Believed to be the rain gauge funnel removed from the roof of Flamsteed House in 1953. Until that point it had formed part of the meteorological apparatus installed on that roof (including an anenometer for measuring wind speeds) and was used to measure rainfall, possibly as part of a recording rain gauge (pluvigraph).

Also used on the roof of Flamsteed House to measure rainfall between 1840 and 1853 was a pluviometer attached to the Osler's anemometer.

Pluviometer (the one listed here is currently at the Science Museum, as is the Osler aneometer) is simply another name for rain gauge though used here to imply a greater level of sophistication than its predecessor rain gauges.