In an interview with Cleveland Moffett printed in the June, 1893 issue of McClure's Magazine (available as scanned images from Google Books and in plain text from Project Gutenberg), Bell starts by discussing air-ships of the near future (airplanes) and seeing at a distance via electricity (television) before revealing his intent to go beyond mere telephony or television with his experiments into electric telepathy:
THOUGHT TRANSFERENCE BY ELECTRICITY.
After he had spoken of this idea [television] for some time, Professor Bell stopped suddenly, and, with an amused twinkle in his eyes, exclaimed: "But while we are talking of all this, what is to prevent some one from discovering a way of thinking at a distance by electricity?"
Having said this, the genial professor threw himself back and laughed heartily at the amazement his words awakened. Was he joking? Apparently not, for he proceeded seriously to discuss one of the most astounding conceptions that ever entered an inventor's mind. Thinking by electricity! Imagine two persons, one thousand or ten thousand miles apart, placed in communication electrically, in such a way that, without any spoken word, without sounding-board, key, or any bodily movement, the one receives instantly the thoughts of the other, and instantly sends back his own thoughts. The wife in New York knows what is passing in the brain of her husband in Paris. The husband has the same knowledge. What boundless possibilities, to be sure, this arrangement offers for business men, lovers, humorous writers, and the police authorities!
Preposterous as such an idea appears in its first conception, it certainly assumes an increasing plausibility when one listens to Professor Bell's reasoning.
"After all," he says, "what would there be in such a system more mysterious than in the processes of the mind reader? You substitute a wire and batteries for a strange-eyed man in a dress suit, that is all."
The logical basis of Professor Bell's scheme is clear, and its details quite beautiful in their simplicity, when you admit his major premise. That premise is that the human brain is merely a kind of electrical reservoir, and that thinking is nothing more than an electrical disturbance, like the aurora borealis or the sparks from a Holtz machine. The nerves are the wires leading from the central battery in the head. The reasonableness of this assumption is increased when one remembers that electricity may be made to act upon the nerves, even in a lifeless body, so as to produce the same muscular contractions which are produced by the brain force, whatever that may be. We talk of animal magnetism. What if it were the same as any other kind of magnetism? If these two forces are identical in one respect, why may they not be so in all respects? So Professor Bell reasons, and granting that the human brain is merely a store-house of electricity for our bodily needs, of electricity not essentially different from that which we know elsewhere, it must be possible to apply the same electrical laws to the brain as to any other electric apparatus and to get similar results.
"Do you begin to see my idea?" said Professor Bell, growing more and more enthusiastic as he proceeded. Then he gave a rapid outline of what might be a system of thinking by electricity.
Everyone knows, who knows anything about the subject, that an electric current passing inside of a coil of wire induces an electric current in that wire. Now, if the human brain be taken as a battery, then currents are constantly passing from it to various parts of the body, and the head may be considered in a state of constant electrical excitement, the intensity varying with the character of the thought processes. Now, suppose a coil of wire properly prepared in the shape of a helmet, and fitted about the head of one person, with wires attached and connected with a helmet similarly fitted upon the head of another person at any convenient distance. Every electric current in the one human battery must induce a current in the coil around the head, which current must be transmitted to the other coil. This other coil must then, by the reversed process, induce a current in the brain within helmet No. 2, and that person must receive some cerebral sensation. This cerebral sensation might be a thought, and probably would be, if it turns out to be true that brain force is identical with electricity. In that case, the thought of the one person would have produced a thought in the other person, and there is, if we go as far as this, every reason to believe that it would be the same thought. Thus the problem of thinking at a distance by electricity would be solved.
So much for a curious theory of what might be, if so and so were true; but Professor Bell has not stopped with theories, but has actually begun to put them to the test. Not that he is over-sanguine as to the result, but he believes the experiment worth the making, and that seriously. He has actually had two helmets, such as those described, constructed, and has begun a series of experiments in his laboratory. Thus far, the results have been for the most part negative, but not so much so as to prevent him hoping that more perfect appliances may lead to something more conclusive. It is true that the thought in one brain has produced a sensation in the other, through the two helmets, but what the relation was between the thought and the sensation could not be determined.
(The rest of the interview is about using electricity to stimulate the brain, albeit in a crude fashion, to allow the deaf to hear and the blind to see.)
Information about Bell's thought transference helmet seems to have been suppressed. I can find no other reference to it other than this interview, nor any pictures of the helmets he had constructed. The US Government, which hosts his family papers online, is, of course, unforthcoming.
Could it be that he was conclusive in his experiments, that he did discover the perfect appliance for the transference of thought via electricity? His initial success at producing a sensation, however hazy, suggests he was on to something.
But what if he was even more successful than he playfully let on to this reporter? What if he not only was able to communicate thoughts across great distances, but also transfer an electric copy of a brain to a storage capacitor?
According to Wikipedia, on his deathbed his wife Mabel whispered, "Don't leave me," to which Bell signed "No" before dying. Was this an acknowledgement that he had transferred his mind electrically before falling ill? And what of the special coffin constructed by his laboratory staff in which he was buried? Could the electric imprint of Alexander Graham Bell's consciousness be stored within a thought capacitor buried atop Beinn Bhreagh mountain, or perhaps secreted away somewhere within the facilities of Bell Laboratories, to be tapped into to produce the many discoveries and inventions for which they are famous?