Von Breechow passed the English officials at Rotterdam and at Tilbury. He soon fell under suspicion, however, and his passport was taken away. When the British learned that the real Rowland was at home in New Jersey, and in possession of his own passport, they sent for it, and compared the two. Breechow's revealed a false watermark, stamped on in clear grease, which made the paper translucent, but which was soluble in benzine. The stamp, ordinarily used to countersign both the photograph and the paper in a certain way, had been applied in a different position. With those exceptions, and the suspicious Teutonic twist to a "d" in the word "dark," the counterfeit was regular. The Rosenthal case was the first to bring to light the false passport activities in Berlin. Rosenthal, posing as an agent for gas mantles, traveled in England successfully as a spy under an emergency passport issued by the American Embassy in Berlin. Captain Prieger, the chief of a section in the intelligence department of the General Staff, asked Rosenthal to make a second trip. The spy demurred, doubting whether his passport might be accepted a second time. The Captain turned to a safe, extracted a handful of false American passports, and said: "I can fit you out with a passport in any name you wish." Rosenthal decided to employ his own. He was arrested and imprisoned in England. As the State Department increased its vigilance the evil began to expire. It was further stifled by concerted multiplication by the Allies of the examinations which the stranger had to undergo. But during its course it made personal communication between Berlin and lower Broadway almost casual. CHAPTER VIII INCENDIARISM Increased munitions production--The opening explosions--Orders from Berlin--Von Papen and Seattle--July, 1915--The Van Koolbergen affair--The autumn of 1915--The Pinole explosion. A bomb is an easy object to manufacture. Take a section of lead pipe from six to ten inches long, and solder into it a partition of thin metal, which divides the tube into two compartments. Place a high explosive in one compartment and seal it carefully (the entire operation requires a gentle touch) and in the other end pour a strong acid; cap it, and seal it. If you have chosen the proper metal for the partition, and acid of a strength to eat slowly through it to the explosive, you have produced a bomb of a type which German destroying agents were fond of using in America from the earliest days of their operation.