Fog

a visible, watery vapor hanging near the surface of the earth. The word is Danish, meaning spray. There is no appreciable differnce between a fog and a mist. Fog is caused by the condensation of moisture in the air into innumerable globules. A current of cold air, passing over warm water from which moisture is rising by evaporation, produces a fog. A current of moist, warm air from the sea, passing over cold land, produces the same result. If this condensation takes place near the surface of the earth we call the product a fog; if at some height, a cloud. Huxley states that a fog is a cloud resting on the earth; a cloud is a fog floating high in the air. As the atmosphere warms, and its capacity for absorbing moisture increases, fogs are disolved and become invisible.

Cold currents from the Arctic Ocean, meeting the warm waters of the Gulf Stream southeast of Newfoundland, produce a region of perpetual fog and mist. To avoid collisions ships passing through this region keep their fog-horns going incessantly. A fog-horn used on shipboard is a huge cast iron affair, perhaps twenty feet in length. The dismal sound is caused by a blast of steam. At certain seasons of the year fogs are to be expected certainly in all North Atlantic ports, including those of the Great Lakes. They are so dense even at midday that a ship's pilot cannot see his way a boat's length in advance. Lighthouses do something to guide ships through the fog. They are also provided with fog signals that prove of assistance.

Great Britain and the coasts of Denmark are noted for heavy fogs, caused by the condensation of the moisture brought by the vapor-laden winds that accompany the warm Atlantic currents. The London fog is proverbially dense. When it falls on the city, street lamps are invisible at a distance of a few feet. Travel is positively dangerous. One may become lost in trying to go half a block. Business is suspended. Cabs stop running. Everyone makes for a place of shelter and waits until the fog lifts.

As we approached London the trees and houses became less and less visible on account of fog, and the nearer we came the denser it grew. It soon became impossible to see an object more than two or three arms length ahead of us. Detonators were placed on the tracks. The train would go until stopped by one of them, and wait a long time for a signal to start again. Then we would go on again at a snail's pace. So we continued until we reached Charing Cross Station.

I had always supposed that a London fog was much like an American fog except a little thicker, but such is not the case. You not only see it but you smell it, you taste it; the sounds you hear are muffled by it; like an evil spirit it follows you everywhere, even to your bedroom; and there is clouds your vision. In its appeal to the senses the London fog is like manual training--it is highly educative; it makes a deep impression upon you. Londoners have standardized fogs and numbered them as we used to number the degrees of hardness of rocks in the mineralogy class. The fog I saw was density No. 4 in a scale of five. I have no curiosity as to what No. 5 would be like. I saw enough London fog in three days to last a lifetime.--Charles A. Bennett.