Letter from William George Penney, on a paper 'The effect of diffusion of the main reactants on flame speeds in gases' by J Corner to D C Martin, Assistant Secretary of the Royal Society Returns the paper and now considers it suitable for publication. The pape rhas been altered extensively and the length is seventy per cent of what it originally was. [Published in Proceedings of the Royal Society A, 1949]. Endorsed on recto as received 7 April 1949. 6 April 1949