A YOUNG American, John Hayes Hammond, Jr., has recently been doing things down on the east coast of Massachusetts that would have been his death-warrant in the days of the Salem witches. From a hilltop overlooking Gloucester harbor, he was directing daily, by means of invisible waves, the manoeuvering of a sinister-looking craft of high speed which may soon develop into a very formidable instrument for coast defense. Mark you, no one is on board; the boat performs all of its amazing evolutions guided by a curious combination of vibrations having their source in an apparatus at Mr. Hammond's hand, far up on the bluff! This sounds uncanny, does n't it? But it is one of the developments of a new branch of knowledge, the science of telautomatics, or the management from afar of mechanical operations. Telautomatics is going to do a large variety of astonishing things for us before long, and all of us should know something about this new wizardry.

Wireless telegraphy has become an old story now, and you know that its way of working is for the man at the sending station to set up waves in the atmosphere by means of an electrical discharge. These waves in the atmosphere, like the circling ripples we see spreading from a stone dropped in a pond, reach out invisibly through the air or ether until they awaken to action a delicate and very sensitive receiver. VOL. XLI.-20.

This receiver is part of a local electric circuit, but the battery current cannot flow until the arriving waves cause the receiver to complete the path for the electricity. In making and breaking this current flow, the receiver actually repeats the signals despatched from a long way off, and in this fashion dots and dashes representing letters are produced.

Of course this is quite different from making a boat turn in any direction, or to halt it or start it at will; but you will see in a moment that the difference is largely in the way the ether waves

mands action upon the part of mechanisms capable of exerting a good deal of power. Let us call the receiver a child, or messenger, and the local battery, or "relay," the man that is strong enough to do what is desired. Keep this simple comparison in mind, and you will find it easy to understand all that is needful of Mr. Hammond's work.

Over in Europe, the French and the Germans have been busy for some time experimenting with torpedoes that could be guided by Hertzian waves, that is, vibrations produced in the ether by an electrical discharge, the kind of waves used in wireless telegraphy. When one, two, three. or four of these waves were despatched in proper order, the sensitive receiver would allow the vigorous "relay" to act so as to call into play any one of as many different mechanical movements. One would start the torpedo, two would stop it. three would turn it to the right, and four would swing its nose to the left, and, possibly, a fifth would explode the charge of guncotton. The wireless experts of these two countries have had a promising measure of success. The idea, you know, is to make the deadly torpedo more certain of hitting its intended mark.

Of course England could not remain idle when her fretful neighbors were busy at this kind of thing, so her wireless "sharps" got into the game. The British naval men went their continental

A FRENCH CRUISER PUTTING A WIRELESS TORPEDO THROUGH ITS PACES.

rivals one better-they took an old submarine, capable of carrying a number of torpedoes, and fitted her with a system of wireless control of a

JOHN HAYS HAMMOND, JR.'S, HOUSE-BOAT, DIRECTED BY WIRELESS, WHICH PRECEDED HIS WIRELESS TORPEDO-BOAT.

when Hertzian waves are employed, and they used under-water sound waves, which Mr. John Gardner was the first to so utilize, for their crewless submarine.

Sound, you know, travels four times as far below water as it will through the air, and, unlike the atmosphere, the power of water in forwarding these waves is not affected by the weather as are Hertzian impulses. Here was one advantage, but we shall see that there were others. The Gardner receiver was so made that its ear was deaf to all but a chosen group of sounds. It was a kind of sound-lock that could not be opened or worked except by a certain key-note or chord, and the desired operations could be set in motion then only by the repeating of this "open sesame" in a given way.

Before we come to Mr. Hammond's invention, which is the latest, let us go back a short span. A few years ago, Professor Ernst Ruehmer, of Germany, who died recently, produced a wireless telephone with which he experimented in the outskirts of Berlin. Instead of a wire he used the beam of a search-light for his conductor, and at the receiving end he had a little cell of selenium. Selenium is a curious metal inasmuch as its capacity to let electricity flow through it varies greatly when exposed to light of different intensities. The brighter the light the less resistance it offers to the passage of the current.