but to judge of his real powers and peculiar ideals, his system of faint and clear coloring, whether in fresco, tempera or oil; his somewhat slender and pallid types, not without something that reminds us of northern art in their teutonic sentimentality as well as their fidelity of portraiture; the conflict of his instinctive love of placidity and calm with a somewhat forced and borrowed energy in figures where energy is demanded, his conservatism in the matter of storied and minutely diversified backgrounds to judge of these qualities of the master as they are, it is necessary to study first the great series of his frescoes and altar-pieces at the certosa, and next those remains of later frescoes and altarpieces at milan and lodi, in which we find the influence of leonardo and of the new time mingling with, but not expelling, his first predilections.