206 Proceedings of the Ohio Academy of Science 
the lightning discharge is exceedingly variable, ranging from 
0.0002 second for a single flash to, in rare cases, even a full 
second or more for a multiple flash consisting of a primary and 
a series of subsequent flashes. The lightning discharge is 
direct, not alternating, as shown by the fact that the lightning 
may operate telegraph instruments, may reverse the polarity of 
dynamos, both of which requires a direct current. 
The length of the lightning streak also varies greatly. 
When the discharge is from cloud to earth the length is seldom 
more than 2 or 3 kilometers, but when from cloud to cloud 
may be 10 to 20 kilometers (6 to 12 miles). The path of the 
lightning discharge may extend from the cloud to earth, from 
one portion to another of the same cloud, or from one cloud to 
another cloud. Obviously the second case is of the most fre- 
quent occurrence, that is, from the upper to the lower portion 
of the same cloud; from cloud to earth is next in point of fre- 
quency, and from cloud to cloud, relatively rare. Sometimes 
the discharge from cloud to earth may include in its strange 
and tortuous path objects that have not sufficient conductivity 
to carry it and as a result of the sudden and excessive heating 
many very freakish things may be done, such as shingles blown 
off, chimneys shattered, trees stripped of their bark or splin- 
tered, wires fused, even holes melted through metal, ete. Then 
there are certain chemical reactions resulting from these elec- 
trical discharges that play an important part in the economy of 
nature. For instance the health-giving ozone of the atmosphere 
is greatly increased by the passage of a thunderstorm, and even 
the fertility of the soil may be increased by the production of 
considerable quantities of ammonia and soluble salts. 
Perhaps, a word or two should be said regarding the danger 
to life incident to the passage of a thunderstorm. That there 
is danger, even great danger at times, is abundantly shown 
from the tragic statistics of deaths each year from this cause. 
While it is not possible, perhaps, to remove this danger, it is 
possible to reduce it, chiefly by avoiding the points of greatest 
danger. In general, it is safer inside than outside of a house, 
especially if the house has a well-grounded rod or metal roof; 
it is also safer in the valley than on a hill or elevated portion 
of land, this because the chance for a cloud-to-earth discharge 
varies inversely as the distance between them; it is also very 
unsafe to take refuge under a tree and the taller the tree the - 
