Reflection methods of measuring the depth of the sea

This paper deals only with the practical application of the idea of sounding by reflection as applied to the needs of navigation in the mercantile marine. It does not profess to dealwith any original researches on the subject, but is only a statement of the present state of the art, especially with reference to the mercantile marine of this country. In order to keep the paper within reasonable limits all detailed description of apparatus has been omitted. Theoretical discussions on the subject, together with detailed descriptions of apparatus, have appeared from time to time in the technical Press. The Hydrographic Review (1930, vol. 7, No. 2) contains references to previous articles on this subject. Most interesting papers can also be found in the Bulletin de l´Association Technique Nautique et Aironautique (No. 34 of 1930) and in Elektrische Nachrichten-Technik (1929, vol. 6, p. 165). The principal formulae referred to have been collected in an Appendix and have all been extracted from papers by Prof.Langevin.