It often happens that news is most uncertain at the moment when it is most important. He should therefore take care to transmit it in the proper setting of all its attendant circumstances, so that the prince may have some material by which to judge whether the advice of his ambassador is well founded. There is no doubt that in crises of this kind the habit of private correspondence between the Foreign Minister and the King and his ministers abroad is of the utmost use, for it enables them to discuss all questions with a freedom which is denied to despatches of a more formal kind; and it will often place the home government in possession of knowledge which will be of the utmost value to them. And since a true judgment of events in one country will often depend upon what is happening in others, a diplomatist in foreign parts will ever keep in touch with his colleagues in other foreign countries, so that he may be informed of the course of events elsewhere. This co-operation between ambassadors abroad is one of the most useful features in diplomacy. [Sidenote: _Ciphers._] As secrecy is the very soul of diplomacy, the art of writing letters in cipher has been invented in order to disguise the written message, but unless the cipher is unusually clever the industry of men, whose wits are sharpened by necessity and by self-interest, will not fail to discover the key to it. Indeed, to such a pitch has this been brought that there are now men who are known as professional decipherers, though in all probability, as I believe, their reputation rests largely upon the ineptitude of poor ciphers rather than upon their discovery of a good cipher. For as a matter of fact experience shows that a well-made and well-guarded cipher is practically undiscoverable except by some betrayal, that is to say, that the wits even of the cleverest student of ciphers will fail to pierce its secret unless aided by corruption. It is therefore the duty of the ambassador, having satisfied himself that the ciphers of his government are adroitly made, to take all means for their due protection, and especially to satisfy himself that the staff of his embassy understand not only the use of the cipher itself, but the extreme importance of guarding it from unauthorised eyes. And certainly the ambassador ought not to adopt the indolent practice, of which I have known one or two cases, where the less important part of a despatch was written _en clair_, and the ambassador himself added the vital part in cipher. Action of that kind is a masterpiece of futility, for it leads directly to the compromise of the cipher itself. For if the letter fall into enemy hands it will not be difficult for a clever spy to divine the manner of the sentence in cipher from the context written _en clair_. In a word, the ambassador and his staff should guard a cipher as they would the inmost secrets of their own hearts. A really effective cipher is literally worth far more than its weight in gold.