104 THE FOKMS OF WATER IN 



state of strain ; it breaks and forms a crevasse. Each 

 fresh portion of the neve as it passes the brow is 

 similarly broken, and thus a succession of crevasses is 

 sent down the fall. Between every two chasms is a 

 great transverse ridge. Through local strains upon the 

 fall those ridges are also frequently broken across, 

 towers of ice— seracs — being the result. Down the fall 

 both ridges and seracs are borne, the dislocation being 

 augmented during the descent. 



264. What must occur at the foot of the fall? Here 

 the slope suddenly lessens in steepness. It is plain that 

 the crevasses must not only cease to open here, but that 

 they must in whole or in part close up. At the summit 

 of the fall, the bending was such as to make the surface 

 convex ; at the bottom of the fall the bending renders 

 the surface concave. In the one case we have strain, in 

 the other pressure. In the one case, therefore, we have 

 the opening, and in the other the closing of crevasses. 

 This reasoning corresponds exactly with the facts of 

 observation. 



265. Lay bare your arm and stretch it straight. 

 Make two ink dots half an inch or an inch apart, 

 exactly opposite the elbow. Bend your arm, the dots 

 approach each other, and are finally brought together. 

 Let the two dots represent the two sides of a crevasse 

 at the bottom of an ice-fall ; the bending of the arm 

 resembles the bending of the ice, and the closing up o/ 

 hhe dots resembles the closing r>f the fissures. 



