The next series of experiments are those of Sir William Crookes. They will be found described in full in his book, Researches in Spiritualism, to which I would refer the reader. I might summarize one series of experiments, perhaps, as follows. On a table was placed a tightly stretched membrane, forming a sort of drumhead. The lower side of this rested on the table, so that the apparatus really resembled a tambourine more than anything else. Now, without having the apparatus explained to her in any way, a lady was brought into the room, and requested to place her hands on the table on which the drumhead rested, so that no contact whatever was possible between the membrane and the hands of the medium. But, to make assurance doubly sure, Sir William placed his hands over those of the medium, in order to detect any conscious or unconscious movement on her part. (All this was in full light.) The account goes on: "Presently percussive noises were heard on the parchment, resembling the dropping of grains of sand on its surface. At each percussion a fragment of graphite which I had placed on the membrane was seen to be projected upward about 1-50th of an inch. . . . Sometime the sounds were as rapid as those from an induction coil, whilst at others they were more than a second apart" (p. 39).
The description of the various kinds of raps noticed at different times is most interesting. On p. 86 we read: "The popular name of 'raps' conveys a very erroneous impression of this class of phenomena. At different times, during my experiments, I have heard delicate ticks, as with the point of a pin, a cascade of sharp sounds as from an induction coil in full work, detonations in the air, sharp metallic taps, a crackling like that heard when a frictional machine is at work, sounds like scratching, the twittering of a bird," etc.
Again, on p. 87, Sir William writes:
"I have heard them (the raps) in a living tree, on a sheet of glass,
on a stretched iron wire, on a stretched membrane, a tambourine, on the
roof of a cab and on the floor of a theatre. Moreover, actual contact is
not always necessary; I have heard these sounds proceeding from the floor,
walls, etc., when the medium's hands and feet were held, when she was standing
on a chair, when she was suspended in a swing from the ceiling, when she
was enclosed in a wire cage, and when she had fallen fainting on a sofa.
I have heard them on a glass harmonicon, I have felt them on my own shoulder
and under my own hands. I have heard them on a sheet of paper, held between
the fingers by a piece of thread passed through one corner. With a full
knowledge of the numerous theories which have been started, chiefly in
America, to explain these sounds, I have tested them in every way that
I could devise, until there has been no escape from the conviction that
they were true objective occurrences not produced by trickery or mechanical