A. 1st—The evaporation from the earth’s surface.
2ndly—The chemical changes perpetually going on: and
3rdly—Currents of air of unequal temperature, excite electricity by friction, as they pass by each other.
Q. How high are the lightning-clouds from the earth?
A. Electrical clouds are the lowest of all clouds; they are rarely more than 700 yards above the ground; and sometimes, they actually touch the earth with one of their edges.
Q. How high are the clouds generally?
A. In a fine day, the clouds are often 4 or 5 miles above our head; but the average height of the clouds is from 1-1/2 to 2 miles.
Q. Why is lightning sometimes forked?
A. When the lightning-cloud is a long way off, the resistance of the air is so great, that the electrical current is diverted into a zig-zag course.