464 THE POPULAR SCIENCE MONTHLY. 



(" Transactions R. S. E.," vol. vii., 1813), and to that of the Petit Ber- 

 nard in Savoy (Favre, " Recherches," pi. x.) ; at 6 is a valley open at 

 one of its ends and almost closed at the other ; at e is a vault almost 

 straight, the prolongation of which is very level ; at g, h, and I are 

 vaults twisted and a little broken, while at i is a broken fold, the 

 curves of which are almost vertical. All these accidents of the ground 

 recall those which have been so often observed in the Jura, the Alps, 

 and the Appalachians. 



Fig. 2 represents a band of clay whose thickness was about 40 mm. 

 before compression and 65 after. We remark contortions similar to 

 those of the preceding figure, among others a vault «, very exactly 

 formed. At distances are seen vertical slices, on which the pressure 

 appears to have acted in a particularly energetic fashion, and which 

 may be called "zones de refoulement " ; the strata are there broken in 

 an exceptional manner, often separated from each other. One of these 

 vaults is replaced by a single vault on the opposite side of the band of 

 clay. 



Before compression, in the band of clay in Fig. 3, were seen the 

 two divisions which are seen there now — that in the right was 33 cm. 

 long and 25 mm. thick at a, and 35 at 5y the left division was 25 cm. 

 long and 65 mm. thick. A gentle slope united the part c to the part b. 

 After compression, the mean height of a h was 45 and that of c 75 mm. 

 All the layers were spread horizontally. 



" In this experiment I have sought to imitate the effect of crushing at 

 the limit of a mountain and a plain. The height of the mountain c has 

 been notably increased, the five or six upper layers have advanced on 

 the side of the plain ; they encroach on it. The plain has, however, 

 offered a resistance sufficiently great to cause the strata of the moun- 

 tain to be strongly inflected at the bottom. From this struggle be- 

 tween the plain and the mountain there resulted a cushion, <?, which is 

 the first hill at the foot of the height. It also resulted that the strata 

 of the plain assumed an appearance of depression at contact with the 

 mountain in consequence of the vault which is formed at h / they 

 plunge underneath the mountain. Tliis resembles what is often seen 

 in the Alps at the junction of the first calcareous chain and the hills 

 of ' moUasse ' ; in fact, the strata of the latter rock seem to plunge 

 under those of the neighboring heights. In consequence of the pres- 

 sure, there are formed several ranges of hills in the plain between h 

 and a. 



"In Fig. 4 the band of clay had, before compression, a thickness of 

 45 mm. ; after that the culminating point was more than 10 cm. I 

 have here sought to represent what must happen when terrestrial pres- 

 sure is exerted on horizontal strata still moist, deposited at the bottom 

 of a sea where are two mountains already solidified. For this purpose 

 I placed in the caoutchouc and under the clay two bare cylinders of 

 wood, a and J, of about 35 mm. radius, at 20 cm. from the ends of the 



