Letter, from John Stuart Mill to Sir John Herschel, dated at India House Autograph letter signed by sender. Acknowledges with pleasure John Frederick William Herschel's kind note. Owes much to John Frederick William Herschel's book in the chapter on experimental methods. John Frederick William Herschel will doubtless find Auguste Comte's book worth reading. Would like a note of any errors in John Stuart Mill's book. 1 May 1843