It is usually impossible for the coincidence of time to be exact, because both mediums may not be sitting at the same time. But in some cases, wherein coincidence of subject is well marked, coincidence in time is of little moment; always provided that the subject is really an out-of-the-way or far-fetched one, and not one common to every English-speaking person, like Kitchener or Roberts or Jellicoe. Cross-correspondences are of various grades. The simplest kind is when two mediums both use the same exceptional word, or both refer to the same non-public event, without any normal reason that can be assigned. Another variety is when, say, three mediums refer to one and the same idea in different terms,--employing, for instance, different languages, like 'mors,' 'death,' and 'thanatos.' (See _Proc._, S.P.R., xxii, 295-304.) Another is when the idea is thoroughly masked and brought in only by some quotation--perhaps by a quotation the special significance of which is unknown to the medium who reproduces it, and is only detected and interpreted by a subsequent investigator to whom all the records are submitted. Sometimes a quotation is maltreated, evidently with intention, by the communicator; the important word to which attention is being directed being either omitted or changed. A large number of examples of this more complex kind of cross-correspondence are reported at length in the _Proceedings_ of the Society for Psychical Research; see especially vol. xxi. p. 369 and xxii. _passim_, or a briefer statement in _Survival of Man_, chap. xxv. Some of these instances as expounded by Mr. Piddington may seem extraordinarily complicated and purposely concealed. That is admitted. They are specially designed to eliminate the possibility of unintended and unconscious telepathy direct from one medium to another, and to throw the investigator back on what is asserted to be the truth, namely that the mind of one single communicator, or the combined mind of a group of communicators,--all men of letters,--is sending carefully designed messages through different channels, in order to prove primarily the reality of the operating intelligence, and incidentally the genuineness of the mediums who are capable of receiving and transmitting fragments of messages so worded as to appear to each of them separately mere meaningless jargon; though ultimately when all the messages are put together by a skilled person the meaning is luminous enough. Moreover, we are assured that the puzzles and hidden allusions contained in these messages are not more difficult than literary scholars are accustomed to; that, indeed, they are precisely of similar order.