Air-Jacket, a dress made of leather, in which are contained several bags or bladders, composed of the same materials, and communicating with with other. These are filled with air blown through a leather tube, having a brass stop-cock, accurately ground at its extremity. In order to confine this elastic fluid, the jacket must previously be wetted; and thus the person is supported in the water without any effort, by the aid of these bladders placed near the breast. Those who are proficients in the art of swimming, condemn such artificial assistance as cannot always be readily procured : in our opinion, the most proper and easy method of acquiring this useful talent, is that mentioned by Dr. Struve, in his German treatise on the Physical Education of Children, lately published, with three Introductory Lectures by the Editor of this Encyclopaedia. —See the article Swimming.