Adverting to your kind offer to lend microscopes for next Thursday's Croonian Lecture, I have just heard that we shall require eight to ten microscopes. I do not know whether you can lend so many. High powers are not required; the objectives should be not more than 1/4 in. [inch], not less than 1/2 in., that is, about the same power as the objective C of Zeiss. We should be willing to pay a fee for the hire of these microscopes, and should be obliged if you could send them in on Wednesday afternoon.
Asst. Sec. R.S. [Assistant Secretary, Royal Society]'.