In 1769 Biddle took an active part in the preparations made by the American Philosophical Society for the observation of the transit of Venus. With Joel Baily he was sent to Cape Henlopen, Delaware, with a large reflecting telescope borrowed from the Library Company. The expedition was described in the _Transactions of the American Philosophical Society_ in 1771 in an article entitled "An Account of the Transit of Venus, over the Sun's Disk, as observed near Cape Henlopen, on Delaware Bay, June 3rd, 1769 by Owen Biddle, Joel Baily and (Richard Thomas) Drawn by Owen Biddle." In addition to his trade in clocks and watches, Biddle also made mathematical instruments and was well known in his native city as a merchant, inventor, and ironmaster. Benjamin Banneker A name that is too often ignored in the history of science in colonial America is that of a free Negro, Benjamin Banneker (c. 1734-1806) of Baltimore. A farmer by occupation, Banneker was the son of a native African slave and a free mulatto woman. In his spare time he attended the school of a Quaker farmer; the only book he owned was the Bible. When he was a young man he acquired a watch from a trader, and from it he developed his love of science and instruments. Although he had never seen a clock, he constructed one based on drawings he made from the watch. Banneker was called upon to assist in the construction of the mills for the Ellicotts, and it was natural that his clock, which was the marvel of the Negro settlement, should come to the attention of Joseph Ellicott. Ellicott became interested in Banneker's thirst for knowledge and allowed him the use of his tools, scientific instruments, and technical books. Among the books were Mayer's _Tables_, James Ferguson's _Astronomy_, and Leadbeater's _Lunar Tables_. Banneker absorbed these and other works that he borrowed and went on to explore the wonderful new world they opened up for him. He pursued astronomical studies, and within three years he began to make calculations (fig. 12) for an almanac. After completing the calculations for the year 1791, he went on to produce a set of calculations for 1792. During this period he mastered the use of surveying instruments and made a firsthand study of tides in the region. His great opportunity came when Andrew Ellicott was chosen to make a survey for the city of Washington and hired Banneker as an assistant. While thus employed, Banneker completed his almanac and gave it to George Ellicott, Andrew's cousin, as a subject of possible interest. Apparently George Ellicott turned it over to the Honorable James McHenry of Baltimore, who in turned submitted it to the Philadelphia firm of Goddard & Angell, who published it (fig. 13). Banneker mailed a copy of his _Benjamin Banneker's Pennsylvania, Delaware, Virginia And Maryland Almanac and Ephemeris For the Year of Our Lord, 1792_ to Thomas Jefferson, who was so impressed with it that