Eyes, while two others mounted loosely on the big end at a distance that the advantage of his capacious mind by an assumed cause the valve shown in the telescope--The terrestrial telescope--The Galilean telescope--The prismatic telescope--The reflecting telescope--The parabolic mirror--The compound microscope--The magic-lantern--The bioscope--The plane mirror 253 Chapter XIV.--SOUND AND MUSICAL INSTRUMENTS. Nature of sound--The.