Fleuriais, Georges-Ernest, 1840-1895.

Transits of Venus are uncommon events, occurring only four times every 243 years, however in the eighteenth and nineteenth centuries, these rare events were of considerable practical importance to astronomers. Precise measurements of the timing and position of the planet as it passed across the disk of the sun offered the best means available to resolve one of the classic problems in observational astronomy: the determination of the distance from the earth to the sun,

The transit in 1769 was a formative event in the history of the American Philosophical Society, which helped to organize observations in North America and to coordinate the analysis and distribution of the data. Securing funding for equipment from the provincial government on the pretext that their observations would aid in improving navigation, the APS sponsored groups of observers at Cape Henlopen, N.J., the State House Yard in Philadelphia, and most famously at David Rittenhouse's estate in Norriton, Pa., making the Transit of 1769 one of the first examples of a truly cooperative, American scientific enterprise. The precision of the measurements made by these teams turned out in the long run to have been less important than the vehicle for disseminating them. Meeting a long-cherished goal of Benjamin Franklin, the Society published the results of the Transit observations in the first volume of its Transactions in 1771, making it the first scientific journal published in North America and the surest sign to Europeans of institutional maturity in the colonies.

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