Copy letter from an unknown correspondent, to Mr Collings, 172 Strand 'Herewith. 6 dias. [diagrams] to be done b. on w. [black on white] for Proc ['Proceedings of the Royal Society']. Also two curves which the author intended for plates, but if they will come easily into the page as blocks, I think they may be w. on b. [white on black] - I leave it to you whether to reduce them sufficiently to bring them into the breadth of the page as half page dias, or to make them full-page dias'. 29 January 1892