Autograph Letter Signed, to C.W.Cooke, agreeing “to see the casting of the condenser on Thursday next”. 1 page 7 x 4½ inches, in good condition. 41 Finsbury Square, 28 April 1863. Henry Letheby (1816-76), analytical chemist, medical officer of health and analyst of food for the City of London. Published ‘Food, Its Varieties, Chemical Composition, etc.’ .