INTRODUCTION. 
5 
discover that the minor subdivisions made in northern Europe 
are quite inapplicable in the south, and that at present 
scarcely sufficient evidence exists to decide their exact equiva¬ 
lents in time. The table of foreign equivalents (pp. 222, 223) for 
this reason is purposely confined to the broad outlines. No doubt 
the deposits have been correlated more minutely, and fuller tables 
will be found in many memoirs and geological manuals, but the 
closer one studies the records of the Pliocene period, the more 
hazardous seems any attempt at correlation of the subordinate 
zones in districts 700 miles apart, divided by 10° of latitude, and 
separated by areas of which the Pliocene history is almost a blank. 
