Here is a little picture of what is known as a floating mine. It consists of a hollow, pear-shaped case, containing an electric battery and a large amount of gun-cotton, or some other high explosive. This mine is thrown into the sea, and by means of an iron weight is made to float three or four feet below the surface. If the mine is struck hard, it will cant over sixty-five or seventy degrees. Then the mercury in a little cup would overflow, and by so doing would complete an electric circuit and explode the gun-cotton. So terrible is the explosive force of gun-cotton, that it will tear asunder the biggest ship, and either cripple it or send it to the bottom. Never before has any nation strewn the open seas with such floating mines, and their use in this way is against all the laws of war which are observed by civilized nations. [Illustration: Sweeping up mines in the North Sea.] The Germans soon discovered that large mine-layers ran a great risk of being sunk by the guns of our warships, so they employed fishing-boats and other small craft to lay these deadly engines in the sea. Many of these ships flew the flag of a neutral Power, and thus pretended that they were engaged on lawful and peaceful business. The North Sea became a death-trap, and our Admiralty had to meet the danger by employing a large number of trawlers to sweep up the mines. The work is done in the following way. Two trawlers sailing parallel with each other drag through the sea a steel hawser which is attached to each of them. The hawser drags the mines along, and they are then picked up. You can readily understand how dangerous this work is. The trawlers themselves may strike a mine, and be blown up; or two mines drawn along by the hawser may collide when they are near to the trawlers, in which case the same result follows. Many gallant smacksmen have lost their lives in trying to free the sea from this terrible peril. We ought to think of them as heroes of the best and highest type. Always remember that it is more glorious to save life than to destroy it.