Heim himself relates, that it sometimes happens that a person whose knowledge of the ground enables him to detect the presence of water will use the divining-rod, because of the greater impression thereby produced. In any case, I do not think that Heim paid sufficient attention to these sources of error, especially those arising from falsification of memory. Here, also, objective investigation is the only correct method of procedure; neither a priori negation nor uncritical assent is justifiable.

As I have already mentioned, the divining-rod was formerly used to find veins of metal, just as it is nowadays to find water. It has long been supposed that some metals have an influence on certain persons, and the assumption has been made use of in medicine. We must here include Burq's metalloscopy and metallotherapy, in which, however, there was contact with the metals. Certain persons were supposed to be influenced by particular metals - copper, for example - which even caused symptoms of disease to disappear. Such assertions were made long ago. Brandis, for example, observed pain and convulsions result from contact with gold and silver.

The later investigations on the action of drugs at a distance apparently proved that certain drugs in hermetically closed tubes would, when brought close to human beings, act in the same way as if they were administered internally. Thus, strychnine was supposed to cause convulsions, ipecacuanha vomiting, opium sleep, alcohol drunkenness.

Experiments of this kind were also made even earlier. In the eighteenth century Pivati of Venice asserted that if odorous substances were shut up in glass tubes, the fragrance would penetrate the glass and exert a specific influence on human subjects as soon as the tubes were rendered electric by friction. Verati and Bianchi found this correct, and so did Winkler, professor of philosophy at Leipzig. As a result, such tubes were much used at Leipzig for the treatment of disease during the middle of the. eighteenth century. There were anti-apoplectic tubes, anti-hysterical tubes, etc. Abbe Nollet then went to Italy to investigate the matter, but he was unable to confirm the phenomena. He found that the statements that had been made were the outcome of inaccurate observation, exaggeration, and fraud. Bianchini, professor of medicine at Padua, came to the same conclusion (Lichtenberg).

Similar experiments were more recently made by Grocco in Italy, and Bourru and Burot in Rochefort. They experimented with both waking and hypnotized subjects; Luys and Dufour repeated the experiments with hypnotized subjects, and confirmed them; so did Duplouy, Alliot, and Peter. The last-named even asserted, on the strength of experiments he had carried out on one subject with Caron and Martinet, that contact with gold would produce a burn of the second degree, without the subject knowing what had touched him. So far as can be seen, the experiment was not very carefully carried out. Luys went farther; he even found distinctions, according as the ipecacuanha was applied to the right or left side. These experiments have been repeated by many other investigators - e.g., by Jules Voisin, Forel, Seguin, and Laufenauer, without result; Luys brought the subject before the French Academy of Medicine, which appointed a commission (Brouardel, Dujardin-Beaumetz, and several others) to test the question in the presence of Luys; they came to a conclusion opposed to his. Seeligmuller also attacked Luys' experiments, and proved that the conditions were not sufficiently stringent; the Nancy school came to the same conclusion. Suggestion and training were shown to be the chief sources of error.

The subject's great suggestibility enables him to gather from the experimenter's manner what is wanted of him. For this reason the Nancy school raised the objection that no experiments on the action of drugs at a distance could be considered conclusive if any one acquainted with the contents of the tubes were in the room. I am unacquainted with any series of experiments in which these conditions were strictly adhered to and the subject nevertheless exhibited the correct reaction.

In the preceding part of this chapter I (The History Of Hypnotism) have discussed questions that are usually included in the domain of occultism. I had already mentioned some points in this connection in the previous chapter. Many believers in these occultistic phenomena go much farther. This is particularly noticeable in their attitude towards spiritism, of which many occultists are followers even if they do not always admit the fact. Of course one may be a believer in animal magnetism, thought-reading, or even in spatial and previsional clairvoyance, without that necessarily making one a spiritist. Spiritism is the doctrine or belief that spirits, more especially those of the dead, appear to human beings under certain circumstances. The presence of certain persons, called mediums, who act as intermediaries between the spirits and human beings, is said to be a preliminary condition. Sometimes the manifestations of the spirits consist of raps which can be heard at different parts of the room, on tables, chairs, the walls, etc., and by means of these raps the audience and the supposed spirits are often able to carry on a conversation; at other times, objects in the room begin to move of their own accord - e.g., the furniture jumps about without any perceptible mechanical assistance.

But the most important manifestation is the materialization of spirits. The spirit manifests itself not merely by raps and the like, but its astral body appears - i.e., the body which under normal conditions constitutes the ethereal frame of the soul. It is easy to understand that a person may believe in other occultistic phenomena without being a spiritist and tracing such phenomena to the spirits of the dead, and, as I have already mentioned, the mentalists are opposed to spiritism in the narrower sense of the term. In spite of this, it cannot be denied that there is a connection between occultism and spiritism (in the restricted sense). Spiritists readily admit that clairvoyance is a means of obtaining glimpses of the spirit-world which is hidden to the view of human beings in a normal state. Conversely, it is asserted that the only explanation of clairvoyance is that the spirits inform the medium of the things to be seen. We generally observe that whoever believes in the phenomena of one domain of occultism - e.g., animal magnetism - takes the phenomena of all the other domains for granted.