Laurence Scales explores the life of an unorthodox character in the history of scientific theorists.
At school I was slow to grasp the point of algebra. So, it was Mr Yelland, the pottery teacher, rather than the maths master, who first showed me a convincing proof of Pythagoras’s theorem with a pair of scissors. It was elegant and ingenious. That proof, I recently found out, was devised neither by Pythagoras nor Mr Yelland but by an eccentric London bookkeeper called Henry Perigal (1801-1898) in 1830.
Most scientists and scientific institutions in the public eye have a file of letters from crazy people. (The answer, before you ask the question, is yes, several.) These include their theories of the universe and their designs for perpetual motion machines. Perigal was trying to square the circle, another favourite with cranks, when he came up with his novel proof of Pythagoras.
He had another odd notion. It was that the moon does not rotate about its own axis and yet he was a welcome attendee at the Royal Astronomical Society and at the ninetieth birthday celebration of the Astronomer Royal, George Airy, at Greenwich. Indeed, his acknowledged skills were appreciated by someone who otherwise made something of a study of cranks, mathematician Augustus de Morgan who is best known for his work on logic.
Compound rotations (wheels rotating about wheels) can be dizzying to the imagination but Perigal had a better understanding than most as he was an expert at lathe work, and the development of the geometric chuck which with compound rotations can turn out flowery looping patterns, such as were once common as anti-forgery devices on banknotes. It was through his facility with the lathe, that he was able to help de Morgan by producing wood cuts to illustrate a maths book.
Some charming photographs of Perigal can be seen on line at the Oxford Museum of the History of Science. I particularly like one of him (in his nineties) taking his ease, but still wearing his top hat, in a hammock in the garden with his friend, meteorologist James Glaisher. (Perigal was Treasurer of the Royal Meteorological Society for several decades and he only retired from paid employment at the age of 87.)
On his lunar fixation, the Monthly Notices of the Royal Astronomical Society, goes on to say affectionately, ‘To this end he made diagrams, constructed models, and wrote poems; bearing with heroic cheerfulness the continual disappointment of finding none of them to any avail’.
Some of Henry Perigal’s models ornament the Royal Astronomical Society by whose kind permission I was able to take photographs and include them here:
A few of his models have survived at the Royal Astronomical Society and (by some mishap) some of the poems are also still with us, pasted into a huge scrap book at the British Library, so I am able to complete this blog with a selection of Henry Perigal’s verses.
Perigal became a member of the Royal Institution at the age of 94,supported by various dignified figures: chemist William Crookes, electricians William Preece and David Hughes, physicists C. V. Boys and Silvanus Thompson, and Augustus Stroh, the inventor of the horn violin.
Earth’s Axial Rotation
All recognise the daily practice
Of Earth to turn upon her axis;
Distinguished by the appellation
Diurnal axial rotation;
Whereby, if we opine aright
We get alternate day and night,
But this an equivoque conveys
T’wixt solar and sidereal days,
For though we see the stars appear
Three sixty six times in a year,
The days enlightened by the sun
Are just that number – minus one.
Will F.R.A.S. tell us why
The difference is unity?
And, if he cannot, may I ask
R. Proctor to perform the task.
The Moon Controversy, Part I - ExplanationI
Laurence Scales is a volunteer working with the Ri Heritage and Collections team. He also leads unique and eclectic London tours focused on the curious history of science, invention, and medicine, most recently one devoted to Geeky Ladies. He is a graduate in engineering and has worked in various technological industries.