8 THE BOTTOM OF THE SEA. 



sea which would explode when it struck the bottom. 

 The noise of the report would reach the surface, 

 and the time that had ela^ised from the moment the 

  jomb was dropped into the water would afford the 

 means of calculating the vertical distance it had 

 fallen. It is well known that water is a good trans- 

 mitter of sound. Dr. Colladon caused a clock to 

 strike under the water of the Lake of Geneva, and 

 it was heard in the first experiment four leagues oif, 

 and in the second at more than twice that distance. 

 However, no apparatus has been contrived which 

 solves the problem so thoroughly as the invention of 

 Brooke. 



2. Construction of Charts and Sections of the Ocean Bottom — But 

 little as yet known of this subject — Maury, the Fouiider of 

 Submarine Orographic Science. 



Let us imagine the commander of a vessel sailing 

 across the ocean to be capable of taking sounrlings in- 

 cessantly from the fir.-^t to the last moment of his voyage, 

 his apparatus being so contrived that the line would 

 shorten or len^^then with such exactness, according to 

 the varying depth, that the lead always just touched 

 the bottom. His observations, in such a case, would 

 bear a close resemblance to those which would be 

 made by a boatman crossing a river in the same 

 way. The plummet would at first sink to a certain 



