328 PALEONTOLOGY. 



that Hunter found time, and had the disposition and the perceptive 

 faculty to note also, the geological phenomena of Portugal, and the 

 deductive power to frame and store up conclusions as to the geological 

 dynamics that had operated on the scene of his encampment. Yet it 

 was from observations at this period of his life and in Portugal, that he 

 derived his ideas of one of the modes in which a retiring sea acts upon 

 an uprising continent, and also of the slow and gradual mode of that 

 operation. 



" The extensive fiat tract of land in Portugal called Alentejo, shows," 

 he writes, " evident signs upon its surface of having been covered by 

 the sea. There is a vast extent of fiat country going to Portalegra 

 covered with loose gravel, apparently of considerable depth ; and there 

 are also considerable heights composed of such materials ; but those 

 composing heights are cemented together like plum-pudding stone, 

 only the cement is not so strong ; which cement was probably the cause 

 of their retaining this situation and form. 



" But the most striking evidence of the sea having once covered this 

 tract, and afterwards having left it gradually, is the peculiar shape of 

 the remains of those elevations of gravel ; for it would appear that as 

 the sea left their tops exposed, the pebbles were washed off by 

 the motion of the surface of the water where this motion is greatest ; 

 and, as the sea subsided, the lower part of such risings, beyond the 

 general surface or basis, were longer washed by it than the top ; con- 

 seqiiently more of the gravel was washed away, till at last they became 

 of a pyramidal figure standing on their apex .... and all round, on 

 the flat surface, is strewed the gravel washed off the rising part which 

 now forms the inverted pyramids." 



He adds, " If the sea was to leave the Isle of Wight, the Needles 

 would exhibit something of this kind." — P. xvi. 



The distinguished geologists who may have honoured this theatre by 

 their presence, will need no other or better proof of Hunter's powers 

 in his new character, as a pure geological observer, than the instance 

 which I have just quoted. 



Besides the aqueous causes which Hunter recognizes as operative in 

 mollifying the surface of the earth, exemplified by the effects of running 

 water, as in valleys and river-courses, by the operation of a retiring 

 sea upon a rising land, by deposition varied according to the different 

 distances to which matters according to their size, &c. would be trans- 

 ported and spread over the sea-bottom, and by the action of the sea on 

 coasts as moved by tides and winds — I would remark that, in addition 

 to these Neptunian dynamics. Hunter does not overlook the agencies of 

 the Plutonists : — 



