﻿Vol. 6 1.] AN EXPERIMENT IN MOUNTAIN-BUILDING, 345 



15. An Experiment in Mountain-Building : Part II. By the 

 Right Hon. the Lord Avebury, P.C., F.R.S., P.S.A., For. Sec. ' 

 R.A., F.G.S. (Read March 22nd, 1905.) 



In ] 903 the Society did me the honour of publishing a short paper 

 on this subject. 1 I may, perhaps, just repeat that Sir James Hall 

 many years ago, and others since, have 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, Daubree, Willis, 

 Ruskin, and others. 



In these investigations the compression was from two sides only. 

 If, however, folded mountains are caused by contraction due to the 

 cooling of the earth, the compression must take place from 

 all sides. 



With the view of illustrating this, I requested the Cambridge 

 Philosophical Instrument Company to make for me an apparatus 

 consisting of four square beams of wood, resting upon 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 this square central space 1 placed layers o^ cloth, baize, oil- 

 cloth, cement, etc., separated by laj^ers of sand. The machine was 

 then set in motion, and compressed so that the central space was 

 reduced from 24 inches square to 22. 



Since last year I have made other experiments, changing the 

 arrangement in various ways. The results differ in details in 

 almost every case, the initial movements being probably determined 

 by slight differences in the texture of the substances employed. 



As a typical case I may cite fig. 1 (p. 348), representing a piece 

 of compressed baize. It will be observed that there are two main 

 folds, which cross at a right angle ; that the elevation is greatest 

 where the two folds meet ; and that, while one fold is continuous, 

 the other and lower one is shifted somewhat to one side, for a 

 reason to which I will presently refer. Fig. 2 (p. 348) represents 

 another specimen also showing the cross-ridges. Fig. 3 (p. 349; 

 exhibits similar features, but the hills and valleys are more 

 complex, and therefore more like those in Nature. Secondary cross- 

 folding is well shown, and there is the same lateral shifting of one 

 arm of the cross. The elevation is shown by fig. 4 (p. 349) which 

 gives a lateral view. 



Quart. Journ. Geol. Soc. vol. lix, pp. 348-55 & figs. 



