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Robert Fitzroy and the myth of the ‘Marsden Square’: Transatlantic rivalries in early marine meteorology

D. C. Agnew


Marine data (especially in meteorology) are often grouped geographically using a set of numbered 10° latitude–longitude squares known as Marsden squares, which are usually attributed to William Marsden, Secretary of the Admiralty (and Vice–President of The Royal Society), who supposedly invented them early in the nineteenth century. Available records suggest that this system was in fact probably invented by Robert FitzRoy soon after his appointment as head of the British Meteorological Office in 1854. FitzRoy felt that early English work in marine meteorology was being ignored, notably by the American Matthew Fontaine Maury, who had pioneered the collecting of marine meteorological data from ship's logs. A desire to undo this wrong led FitzRoy to emphasize earlier (though abortive) British projects by A.B. Becher (in 1831) and by Marsden (probably in the 1780s), both of which involved grouping marine data geographically, though only over limited areas. FitzRoy's treatment of this earlier work seems to have created, much later, the belief that Marsden had invented the system of 10° squares. Given both Maury's and FitzRoy's desire to demonstrate priority in this field, it is ironic that the first clear proposal to collect and group data from ship's logs was made by the American (and British) natural philosopher Isaac Greenwood in 1728.

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