THREE CRUISES OF THE BLAKE 169 



canoes, which has fallen on the surface of the oceans 

 and sunk ; and the pteropod and the Globigerina oozes, 

 composed of the accumulation of the shells of small 

 animals living near the surface which have died and 

 fallen to the bottom. Geologists have been unable to 

 point to any rocks anywhere on the earth's surface that 

 could have been formed from such deposits. Hence we 

 seem led to the inevitable conclusion that the beds of 

 the oceans have been such for a considerable period of 

 geological time. So that geologists who have kept in 

 touch with the advances of oceanography are inclined 

 to be conservative in their estimates of the amount of 

 disturbance in the earth's crust under the sea in recent 

 geological times. 



In 1877, Agassiz eagerly accepted an invitation from 

 Carlile P. Patterson, superintendent of the United 

 States Coast Survey, to take charge of a series of dredg- 

 ing cruises in the steamer Blake. She was a small 

 schooner-rigged vessel of 350 tons, 140 feet on the 

 water-line, with a beam of 2GJ feet and a draught of 11 

 feet ; commanded by Lieutenant-Commander (now Re- 

 tired Rear-Admiral) C. D. Sigsbee, afterward captain 

 of the ill-fated Maine. 



In equipping the Blake, Agassiz found his experience 

 as a mining 1 engineer of the greatest assistance in mak- 

 ing many improvements in the apparatus used by his 

 predecessors. In this he was ably assisted by the ingen- 

 uity and mechanical skill of Captain Sigsbee. The most 

 important improvement Agassiz introduced was the sub- 

 stitution of wire rope for dredging in place of the hemp 

 rope used in all previous deep-sea expeditions. He also 

 changed the arrangement of the drums and other appa- 

 ratus used in hoisting. 



