Apparatus for Astronomy, Geodesy, and Surveying.
No event or series of events marks more strikingly the advent of modern science than the invention of the telescope and the microscope. Both came into general use in the course of the seventeenth century, revealing hitherto unimagined wonders in the macro- and microcosmos, and stimulating the mind of the experimentalist in directions which were to lead to a new view of nature. The impetus given to scientific investigation by this extension of vision was far from spent when the American Philosophical Society assembled, and the exploitation of the possibilities of the telescope was one of the earliest concerns of the Society.
Its formation coincided with the approach of a long awaited scientific event, the transit of Venus of 1769. By the middle eighteenth century the gross discoveries made possible by simple observation through the telescope had been accomplished, and astronomers had advanced to more subtile questions. Kepler and Newton had shown the planets to be subject to mathematically definable laws, and the telescope had been adapted to the determination of the angular measurements upon which those laws depended. Transits of the inferior planets, such as Venus, across the face of the sun, provided a method of determining the value of solar parallax, from which its distance could be more precisely determined. It was generally recognized that the transit of 1769 would provide a rare opportunity to collect data on this problem, and European astronomers made an unprecedented effort to promote observations from sites around the world. Participation in this international project was the first important scientific enterprise of the Society, and observations were made by members from Philadelphia, Norriton (the home of David Rittenhouse), and Cape Henlopen, Delaware. The results were published in the first volume of the Transactions.