Captain Glynn, U.S.N., has made some interesting observations, ranging
over 200° of latitude, in different oceans, in very high latitudes,
and near the equator. His apparatus was simple: a common white
dinner-plate, slung so as to lie in the water horizontally, and sunk
by an iron pot with a line. Numbering the fathoms at which the plate
was visible below the surface, Captain Glynn saw it on two occasions,
at the maximum, twenty-five fathoms (150 feet) deep; the water was
extraordinarily clear, and to lie in the boat and look down was like
looking down from the mast-head; and the objects were clearly defined
to a great depth.