An Experiment in Mountain-Building

Abstract

Many years ago Sir James Hall illustrated the formation of folded mountains by placing layers of cloth under a weight, and then compressing two of the sides so that the cloth was thrown into folds. Since then, other and more complete experiments of the same kind have been made by Favre, Cadell, Daubrée, Willis, and Ruskin. In these experiments the compression was from two sides. If, however, folded mountains are caused by compression due to the contraction of the earth, the compression must take place in two directions at right angles one to the other. With the view of illustrating this I consulted Mr. Horace Darwin, and he constructed for me an apparatus consisting of four square beams of wood, resting on a floor, which by means of screws could be moved nearer to, or farther from, each other. The beams left between them a space 2 feet across and 9 inches in depth. In the square central space I placed some pieces of carpet-baize and layers of sand, each about 1½ inches deep. About an inch above the upper layer of sand I placed a piece of plate-glass and some weights. The machine was then set in motion, causing the beams of wood to approach one another. The sand rose in the centre, until it reached the glass, when it was flattened out. On removing the upper layer of sand, the top-piece of cloth was as shown in fig. 1 (p. 350), which is a photographic reproduction of a