Description

A quite rare example of a Fineman-/Hildebrandsonn type Nephoscope by F. Pellin, circa 1910

The nephoscope was invented in the nineteenth-century to measure the altitude, direction and velocity of clouds. Seventeenth- and eighteenth-century methods of determining cloud height required triangulation from the ends of two baselines. Other techniques involved using a map to trace the passage of cloud-shadows over the countryside, or a camera obscura to measure a cloud’s angular height and bearing from 0º north, (known in astronomy as ‘azimuth’).

Early nineteenth-century mirror nephoscopes used a shallow tank of inky water to reflect the sky and employed the same triangulating technique as the camera obscura, in which the angle of reflection was used to calculate the height of a cloud. Unfortunately, the image produced using the reflecting pool was rather restricted and wind easily disrupted its surface.

In 1846, the French meteorologist G. Aimé incorporated a horizontal mirror into nephoscope design, which significantly improved the instrument. Fineman’s nephoscope, first manufactured in 1886, employed darkened glass and was fitted with a compass needle. A vertical pointer rotated around the glass edge to be aligned with a cloud observed in the glass reflection. Engraved on the surface of the glass, concentric circles functioned as a measurement guide.

This example of a Fineman’s Mirror Nephoscope was produced by the French firm Pellin, Philibért Pellin (1847-1923) acquired from Jules Duboscq (1817-1886) after several years of collaboration and partnership, then shared the company with his Son Félix Pellin. Maintaining Duboscq’s excellent reputation, Pellin and his son Félix produced optical and meteorological instruments of the highest calibre.

Condition : the present example is fully complete with its rare circulare water level. The condition is excellent despite one of the three set screws which is shortent (its bottom part was broken). Case example with water level are really rare. The two wooden parts in the case are unglued but still complete and present.

See : https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/meteorology/cloud-studies