In 1096, sun-spots were seen with the naked eye on March 3.
In 1206 A.D. on the last day of February, “there was complete darkness for six hours, turning the day into night.” This seems to have occurred in Spain.
In 1241 the sun was so darkened that stars could be seen at 3 p.m. on Michaelmas day. This happened in Vienna.[487]
The sun is said to have been so darkened in the year 1547 A.D. for three days that stars were visible at midday. This occurred about the time of the battle of Mühlbergh.[488]
Some of these darkenings may possibly have been due to an enormous development of sun-spots; but in some cases the darkness is supposed by Chladni and Schnurrer to have been caused by “the passage of meteoric masses before the sun’s disc.”
The first observer of a transit of Venus was Jeremiah Horrocks, who observed the transit of November 24 (O.S.), 1639. He had previously corrected Kepler’s predicted time of the transit from 8h 8m a.m. at Manchester to 5h 57m p.m. At the end of 1875 a marble scroll was placed on the pedestal of the monument of John Conduitt (nephew of Sir Isaac Newton, and who adopted Horrocks’ theory of lunar motions) at the west end of the nave of Westminster Abbey, bearing this inscription from the pen of Dean Stanley—
| “Ad majora avocatus quæ ob hæc parerga negligi non decuit” In Memory of JEREMIAH HORROCKS Curate of Hoole in Lancashire Who died on the 3d of January, 1641, in or near his 22d year Having in so short a life Detected the long inequality in the mean motion of Jupiter and Saturn Discovered the orbit of the Moon to be an ellipse; Determined the motion of the lunar aspe, Suggested the physical cause of its revolution; And predicted from his own observations, the Transit of Venus Which was seen by himself and his friend WILLIAM CRABTREE On Sunday, the 24th November (O.S.) 1639; This Tablet, facing the Monument of Newton Was raised after the lapse of more than two centuries December 9, 1874.[489] |
The transit of Venus which occurred in 1761 was observed on board ship(!) by the famous but unfortunate French astronomer Le Gentil. The ship was the frigate Sylphide, sent to the help of Pondicherry (India) which was then being besieged by the English. Owing to unfavourable winds the Sylphide was tossed about from March 25, 1761, to May 24 of the same year. When, on the later date, off the coast of Malabar, the captain of the frigate learned that Pondicherry had been captured by the English, the vessel returned to the Isle of France, where it arrived on June 23, after touching at Point de Galle on May 30. It was between these two places that Le Gentil made his observations of the transit of Venus under such unfavourable conditions. He had an object-glass of 15 feet (French) focus, and this he mounted in a tube formed of “four pine planks.” This rough instrument was fixed to a small mast set up on the quarter-deck and worked by ropes. The observations made under such curious conditions, were not, as may be imagined, very satisfactory. As another transit was to take place on June 3, 1769, Le Gentil made the heroic resolution of remaining in the southern hemisphere to observe it! This determination was duly carried out, but his devotion to astronomy was not rewarded; for on the day of the long waited for transit the sky at Pondicherry (where he had gone to observe it) was clouded over during the whole phenomenon, “although for many days previous the sky had been cloudless.” To add to his feeling of disappointment he heard that at Manilla, where he had been staying some time previously, the sky was quite clear, and two of his friends there had seen the transit without any difficulty.[490] Truly the unfortunate Le Gentil was a martyr to science.
The famous German astronomer Bessel once said “that a practical astronomer could make observations of value if he had only a cart-wheel and a gun barrel”; and Watson said that “the most important part of the instrument is the person at the small end.”[491]
With reference to Father Hell’s supposed forgery of his observations of the transit of Venus in 1769, and Littrow’s criticism of some of the entries in Hell’s manuscript being corrected with a different coloured ink, Professor Newcomb ascertained from Weiss that Littrow was colour blind, and could not distinguish between the colour of Aldebaran and the whitest star. Newcomb adds, “For half a century the astronomical world had based an impression on the innocent but mistaken evidence of a colour-blind man respecting the tint of ink in a manuscript.”