Directly I saw the half-faded parchments I recognised that the cipher which those early Jesuit writers had used was a very simple one. This, I may explain to the uninitiated, is not so difficult a matter to observe as they might perhaps think. Some very simple considerations guided me to this conclusion. For instance, unlike the cipher in use by the founder of St Bruno, there were practically no figures in the manuscripts, and by that I gathered the cipher was complete in the alphabet in use, and did not refer to any book, like the institutes of St Bruno. The one thing that does puzzle and sometimes confound experts is to adopt a book, as Bruno Delganni had done, and then to put in the record simply figures that related to letters in this volume. That, however, is not always quite safe. The expert looks in the manuscript for the letter that appears most often, and he decides, perhaps, that that is "e," the second "i," and so on according to the letters that are most frequently used in the language in which he believes the document to be written, and by this simple means he can often construct the entire code alphabet. On some such method I too proceeded with the inspection of the manuscripts in question, and found that the letter that appeared the most often therein was a certain letter that was not often used in any language. I, therefore, turned the alphabet round thus: ZYXWVUTSRQP abcdefghijk It was, unfortunately, useless. Later I tried the alphabet in Portuguese form, and I saw with joy that we need not trouble at all about the rolls of explanation which Camille Velasquon had brought, and which were laid on the table beside us, but that I had really hit on the right solution--at the very start--without a glance at those cipher keys that had come to us from Mexico. The Jesuits had first merely reversed the order of the letters, and instead of writing "A" when they should have done, they had put "Z" in its place, and so on right through the alphabet, making the language of the base Portuguese, and not Spanish or English, as we had all expected at first. The cunning old sons of St Ignatius of Loyola had, however, not left their secret quite so plain as that. They had also added to it, to disguise it the better, a trick which most of us learn when we are boys at school. This consisted in adding to every syllable another rhyming with it but beginning with "p." Thus to put "Venha Ca" (come here) they wrote "Venpenhapa Capa," or if in English, "comepum herepere," and this, when written to any extent, is really quite bewildering to any student of manuscripts unaccustomed to it.