20 



Moisture Supplied to the Air by Forests. 



The forest laad being always shaded, by the dense masses of foliage above, from the 

 summer sun, is then much cooler than the surrounding earth of the open country, a 

 ■coolness increased by the damp atmosphere within and surrounding it, produced by t^e 

 ■exhalations of the leaves, by the droppings of the great accumulations of dew, which col- 

 lect on its great extensions of leaf surface in the course of the night, and by the evapora- 

 tion from the ground itself, which, as before observed, is almost a perpetual bed of 

 moisture. The amount transpired by the leaves, as shewn' in the preceding paragraph, is 

 enormous. The forest then is continually sending out and sending upwards, dense 

 accumulations of vapour. It necessarily sends them upwards, the vapour of water being 

 the lightest and most inclined to rise of all vapours. Therefore, there will be above the 

 forest a large stratum, or it may be a column of air holding in solution as much vapour 

 ■of water as it can bear, without forming cloud, and ready, when the proper natural cause 

 ■occurs, to form a cloud, and thereafter in due time to be precipitated in rain. What may 

 ■occasion this we will speak of further on. 



Moisture Increased by Prevention op Winds. 



/ Another cause which adds to the moisture in the field surrounding a forest is the 

 great influence it exerts in modifying the force of the wind. When the stratum of air 

 immediately above the fields has, in drying the fields, taken up a portion of its moisture, 

 that moisture will pass oS" slowly to the stratum of air above, and that in turn to the 

 next above ; but if the stratum of air next to the ground be rapidly moved across the 

 ground by the wind, it is no longer simple evaporation into one stratum, that portion of 

 stratum moves off immediately with the wind, and is immediately succeeded by another 

 jportion of the same stratum, and that by another and another as rapidly as they can pass 

 ■over the ground, each in turn, taking what moisture it can rapidly imbibe. Therefore 

 a portion of country protected by an adjoining forest from rapid winds, may remain 

 although exposed to sunshine, for weeks, in good moist and growing condition, while a 

 rapid drying wind passing over it for even one day, might have taken from the ground 

 much more moisture than it could spare, and have very injuriously affected the crop. To 

 prevent this is one great use of even very thin lines of trees. 



The great Natural System which gives Rain in due Season, 



Providence gives man the means, if he choose to avail himself of them, of procuring 

 all through the growing season, frequent growth assisting showers. The means are given 

 him of continuing and preserving to himself thousands of rivulets, " the upper springs 

 and the nether springs," so th^t few good sized farms need be without a creek or sprint 

 in some corner or another, where you may always be sure of water for your cattle, without 

 having to spend hours a day pumping it from a well, and not getting then a constant sup- 

 ply, or one nearly as healthy as the stream ; without having, when wells dry, to drive 

 your cattle across your neighbour's fields, meeting his black looks, because he is sure it is 

 you who leaves his bars down, and moreover he don't calculate he'll have more water than 



