benjamin franklin

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timeline: 1743
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Franklin montage
Gulf Stream chart
A chart of the Gulf Stream based on Franklin's sketches
Like everyone else, Benjamin Franklin was affected by weather; but unlike most people of his time, he tried to explain the reasons for various weather-related phenomena, and even discovered some ways to predict the weather.

One of Franklin's first recorded observations of weather patterns occurred in October of 1743, when he planned to observe an eclipse of the moon. As Franklin prepared to watch the eclipse in Philadelphia, a storm moved in and clouds obscured the moon. Later he learned that people in Boston, hundreds of miles northeast of Philadelphia, were able to see the eclipse because the storm didn't arrive there until several hours after the eclipse. Franklin became intrigued and continued gathering observations and eventually determined the direction of movement for storms. He was the first to observe that storms can move in an opposite direction from the direction of the wind. In other words, although the winds in a nor'easter blow from the northeast, the storm is actually moving from the southwest. In trying to explain how this weather pattern worked, Franklin accurately theorized about the existence of high and low pressure and proposed one of the first correct explanations for storm movement in the northern hemisphere.

As an extensive traveler, Franklin found himself on eight long transatlantic voyages, where, instead of sitting idle, he seized the opportunity to run various experiments at sea. During his first crossing in 1724, Franklin and his companion regularly checked and recorded the temperature of the ocean water and were struck by the differences in temperature along the way, with the water almost twenty degrees warmer when the ship crossed into the Gulf Stream. Franklin also observed other phenomena such as the color of the water and the type of seaweed floating in it.

Sixty years later, during Franklin's final Atlantic crossing, he was still trying to uncover the secrets of the Gulf Stream. By measuring the temperature of the ocean at various depths, Franklin rightly surmised that the Gulf Stream was like a warm river flowing over and through the Atlantic Ocean. He suggested that the Gulf Stream could be used to improve the speed of vessels sailing between America and England if those vessels stayed in the current when traveling east and avoided it while traveling west. Franklin's other contribution to the understanding of the Gulf Stream was a map he drew that showed its movement with a high degree of accuracy.

Franklin was interested in climate-related phenomena throughout his life. Just six years before his death, he published a number of "Meteorological Imaginations and Conjectures." For example, he was puzzled that hail and ice could occur in the summer time. While having no way to test his ideas, he correctly deduced that the upper atmosphere was much colder than the air below it. Moist air flowing into the upper atmosphere could produce ice that could fall to earth before it melted. He also wrote about fog, wind direction, insulation, and heat radiation.

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