© Tom Lethbridge 1969 
There are other ways of using the pendulum to the one we employ by using rates. The most popular is that of using a short cord of roughly 6 inches long. Most operators use this method in conjunction with a very large number of samples of what they want to look for, whether it be traces of tuberculosis or a golden treasure. The principle is that the pendulum will swing backwards and forwards between two things of like kind, two nickel pennies, or two lumps of alabaster, and will gyrate when the two specimens are of different materials. With sexes, however, this is reversed. The pendulum gyrates between two males and oscillates between a male and a female.
We have found a number of practical uses for the short pendulum. It will say at once what foods or drinks are good for you, by oscillating when you swing it between you and something good and the reverse when it is harmful. There is no difficulty in picking out the poisonous alimentary canal of a lobster or the dangerous parts of a crab. Pills which do not suit you cause an immediate gyration. But it has none of the advantages of being adaptable to accurate measurement of the other method and, although I have tried it for the apparently most improbable art of finding things from maps, I have not done much of this and have never been able to check up to see whether it told the truth.
We have however used the short pendulum for quite another purpose, and that was in an experiment to attempt to demonstrate pendulum telepathy. Telepathy, a branch of parapsychology, is almost universally accepted now and has in fact been suggested as a factor in evolution. However, we wished to see if we could demonstrate it in connection with the rates. For this purpose we chose the sex rates as something which could easily be recognized. I had a considerable number of one species of fossil sea-urchin for I always pick one up when I happen to see it.  They are heart-shaped casts of the interiors of the shells. There is a considerable difference in size and pattern between those which react to the male rate and those which the pendulum designates as female.
For the other part of this experiment we took two sterilized bottles containing some male and female hair respectively. When a bottle of male hair is placed opposite a male fossil and the short pendulum is swung between, there is opposition. The pendulum gyrates because the ray is turned back on itself. If, however, you repeat the performance with a bottle of male hair and a female sea-urchin the pendulum oscillates backwards and forwards. The ray passes uninterrupted between the two. If you substitute female hair for male, of course you get the reverse result.
Now what we wanted to find out was whether if one operator swung the short pendulum between two specimens in one place, a second operator in a different room could tell what result was being obtained by the first. The second operator, who could neither see nor hear the first, was to use a long pendulum tuned in to either the male or the female rate of the sample of hair taken to be used against a fossil by the first operator.
There was nothing but a slate floor under the long pendulum and a concrete floor beneath the short one. The two floors were on different floor levels and there was a thick stone wall between. Nothing could be seen or heard between the two rooms. The long pendulum was entirely on its own, and its operator did not point in the supposed direction of the short one. Everything was as secure as we could make it and it seemed evident that if the second operator obtained correct results on the long pendulum the information was being conveyed by mechanical telepathy. Watches were synchronized, and at given times the first operator swung the short pendulum between two fossils while the second operator, in ignorance of what sex of fossil was being tested in the other room, swung the long pendulum.
We found that which ever of us operated which pendulum, the long one always gave the correct answer to the sex of the fossil being tested. You could change the operators about, change the sex of the hair and the rate on the long pendulum and change the sex of the fossil. It could not deceive the pendulum.
Of course, to prove this, the experiment ought to be performed hundreds of times. A warning is, however, necessary here. All pendulum work entails the use of some current from the operatorís body to project the ray through the pendulum. As far as our work goes, we find that a great deal of current is in fact used up and the operator soon becomes tired. After testing for sex and thought rates in 110 sling stones, I was very tired. I think that it is most probable that, if you did more than a couple of dozen of these telepathic experiments at one time, the operators would become tired and errors would start to creep in. I do not know and the number is a guess. However I think that this would happen.
Probably the way to test whether the operators are becoming tired is by using the psi rate of 9Ĺ. This I regard as a measure of potential. You measure it by counting the number of turns made before the pendulum ceases to gyrate. We have tested 84 people for their psi rates. This can be found from their handwriting just as well as by reading direct from the actual person.
Fifty-four persons had what we may perhaps speak of as psi potentials of varying values. They range from 0 to at least 50, but they are not constant. They go up and down according to the personís bodily condition. During bronchitis, one guinea pigís potential dropped from a normal of about 45 to 30, and remained there till the illness was over.
People with a potential of 15 and upwards can usually work the pendulum quite well. The only professional medium whose writing we were able to test was no higher than 18, whereas we had about a dozen of 45 or over. From around 30 and upwards people seem liable to have more extra-temporal and other unusual experiences than most of their neighbours.
There remains more than a third of the selected group who have no reading on 9Ĺ. Instead they have one on the opposite side of the circle at 29Ĺ, which we are calling minus psi. It is seldom very large, and when small fluctuates to the positive side and becomes 9Ĺ.
When we tested the few minus psi persons who had a reading of 30 or over, we found that they were in poor health according to what the pendulum reported. They showed as rather bad readings for the nervous system in particular. There were generally traces of something else wrong as well.
By no means all persons with bad nervous readings have minus psi potential, but it is something which is worth bearing in mind. Animals have psi readings and such cats as have been tested mostly have a potential of about 45, as high as any human in fact. Dogs we have not yet tried.
It seems evident that a psi potential is really a necessary part of the human make-up, but in many cases it is becoming weak, or converted into something else. Since examining nervous cases with the pendulum is intensely exhausting, it seems probable that the minus psi draws current from plus psi and these people become, in a sense, vampires. Many readers must have experienced a feeling of exhaustion after being in close company with another person. This is, I think, due to the leakage from plus to minus psi. It flows from the highest to the lowest and those persons whose psi is normally under about 10 probably never experience this phenomenon at all.
With much practice in pendulum work your normal psi rate appears to rise, but this does not warrant too much use of the instrument at any one time. This leads to exhaustion. Should one suspect that another person is draining power from you, it can be checked to some extent by being outside the range of the rates, that is 40 + 40 inches.
Although psi is in many ways similar to electro-magnetism, it is by no means the same. For one thing, we have seen that it does not diminish with the square of the distance. For another, it can pass up from the three-dimensional earth plane into a second and third. Psi is not bounded by time, or distance, as we know them. As I have suggested in another book, it may well be the same force as that which operates gravity. It also appears to be related to ultra-sonic sound. This is the force which has to be considered when thinking about both telepathy and psychometry.
Of course you cannot have one without the other. Telepathy has to be used by the psychometrist to extract impressions from an object in such a way that they may be comprehensible to the mind. We usually think of telepathy as being the process where a single idea appears to arrive almost simultaneously in the minds of two people. This seems to be a chance happening and it is often difficult to establish which mind originated the thought.
But telepathy is much wider than this and in the case of animals it is clear that individuals of differing species can carry on conversations by its means. In the case of birds, whole flocks operate as one, wheeling and diving with no word of command. Telepathy, in fact, is an alternative method to speech as a means of communication, and can be quite deliberate.
I said that the psychometrist must make use of telepathy and this may seem an inaccurate statement. But telepathy has to be the means by which the information stored in the field of an object can be transferred to the mind of the operator. The information may be pictorial, or in sound form, but whatever form it takes it cannot pass into the operatorís mind by its own action. Telepathy provides the beam on which it passes.
The beam can, as we have seen, be broken down into various rates and these we are beginning to appreciate, even if we do not know what they really are. But then does anyone honestly believe that he understands electricity? He may know all there is to know about harnessing the force, but what it really is remains an enigma.
It is the same with telepathy. We may know that it can transfer thought forms from one mind to another, or from one object to one mind. We may soon learn to control it in the manner that electricity is controlled. Yet it may never be possible to say what it really is, beyond the vague statement that it consists of high velocity vibrations.
There we will leave telepathy for the moment, having demonstrated, I hope, that it can be utilized mechanically in the manner that electricity can be so utilized. We can, moreover, note that we have now two branches of parapsychology, telepathy and psychometry, both of which seem capable of being studied in a normal scientific manner, but both of which are evidently outside the range of three-dimensional science.
 Source: Chapter 9 of The Monkey's Tail - a study in evolution and parapsychology; Routledge & Kegan Paul, 1969, SBN 7100 6598 1.
 I described my attempts to demonstrate pendulum telepathy in some detail in a former book, Ghost and Diving Rod which also contains a detailed account of my experiment with sea-urchins.