This was a period of intense interest, and many expeditions were fitted out to observe the transit at different places in both the northern and southern hemispheres.
Mason and Dixon, the English astronomers, who gained undying fame as the surveyors of the boundary line between Pennsylvania and Maryland, started on a ship of war for their station on the southern hemisphere, but they were attacked by a French frigate and were compelled to return to port after a severe battle. Other expeditions became celebrated through the adventures to which they gave rise.
The transit of 1769 was visible in the Atlantic States and observations upon it were made under the auspices of the American Philosophical Society at Philadelphia. The most celebrated of all these observers was David Rittenhouse.
Benjamin Franklin had organized the society and in 1769 became the society’s first president. He was annually elected to that position for twenty-two years, being succeeded in 1791 by another Pennsylvanian, David Rittenhouse.
In 1768 the American Philosophical Society petitioned the Assembly of Pennsylvania for assistance to observe the transit of Venus, and the proposition was treated with liberality.
One hundred pounds was granted to enable the society to procure a reflecting telescope of two and a half or three feet focus and a micrometer of Dolland’s make, which had to be procured from England. They were purchased there by Dr. Franklin.
The society erected a wooden building as an observatory in the State House yard. This was of circular shape, and about twenty feet high, twelve to fifteen feet square and placed about sixty feet south of the State House.
On the morning of June 3 the sky was cloudless. The transit was observed from this building in the State House yard by Dr. John Ewing, Joseph Shippen, Dr. Hugh Williamson, Thomas Prior, Charles Thomson and James Pearson.
While they were thus engaged, David Rittenhouse, Dr. William Smith, John Sellers and John Lukens noticed the phenomena at Norriton, the home of the celebrated astronomer. Owen Biddle made an observation at Henlopen lighthouse.
Rittenhouse was already a member of the American Philosophical Society and made his observations for that society. He used a telescope and other instruments made by his own hands.