BOTANY. 331 



where trees have been cut down, springs have disappeared. In India, a 

 few years since, a proprietor, in laying down some ground, well watered 

 by an excellent spring, for a coffee garden, at Genmore, despite the ad- 

 vice of the natives, cleared the adjacent ground, when the supply of 

 water vanished. Cases are also cited, where the clearing of jungles 

 was followed in every case by an almost immediate diminution of water ; 

 when the jungle was allowed to grow again, the water returned, the 

 springs were opened and flowed as ibrmerly. The St. Helena Almanac, 

 for 1848, gives particulars of the increase of the fall of rain for the last 

 few years, attributable to the increase of wood ; within the present 

 century the fall has nearly doubled. The plantations seem to have 

 performed another service to the island. Formerly, heavy floods, 

 caused by sudden torrents of rain, were almost periodical, and fre- 

 quently very destructive ; for the last nine years they have been un- 

 known. On the mountains of Ferro, one of the Canary Islands, there 

 are trees, each of which is constantly surrounded by a cloud ; their 

 power of drawing down moisture is well known to the people. The 

 natives call them gawl, the Spaniards santo, from their utility. The 

 drops trickle down the stem in one unceasing stream, and are collected 

 in reservoirs constructed for their reception. The whole of this beau- 

 tiful process depends upon the simple laws of temperature, condensa- 

 tion and evaporation. Trees shade the soil from the sun. They give 

 off vapor during the clay, and so mitigate heat, while they obstruct the 

 direct rays from above ; they radiate heat out during the night, and 

 occasion the precipitation of dew at night many plants being en- 

 dowed with this faculty to such an extent as to collect water in large 

 quantities from the air. 



In a discussion which occurred in the British Association, on the 

 influence of forests on climate, Capt. Strachey said he could not agree 

 with those who thought that forests had much influence on climate. 

 It was a notion that they encouraged rain ; but it was more probable 

 that rain was the cause of forests. He alluded to districts in India, 

 in which the forest vegetation was just in proportion to the fall of rain ; 

 being small and diminutive where there was little rain, and abundant 

 and gigantic where there was much rain. In temperate climates forests 

 might produce an effect, but certainly not in the tropics. With regard 

 to the economical question, there could be no doubt that it was foolish 

 to destroy what was valuable, but we had not the power to arrest the 

 present destruction of the forests in India. Mr. Bunbury enumerated 

 several instances where forests did not exist, and yet there was much 

 rain, and others, where forests existed, and there was little rain. 

 Humboldt was our great authority on this subject, and he had recorded 

 his opinions of the influence of forests on climate. In many districts 

 where forests were cleared and single individuals left, these latter soon 

 died from the want of the influence of their neighbors. Dr. Lankester 

 pointed out that, according to the laws of vegetation, plants must be 

 supplied with water in a liquid or vaporous form for their growth, and 

 that all the facts which had been mentioned, and which at first sight 

 appeared opposed to each other, might be explained. That forests did 

 not always grow in rainy districts, arose probably from the waters 



