Letter from Svante Arrhenius, Experimentalfaltet, to Sir Joseph [Larmor] He recalls the days he spent in Cambridge in the previous year, gives thanks to Larmor and wishes him a happy Christmas. Some days ago he received a letter and some proofs of a book from Mr. Tunzelmann. He says that Arrhenius has fallen into an error regarding the pressure of radiation. His correspondent had fallen into the same error until Sir Joseph Larmor called his attention to an analysis in his Philosophical Transactions paper and to papers by Lord Rayleigh. Arrhenius is very interested in this question and has used the calculations of Schwarzschild on the rate of pressure of radiation to the gravity of a particle. He asks if this calculation is correct. He would suppose as a result that gas molecules, and alpha and beta particles could not be driven away from the Sun by pressure of its radiation. He notes the ratio for comets and Scharzschild's assertion that radiation pressure in the neighbourhood of the Sun should not exceed ten times the gravity. He has helped himself by his suppositions about fine coal dust with a figure given by [Ernest Fox] Nichols and [Gordon Ferrie] Hull. 20 December 1910