“Since you insist,” replied the Professor, “under pressure and assuming that I was furnished with the highest facilities, my invention is so well advanced and the practical details are so clearly outlined in my mind that I could produce an air-ship of the smaller type in from two to three weeks.” Kearns sprang forward with a joyous exclamation. “Professor,” he cried, “you shall build that machine. You shall have the highest facilities--the very highest facilities--I promise you, but it must be ready within a month at latest!” “Why--why--what do you mean?” exclaimed the Professor with mingled joy and astonishment. “Never mind!” retorted Kearns. “Suffice it that the King will refuse me nothing I need to assist me in my investigations. And now, I have one other question to ask. Does your machine leak at times?” “Leak!” repeated the Professor, bewildered. “Well, I mean,” explained Kearns, “does it ever exude, drop, drip, let fall--or whatever you like to call it--a liquid of any kind?” “Oh, I see what you mean!” exclaimed the Professor, his face lighting up. “Why, yes. To the right side and below the level of the main turret, there is a secondary storage box. The decomposition of the chemicals in this box produces the power to----” “Now, Professor,” interrupted Kearns, “please don’t wax technical. Remember, as I told you, a stone wall is a light and airy thing compared to my density as to matters mechanical.” “Very well, O marvel of density!” retorted the Professor with light sarcasm; “I will endeavor to explain so that even your benighted brain may grasp and understand. What would you do if you had a grate full of coals and the coals had burned out and you wanted more fire?” “I suppose,” replied Kearns mischievously, “that I should ring the bell and tell the servant to make up the fire.” “And how would the servant do it?” “I suppose by putting on more coals,” answered Kearns cautiously. “Indeed!” sniffed the Professor contemptuously, “does it not occur to you--O man of self-vaunted thickness!--that the servant might indulge in some operation prior to putting on those fresh coals?” “Huh!” exclaimed Kearns, with a puzzled expression; “I suppose you mean that there would first be a raking out of the ashes.” “Good!” exclaimed the Professor; “you are beginning to betray an intelligence which is almost human. Now, so it is in the case of the air-ship. In that secondary storage box to which I have referred are certain chemicals which furnish power. When a portion of these chemicals have exhausted their activity, a residuum gradually forms, corresponding to the ashes in your grate, only it is in liquid form instead of solid. This residuum is allowed to escape through a valve and is thus carried away and, of course, the storage box is fed from time to time, as may be required, with fresh energy-producing chemicals.”