Dienstag, 5. Juni 2012

Chasing the Venus....Pingré in Rodrigues

"...an enlightening chronicle of the first truly international scientific endeavor—the eighteenth-century quest to observe the transit of Venus and measure the solar system.

On June 6, 1761, the world paused to observe a momentous occasion: the first transit of Venus between the earth and the sun in more than a century. Through that observation, astronomers could calculate the size of the solar system—but only if they could compile data from many different points of the globe, all recorded during the short period of the transit. Overcoming incredible odds and political strife, astronomers from Britain, France, Russia, Germany, Sweden, and the American colonies set up observatories in remote corners of the world, only to have their efforts thwarted by unpredictable weather and warring armies. Fortunately, transits of Venus occur in pairs: eight years later, the scientists would have another opportunity to succeed. "(Book)

"In November 1760 two French astronomers set out from Paris to view the transit of Venus from far-flung destinations: thirty-eight-year-old Jean-Baptiste Chappe d’Auteroche began his 4,000-mile journey to Tobolsk in Siberia and forty-eight-year-old Alexandre-Gui Pingré to Rodrigues, a small island in the Indian Ocean not far from Mauritius.

Both were regarded as ‘worthy’ of the honour and the ‘perfect’ candidates for the appointment – or so at least the members of the Académie des Sciences thought. They were certainly brilliant astronomers, but also corpulent and middle-aged – not exactly the epitome of dashing adventurers but they were ready to face the dangers of the long voyages.

Pingré, however, had some second thoughts on the evening before of his departure. The appointment had first ‘extremely flattered’ him, but now his friends’ warnings began to trouble him. They were ‘the first to be frightened about his fate’, Pingré noted in his diary, and therefore tried to convince him that his life was in danger. Suddenly he saw the voyage through different eyes: instead of fame and honour, death and disease might loom. With the whole of Europe in the midst of the Seven Years War, Pingré was risking ‘my liberty, my health, and even my life’.

Despite his worries, Pingré left Paris to catch a boat from Lorient – the headquarters of the Compagnie des Indes – on the coast of Brittany, while Chappe made his way across Europe. From the beginning their journeys were riddled with problems. Only a week after Chappe had departed from Paris, his carriage was already beyond repair. He had to purchase a new one as well as replace his thermometers and barometers which had been damaged in accidents – though luckily his telescopes emerged intact. Meanwhile Pingré was stuck in Lorient where the local agents of the Compagnie complained that he had brought a rather excessive amount of luggage. Outraged, Pingré argued that 700 to 800 pounds of luggage was nothing unusual for an astronomer – they were certainly not travelling lightly."(source)

Some vessels with astronomers on their way to their destination were attacked by war ships, this also happened to Pingré on 10 January 1761, and there were more challenges..

"In early April 1761, just after rounding the Cape of Good Hope, Alexandre–Gui Pingré’s ship met a damaged French supply vessel that had been attacked by the British. Packed to the brim with provisions from the Cape for Mauritius the captain ordered Pingré’s vessel to accompany and protect them. Instead of sailing to Rodrigues where he had been ordered to view the transit on 6 June 1761, Pingré was now forced to go to Mauritius where he disembarked on 7 May.

It was still possible to reach Rodrigues in time – an eight-day journey and no more, one captain had told Pingré. However, squalls and high waves had slowed them down first, then a lull. The days were ticking by and the frenzied race had come to a standstill. On 26 May, Pingré finally saw Rodrigues in the distance – a sight ‘that filled me with such satisfaction as I haven’t felt since my departure from France’, he cried, but there was still no wind. He was now, Pingré believed, in the hands of God and the captain. ‘The calm continued on the sea, in the air and in the spirit of M. Thullier [his assistant]’, he wrote in his journal, ‘but certainly not in mine’.

It had been on the way from Mauritius to Rodrigues that he observed on 18 May 1761 the lunar eclipse – one of the celestial encounters by which the astronomers would be able to determine their exact geographical position which was essential in order to use the transit data. This one was one of the rare total lunar eclipse during which the moon became completely invisible. As the earth slowly moved between the sun and the moon, its shadow hiding the moon, many astronomers pointed their telescopes to the night sky, Pingré watched from the deck of the vessel."(source).

"Then, on 28 May, only seven days before the transit, Pingré finally set foot on the ‘desired island’. There was no town or fort on Rodrigues. The only reason the Compagnie des Indes kept the island was for its large turtle population. Regarded as a remedy against scurvy, the turtles were collected and kept in an enclosure and every two or three months dispatched to Mauritius. The governor of Rodrigues, Pingré snobbishly noted, lived only in a small log cabin made of roughly hewn timber and mud. Pingré and his assistant had to sleep in a shed with a dirt floor beside this governor’s ‘residence’.

‘We had no time to lose’, Pingré wrote. He found a location in the north of the island from where to view the transit, but it was too late to build a proper observatory. Instead he placed some big boulders in a circle and constructed a small hut to house the instruments. It was so crudely built that it gave little protection from wind, dust and animals. The instruments had already suffered from the long sea voyage with some ‘eaten by rust’, Pingré moaned, hectically polishing and greasing them with turtle oil, the only lubricant available. Over the next days, the French astronomer prepared his instruments and observed the movements of Jupiter’s satellites at night in order to set the clock – an enterprise that was sabotaged by the rats that chewed through one of the pendulums. He only had a few days to the transit."(source)

Triangulation on Rodriguez Island, from the Illustrated London News, 24 October 1874.source

To make things very short, Pingrés transit observation was doomed also by the weather and in some encyclopedias it was simply tagged as unsuccessful.

" On the fateful 6th of June the weather was generally unfavourable. At 5.30 am, the wind, which had blown hard during the night, calmed down somewhat, but there was a heavy cloud in the east, and a quarter of an hour later the sky was almost completely overcast. At the crucial time, between 8.00am and 8.30 am the clouds cleared sufficiently for observations to be made but the wind rose so strong, that Pingré was as much troubled by it as by the clouds with the result that the observation was far from satisfactory.Pingré made his observation "dans l'enfoncement de Francois Leguat", probably on the hill of the East to it."  (Source: North-Coombes)

A living Domed Rodrigues Giant Tortoise (Cylindraspis peltastes) depicted by Jossigny in c. 1770. 

Maybe he could not contribute with much related to the Transit of Venus itself but his account of the 3 and a half months in Rodrigues has proved valuable in many respects. First of all his second objective of his voyage to Rodrigues. He was determined to draw a map and so with his assistant he set out on several occasions taking angles in order to determine latitude and longitude. Lack of time and the capture of the island by the British Navy prevented Pingré, who was said not to aim much at accuracy, from drawing a more accurate map than he actually did. However, his Rodrigues manuscript was voluminous, containing, beside meteorological observations, a 100 pages alone of the island's capture.And we learn that during his visit Rodrigues had just a handful inhabitants, "a surgeon and a corporal in charge of a dozen slaves who were engaged in collecting tortoises for shipment to Isle de France." In 1761, Abbé Pingré wrote:

"The tortoise is not a pretty animal, but it was the most useful of those we found at Rodrigues. In the three and a half months that I spend on the island, we ate almost nothing else: tortoise soup, fried tortoise, stewed tortoise, tortoise forcemeat, tortoise eggs, tortoise liver - these were pretty much our only savouries. This meat seemed to me as good on the last day as on the first; I did not eat many of the eggs; the liver seemed to me the most delicious part of the animal. After five weeks stay I was attacked by dysentery which I kept secret, because I counted more on myself to heal it than the island's surgeon. Diet and rest put me right in a few days, but it left me with an extraordinary involuntary repugnance for this liver that I had so liked until then. Should I thus regard it as the cause of my indisposition?. . .Tortoise fat is very abundant and does not congeal; it is what is known as tortoise oil. This oil had no bad taste, it is very healthy, and we seasoned our salads with it, used it in frying and all our sauces. Rodrigues tortoises are foot and a half long and bout a foot across; they were formerly large, but they are no longer given time to grow. When a bigger one is found, it is called a carrosse. These carrosses cannot harm a waken man, though they have sometimes bitten sleepers hard. The shells of these tortoises served us like baskets to carry oysters and similar provisions. The flesh of these tortoises is the colour of mutton, and approaches it for taste." (Pingré, 1763; Cheke and Hume, 2008, found here).

Pingré mentioned not only the tortoises which at his time were still more or less abundant but also that other species mentioned by Leguat about 70 years earlier were not anymore to be seen, like the Rodrigues Night Heron.

As to the second part of the Transit of Venus pair, Pingré was more successful.
"More satisfactory results were obtained from an expedition to the French Cape on Haiti where the next transit was observed on 3 June, 1769."(source)
Monument of Pingré in Rodrigues

The next Transit of Venus took place in 1874, and it was again observed by scientists sent to the island, this pic was sent to me by Brice, unfortunately without source

"Not far from Port Mathurin on Rodrigues, on a site where the old Fort Duncan was loacted, Charles B. Neate erected his observatory huts. The transit hut was enclosed by a large stone wall to protect it against hurricanes. On the morning of the transit, the observatory was surrounded by policemen and no one was allowed to approach. Neate observed with the 6-inch equatorial. At both ingress and egress the black drop was very apparent. Today, there is a plaque commemorating the event (with the wrong year 1894), attached to a large concrete block."

The transit hut at Point Venus, surrounded by a wall to protect the hut against hurricanes. (Picture courtesy of National Maritime Museum, London) 

The scene as it is today with the concrete block and plaque commemorating the event. 
Photo:Deva Ramasawmy, 2009
Tomorrow between 6.20 am and 8.00 am the Transit of Venus can hopefully be observed again in Rodrigues.


- Alexandre Guy Pingré/ New Advent Encyclopedia


Anonym hat gesagt…

Liebe Birgit,

leider habe ich zu spät von diesem Ereignis erfahren und hatte somit gar keine Gelegenheit, den Venus Transit zu beobachten, trotz Sonnenscheins heute Morgen.

Dein Bericht über die Reise von A. Guy Pingré nach Rodrigues war auf jeden Fall abenteuerlich und hochinteressant.
Es ist unglaublich, was Menschen für wissenschaftliche Forschungen schon vor 250 Jahren an Strapazen auf sich genommen haben und Pingré sich ausgerechnet diese winzige Insel im Indischen Ozean für seine Beobachtungen ausgesucht hat, wo damals nur eine Handvoll Menschen lebten - sagenhaft und sehr mutig!

Nebenbei wird dabei auch die Ausrottung Eurer Schildkröten dokumentiert, das gereicht ihm allerdings weniger zum Ruhm...

Liebe Grüße und Dank für Deine tolle Arbeit.

Birgit Rudolph/Dirk Krehl hat gesagt…

Liebe Britta-Gudrun,

Ich hatte das Datum zu Beginn nicht ganz richtig eingegeben, bei uns ist es heute früh, in ein paar Minuten soll es beginnen, doch es ist wolkig.

Ich selbst werde auch nicht die Gelegenheit haben mit entsprechendem Schutz zu schauen,doch ich hoffe immer noch,dass unser lokaler Astronom Brice Allenbrand mehr Glück hat als Pingré.

Ein schneller morgendlicher Gruß von der Insel


Anonym hat gesagt…

Liebe Birgit,

hier war der Durchgang leider nicht zu sehen, aber Christina in Berlin hatte Glück und zeigt in ihrem Blog einige schöne Fotos davon.

Fromme Grüße vom Fronleichnamstag sendet Dir

Anonym hat gesagt…

Hallo Birgit

Dieses von der Nasa freigegebene Foto
fand ich besonders eindrucksvoll:
Die Venus ist oben links zu sehen.
In Frankfurt war es leider bedeckt.

Grüssle Chris