140 
ELECTEICAL INFLUENCE OF FOREST. 
Electrical Influence of Trees. 
The properties of trees, singly and in groups, as exciters or 
conductors of electricity, and their consequent influence upon 
the electrical state of the atmosphere, do not appear to have 
been much investigated; and the conditions of the forest itself 
are so variable and so complicated, that the solution of any 
general problem respecting its electrical influence would be a 
matter of extreme difficulty. It is, indeed, impossible to sup¬ 
pose that a dense cloud, a sea of vapor, can pass over miles of 
surface bristling with good conductors, without undergoing 
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 elements are too numerous for us to seize. The 
true electrical condition 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 certain, or even probable conclusions are wanting, and we 
should, therefore, only embarrass our argument by any attempt 
to discuss this meteorological element, 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, are always accompanied by elec¬ 
trical disturbances—are believed, 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 Apen¬ 
nines 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 general 
prostration of the forest, these tempests are laying waste even 
