Dr. Ahrens's paper, which was presented in a more extended version at the meeting in Paris, describes a number of ways in which automatic processes may be applied to, or operated from, echo-sounders.

Knowledge of the depth of water is of secondary navigational value to the surface ship since (as compared with the submarine), she has no changes of course to make in the vertical direction. The present state of development of surface navigation systems makes the use of the depth as a method of navigation superfluous in all cases in which sufficient water is available, where there is no danger of grounding. It can, however, when the topography of the sea-bottom is known from accurate charts, be employed for checking and confirming the data determined by other forms of navigation.