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Chasing Venus: Observing the Transits of Venus 1631-2004
Introduction
What is a Transit of Venus?
Discovering the Transits: The 1631 and 1639 Transits
Measuring the Universe: The 1761 and 1769 Transits
New Possibilities: The 1874 and 1882 Transits
The Transits of 2004 and 2012
Credits and Financial Support
Education and Events
Resources and Links
~ Return to Exhibition
Chasing Venus: Observing the Transits of Venus, 1631-2004

John Philip Sousa and the Transit of Venus


John Philip Sousa in uniform as the leader of the U.S. Marine Band
c. 1892.
Courtesy of "The President's Own" U.S. Marine Band, Washington, DC

John Philip Sousa in uniform as the leader of the U.S. Marine Band



John Philip Sousa and the Transit of Venus


Joseph Henry statue in front of Smithsonian "Castle"

Smithsonian Institution

Joseph Henry statue in front of Smithsonian

As a memorial to Joseph Henry, the first Secretary of the Smithsonian Institution, a statue in his honor (which now stands in front of the Smithsonian “Castle”) was unveiled on April 19, 1883, shortly after the 1882 transit. The music you hear was composed for the ceremony by the legendary U.S. Marine Corps bandmaster John Philip Sousa. This march is called “The Transit of Venus,” in honor of Henry’s service on the original U.S. Commission on the Transit of Venus.

Transit Expeditions in the 19th Century


Glass-plate negative photographs of the 1882 transit of Venus taken by one of the U.S. Naval Observatory expeditions

Courtesy of the U.S. Naval Observatory Library

Glass-plate negative photographs of the 1882 transit of Venus taken by one of the U.S. Naval Observatory expeditions

These eleven plates are the only surviving original photographs of the 1,700 taken by the 1882 U.S. expeditions. None of the 350 plates from the 1874 expeditions has survived.

These are negative images, so Venus appears as a large white dot on the black solar disk. Because measurements would be taken directly from the photographic plate, it was important to ensure that the image was not distorted in any way. A rectangular grid placed in front of the plate was photographed as a check to make sure the image did not shrink or warp. A second vertical line in the center is an image of a wire on a plumb bob used as a reference point for measurements.


Transit Expeditions in the 19th Century


U.S. Naval Observatory observing station in Nagasaki, Japan, 1874
1874.
Courtesy of the U.S. Naval Observatory Library

U.S. Naval Observatory observing station in Nagasaki, Japan, 1874

Many of the objects in this exhibit are representative of those used at this observation station. A Stackpole transit instrument was housed in the shed at the left foreground. A 5-inch telescope like the one at the gallery’s entrance was stored in the center shed. The camera used to produce glass-negative photographs was in the shed at right.

Transit Expeditions in the 19th Century


U.S. Naval Observatory staff at the observing station on Kerguelen Island, 1874
1874.
Courtesy of the U.S. Naval Observatory Library

U.S. Naval Observatory staff at the observing station on Kerguelen Island, 1874

Prior to the transit of Venus, observatory staff performed trial runs with the photoheliograph (far right), the instrument used to photograph the Sun. During the transit it directed the Sun's image through a lens and onto a photographic plate in a dark shed about 40 feet away. The photoheliograph produced the glass-plate photographs on display in this exhibition gallery

Transit Expeditions in the 19th Century


Observation station at the 1876 Centennial Exposition
1876.
Courtesy of the U.S. Naval Observatory Library

Observation station at the 1876 Centennial Exposition

The U.S. Naval Observatory recreated the experience of observing the 1874 transit of Venus for the American public by setting up one of its eight observation stations at the Centennial Exposition in Philadelphia, Pa.

Transit Expeditions in the 19th Century


Testing the equipment at the 1874 American transit-of-Venus observation station on Kerguelen Island
1874.
Courtesy of the U.S. Naval Observatory Library

Testing the equipment at the 1874 American transit-of-Venus observation station on Kerguelen Island



Transit Expeditions in the 19th Century


Members of the U.S. transit-of-Venus expedition at the site of Kerguelen Island putting up the water casks at the photography building
1874.
Courtesy of the U.S. Naval Observatory Library

Members of the U.S. transit-of-Venus expedition at the site of Kerguelen Island putting up the water casks at the photography building



Transit Expeditions in the 19th Century


Boxes containing records of the 1874 U.S. Naval Observatory transit-of-Venus expeditions
1874.
Courtesy of the U.S. Naval Observatory Library

Boxes containing records of the 1874 U.S. Naval Observatory transit-of-Venus expeditions

The United States sent eight expeditions around the world to observe the 1874 transit of Venus. These boxes were constructed to house the observation record books. The various logs and data books include details of each photograph taken at each visual observation of the transit, latitude and longitude measurements, and other pertinent observational data.

Mobilizing for the 1761 and 1769 Transits


Encyclopedie, ou Dictionnaire raisonne des sciences, des arts et des metiers (Encyclopedia or descriptive dictionary of the sciences, arts, and trades, plate volume XII)
Paris: Chez Panckoucke et al., 1777.
Smithsonian Institution Libraries

Encyclopedie, ou Dictionnaire raisonne des sciences, des arts et des metiers

The famous Encyclopédie was one of the great products of the French Enlightenment and one of the great achievements in the history of printing and publishing. This illustration shows a small telescope of the kind that might be used to observe the transit of Venus on an expedition. A piece of dark glass would be placed in front of it to reduce the intensity of the sunlight.

New Possibilities: 1874 and 1882


Observations of the transit of Venus, 9 December, 1874 : made at stations in New South Wales
Sydney: C. Potter, 1892.
Courtesy of the U.S. Naval Observatory Library

Observations of the transit of Venus, 9 December, 1874 : made at stations in New South Wales

Australia was well situated for observing the 1874 transit. There were eight local observers in the colony of New South Wales, and H.C. Russell, the director of the Sydney Observatory, brought together their work in this beautiful book. It was not published until 1892 because Russell had difficulties organizing the work of the eight independent people involved.

When Venus is near the inner edge of the Sun’s disk, its edge appears to smear and make a hazy connection with the solar disk. This makes Venus look like a black drop dripping off the edge of the Sun. This smearing prevented astronomers from timing accurately the moment when Venus made “contact” with the edge of the Sun, dooming any chance of obtaining an accurate measure of the Earth-Sun distance.


Transit Expeditions in the 19th Century


Recueil de mémoires, rapports et documents relatifs à l'observation du passage de Vénus sur le soleil (Collection of memoirs, reports, and documents relating to the obsrvations of the transit of Venus, volum III, part II, atlas of plates)
Paris: Gauthier-Villars, 1885.
Courtesy of the U.S. Naval Observatory Library

Recueil de mémoires, rapports et documents relatifs à l'observation du passage de Vénus sur le soleil

The French government sent major expeditions to Yokohama, Beijing, St. Paul’s Island, and Campbell Island in 1874. After their recent defeat in the Franco-Prussian War, this effort no doubt helped boost national morale. Besides observing the transit, the French also studied the zoology and geology of their observation sites. This volume is open to cross-sections of rocks found on Campbell Island, 400 miles south of New Zealand.

New Possibilities: 1874 and 1882


"The transit of Venus". Scientific American, Volume XXXI, no. 8, August 22,
New York: Munn & Co., 1874.
Smithsonian Institution Libraries

Scientific American, Volume XXXI, no. 8, August 22,

This article reflected American popular scientific interest in the transit of 1874. Besides discussing details of the transit, it also boasted of the American effort: “It is generally admitted that the United States has shouldered the most difficult share of the work, not only in appropriating the largest sum, but in accepting the most difficult [observing] stations.”

The Many Faces of Venus


Images of Venus: UV Image of Venus Showing Cloud Patterns.

Courtesy of NASA/JPL/Caltech

Images of Venus: UV Image of Venus Showing Cloud Patterns.

Although Venus is the closest planet to Earth, it has long remained a mystery due to the thick clouds that completely hide its surface.

The Many Faces of Venus


Images of Venus: Venus in Transit

Courtesy of the U.S. Naval Observatory Library

Images of Venus: Venus in Transit

Although Venus is the closest planet to Earth, it has long remained a mystery due to the thick clouds that completely hide its surface.

The Many Faces of Venus


Images of Venus: The Surface of Venus

Courtesy of NASA/JPL/Caltech

Images of Venus: The Surface of Venus

Although Venus is the closest planet to Earth, it has long remained a mystery due to the thick clouds that completely hide its surface.

The Many Faces of Venus


Images of Venus: Venus in Visible Light

Courtesy of NASA/JPL/Caltech

Images of Venus: Venus in Visible Light

Although Venus is the closest planet to Earth, it has long remained a mystery due to the thick clouds that completely hide its surface.

Transit Expeditions in the 19th Century


Glass-plate negative boxes used during the 1882 transit of Venus expeditions by the U.S. Naval Observatory

Courtesy of the U.S. Naval Observatory Library

Glass-plate negative boxes used during the 1882 transit of Venus expeditions by the U.S. Naval Observatory

Boxes used to house glass-plate negatives taken by the 1882 U.S. expeditions.

Transit Expeditions in the 19th Century

George Biddell Airy, editor (1801-1892)
Account of observations of the transit of Venus, 1874, December 8
London: Her Majesty's Stationery Office, 1881.
Courtesy of the U.S. Naval Observatory Library

Account of observations of the transit of Venus, 1874, December 8

Airy, the British Astronomer Royal, collected the results of the British observations of the transit into this volume. The British used a different photographic method than the Americans, and it failed spectacularly. The British and Germans were so disappointed that they resolved not to use photography for the 1882 transit. This book illustrates that these observations were also plagued by the infamous black drop effect.

Transit Expeditions in the 19th Century

Alvan Clark & Sons
Refracting telescope with 5-inch objective lens
Boston: 1874.
Courtesy of the U.S. Naval Observatory

Refracting telescope with 5-inch objective lens

Invented in the early 1600s, telescopes enabled astronomers to see the transits of Venus, which are nearly impossible to see with the unaided eye.

This telescope is one of eight identical models built expressly for the U.S. Naval Observatory’s expeditions to observe transits of Venus in the 19th century.


Hunting the Astronomical Unit

Aristarchus of Samos
De magnitudinibus, et distantiis solis, et lunae (On the sizes and the distances of the Sun and the Moon)
Pisa: Camillo Fanchischini, 1572.
Gift of the Burndy Library

De magnitudinibus, et distantiis solis, et lunae

In the third century B.C., the Greek mathematician Aristarchus reasoned that, if you measured the angle between the Sun and the Moon when the Moon was exactly half-full, you could determine the Earth-Sun distance geometrically. His method demanded great accuracy. Aristarchus, lacking such precision, concluded that the Sun was 4 million miles away. This is the first appearance of his work in print, translated into Latin by Federico Commandino.

The Perils of Chasing Venus

Artist Unknown
Portrait of Jean Chappe d’Auteroche



Portrait of Jean Chappe d’Auteroche

For the 1769 transit, Jean Chappe d’Auteroche led a party to the southern tip of Baja California. They observed the transit under ideal conditions, but a few days later an epidemic struck the area, killing three-fourths of the local population and everyone in the expedition except for Chappe and Pauly, his engineer. Chappe lingered for a short while but died before leaving Baja. Pauly managed to get back to France with all of the observation records

Mobilizing for the 1761 and 1769 Transits

Johann Elert Bode (1747-1826)
Deutliche Abhandlung … von dem bevorstehenden merkwürdigen Durchgang der Venus… (Clear treatise on the forthcoming remarkable transit of Venus)
Hamburg: Dieterich Anton Harmsen, 1769.
Courtesy of the U.S. Naval Observatory Library

Deutliche Abhandlung … von dem bevorstehenden merkwürdigen Durchgang der Venus…

In preparation for the 1769 transit, the German astronomer Bode produced this short work providing details on the previous transit observations and a map of places where the 1769 transit would be visible. In the pink area, the transit would be visible in its entirety. Green indicates where observers would see only the beginning of the transit, while yellow shows where they would see only the end.

Mobilizing for the 1761 and 1769 Transits

John Singleton Copley (1738-1815)
Portrait John Withrop
c. 1773.
Courtesy of the Harvard University Portrait Collection, Gift of the executors of the Estate of John Winthrop, grandson, 1894

Portrait John Withrop

Winthrop was Hollis Professor of Mathematics and Natural Philosophy at Harvard University. Copley, the preeminent painter in Boston at the time, captured the importance of Winthrop’s interest in the transit of Venus. Winthrop is shown next to the telescope with which he may have viewed the 1769 transit. He is pointing to a diagram of the transit (compare it to the one in his book) and the landscape corresponds to that of his 1761 observing site (“Venus’s Hill”) in Newfoundland.

Discovering the Transits of Venus

Eyre Crowe (1824-1910)
Jeremiah Horrocks Watching the Transit of Venus in 1639
1891.
Courtesy of National Museums Liverpool (The Walker)

Jeremiah Horrocks Watching the Transit of Venus in 1639

Crowe painted this picture 250 years after Horrocks’s death. Horrocks and his telescope are depicted according to Victorian tradition and astronomical practice. Horrocks was not a sickly Puritan curate, and his equipment would have been set up in a similar way to Crabtree’s.

Transit Expeditions in the 19th Century

Franscisco Díaz Covarrubias (1833-1889)
Viaje de la Comision Astronómica Mexicana al Japon : para observar el tránsito del planeta Vénus… (Voyage of the Mexican Astronomical Commission to Japan to observe the transit of Venus)
Mexico City: C. Ramiro y Ponce de Leon, 1876.
Courtesy of the U.S. Naval Observatory Library

Viaje de la Comision Astronómica Mexicana al Japon : para observar el tránsito del planeta Vénus…

The Mexican republic had been restored in 1867 when Benito Juárez deposed the French interlopers. After Juárez’s death in 1872, the new president, Lerdo de Tejada, devoted himself to rebuilding the country’s international reputation. This effort included sending a Mexican expedition to Yokohama to observe the 1874 transit and strengthen Mexican ties with Japan. Diaz Covarrubias’s report helped acquaint Mexicans with Japanese history, culture, and customs.

To the Ends of the Earth

Samuel Dunn (d. 1794)
"A Determination of the exact Moments of Time when the Planet Venus was at external and internal contace with the Sun's Limb…,". Philosophical transactions of the Royal Society of London
London: Lockyer Davis, 1771. Volume LX (1770)
Smithsonian Institution Libraries

Philosophical transactions of the Royal Society of London

Dunn’s observations reveal why accurate measurements of the exact moment of contact were impossible. His drawings show how the edge of Venus appeared to smear instead of remaining sharply defined as it approached the Sun. This phenomenon, known as the black drop effect, played havoc with the transit observer’s measurements.

Transit Expeditions in the 19th Century

E. Howard Clock Company
Mercury pendulum clock
Boston: 1874.
Courtesy of the National Museum of American History

Mercury pendulum clock

This is one of eight identical clocks ordered by the US Naval Observatory for the 1874 transit-of-Venus expeditions. Designed to withstand the rigors of a long voyage, they cost $275 each. The Campbell Town, Tasmania, observers used this one. With this clock and the Stackpole transit instrument, they could determine the precise latitude and longitude of the observing site, critical for an accurate transit-of-Venus observation.

New Possibilities: 1874 and 1882

George Forbes (1849-1936)
transit of Venus
London, New York: Macmillan and Co., 1874.
Smithsonian Institution Libraries

transit of Venus

Forbes’s treatise was one of many to bring the transit of Venus to popular attention. It consisted of a history of the observations, a discussion of how to find the Earth-Sun distance from a transit, and plans for the 1874 transit. He placed great emphasis on the British expeditions to Egypt, Hawai’i, Rodrigues Island, Kerguelen Island, and New Zealand, but discussed the German, Russian, French, American, Dutch, and Italian expeditions as well.

Discovering the Transits of Venus

Pierre Gassendi (1592-1655)
"Mercurius in sole visus & Venus invisa". Opera omnia (Mercury seen upon the Sun & Venus unseen)
Florence: Typis Regiæ Celsitudinis …, 1727. Volume 4
Gift of the Burndy Library

Opera omnia

Gassendi, a French astronomer, was one of a few witnesses of the first recorded planetary transit—Mercury’s on November 7, 1631. He shows Mercury’s path across the Sun as a series of black dots. Gassendi noted that the predicted transit of Venus one month later did not occur. Kepler’s tables had neglected to indicate that the transit would take place after the Sun had set for European observers.

Mobilizing for the 1761 and 1769 Transits

George Adams
Gregorian reflecting telescope
London: c. 1750-1800.
Courtesy of the National Museum of American History, Behring Center

Gregorian reflecting telescope

Unlike the telescope at the gallery’s entrance, this telescope uses mirrors, not lenses, to gather the light from stars and planets. It was originally developed by James Gregory in 1663, but improvements made it practical around 1740. Reflecting telescopes could be made much smaller than the lens-based telescopes of the time. Their smaller size made them easier to take on distant expeditions to see the 1761 and 1769 transits of Venus.

To the Ends of the Earth

Charles Green ; Cook, James (1728-1779)
"Observations made … at King George's Island [Tahiti] in the South Sea". Philosophical Transactions of the Royal Society of London, vol. LXI. For the year 1771
London: Lockyer Davis …, 1772. Volume LXI (1771)


Philosophical Transactions of the Royal Society of London, vol. LXI. For the year 1771

Perhaps the most famous observer of the transit of Venus was Captain James Cook. The primary purpose of his first voyage to Tahiti was to witness the 1769 transit. Cook was experienced in nautical astronomy and received additional training from Green, the expedition astronomer. This article shows Cook’s drawings of the transit. In them, you can clearly see the black drop problem.

Hunting the Astronomical Unit

Edmond Halley (1656-1742)
"Methodus singularis qual Solis Parallaxis sive distantia a Terra (Remarkable method for determining the solar parallax of the distance from the Sun to the Earth)". Philosophical Transactions of the Royal Society of London
London: W. Innys, 1717. Volume 29
Smithsonian Institution Libraries

Philosophical Transactions of the Royal Society of London

After working on the problem for nearly forty years, Halley announced in this article the final details of his method for measuring the value of the AU from transit-of-Venus observations. By this time, Halley’s reputation was so great that astronomers took notice of his plea for scientists everywhere to make numerous observations of the transit of 1761. This article was the most important published work that brought about the surge of interest in the transit of Venus.

Hunting the Astronomical Unit

Edmond Halley (1656-1742)
Catalogus stellarum australium (Catalogue of the southern stars)
London: T. James, 1679.
Gift of the Burndy Library

Catalogus stellarum australium

In 1676 the English astronomer Halley traveled to the remote South Atlantic island of St. Helena for one year to observe stars in the southern skies that were not visible in England. While there he witnessed the 1677 transit of Mercury and realized that transits might be useful for finding the Earth-Sun distance. He first published his idea in his catalogue of the stars located near the south celestial pole.

To the Ends of the Earth

John Hawkesworth (1715?-1773)
account of the voyages undertaken … for making discoveries in the Southern Hemisphere…
London: W. Strahan and T. Cadell, 1773. Vol. II
Gift of the Burndy Library

account of the voyages undertaken … for making discoveries in the Southern Hemisphere…

Hawkesworth’s well-known accounts of Cook’s voyages helped publicize a new era of exploration. This account of the first voyage includes a map of Tahiti (or “Otaheite”). At the top of the main island, you can see “Point Venus,” where Cook and Green observed the 1769 transit of Venus.

When Captain Samuel Wallis of the Swallow returned to England in 1768 and told everyone about the island of Tahiti, many agreed that it would be the best place to see the 1769 transit.



Hunting the Astronomical Unit

Johannes Hevelius (1611-1687)
Machinæ coelestis (Celestial Machines)
Gdansk: by the author, 1673.
Gift of the Burndy Library

Machinæ coelestis

The astronomers Johannes and Elisabetha Hevelius using their sextant at their private observatory in Gdansk.

17th-century astronomers used instruments like this to determine the parallax—the apparent shift of a planet’s position caused by observing it from different locations—of Mars in order to find a value for the Earth-Sun distance.


Discovering the Transits of Venus

Johannes Hevelius (1611-1687)
Mercurius in Sole visus (Mercury seen upon the Sun)
Gdansk: by the author, 1662.
Gift of the Burndy Library

Mercurius in Sole visus

Kepler thought that Venus would pass below the Sun in 1639, but Jeremiah Horrocks calculated that it would indeed transit the Sun. Consequently, Horrocks and his friend William Crabtree were the first witnesses of a transit of Venus. Unfortunately, because Horrocks died suddenly in 1641, his observations went unpublished until 1662, when the astronomer Hevelius, in his book on the 1661 transit of Mercury, printed Horrocks’s work for the first time.

Discovering the Transits of Venus

Jeremiah Horrocks (c. 1617-1641)
Transit of Venus across the Sun
London: William Macintosh, 1859?.
Gift of the Burndy Library

Transit of Venus across the Sun

Horrocks, a gifted English astronomer and mathematician, might be better remembered if he had not died in his early twenties. When he predicted the 1639 transit of Venus, he lived in Hoole, north of Liverpool, and set up his telescope in his home to watch the transit on December 4. Not sure of the precise time of the transit, he checked the Sun regularly. At 3:15 PM he saw Venus as a “spot of unusual magnitude and of a perfectly circular shape” on the Sun. This translation of Horrocks’s posthumously published Latin work, is open to the pages where he tells of his first sight of the transit.

Hunting the Astronomical Unit

James Giles
Orrery
London: 1740-80.
Courtesy of the National Museum of American History, Behring Center

Orrery

The first orrery, or model that simulates the motions of the planets around the Sun, was made in 1713 for the Earl of Orrery. These models were made primarily as educational aids and conversation pieces. While the true size of the solar system was still a mystery at this time, by the early 1700s people basically understood its arrangement and relative proportions

Discovering the Transits of Venus

Johannes Kepler (1571-1630)
Tabulæ Rudolphinæ (Rudolphine Tables)
Ulm: J. Saurii, 1627.
Gift of the Burndy Library

Tabulæ Rudolphinæ

The Rudolphine tables (named for the Holy Roman Emperor Rudolf II) were the crowning achievement of Kepler’s career. These astronomical tables allowed astronomers to compute the positions of the planets, and Kepler used them to predict the 1631 transit of Venus. Kepler is pictured in the panel at the bottom left of this illustration, which depicts an allegorical temple of the heavens built on the foundations of the great astronomers’ works.

The Perils of Chasing Venus

Guillaume Le Gentil de La Galaisiere (1725-1792)
Voyage dans les mers de l'Inde
Paris: deI'Imprimerie Royale, 1779.
Courtesy of the U.S. Naval Observatory Library

Voyage dans les mers de l'Inde

Guillaume Le Gentil de la Galaisière traveled to India to observe the 1761 transit from the French colony of Pondicherry. Before he arrived, the British captured the colony, forcing Le Gentil to return to the French island of Mauritius. He did not get there in time to observe the transit. Rather than return home, he studied the Indian Ocean cultures, planning to watch the 1769 transit from Manila in the Philippines. But he was ordered back to Pondicherry, again under French control.

While Manila had beautiful weather during the transit, it rained in Pondicherry. Le Gentil missed both transits. When he returned home in 1771, he learned that he had been declared dead. After many expensive legal battles, Le Gentil managed to prove he was actually alive.


Hunting the Astronomical Unit

Guillaume Le Gentil de La Galaisiere (1725-1792)
"De la conjunction inferieure de Venus avec le Soleil (On the inferior conjunction of Venus with the sun)". Histoire de l' Academie Royale des sciences, annee 1753
Paris: deI'Imprimerie Royale, 1757.
Smithsonian Institution Libraries

Histoire de l' Academie Royale des sciences, annee 1753

French astronomer Le Gentil, who worked at the royal observatory in Paris, downplayed the worth of observing transits of Mercury in determining the Earth-Sun distance. His article was critical in raising French support for observations of the transits of Venus in 1761 and 1769, using Delisle’s improved method. An inferior conjunction of Venus (when Venus passes between Earth and the Sun) happens every 584 days.

Mobilizing for the 1761 and 1769 Transits

Nevil Maskelyne (1731-1811)
Instructions relative to the observations of the ensuing transit of the planet Venus. . .
London: W. Richardson and S. Clark, 1768.
Gift of the Burndy Library

Instructions relative to the observations of the ensuing transit of the planet Venus. . .

Maskelyne, an English astronomer, traveled to St. Helena in the South Atlantic to observe the 1761 transit, but was cursed with overcast skies. Seven years later, Maskelyne, by this time the Astronomer Royal, wrote to encourage people with the proper equipment to observe the 1769 transit, providing detailed instructions in how to make an observation of real scientific value.

To the Ends of the Earth

Charles Mason (1730-1787) ; Dixon, Jeremiah d. 1777
"Observations made at the the Cape of Good Hope". Philosophical transactions of the Royal Society of London
London: L. Davis and C. Reymers, 1762. Volume LII (1761)
Smithsonian Institution Libraries

Philosophical transactions of the Royal Society of London

Before the English astronomers Mason and Dixon surveyed the boundary between Maryland and Pennsylvania (the Mason-Dixon Line), they were sent to Sumatra to observe the 1761 transit of Venus. England was at war with France. On the voyage a French ship attacked them, killing some of the crew. Quite shaken, Mason and Dixon were persuaded to continue but, running short of time, they had to stop in South Africa, where they had good observing conditions.

To the Ends of the Earth

David Rittenhouse (1732-1796) ; and others
"An account of the Transit of Venus…". Transactions of the American Philosophical Society
Philadelphia: R. Aitken & Son, 1789. vol. I, 2d ed. Corrected


Transactions of the American Philosophical Society

The noted American astronomer, surveyor, and clockmaker Rittenhouse was one of many colonists who observed the 1769 transit of Venus. Members of the newly founded American Philosophical Society in Philadelphia observed the transit at Rittenhouse’s home in nearby Norriton. They purchased astronomical instruments with money from the Pennsylvania governor and provincial assembly, and published their observations in the first volume of their Society’s journal.

Discovering the Transits of Venus

Christoph Scheiner (1575-1650)
Rosa Ursina (The Rose of Orsini)
Bracciani: Andream Phæum, 1630.
Gift of the Burndy Library

Rosa Ursina

Scheiner, a Jesuit in Italy, was an expert at studying the Sun and a vocal opponent of Galileo. In this book (titled after his patron, the Duke of Orsini, whose family emblem was the rose), Scheiner shows how to view the Sun indirectly using a telescope. Pointing the telescope at the Sun and letting the image shine through the eyepiece to focus on a white screen was the preferred 17th-century way of observing the Sun, including transits of Venus.

Mobilizing for the 1761 and 1769 Transits

Edward Scriven (1775-1841)
Portrait of Rev. Nevil Maskelyne, Astronomer Royal from 1765 to 1811 (from a portrait by Van de Puyl)

Gift of the Burndy Library

Portrait of Rev. Nevil Maskelyne, Astronomer Royal from 1765 to 1811

Maskelyne, an English astronomer, traveled to St. Helena in the South Atlantic to observe the 1761 transit, but was cursed with overcast skies. Seven years later, Maskelyne, by this time the Astronomer Royal, wrote to encourage people with the proper equipment to observe the 1769 transit, providing detailed instructions in how to make an observation of real scientific value.

John Philip Sousa and the Transit of Venus

John Philip Sousa (1854-1932)
Transit of Venus March
Washington, D.C.:
Courtesy of Collections of Music Division, Library of Congress

Transit of Venus March

As a memorial to Joseph Henry, the first Secretary of the Smithsonian Institution, a statue in his honor (which now stands in front of the Smithsonian “Castle”) was unveiled on April 19, 1883, shortly after the 1882 transit. The music you hear was composed for the ceremony by the legendary U.S. Marine Corps bandmaster John Philip Sousa. This march is called “The Transit of Venus,” in honor of Henry’s service on the original U.S. Commission on the Transit of Venus.

Recording of “The Transit of Venus” march arranged and conducted by Loras John Schissel and performed by the Virginia Grand Military Band on September 13, 2003, courtesy of Raytheon ITSS
Listen to the Music (mp3 format)


John Philip Sousa and the Transit of Venus

John Philip Sousa (1854-1932)
transit of Venus
Boston: Small, Maynard & Company, [1920].
Courtesy of George Washington University, Special Collections Department, Gelman Library

transit of Venus

In addition to being a composer and bandmaster, Sousa was also an author, writing three novels including this, his longest work. The transit of Venus plays only a small role in the book; the publishers wanted to title it The Alimony Club, to no avail. The plot centers around a young man vacationing on a yacht chartered by a group of misogynists (the Alimony Club). They are off to see the transit of Venus, but to their horror they find that the expedition leader is a “vivacious” female scientist, and hilarity ensues. The novel culminates with a performance of Aida at the Cairo Opera House. The book was not a bestseller.

Transit Expeditions in the 19th Century

Stackpole & Brothers
Broken-tube transit instrument
New York: 1874.
Courtesy of the National Museum of American History, Behring Center

Broken-tube transit instrument

This is one of eight transit instruments ordered by the US Naval Observatory for the 1874 expeditions to determine their exact positions. Observers would look in the eyepiece and measure the exact time when a star would cross a fine wire in the field of view. A prism at the base of the main tube redirects, or “breaks,” the starlight so that it can be observed from the side of the instrument, hence the name.

Transit Expeditions in the 19th Century

Pietro Tacchini (1838-1905)
passaggio di Venere sul sole dell'8-9 dicembre 1874 (The transit of Venus on 8-9 December 1874)
Palermo: Lao, 1875.
Courtesy of the U.S. Naval Observatory Library

passaggio di Venere sul sole dell'8-9 dicembre 1874

Tacchini, the energetic director of the Palermo Observatory in Sicily, organized an Italian expedition to observe the 1874 transit. Italy had just become a unified country in 1870, so the government was willing to support matters that would add to the new nation’s international standing. The Italians traveled to India and observed at a site near Calcutta.

New Possibilities: 1874 and 1882

U.S. Commission on the Transit of Venus
Atlas to part II of the papers relating to the transit of Venus in 1874
Washington, D.C.: Government Printing Office, 1873.
Courtesy of the U.S. Naval Observatory Archives

Atlas to part II of the papers relating to the transit of Venus in 1874

The U.S. Commission prepared these maps detailing places on Earth from which observers could see the 1874 transit. This map shows who would see the critical moment when Venus’s image would be totally on the Sun’s disk. The blue and red lines helped astronomers know when the event could be observed and where on the Sun Venus would appear to make contact.

New Possibilities: 1874 and 1882

U.S. Commission on the Transit of Venus
Instructions for observing the transit of Venus
Washington, D.C.: Government Printing Office, 1874.
Courtesy of the U.S. Naval Observatory Library

Instructions for observing the transit of Venus

To ensure the success of the American transit expeditions, it was important that the observers have their equipment set up identically and that the observations be performed in exactly the same way. To that end, the Navy published these detailed instructions covering everything from how to record observations to which way to turn the screws attaching the equipment.

Transit Expeditions in the 19th Century

U.S. Naval Observatory
Observations of the transit of Venus…, part II, sections 1-4 [page proofs]
Washington, D.C.: Government Printing Office, 1881.
Courtesy of the U.S. Naval Observatory Library

Observations of the transit of Venus…, part II, sections 1-4 [page proofs]

After the 1874 transit, the U.S. Naval Observatory staff began analyzing the results. Because of funding and staffing problems, they decided to delay publication until the 1882 transit observations were analyzed. On display are page proofs of the 1874 observations. The U.S. results were disappointing and they were never published, due to lack of funding and other bureaucratic difficulties.

Mobilizing for the 1761 and 1769 Transits

Benjamin West (1730-1813)
New-England almanack … for the year of our Lord Christ, 1769
Boston: Mein and Fleeming, [1768].
Gift of Ronald S. Wilkinson

New-England almanack … for the year of our Lord Christ, 1769

Since the 1769 transit of Venus was expected to be visible in the American colonies, there was a great deal of interest in seeing the rare event. The noted New England almanac producer Benjamin West included an extensive essay on the transit in his 1769 volume. It includes a diagram showing the path that Venus would take across the Sun’s disk.

To the Ends of the Earth

John Winthrop (1714-1779)
Relation of a voyage from Boston to Newfoundland, for the observation of the transit of Benus, June 6, 1761
Boston: Edes and Gill …, 1761.
Courtesy of the U.S. Naval Observatory Library

Relation of a voyage from Boston to Newfoundland, for the observation of the transit of Benus, June 6, 1761

In contrast with the extensive and often dangerous French and British expeditions, the thirteen-day voyage of the party led by Winthrop, a Harvard mathematics professor, to St. John’s, Newfoundland, could be considered a pleasant excursion. His party named the hill where they set up their observatory “Venus’s Hill.” Winthrop’s rare little book describes how they could see only the end of the transit, although their weather was quite clear.