Letter from [Jean-Baptiste] Biot, Paris, to Captain Henry Kater, No.1 Union Place, Regent's Park, New Road, London Thanking Kater for his pendulum results, which he cited at the public session of the Academie. There is a difference between Biot's results and Kater's, which is unsurprising and accptable. Biot's were rough conclusions, based on experiments in Foranterra and Dunkirk; he discusses this at length. Biot's results had been presented at the Societe Philomatique and in the previous month at the Institut. Biot sent to Kater a copy of his work on polarization in light transmission; he set fire to a building as a consequence of that work last summer, after a heater exploded. Copies were also sent to [Thomas] Young and [William Hyde] Wollaston. As regards to palladium, Arago is in charge of answering Wollaston. He sends regards to the Somervilles and others including Mrs Kater, which was so good to everyone. 29 April 1819