Hearing, a most excellent outward sense, “by which we learn and get knowledge.” His object is sound, or that which is heard; the medium, air; organ, the ear. To the sound, which is a collision of the air, three things are required: a body to strike, as the hand of a musician, the body strucken, which must be solid and able to resist, as a bell, lute-string, not wool, or sponge; the medium, the air, which is inward or outward; the outward, being struck or collided by a solid body, still strikes the next air, until it come to that inward natural air, which as an exquisite organ is contained in a little skin formed like a drum-head, and struck upon by certain small instruments like drum-sticks, conveys the sound by a pair of nerves, appropriated to that use, to the common sense, as to a judge of sounds. There is a great variety and much delight in them; for the knowledge of which consult with Boethius and other musicians.