[Reports from Sir John Herschel, Professor Airy, and Captain Smyth, on the fluid-lens telescope]

Abstract The Reports received by the Secretaries, from Sir John Herschel, Professor Airy, and Captain Smyth, on the Fluid-lens Telescope constructed for the Royal Society on Mr. Barlow’s principles, were, by direction of His Royal Highness the President and Council, read to the Society at this meeting. Sir John Herschel's Report. I have seen Mr. Barlow’s telescope at Cambridge, and examined it on several objects, in a very fine night, the 25th (if I remember) of June. As I have now no time to give it any further trial at Slough, (where I have no longer, either, any achromatic telescope of sufficient power to compare it with, all my apparatus being dismounted and in course of packing,) I will here state in few words, as my report on it, all I could then collect relative to its action. 1. Achromaticity.—Mr. Barlow’s telescope is remarkably free from the dispersion of colour, very much more so than I could have expected from the nature of the correcting medium, and nearly or quite as much as could be desired.