" In the mid-twentieth century it became the fashion in library architecture to design buildings as open-floored structures in which furniture, including bookcases, could be moved about at will. The Green/Snead Library of Congress bookstack that six decades earlier had been declared 'perfect' was now viewed as disadvantageously locking a stack arrangement into the configuration of its construction. In the new approach, reinforced concrete floors carry the loads of bookshelves, so that they can be arranged without regard for window placements. This apparently has the appeal of flexibility in the light of indecision, for planners need not look at the functional and aesthetic requirements of their space and its fittings with any degree of finality; they can always change the use of the space as whim and fashion and consultants dictate. It is unfortunate that such has become the case, for it reflects not only a lack of sensitivity to the historical roots of libraries and their use but also rejects the eminently sensible approach to using natural light as a means of energy conservation if nothing else. There is little more pleasing experience in a library than to stand before a bookshelf illuminated not by florescent lights but by the diffused light of the sun. Direct sunlight can be an annoyance and have a downright blinding effect, of course, but it has been the challenge to architects and engineers since Vitruvius to orient their structures--and the bookshelves in them--to minimize such problems in institutional stacks and in private libraries alike. Let us hope that not all future librarians lose their heliotropic instincts nor lose sight of the bookshelves for the forest of bookcases in which they rest. "

― Petroski, Henry