Robert Hooke's Micrographia was published in 1665. Hooke worked in the Royal Society as Head of Experiments and his scientific interests were wide. Perhaps one of his most well-known contributions to science was the law of elasticity, known as Hooke’s Law, which states that the extension of a spring (or wire) caused by an applied force is proportional to the force.
He made several other influential and pioneering contributions. For example, he invented the compound microscope, which he used in his demonstrations at the meetings of the Royal Society. Through his microscope Hooke looked at insects, plants and bird’s feathers. These were shown in Micrographia in great detail. Hooke uses the book to suggest a new way of doing science, through careful observation and recording the results. This became a tenet of scientific practice. Many of his observations were drawn on impressive copper-plated illustrations for example, the flea, which opens to four times the size of the book. Hooke described a flea as adorn'd with a curiously polish'd suite of sable Armour, neatly jointed.
In its day Micrographia was a best-seller, and it received praise from Samuel Pepys, who stayed up until two in the morning reading the book. He then said that it was the cleverest book he had ever read!
Another famous image from the book is Hooke's study of cork under a microscope. Through this, he was the first, though without realising it initially, to discover the structure of plants cells. He described the material as follows:
“. . . I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any writer or person, that had made any mention of them before this. . .”
Hooke wrote about his theory of combustion in Micrographia, when he surmised that the process was maintained by a substance that was mixed with air. Thus Hooke's theory can be construed as a precursor of the modern theory of combustion; some even believe that Hooke would have discovered Oxygen had he continued his experiments.
The pictures of fossils under a microscope persuaded Hooke that fossils originate, not from stones, but from creatures that lived many centuries before. This was a novel theory, proposed at a time when it was not realised that the Earth was as old as it is and that different creatures lived on it at different periods. This is another example of Hooke’s far-sighted vision and ideas.
Despite the fact that the book is better known for its descriptions using the microscope, Micrographia also describes distant planets and discusses the theory of light waves. His work on gravity, and astronomy can be seen as a precursor of that of Newton, who went on to develop the laws of Classical Mechanics and gravitation.