Letter, from Sir John Herschel to Charles Babbage, dated at Slough Autograph letter signed by sender. Thanks for all the packages. Would like to send copies of the supplement to John Brinkley and Fearon Fallows. Regarding D. F. J. Arago's statement. Method of making a barometer clock. Wishes the president of the Royal Society [of London] was changed every four or five years. Message for W. H. Wollaston from J. B. Biot. 24 October 1820