But we have not as yet reached what is, after all, for our purposes the most instructive part of the work of the pontifices--I mean the archives or memoranda (_libri_ or _commentarii_) which they kept, and from which, indirectly, much of what I have had to say about the _ius divinum_ has been drawn. It is here that we see the policy of maintaining the _pax deorum_ carried to its highest point. These books contained a vast collection of formulae for every kind of process in which the deities were in any way concerned; here was the complete _pharmacopoeia_ of the _ius divinum_.[591] We must remember that the pontifex maximus and his assessors had to be ready at any moment with the correct formula for all religious acts, whether extraordinary, like the _devotio_ of Decius or the expiation of some startling "prodigium," or belonging to the ordinary course of city life, such as prayers in sacrificial ritual, _vota_ both public and private, charters (_leges_) of newly founded temples, and so on. The idea that the spoken formula (ultimately, as we saw, derived from an age of magic) was efficient only if no slip were made, seems to have gained in strength instead of diminishing, as we might have expected it to do with advancing civilisation; and the pontifices not only responded to its importunity, but actually stimulated it. _Vires acquirit eundo_ are words which apply well in all ages to the passion for organisation and precision. Though we cannot prove it, I myself have little doubt that the members of the college, or some of them, collected and invented formulae simply for the pleasure of doing it, and that the work became as congenial to them as the systematisation of the law to Jewish scribes after the captivity, or as casuistry to the confessors of the middle ages. When the art of writing became familiar to experts, the natural and primitive desire of the Roman to have exactness in the spoken word affected him also in his relations with the word as written. The scribe and the Pharisee found their opportunity. The whole public religion of the State, and to some extent also the private religion of the family, became a mass of forms and formulae, and never succeeded in freeing itself from these fetters.