"It has long been a familiar fact that the bubbles of phosphuretted hydrogen gas consisting of PH3 with an admixture of PH2, give rise by their explosive combustion in the air to a ring of white vapor-like phosphoric acid, which dilating as it ascends exhibits a rotation of each vertical element around the curved axis of the figure. A similar motion is sometimes discernible in the smoke from a cannon, and in the steam which escapes by momentary puffs from a steam-pipe, and as expert smokers know, such revolving rings are readily produced by ejecting the smoky breath in a peculiar manner from the rounded opening of the lips."An excellent paper on the phenomena of vortex rings formed from smoke, etc. Goes into quite a bit of detailed observations. (1858) Illustrated. 8.5" X 11"