Sea-gage.
(Nautical.) a. An instrument invented by Drs. Hale and Desaguliers, to ascertain depths beyond ordinary deep-sea soundings. It is a self-registering apparatus, in which the condensation of a body of air is caused by a column of quicksilver on which the water acts. A viscid material, such as molasses, floats on the quicksilver and leaves its high-pressure mark in the tube. Ericsson's improvement is to cause the volume of water thus forced in to pass over into a second tube. b. A tide-gage (which see).