In a few minutes Captain Doris returned and the vessel began to move rapidly through the water. I was much interested in the view of marine life which was revealed through the transparent sides, and especially in the level bottom of the lake, which, as Oqua had remarked, really looked something like a broad, smooth, cultivated field. But soon we turned toward the south and began to move slowly along the side of a brilliantly lighted boulevard on which all kinds of vehicles were passing and repassing. I was so much astonished at this unexpected scene, so realistic and seemingly uncanny, that I was utterly at a loss for words to express my feelings. Oqua seeing my embarrassment came to my relief by saying: "This is the tunnel across the lower portion of the lake and constitutes a part of the boulevard you noticed along the shores." "How is this?" I asked. "It is certainly not a tunnel excavated under the lake. If anything, we are a little below the roadway and well above the bottom of the lake with the water all around us." "We do not," said Oqua, "excavate tunnels as we did in ancient times. They are constructed in our machine shops. This is a metallic tube with supports which rest on the bottom, and has many advantages over the old fashioned, dark and dismal excavations. The material used is a compound somewhat like common glass but as strong as steel. With our submarine fleets it is not difficult to put the sections in place and when completed the water is pumped out of the cavity and the roadway is ready for use. Even across small streams, where the banks are not too high, they are frequently preferred to bridges as more safe and durable, but for long distances and in very deep water they are indispensable, and in the case of deep water tunnels, they are frequently made to span submarine gorges." "How fortunate," I exclaimed, "that this submarine excursion was on the program! I now see a most wonderful exhibition of the power of mind to overcome material difficulties, that it would have been hard for me to realize if I had received the information in some other manner." "All things," responded Oqua, "are possible to the human mind in its ultimate state of development--But we are now heading for the landing at the Transportation Headquarters and we will spend the night on the Silver King which takes us down to the ruins of Kroy in the morning." "And," I asked, "what is to hinder you from telling me something about these ruins now, and what they have to do with Norrena's economic lessons?" "They are," said Oqua, "only the relics of the great money center which held the people in bondage during the Transition Period. When Kroy was deserted by the money kings, the people determined to preserve it, subject only to the ravages of time, as a warning and a lesson to future generations."