The mistake of colouring your plate seems to have occurred through some of the copies being printed off by artificial light in order to hurry the issue. Mr Wilson greatly regrets the mistake, and offers to strengthen the colour in accordance with your wishes. As only a portion of the edition has been bound up, I am sending back the bulk of the plates to be rectified, and if you will send the separate copies, which I presume have been delivered to you, to Mr Edwin Wilson, Post Office Terrace, Cambridge, he will have the colour rectified and the numbers rebound.
I am, yours truly,
Asst. Sec. R.S. [Assistant Secretary, Royal Society]'.