Unpublished letter, regarding thermometers from G [George] Cayley to [Thomas] Young In this covering letter, Cayley introduces his short publication on Fahrenheit's and Reaumur's thermometers. He explains his reasoning behind the belief that Fahrenheit may have made errors in considering the freezing point of water and suggests improvements to the thermometers. A graphite annotation on first page reads 'Not for reading T. Y. [Thomas Young]'. Subject: Scientific Instruments Written by Cayley in Durham [Tyne and Wear, England]. 15 November 1825