62 ON A PIECE OF CHALK 



the length of that life, the chalk period must have had 

 a much longer duration than that thus roughly as- 

 signed 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 esti- 

 mate 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 discoveries 

 recently made, in various parts of Western Europe, of 

 flint implements, obviously worked into shape by hu- 

 man hands, under circumstances which show conclu- 

 sively that man is a very ancient denizen of these re- 

 gions. 



It has been proved that the old 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 

 is now the river Somme, for instance, having cut 

 its bed a hundred feet deeper between that time and 

 this; and, it is probable, that the climate was more like 

 that of Canada or Siberia, than that of Western 

 Europe. 



