180 J. I. LOBLEY — THE STUDY OF GEOLOGY. 



of Africa, that the mountains of Abyssinia give us the plains of 

 Egypt, that the Athis range protects the desert of Sahai'a and the 

 northern regions, and that the great central highlands give width 

 to the continent. 



But in our own island of Great Britain this relation of the form 

 of the land to its mountains is conspicuously observable. On our 

 western coasts, where the sea beats with great force, we have high 

 lands and hard rocks, extending almost from the most southern to 

 the most northern point, and thus our island is protected from 

 destruction. The irregular outline of Scotland will be found 

 to be intimately connected with the extent and direction of her 

 mountains, and the same relation of the coast-line with mountains 

 is to be observed in the north of England and in Wales, while the 

 promontory of Cornwall is due to the uplifted masses of granitic 

 rocks which characterise the south-west extremity of Great Britain. 

 The east and south-east of England is formed, it is true, of com- 

 paratively soft rocks and low lands, without any bounding high 

 lands except the South Downs. But these lands could not have 

 existed had the sea been acting with the same destroying power 

 as on the west coast. The sea on the eastern shores of England, 

 although wearing away the cliffs in some places, is depositing and 

 forming land in others, and on the whole is acting with compara- 

 tively little force. But even on this eastern coast of Britain, 

 where we see a projecting headland, as at Flamborough Head, or 

 at Scarborough Castle, somewhat harder rocks and more elevated 

 land will be found than where the retreating coast-line forms bays 

 and indentations. 



And as the mountain ranges determine the form of the land, so 

 also do they determine the climate, and the character of their 

 adjacent districts, and even the occupations of the inhabitants. 

 For it is the mountain chains which form the watersheds, and 

 determine the size and the direction of the great rivers which form 

 the plains and deltas, irrigate the land, and facilitate commerce. A 

 watershed is of course the summit-line of a range of mountains, 

 hills, or high lands. These watersheds or summit-lines are in 

 many instances more effectual dividers of floras, of faunas, and 

 even of races of men, than wide rivers or deep seas. 



Watersheds form the boundaries of river-basins, and hydro- 

 graphical areas, which are often very distinct geographical divisions 

 of the earth's surface. Thus we have in America the great river- 

 basins of the Mississippi, of the St. Lawrence, of the Amazon, and 

 of the La Plata, forming very large and very distinct portions 

 of the continent. So in Europe, the area di'ained by the Rhine 

 is distinct in climate and productions from the area drained by the 

 Danube, the Volga, the Vistula, or the Po. In England, too, we 

 have the basins of the Thames, of the Severn, of the Trent, and of 

 the Ouse, forming very well-marked portions of the kingdom. 



When we reflect that all these great features of the globe on 

 which we live, so profoundly important as they are to all the 

 interests of the human race, are the result of geological causes, we 



