1898-99. | On some Geological Agents. 27 
destruction were well illustrated round our coast in October 
last year. Aided by wind and tide, it washed away the land 
and undermined the solid rock of the cliff by pounding it 
with materials torn from its own massive side. In this rude 
and boisterous fashion it eats away the land, forming islands, 
channels, and bays. And by the same means and in the same 
manner Great Britain was made an island—to the disgust of 
our friends on the other side of the Channel, who would fain 
shake hands with us on some occasions. 
And man as the last agent. Man, especially since the time 
that he discovered the use of fire and metals, has been the 
cause of geological changes on the surface of the earth. Read- 
ing the early history of man in the East, we learn that he 
brought the greater part of Western Asia into a condition of 
great fertility, capable of supporting a large population in a 
high state of civilisation. Looking at the same region in the 
present day, we see the desert sand covering what were culti- 
vated fields and vineyards in the past: the trees have been 
cut down, and the water has ceased to flow,—for all which 
the ignorance of man and bad rulers are responsible. 
But if man, through ignorance, idleness, and bad govern- 
ment, has allowed a large area of Asia Minor, Northern 
Africa, and some other countries on the shores of the Mediter- 
ranean to run to waste, he has by industry, perseverance, and 
science changed the physical features of the earth in many 
other quarters of the world. In the cold and rigorous climate 
of Germany, Holland, Great Britain, and North America he 
has converted the impenetrable forest, the swamp, and the 
mountain side into fields of wheat, corn, and grassy pasture, 
producing food and shelter for himself and the useful animals 
that he has brought under his dominion and protection. 
But the cultivation of the soil is an agent of geological 
change, by frequently exposing the loose surface to the 
denuding action of rain. It is only necessary to look at 
a ploughed field on a gentle slope during a heavy shower 
of rain to be convinced that the soil is being rapidly washed 
away towards the river, and by the river to the sea. Who 
ean calculate how much the land will be lowered in our own 
Lothians by the works of men during the next thousand 
years ? 
