4 THE OCEAN WOKLD. 



Laplace found, on astronomical consideration, that the mean depth 

 of the ocean could not be more than ten thousand feet. Alexander 

 von Huniboldt adopts the same figures. Dr. Young attributes to the 

 Atlantic a mean depth of a thousand yards, and to the Pacific, four 

 thousand. Mr. Airy, the Astronomer Eoyal, has laid down a 

 formula, that waves of a given breadth will travel with certain velo- 

 cities at a given depth, from which it is estimated that the average 

 depth of the North Pacific, between Japan and California, is two- 

 thousand one hundred and forty-nine fathoms, or two miles and a 

 half. But these estimates fall far short of the soundings reported by 

 navigators, in which, as we shall see, there are important and only 

 recently discovered elements of error. Du Petit Thouars, during his 

 scientific voyage in the frigate Venus, took some very remarkable 

 soundings in the Southern Pacific Ocean : one, without finding 

 bottom at two thousand four hundred and eleven fathoms ; another, 

 in the equinoctial region, indicated bottom at three thousand seven 

 hundred and ninety. 



In his last expedition, in search of a north-west passage, Captain 

 Boss found soundings at five thousand fathoms. Lieutenant Walsh, 

 of the American Navy, reports a cast of the deep-sea lead, not far 

 from the American coast, at thirty-four thousand feet without bottom. 

 Lieutenant Berryman reported another unsuccessful attempt to fathom 

 mid ocean with a line thirty-nine thousand feet in length. Captain 

 Denman, of H. M. S. Herald, reported bottom in the South Atlantic 

 at the depth of forty-six thousand feet ; and Lieutenant J. P. Parker, 

 of the United States frigate Congress, on attempting soundings near 

 the same region, let go his plummet, after it had run out a line fifty 

 thousand feet long, as if the bottom had not been reached. We 

 have the- authority of Lieutenant Maury for saying, however, that 

 " there are no such depths as these." The under-currents of the deep 

 sea have power to take the line out long after the plummet has 

 ceased to sink, and it was before this fact was discovered that these 

 great soundings were reported. It has also been discovered that the 

 line, once dragged down into the depths of the ocean, runs out un- 

 ceasingly. This difficulty was finally overcome by the ingenuity of 

 Midshipman Brooke. Under the judicious patronage of the Secretary 

 to the United States Navy, Mr. Brooke invented the simple and in- 

 genious apparatus (Fig. 1), by which soundings are now made, in a 



