to the rendering of the physical phenomenon of a concave space more or less immersed in shadow, no one was more skilful than Dou. To give depth and quality to the obscurity of the distance and especially of the ceiling, he would hang a chandelier or lantern in the middle distance and catch the light upon it. Similarly, he would place some objects in the foreground to bring the latter forward, and then between these two foci of secondary light concentrate or scatter the main group of figures in highest illumination. The two finest examples of his skill in thus building up a composition of values of light are _The Young Mother_, in the gallery of The Hague, and _The Dropsical Woman_ of the Louvre. The former, because of its charming sentiment, is Dou’s most popular picture; but the other, in consequence of the superior simplicity and concentration of its composition, the comparative breadth of its treatment and fuller richness of color and quality of chiaroscuro, is without much doubt his masterpiece. However, another example which approaches it very closely is _A Lady at her Toilet_, in the Munich Gallery. Dou’s interest in chiaroscuro led him to experiment with so-called night-pieces, where the gloom of the interior is illuminated by a candle that makes a central spot of brilliance, fitfully reflected in a partially diffused glow. Such are _An Old Woman who has Lost her Thread_ and the _Young Man and Girl in a Cellar_, both in the Dresden Gallery; while the most elaborate and famous example is _The Night School_ of the Rijks Museum, somewhat damaged by time, in which there are five separate points of varying degrees of illumination.