Referee's report by Charles Galton Darwin, on a paper 'Time-lag in a control system' by A Callender, Douglas Rayner Hartree and A Porter Sectional committee: Mathematics Not recommended for publication. The methods used are sounds and few faults can be found with them. However, the text is difficult to understand and it 'does not fit in anywhere'. The account showing the troubles in the design and how they were overcome might be worth writing, as it would results in a much shorter paper. . It would be better suited to an engineering journal. [Published in Philosophical Transactions A, 1936]. Endorsed on verso as received 24 October 1935. October 1935