Robert Hooke’s Snowflakes

Many apologies for the long gap between posts! Now that my circumstances have changed, I expect to be able to post more often.

To get things going again I thought I would introduce two of my very favourite ruins, one natural and one artificial, over the course of three posts. In this post I will talk about a drawing of snowflakes by Robert Hooke, objects that Hooke thought to be ruins of once-perfect ice crystals. In the next post I will talk about a ruin that a number of seventeenth century architects, antiquarians and philosophers interpreted in a strangely similar way – Stonehenge. Finally, I’ll put up a third post explaining exactly why I think that Robert Hooke’s attempts to understand snowflakes are so comparable with the attempts of Inigo Jones, Walter Charleton, Isaac Newton and John Aubrey to interpret the meaning of Stonehenge. It might seem at first glance pretty strange to suggest that seventeenth century architects, antiquarians and natural philosophers approached natural and artificial things in very similar ways. But I want to suggest not only that this is exactly what they did, but that by exploring the connections between seventeenth century natural history, architecture and antiquarianism, we can come to understand that natural history at the time was very different to the scientific discipline carried on today in universities.

Robert Hooke’s Snowflakes

In the second volume of the Register Book of the Royal Society, we can find a drawing of snowflakes, made by Robert Hooke, perhaps in December 1662. The description consists of about one folio page of handwritten text, and an image that folds out sideways, a little smaller than a folio page turned on its side:

RegsiterBk(II)_HookeSnowflakes(2)

Photograph of Hooke’s fold-out ink-wash drawing of snowflakes, with inscribed compass and knife marks, in ‘Figures Observ’d in Snow by Mr. Hook’, Royal Society Register Book, Vol. II, p62. Royal Society Centre for the History of Science.

At first glance, Hooke’s image hardly seems worth giving serious attention. These blotchy and impressionistic snowflakes might even be the work of a child, and Hooke saw fit to apologise for them in the text, referring to them as ‘coarse draughts’. Yet, as Matthew Hunter has observed in his wonderful PhD thesis ‘Robert Hooke Fecit: Making and Knowing in Restoration London’, (University of Chicago, 2007), Hooke’s representative strategy was in fact very subtle. He painted each snowflake by laying a dark ink wash over a circle inscribed with a compass and a razor. He divided each circle into six using a straight edge and a razor, as if to construct a hexagon inside the circle.

Close-up detail showing (from the left) the fifth snowflake drawn in the middle row. ‘Figures Observ’d in Snow by Mr. Hook’, Royal Society Register Book, Vol. II, p. 62. Royal Society Centre for the History of Science.

Close-up detail showing (from the left) the fifth snowflake drawn in the middle row. ‘Figures Observ’d in Snow by Mr. Hook’, Royal Society Register Book, Vol. II, p. 62. Royal Society Centre for the History of Science.

The straight lines cut into the paper to make these divisions seem to have served Hooke as the guides for the arms of his snowflakes. If we refer to Hooke’s verbal description, things get even more interesting. He hardly referred at all to the images that he made with the black ink wash, but rather described the regular, geometrical markings he made with the compass, razor and rule: ‘In which I observ’d that if they were of any regular figures, they were always brancht out, with 6 principall branches’. His only remark on the different sorts of snowflake that he illustrated in ink was that they seemed to follow the same geometric pattern that he had also observed in frozen urine crystals: ‘the branches from each side of the stemms were parallel to the next stem on that side.’ We know from Hooke’s book containing verbal and graphic descriptions of microscopic things, Micrographia (1665), that he thought that snowflakes were ruins. Their more perfect geometric figures had been damaged by the wind during their descent from the clouds. ‘Could we have a sight of them through a Microscope as they are generated in the Clouds before their Figures are vitiated by external incidents’, he wrote, ‘they would exhibit abundance of curiosity and neatness.’

Hooke’s drawing of snowflakes takes into account his belief that they were really the ruins of more perfect forms. He did not describe exactly what one might see. Rather, he picked out features through his razored lines and circles and through his verbal description that gave him clues about a form the snowflakes once had, and about their design, shorn of extraneous details. As Matthew Hunter has also noted, Hooke brought to bear considerable experience of the formation of crystals with six branches. The item immediately preceding Hooke’s account of snowflakes in the Royal Society Register Book is an account of the formation of urine crystals, made under controlled, experimental conditions. This is an order that Hooke preserved in his Micrographia. In a section describing the crystals that form in liquids when frozen, an account of the crystals that form in urine crystals under experimental conditions comes immediately before the discussion of ruined snowflakes. Taken together, the descriptions seem to comprise an assertion that snowflakes would have a form as regular as that found in urine crystals, if only they could be observed before the battering that they receive at the hands of the wind on their way down to earth. Perhaps this justified Hooke’s incision of regular hexagons in the place of the multitude of irregular patterns that he actually admitted to finding.

I would suggest that Hooke felt able to impose the sorts of geometric shapes that he found in urine crystals on to snowflakes because he thought that it was possible to see a ‘design principle’ at work in the urine crystals that must apply to other sorts of crystals. He incised geometrical figures in his ruined snowflakes, comparing those figures with the ones he had found in other, more perfect, frozen crystals to get some sense of their meaning. His description highlights the geometrical qualities he found in these figures, and permits a comparison to other forms, better-known from observations and descriptions made of them in their pristine state. Hooke was much less interested in the forms of snowflakes as he found them than he was in the forms of snowflakes as they must once have been.

In this aim, Hooke had something very important in common with the seventeenth century architects, antiquarians and philosophers who inquired into Stonehenge. They took it for granted that Stonehenge was a ruin, only likely to be interpreted if one could work out what it had once looked like. Possessing almost no sense of prehistory, they thought that they could interpret Stonehenge if they could only work out what it had once looked like. Armed with that knowledge, they could trawl ancient texts for descriptions of similar buildings, or perhaps even find a more perfect, less ruined example of a similar structure. They went about trying to restore the form of Stonehenge using drawings and other techniques that were remarkably similar to those employed by Hooke in his efforts to understand snowflakes. To find out more about this, check out the next post!

 

I would like to emphasise that much of the writing here would have been impossible, had I not consulted Matthew Hunter’s PhD Thesis, ‘Robert Hooke Fecit: Making and Knowing in Restoration London’, (Unpublished Doctoral Thesis, University of Chicago, 2007). Although this blog post develops my own ideas about Hooke’s interpretation of snowflakes, it rests upon the excellent account that Hunter offers, especially his detailed attention to the incisions made in the snowflakes and his discussion of the links between the snowflake drawing and that of the urine crystals. My contribution here will be developed in the next two blog posts, when I discuss my interpretation of Hooke’s work in relation to contemporary discussions of Stonehenge.

The Sheldonian Theatre – Ancient and Modern

I will continue to blog about the things that I encounter as I teach my Renaissance Special Subject. Today, however, I have found something much closer to my research interest – the history of science in the 17th and 18th centuries.

Today’s thing is very easy to find, and it is very well-worth visiting. It is the Sheldonian Theatre, one of the most important buildings in Oxford University. The theatre was paid for by Gilbert Sheldon (1598-1677), who ended his career as Archbishop of Canterbury.

Why is this building important in the history of science? Firstly, it was built by someone who would now be understood as a scientist. Although Wren is today most famous for his architectural work, of which St. Paul’s Cathedral is the most famous example, he had deep scientific interests. You can see this if you pay close attention to the Sheldonian Theatre.

Outwardly, it looks much like a building in the classical style, designed like so many other buildings in that time in accordance with Roman Architecture. In fact Wren drew inspiration from an ancient Roman building that had been drawn by Sebastiano Serlio (1475-1554) – the Theatre of Marcellus in Rome.

Design of the floor-plan of the Theatre of Marcellus from Serlio’s Seven Books of Architecture (1540).

 

Modern Seating Plan of the Theatre

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The Sheldonian Theatre

So does this building just show us that Wren copied ancient architectural ideas, in spite of his own engagement with the most modern ideas of his time? Actually, the answer is ‘no’. One remarkable feature of the building is its flat internal ceiling, which actually supports much of the weight of the roof structure and cupola above it. The ceiling is decorated with (removable) painted panels but in the original design it fulfilled a load-bearing function, something that should have been impossible because there were no timbers long enough to bridge the gap.

The painted panels are beautiful, but they conceal the ingenuity of the design used by Wren.

 

How did Wren get a flat ceiling that would also help hold up the roof? He turned to the mathematician John Wallis, who came up with an ingenious solution. Rather than explain myself, I quote from the blog ‘Maths in the City‘:

”Wallis’ devised an ingenious pattern of interlocking beams, so that every beam was supported at both ends – either by the walls or by other beams – while every beam also supported the ends of two other beams.  So for every beam, the downward forces from those resting on it are balanced by the upward forces from the beams, or wall, supporting it.   In an impressive feat of calculation, Wallis demonstrated that his geometrical flat floor could carry loads when supported by the walls alone by solving  a set of 25×25 simultaneous equations using just pen and paper!”

This is a model showing us what Wallis’s solution looked like:

Wallis’s Ingenious Solution

 

Many of Wren’s buildings concealed astonishing technical solutions, based on new ideas in mathematics and physics, beneath a veneer of ancient design rules.