There are undoubtedly many other methods used by mediums for this purpose; but if the sitter who has obtained spirit extras under test conditions carefully considers the procedure employed, in the light of the suggestions made above, he will probably find that several loopholes were left by which fraud might have been introduced. _B.--Experiments in Fraud_ The argument most frequently brought forward, in favour of the genuineness of spirit photographs, is that the conditions employed in their taking leave no loophole for fraud. It has been pointed out in the preceding section that the usual “test conditions” leave not one, but many, such loopholes. Evidence of fraud has at some time or other been brought against most spirit photograph mediums, and they have consequently been more or less discredited. Other mediums have been more clever--or more fortunate--and many people therefore argue that they are not all to be tarred with the same brush; it is pointed out that spirit extras _have_ been obtained under the strictest conditions imposed by acute observers who have found nothing suspicious of trickery. It occurred to me that the most effective way to refute this argument was actually to produce bogus spirit photographs under similar, or even more stringent, test conditions. This I accordingly attempted in a series of _séances_, held in my rooms at Cambridge in the summer of 1919. At four of these _séances_ photographs were taken, and on each occasion one plate showed a more or less conventional spirit extra. As I was experimenting primarily for my own satisfaction, my seven victims were drawn from among my own friends, and were enjoined to keep the matter as quiet as possible. They were not, of course, specially trained psychic researchers, but could not, I think, be considered as being particularly easy men to deceive. Five of the seven were ex-Service men, and all were of B.A. or “fourth year” University status; they included two chemists, two medical students, a geologist, and two physiologists who were also studying psychology. They were all therefore of a scientific bent, and, with possibly one exception, were completely sceptical about spiritualistic phenomena when the experiments started.