172 ALEXANDER AGASSIZ 



Sounding in a few fathoms with a common lead line is 

 an easy matter ; and even down to one hundred fathoms 

 fairly accurate results may be obtained with a hand lead 

 line. Below this, the matter is quite a different question, 

 and when it comes to sounding in depths of several 

 miles the problem is exceedingly difficult. 1 Even at com- 

 paratively moderate depths the weight of the rope is so 

 great in relation to the sinker that it becomes impossible 

 to determine when the bottom is reached. Professor 

 John M. Brooke, when a passed-midshipman, devised 

 the first considerable improvement on these antiquated 

 methods. He contrived an apparatus consisting of a 

 cannon ball on a very light line, so constructed that 

 on striking the bottom the weight was disconnected and 

 the line drawn up with only the collecting cup, contain- 

 ing a sample of the bottom. Lord Kelvin, in 1872, in- 

 vented a sounding machine in which he used a piano- 

 wire line. An improvement on Lord Kelvin's sounding 

 machine, devised by Captain Sigsbee, had already been 

 in use on the Blake for three years. 



Agassiz joined the Blake at Havana on December 17, 

 1877, where he found his assistant, Mr. Garman, who 

 had come down on the boat from New York. A glance 

 at Chart l, 2 in the pocket in the front cover, will show 

 the lines run on this cruise. It embraced the region to 

 the north and west of the western end of Cuba, the Yu- 

 catan Bank, and the districts about Key West and the 



1 The deepest known spot in the ocean, near the Island of Guam, is 

 5269 fathoms — sixty-six feet less than six miles. If Mount Everest were 

 sunk in this spot its summit would be over two thousand feet under 

 water. 



2 The tracks of the voyages of the Blake are taken from a chart in 

 Three Cruises of the Blake, and include some lines of soundings made 

 when Agassiz was not on board. 



