560 STEVENSON— FORMATION OF COAL BEDS. [November 3. 



" While dredging to the leeward of the Caribbean islands, we could not 

 fail to notice the large accumulation of vegetable matter and of land debris 

 brought up from deep water many miles from the shore. It was not an un- 

 common thing to find at a depth of over one thousand fathoms, ten or 

 fifteen miles from land, masses of leaves, pieces of bamboo and sugar cane, 

 dead land shells and other land debris, undoubtedly blown out to sea by the 

 prevailing trade winds. We frequently found on the surface masses of 

 vegetation, more or less waterlogged and ready to sink." 



The violent hurricanes of the Caribbean, as described by Maury, 

 must contribute very largely to the mass of vegetable material. 

 Agassiz found similar conditions at the bottom of the Pacific during 

 the cruise of the Albatross, when he was surprised at the distance to 

 which land-derived material had been carried. Along most of the 

 distance between Acapulco and the Galapagos islands as well as all 

 along the coast from Acapulco northward to within the Gulf of Cali- 

 fornia, there is a very sticky mud covering the bottom and inter- 

 fering seriously with the work of dredging. His description of con- 

 ditions between Acapulco and the Galapagos is 



" Nearly everywhere along our second line of exploration, except on face 

 of the Galapagos slope, we trawled along a bottom either muddy or com- 

 posed of Globigerina ooze, more or less contaminated with terriginous 

 deposits and frequently covered with a great amount of decayed vegetable 

 matter. We scarcely made a trawl which did not bring up a considerable 

 amount of decayed vegetable matter and frequently logs, branches, twigs, 

 seeds, leaves, fruits, much as during our first cruise." 



The conditions were similar along the continental coast. The 

 trawl was ordinarily well filled with mud along with the usual supply 

 of decayed vegetable matter. Observations of like character have 

 been made by others elsewhere in the Pacific. 



In all probability, a great part of the vegetable matter swept out 

 to sea disappears by oxidation at the surface or in the depths ; but 

 in favorable localities another great part is deposited in fragmentary 

 condition with fine muds on the bottom, there eventually to form 

 beds of carbonaceous shale. 



Conclusions. — The grouping of facts presented in the preceding 

 pages, proving shnilarity of conditions in all parts of the world, 

 seems to justify the following conclusions: 



I. If torrents carry clear water, they produce little efifect on 



158 



