RECORDS LEFT BY THE SEA 



iron, so its salts and acids must eat their way into many 

 rocks. 



But, after all, the coast-line of the world is a small 

 fraction of the whole land surface of the globe ; and a 

 smaller fraction of the sea^s own wide area. On that area 

 are flung all the records and treasures which the sea has 

 wrested from the land. The rivers, as we have already 

 several times repeated, are the chief carriers of deposits 



to the sea. By their deltas they may be known. The 



^# 

 deltas of the Ganges^Ktd Brahmaputra cover an area as 



large as that of England and Wales. The delta has been 

 bored through to a depth of nearly five hundred feet, and 

 has been found to consist of numerous alternations of fine 

 clays, marls, and sands or sandstones, with occasional 

 layers of gravel. In all this accumulation of sediment 

 there are no traces of marine animals ; but land plants 

 and the plants and animals of the river and of the sur- 

 rounding land have been discovered in quantity. The sea 

 most often destroys land ; but it sometimes deposits 

 beaches ; and, we might almost say, silts up the land. At 

 Romney Marsh, for example, a tract of eighty square miles 

 which was marsh in Julius Caesars time is now dry land, 

 and has become so partly by the natural increase of 

 shingle thrown up by the waves. The coarsest shingle 

 usually accumulates towards the upper part of the beach, 

 and the rest arranges itself generally according to size 

 and weight, that which is finest being nearest to low- 

 water mark. 



It is often long before the stuff brought down by the 

 rivers settles on the floor of the ocean. The finer particles 



60 



