he was responsible for demonstrating new experiments at the Society's weekly meetings. During this time, Hooke published the book Micrographia, an accurate and detailed record of his observations through his microscope (one of the best such microscopes of his time), illustrated with magnificent drawings. With it he observed organisms as diverse as insects, sponges, bryozoans, foraminifera, and bird feathers.
Robert Hooke's microscope
Perhaps his most famous observations were in his study of thin slices of cork, describing the pores, or "cells" he viewed. Hooke had discovered plant cells, or more precisely, Hooke had been viewing the cell walls in cork tissue. In fact, it was Hooke who coined the term "cells": the boxlike cells of cork reminded him of the cells of a monastery. Hooke also reported seeing similar structures in wood and in other plants. Hooke also famously described a fly's eye.
The extract below from Micrographia demonstrates Hooke's perspective on how the microscope is utilised to enhance the senses...
"In the collection of most of which I made use of microscopes and some other glasses and instruments that improve the senses... only to promote the use of mechanical helps for the Senses, both in the surveying the already visible World, and for the discovery of many others hitherto unknown"
- Micrographia, by Robert Hooke (1665)
In addition to Hooke's observations, Micrographia is known for its spectacular copperplate engravings of the miniature world, particularly its fold-out plates of insects. The engraving of the louse in particular folds out to four times the size of the book. Although the book is best known for demonstrating the power of the microscope, Micrographia also describes distant planetary bodies, the wave theory of light, the organic origin of fossils, and various other philosophical and scientific interests of its author.
Hooke also achieved fame in his day as Surveyor to the City of London and chief assistant of Christopher Wren. Hooke helped Wren rebuild London after the Great Fire in 1666, and also worked on designing many of London's landmarks, including the Royal Greenwich Observatory and the infamous Bethlem Royal Hospital (which became known as 'Bedlam').
Hooke's reputation was revived during the twentieth century and after a long period of relative obscurity he is now recognized as one of the most important scientists of his age.