Wednesday, August 7, 1867. — We walked down to the Porto da Ponte Grande, where the ajojo or raft lay. I never saw such an old Noah’s Ark, with its standing awning, a floating gipsy “pál,” some seven feet high and twenty-two long, and pitched like a tent upon two hollowed logs. The river must indeed be safe, if this article can get down without accident.
If the human brain is exposed to one frequency in the left ear which is 10 Hertz below another audible frequency played in the right ear, rather than hearing either of the two audible frequencies, the brain chooses to “hear” the difference between them, the “beat” frequency.
Since the Theta level is associated with sleep, the subject concerned may progress from a fully awake to a sleep state (provided that he does not consciously resist) as the brain strives to entrain its wave frequency output with the one which the person hears.