24 ON A PIECE OF CHALK i 



that life, the chalk period must have had a much 

 longer duration than that thus roughly assigned 

 to it. 



Thus, not only is it certain that the chalk 

 is the mud of an ancient sea-bottom ; but it is no 

 less certain, that the chalk sea existed during an 

 extremely long period, though we may not be 

 prepared to give a precise estimate of the length 

 of that period in years. The relative duration is 

 clear, though the absolute duration may not be 

 definable. The attempt to affix any precise date 

 to the period at which the chalk sea began, or 

 ended, its existence, is baffled by difficulties of the 

 same kind. But the relative age of the cretaceous 

 epoch may be determined with as great ease 

 and certainty as the long duration of that epoch. 



You will have heard of the interesting dis- 

 coveries recently made, in various parts of Western 

 Europe, of flint implements, obviously worked into 

 shape by human hands, under circumstances which 

 show conclusively that man is a very ancient 

 denizen of these regions. It has been proved that 

 the whole populations of Europe, whose existence 

 has been revealed to us in this way, consisted of 

 savages, such as the Esquimaux are now ; that, in 

 the country which is now France, they hunted the 

 reindeer, and were familiar with the ways of the 

 mammoth and the bison. The physical geography 

 of France was in those days different from what it 



