xvii Man in Nature 339 



be unable to make a living. Savage or useless creatures 

 have been exterminated over wide areas, and useful forms 

 of life introduced in their place. Sheep are now far more 

 numerous in Australia and temperate South America than 

 any indigenous species of mammal ever was. Human 

 interference can never overcome, but only take advantage of, 

 natural conditions ; and the rabbits accidentally introduced 

 to Australia happened to be so much in harmony with their 

 new surroundings that they have thriven and multiplied, so 

 as to be an intolerable plague in some districts. By human 

 agencies the horse, dog, sheep, and cow are no longer con- 

 fined to any faunal realm, and the useful plants of each of 

 the continents have been transplanted wherever suitable 

 conditions are found in all the others. Maize and tobacco 

 brighten the fields of Southern Europe, while wheat, sugar- 

 cane, and coffee spread over vast expanses of America. 

 The American cinchona and the Australian eucalyptus are 

 now invaluable to the fever-haunted lands of India, and the 

 latter tree flourishes in the swampy lowlands of the Medi- 

 terranean, while the vine and olive gladden the heart of the 

 Australians. 



434- Meteorological Changes. The regulating effect 

 of vegetation on rivers ( 417) is accompanied by an actual 

 increase in the rainfall of wooded as compared with barren 

 regions. This is so clearly recognised that in many of the 

 treeless plains of North America and Australia tree-planting 

 is encouraged by the institution of an annual holiday called 

 Arbour Day, on which each citizen is expected to plant a 

 tree. In Russia the cutting of trees is prohibited in the 

 whole belt of forests which covers the Ural -Carpathian 

 ridge, whence all the rivers of Eastern Europe flow to north 

 and south. Palestine presents a very striking example of 

 climate altered by human action. In the days of the 

 Israelites the steep mountain slopes were terraced artifi- 

 cially by walls supporting a narrow strip of soil, on which 

 grain, vines, olives, and fruit-trees of many kinds were 

 grown. The rainfall was regular and gentle ; and after 

 percolating through the terraces, formed perennial springs 

 at the foot of the slopes, feeding the brooks which rippled 



