We’ve been having some scorching weather of late, with temperatures reaching 32C here in central London. On days like these, you find any excuse to conduct some research in the archive store so as to cool down in the air-conditioned environment. One item I came across recently is a letter from 1727, sent on today’s date (28 July) and addressed to James Jurin FRS, which illustrates the power of the sun’s rays. It tells the story of a Mr John Scrimshire and his ill-fated nightcap…

‘Mr John Scrimshire in Bow Lane, having a lodging at South Lambeth, went that morning about seven o’clock out of his Chamber to walk in the garden, he had not been long there before he discovered smoke coming out of his chamber window, when immediately returning he found to his great surprise several things in the room in flame, particularly a calico night cap which lay on a table near the window and a cloth which covered the table. It was some time after he had extinguished the flames before he could conceive how the accident should happen, but at last concluded that a bottle of water being on the table, and the rays of the sun passing through it had met in a focus where the night cap lay and lit it on fire. He confirmed this by trying the experiment upon a part of the linen which was not consumed, the rays lit it again in a flame.’

Such damaging effects of reflected sun rays converging and focusing on one point have been in the news a fair bit recently, from melting car parts caused by the sun reflecting off glass skyscrapers in the City, to an innocent looking crystal doorknob which teamed up with the sun to trigger a house fire in South London earlier this month.

Enjoy this great summer we’re having, but do be careful where you leave your nightcap…

 

Letter from J Smart, dated at Guildhall, to James Jurin, 28 July 1727. Royal Society manuscript EL/S2/63

 

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