The specific gravity of sulphuretted hydrogen almean temperature and pressure is 10645, which differs very little from the estimation of M. Kirwan * that of sulphureous and gaz is 20967 in the last bakerian lecture, I have estimated the specific gravity of sulphureous hydrogene at 35 grains, the 100 cub. inetres. *according to this last expérience sulphuretted hydrogene is composed of 1 proportion of hydrogene represented by 1, and 1 of sulphur represented by 13,4.