The first of these, in the order of time, was our Astronomer’s newly-projected Orrery; a general but concise description of which, was communicated by his friend, the Rev. Dr. Smith, to the Philosophical Society, on the 21st of March, 1768. Of this fine and eminently useful piece of mechanism, more particular mention shall be made in the sequel. The other circumstance, just referred to, was the then approaching Transit of Venus over the Sun’s disk; an event which was to take place on the 3d day of June, 1769: And of Mr. Rittenhouse’s participation in the arduous labours of the astronomical world, on that very interesting occasion, the following narrative will furnish some account. The American Philosophical Society, in their meeting on the 7th of January, 1769, had appointed the following gentlemen to observe that _rare phænomenon_,[108] as it was aptly styled by Dr. Smith; namely, the. Rev. Mr. (afterwards Dr.) John Ewing, Mr. Thomas Prior, Joseph Shippen, jun. Esq., Hugh Williamson, M. D., the Rev. Dr. Smith, Mr. David Rittenhouse, John Lukens, Esq. and Messrs. James Alexander, Owen Biddle, James Pearson, John Sellers, Charles Thomson, and William Poole. The gentlemen thus nominated were distributed into three committees, for the purpose of making separate observations at three several places; these were, the city of Philadelphia, Mr. Rittenhouse’s residence, in Norriton, and the Light-House near Cape Henlopen, on Delaware Bay. Dr. Ewing, an able mathematician and very respectable astronomer, had the principal direction of the Observatory in the City, which was erected on this occasion in the State-house Gardens; and Mr. O. Biddle, a person of much ingenuity, had the charge of superintending the observations at Cape Henlopen. Associated with Mr. Rittenhouse, on the Norriton committee, were the Rev. Dr. Smith, provost of the College of Philadelphia, well known as an astronomer and eminently skilled in the mathematics; Mr. Lukens, then surveyor-general of Pennsylvania, who possessed considerable abilities in the same departments of science; and Mr. Sellers, a respectable member of the provincial legislature, for the county of Chester. The Rev. Mr. Barton, with some other gentlemen of ingenuity and talents, voluntarily attended at Norriton, on this occasion; and rendered such assistance as they could, to the committee. ----- Footnote 108: