Hydrogen Gas. A variety of atoms, in motion, which fill a space, and which space, when filled with them, is from fifteen to sixteen times lighter than if the space were filled with common atmospheric air. The engraving represents its manufactory in large quantities for the purpose of filling a balloon. The casks placed round are partly filled with water, from which hydrogen is extracted, by putting pieces of zinc into it, and two-fifths of sulphuric acid, or vitriol. This producing an effervescence, the light gas passes out of the casks through the bent tubes which pass through a vessel of cold water under the cask placed in the centre, from which it passes through the bent tube into the balloon, and being so much lighter than atmospheric air, it rises with great force, and carries the balloon with it into the upper regions of the atmosphere.