Chap. IX. GEOLOGICAL RECORD. 287 



of one inch per century for the whole length would be 

 an ample allowance. At this rate, on the above 

 data, the denudation of the Weald must have required 

 306,662,400 years ; or say three hundred million years. 



The action of fresh water on the gently inclined 

 Wealden district, when upraised, could hardly have 

 been great, but it would somewhat reduce the above 

 estimate. On the other hand, during oscillations of 

 level, which we know this area has undergone, the sur- 

 face may have existed for millions of years as land, and 

 thus have escaped the action of the sea : when deeply 

 submerged for perhaps equally long periods, it would, 

 likewise, have escaped the action of the coast-waves. 

 So that in all probability a far longer period than 300 

 million years has elapsed since the latter part of the 

 Secondary period. 



I have made these few remarks because it is highly 

 important for us to gain some notion, however imper- 

 fect, of the lapse of years. During each of these years, 

 over the whole world, the land and the water has been 

 peopled by hosts of living forms. What an infinite 

 number of generations, which the mind cannot grasp, 

 must have succeeded each other in the long roll of 

 years! Now turn to our richest geological museums, 

 and what a paltry display we behold ! 



On the poorness of our Palceontological collections. — 

 That our palseontological collections are very imperfect, 

 is admitted by eveiy one. The remark of that admir- 

 able palaeontologist, the late Edward Forbes, should not 

 be forgotten, namely, that numbers of our fossil species 

 are known and named from single and often broken 

 specimens, or from a few specimens collected on some 

 one spot. Only a small portion of the surface of the 

 earth has been geologically explored, and no part with 



