The shift from superstition to scientific study of meteorology began when proper measuring instruments became available in the mid-17th century. By the early 18th century, Daniel Fahrenheit produced accurate mercury thermometers calibrated to a standard scale that ranged from 32 to 96 degrees (i.e., from the melting point of ice to body temperature). 

Early work by chemists and physicists further drove rigor in the study of weather and helped explain why storms form.  Robert Boyle published the models explaining the behavior of gas pressure, temperature, and density; John Dalton explained partial pressures of mixed gases; and Joseph Black determined heat release by condensation or freezing.  This work made it possible to measure and better understand not just steam in an engine or gases in a pressure vessel but also the atmosphere and its behavior.

Around 1750, Thomas Dobson invented the sling psychometer (in Philadelphia!).  A psychrometer, or a wet and dry-bulb thermometer, consists of two calibrated thermometers, one that is dry and one that is kept moist with distilled water on a sock or wick. At temperatures above the freezing point of water, evaporation of water from the wick lowers the temperature, such that the wet-bulb thermometer will be at a lower temperature than that of the dry-bulb thermometer. Determining the amount of water in the air allowed for more robust understandings of when and why various forms of precipitation occur.

Wind direction has been long measured with weather vanes and flags but wind speed was somewhat elusive. Sometimes wind is very forceful and easily measured (eg with a sock) at other times, it is faint and not powerful enough to move would be measuring tools.  Establishing wind speed and direction, however, is CRITICAL in an age dependent upon sail.

Following a devasting storm that hit the British Isles in 1703, Daniel Defoe (author of Robinson Crusoe) developed a 12-point scale that he called a table of degrees. This comprised, as he put it, “bald terms used by our sailors”.  This scale had no measurements, it simply ranked the power of the wind based on the terms experienced seamen used to describe it.

.

Defoe’s Scale of winds, 1704
0stark calm
1calm weather
2little wind
3a fine breeze
4a small gale
5a fresh gale
6a top sail gale
7blows fresh
8a hard gale of wind
9a fret of wind
10a storm
11a tempest

In 1780, the Palatine Meteorological Society of Mannheim, added empirical values to Defoe’s Scale using everyday observable factors (at least in Essen):

0Calm
1Leaves rustle
2Small branches move
3Large branches in motion and dust swirls up from the ground
4Twigs and branches break off trees

Eventually, the East India Company commissioned Francis Beaufort (who sailed on the Beagle with Darwin and Fitzroy) to improve upon the Mannheim scale. While serving aboard HMS Woolwich, he devised a scale of wind force that used a scale extending from 0 to 12.  He also added a description of the canvas that could be carried by a fully rigged frigate in different wind conditions. Like the observers of the Palatine Meteorological Society, he frequently used halves, which suggests he was confident he could estimate wind force accurately.

Even though Leon Battista Alberti describes an anemometer in 1450.  Modern numerical windspeeds in Miles/hour (nautical miles) would have to wait for John Thomas Romney Robinson, of Armagh Observatory to invent the modern rotational anemometer in 1855.

Barometer

In the early 1700’s The German philosopher Goethe describes a simple device called a Weather or Storm Glass.  Sometimes referred to as Goethe’s barometer, the weather glass is a teapot like container, made of blown glass, with a wide body and a thin spout which is the only opening to the larger part of the weather glass. It is filled with water, to a little above the connection between the body and the spout.  Rising air pressure will push the liquid back down the spout, whereas falling pressure will cause the water to rise in the spout, even to the point where it overflows. The weather glass was a useful predictive tool for farmers and sailors, as a falling level in the spout indicated increasing pressure and generally fine weather, and the opposite suggested approaching rain and storms.

At about the same time, developed a mercury barometer in partnership with Galileo Galilei.  Galileo and Torricelli were studying vacuums and Torricelli filled a four-foot-long glass tube with mercury and inverted the tube into a dish. Some of the mercury did not escape from the tube and Torricelli observed the vacuum that was created.   Through observation Torricelli realized that the variation of the height of the mercury from day to day was caused by changes in the atmospheric pressure.

Rain gauge

Christopher Wren created a rain gauge in 1662 but most sources show that the Chinese had been measuring rain since the Choson Dynasty (1418 to 1450).  Emperor Sejong (Choson) sought ways to improve agricultural technology to provide his subjects with adequate food and clothing so he developed a system of tipping buckets that measured the amount of water falling in a given place.  This system was brought back to Europe by Venetian traders (perhaps Marco Polo) and copied by Wren.

Reporting across various locations

The meteorological observations by clergyman William Derham (1657 – 1735) are among the earliest in England. James Jurin, the secretary of the Royal Society, laid out a plan for daily recordings of barometer and thermometer readings, wind strength and direction, precipitation and state of the sky in 1723. The English network of weather stations could count on fifteen international observers, ranging from Bengal and St. Petersburg to Massachusetts.

Published by Michael Carver

My goal is to bring history alive through interactive portrayal of ordinary American life in the late 18th Century (1750—1799) My persona are: Journeyman Brewer; Cordwainer (leather tradesman but not cobbler), Statesman and Orator; Chandler (candle and soap maker); Gentleman Scientist; and, Soldier in either the British Regular Army, the Centennial Army, or one of the various Militia. Let me help you experience history 1st hand!

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