LECTURE PAGE
I. GUSTAV MAGNUS. IN MEMORIAM 1
II. ON THE ORIGIN AND SIGNIFICANCE OF GEOMETRICAL AXIOMS 27
III. ON THE RELATION OF OPTICS TO PAINTING 73
I. Form 78
II. Shade 94
III. Colour 110
IV. Harmony of Colour 124
IV. ON THE ORIGIN OF THE PLANETARY SYSTEM 139
V. ON THOUGHT IN MEDICINE 199
VI. ON ACADEMIC FREEDOM IN GERMAN UNIVERSITIES 237
VII. HERMANN VON HELMHOLTZ. AN AUTOBIOGRAPHICAL SKETCH 266