392 HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 



with sediment brought down by the Connecticut River. Other re- 

 gions in the Sound were also easily recognized but thus far no 

 attempts have been made to identify any particular sound character- 

 istic with a particular kind of sea-bottom. Doubtless experiments 

 along this line will prove interesting and valuable. 



The hydrophone is destined to be of great aid in accurate, rapid, 

 and detailed hydrographic surveys, affording as it does a continuous 

 sounding curve over any desired course, at the same time giving an 

 indication of the character of the bottom. For such researches a 

 special design of hydrophone having an extended and variable base- 

 line would probably be used. Thanks to the extensive labors of the 

 hydrographic bureaus the coastal waters of this and several other 

 nations are well surveyed, but the advent of the hydrophone into this 

 field will facilitate the checking and extension of this information so 

 vital to navigation. 



The Hydrophone as an Auxiliary to the Radio. 



Another field in which the hydrophone will doubtless serve as 

 an aid to navigation is that of auxiliary to the radio. It has been 

 clearly demonstrated that by the use of a proper sound-source and 

 hydrophone, code messages may be exchanged up to ranges of from 

 15 to 20 miles by vessels under way, so that this equipment may be 

 advantageously used for handling the " short traffic " communica- 

 tions between adjacent vessels or from vessel to shore. With the 

 rapid growth and expansion of radio science the problem of inter- 

 ference becomes more vital every year so that the relief which may 

 be afforded by hydrophone communication will, no doubt, be very 

 welcome. 



The use of powerful sound-sources, designed to be located off 

 promontories, at harbor entrances, etc., and operated by power ob- 

 tained from shore or installed upon light vessels will very mate- 

 rially increase the range at which such communication can be carried 

 on or guiding bearings obtained, thus introducing the hydrophone 

 into the field now occupied by the radio compass. One does not 

 have to make many trips on the " trackless main " to appreciate the 

 very positive value of each such additional source of information in 

 situations of uncertainty and doubt. 



