Referee's report by George Salmon, on a paper 'On the calculus of symbols.— Fourth memoir. With applications to the theory of non-linear differential equations' by William Henry Leighton Russell No clear statement regarding publication in the 'Philosophical Transactions of the Royal Society'. Has not had time to fully read the paper due to work commitments, and has not seen the third memoir [RR/5/223 and RR/5/224]. Suggests George Boole would be a more suitable referee. Subject: Mathematics [Published in the 'Proceedings of the Royal Society of London', 1864] 19 April 1864