I CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 231 



conditions. Whether we are at Singapore or Batavia, in the 

 Moluccas or New Guinea, at Para, at the sources of the 

 Rio Negro, or on the Upper Amazon, the equatorial climate 

 is essentially the same, and we have no reason to believe that 

 it materially differs in Guinea or the Congo. In certain 

 localities, however, a more contrasted wet and dry season 

 prevails, with a somewhat greater range of the thermometer. 

 This is generally associated with a sandy soil, and a less dense 

 forest, or with an open and more cultivated country. The 

 open sandy country with scattered trees and shrubs or occa- 

 sional thickets, which is found at Santarem and Monte- Alegre 

 on the lower Amazon, are examples, as well as the open 

 cultivated plains of Southern Celebes ; but in both cases the 

 forest country in adjacent districts has a moister and more 

 uniform climate, so that it seems probable that the nature of 

 the soil or the artificial clearing away of the forests, are 

 important agents in producing the departure from the typical 

 equatorial climate observed in such districts. 



Effects of Vegetation on Climate 



The almost rainless district of Ceara on the north-east coast 

 of Brazil, and only a few degrees south of the equator, is a strik- 

 ing example of the need of vegetation to react on the rainfall. 

 We have here no apparent cause but the sandy soil and bare 

 hills, which, when heated by the equatorial sun, produce ascend- 

 ing currents of warm air and thus prevent the condensation of 

 the atmospheric vapour, to account for such an anomaly ; and 

 there is probably no district where judicious planting would 

 produce such striking and beneficial effects. In Central India 

 the scanty and intermittent rainfall, with its fearful accom- 

 paniment of famine, is perhaps in great part due to the 

 absence of a sufficient proportion of forest -covering to the 

 earth's surface ; and it is by a systematic planting of all the 

 hill -tops, elevated ridges, and higher slopes that we shall 

 probably cure the evil. This would almost certainly induce 

 an increased rainfall ; but even more important and more 

 certain is the action of forests in checking evaporation from 

 the soil and causing perennial springs to flow, which may be 

 collected in vast storage tanks and serve to fertilise a great 

 extent of country ; whereas tanks without regular rainfall or 



