Marsh. 193 



the time that rivers have occupied in wearing away their 

 present beds since they formed the gravel beds in which 

 the traces of man's skill are found ; the time necessary for 

 man to advance from his earliest condition to his present 

 state of civilization ; the time necessary for the slow ex- 

 tinction of animals, which we know to have been contem- 

 porary with early man; all these are things which must be 

 imagined, for they cannot be absolutely measured in years. 

 Definite times or limits cannot be assigned, but we know 

 that some of the remains of man are pre-Grlacial, and 

 astronomers have calculated approximately the time at 

 which the position of the earth with regard to the sun was 

 favourable for glacial conditions ; their mathematical in- 

 vestigations have led them to assign figures closely 

 approximating to those arrived at by other and indepen- 

 dent lines of thought, based on philology, geology and 

 palaeontology. 



Well, these beds of gravel have carried our minds far 

 away, but let us return to the present. To the east the 

 marshes stretch as far as the eye can see, being lost to view, 

 as, with a sudden curve, the river trends southwards, to re- 

 appear farther on ; they continue, in fact, without break until 

 Queensborough and Sheerness are reached. Before us, to 

 the north, only a few hundred yards distant, is Father 

 Thames, flowing lazily to the sea. " Lazily," did we say ? 

 Placid and peaceful enough the river looks as it wends its 

 way onwards, ever onwards, but lazy as it appears, it does a 

 great deal of work. 



It has been estimated that the river discharges into the 

 sea daily one thousand two hundred and fifty million 

 gallons of water, and that each gallon holds in suspension 



