412 BOARD OF AGRICULTURE. 



with regard to the precise method in which the forests influence 

 the production of rainfalls. Humboldt thought that the dense 

 woods gave out what he called "a frigorific, or cooling radiation," 

 which condensed the vaporous clouds ; while others supposed that 

 the tall trees attracted the frozen, or ice-clouds, and that the warm 

 vaporous clouds mixing with them became at once condensed and 

 formed the rainfuU. But let this question be settled as it may, it 

 is still proved by universal observation, that rainfalls are more 

 frequent and abundant over wooded districts and vast forests than 

 over open fields and plains. 



If this be true then, it must be evident that the forests perform 

 a most important part in the supply of watej;^ without which the 

 entire surface of the earth would be a parched and barren waste, 

 upon which no living thing could exist. In the development of a 

 subject in which so great a variety of elements are silently and in- 

 visibly operating upon each other, it is very difficult, if not impos- 

 sible, to determine the laws which govern them. We are there- 

 fore obliged to make deductions and draw inferences from various 

 observations, more or less carefully made and conducted. 



If we cast our mental vision over the whole surface of the globe, 

 wherever man has been known to exist, we find a very great 

 difference in the soils and climates of its various parts. While 

 some consist of vast deserts of sand, dry and almost treeless, 

 others are again luxuriantly clothed with woods and forests, and 

 the densest vegetable growths. While some are vast wastes of 

 cold, verdureless rocks, others are formed of gently rolling hills 

 and plains, divided by Valleys, through which run numberless 

 streams and rivers. Now if we specify some of these countries, 

 with i-eference to our subject, we shall find facts in abundance to 

 corroborate the theory that trees do influence, in a powerful man- 

 ner, the rainfalls over the whole earth, thus supplying the indis- 

 pensable amount of water ; and that wherever the forests have 

 been destroyed, the lakes and ponds have fallen off, and the 

 springs and streams have dried up, and the lands have become 

 sterile and uninhabitable. 



If we go back in point of time, we find that in the reign of the 

 Roman Emperor, Tiberius, Syria and Barbary were among the most 

 fertile regions of the world, and were heavily clothed with forests. 

 Those forests having been utterly destroyed, those regions are at 

 the present day wastes of sand and desolation. In ancient times 

 the river Scamander, which entered the Mediterranean on the north 



