transference of the outline of complex form, is therefore among the first, and even among the most important, means of educating his taste. A student who can fix with precision the cardinal points of a bird's wing, extended in any fixed position, and can then draw the curves of its individual plumes without measurable error, has advanced further towards a power of understanding the design of the great masters than he could by reading many volumes of criticism, or passing many months in undisciplined examination of works of art. 161. Again, it will be found that among amateur students there is almost universal deficiency in the power of expressing the roundness of a surface. They frequently draw with considerable dexterity and vigour, but never attain the slightest sense of those modulations in form which can only be expressed by gradations in shade. They leave sharp edges to their blots of colour, sharp angles in their contours of lines, and conceal from themselves their incapacity of completion by redundance of object. The assurance to such persons that no object could be rightly seen or drawn until the draughtsman had acquired the power of modulating surfaces by gradations wrought with some pointed instrument (whether pen, pencil, or chalk), would at once prevent much vain labour, and put an end to many errors of that worst kind which not only retard the student, but blind him; which prevent him from either attaining excellence himself, or understanding it in others. 162. It would be easy, did time admit it, to give instances of other principles which it is equally essential that the student should know, and certain that all painters of eminence would sanction; while even those respecting which some doubt may exist in their application to consummate practice, are yet perfectly determinable, so far as they are needed to guide a beginner. It may, for instance, be a question how far local colour should be treated as an element of chiaroscuro in a master's drawing of the human form. But there can be no question that it must be so treated in a boy's study of a tulip or a trout.