Windswept_ The Story of Wind and Weather - Marq de Villiers [30]
After that, developments came thick and fast. Anders Celsius, who constructed a temperature scale, also put together a wind-force scale. In Germany the Palatine Society, which joined the mania for measuring winds, set up the first weather office by coordinating observations from several cities in the Mannheim region of Germany. The ever-curious Benjamin Franklin added to the storehouse of knowledge in 1743, after a storm blocked a sighting of an eclipse of the moon he had been particularly eager to see. The winds in Philadelphia were from the northeast, but he discovered through correspondence that Boston, which was to his northeast, actually suffered the same storm later than he had. A few years later this curiosity led him to a theory of storms, and he concluded they were disturbances that moved independently. He didn't know yet that they rotated. If he had seen Dampier's observations, they hadn't registered with him.
By the end of the century the practical men understood a good deal about storms, though a more careful calibration and a really comprehensive theory wasn't to be for another few decades. Sea captains understood clearly that pressure affected weather—that low pressure meant a storm—and no ship would leave port without a glass, as barometers were by then called. By the early nineteenth century meteorologists were commonly drawing isobars on maps to denote pressure, which meant winds. In 1802 Nathaniel Bowditch produced his American Practical Navigator, which was filled not only with graphs and charts (one of his graphs suggested that a drop of one millibar in an hour indicated a storm center twenty-two miles away; a drop of three millibars a storm center ten miles away) but with hard advice to sailors that made it clear just how storms actually traveled, and what they could do about it. A storm's center could be found by the simple expedient of facing the wind, in which case the center would be to your right. If you did this periodically, you could tell which way the storm was moving. The worst possible place to be was in the direct path of the storm's advance or toward its right—that is, to the north of a storm tracking west, to the east of a storm tracking north. Bowditch called that the dangerous semicircle, where the winds actually pushed vessels back into the center of the storm. The safest place, by contrast, was to the left of the path, where the winds would tend to propel you away from the center—and away from the center was very definitely where you wanted to be. He called this the navigable semicircle. All this made sense only in the northern hemisphere, because the storms were rotating counterclockwise.
Later Joseph Conrad had some fun with these rather head-scratching directions, and in Typhoon had his captain mulling the possibilities: "[The skipper] lost himself amongst advancing semi circles, left and right hand quadrants, the curves of the tracks, the probable bearing of the center, the shifts of wind and the readings of the barometer. He tried to bring all these things into a definite relation to himself, and ended by becoming contemptuously angry with such a lot of words and with so much advice, all head work and supposition, without a glimmer of certitude. 'It's the damndest thing, Jukes,' he said. 'If a fellow was to believe all that's in there, he would be running most of his time all over the sea to get behind the weather.' "
Finally, in 1831, the true cyclonic nature of storms was persuasively described by the autodidact scientist William Redfield. His conclusions were drawn from careful observation, especially by tracking detailed reports of hurricane damage after a storm had passed through Connecticut. He learned from these reports that trees had been felled in different directions, depending on where they had been in the