STRATIFICATION. 



95 



having been solidified against either wall of the crack until the 

 two sides met at the centre and became more or less perfectly 



Fig. 64. 



Fig. 65. 



united. Specimens of rock thus honeycombed are sometimes 

 called septaria (from septum, partition) ; but the term is little used 

 in science. 



Fig. 66. 



(5.) Rain-prints (fig. 66). — Eounded pits or depressions, made by 

 drops of rain on a surface of clay or half-dry mud. On a reversed 

 layer the impressions appear raised instead of depressed, being 

 casts made in* the pits which the rain had formed. 



(6.) There are also markings which are attributed to the 

 flowing of thick mud. There are others, produced apparently by 

 small eddyings of water in clay or mud which work out concavities 

 that afterwards become filled with clay and look as if made by 

 the valves of shells. 



102. (2. ) Kinds of structure not properly a result of deposition, 

 and mostly of subsequent origin.— The kinds of structure here 



