F. GEOGRAPHY. 239 



disturbing effect of the distant shore would be very small, 

 it would indicate with great certainty the shoaling of the 

 water, and a simple observation of the rate of shoaling could 

 not fail to be of service to the navigator. 



The foregoing objections would not apply, however, in a 

 case where the instrument was placed on a packet-ship which 

 was continually making the same voyage, as on one of the 

 Atlantic steamers for example. 



If whenever the ship's position was known the bathometer 

 was read and the reading entered on the chart, and if after 

 ten or twenty voyages a particular instrument was constant- 

 ly seen to have the same reading when the ship was in a 

 given position (as it undoubtedly would), it could not fail to 

 be trusted as a warning and as an aid. By an experience of 

 this kind a table of the bathometer readino-s which corre- 

 sponded to particular positions could be made and thoroughly 

 tested on such a vessel, which is constantly crossing in the 

 same track, so that after a time the reading of this particu- 

 lar bathometer would become an important sign of nearing 

 a coast. 



In this way, with intelligent officers who would not fail to 

 put the necessary tests to it, it may yet be deemed suitable 

 to serve as an important aid to navigation. Its great use 

 will be, for the present, on board of special surveying ships, 

 to indicate not so much the actual and absolute depths as 

 the changes of depth. If, for example, a ship is engaged in 

 making soundings with a trustworthy apparatus on board, 

 and if it is found that a given depth by the piano-wire al- 

 ways corresponds very nearly to the same reading of the 

 instrument (as it would), and if this continues to be so, then 

 a change in the reading of the bathometer would indicate to 

 the commanding officer the passage over shoaler or deeper 

 water, as the case might be, and it would show the necessity 

 for a new sounding a necessity which otherwise would be 

 overlooked. In the hands of intelligent officers this instru- 

 ment, which is now an experiment merely, may become of 

 great value, and it is quite within reasonable expectations to 

 hope for valuable aid from it in its perfected form. 



It is understood that an instrument of this class will soon 

 be in the possession of the Navy Department, and one has 

 been proposed for use on H. M. S. Faum, and upon the re- 



