AS AFFECTED BY THE "TRADES." 259 



have lost, together with their forests,, much of their 

 flourishing condition, and have even been changed, 

 in part, into desert. But you will also see that, 

 by gradually planting trees, many regions of our 

 earth, which have been hitherto waste and barren, 

 may be rendered fit for tillage and the dwelling of 

 man. 



The air is in general moister over the sea than 

 on the land ; least so, however, in the region of 

 the trade-winds. It there flows from colder to 

 warmer regions, and so, its temperature gradually 

 increasing as it advances, its power of taking up 

 moisture is more and more enhanced. Within the 

 region therefore of the trade- winds, the atmosphere 

 is clearer, and rain scarcer. But between the north- 

 east and south-east trades, in the belt of the calms, 

 where the surface of the sea receives most warmth, 

 and where, therefore, air fully charged with water 

 is ever rising and spreading itself out, and thus is 

 cooled down by degrees below the dew-point, it 

 rains regularly every afternoon. The domain of 

 the calms advances, as you know, and retreats 

 with the sun ; the rainy season sets in wherever it 

 comes ; and the dry season where the trade-wind 

 prevails. Between the two periods there is a 

 regular interchange, so that the former always 

 answers to the highest, and the latter to the lowest, 

 position of the sun. Thus it rains in the West 

 Indies during the summer months, and is dry 



s 2 



