"These bilge-keels serve a threefold purpose; they enable the ship to rest steadily and firmly on the ground, as you see, which, from her peculiar form, she could not otherwise do; they also form the sheaths, so to speak, of four anchors to fasten her securely to the ground either above or beneath the water--a most necessary precaution, believe me; and they also add considerably to the cubical contents of the water- chambers, with which they communicate, which will help to sink the ship to the bottom. Lastly, there is the propeller, the only peculiarities of which are its great diameter--fifty feet--its enormous surface area, and the fact that it is attached to the hull in such a way as to admit of its being turned freely in any direction, thus dispensing with all necessity for a rudder." "Why have you left the hull unpainted, professor? I suppose you had some good reason for so doing?" remarked the colonel, chiming into the conversation. "I had no less than _three_ good reasons for leaving the hull of the ship unpainted," answered the professor. "In the first place, aethereum is quite insensible to the attacks of air and water--it never oxidises, and paint was therefore unnecessary for its preservation. In the next place, the quantity of paint necessary to cover that enormous surface would weigh something considerable; and, as I have throughout the work taken the utmost pains to keep down all the weight to the lowest ounce consistent with absolute safety, I rejected it on that account. And lastly, I take it that we are anxious to avoid all unnecessary observation; and I believe this cannot be better accomplished than by preserving the brilliant metallic lustre of the hull, which, especially when we are floating in mid-air, will reflect the tints of the surrounding atmosphere, and so make it almost impossible to distinguish us." "Except when the sun's rays fall directly upon us, eh, professor?" remarked Mildmay. "In that case," returned the professor, "observers will see a dazzling flash of light in which all shape will be indistinguishable." "And we shall thus be mistaken for a meteorite," exclaimed the baronet somewhat sarcastically. "Excellent! admirable! I really must congratulate you, professor, upon the wonderful foresight with which you seem to have provided for every possible and impossible emergency. Now, what is the next marvel?"