Letter, from John William Lubbock to Sir John Herschel Autograph letter signed by sender. Will find the reference to S. D. Poisson in his own paper on the Heat of Vapours. The subject is in a state of confusion. John Southern's experiments are detailed in John Robison's Mechanical Philosophy, which can be sent from the Royal Society [of London] library if John Frederick William Herschel does not possess it already. 13 January 1845