“There,” said the inventor, pointing to this band and the two holes, “is the vital part of my invention. You see those holes?—yes—well, they are the muzzles of my vanishing guns.”
The group about the inventor nodded; but as yet they had only a very vague idea of the details of this strange invention.
“That slender shaft of tubing rising from the conning tower,” said Mr. Peregrine, who in his enthusiasm had lost his jerky manner of talking, “is nothing more nor less than a periscope; you know what that is, I presume.”
“A device which will show whatever is occurring outside, while the operator of the machine to which it is attached remains hidden,” said Jack.
“Correct. But this is an improved periscope. It gives the operator of the ‘gun carriage’ a wide view of the sky in every direction. But to explain my invention more fully I must invite you inside.”
So saying, the inventor opened a door in the side of the steel structure, which they had not previously noticed. Taking Jack by the arm, he gave him a half shove into the interior of the steel cigar.
As the space within was small, Mr. Peregrine explained that he would have to show the points of his invention to one of them at a time. When Jack was inside the inventor closed the door and, turning a switch, caused a flood of light to illuminate the interior of the wheeled cylinder. Jack found that they were standing within the conning tower. Through the slits he could see out into the shed, but his attention was speedily distracted by Mr. Peregrine.
The inventor indicated a seat, and invited Jack to occupy it. The boy was informed that he was seated in the operator’s position. In front of him was a sort of desk with a white top. This was divided into squares. The inventor explained that the white surface represented the expanse of sky commanded by the periscope.
“The instant an aëroplane is seen to enter one of those squares, each of which, as you see, is numbered,” he explained, “I press one of these buttons which are correspondingly marked.”
He reached up to a sort of switchboard above the periscope desk, and pressed one of the numbered buttons on it. A whirring sound followed.
“That noise is caused by the cylindrical band which you observed on the fore part of the machine,” said Mr. Peregrine; “two guns, controlled by electricity, are set in that band. By pressing this button one of them is automatically aimed at the square of sky which the periscope shows is occupied by a supposedly hostile aëroplane.”