28 WALTER H. BUCHER 
when a rivet yields perpendicularly to its axis, say, in a bursting 
boiler.’ 
A clear and simple illustration of the form in which this method 
of fracturing finds its most important expression in the earth’s 
structure, is offered by Figure 21, which represents the section of 
one of the folds of the Jura Mountains at the boundary of France 
and Switzerland, as brought out by Buxtort’s detailed investiga- 
tions.2 The brittle layer of the Rauracien, which stood up verti- 
cally in the process of folding, comparable to the rivet on a boiler 
plate mentioned above, gave way to the pressure of the swelling 
plastic Oxford clays, counteracted below by the level part of the 
north limb of the anticline. 
Sorsativeeg, 
CEPA AS 
5 AB ger v, 190g 
Fic. 21—Cross-section of a fold of the Jura Mountains at the border of France and 
Switzerland (at the ‘‘Clos du Doubs’’). 1-3, Triassic, 4. Liassic, 5. Dogger, 6. Oxford 
clays, 7- Rauracian, Sequanian, 9. Kimmeridgian, to. Landslide. (A. Buxtorf, 1909.) 
The writer is inclined to believe, following the lead of Dr. 
Buxtorf,’ that in the case of most, if not all “low-angle faults,” or as 
Suess called them, ‘“‘listric planes,” the rotational stress resulted 
from the flowage of materials inside the fold, whether it be, on a 
smaller scale, confined to individual normally plastic layers, or, 
on the largest scale, to the forced flowage of the rocks forming the 
cores of rising mountains. 
This, however, leads us beyond the scope of this paper. The 
necessary setting for a broader discussion of this important prob- 
lem will be given in a paper now in preparation.° 
1G. F. Becker, ‘‘Finite Homogeneous Strain, Flow and Rupture of Rocks,” 
Bull. Geol. Soc., Vol. TV (1893), p. 24. 
2 A. Buxtorf, ‘“‘Uber den Gebirgsbau des Clos du Doubs und der Vellerat-Kette 
im Berner Jura,’’ Ber. Vers. Oberrhein. Geol. Ver. (1909), p. 76, Fig. 1. 
3 Ibid., p. 86. 
4E. Suess, The Face of the Earth (transl. by Sollas, H. B.), Vol. IV (1909), p. 536. 
5 Parts of which were presented before the Geological Society of America at the 
Chicago meeting 1920 under the title ““The Probable Cause of the Localization. of 
the Major Geosynclines.”’ 
