ELECFRICAL INFLUENCE OF TREES. 153 
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 
and producing some change of electrical condition. Hypo- 
thetical 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 adeluge 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, conclusions are 
wanting, and we should, therefore, only embarrass our argument 
by any attempt to discuss this meteorological element, impor- 
tant 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 pro- 
duced by a specitic electrical action, and which, at least, appear 
to be always accompanied by electrical disturbances—are be- 
lieved, 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 
