Camille Pissarro was mainly, in separate periods of his artistic development exclusively, an optical landscape painter. The attunement with nature which is afforded by the meeting of mountain and wood, water and reed, by the forms of trees and cliffs, the peculiarities of plant-life, and the movements of open country, he evidently did not feel and he cannot arouse. He was nothing, and he wanted to be nothing, but a priest and poet of light. When light fell, what objects it illumined and played on was a matter of such indifference to him that this landscape painter painted city scenes just as often as those of open country. Views of the Paris Boulevards, the Avenue de l’Opéra, the Seine seen from the bridges, the streets and squares of Rouen, occupy quite as large a space in his work as studies of the valley of the Marne and the hills of Southern England. Thanks to the good school from which he came, he never, like so many of his rivals, melts away into formlessness. He could not refrain from drawing distinctly. It was the movement of his bold and skilful hand that pervaded his will; but the sole hero of his pictures, to whom he gave his love and attention, was light. After he had outgrown the formulæ of the Corot type of landscape, he sought with persistent, hot endeavour to find a method that would qualify him to draw into his picture as much light as possible, as intense light as possible, even the whole sun. What he himself found failed to satisfy him. When Seurat, who suffered undoubtedly from eye troubles, came forward with his stippling, Pissarro at once took possession of the new manner, and became a stippler even unconsciously. Seurat, it is well known, taught that the painter, if he would give truth and force to colour, must not mix the shade on his palette and transfer it ready-made to the canvas, but must dissect it into its primary colours, which are known from the spectrum, and insert them in little dabs by one another, so as to leave it to the eye to put them together again on the retina. This optical proceeding professes to have been learnt by listening to nature, which also offers us only as single colours what we feel as a synthesis of colour. The theory is sheer nonsense. Nothing of the sort happens in nature. When we see green grass we do not see yellow and blue grass which our eye mixes into green, but we see a body proceed from the æther-vibrations of the undulations, which call forth on the retina a sensation of green; and to imitate this influence of the grass we have to employ only one colour stuff from which atmospheric vibrations of similar undulations proceed. Unscientific painters were, however, impressed by the sham-scientific jabber of Seurat, who tried, in his wonted manner, through a subsequently discovered theory, to convert a defect of sight into an advantage; and they applied themselves the more zealously to stippling as the innumerable specks really made bright a twinkling,