Halley's Quest A Selfless Genius and His Troubled Paramore (2005) / Chapter Skim
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9 Chart the Needle
9 Chart the Needle
Pages 127-144
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From page 127... ...
The odd bounty he carried, gleaned from nearly two years and many thousands of undulating miles, was a clutch of numbers. Never had anyone shown as much interest in the wide blue sea -- not merely the shoreline -- and brought back little else but abstract data.These nearly 150 observations ranged from roughly 50 degrees north latitude to 50 degrees or so south latitude.
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From page 128... ...
But in connecting the dots, the plots of similar declination values, patterns had emerged. Halley had converted his daily observations into curved lines depicting areas of equal magnetic variation.
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From page 129... ...
Rhumb lines, or lines of constant compass bearing that ships typically steer along appear as straight lines. The major disadvantage of this type of projection is that polar regions appear especially enlarged.
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From page 130... ...
Halley has more than any other applied the deepest thought in establishing a theory of the declination of the magnet which the learned have been seeking to improve ever since; yet he does not ven ture to determine by geometry the situation of the magnetic poles upon the earth and to establish rules for computing the declination. Mean while however, he has empirically constructed crooked lines representing the declinations of the magnet on the largest ocean of the world, and he has had the good fortune to see those lines, which were constructed mostly on the basis of the observations taken during his voyages con firmed more and more by later experiments.
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From page 131... ...
Even almost two centuries later, for instance, Halley's charts were touted by G Hellmann, a prominent German historian of science, as "a masterpiece of practical navigation."His representative system was embraced as being "of the greatest importance in all branches of physical geography." Contour-type lines of equal field increments are still plotted today.
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From page 132... ...
His improvement of the air pump helped confirm that magnetic action occurs in a vacuum. Boyle argued that direct contact with an effluvium caused magnetic attraction -- an idea that was compatible with Gilbert's permanent magnet hypothesis.
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From page 133... ...
. and that in those parts of the world which lie near adjacent to any of those magnetical poles, the needle is governed thereby; the nearest pole being always predominant over the more remote." His idea was that there were two north magnetic poles and two south magnetic poles.
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From page 134... ...
He believed Halley had borrowed key ideas from a little-known mathematician named Peter Perkins, whom Halley consulted on his deathbed in 1680. Perkins was master of a prestigious school for boys, the Royal Mathematical School at Christ's Hospital, established to produce a small cadre of highly trained navigators.
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From page 135... ...
He actively sought out the results of others to develop hypotheses about not only geophysical but also historical patterns. Halley's method typically entailed compiling observations from varied sources and then publishing them openly in the Philosophical Transactions.
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From page 136... ...
When the notion reached England, the self-taught seaman William Borough tested the reigning watch technology. But such watches lost as much as 15 minutes a day and required seemingly constant winding.
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From page 137... ...
While an eternal clock that worked at sea would for a time prove quite valuable to society, the concept of a perpetual motion machine powered by magnetism, first proposed by the very same Petros Peregrinus, would become a perpetual lark in the science world. In the 18th century, one true believer presented his ideas for a perpetual motion machine not once but twice to the Royal Society.
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From page 138... ...
In a marvelous display of scientific sharing of data, Halley, using data supplied by many others, expanded his famous chart in 1702 into Halley's World Chart of Magnetic Variations, "A New and Correct Sea Chart of the Whole World showing the Variations of the Compass as they were found in the Year MDCC." Despite its all
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From page 139... ...
Even to Rome a watery bound was set Where Danube here and Tigris here she met. But wider the blue wave to Britain bows Where'er the breezes waft her mighty prows ANNA the sea's bright queen, Jove's ally thou, Don thou thine armour, crown thy royal brow, Pallas herself who grants thee all her aid, All men will think thee, in her image made.
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From page 140... ...
From existing copies of various editions, historians note that it was reprinted frequently with minor changes. No doubt the wider dissemination of information through increased trade helped advance science and navigation, including many of Halley's contributions.
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From page 141... ...
Printers in France and the Netherlands also published Halley's world chart. Around 1740 the Dutch East India Company adopted the Halley charts for its ships with the intent to use them to estimate longitude from the variation.
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From page 142... ...
In the second paper, Halley actually applied the physical limits spelled out by Newton to his postulate. Regardless of the origin of some of the ideas in his first paper on geomagnetism, Halley's mission aboard the Paramore significantly contributed to what we now know as geophysics -- more so than his basic meteorological chart and other previous innovations.
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From page 143... ...
It would be more than a century after Halley's death when German mathematician and astronomer Karl Friedrich Gauss introduced improved techniques for observing and analyzing Earth's magnetic field. For example, in 1832 he devised the magnetometer, essentially a permanent magnet suspended horizontally by a gold wire, to measure the strength and direction of magnetic fields.
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From page 144... ...
144 HALLEY'S QUEST before Sidney Chapman and Julius Bartels would move the field into the modern age. But in June 1701 the Paramore still had another mission in her.
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