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SUPPOSE we have at our command torpedoes that obey the orders of a single master; torpedoes that heed faithfully the wish of an operator expressed through a simple directing apparatus; torpedoes that can be projected six or eight miles through the water, being constantly under the control of the man and his machine on shore; in a word, torpedoes which carry out the intention of one man to destroy an oncoming vessel of the enemy. This torpedo would simply be the projection mechanically, of this man's will to destroy that vessel.

Theoretically, we have the materials at hand to render this achievement possible. In fact, the "light-directed torpedo," as it is called, is virtually on the threshold of reality, but it has not yet crossed the threshold. This delay is caused by the present unreliability of a chemical substance, selenium, and it is upon selenium that the eventual success of the light-directed torpedo depends. In an article on the Hammond electric dog, appearing elsewhere in this issue, will be found an explanation of the way in which selenium does the work.

A boat has been directed wirelessly from shore—most all of us have read of that—and a boat can be directed by wire-