Transit of Venus

One of only 11 surviving 1882 dry collodion emulsion plates from American expeditions sent to observe the Transit of Venus by the Naval Observatory and Transit of Venus Commission. Photo Credit: Photographic plates from the 1882 transit

The Transit of Venus was an astronomical event that took place on December 6, 1882 and was observed on the Trinity College campus.

A transit of Venus is a rare phenomenon in which Venus passes between the Earth and Sun, appearing as a black dot against the Sun's surface. A pair of transits takes place eight years apart in December followed by a gap of 121.5 years, before another pair occurs eight years apart in June, followed by another gap of 105.5 years. The last pairs of transits occurred on 8 June 2004 and 5/6 June 2012 and the next pair of transits will occur on 10–11 December 2117 and 8 December 2125. ¹⁾

On November 3, 1882, Trinity College became home to several distinguished German scientists and members of the German Commission, who were stationed at the College to track the transit of Venus on December 6. The astronomy team had chosen Trinity “because of the campus's superior elevation relative to the horizon,” as well as the campus' relative isolation to other buildings. ²⁾ During their stay, Dr. Gustav Mueller, assistant at the astrophysical observatory at Potsdam; Dr. Fritz Deischmueller, of the observatory at Bonn; Julius Bauschwiger, scientific assistant; and Herman Dolter, mechanician; lived in Seabury 18 and 19. They brought with them seven tons of equipment in 33 cases, constructed several small buildings, and utilized, among other instruments, thermometers, telescopes, refractors, a heliometer, and a collamator.

Buildings erected by the German scientists on the Trinity College Campus: Eastern Observatory, Heliometer House, Western Observatory. Wood engraving from Frank Leslie’s Illustrated Newspaper, December 16, 1882.

In addition to equipment, fickle New England weather played a role in the observations. Leading to the viewing, there was a 50 percent chance of rain, but by mid-morning “to the delight of everybody, the clouds disappeared and the sun shone forth with a dark spot on its lower portion.” The full observations of Venus' movement took four hours. Dr. Mueller stated, “How much fortune has favored us is seen from the fact that soon after the transit it became completely overcast, and during all the following day a strong snowstorm ravaged.” The team remained on campus for two more weeks, and departed on December 19. Dr. Arthur Auwers, President of the Imperial Commission, published a report on the transits, a copy of which resides in the Watkinson Library.

The Transit of Venus marker on its current site. Photo Credit: Amanda Matava, taken during the solar eclipse 4/8/2024.

The transit viewing garnered much publicity for Trinity, and the College placed an inscribed stone marker atop the concrete pier “on which stood the heliometer with which the transit of Venus was observed two years earlier.” It read:

Transit of Venus
December 6, 1882
Imperial German Commission
Lat. 41° 44' 47“ N
Lon. 4h, 50m, 46.4s W.

The Transit of Venus event led directly to the creation of the Astronomy department and building of St. John Observatory in 1884. The observatory was placed by the commemorative marker and torn down in 1938, after which the department atrophied.

Over the decades, the purpose of “the odd looking cube that [sat] in solitary splendor just west of Boardman Hall” was forgotten. As architect Robert O'Connor drew plans for the new Student Center in 1959, he noticed the marker stood in the path of construction and asked about its significance. Professor Theodore Lockwood, who had re-mounted the marker after it was removed during World War I due to anti-German sentiments, “prepared a place near Hallden Laboratory to which the stone marker [could] be moved,” having “taken measurements and planned the move so as not to lose the benefit of the accuracy of the original mark.” ³⁾ Today, the stone plaque is located in front of Hallden Hall. ⁴⁾

A pair of transits occurred in June 2004 and 2012, attracting visitors to campus once more.