Figures in the Diary of Robert Hooke

Felicity Henderson, University of Exeter

Robert Hooke, the early Royal Society’s paid ‘curator of experiments’, kept a detailed diary about his daily life from 1672 to 1694 (though with a long break in the mid-1680s). The diary tells us a lot about Hooke’s working practices and especially his networks of contacts in London. It’s not just an interesting text, though – Hooke occasionally adds a figure amongst his cramped lines of prose. What might these sketches tell us about Hooke’s use of scientific images?

Hooke’s diary, or memoranda, were not meant for anyone other than himself and were primarily intended as a register of his daily activities – things he wanted to remember. Some of Hooke’s figures clearly support this aspect of the diary. But why include pictures as well as verbal descriptions? I think some of these figures show Hooke in the act of thinking things through, trying out new ideas or clarifying old ones. One of the simplest figures in the diary is this drawing of the sun as it rose on 15 June 1676.

Drawing of sun rising
Rising sun, 15 June 1676. London Metropolitan Archives CLC/495/MS01758. © London Metropolitan Archives (reproduced by permission).

The diary entry reads

saw ye sun Rise very ellipticall [figure inserted here] thus the vnder side much flatter then the vpper.’

The wording suggests that Hooke first thought of describing the rising sun as ‘ellipticall’. He then realised this didn’t fully express his observation and added the figure. However he still wasn’t happy, and added further explanation focussing on the disparity between the flatter underside and the rounded top of the sun. Possibly at this point he went back over his figure to emphasise the roundness of the upper curve, as this line is much stronger than the rest of the image. It seems that even this relatively straightforward figure forced Hooke to clarify his description of the sunrise.

Other figures represent much more complex ideas.

Drawing of Richard Reeve's glass furnace
Glassworking furnace, 30 March 1677. London Metropolitan Archives CLC/495/MS01758. © London Metropolitan Archives (reproduced by permission).

This is Richard Reeve’s contrivance for his cementing glasse plates in his furnace’. Reeve had succeeded his more famous father as a maker of optical instruments, and Hooke had previously visited him in February 1674, when he had watched Reeve

joyning glasse plates by grinding them together either by a square joynt [first figure] or by an oblique joynt thus. [second figure] or by an vndulated joynt thus [third figure]’.

Drawing of different methods of joining glass plates
Methods of joining glass, 23 February 1674. London Metropolitan Archives CLC/495/MS01758. © London Metropolitan Archives (reproduced by permission).

Hooke had commented in his diary at the time

I suppose the whole secret consists in the make & heating of the fornace and cooling it wch is neer a week in doing’.

The follow-up visit in 1677 thus represented an opportunity to understand more about Reeve’s ‘secret’ furnace design. The details of the sketch are linked with extensive explanatory notes keyed to letters indicating the different parts of the furnace. It’s interesting to see Hooke using this technique, standard in contemporary scientific images, in his diary. It gives this rough sketch an authority we might not have expected in the informal context of a personal document, and raises the question of what Hooke might have planned to do with the information preserved here. Was it intended to be passed on to Hooke’s philosophical associates?

Other figures in the diary document Hooke’s own inventions, among them the ‘Horizontall Sayles’ drawn in September 1674.

Drawing of Hooke's invention of 'horizontal sails'
Horizontal sails, 26 September 1674. London Metropolitan Archives CLC/495/MS01758. © London Metropolitan Archives (reproduced by permission).

Lacking the detailed annotation of the furnace image, this sketch accompanies a brief note:

Inuented ye Perfection of Horizontall Sayles. by a poysd & turning sayle see ye figure’.

We should read ‘Wind’ and ‘Water’ on the left-hand side as part of the figure: these are aspects of the system more clearly expressed in words than in the rather vague wavy and dashed lines that surround the sails.

These sketches attest to Hooke’s visual approach to the new philosophy, suggesting that thinking about things through graphical representation was something he did routinely, not just when he was explaining his ideas to others. Most of the figures in the diary act alongside words, although there are occasional examples where they replace them entirely (as, for example, tiny drawings of spectacles – quicker than writing out the word in full!). In the context of the diary, the relationship between figures and time is also significant. The diary figures are pinned to a specific date, locating them in time in a way that might have aided in any future priority disputes. But equally, Hooke was clearly not drawing them at the point of observation, discussion or invention. He wrote his diary entries after the event, and therefore the figures must represent some further thought, rather than being an immediate record (just as diary text is always composed after the fact); so we need to see these images as having been influenced by the passage of time.

These are just a few of the figures in Hooke’s diary, but they help us to see how he approached the problem of describing and recording observations and inventions in a private context.