Thus matters stood when half the industrial army of Holl, taken from their regular tasks, were set to the making of the giant gun and its equally giant projectiles. Monstrous though they were to be, however, they were no less prodigious than Powart. Could Fort, wondered Mona, possibly equal him? And so the weeks passed into months, and finally the great day came. XVI THE BLAST "I am glad to see so many moving-picture men," said Mona thoughtfully. "If it were not for photographs, I doubt if coming generations would believe this." And she turned her glasses again upon the scene. From the cockpit of Fort's newest ornithopter, about three hundred yards from the ground and less than that distance from the spot, she could watch operations with exceptional ease. Fort agreed with her comment. "Yes; to merely state that the mouth of that cannon is a hundred feet in diameter, and that it is set a mile and a half into the ground, at an angle of thirty degrees--it's too much of a strain on the imagination. However, I understand they've taken flash-light pictures from the interior, such as will make it easier to believe." A huge compound crane was slowly swinging the first projectile into place over the muzzle of that colossal gun. Mona eyed the immense shell with curiosity. "As I understand it," she said, "the projectile is really a number of shells, telescoping, one within another. I've forgotten how many there are." "Fifty. The idea, of course, is that the original charge of powder within the cannon will send the projectile at something like two miles a second. Upon reaching a certain point in space another charge will be automatically fired in the base of the outermost shell. Thus it will act as another cannon, from which the remaining shells will be shot. And so on, until the forty-ninth shell has been blown to the rear. The remaining one will, by that time, have traveled far enough to get out of our gravitation into Alma's." "What is the size of the fiftieth shell?" "Only two feet in diameter; [Footnote: All dimensions are necessarily a matter of judgment; but they represent the opinion of an architect, whose sense of proportion is presumably better than average.] but of such length that it will hold five tons of explosive. It is expected to demolish a square mile of their roof." The great projectile was carefully lowered until its tip was flush with the volcano-like mouth of the cannon. The proceeding took a long time; and it was well toward the end of the work that Powart's handsome yacht swept into the space provided for it in the circle of spectators. By prearrangement this space was next to that occupied by Mona and Fort. As soon as the yacht had come to a stop its thrumming wings keeping it as steadily suspended in mid air as any of the lighter craft roundabout, Powart himself stepped out upon the tiny bridge. It was the signal for a great outburst of applause, in which Fort joined as heartily as any one.