John JeffriesBorn 5 Feb 1744; died 16 Sep 1819 at age 75.American physician and scientist who financed two balloon flights for himself and a Frenchman, Jean Pierre Blanchard, with experience in balloon flight. Jeffries wished to make scientific and meteorological observations. The first flight took place in London on 30 Nov 1784. Jeffries had provided himself with thermometer, barometer, electrometer, hygrometer and timepiece. He took air samples at different elevations for Cavendish, who subsequently made a chemical analysis of the air. The twelve observations of temperature, pressure, and humidity that Jeffries made were the first scientific data for free air, to a height of 9,309 feet. The values agree closely with modern determinations. On 7 Jan 1785, they made the first balloon crossing of the English Channel.Image: Jeffries posed as if in balloon, holding barometer. |
