41.(Pg. [156]) How are octaves produced?
42.(Pg. [156]) How are fifths produced?
43.(Pg. [156]) How major and minor thirds?
44.(Pg. [156]) What is meant by melody, and in what particular does it differ from harmony?
CONVERSATION XIV.
ON OPTICS.
OF LUMINOUS, TRANSPARENT, AND OPAQUE BODIES. OF THE RADIATION OF LIGHT. OF SHADOWS. OF THE REFLECTION OF LIGHT. OPAQUE BODIES SEEN ONLY BY REFLECTED LIGHT. VISION EXPLAINED. CAMERA OBSCURA. IMAGE OF OBJECTS ON THE RETINA.