THEIR INCESSANT OPERATIONS. 37 



battle-fields mentioned in ancient history, the sites of cities 

 and harbours, the courses of rivers, and the contour of 

 mountains, are much the same as when described one thou- 

 sand, two thousand, or even four thousand years ago. But 

 to him who looks a little more narrowly the case is altogether 

 different. The stream in the valley has cut for itself a 

 deeper channel, and has repeatedly shifted its course eating 

 away the banks on one side, and laying down spits of new 

 ground on the other. The cliffs in the hills are more 

 weather-worn and rounded, and a larger mound of rock-debris 

 has accumulated at their bases. The lakes of the old his- 

 toric plain are partly converted into marshes, and the marshes 

 into meadow-land ; the site of the old city on the sea-cliff 

 has been partly wasted away by the encroaching waves ; 

 and the ancient harbour, once at the river-mouth, is now a 

 goodly mile inland, and separated from the sea by a flat 

 alluvial delta. The Nilotic plain is not precisely the same 

 as when described by Herodotus ; the sunderbunds or mud- 

 islands of the Ganges have been largely augmented during 

 the last two hundred years ; and many areas that were laid 

 down on the charts of our earlier traders as mud-flats, now 

 form fertile portions of the great Chinese plain. Vesuvius 

 has repeatedly changed its aspects since Herculaneum and 

 Pompeii were buried beneath its ejections; and there is 

 scarcely an active volcano that has not materially added to 

 its bulk since the commencement of the current century. 



Such changes are incessant, and though individually they 

 may seem insignificant, yet when viewed in the aggregate, 

 and continued from century to century, they assume a mag- 

 nitude commensurate with the crust of the globe itself, 

 every portion of which has repeatedly suffered degradation 

 and renovation, been repeatedly spread beneath the waters as 

 sediment, and as repeatedly reconstructed into newer strata 

 and upheaved into dry land. Imperceptibly as the rains 



