"But as to the Tube, if I cross under the sea, I would want to be as well informed on the road as I was three years ago. Now in the meantime, you have dropped interest in the long tunnel while I have become more interested in textiles--with the result that I have forgotten all I ever did know--which compared to your grasp of the details, was little enough." * * * * * But his face showed none of the old-time animation on the subject. What a different man, I mused to myself, from that enthusiastic engineering student that I used to come upon dreaming over his blue-prints. He was considered "half-cracked" in those days when he would enthuse over his undersea railroad, but his animated face was lit with inspiration. Now the light was gone. "Well, Dutch, how about it? Aren't you going to make me that brief little sketch of the length plan and cross-section of the Tube? I remember your sketch of it in college, and it tends to confuse me with the real changes that were made necessary when the wind-propulsion method was adopted." "All right, old timer. You remember that the Tube was widened at the sides in order that we could make two circular tubes side by side--one going each way." "I had forgotten that they were circular." "That is because of the pressure. A circle presents the best resistance," and picking an odd envelope from his pocket, he made the following sketch and passed it to me. [Illustration:--CROSS-SECTION OF TUBE--] I nodded as I recognized the cross-section. "Now the plan of the thing is like this," he added, putting aside his pipe and pulling a sheet of paper from the corner of his desk. Rapidly, with all his old accuracy, he sketched the main plan and leaned over as he handed it to me. [Illustration:--PLAN OF UNDER-SEA TUBE--] "You see," he explained, picking up his pipe again, "both pumps work at one time--in fact, I should say all four, because this plan is duplicated on the English side. On both ends then, a train is gently pushed in by an electric locomotive. A car at a time goes through the gate so that there is a cushion of air between each car. The same thing happens at Liverpool. Now, when the due train comes out of the suction tube, it goes on out the gate, but the air behind it travels right on around and comes in behind the train that is leaving." "But how are you assured that it will not stall somewhere?" "It won't be likely to with pressure pumps going behind it and suction pumps pulling from in front. We can always put extra power on if necessary. Thus far the road has worked perfectly." "How much power do you need to send it through, under normal conditions?"