Sir Richard Threlfall and Sir Horace Darwin

Abstract

MANY of us have read with much interest the understanding obituaries of Sir Richard Threlfall that appeared in NATURE of Aug. 13. Both obituaries dwell on his inventiveness and powers of work. When looking through some old papers to-day, I found a letter from Sir Richard to his friend the late Sir Horace Darwin. In the course of a conversation on a continuous gas calorimeter, which must have taken place about 1900, Darwin suggested that it was advisable to link up automatically the quantity of water heated by the gas flame with the quantity of gas burnt. Threlfall did this, and obtained a recording calorimeter which was far in advance of any other instrument for many years. The letter was evidently written by Threlfall to Darwin after one of the concentrated periods of work referred to in the first obituary notice. It was accompanied by a clear sketch and notes in Threlfall's handwriting.