John Jeffries, an American physician, born in Boston, Feb. 5, 1744, died there, Sept. 16, 1819. He graduated at Harvard college in 1763, subsequently attended the medical schools of London, and in 1769 received from the university of Aberdeen the degree of M. D. Returning to Boston, he entered upon a lucrative practice, which continued until the evacuation of the town by the British troops, whom he accompanied to Halifax. After serving as surgeon general of the troops in Halifax, he was appointed in 1779 surgeon major of the forces in America, and was present for a short time with the army in Savannah. In the succeeding year he established himself in London in the practice of his profession, and with so much success that he declined the lucrative post of surgeon general to the forces in India. He also occupied himself much with scientific studies, and in the prosecution of his experiments in atmospheric temperature undertook, together with Francois Blanchard, Jan. 7, 1785, a remarkable voyage in a balloon from Dover cliffs across the British channel, landing in the forest of Guines in France. This was the first successful attempt at aerostation on an extended scale, and Dr. Jeffries in consequence received many attentions from the learned and scientific societies of Paris and from various eminent personages.

In 1789 he returned to Boston, where he practised his profession until the close of his life. He announced a course of lectures in Boston on anatomy, but such was the prejudice against dissection that on the evening of the second lecture a mob broke into his anatomical room and bore away the subject, the body of an executed felon presented to him by the'governor. The course was never resumed, and the single lecture delivered is said to have been the first public one on anatomy given in New England.