text:  The former chiefly valuable when he quotes--for then as Reynolds observed "he speaks the language of an artist:" as in his account of the glazing method of Apelles; the manner in which Protogenes embodied his colours; and the term of art _circumlitio_ by which Nicias gave "the line of correctness to the models of Praxiteles;" the foreshortening the bull by Pausias and throwing his shade on the crowd--showing a forcible chiaroscuro