The other Method of filling a Balloon with permanently elastic inflammable Air, and then closing it is a tedious Operation, and very expensive; Yet we are to have one of that kind sent up in a few Days. It is a Globe of 26 feet diameter. The Gores that compose it are red and white Silk, so that it makes a beautiful appearance. A very handsome triumphal Car will be suspended to it, in which Mess^rs. Robert, two Brothers, very ingenious Men, who have made it in concert with Mr. Charles propose to go up. There is room in this Car for a little Table to be placed between them, on which they can write and keep their Journal, that is take Notes of every thing they observe, the State of their Thermometer, Barometer, Hygrometer, &c which they will have more Leisure to do than the others, having no fire to take Care of. They say they have a contrivance which will enable them to descend at Pleasure. I know not what it is. But the Expence of this Machine, Filling included, will exceed, it is said, 10,000 Livres. This Balloon of only 26 feet diameter being filled with Air ten times lighter than common Air, will carry up a greater Weight than the other, which tho' vastly bigger was filled with an Air that could scarcely be more than twice as light. Thus the great Bulk of one of these Machines, with the short duration of its Power, & the great Expence of filling the other will prevent the Inventions being of so much Use, as some may expect, till Chemistry can invent a cheaper light Air producible with more Expedition. But the Emulation between the two Parties running high, the Improvement in the Construction and Management of the Balloons has already made a rapid Progress; and one cannot say how far it may go. A few Months since the Idea of Witches riding thro' the Air upon a Broomstick, and that of Philosophers upon a Bag of Smoke, would have appeared equally impossible and ridiculous. These Machines must always be subject to be driven by the Winds. Perhaps Mechanic Art may find easy means to give them progressive Motion in a Calm, and to slant them a little in the Wind.