354 AN EXPERIMENT IN MOUNTAIN-BUILDING. [Aug. I903, 



dip. Generally speaking, one might say that in mountains of 

 recent date, such as the Outer Himalayas, and even the Pyrenees, 

 contortions are not particularly in evidence, while the higher beds 

 are simply tilted, though sometimes at a very high angle. The 

 case is different in regard to the older ranges, such as those of 

 Scotland and Wales, which, being merely stumps of a mountain- 

 chain, exhibit chiefly the lower features. 



Mr. P. E. Kendall said that these experiments were very sug- 

 gestive, and he hoped that the Author would persevere with them. 

 He would like to see the vertical scale much reduced, so that the 

 number of folds might be increased ; it would, he thought, also be 

 desirable to make some provision for a diminution in the rigidity of 

 the materials forming the deeper-seated layers, so as to imitate 

 more closely the conditions prevailing in the lower portions of 

 earth-folds. He should like to see some experiments made with 

 contracting circles, which might perhaps throw light upon the 

 structure of curved mountain-chains. He thought that the North- 

 Western Highlands were far too complex in structure to constitute a 

 suitable study of mountain -folding, and would prefer to take as an 

 example some widespread deposit the folds of which could be traced 

 with precision over a large area. The Chalk of the South-East of 

 England appeared to show the phenomena of cross-folding with 

 great clearness, and there was a major wave or fold indicated by 

 the general dip to the south-east, and transverse ripples forming the 

 decussating folds of the Isle of Wight, the Portsdown anticline, 

 the great Wealden anticline, and others. 



Mr. Hudler welcomed the Authors suggestive researches, as 

 making a great advance on the work of earlier experimentalists in 

 the same held. By applying stresses in two directions at right 

 angles one to the other, it seemed possible to simulate the effects 

 resulting from the intersection of two rectangular sets of folds, such 

 as the Caledonian and the Charnian. He foresaw a wide range 

 of possibilities in these ingenious experiments, by varying the 

 magnitude of the pressure and the character of the media operated 

 on, and especially by varying the weight of the load under which 

 the substance was subjected to strain. 



Dr. Johnston-Lavis thought that some attempt to adhere to 

 ratios such as they existed in Nature would give more value to the 

 experiments. He would suggest that artificial loads should be 

 replaced by thicknesses of the material compressed, proportional to 

 the probable average thickness of the earth's crust. At the same 

 time, the compression should be proportional to what is known to 

 have taken place in the Alps or other mountain- chains. The 

 compression should be slow, and some artificial denuding rain, such 

 as water with plaster or clay, or weak hydrochloric acid with 

 cement, should be used to represent erosion simultaneous with 

 mountain-building. Compression should be tried, not only at right 

 angles as in the Author's experiments, but also with the axes of 

 compression at other angles, and moreover compression should be 

 applied simultaneously and also consecutively. This would, to 



