Signedunsigned
FunctionPart of a larger instrument known as Draper's self-recording barograph. The tube would have been fixed to the wall, and the cistern supported by the two springs seen here, which would have also been attached to a metal piece carrying a pencil, which would have written the barometric pressure reading onto a graph that moved by clockwork horizontally along a rail.
A third spring, equal in weight to the cistern, and of uniform pressure, was attached to another pen which traced a zeroing line along the graph, to compensate for the effect of temperature on the metal springs.
ProvenanceFrom the Blue Hill Meteorological Observatory. It was retrieved from the BHO on May 15, 1960 by David P. Wheatland.
Related WorksOn Daniel Draper and the Draper recording barograph, see W. E. Knowles Middleton, The History of the Barometer (Baltimore: Johns Hopkins University Press, 1964), 317 and 465.