ELEOTKICAL IKFLTTEPrOE OF TREES. 151 



Elect/rical Inf/uence of Trees-. 



The properties of trees, singly and in groups, as exciters or con- 

 ductors of electricity, and tlieir consequent influence upon the 

 electrical state of the atmosphere, do not appear to have been 

 much investigated ; and the conditions of the forest as a whole 

 are so variable and so compHcated, that the solution of any gen- 

 eral problem respecting its electrical influence would be a matter 

 of extreme difficulty. It is, indeed, impossible to suppose that a 

 dense cloud, a sea of vapor, can pass over miles of surface bris- 

 tling with good conductors, without undergoing and producing some 

 change of electrical condition. Hypothetical cases may be put in 

 which the character of the change could be deduced from the 

 known laws of electrical action. But in actual nature the ele- 

 ments are too niunerous for us to seize. The true electrical con- 

 dition of neither cloud nor forest could be known, and it could 

 seldom be predicted whether the vapors would be dissolved as 

 they floated over the wood, or discharged upon it in a deluge of 

 rain. With regard to possible electrical influences of the forest, 

 wider still in their range of action, the uncertainty is even greater. 

 The data which alone could lead to positive, or even probable, con- 

 clusions are wanting, and we should, therefore, only embarrass 

 our argument by any attempt to discuss this meteorological ele- 

 ment, important as it may be, in its relations of cause and effect 

 to more familiar and better understood meteoric phenomena. It 

 may, however, be observed that hail-storms — which were once 

 generally supposed, and are still held by many, to be produced 

 by a specific electrical action, and which, at least, appear to be 

 always accompanied by electrical disturbances — are beheved, in 

 all countries particularly exposed to that scourge, to have become 

 more frequent and destructive in proportion as the forests have 

 been cleared. Caimi observes : " When the chains of the Alps 

 and the Apennines had not yet been stripped of their magnificent 

 crown of woods, the May hail, which now desolates the fertile 

 plains of Lombardy, was much less frequent ; but since the gen- 

 eral prostration of the forest, these tempests are laying waste even 

 1;he mountain-soils whose older inhabitants scarcely knew this 



