IV] DRIFTING OF TREES. 65 



vegetable material. The following passage is taken from the 

 Principles of Geology, 



" Within the tropics there are no ice-floes ; but, as if to compensate for 

 that mode of transportation, there are floating islets of matted trees, 

 which are often borne along through considerable spaces. These are 

 sometimes seen sailing at the distance of fifty or one hundred miles from 

 the mouth of the Ganges, with living trees standing erect upon them. 

 The Amazons, the Orinoco, and the Congo also produce these verdant 

 rafts 1." 



After describing the enormous natural rafts of the Atchafa- 

 laya, an arm of the Mississippi, and of the Red river, Lyell goes 

 on to say : 



"The prodigious quantity of wood annually drifted down by the 

 Mississippi and its tributaries is a subject of geological interest, not 

 merely as illustrating the manner in which abundance of vegetable matter 

 becomes, in the ordinary course of nature, imbedded in submarine and 

 estuary deposits, but as attesting the constant destruction of soil and 

 transportation of matter to lower levels by the tendency of rivers to shift 



their courses It is also found in excavating at New Orleans, even at 



the depth of several yards below the level of the sea, that the soil of the 

 delta contains innumerable trunks of trees, layer above layer, some 

 prostrate as if drifted, others broken ofi" near the bottom, but remaining 

 still erect, and with their roots spreading on all sides, as if in their 

 natural position 2." 



The drifting of trees in the ocean is recorded by Darwin in 

 his description of Keeling Island, and their action as vehicles 

 for the transport of boulders is illustrated by the same account. 



" In the channels of Tierra del Fuego large quantities of drift timber 

 are cast upon the beach, yet it is extremely rare to meet a tree swimming 

 in the water. These facts may possibly throw light on single stones, 

 whether angular or rounded, occasionally found embedded in fine sedimen- 

 tary masses^." 



Fruits may often be carried long distances from land, and 

 preserved in beds far from their original source. Whilst 

 cruising amongst the Solomon Islands, the Challenger met 

 with fruits of Barringtonia speciosa &c., 130 — 150 miles from 

 the coast. Off the coast of New Guinea long lines of drift 



1 Lyell (67) vol. ii. p. 361. " Lyell (67) vol. i. p. 445. 



3 Darwin (90) p. 443. 



5 



