THE FORMATION OF MOUNTAINS. 



461 



Fig. 1. 



which he wished to oompress to rest on a body which itself could not be 

 compressed, while I placed the layer of clay employed in these experi- 

 ments on a sheet of caoutchouc, tightly stretched, to which I made it 

 adhere as much as possible ; then I allowed the caoutchouc to resume 

 its original dimensions. By its contraction the caoutchouc would act 

 equally on all points of the lower part of the clay, and more or less on 

 all the mass in the direction of the lateral thrust. 2. Hall compressed, 

 by a weight, the upper surface of the body which he wished to wrinkle, 

 which prevented any deformation, while by leaving that surface free, 

 I have "seen, during the experiment, forms appear similar to those of 

 hills and mountains which may be observed in various cotmtries. . . . 



Ki(i. 



"The arrangement of the apparatus is very simple. A sheet of 

 India rubber 16 mm. in thickness, 12 cm. broad, and 40 cm. long, was 

 stretched, in most of the experiments, to a length of 60 cm. This was 



