In architecture, as in painting, the visual elements are adapted to one or the other of the two chief ways of seeing. Either the surfaces are seen as wholes primarily and the details in subordination; or else the parts stand out clear and distinct, and the whole is their summation. The former is always the case when the surfaces are left plain with few divisions, or, if the surfaces are divided, when the lines intersect and intermingle, as is exemplified in late Renaissance or Baroque work, where the walls are covered with lavish ornament, the enframement of windows is broken by moldings and sculpture which carry into the surrounding spaces, and where, instead of embracing one story, the "orders" comprise the entire height of the building. The second possibility is well illustrated by the early classical Renaissance, where the surface of each story, sharply separated from the others by the line of the frieze, is divided regularly by arches or columns, each window clearly enframed, and every sculptured ornament provided with a niche. There is, however, this fundamental difference between architectural and pictorial lines: the latter are usually pure kinematical lines, lines of free and un-resisted movement, while the former are usually dynamical, lines of force which move against the resistance of mass. In a picture objects are volatilized into light and have lost all weight; but in architecture, since they are present in reality and not in mere semblance, their weight is retained. A Greek column, for example, not only moves upward, but also against the superincumbent load of the entablature which it carries. The difference between the two arts can be appreciated by comparing the picture of a building with the building itself; in the former, despite the fact that we know how heavy the dome or pediment is, and how strong therefore the piers or columns that support it, we hardly feel them as heavy or strong at all--the forces and masses have been transformed into abstract lines and shapes. Sometimes, however, architectural lines and surfaces remain purely kinematical; on the inside of our rooms, for example, when the surfaces are smooth, and especially when they are decorated, we often feel no tension of conflicting forces, but only a quiet play of movements; it is as if the walls had been changed into the paper or paint that covers them. The vividness of the expression of mechanical forces in architecture depends, moreover, upon the kind of materials employed; it is greater in marble than in wood, and less in our modern constructions of steel and glass, where the piers move in single vertical lines from the bottom to the top of the building, than in the old forms, where the upper part of the building is frankly carried by the lower.