3-070-812 - The Print Collector/Heritage Images

Greenwich Observatory: photographing the temperature; method of reading deep-sunk thermometers, 1881. '...apparatus provided at the Royal Observatory, for meteorological as well as for astronomical purposes...In the underground chambers here, called "the Magnetic Basement," the phenomena of terrestrial magnetism are made to register themselves by photography; the declination and variation of the compass, the variations of horizontal magnetic force, and those of vertical magnetic force, each by separate instruments...The barometer, and likewise the thermometer, are here also made to register their own variations respectively, by a suitable application of photography. Our Illustration shows this operation being applied to one of the thermometers...In this courtyard behind the Magnetic Observatory building are the four deep-sunk thermometers, having their bulbs placed at different depths below the surface of the ground; one at the depth of 3 ft., one at 6 ft., one at 12 ft., and one at 24 ft. The variations of temperature indicated by these thermometers respectively are daily noted and recorded...We may suppose...that the accumulated heat of all the summer months remains deep in the earth, becoming still more intense during the autumn season'. From "Illustrated London News", 1881.