affected the result, the amount of deviation of the later observations from the earlier in each tenth of a degree of magnitude would be represented by a smooth curve. As a matter of fact, it was found that the number of cases of complete agreement were much greater, with some observers more than 50 per cent. greater, than they should have been on an estimate of the probabilities. At first sight this excess of the actual over the theoretical numbers suggested the action of thought-transference between the assistant and the observer. But Professor Pickering shows, on a further analysis of the figures, that almost the whole of the excess was due to the preference of both the earlier and the later observers for 5 and 10 over all other fractions of a degree. The practical deduction from this investigation is that in any experiment care should be taken to exclude, as regards the agent at any rate, the operation of any diagram or number-habit.[14] If an object is thought of, it should if possible be chosen by lot, and should not be an object actually present in the room. If a card, it should be drawn from the pack at random; if a number, from a receptacle containing a definite series of numbers; if a diagram, it is preferable that it should be taken at random from a set of previously-prepared drawings. It will be seen that in the majority of the cases quoted in the four succeeding chapters these precautions have been observed. FOOTNOTES: [Footnote 4: _Primary and Present State of the Solar System_, by P. McFarlane. Edinburgh, Thomas Grant, _circa_ 1845.] [Footnote 5: At the meeting of the British Association in 1844; quoted by Hugh Miller, _Testimony of the Rocks_, pp. 358, 359.] [Footnote 6: _A Brief and Complete Refutation of the Antiscriptural Theory of the Geologists_, by a Clergyman of the Church of England. London, 1853; quoted by Hugh Miller, _loc. cit._] [Footnote 7: _L'Hypnotisme et la suggestion mentale._ Germer Baillière et Cie. Paris, pp. 261-316.] [Footnote 8: _Revue Philosophique_, Nov. 1887, quoted in _Proceedings of the Soc. Psych. Research_, vol. iv. p. 532.] [Footnote 9: _Revue Philosophique_, March 1887.] [Footnote 10: Mrs. Verrall states that after long practice she "lost all consciousness of the means which enabled her to guess, and _saw_ pictures of the cards."] [Footnote 11: _Proceedings of the American Soc. Psych. Research_, pp. 302 _et seq._] [Footnote 12: No doubt the great preponderance of geometrical figures is in some measure due to the use of the word "diagram," which in English would probably suggest to most persons a geometrical diagram. But possibly the word has a different shade of meaning in American. It is certain too that a considerable proportion of the persons who filled in the cards were acquainted with the object of the inquiry.] [Footnote 13: _Proc. American Soc. Psych. Research_, pp. 35-43.]