Referee's report by John Henry Poynting on a paper, 'A wave-length comparator for standards of length: An instrument for fine measurement in wave-lengths of light. - With an appendix on the use of wave-length rulings as defining lines on standards of length' by Alfred Edwin Howard Tutton Sectional committee: Physics and chemistry Recommended for publication in Philosophical Transactions, with no modifications. The paper is 'important and the method marks a distinct advance'. [Published in Philosophical Transactions A, 1911]. Endorsed on verso as received 30 June 1909. June 1909