Josiah M. Grumman, a city surveyor in Brooklyn, N. Y., obtained a patent (#23,680) for an improved surveyor's chain on April 19, 1859, and sent this example to John Ferris, a surveyor in Dutchess County, N. Y., in October of that year.
It is a short Gunter chain with 50 links measuring 33 feet (2 poles) overall. The links are made of tempered steel wire, which Grumman found to be stronger and lighter than iron. To eliminate the traditional rings between the links, Grumman formed each link with a circular eye at one end and an oval eye at the other, so designed that these eyes fit easily into one another. One end of the chain has a spring balance and level for determining if the chain is held level and the tension applied to the chain. The other end has a thermometer with a Fahrenheit scale for determining the temperature at the time of measurement.
W. & L. E. Gurley purchased Grumman's patent from Grumman's estate in 1870. Gurley records indicate that Grumman's chains were made by metalworkers in Brooklyn.
Ref: J. M. Grumman, A Short Treatise on Surveyors' Chains and Chain Measuring (Brooklyn, 1859).
W. & L. E. Gurley, Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N.Y., 1871), pp. 130-131.
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