Searchlights are ordinarily electric arc lights of great candle-power, arranged with a parabolic reflector so that the rays are sent almost wholly in one direct line, forming a path of light which may be projected for miles.
What Started the Habit of Touching Glasses Before Drinking?
Just as athletes shake hands before the beginning of a contest today, the people who fought duels in the olden days used to pause before their fighting long enough to each drink a glass of wine furnished by their friends. In order to make sure that no attempt was made to forestall the results of the duel by poisoning the wine in either cup, they developed the habit of pouring part of the contents of each glass into the other, so that if either contestant was poisoned the other would be too.
This habit has continued up to the present time, although there is no thought given now to the danger of poison, and in the present day the ceremony of actually pouring the drink from one glass to another has been omitted, merely the motion, as if to touch the glasses, sufficing as an expression of friendliness and good will.
Touching glasses together in drinking, preparatory to a confidential talk, has come to be nicknamed “hob-nobbing” because of the equipment incidental to that action years ago. A “hob” was the flat part of the open hearth where water and spirits were warmed; and the small table, at which people sat when so engaged, was called a “nob.”
Why are Windows Broken by Explosions?
When the large cannons in the forts on our coast are discharged during target practice, there are usually a lot of windows broken in the nearby houses. In Jersey City, N. J., several freight cars and boats loaded with dynamite and ammunition full of high explosives furnished the power for an explosion which, in July, 1916, broke considerably over a hundred thousand dollars worth of windows in the lower part of New York City.
The force of an explosion, whatever its source, throws back the air in huge waves, very much like the waves of the ocean, and whatever they come in contact with must have a sort of a tug-of-war with them, the weaker side being crumpled up and pushed back by the other. Broad expanses of glass, unprotected and without any support, except at the extreme edges, present an easy mark for air waves, therefore, and the amount of damage done to windows by explosions is usually only limited by the power of the explosives which produce the force of air waves.
The earth beneath, and the roof and walls of a building above, all receive the effects of these air waves in exactly the same way as do windows, and the resulting disaster is in direct proportion to their resisting capacity as against the pressure caused by the explosion. Many striking examples of the power of explosives have been accidentally furnished of late, in the course of making munitions for the European war.