Before accepting your estimate for the photographic plates illustrating Mr Spencer's paper, the Secretaries wish me to ascertain what would be the cost of reproducing a portion of the tracings which were originally submitted to you. They amount to twenty-three tracings and two diagrams, or about half the number for which you originally estimated. I send them herewith, and shall be glad to have your new estimate as soon as possible.
Asst. Sec. R.S. [Assistant Secretary, Royal Society]'.