am now, on the termination of a work of several years' duration, in a position to review the general tenour of Leonardos writings, I may perhaps be permitted to add a word as to my own estimate of the value of their contents. I have already shown that it is due to nothing but a fortuitous succession of unfortunate circumstances, that we should not, long since, have known Leonardo, not merely as a Painter, but as an Author, a Philosopher, and a Naturalist. There can be no doubt that in more than one department his principles and discoveries were infinitely more in accord with the teachings of modern science, than with the views of his contemporaries. For this reason his extraordinary gifts and merits are far more likely to be appreciated in our own time than they could have been during the preceding centuries. He has been unjustly accused of having squandered his powers, by beginning a variety of studies and then, having hardly begun, throwing them aside. The truth is that the labours of three centuries have hardly sufficed for the elucidation of some of the problems which occupied his mighty mind.

Alexander von Humboldt has borne witness that "he was the first to start on the road towards the point where all the impressions of our senses converge in the idea of the Unity of Nature" Nay, yet more may be said. The very words which are inscribed on the monument of Alexander von Humboldt himself, at Berlin, are perhaps the most appropriate in which we can sum up our estimate of Leonardo's genius:

"Majestati naturae par ingenium."

LONDON, April 1883.

F. P. R.

CONTENTS OF VOLUME I.

PROLEGOMENA AND GENERAL INTRODUCTION TO THE BOOK ON PAINTING

Clavis Sigillorum and Index of Manuscripts.—The author's intention to publish his MSS. (1).—The preparation of the MSS. for publication (2).—Admonition to readers (3).—The disorder in the MSS. (4).—Suggestions for the arrangement of MSS. treating of particular subjects (5—8).—General introductions to the book on painting (9—13).—The plan of the book on painting (14—17).—The use of the book on painting (18).—Necessity of theoretical knowledge (19, 20).—The function of the eye (21—23).—Variability of the eye (24).—Focus of sight (25).—Differences of perception by one eye and by both eyes (26—29).—The comparative size of the image depends on the amount of light (30—39).

II.

LINEAR PERSPECTIVE

General remarks on perspective (40—41).—The elements of perspective:—of the point (42—46).—Of the line (47—48).—The nature of the outline (49).—Definition of perspective (50).—The perception of the object depends on the direction of the eye (51).—Experimental proof of the existence of the pyramid of sight (52—55).—The relations of the distance point to the vanishing point (55—56).—How to measure the pyramid of vision (57).—The production of the pyramid of vision (58—64).—Proof by experiment (65—66).—General conclusions (67).—That the contrary is impossible (68).—A parallel case (69).—The function of the eye, as explained by the camera obscura (70—71).—The practice of perspective (72—73).—Refraction of the rays falling upon the eye (74—75).—The inversion of the images (76).—The intersection of the rays (77—82).—Demonstration of perspective by means of a vertical glass plane (83—85.)—The angle of sight varies with the distance (86—88).—Opposite pyramids in juxtaposition (89).—On simple and complex perspective (90).—The proper distance of objects from the eye (91—92).—The relative size of objects with regard to their distance from the eye (93—98).—The apparent size of objects denned by calculation (99—106).—On natural perspective (107—109).

III.

SIX BOOKS ON LIGHT AND SHADE

GENERAL INTRODUCTION.—Prolegomena (110).—Scheme of the books on light and shade (111).—Different principles and plans of treatment (112—116).—Different sorts of light (117—118).—Definition of the nature of shadows (119—122).—Of the various kinds of shadows (123—125).—Of the various kinds of light (126—127).—General remarks (128—129).—FIRST BOOK ON LIGHT AND SHADE.—On the nature of light (130—131).—The difference between light and lustre (132—135).—The relations of luminous to illuminated bodies (136). —Experiments on the relation of light and shadow within a room (137—140).—Light and shadow with regard to the position of the eye (141—145).—The law of the incidence of light (146—147).—SECOND BOOK ON LIGHT AND SHADE.—Gradations of strength in the shadows (148—149).—On the intensity of shadows as dependent on the distance from the light (150—152).—On the proportion of light and shadow (153—157).—THIRD BOOK ON LIGHT AND SHADE.—Definition of derived shadow (158—159).—Different sorts of derived shadows (160—162).—On the relation of derived and primary shadow (163—165).—On the shape of derived shadows (166—174).—On the relative intensity of derived shadows (175—179).—Shadow as produced by two lights of different size (180—181).—The effect of light at different distances (182).—Further complications in the derived shadows (183—187).—FOURTH BOOK ON LIGHT AND SHADE.—On the shape of cast shadows (188—191).—On the outlines of cast shadows (192—195).—On the relative size of cast shadows (196. 197).—Effects on cast shadows by the tone of the back ground (198).—A disputed proposition (199).—On the relative depth of cast shadows (200—202).—FIFTH BOOK ON LIGHT AND SHADE.—Principles of reflection (203. 204).—On reverberation (205).—Reflection on water (206. 207).—Experiments with the mirror (208—210).—Appendix:—On shadows in movement (211—212).—SIXTH BOOK ON LIGHT AND SHADE.—The effect of rays passing through holes (213. 214).—On gradation of shadows (215. 216).—On relative proportion of light and shadows (216—221).

IV.

PERSPECTIVE OF DISAPPEARANCE

Definition (222. 223).—An illustration by experiment (224).—A guiding rule (225).—-An experiment (226).—On indistinctness at short distances (227—231).—On indistinctness at great distances (232—234).—The importance of light and shade in the Prospettiva de' perdimenti (235—239).—The effect of light or dark backgrounds on the apparent size of objects (240—250).—Propositions on Prospettiva de' perdimenti from MS. C. (250—262).

V.

THEORY OF COLOURS

The reciprocal effects of colours on objects placed opposite each other (263—271).—Combination of different colours in cast shadows (272).—The effect of colours in the camera obscura (273. 274).—On the colours of derived shadows (275. 276).—On the nature of colours (277. 278).—On gradations in the depth of colours (279. 280).—On the reflection of colours (281—283).—On the use of dark and light colours in painting (284—286).—On the colours of the rainbow (287—288).

VI.

PERSPECTIVE OF COLOUR AND AERIAL PERSPECTIVE

General rules (289—291).—An exceptional case (292).—An experiment (293).—The practice of the Prospettiva de' colori (294).—The rules of aerial perspective (295—297).—On the relative density of the atmosphere (298—299).—On the colour of the atmosphere (300—307).

VII.

ON THE PROPORTIONS AND ON THE MOVEMENTS OF THE HUMAN FIGURE

Preliminary observations (308. 309).—Proportions of the head and face (310—318).—Proportions of the head seen in front (319—321).—Proportions of the foot (322—323).—Relative proportions of the hand and foot