What kind of signs could be in question? It may seem to outsiders that the most wonderful system of signs would be needed for every content of one mind to be communicated to another. But here again we must first reduce the exaggerated claims to the simpler reality. When Beulah makes card experiments, the whole words jack, queen, king, spade, club, heart, diamond, come to her mind, but when she makes word experiments, never under any circumstances does a real word come to her consciousness, but only single letters. Why is this? If king and queen can be transmitted from mind to mind, why not dog and cat? Yet when the mother thinks of dog, it is always only first D, and after a while O, and finally G which creeps into her mind. This difference seems to me most characteristic, because it indicates very clearly that the whole performance is possible only when the communicated content belongs to a small list which can be easily counted. There are only three face cards, only four suites, only ten numbers, and only twenty-six letters, but there are ten thousand words and more. It is easy to connect every one of the ten numbers or every one of the twenty-six letters with a particular sign, but it would be impossible to have a sign for every one of the ten thousand words. Yet if we had to do with real mind-reading, it ought to make no difference whether we transmit the letter D or the word dog. This fact that she can recognize words only by slow spelling, while the faces and the suites of the cards and the names of the numbers come as full words, seems to me to point most clearly to the whole key of the situation. Anything which cannot be brought into such a simple number series, for instance, a colour impression, can never be transmitted. If the mother looks at the ace of diamonds, Beulah says that she sees the red of the diamond before her in her mind, but if the mother looks at the picture of a blue lake, this blue impression can never arise in Beulah's mind, but only the letters B-L-U-E.
Moreover, I observed that for Beulah the letters of the alphabet were indeed connected with numbers, as in seeking a letter she has a habit of going through the alphabet and at the same time moving one finger after another. Thus she feels each letter as having a definite place in her series of finger movements, and the finger movements themselves are often counted by her, so that each letter is finally connected with a special number. This, indeed, reduces the situation to rather a simple scheme. She succeeds only if her mother or sister is present and if her eyes are open, and she succeeds only with material which can be easily counted. A very short system of simple signs would thus be entirely sufficient to communicate everything which her mind-reading brings to her. As to the particular signs, I do not yet feel sure. It would probably take months of careful examination before I should find them out, just as in Germany it has taken months for scholars to discover the unintentional signs which the owner of a trick horse made, from which the horse was apparently able to calculate. I have no time to carry on such an investigation in this case, the more as I do not see that any new insight could be gained by it.