Letter from J [John] Herschel, Brompton Barracks, Chatham, to 'Dear Pater' [John Frederick William Herschel] His father's explanation of the setting of lime was just what he required. He discusses plaster of Paris, then hydraulic cements and their setting properties, the latter mentioned in lectures. He has his father's Civil Engineers paper which he begs to keep for a day or two longer, to show it to the architect. He gives thanks for a cheque, and notes that a bill for a hat was his. He gives thanks for letters and parcels, including letters from France via Alick [Alexander Stewart Herschel] which he will return with the Civil Engineers paper. With a postscript marked 'For the children', on chrysalises. 13 May 1857