"Then, if they have a base anywhere along the coast we ought to be there before tomorrow at this time?" ventured Alfred. "That is exactly what I mean," answered the captain. CHAPTER VI GROPING THROUGH THE ENGLISH CHANNEL There was a steady pulsation of the engines during the entire afternoon without cessation until five o'clock, when the submarine submerged and continued under water for an hour. The three captives had now learned a great many of the manoeuvers incident to the diving operations, the signals accompanying each action, and studied with the greatest diligence and care the direction indicator and inclinometer. "I have been noticing the indicator for the last hour," said Ralph, "and it didn't change once. Are we going due north?" "The indicator that you see is not for the purpose of showing the points of the compass, but to tell whether or not there is a turning movement in the ship. If, for instance, the rudder should be turned to starboard or to port, the dial would swing in such a position as to show how much of a turn has been made, and no more," responded the captain. "Suppose then, that after making a quarter turn, the ship should again go ahead on a straight line, what would happen to the dial?" asked Alfred. "In that case the dial would again indicate that by coming back to its original position,--or, in other words, the dial would show that the ship had then assumed a new direction of sailing, and if it again changed to the right or to the left the indicator would reveal this to the observer," remarked the captain. "I wish we had a compass," said Ralph. "Unfortunately, they have taken our watches and pocket compasses," said the captain. "We may contrive, later on, to get a glimpse of the steering compass." "Do you know where it is?" eagerly inquired Alfred. "The navigating officer's instrument is in the conning tower, but it is usual, too, to have a similar instrument below, and I am sure it is located to the left of the cook's galley. It would not be safe, however, for either of us to be spying around in that quarter," responded the captain. That night they were again locked in their narrow apartment. As they had been provided with a good meal it was not such an unpleasant experience, and they were also comforted by the feeling that the submarine was now engaged in a no more perilous duty than trying to reach some port. That night was followed by a trying day of waiting. Singularly, they had not been permitted to ascend the hatchway stairs since the first day of their capture. "A glance at the sun would be enough to tell us the direction," remarked the captain after they left the table at the lunch hour. "I suppose they are keeping us down here for that purpose," suggested Alfred. "I have thought," replied the captain, "that the very fact of keeping us in ignorance of the direction they are going is the best indication that we are making for a concealed base."