TROPICAL NATURE 



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 or peat which absorbs 

 moisture and does not become overheated by the sun's rays, 

 and the rains are seldom violent enough to strip this protect- 

 ive covering from the surface. In tropical and even in 

 warm -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 cen- 

 turies. 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 abso- 

 lutely uninhabitable. Knowingly to produce such disastrous 

 results would be a far more serious offence than any destruc- 

 tion of property which human labour has produced and can 

 replace ; yet we have ignorantly allowed such extensive clear- 

 ings for coffee cultivation in India and Ceylon as to cause 

 the destruction of much fertile soil, which human labour 

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

 lead to the deterioration of the climate and the permanent 

 impoverishment of the country. l 



Short Twilight of the Equatorial Zone 



One of the phenomena which markedly distinguish the 

 equatorial from the temperate and polar zones is the 

 shortness of the twilight and consequent rapid transition 

 from day to night and from night to day. As this depends 

 only on the fact of the sun descending vertically instead 

 of obliquely below the horizon, the difference is most 

 marked when we compare our midsummer twilight with 



1 For a terrible picture of the irreparable devastation caused by the reckless 

 clearing of forests, see the third chapter of Mr. Marsh's work, The Earth as 

 Modified by Human Action. 



