TREES ATTRACTORS OF HUMIDITY. 49 



ascending a hill in the month of March. The weather 

 had previously been very fine and dry, and the road in 

 a dusty state ; but a fog coming on, an ash tree hanging 

 over the road was dripping with water so copiously, 

 that the road beneath was in a puddle, when the other 

 parts continued dry, and manifested no appearance of 

 humidity. That leaves imbibe moisture by one set of 

 vessels and discharge them by another, is well-known ; 

 but these imbibings are never discharged in falling 

 drops : the real mystery was, the fog in its progress was 

 impeded by the boughs of the tree, and gradually col- 

 lected on the exposed side of them, until it became 

 drops of water, whereas the surrounding country had 

 only a mist flying over it. Thus in fact the tree was 

 no attractor, but a condenser ; the gate of a field will 

 in the same manner run down with water on the one 

 side, and be dry on the other ; as will a stick, or a post, 

 from the same cause. It is upon this principle that 

 currents of air will be found under trees in summer, 

 when little is perceived in open places ; and the under 

 leaves and sprays will be curled and scorched at times, 

 when the parts above are uninjured. The air in its 

 passage being stopped and condensed against the foliage 

 of the tree, it accordingly descends along its surface 

 or front, and escapes at the bottom, where there are no 

 branches or leaves to interrupt its progress. In winter 

 there is little to impede the breeze in its course, and it 

 passes through; consequently at this 'season the air un- 

 der a tree is scarcely more sensibly felt than in the ad- 

 joining field. 



It may be observed, that in the spring of the year 

 the herbage under trees is generally more vivid and 

 luxuriant, than that which is beyond the spread of the 

 branches : this may be occasioned, in some instances, 

 by cattle having harbored there, and the ground becom- 

 ing in consequence more manured ; but it will be found 

 likewise manifestly verdant and flourishing where no 

 such accessory could have enriched it, and is, I appre- 

 hend, in general, chiefly owing to the effects of the 

 driving fogs and mists, which cause a frequent drip be- 

 neath the tree, not experienced in other places, and 



Tj! 





