Robert Hooke's Micrographia
Micrographia, or, Some physiological descriptions of minute bodies made by magnifying glasses, with observations and inquiries thereupon (1665) was the first important work on microscopy. The name Micrographia is derived from micrography Â? a word that first appeared in English in 1658, and is Latin for 'little pictures'. The book was popular and the print run extended to as many as one thousand copies. Indeed Samuel Pepys wrote in his diary that it was 'the most ingenious book that ever I read in my life' and reputedly stayed up until 2am reading it. The flea, fly, and gnat plates are seen as particularly noteworthy and the beauty of the images would have attracted people to read it.
Its popularity was perhaps unsurprising given its revelation of a previously unknown world so close to home. It challenged people's perceptions the nature of things in a similar way to Galileo with astronomy and revealed new and interesting structural features of many items from the natural world, as well as everyday objects, such as a needle, razor and cork. In his introduction Hooke discusses how curious the natural world is and how 'excellencies and mysteries do appear' once objects are magnified and we go beyond what is visible to the naked eye.
Micrographia was not the only book on microscopy produced in the seventeenth century, but it was by far the most accurate, and the most detailed. Gionbatista Hodierna (1597-1660) published L'Occhio della Mosca (The Eye of the Fly) in 1644. This was the first book devoted to displaying microscope observations, however, printed with woodblocks, the illustrations were cruder than those of Micrographia. A closer contemporary to Hooke was Henry Power (c.1626Â?1668) who published Experimental Philosophy in 1664. Both Hooke and Power were fellows of the Royal Society and had the same publisher, but critics have suggested that Power's lack of subtlety of shading or texture in the portrayal of microscopical observations make it more comparable to Hodierna than Hooke.
Hooke was certainly concerned with accuracy; Â?in making them, I indeavoured [sic] (as far as I was able) first to discover the true appearance, and next to make a plain representation of it. This I mention the rather, because of these kind of Objects there is much more difficulty to discover the true shape, then of those visible to the naked eye, the same Object seeming quite differing, in one position to the Light, from what it really is, and may be discover 'd in another. And therefore I never began to make any draughts before by many examinations in several lights, and in several positions to those lights, I had discover'd the true form.' He was also engaged with an artistic and visual culture, having been apprenticed to Dutch painter Peter Lely, and being interested in printing techniques. He was on friendly terms with many printers and engravers such as Wenceslaus Hollar and William Faithorne who he shared advice with and borrowed instructive books from. Meghan C. Doherty argues that it is Hooke's familiarity with the 'visual vocabulary' of portrait engravings and understanding of how to indicate the fall of light in particular that enabled him to capture his microscope observations so accurately. She picks out the engravings of the spider, which on one plate has a couple of legs missing, as an example of how Hooke recorded exactly what his objects of study looked like at a given time (the spider having lost its legs in the course of Hooke's examination), in the same way as an engraved portrait.
The clear and coherent methods for engraving made possible the more accurate translation of a drawing into print but it still required Hooke's method and skill of observation to produce the best images. Hooke remarked on errors in Power's Experimental Philosophy caused by neglecting to observe the objects under different lighting conditions and thus mistakenly ascribing effects of the instrument to the object itself.
As well as an interest in drawing and printmaking Hooke also had a lifelong interest in scientific instruments. He was a founding member of the Royal Society and became fellow in 1663. He was their curator of experiments with the responsibility of demonstrating several experiments at meetings. He had also served as an assistant to Robert Boyle working on the pneumatic engine (vacuum pump) and in his experiments on the weight of air. He also designed a new microscope, which was made by Christopher Cock, bought by the Royal Society for their own use. It is interesting that some of the scientific instrument makers were often simply concerned with the construction of the device rather than understanding how it worked; Hooke directed Christopher Cock as to the specifications of his microscope, and Samuel Pepys noted how another maker, R. Reeve, had no knowledge of how the microscope worked. Jim Bennett has argued that Hooke's connections to instrument makers and understanding of the mechanics of them helped him to integrate developments in mechanical arts to natural philosophy.
Hooke describes and illustrates the kind of compound microscope he used to make his observations in Micrographia although there are no surviving examples of the exact type. Compound microscopes worked using two lenses; a short focus lens placed as near to the object as allowed by focal length alongside an eye lens of larger diameter located nearer to the eye of the observer. The description and illustration of the instrument would have enabled replication of his observations by anyone with the necessary skills. The significance of repeatability would not have been lost on the Royal Society's curator of experiments.
Bennett, J., in Bennett, Cooper, Hunter, Jardine, Eds., London's Leonardo: the life and work of Robert Hooke, Oxford University Press, Oxford, 2003.
Chapman, A. England's Leonardo: Robert Hooke and the seventeenth-century scientific revolution, Institute of Physics Publishing, Bristol, 2005.
Doherty, M.C., Â?Discovering the Â?true form:' Hooke's Micrographia and the visual vocabulary of engraved portraitsÂ?, Notes and Records of the Royal Society, September 2012, vol. 66, no. 3, pp 211-234.
Neri in O'Malley, Therese ; Meyers, Amy R. W., The Art and History of Botanical Painting and Natural History Treatises, Washington, DC, 2002.
Oxford English Dictionary: Entry for micrography.
Oxford Dictionary of National Biography; Pugliese, P.J., Robert Hooke; and Johns, A., Henry Power.