The present-day submarine suffers from two serious drawbacks: (1) inability to see under the water; (2) inefficient speed—the latter being much slower compared with the speed of fast surface boats. The chief chance of a submarine attacking an enemy with success is to come upon him unawares.
The periscopes and other optical tubes with which submarines are fitted, suffer also from many disabilities; and the fact that many collisions have occurred while using them, shows that they are not yet perfect. Obviously one showing not only what is forward of the submarine but what is on the surface of the water on every side is best. One of the drawbacks from which they suffer is the encrustation of salt on their reflecting surfaces; and small though the exposed surface of the periscope may be, there is always the chance of a vigilant enemy detecting it.
The Submarine in Peace.—It is pleasant to record that this invention, like many others of its kind, has not been devoted solely to war, but that peace also can claim its services. The recent remarkable trans-Atlantic voyages of the German submarine Deutschland to American ports is an illustration of their importance to commercial transportation under critical conditions. Since, too, the submarine can sink or dive down to moderate depths, it is obvious it can be used for purposes of underwater salvage, construction, and exploration.
As an aid in the construction of breakwaters, the blowing-up of submerged wrecks in comparatively speaking shallow waters, in searching for sunken treasures, and as an aid to marine explorations in suitable waters, the peace or working submarine is likely to be of untold value.
TORPEDO TUBE OF SUBMARINE—DEADLY TORPEDO SHOWN IN TUBE ON RIGHT OF PICTURE
ELECTRICITY AND MAGNETISM
What is Electricity?—Means of Exciting Electricity—Electrified and Non-Electrified Bodies—Conductors and Non-Conductors of Electricity—Electrical Machines—Positive and Negative Electricity—Velocity of Electricity—Principal Agents in Nature Exciting Electricity—Lightning—Three Forms of Lightning—Sheet and Heat Lightning—Duration of a Flash of Lightning—Places Dangerous in a Thunder Storm—How a Tree Influences Lightning—Lightning Conductors—Their Proper Principle of Construction—Franklin’s Experiment with a Kite—Identity of Lightning and Electricity—Utility of Lightning-Rods—What is Thunder?—What Occasions the Rolling of Thunder?—Aurora-Borealis—Extent of the Aurora—Height of the Aurora—Appearance—Aurora-Borealis Occurs in the Day-Time—What is Galvanism?—How Galvanic Electricity Was Discovered—Construction of a Galvanic Battery—Origin of the Term “Galvanism”—Poles of a Battery—Means by Which Galvanic-Electricity in Quantity Can Be Developed—Different Forms of Galvanic Batteries—Light and Heat Produced by Galvanism—Principles and Processes of Electro-Metallurgy—Magnetism—Natural Magnets—Where Found—Bodies Capable of Being Magnetized—Induction—Magnetic Needle—The Magnetic Compass—Discovery and First Use of the Compass—Electro-Magnetism—When and How Discovered—How Iron Bars Become Magnetic—Horse-Shoe Magnets—Excitation of Magnetism—Morse’s Magnetic Telegraph—Telegraph, Magnetic, Principles of—Intelligence, How Conveyed by—Electric Dynamo and Motors—Wireless Telegraphy—Wireless Telephone—X-Rays