A HISTORY OF KENT 



Secondary division and embrace portions of the Paleozoic or Primary 

 rocks also. By reference to Table I. on the next page the extent of 

 these additions to our knowledge will be readily grasped. 



The geology of the county therefore falls naturally under two 

 heads : {a) the study of the outcropping strata and of the features to 

 which they give rise ; and (^) the study of the deep-seated rocks found 

 only in the borings and having little or no effect upon the outline 

 of the present surface. 



It is customary in geological literature to commence with the 

 description of the oldest formation and to work upward through the 

 sequence. But for our present purpose this method is hardly suitable, 

 since the most difficult and technical part of our subject, and that respect- 

 ing which our knowledge is necessarily restricted, would have to be 

 considered first. The simpler method will be to give precedence to 

 the description of the surface formations of the county in the above- 

 mentioned order, and to discuss the results of the deep borings after- 

 wards under a separate heading. 



The tables which follow will serve as indices to the stratigraphical 

 sequence : the first gives a summary of the rock systems commonly 

 adopted as the geological time-scale, with an indication of the portions 

 known to exist in Kent ; and the second contains the fuller classification 

 and sub-division of the Kentish strata. 



SUMMARY OF ROCK-SYSTEMS 



