XXXIII. Account of an observation of the right ascension and declination of Mercury out of the Meridian, near his greatest elongation, Sept. 1786, made by Mr. John Smeaton, F. R. S. with an equatorial micrometer, of his own invention and workmanship; accompanied with an investigation of a method of allowing for refraction in such kind of observations; communicated to the Rev. Nevil Maskelyne, D. D. F. R. S. and Astronomer Royal, and by him to the Royal Society