[6] See Proceedings S.P.R., vol. iv. pp. 29-33.
[7] See Proceedings S.P.R., vol. iv. pp. 33-35.
[8] Vol. vii. pp. 146-198 and pp. 383-394.
[9] For full account see Proceedings S.P.R., vol. vii. pp. 159-160.
[10] Proceedings S.P.R., vol. vii. p. 160.
[11] See the full account in Part XIX. of the Proceedings of the S.P.R., which part is included in vol. vii., and may be obtained separately for 2s. 6d.
[12] See Proceedings S.P.R., vol. vii. pp. 383-394.
CHAPTER III
THE PRODUCTION OF SOUND WITHOUT ANY
APPARENT PHYSICAL CAUSE
If the tipping of small tables when the hands of the sitters are in contact is excepted—under which circumstances it is generally impossible to determine whether the result is psychical, or due merely to muscular action unconsciously exercised—the production of raps and other sounds is the most frequent of the phenomena under consideration. They are, however, generally so intermixed with other phenomena that it is difficult to treat them separately.