Halley's Quest A Selfless Genius and His Troubled Paramore (2005) / Chapter Skim
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Third Voyage 1701: 10 Prince of Tides
Third Voyage 1701: 10 Prince of Tides
Pages 145-157
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From page 147... ...
He was to chart the tides and other vagaries of the English Channel, and in the furtive role of spy he was also to survey assets near French ports on the south side of the channel, which the French call "La Manche." Once again Halley had drawn up his own orders and leveraged the monarchy to support another scientific voyage: You are to use all possible diligence in observing the Course of the Tides in the Channel of England as well as in the mid sea as on both shores, and to inform yourself of the precise times of High and Low Water; of the set and strength of the Flood and Ebb and how many feet it flows in as many places as may suffice to describe the whole. And where there are irregular or Half Tides to be more than ordinarily curious in observing them.
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From page 148... ...
By Halley's day, so much shipping passed through the English Channel that any improvement in its navigation would have reaped big rewards. Although many great philosophers of the day did not fail to recognize the Moon's involvement, they, like da Vinci and Galileo before them, had little understanding of how or why.
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From page 149... ...
Three days later on April 26, 1701, Halley requested that he depart immediately "in order to get the Paramour Pink manned with such complement as their Lordships shall think fitting." The Admiralty outfitted him with a pair of small boats, two extra cables, an additional anchor, and guns, as Halley specified, from the Tower of London, which housed the monarchy's chief armory. The Paramore wouldn't sail until early June, however, because Halley had trouble manning his pink despite the favorable terms then offered by the Navy.
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From page 150... ...
About 11 resolving to pass the race I got under sail with the last of the flood and at twelve Aldernay baring due west I observed the latitude 49 degrees 47 minutes. As soon as we were through the race and had gotten the French land NE of us the strong tide abated and the ebb sat SSW between Sark and Jersey, in the afternoon the wind came to W and WSW so that we could not lie better than South, and withal it began to blow fresh so I resolved to put in to Jersey.
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From page 151... ...
He identified a complex pattern behind the phenomenon and recognized that the daily high tide resulted from the rising Moon during the first half of the month and the setting Moon during the other half. He ruled out the monsoons as a factor and instead hypothesized that the bay of Tonkin's tidal range was proportional to the position of the Moon with respect to where the Sun's path crosses the celestial equator.
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From page 152... ...
In Book III, the final book, of his Principia, Newton explained the anomalous tides in the port of Batsha in the Gulf of Tonkin, a feat Halley had previously believed impossible."The whole appearance of these strange Tides, is without any forcing naturally deduced from these Principles, and is a great Argument of the certainty of the whole Theory," Halley exclaimed. It was Newton's attention to the tides that expedited the general acceptance of his theory of universal gravitation, most scholars contend.
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From page 153... ...
When the Sun and the Moon are out of kilter, the gravitational forces cancel each other out, causing neap tides, which are not as markedly high and low. Newton's Principia went on to elucidate why tides vary from day to day as well as place to place with latitude, as gravitational effects shift with the constantly changing interactions between Earth, the Moon, and the Sun.
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From page 154... ...
Halley was dispatched to gather intelligence about the defensive strength of the French near channel ports. What's more, to Halley's original instructions the Admiralty added the following warning about taking liberties in publishing any data he gathered while on the mission: "And in case during your being employed on the Service, any other Matters may Occur unto you the observing and Publishing whereof may tend towards the Security of the Navigation of the Subjects of his Majesty or other Princes trading into the Channel you are to be very careful in taking notice thereof." Unlike Newton, Halley had few reservations about applying sci
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From page 155... ...
But he refused to let stormy skies of either persuasion interfere with his mission. Halley's third voyage may have been short on exotic glamour compared to his first and second voyages, but it would bear practical fruits for channel travelers.
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From page 156... ...
. Called the resection method, it relied on fixing horizontal angles by the Sun to achieve greater accuracy than the conventional practice of using a magnetic compass.
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From page 157... ...
PRINCE OF TIDES 157 Nothing is known of the results of the spy mission. No records survive.
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