We shall be glad to have your photographs as a lantern exhibit. We have here an electric lantern, bearing a condenser of 4 inch diameter, and slide carriers of varying sizes. It would be well for you to let us know if your slides are of one size, or their dimensions, so that we may suit a carrier for them. You might send a piece of paper of the actual size of one of them for convenience sake.
Yrs [Yours] faithfully,
Asst Sec RS [Assistant Secretary, Royal Society]'.