Ezra Stiles and the Transit of Venus

Fri, 08/03/2018 - 11:37am -- baglio


Point Venus, Tahiti, by William Hodges. Credit: National Library of Australia.

In June of 1769, a major astronomical event enveloped the western world with excitement. The transit of Venus was a momentous occasion from one side of the globe to the next. Members of the Royal Society in London were sent to far off places to observe and record the event. Several Society members, under the lead of Charles Green were sent on an expedition with Lieutenant James Cook to observe the transit from Tahiti. There, from the observatory on land known as Point Venus, they observed the planet crossing the Sun, and took careful notes. King George III had a special observatory built so that he could watch the planets movement across the sun outside of London. His own personal observations were recorded. 

Other countries too became involved in the event: French Astronomer Jean-Baptiste Chappe d'Auteroche observed the transit from Spanish-held Baja California. Sadly, his viewing was marred with tragedy as many of his party, including d"Auteroche himself were lost to an outbreak of typhus. With d'Auteroche's, Green's, and others observations around the world, new understandings about the solar system, and the distance between the Earth and the Sun were made.

In the American Colonies, large efforts were made in Philadelphia and Providence to observe the the Transit of Venus as well. Here in Newport, a great effort was made by our librarian, Ezra Stiles, and his friends to take part in the twice in a lifetime event (the previous transit was only 8 years before, in 1761). From Stiles' diary, and other accounts, we get a good idea of how the occasion went down that June 3rd. Preceeding the event, Stiles was able to gain sponsorship from Abraham Redwood to purchase a sextant to use for the event, and for it to be used later by the library.  As efforts were underway in Providence, under Dr. Benjamin West, to also observe the transit, Government officials felt that the sextant would be better used there rather than in Newport. Through some maneuvering, and with aid from Peter Harrison, Stiles and friends were able to secure the scientific instrument.

Ezra Stiles House Credit: Wikipedia

The latitude of Newport was measured, and from Stiles' home on Clarke Street, the party anxiously waited for Venus to make its crossing in front of the sun. While three men (Stiles, William Vernon and one other) were observing from telescopes, two others were carefully watching clocks, so that when either Stiles or Vernon noticed Venus first appear, they could immediately mark the moment, and time how long it took for Venus to cross the sun. . In his diary, Stiles proudly wrote,

I was the first that espied Entrance. the other two soon saw it tho’ not till several after I gave the word. The moment of Immersion or first contact was seen by two of us Mr William Vernon & myself both gave the word the same Instant. We had two observers each of the clocks At Sunset Venus had passed the middle of the Transit in the Sun's Disk.

What Stiles doesn’t point out in his diary, that is later grumbled by others, is that Stiles failed to used the proper word for his friends to start watching the clocks! The practiced word to start timing the transit was “now”. However in his excitement, Stiles said, “take notice”, and the men watching the clocks were not prepared. Therefore their timing was off, and incorrect.

Ezra Stiles by Reuben Moulthrop. Credit: Redwood Library and Athenaeum

Around the world, June 3rd 1769 was a defining moment for Astronomy. The next transit of Venus would not occur again until 1874, but until then Ezra Stiles, and many others could proudly say that they observed the transit with their own eyes.