This is a remarkable sea-sounding instrument or depth meter. It’s based on atmosheric pressure and invented by Wigzell, London. The instrument is put away in a pine box together with a fathom scale. The instructions for use are stuck on the inside of the lid.
The instrument exists of a clear tube mounted inside a brass housing. The housing is fixed at a lanyard. The top end of the lanyard will be fixed to a sling and with the lead on the other side it will be dropped into the water.
Pressure forces water into the tube depending on the the depth. Back on deck the water column indicatest the depth to be read at the fathom scale.

Catalog: NM.4-37
Date: 1900-1940
HWL case: 5x66x8 cm (2x26x3,1 in)
Signed: WIGZELL’S PATENT (ATMOSPHERIC TYPE) SEA-SOUNDING INSTRUMENT
Origin: England
Condition: very good