tj THE THAMES. 19 



ground is only relatively high; but the water easily finds 

 the slope, however small, and runs down it, thus showing at 

 once the direction of the water-parting. 



A little consideration will show that water-partings may 

 be drawn on a map of any country, so as to divide the 

 entire region into a series of river-basins. Plate II. is a 

 map of Great Britain and Ireland thus completely divided 

 into river-basins, separated one from another by water- 

 partings, which are indicated by dotted lines. All the 

 rivers which empty themselves into the sea on the eastern 

 side of Britain may, in this way, be separated from those 

 which run into the western seas, and both systems may be 

 separated from the southern rivers which open into the 

 English Channel : the northern drainage is insignificant. 

 We thus obtain the general water-parting of Great Britain, 

 distinguished in the map by a line of red dots. This is a 

 sinuous line running from near John-o'-Groat's House, 

 through Scotland and the north of England, down the Peak 

 of Derbyshire and through the Midland counties, till it gets 

 as far south as Salisbury Plain. Such a line divides the 

 western drainage of the country from its eastern drainage. 

 At Salisbury Plain the line splits into two branches, one 

 stretching to the east coast and terminating somewhere 

 about Dover, the other striking to the west coast and ter- 

 minating at the Land's End. To the south of this great 

 east-and-west line, all the rivers flow into the English 

 Channel. This three-branched hne consequently represents 

 the main water-parting of the country; it is in fact the gene- 

 ral high-level line of Britain, though it has no direct relation 

 to the mountain-systems of the country. The main water- 

 partings of Ireland are also indicated on the map, the rivers 

 being grouped in four great systems, which drain to the 

 north, south, east, and west. 



C 2 



