National Geographic : 1949 Jul
40 The National Geographic Magazine S that the dynamic spiral S,. is a fundamental pat S: " : tern of growth. *." , To produce a spiral, S"' . . ' :...".. ' three conditions must exist. First, growth Must pursue a continu S" ous course and not be erratic or backtrack. SSecond, growth must proceed freely and without outside inter ference. Third, it must operate as a sequence with a growing tip or growing lip, or at least produce new growth following after older parts. St The growth of shells Se clearly pursues a con i tinuous course. Their lines are not zigzag or jagged. They often have spines, knobs, and r ridges, but these are protuberances on the basic spiral. Finally, each shell has a lip e u tthat generates the shell so that it is built with °q a sequence of incre ments, those near the lip being younger than those near the apex. Because they possess this inherent spiraling T. c. noughley ability, combined with Scarlet Tentacles Fringe the Moving Valves of the Lima lima the permanence of their Propelling itself by opening and closing its shell, this mollusk develops good structure when built, speed through the waters of Australia's Great Barrier Reef. It and the pecten, or shells are the most scallop, are the only bivalves capable of swimming during their adult stage. The vivid examples in all tentacles cannot be drawn inside when the shell is closed. Nature of this principle of growth. flowing back toward the deep, until finally The stirring quality of the design lies in its the oncoming wave has no reserves left for action. It is not inert. Even though the increasing its magnitude and must topple. spiral of a shell is physically stationary, it But it does not crash formlessly. At that has a point of origin, called a nucleus or proto moment, when it is undermined by the in- conch, from which it springs whirling toward creasing force of the undertow, the wave an infinitely greater magnitude. bends forward. In cross section it forms momentarily the pattern of a logarithmic Snail and Scallop Inspire Architects spiral, with the crest curving in and under That this pattern of action can be impressed to place its apex at the center of gravity. in hard material so as to endow what is fixed This figure perpetually repeated by waves as and immovable with a quality of movement they mount the beach forms the identical is one of the characteristics of the spiral. curve that you find in the cone, conch, cowry, You may say that architects and sculptors snail, and nautilus shells, borrow from the snail and the scallop their Here we are confronted not with an imagi- dynamic curves to animate intractable marble native idea but with a thrilling fact of life: with fluidity and living beauty.