5o8 



WARREN J. MEAD 



the type used by Willis. A slight modification of the apparatus 

 of Favre was used by Hans Schardt/ who used various combina- 

 tions of plastic and brittle layers in his studies of the mechanics 



of mountain building. Still 

 another modification of Favre's 

 work was employed by Stanislas 

 Meunier,^ who studied and de- 

 scribed the fractures produced 

 in a layer of partially set plaster 

 on a contracting rubber sheet. 

 These three investigaters con- 

 fined their work to pure shorten- 

 ing and paid no attention to 

 stresses set up by tension, shear, 

 or warping. 



EXPERIMENTAL RESULTS 



Fractures produced by ten- 

 sion. — The apparatus (Fig. i) 

 consists of a frame with a rigidly 

 attached clamp at one end and 

 a movable clamp at the other 

 which may be moved toward or 

 away from the stationary clamp 

 by means of a long screw. To 

 develop tension fractures the 

 rubber sheet fastened at its edges 

 in the two clamps is tightly 

 stretched by means of the screw 

 and then coated with parafl&n 

 which is allowed to chill until 

 brittle. Tension is then applied 

 by further stretching of the rubber by means of the screw. A 

 typical set of tension fractures thus developed is shown in Figure i . 



^ Hans Schardt, "Etudes geologiques sur le Pays-d'Enhaut Vaudois." Troisieme 

 partie. A. Mecanisme des Dislocations. Chapitres xv-xvii. Planches VI-IX. 

 Bulletin de la Soc. Vandoise des Sciences naturelles, Vol. XX, No. 90, 1884. 



= Stanislas Meunier, La Geologic Experimeniale (Paris, 1899), p. 299. 



Fig. I. — Fractures produced by tension. 

 A heavy sheet of rubber is held between 

 two clamps and stretched by means of 

 the screw at the end. It is then coated 

 with paraffin which is allowed to chill 

 until brittle, after which the rubber is 

 further stretched by means of the screw, 

 developing tension cracks in the paraffin. 



