The greatest height at which visible clouds ever exist does not exceed ten miles.

Air is about 815 times lighter than water.

The pressure of the atmosphere upon every square foot of the earth amounts to 2,160 pounds.

An ordinary-sized man, supposing his surface to be fourteen square feet, sustains the enormous atmospheric pressure of 30,240 pounds.

The barometer falls one-tenth of an inch for every seventy-eight feet elevation.

The violence of the expansion of water when freezing is sufficient to cleave a globe of copper of such thickness as to require a force of 27,000 pounds to produce the same effect.

During the conversion of ice into water 140 degrees of heat are absorbed.

Water when converted into steam increases in bulk 1,728 times.

Power of steam, steam as compared with water, occupies 1,728 times as much space. A cubic inch of water will make 1,728 cubic inches of steam at atmospheric pressure. Now, if this steam is compressed into half the space it occupies at atmospheric pressure, it will double that pressure, or 15 pounds above the atmosphere; it will then occupy only 8G4 cubic inches; if reduced again to half its volume, it will occupy 432 cubic inches and will have 30 pounds pressure. Reduced again to half this volume, the steam will occupy 216 cubic inches, and will have 60 pounds pressure to the square inch. We can go on reducing in this way until we find that a cubic inch of water turned into steam and compressed into a space of 3 cubic inches will have the somewhat enormous pressure of 3,S40 pounds to the square inch.

Were a cannon-ball shot towards the sun and were it to maintain full speed, it would be twenty years in reaching it; and yet light travels through this space (91,000,000 miles) in seven or eight minutes.

In one second of time, in one beat of the pendulum of a clock, light travels 192,000 miles.

Strange as it may appear, a ball of a ton weight and another of the same material of an ounce weight, falling from any height, will reach the ground at the same time.

The heat does not increase as we rise above the earth nearer the sun, but decreases rapidly until, beyond the regions of the atmosphere, in void, it is estimated that the cold is about 70 degrees below zero. The line of perpetual frost-at the equator is 15,000 feet altitude, 13,000 feet between the tropics and 9,000 to 4,000 feet between the latitudes of 40 degrees and 49 degrees.

At a depth of 45 feet under the ground the temperature of the earth is uniform throughout the year.

In summer time the season of ripening moves northward at the rate of 10 miles a day.

The human ear is so extremely sensitive that it can hear a sound that lasts only the twenty-four thousandth part of a second.

The ordinary pressure of the atmosphere on the surface of the earth is 2,160 pounds to each square foot, or 15 pounds to each square inch, equal to 30 perpendicular inches of mercury or 34 1/2 feet of water.

Sound travels at the rate of 1,142 feet per second, about 13 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 six and one-half miles away.

Lightning can be seen by reflection at a distance of two hundred miles.

The explosive force of closely confined gunpowder is six and a half tons to the square inch.