THE FOSSIL PLANTS 



231 



ined, would present any such difficulties as to make the assumption necessary 

 that they have been ejected from the interior of the earth. In cases where 

 infusoria seem to have been actually ejected from craters, as is said to have 

 been the case in some of the South American volcanoes, it is not difficult to 

 understand that an ancient crater may have become filled up and temporarily 

 converted into a lake ; and that, after the growth and deposition of an infu- 

 sorial deposit at the bottom, a new eruption may have broken out in the 

 same place as a previous one, or in its immediate neighborhood. In such a 

 case, among the ejected material a large quantity of the infusoria would be 

 found, mingled with the ashes, which must pass through the material collected 

 in the bottom of the crater as they rise from the interior of the earth. The 

 bursting of lakes at the bases of volcanic cones, caused by the rapid melting 

 of the snows above them, have often given rise to torrents of volcanic mud, 

 called "moya" in South America, in which both animal and vegetable re- 

 mains are often enclosed in great quantity ; but the connection between the 

 organic and inorganic phenomena, in such cases, is perfectly evident. 



Section III. — The Fossil Plants of the Auriferous Gravel Series. 



■ 



As the fossil plants found in connection with the auriferous gravels is the 

 subject of a special report, prepared by Mr. Lesquereux, and forming a portion 

 of the present volume, it will not be necessary to devote any considerable 

 part of this chapter to that branch of the subject. Some additional informa- 

 tion, however, may with propriety be given in regard to certain points 

 connected with the mode of occurrence, the distribution and the relative 

 abundance of the remains of a former vegetation imbedded in the detrital 

 deposits which have been described in the preceding chapter. Such general 

 considerations as properly connect themselves with the climatic conditions 

 prevailing at the time of the growth of the plants in question may, in accord- 

 ance with the plan of this volume, be reserved for a future chapter. 



From what has been stated in the preceding pages it will have been in- 

 ferred that the remains of vegetable life, in the form of trunks of trees, 

 impressions of leaves, and the like, are of common occurrence in the strata 

 worked by the hydraulic mining process. This is indeed the case ; for from 

 the most southern to the extreme northern localities mentioned, in the de- 

 tailed description of the gravel region, there seem to be but few districts 

 where such remains have not been noticed. The material which could be 



