GEOLOGY 



INTRODUCTION 



IF it were possible completely to trace the series of changes which 

 any part of the earth's crust has undergone, geological history would 

 everywhere embrace the whole vast range of time that has passed in 



the shaping of our planet to its present form. But in no place is 

 more than a very small fragment of the record exhibited. The effects 

 of the great cycles of earth-development have been ever varying from 

 place to place. With the elevation of one tract into dry land, and the 

 wearing down of its surface by the agents of sub-aerial erosion, there 

 has gone on concurrently the depression of a neighbouring area beneath 

 the waters, wherein the materials derived from that land were spread out 

 in layers of sediment to become the solid strata of a newer land. Over 

 every part of our country this chain of vicissitudes has passed unbrokenly 

 since the remotest times to which our knowledge can reach, and it is still 

 passing. The records of the older epochs are ground down into material 

 for the newer history, even as the paper-maker may reduce old docu- 

 ments to pulp which shall in turn become a vehicle for later knowledge. 



To use the well-worn but none the less faithful simile, the geo- 

 logical register is everywhere the mere fragment of a volume, with here 

 and there a leaf or often only part of a leaf remaining ; and it is the aim 

 of the geologist to reconstruct the history of the past from these frag- 

 ments. We might even pursue the simile further, and speak of the 

 geology of a limited district as the fragmentary copy of a work of world- 

 wide distribution, decipherable only by comparison and correlation with 

 similarly imperfect copies found in other districts in constantly varying 

 states of mutilation. From this point of view, our Surrey record is a 

 fragment containing portions of the later chapters only, with by far the 

 greater part of the volume missing. 1 



In other words, of the three great groups into which we divide the 

 fossiliferous rocks, namely, Palaeozoic (computed to represent in time- 

 value nine-tenths of the whole), Mesozoic or Secondary, and Cainozoic or 

 Tertiary, the strata actually visible in the county (excluding the com- 

 paratively recent ' superficial ' deposits) belong entirely to the later part 

 of the Mesozoic and the earlier part of the Cainozoic. It is true that, 

 as will be shown in the context, older rocks are known to exist at some 

 distance below ground, but these are too deeply buried to affect the 

 present land-surface, and our knowledge respecting them is limited to 

 the bare fact that they have been found in certain deep borings. 



1 For detailed information regarding the geology of Surrey generally, the following 

 Memoirs of the Geological Survey may be consulted : The Geology of the Weald, by W. Topley 

 (1875), for the beds below the base of the Chalk and for matters connected with the valley 

 systems of the Weald, and its denudation ; The Geology of the London Basin, by W. Whitaker 

 (1872), for the Chalk and Eocene beds; The Geology of London and of part of the Thames 

 I I B 



