MEASURING THE DEEP SEA. 



717 



lb such harbors as he was frequenting. But the ocean, to all 

 antiquity, was unfathomable ; they dared not attempt to cross 

 it, and of course did not think they could measure its depth. 

 Long after the ocean had been crossed bv ships the belief was 

 still current that it was impossible to measure its depth, and 

 this belief was made the stronger by the unsuccessful attempts 

 made in mid ocean to obtain soundings with the ordinary 

 lead and line. 



Before we arrived at a positive knowledge of the depth of 

 the ocean, scientific men attempted to calculate it by varioug 

 methods. Laplace, calculating the mean elevation of the land, 

 supposed the sea must be of about equal depth. Young, draw- 

 ing his deductions from the tides, calculated the depth of the 

 sea. This method has been recently used to calculate the 

 depth of the Pacific. A wave of a certain velocity indicates 

 water of such a depth. In the case of the earthquake of 1854, 

 in Japan, which caused a wave that extended to California, the 

 rate of its progress afforded an indication of the mean depth 

 of the sea it passed over, and authentic soundings taken since 

 have confirmed the general accuracy of the calculation. 



The ordinary lead used for soundings is a pyramid of lead, 

 the bottom of which has a depression in it, which is filled 

 with tallow ; on striking the bottom a little of the sand or mud 

 adheres to this tallow and is brought up to the surface. In 

 this way something is learned about the depth and bottom of 

 the sea, but not enough to satisfy the naturalists, who inquired 

 whether it might not be possible to dredge the bottom of the 

 esa in the ordinary way, and to send down water bottles and 

 registering instruments to settle finally the conditions of the 

 deep waters, and determine with precision the composition 

 and temperature at great depths. 



An investigation of this kind is beyond the powers of pri- 

 vate enterprise. It requires more power and sea skill than 

 naturalists usuallv have. It is a work for governments. That 



