334 The Realm of Nature CHAP. 



and enthusiastic ; they are passionate, inconstant, and fond 

 of ease. These two types evidently represent different 

 races ; but they have mingled so thoroughly that any 

 attempt at exact classification is now impossible, although 

 some indefinite but very interesting subdivisions have been 

 made out. 1 



427. Distribution of the Human Race. The esti- 

 mated population of the world is 1,470,000,000 people. 

 These are all dependent for their means ofTIFe on the 

 land, and the densest population, that is the greatest 

 number living on a given area, is necessarily found where 

 the land is richest in useful productions. Deserts are 

 practically unpeopled ; the few inhabitants live on the pro- 

 duce of the s date-trees of the oases and on the aid given 

 them by passing caravans, to which the oases afford in- 

 valuable halting -places. Steppe -lands can carry more 

 inhabitants, who as a rule are wandering shepherds feeding 

 their flocks on the best grass they can find, and moving on 

 to " pastures new " when the ground is cropped bare. 

 Well -watered lands, when naturally treeless, or after the 

 trees have been cleared, yield to agriculture abundance of 

 food and material for clothing, hence such countries can 

 support many inhabitants. The crowded Nile delta, the 

 river-plains of China, and the valley of the Ganges are the 

 most densely peopled parts of the Earth, on account of the 

 fertility of the ever-renewed soil allowing large crops of 

 food-plants to be raised at moderate expense. The question 

 of the production of food is the most important in order to 

 find how many people a given country can support. Mr. 

 Ravenstein calculates that with proper treatment of the land 

 about 6,000,000,000 inhabitants should be comfortably pro- 

 vided for on the Earth, a number which, if the present 

 rate of increase continues, will be attained in less than 200 

 years. 2 There are other wants besides food, and by the divi- 

 sion of labour made possible by the organisation of civilised 

 life, a large population may be engaged in working mines or 

 carrying on manufactures in regions where sufficient food 

 for them cannot be grown. The supply of bread and meat 

 is kept up by trade with their fellow- workers on lands 



