Paper, 'On the specific heats of gases at constant volume. (Preliminary note)' by John Joly Joly writes: 'I have found it possible to obtain the specific heat of a gas at constant volume by means of the steam calorimeter, the values obtained being, I believe, reliable as close approximations to the true values. The first method of procedure adopted was to compress by means of a pump a certain quantity of dry air into a thin copper sphere, the sphere being then closed by a screw valve. The quantity of gas in the sphere is ascertained by weighing.' Annotations in pencil and ink. Subject: Physics Received 21 July 1888. Read 22 November 1888. A version of this paper was published in volume 45 of the Proceedings of the Royal Society as 'On the specific heats of gases at constant volume. (Preliminary note.)'. 1888