332 Mr. Hinds on Climate, ^c Humidity. 



Frequently the water itself is supposed to contain nutritive 

 qualities, which, though not distinguishable to the eye or 

 taste, are unquestionable from the superior luxuriance of the 

 subsequent vegetation. It is not improbable that vegetable 

 matter may become so mixed up in the water of some of 

 these rivers, as not to be perceptible to ordinary examination. 

 It must be remembered that they often take their rise in 

 high and mountainous regions, and have to pursue a course 

 to the ocean sometimes of thousands of miles, continually 

 deflected from the straight course by chains of hills, falling 

 in frequent cascades, tumbling over huge rocks, and boiling 

 in eddies and whirlpools. A dense vegetation covers the 

 country through which they roll, and overhangs its banks ; 

 trees, undermined or falling through age, are precipitated into 

 the stream ; the large sear leaves of the autumn of a tropic 

 forest are wafted there by every breeze, and before they find 

 their way to the ocean much has become comminuted and 

 dissolved. It is easy then to account for the luxuriant vege- 

 tation on the banks of the Ganges, Niger, Amazon, and simi- 

 lar rivers, and to appreciate the vast fertility which their over- 

 flowing waters carry with them, and the misery and sterility 

 consequent on a sparing wet season. 



Vegetation is capable of appropriating a large quantity of 

 moisture, particularly in the active stages of its growth : nu- 

 merous experiments have been made to ascertain the amount 

 a plant will take up ; in one of these, by Hales, a pear-tree 

 weighing 71 lbs. was allowed to imbibe as much moisture as 

 it was able for the space of six hours, when it was found that 

 fifteen pounds of water had disappeared. It is interesting to 

 observe how very much the parts of plants are fashioned ac- 

 cording to the kind of climate they are destined to live under : 

 in the tropics, where the climate is warm and moist, plants 

 are clothed with large flaccid leaves in great numbers, and 

 flowers are not very abundant in this variety ; if the air is 

 warm and tending to dryness the fohage is much smaller; 

 Leguminosae and their compound leaves prevail, and the struc- 

 ture is leathery and dry. Very peculiar is the vegetation of 

 a country eminent for dryness : its plants are adapted in their 

 organization to the circumstances around them ; the leaves are 

 provided with comparatively few stomata or evaporating pores, 

 ajid are so many magazines of moisture ; the leaves are also 

 small in size, or if large, cut and divided, to offer the more 

 surface for absorption. The flora of the Cape of Good Hope 

 is very peculiar, and has much of this character ; among its 

 numerous bulbous and succulent plants, heaths, and Prote- 

 acese, the features of its climate are easily read. I have 



