Thunder-storms are more frequent in summer than in winter, and more so in the afternoon than in the morning.
By what are thunder-storms usually attended?
They are usually attended by some change in the direction of the wind.
Where do thunder-storms generally prevail?
They generally prevail in the lower regions of the air, near the earth.
What is the rapidity of lightning?
The rapidity of lightning is probably not less than 250,000 miles in a second, and the flash does not exceed the millionth part of a second in duration.
Magnetism.
Of what does magnetism treat?
Magnetism treats of the property of magnets.