Scarce Zero-setting Rain Gauge by Negretti & Zambra No 17 c.1930

A very good scarce Zero-Setting Rain Gauge by Negretti & Zambra no. 17 c.1930. Zero-Setting Rain Gauge constructed principally in copper and brass, box form with O-G plinth and pediment, twin securing plates. Removable collector marked “Negretti & Zambra, London” of inverted pyramidal form with debris shield, twin clamping screws. The mechanism emulating the reverse of a deadbeat escapement, motive force derived from twin water receivers equally set to a beam with central pivot and supplied from a lower collecting funnel, anchor and escape wheel, three further driven gears, assembled between cruciform and circular plates. The rear plate with zeroing knobs. Condition: Working well, the movement stripped and serviced, the exterior re-japanned as original. Comments: Originally noted in the Negretti & Zambra catalogues of c.1910 and c.1915 as a “Self-Recording Dial Gauge”, this is the evolution of those earlier gauges, featuring in Negretti & Zambra’s Standard Meteorological Instruments M2 catalogue c.1935 (see image). Dial pattern rain gauges indicate on the dial the number of hundredths of an inch of rainfall passing the gauge since the last observation. Although the earlier rain gauges were available in galvanised or japanned iron to withstand the elements, copper was strongly recommended on account of it being much more durable. From the M2 catalogue: The funnel is of copper with brass rim 8” square; the outer case is of copper with glass front and setting hand; the mechanism is a bucket with open ends divided in two parts and pivoted about its central point – this bucket tilts when 0.01” of rain has been collected; an escapement advances a toothed wheel and the index hand moves over the dial at each step. The dial is graduated in divisions of 0.01” up to 1”, with a smaller dial to 12”. An aesthetically attractive, scientifically important and very unusual instrument. The perfect addition to any collection of meteorological interest.