John Jeffries John Jeffries John Jeffries (5 February 1745 – 16 September 1819) was a Boston physician, scientist, and a military surgeon with the British Army in Nova Scotia and New York during the American Revolution. He is best known for accompanying Jean-Pierre Blanchard on his 1785 balloon flight across the English Channel. Born in Boston, Jeffries graduated from Harvard College and obtained his medical degree at the University of Aberdeen. Dr. Jeffries played a large role in the trial for the Boston Massacre as a witness for the defense. He was the surgeon for Patrick Carr, who was one of the
Hot air balloon course) stated in the previous section. Liftoff would require a slightly greater temperature, depending on the desired rate of climb. In reality, the air contained in the envelope is not all the same temperature, as the accompanying thermal image shows, and so these calculations are based on averages. For typical atmospheric conditions (20 °C, 68 °F), a hot air balloon heated to (99 °C, 210 °F) requires about 3.91 m³ of envelope volume to lift 1 kilogram (62.5 ft³/lb). The precise amount of lift provided depends not only upon the internal temperature mentioned above, but the external temperature, altitude above