Bathometer

an instrument for measuring depths, especially of sea water. One kind is a peculiar, self-registering spring balance. It is difficult to ascertain the depth of the ocean. This instrument is based on the density of sea water at varying depths. The deeper the water, the greater its density and the greater its buoyancy. A stone weighs less--comes nearer floating--in deep water than in shallow water. The operator takes the weight of a sinker just beneath the surface of the sea, and again after the apparatus has been lowered by a cord into the sea. As stated, the index of the balance registers the weight. A comparison of the two results is made. The difference in buoyancy gives the difference in density and enables the scientist to compute the depth.