These qualities, and probably his near connection with Mr. Martyn, recommended Mr. Hitchins as an assistant to Mr. Benjamin Donne in constructing a map of Devonshire, an occupation decisive of his future life, for at Bideford he became acquainted with Miss Hockin, whom he married, and acquiring with her an accession of fortune, he proceeded to Oxford, and became a member of Exeter College, with the view of obtaining orders. But Mr. Hitchins possessed talents and acquirements that could not admit of his remaining undistinguished at a place of learning. He was soon noticed by the mathematicians, and recommended to the Reverend Nevil Maskelyne, Astronomer Royal, to assist him at the Royal Observatory; and when Doctor Maskelyne went to St. Helena, in the year 1761, to observe the transit of Venus, and to ascertain, if it were possible, the parallax of Sirius, Mr. Hitchins had the whole care of the Observatory entrusted to his hands. Another object of Doctor Maskelyne’s voyage, and one eventually of by far the greatest importance, was to prove from actual experience that Longitudes at sea might be derived from observations on the moon. Tables founded on the theory of gravitation and of inertia, as laid down by SIR ISAAC NEWTON, had then been constructed by Tobias Mayer, of Gottingen, and communicated to Dr. Maskelyne in manuscript, representing the moon’s place at all times in the heavens, within narrow limits; and the admirable instrument invented by Mr. John Hadley, by rendering the apparent contact of two objects, independent of all agitations of the instrument itself, enabled observers to ascertain the distance of the moon from the sun, or from a star, almost as accurately on board a ship as on the solid land. With these assistances the determination of a ship’s longitude became an easy problem. The moon is converted into the hand of a clock, indicating by its distance from a particular star, the time at Greenwich Observatory made the first meridian. This distance is ascertained by Hadley’s sextant, and after applying certain corrections for parallax and refraction, the time at Greenwich becomes known. The actual time at the place of observation is then determined from the altitude of some celestial body, and thus differences in the longitude required.