Sound moves about thirteen miles in a minute. So that if we hear a clap of thunder half a minute after the flash, we may calculate that the discharge of electricity is a half miles off.

In one second of time - in one beat of the pendulum of a clock - light travels over 192,000 miles. Were a cannon ball shot toward the sun, and it were to maintain fill speed, it would be twenty years in reaching it - and yet light travels through this space in seven or eight minutes.

The velocity of sound in sea water is 4,708 feet per second, at the mean temperature of 46.6° Fahrenheit.