Referee's report by Sydney Chapman, on two papers 'The diffusion and thermal diffusion of hydrogen-deuterium, with a note on the thermal diffusion of hydrogen-helium' by H R Heath, T L Ibbs and N E Wild, and 'Thermal diffusion in hydrogen-deuterium mixtures' by K E Grew Sectional Committee: Physics Recommended for publication in the 'Proceedings of the Royal Society of London'. Suggests correcting some of the values across the two papers. Contains extra question - 'Is there any information contained in the paper which likely to be of value to the enemy?' Referee replies no. [Published in the 'Proceedings of the Royal Society of London'] Endorsed on recto as received 13 March 1941. [March 1941]