Copy letter from Francis Alexander Towle, Assistant Secretary of the Royal Society; to Professor [Alfred William] Porter, FRS Encloses the manuscript of the paper by [Chandrasekhara Venkata] Raman and V. S. Tamma, 'A new optical property of biaxial crystals' [not enclosed]. Reminds Professor [Alfred William] Porter of the regulation requiring that a copy of any paper communicated to the Society must remain in their possession. 2 November 1921