Crookes felt that he had a duty as a scientist to investigate the phenomena related to the wider question of whether or not there is any part of us which survives physical death.
The phenomena he researched in regard to this question largely focussed on claims of materialization mediumship (or "physical mediumship") - individuals who claimed to act as an agent through which spirits from the other side could draw on a substance from the mediums own body known as ectoplasm to mould into their form and manifest themselves in our physical reality.
Crookes was determined to conduct an impartial investigation into these claims and imposed the condition on mediums that they must do their sittings at his own house, with his own selection fo friends present and under strictly controlled conditions which he sets.
Crookes was able to study the famous mediums of his day including Kate Fox, Florence Cook and Daniel Dunglas Home and came the conclusion through his research that these mediums were at the very least producing phenomena which cannot be explained via ordinary means.
Medium Florence Cook was said to be fully materializing the spirit of a woman named Katie King in seances which began around the year 1871. Florence was only about 15 years old when the pheneomena began.
Katie King was said to look very similar to the medium Florance Cook, which aroused skepticism that Florance and Katie King were simply the same person, with Florence mascurading around as a ghost.
When William Crookes attended one of Cook's seances, he claimed to have heard moaning from within the spirit cabinet which lead him to wonder whether Florance and Katie may well be seperate individuals. This event made Crookes determined to conduct a thorough investigation of Florence Cooks mediumship. In his investigation of Florence Cook, William Crookes asked the medium to stay at his home and perform seances. This way Crookes would be fully in control of the investigation and hope to rule out fraud.
In support of Katie King and Florence Cook being two seperate individuals, Crookes as well as other witnesses noted several physical differences between the two. Katie was larger built. Different colour hair. Unpierced ears. Florence at one stage was found to have a blister on her neck, whilst Katie did not.
William Crookes had this to say about the idea of Katie King and Florence Cook being the same person:
"I have the most absolute certainty that Miss Cook and Katie are two separate individuals so far as their bodies are concerned. Several little marks on Miss Cook’s face are absent on Katie’s. Miss Cook’s hair is so dark a brown as to almost to appear black; a look at Katie’s, which is now before me, and which she allowed me to cut from her luxuriant tresses, having first traced it up to the scalp and satisfied myself that that it actually grew there, is a rich golden auburn.”
In addition to this, William Crookes also said:
“[For approximately six months] Miss Cook has been a frequent visitor at my house, remaining sometimes a week at a time. She brings nothing with her but a little hand bag, not locked; during the day she is constantly in the presence of Mrs. Crookes, myself, or some other member of the family, and, not sleeping by herself, there is absolutely no opportunity for any preparation even of a less elaborate character than would be required for enacting Katie King.”
Could it be possible that it was in fact an accomplice masquerading as Katie King? A likely candidate perhaps being Florence Cook's sister.
In the course of these experiments, William Crookes claimed to have actually witnessed Florence Cook and the alleged spirit of Katie King at the same time, however his accounts of these incidents appear to lack detail and to the highly skeptical it could still be argued that Crookes simply saw an accomplice who had her face covered by a hood, whilst Florence Cook was acting the part of Katie King.
Could it have been an accomplice? According to William Crookes:
“I prepare and arrange my library myself as the dark cabinet, and usually, after Miss Cook has been dining and conversing with us, and scarcely out of our sight for a minute, she walks direct into the cabinet, and I, at here request, lock its second door, and keep possession of the key all through the séance; the gas is then turned out, and Miss Cook is left in the darkness. On entering the cabinet, Miss Cook lies down upon the floor, with her head on the pillow, and is soon entranced."
It seems difficult to imagine how an accomplice could have entered into this arrangement without such things as trap doors, which would not have been present in Crookes' home, under the controlled conditions.
It is said that William Crookes took numerous photographs of these materializations but it seems the vast majority of these photographs are no longer available.
9 December, 1873 - A man named William Volckman attended one of Florence Cook's seances. Volckman was a skeptic and believed that Katie King and Florence Cook were one and the same person. In order to prove this theory, during the seance he waited for Katie King to materialize and then made a grab for the alleged spirit. A struggle then took place, Volckman was then held back by other sitters and the alleged spirit of Katie King escaped back into the spirit cabinet. Once things had calmed down about 5 minuets later, the curtain of the spirit cabinet was pulled back- and Florence was still there securely bound- the seals unbroken. An examination of Florence also found no trace of the white clothes that Katie King wore.
This "exposure" did cast much doubt on the mediumship of Florence Cook, however some would also question Volckman's motives and there are theories that he may have been hired on a deliberate agenda to try and discredit her mediumship.
The fact is Florence Cook was brought to William Crookes' home and examined under strict conditions by a man of science and the materializations occurred under various levels of lighting and photographic and physical evidence was captured on numerous occasions. William Crookes felt completely certain that Katie King and Florence Cook were NOT the same individual- having examined them and also seen them both together on some occasions. His strict conditions also appear to rule out the idea of an accomplice acting as Katie King. It must be said however that William Crooke's notes on the subject lack detail and do to some extent require an element of faith in his word. His testimony is certainly valuable due to his scientific credibility.