Written without vowels, stops, capitals, or spaces, this gave a very serviceable cryptograph, but there was an added safeguard. After completing the first line the writer moved a shift-key and brought another set of symbols into play--or, rather, the same symbols under a different arrangement. The process was repeated for the third line, and then the fourth line returned to the system of the first. Thus three codes were really in operation, and the danger of the key being found by the frequent recurrence of certain symbols (the most fruitful cause of detection) was almost overcome. Six identical machines were in existence. One has been accounted for; Sir John Hampden had another; and a third was in the possession of Robert Estair, the venerable titular head of the combined Imperial party. A sociable young publican, who had a very snug house in the neighbourhood of Westminster Abbey, could have put his hand upon the fourth; the fifth was in the office of a super-phosphate company carrying on an unostentatious business down a quiet little lane about ten or a dozen miles out of London; and the sixth had fallen to the lot of a busy journalist, who seemed to have the happy knack of getting political articles and paragraphs accepted without demur by all the leading newspapers by the simple expedient of scribbling "Urgent" and some one else's initials across the envelopes he sent them in. Communications of the highest importance never reached the stage of ink and paper, but the six machines were in frequent use. In _bona fide_ communications the customary phraseology with which letters begin and end was not used, it is perhaps unnecessary to say. So obvious a clue as the short line "kbeljsl" at the head of a letter addressed to Estair would be as fatal to the secrecy of any code as the cartouched "Cleopatra" and "Ptolemy" were to the mystery of Egyptian hieroglyphics. That Salt wrote it may be taken as an indication that he had another end in view; and it is sometimes a mistake to overrate the intelligence of your opponents. When the letter was finished he put it away in his pocket-book, arranged the fastenings of both safe and desk so that he could tell if they had been disturbed, and then went home.