Letter, from Sir John Herschel to William Radcliffe Birt, dated at Slough Autograph letter signed by sender. Checked June observations of Mr. Robertson in Athenaeum. Found William Radcliffe Birt's statement correct [see William Radcliffe Birt's 1831-9-11]. Wrote to Meteorological Society for explanation. Thanks for pointing out difference in March observations. John Frederick William Herschel is honorary member of [Meteorological] Society. 23 September 1838