20 TROPICAL NATURE, AND OTHER ESSAYS. 



vast storage tanks and will serve to fertilise a great 

 extent of country ; whereas tanks without regular rain- 

 fall or permanent springs to supply them are worthless. 

 In the colder parts of the temperate zones, the absence 

 of forests is not so much felt, because the hills and 

 uplands are naturally clothed with a thick coating of 

 turf which absorbs moisture and does not become over- 

 heated by the sun's rays, and the rains are seldom 

 violent enough to strip this protective covering from the 

 surface. In tropical and even in south-temperate 

 countries, on the other hand, the rains are periodical 

 and often of excessive violence for a short period ; 

 and when the forests are cleared away the torrents 

 of rain soon strip off the vegetable soil, and thus 

 destroy in a few years the fertility which has been the 

 growth of many centuries. The bare subsoil becoming 

 heated by the sun, every particle of moisture which does 

 not flow off is evaporated, and this again reacts on the 

 climate, producing long-continued droughts only relieved 

 by sudden and violent storms, which add to the 

 destruction and render all attempts at cultivation 

 unavailing. Wide tracts of fertile land in the south 

 of Europe have been devastated in this manner, and 

 have become absolutely uninhabitable. Knowingly to 

 produce such disastrous results would be a far more 

 serious offence than any destruction of property which 

 human labour has produced and can replace ; yet we 

 ignorantly allow such extensive clearings for coffee 

 cultivation in India and Ceylon, as to cause the destruc- 

 tion of much fertile soil which generations cannot 

 replace, and which will surely, if not checked in time, 



