Letter, from Matthew Henry Webster to Sir John Herschel, dated at Albany [New York] Autograph letter signed by sender, with enclosure and with annotations by recipient. Received John Frederick William Herschel's two letters last autumn. Delayed sending observations until John Frederick William Herschel returned to England. Compared actinometers with those of Mr. Danberry of England and J. S. McCord of Montreal. Encloses letter of introduction to Harmanus Bleecker [American charge d'affaires to the Hague] . 3 October 1838