In a biography of Bell, Reluctant Genius, Charlotte Gray writes:
One day, Bell went for a walk on a bluff overlooking the Grand River, near his parents’ house. A large tree had blown down here, creating a natural and completely private belvedere, which [he] had dubbed his “dreaming place.” Slouched on a wicker chair, his hands in his pockets, he stared unseeing at the swiftly flowing river below him. Far from the bustle of Boston and the pressure of competition from other eager inventors, he mulled over everything he had discovered about sound.
In that moment, Bell knew the answer to the puzzle of the harmonic telegraph. Electric currents could convey sound along a wire if they undulated in accordance with the sound waves.
Bell was clearly one in a million, a genius who went on to have ideas in an extraordinary number of areas—sound recording, flight, lasers, tetrahedral construction, and hydrofoil boats, to name a few. The telephone was his obsession. He approached it from a unique perspective, that of a speech therapist. He had put in years of preparation before that moment by the Grand River, and it was impossible to know what unconscious associations triggered his great insight. Invention has its own algorithm: genius, obsession, serendipity, and epiphany in some unknowable combination. How can you put that in a bottle?