Letter, from [D. M.] Vallot to Sir John Herschel, dated at Dijon Autograph letter signed by sender. Missed John Frederick William Herschel (traveling with Charles Babbage) when they passed through Dijon. Provides some barometric observations along with a comparison of measuring instruments. Appears to be commenting on some of Charles Babbage's interests in statistics, and believes that G. W. Leibniz did some work in this also, but died before publishing it. [Parts of this letter illegible.] 2 October 1821