The Nots of Leonardo Da Vinci | Page 4

is mainly due to Mrs. R. C. Bell; while the rendering of several of the most puzzling and important passages, particularly in the second half of Vol. I, I owe to the indefatigable interest taken in this work by Mr. E. J. Poynter R. A. Finally I must express my thanks to Mr. Alfred Marks, of Long Ditton, who has most kindly assisted me throughout in the revision of the proof sheets.
The notes and dissertations on the texts on Architecture in Vol. II I owe to my friend Baron Henri de Geymuller, of Paris.
I may further mention with regard to the illustrations, that the negatives for the production of the "photo-gravures" by Monsieur Dujardin of Paris were all taken direct from the originals.
It is scarcely necessary to add that most of the drawings here reproduced in facsimile have never been published before. As I 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