III. Additional note to the paper "On a supposed alteration in the amount of astronomical aberration of light produced by the passage of the light through a considerable thickness of refracting medium."

Abstract

Some months since I communicated to the Royal Society the result of observations on γ Draconis made with the water-telescope of the Royal Observatory (constructed expressly for testing the equality of the coefficient of sidereal aberration, whether the tube of a telescope be filled with air, as usual, or with water) in the spring and autumn of 1871. Similar observations have been made in the spring and autumn of 1872, and I now place before the Society the collected results. It will be remembered, from the explanation in the former paper, that the uniformity of results for the latitude of station necessarily proves the correctness of the coefficient of aberration employed in the Nautical Almanac.