FORMATION OF MOUNTAIN& ;>1 



In Fig. 2 the clay was 40 millimetres thick broken and their ends often separated. One of 



originally, and 65 after compression. At a is these vaults is replaced on the opposite hi<|.- \,\ 



a very perfect vault. At ft, c, d, and e are a single fault. M. Favre calls these places of 



spots whore tin- pressure found the least re- extreme pressure zontt de rtfouhment. 

 sistance, and where the strata were violently In Fig. 3 an experiment with a band of va- 



Fio. 



riant thickness is represented. The division a 

 was 33 centimetres long and 25 millimetres 

 thick ; b was 25 centimetres long and 65 milli- 

 metres thick ; a gentle slope 35 millimetres 

 thick at b connected them. After compression 

 the mean thickness of a and b was 45 and that 

 of e 75 millimetres. Jn this experiment he 

 sought to obtain the effect of compression at a 



point where a mountain meets a plain. The 

 height of the mountain c has been increased ; 

 the live or six upper layers have encroached 

 upon the plain ; but the resistance of the plain 

 has been sufficient to cause the strata of the 

 mountain to be strongly inflected. The first 

 hill rf, at the foot of the mountain, is the result 

 of the struggle between the mountain and the 



Fio. 3. 



plain ; ns also is the vault 6, the elevation of 

 which has caused the strata of the plain to be 

 deflected and depressed at contact with the 

 mountain. Such a phenomenon as the depres- 

 sion of the strata of a lower elevation under the 

 foot of a mountain is often observed in the 

 Alps at the junction of the first calcareous 

 chain and the hills of the molasse. 



In Fig. 4 the thickness of the clay band was 



45 millimetres, and nfter compression the high- 

 est elevation was over 100. The object of the 

 experiment was to reproduce the eftect of lat- 

 eral pressure on moist strata at the bottom of 

 the ocean, near two solidified mountain masses. 

 Two semi - cylinders of wood were inserted 

 nnder the clay at equal distances from the ex- 

 tremities nnd the same distance from each 

 other. After pressure a valley c was formed 



