. Fig. I.—HORIZONTAI, 0SCII,I,ATING FRAME. This enables an observer to study the aerial field above the earth, and to determine the direction of the source emitting the electric waves. and a minimum on the longitudinal frame, indicating that the course is at right angles to, and of course approaching, the cable. The intensity of reception increases as the cable is approached. From time to time the observer listens in on the spiral of ten turns of the transverse frame, but hears nothing until the ship is sufficiently near. At the moment of making contact on this coil the vessel is turned throug
. Fig. I.—HORIZONTAI, 0SCII,I,ATING FRAME. This enables an observer to study the aerial field above the earth, and to determine the direction of the source emitting the electric waves. and a minimum on the longitudinal frame, indicating that the course is at right angles to, and of course approaching, the cable. The intensity of reception increases as the cable is approached. From time to time the observer listens in on the spiral of ten turns of the transverse frame, but hears nothing until the ship is sufficiently near. At the moment of making contact on this coil the vessel is turned through 90'", for this signal indicates that it is about 300 metres from the cable. The ship is then set so that there is a good signal on the small longitudinal frame and zero signal on the transverse. In this case a course is being held rigorously parallel to the cable and at a distance less than 300 metres from it. Even if there is a strong cross-current, it is possible to maintain on the longi- tudinal frame a signal of constant intensity. Vessels keeping to the right— having always the cable on their left—know its direction and consequently their own course. At any time they can find out whether they are approaching or receding from the cable and know where they are relatively to it. Thus the dangers of fouling, of grounding, or of striking a rock disappear completely, and make navigation practicable. It was found possible, for example, to steer a 400-ton gunboat. La Belliquense, along a cable placed at the mouth of the entrance to the Brest harbour under conditions of perfect safety. La Gloire, a 10,000-ton cruiser, was also piloted along the same cable. The current flowing through the submerged cable is only 2'5 amperes. Yet it can be detected, even without adjustment to resonance, as far away as two to three kilometres, so that the total listening zone is four to six kilometres. It may be added that these experiments, witnessed by the Minister of Marine, were f
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