John Jeffries, a colonial physician, is known for his balloon flight across the English Channel with Jean-Pierre-Françoise Blanchard in 1785. Their first major ascent, on Nov. 30, 1784, was a notable event in London, observed by the Prince of Wales and the Duchess of Devonshire. Jeffries' aim was to conduct a scientific study of the atmosphere, for which he used a thermometer, barometer, electrometer, and hygrometer (not to mention a compass and telescope for navigation). He also carried several bottles filled with distilled water, which he emptied at different elevations and then closed with glass stoppers to capture air at those levels. Twelve observations of temperature, pressure, and humidity were made. The experiment, suggested by Henry Cavendish, provided the first scientific data on air from sea level to more than 9,000 feet. Results from the chemical analysis performed by Cavendish correspond to currently accepted values.
Jeffries is best known, however, for his flight with Blanchard from Dover to France on Jan. 7, 1785. The Channel crossing was uneventful initially, but a third of the way across, the balloon lost altitude. Dropping the sand ballast restored buoyancy, but two thirds of the way across the Channel, the balloon began falling again. Food, supplies, instruments, the two balloonists' coats, and Blanchard's trousers were thrown overboard, and once more the balloon rose. Then over France, it descended toward a forest. Discharging 5 or 6 lb from the “secretions of their kidneys” allowed the flight to continue to a site near Ardres in the forest of Guines. The balloonists were received enthusiastically in Calais and subsequently in Paris. At Passy, Jeffries dined with Benjamin Franklin and met Commander John Paul Jones. Jeffries' account of the flight and of his scientific observations was read to the Royal Society of London.
John Jeffries was born on Feb. 5, 1744 or 1745, in Boston. He graduated from Harvard University in 1763 and then studied medicine under a preceptor, Dr. James Lloyd, whose other apprentice was the patriot Joseph Warren. Jeffries received an M.D. degree from Marischal College, Aberdeen, Scotland, in 1769. He returned to Boston and practiced medicine until 1771, when he became an assistant surgeon in the British navy. Evacuating Boston with the British, Jeffries went to Halifax, served as a surgeon in various English military hospitals, and then accompanied British troops in the campaigns at Savannah, Georgia, and Charleston, South Carolina. He subsequently sold his commission and returned to England, where he practiced medicine from 1780 to 1789. There he became interested in balloons and financed (at a price of 100 guineas) and participated in the well-known balloon flights with Blanchard.
After inheriting property in Boston, Jeffries returned to that city in 1790 and established a large medical practice. He initiated the first Boston lecture course in anatomy (which was terminated when his cadaver was seized by a mob) and was one of the founders of the Boston Medical Library. Jeffries died in Boston on Sept. 16, 1819, from a strangulated hernia. He was honored on a stamp issued by Vanuatu in 1983 for his crossing of the English Channel in 1785.
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