In photography there are several ways of defrauding; the most usual is by double exposure. A shrewd use of sulphite of quinine permits of certain curious operations, it appears. I have not verified this. CHAPTER V PSYCHO-SENSORY AND INTELLECTUAL PHENOMENA Under this somewhat vague title I am bringing certain facts together, which differ greatly from those I have been examining. In reality, the facts so far related by me refer to material manifestations, and it was merely as an accessory, that I pointed out the intelligent character some of these manifestations presented. I will now describe the means best adapted for obtaining not _physical_ but _intellectual_ phenomena, properly so-called; that is to say, phenomena which are interesting solely because of the ideas expressed, or because of the signification of the images produced, and not at all because of the conditions under which they are obtained. I have studied this category of phenomena with less interest than sonorous, motor or luminous phenomena, where observation is relatively simple. Intellectual phenomena can only be studied indirectly, and in order to verify them, we are generally obliged to trust to the statement of a third person. I think these are bad conditions of observation. This reserve made, I will divide these phenomena into two wide categories:— 1. Sensory automatism. 2. Motor automatism. I. SENSORY AUTOMATISM I thus designate phenomena produced by the spontaneous activity of our senses, and which do not appear to be due to exterior excitation. They border on hallucination. They are observed in the different sensory spheres. I will only examine olfactory, auditory, and visual sensations; tactile impressions were studied in the last chapter. As for gustatory sensations, they are very rare and without interest. (_a_) _Olfactory sensations._—These consist of a special odour. I have never observed any in the seances at which I have been present. In one series, however, the medium associated the odour of Jasmine with the manifestation of certain personifications. To me this sensation seemed to be purely subjective; it was constant. An odour of ozone is often perceived after luminous phenomena have been obtained, a fact which ought to be borne in mind. It may be compared with the odour of ozone, perceived in the vicinity of powerful static machines, which give off electricity at _very high potentiality_. Here is an analogy which is, perhaps, not altogether fortuitous; these facts, however, are unintelligible. (_b_) _Auditory sensations._—I do not speak of sonorous phenomena. I now enter directly into the study of intellectual phenomena, that is to say, phenomena having a signification more or less precise and intelligible.