CONCERNING THE PROCESS OF THRUST FAULTING 427 



appears to yield first by flexure and then by rupture, and that 

 many experiments performed by Wilb's, Cadell, Chamberhn, 

 Miller, and others, technically speaking, are experiments with 

 long columns rather than with short blocks, because the members 

 flexed before rupturing. More strictly speaking, most of these 

 experiments on deformable materials fall under the mechanical 

 analyses of neither short blocks nor of long columns because of 

 the nature of the material, but they seem to accord the more 

 closely to long-column analysis. If an adequate amount of experi- 

 mental and analytical work had been done upon the deformation of 

 sheets,'^ the writer would have used only the sheet as an illustra- 

 tion of earth deformation. 



THE RUPTURE OF SHEETS AND LONG COLUMNS 



Experiments with sheets under rotational stress. — In hope of 

 learning more about the deformation and rupture of sheets the 

 writer performed a few simple experiments upon easily controlled 

 members. T. Mellard Reade has done sufficient work with straight 

 and circumferential compression upon sheets, but the effects of a 

 vertically unequally distributed stress heretofore have not been 

 tried. Reade^ draws conclusions from the deformation of the lead 

 lining of a scullery sink. The writer used a common bench vise 

 to deform and rupture plates of soap and paraflin. Of the two, 

 soap was the more satisfactory. In order to secure an unequally 

 distributed stress a wedge was inserted, large end upward, between 

 the end of the member and the face of the vise. This resulted in 

 bringing greater pressure to bear near the top than near the bottom 

 of the plate. If the plate had been quite free to bend it would 

 have bent downward; however, that would not have illustrated 

 the deformation of rock strata, and the member was therefore 

 stiffened enough by slight pressure from below to make it bend 

 upward. After the bending of the soap, rupture started from the 

 bottom at a low angle from a point nearly equidistant from each 



^ The only work known to the writer which appears to have a bearing on the 

 subject is "Tests of Reinforced Concrete Flat Slab Structures," by Arthur N. Talbot 

 and Willis A. Slater, University of Illinois Bull., Vol. XIII, No. 22, 1916. 



^ T. Mellard Reade, The Origin of Mountain Ranges (1886), pp. 15-16, and 

 Plate VI, p. 28. 



