MESULTS OF EXPERIMENTS. 15 



cable parted, that expense would be added to the rest, 

 and thus the lost apparatus could seldom be replaced. 

 Evidently, experiments of this kind can only be made 

 by Governments, or by commercial companies in- 

 terested in their results, i^or example, the laying of 

 submarine telegraph cables has made it necessary in 

 recent times to sound the ocean in various tracks. 

 Almost every day sees some addition made to our 

 knowledge in this way, and there can be no doubt 

 that the multiplication of submarine telegraph lines 

 will tend very greatly to hasten the time when we 

 shall have an accurate idea of the form of the earth, 

 and of the lesser accidents which. affect its surface. 



Before the general form of the earth was ascer- 

 tained, the depths of the ocean were the subject of 

 the most extravagant suppositions. The writings of 

 geographers abound in such expressions as that of 

 " a bottomless and shoreless sea," to designate tlie 

 Atlantic Ocean. The abandonment of such absurdi- 

 ties is a necessary consequence of the facts known in 

 the present day concerning the form and physical 

 constitution of our planet. But other speculations, 

 not less calculated to fill the imagination with an 

 idea of grandeur, have taken their place. If the mass 

 of water which covers about three-fourths of the solid 

 crust of tlie globe is, after all, limited in quantity, 

 what is the depth of the basins which contain it ? 



