68 



even overtake and pass through those of the chalk still suspended, 

 thus forming a bed below the chalk, or a mixed bed of chalk passing 

 into gault, and then ultimately a bed of gault above the chalk. 



In such circumstances few or none of the larger fossils would 

 occur, but possibly the remains of infusorial animals might enable us 

 to identify the material of the ancient and of the new but inverted 

 deposit of gault. 



The case of remains of human art found imbedded with bones of 

 extinct races of animals in deposits of ancient gravel, seems to 

 require a different explanation. 



Admitting, however, the existence of those animals to have been 

 contemporaneous with the original distribution of the gravel, it by no 

 means certainly follows that the race of man was coeval with them. 



For the remains of man and his rude arts might occur on the 

 surface of that gravel long ages after the extinction of those races of 

 animals. Several causes might produce their mixture : 



1st. A vast lake bursting its barriers by erosion, or by an earth- 

 quake, might carry before it in its impetuous course the superficial 

 remains of man, mixed up with vast quantities of gravel, containing 

 the bones of the extinct races of animals, and deposit them over a 

 large area of land at a lower level. 



2nd. The change of the course of a river, or of a branch of its 

 delta, might produce the same mixture of the remains of two distinct 

 and far distant ages. It might, by the clearing out of its new 

 channel, carry off the gravel and the remains of extinct animals, and 

 deposit them, mixed up with specimens of human art, on spots 

 which, after a few centuries, might again reappear as dry land. 



3rd. A narrow pass, the outlet of a stream of water, might be 

 stopped up by the avalanches falling from a glacier after a severe 

 winter, and the lake formed by the stream might thus periodically 

 rise, until the pressure broke through the barrier. 



4th. Amongst the phenomena occurring during earthquakes, it 

 has been observed that large cracks have suddenly opened and as 

 suddenly closed, either immediately or shortly after. During these 

 momentary or temporary openings, the remains of the arts of man, 

 and even man himself, may have dropped into the chasm. Under 

 such circumstances, remains of man and his arts might occur in 



