(_γ_) The last kind of material exceptionally favourable to sculpture is stone, which possesses independently the external aspect of consistency and permanence. The Egyptians long before chiselled out their sculptured colossi with a labour that spared no pains from the hardest granite, syenite and basalt. _Marble_ is, however, most directly, as a material, in harmony with the aims of sculpture through its soft purity, whiteness, no less than by the absence of definite colour and the mildness of its sheen, and in particular possesses, by virtue of its granular texture and the soft interfusion of light which it carries, a great advantage over the chalk-like dead whiteness of gypsum, which is too bright, and easily kills with its glare the finer shadows. We find a distinct preference given to marble, only at a later epoch of the Greek school, that is during the period of Praxiteles and Scopas, who executed their most famous works in marble. Pheidias no doubt worked in marble, but for the most part only in the execution of head, hands, and feet. Myron and Polycletus mainly made use of bronze. Praxiteles and Scopas, on the other hand, appear to have sought to remove from sculpture that feature which is alien to its main principle, namely colour. No doubt it is undeniable that the beauty of the ideal of sculpture is capable of being embodied in bronze as in marble, with no diminution whatever of its purity. When, however, as was the case with Praxiteles and Scopas, art begins to approach the softer forms of grace and charm of figure, the marble asserts itself as the more congenial medium. For marble "encourages, by virtue of the transparency of its surface, a softness of outline, its gentle articulation[195] and mild conjunction; add to this that the tender and artificial elaboration of consummate work always appears more clearly on the soft whiteness of stone than on bronze, however noble it may be, which, in proportion as the transition of green is beautifully gradated, makes the lustres and the reflections all the more disturbing to the effect of repose[196]." For the same reason the careful attention, which at this period was paid to effects of light and shade, whose nuances and gradations are more clearly marked by marble than by bronze, was a further reason why stone should be preferred to metal. (_c_) In conclusion we ought to associate with the above more important kinds of material _precious stones_ and _glass._