Inside there is nothing much but machinery of the gasolene type, and the machine guns. The tank is closed except for small openings out of which the guns project, and slots through which the men inside look out to guide themselves or direct their fire. Such, in brief, is a British tank, one of the most powerful and effective weapons yet loosed against the Germans. They are useful in tearing down the barbed-wire entanglements on the Boche side of No Man's Land, and they can clear the way up to and past the trenches, which they can straddle and wriggle across like some giant worm. "And to think that Tom Swift didn't enthuse over these!" murmured Ned. "I wonder what's the matter with him!" Chapter IV Queer Doings There was a subdued air of activity about the Swift plant. Subdued, owing to the fact that it was mostly confined to one building--the new, large one, about which stretched a high and strong fence, made with tongue-and-groove boards so that no prying eyes might find a crack, even, through which to peer. In and out of the other buildings the workmen went as they pleased, though there were not many of them, for Tom and his father were devoting most of their time and energies to what was taking place in the big, new structure. But here there was an entirely different procedure. Workmen went in and out, to be sure, but each time they emerged they were scrutinized carefully, and when they went in they had to exhibit their passes to a man on guard at the single entrance; and the passes were not scrutinized perfunctorily, either. Near the building, about which there seemed to be an air of mystery, one day, a week after the events narrated in the opening chapters, strolled the giant Koku. Not far away, raking up a pile of refuse, was Eradicate Sampson, the aged colored man of all work. Eradicate approached nearer and nearer the entrance to the building, pursuing his task of gathering up leaves, dirt and sticks with the teeth of his rake. Then Koku, who had been lounging on a bench in the shade of a tree, Called: "No more, Eradicate!" "No mo' whut?" asked the negro quickly. "I didn't axt yo' fo' nuffin yit!" "No more come here!" said the giant, pointing to the building and speaking English with an evident effort. "Master say no one come too close." "Huh! He didn't go fo' t' mean me!" exclaimed Eradicate. "I kin go anywheres; I kin!" "Not here!" and Koku interposed his giant frame between the old man and the first step leading into the secret building. "You no come in here." "Who say so?" "Me--I say so! I on guard. I what you call special policeman--detectiff--no let enemies in!" "Huh! You's a hot deteckertiff, yo' is!" snorted Eradicate. "Anyhow, dem orders don't mean me! I kin go anywhere, I kin!" "Not here!" said Koku firmly. "Master Tom say let nobody come near but workmen who have got writing-paper. You no got!"