Carruthers ‘Fishermens’ Current Meter (1953)
By Mr. Sv. Woldseth (of ‘Bergen Nautik’: made the Conical mesh) and Kelvin & Hughes (produced the instruments contained within the mesh and made the solid metal nose cone)

This instrument was created in response to a request from Norwegian fishermen who wanted a way of knowing the direction sub-surface currents. Carruthers claimed “current speed and direction are obtainable at any depth more or less without anchoring a ship and at the cost of a wait of about twenty minutes only”. There is no evidence of any device like this being used by fishermen. Carruthers created this instrument while on a trip to Bergen, using the hydrodynamical tank of the Geophysical Institute, with the assistance of Sven Woldseth of famous oceanographic instrument maker ‘Bergen Nautik’. The device contained a disposable chemical depth-indicator tube and compass, which screwed into the nose cone. These were calibrated at the National Physical Laboratory in England. The device at the bottom of the cone, records the angle at which the cone is lifted from the vertical by the current, from this current speed can be calculated. In order to record this measurement the device uses a sprung spike, which was restrained by a tablet that disintegrated in the water and released the spike into the wire gauze thus taking a single measurement.

Further information about this instrument can be found in J.N. Carruthers, ‘Some Inter-relationships of Oceanography and Fisheries’, Archiv für Meteorologie, Geophysik und Bioklimatologie, serie B, (1954)