Thermometer

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Thermometer. Thomas Jefferson Foundation, Inc.

In his memorandum books Jefferson recorded the purchase of almost twenty thermometers. On July 4, 1776, he bought one from Philadelphia merchant John Sparhawk for £3-15. Three days earlier he had begun his first surviving "meteorological diary."^[1] For the rest of his life his daily routine included a thermometer check at dawn and in late afternoon — in his opinion, the coldest and warmest times of day. His temperature record was sometimes supplemented with barometer and hygrometer readings, as well as notes on what he called "indexes of climate," like the blooming of plants and migrations of animals.

Detail of thermometer. Thomas Jefferson Foundation, Inc.

As one of the first systematic observers of the American climate, Jefferson tried to enlist others in his activities and even envisioned a national network of weather watchers. He realized that, for the formation of a reliable theory of climate, many others would have to provide what he had: years of "steady attention to the thermometer, to the plants growing there, the times of their leafing and flowering, its animal inhabitants, beast, birds, reptiles and insects; its prevalent winds, quantities of rain and snow, temperature of mountains, and other indexes of climate."^[2]

-Text from Stein, Worlds, 363

Further Sources

• Historical Society of Pennsylvania.