Pitot-Darcy Tube

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The Pitot tube, a simple device for determining the subsurface flow of water, is a hollow tube with a bend at the bottom that can be turned to face the flow. A French engineer named Henri Pitot described the form in 1732. Henry Darcy, the Inspector General of Ponts et Chausées in Paris, discussed various improvements in the 1850s.
This example consists of two brass tubes that measure 54 inches long overall, arranged so that one can face into the current and the other can face away from it. The tubes are mounted on a wooden board with a graduated scale. It came from the Proprietors of the Locks and Canals in Lowell, Mass., and was probably used by the resident engineer, James B. Francis. Francis did not mention instruments of this sort in the 1855 edition of his Lowell Hydraulic Experiments, but in the 1868 edition he talked about tubes of about two inches diameter and various lengths.
Ref: James B. Francis, Lowell Hydraulic Experiments (New York, 1868), p. 172.
Currently not on view
date made
after 1850
overall: 54 in; 137.16 cm
overall in case: 1 7/8 in x 55 7/8 in x 2 13/16 in; 4.7625 cm x 141.9225 cm x 7.14375 cm
ID Number
accession number
catalog number
Credit Line
Proprietors of the Lock and Canals
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Water Currents
Data Source
National Museum of American History


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