Dr. Armitage knew, from the repeated failures of his colleagues, that the riddle was a deep and complex one, and that no simple mode of solution could merit even a trial. All through late August he fortified himself with the massed lore of cryptography, drawing upon the fullest resources of his own library, and wading night after night amidst the arcana of Trithemius' Poligraphia, Giambattista Porta's De Furtivis Literarum Notis, De Vigenere's Traité des Chiffres, Falconer's Cryptomenysis Patefacta, Davys' and Thicknesse's Eighteenth Century treatises, and such fairly modern authorities as Blair, von Marten, and Klüber's Kryptographik. He interspersed his study of the books with attacks on the manuscript itself, and in time became convinced that he had to deal with one of those subtlest and most ingenious of cryptograms, in which many separate lists of corresponding letters are arranged like the multiplication table, and the message built up with arbitrary key-words known only to the initiated. The older authorities seemed rather more helpful than the newer ones, and Armitage concluded that the code of the manuscript was one of great antiquity, no doubt handed down through a long line of mystical experimenters. Several times he seemed near daylight, only to be set back by some unforeseen obstacle. Then, as September approached, the clouds began to clear. Certain letters, as used in certain parts of the manuscript, emerged definitely and unmistakably; and it became obvious that the text was indeed in English.