Sends specimen of esculine, or polychrome, extracted from horse chestnut. It exhibits optical properties that JH recently investigated. Offers to send specimen of colophene. Asks JH's recommendations for foreign secretary of R.S.L., following death of J. F. Daniell. This officer must supervise magnetic and meteorological observatories. [JH annotation: 'By all means appoint Sab(ine).']