Letter, from John William Lubbock to Sir John Herschel Autograph letter signed by sender. Was not aware when he wrote his paper that doubt existed regarding the invariability of [the absolute heat of steam?]. Comments on the variations in the theories of S. D. Poisson and Karl Holtzmann. The experiments John Frederick William Herschel suggests would be highly interesting. Would he like to see Holtzmann's paper? 19 February 1845