The electrical bathometer was invented in 1876 by William Siemens, stimulated by the needs of the telegraph industry. Siemens' instrument was the first to come into widespread use and  he is often credited as the inventor of the bathometer. His instrument consisted of a tube of mercury and worked like a barometer.The pressure at the closed end of the tube deformed a steel sheet which was measured electrically and relayed to the surface.The Practical Magazine, vol. 6 (new series), no. 20, p. 249, 1876  Starting in the mid-nineteenth century, submarine telegraph cables were being laid around the world. Accurate knowledge of the depth of the ocean bed was important for this work. Previously, depth was determined by taking soundings with a lead line, a time-consuming and difficult method.* Jeffrey L. Kieve, The Electric Telegraph: A Social and Economic History, p. 238, David and Charles, 1973 .
A bathometer that did not need to be submerged was invented in 1876 by William Siemens, stimulated by the needs of the telegraph industry. Siemens' instrument was the first to come into widespread use and is so different and so much more practical than anything that had gone before that he is often credited as the inventor of the bathometer. His instrument consisted of a tube of mercury and worked similar to a barometer.The Practical Magazine, vol. 6 (new series), no. 20, p. 249, 1876 The pressure of the mercury acting under the force of gravity pushed down on, and deformed, a thin steel sheet. The height of the mercury in the column was thus proportional to the strength of the Earth's gravity field. The theory of the instrument was that the greater the depth of water under the ship, the lower the gravitational force would be. This is because water has a much lower density than the rocks of the Earth's crust.J. Munro, "Obituary: Sir William Siemens", Journal of the Society of Telegraph-Engineers and Electricians, vol. 13, iss. 53, pp. 442-462 Starting in the mid-nineteenth century, submarine telegraph cables were being laid around the world. Accurate knowledge of the depth of the ocean bed was important for this work. Previously, depth was determined by taking soundings with a lead line, a time-consuming and difficult method.* Jeffrey L. Kieve, The Electric Telegraph: A Social and Economic History, p. 238, David and Charles, 1973 .
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The electrical bathometer
A bathometer that did not need to be submerged
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is so different and so much more practical than anything that had gone before that
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like
similar to
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pressure at the closed end of the tube deformed a steel sheet which was measured electrically and relayed to the surface.The
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The pressure of the mercury acting under the force of gravity pushed down on, and deformed, a thin steel sheet. The height of the mercury in the column was thus proportional to the strength of the Earth's gravity field. The theory of the instrument was that the greater the depth of water under the ship, the lower the gravitational force would be. This is because water has a much lower density than the rocks of the Earth's crust.J. Munro, "Obituary: Sir William Siemens", Journal of the Society of Telegraph-Engineers and Electricians, vol. 13, iss. 53, pp. 442-462