Page 439 echo sounding 512 



may be obtained in a few seconds from a vessel proceeding at full speed, in contrast to an 

 hour or more that may be jrequired to obtain a wire sounding of similar depth from a 

 ship stopped in the water. Echo soundings can be obtained so frequently in shoal water, 

 many hundreds per minute with some instrujnents, that a nearly continuous profile of 

 the bottom can be made while the vessel is moving through the water at normal speed. 



Echo-sounding equipment may be employed on vessels ranging in size from a small 

 rowboat to the largest ocean-going ship. The equipment is generally permanently 

 installed on a vessel, and considered part of the navigation or survey equipment; 

 however, portable instruments are sometimes used that can be temporarily installed 

 and removed as desired. This latter type of instrument is particularly adapted for use 

 on small vessels and launches. 



In this chapter are included detailed descriptions of specific types of echo-sounding 

 equipment and their operation, general limitations, classifications, and functions of 

 parts, with particular emphasis on those types used in hydrographic survejdng by the 

 Coast and Geodetic Survey. 



512. History of Echo Sounding 



The principles of echo sounding were formulated well over a hundred years ago 

 and attempts were made shortly thereafter to reduce those ideas to practical application. 

 But only in recent years has echo sounding been developed to a stage of practical use- 

 fulness. 



History discloses numerous observers who noted the fact that sounds could be 

 heard under water, but apparently no one suggested that such sounds might be used for 

 the measurement of distance and depth until 1807, when a French physicist, Dominique 

 Frangois Jean Arago, made the specific proposal that water depths might be measured 

 by utilizing the propagation of sound. Unfortunately, Arago's ideas remained little 

 more than a proposal. In the following years several unsuccessful attempts were made 

 to measure depths by sound, but these failed because of lack of proper equipment 

 and the meager knowledge of acoustics that existed at that time. Among the 

 early experimenters in underwater sound were Colladon and Sturm who in 1827 devised 

 a means of measuring horizontal distances and made a fairly good determination of the 

 velocity of sound in Lake Geneva. In 1837 Charles Bonnycastle made unsuccessful 

 attempts to hear echoes in water an,d in 1854 the great American navigator and scientist, 

 Matthew F. Maury, attempted to obtain echo soundings, by discharging gunpowder 

 under water, also without success. Had he listened under the water for the echo his 

 experiments might have proved successful. 



It was more than one hundred years after Arago's proposals that the first actual 

 means for obtaining echo soundings was devised. One of the earliest patents based on 

 echo-sounding principles was issued to A. F. Eells of the United States in 1907. It is 

 not known whether Eells' equipment was successful, but his conception of echo-sounding 

 principles was far ahead of his day. Dr. Alexander Behm of Germany is given credit by 

 many for the first echo soundings. His early experiments consisted in firing cartridges 

 in the water and recording the echoes photographically. Much of Behm's success and 

 that of later experimenters can be attributed to the gradual accumulation of knowledge 

 in the field of acoustics and related sciences since the time of Arago. 



The sinking of the Titanic in April 1912, by a collision with an iceberg, motivated 

 Behm and others to devise methods of preventing similar disasters. Attempts to 

 receive echoes from the submerged portions of icebergs led to the development of 



