BELT OF CEMENTATION DEFINED. 563 



that metasomatism, injection, consolidation, and fracturing are important, 

 and some of them scarcely less so than cementation. The geological 

 evidence clearly shows that no sooner are openings produced in this belt, or 

 rocks containing openings transferred to this belt, than deposition of material 

 in the openings begins and continues until the separated parts are firmly 

 cemented. Since cementation is only one of the processes which occur, the 

 name "belt of cementation" is less fortunate than the name for the belt at 

 the surface, the belt of weathering, for weathering is a general terra properly 

 covering many, if not all, the processes which take place within the belt 

 to which it is applied; but as there is no comprehensive term available, 

 the name "belt of cementation" has been chosen, with hesitation, on the 

 basis of naming the belt by the most obvious and characteristic of the 

 processes which take place within it. In many respects the name "belt 

 of induration" would be a good one, since under quiescent conditions the 

 rocks are hardened by the various processes at work. The process of 

 cementation also hardens or indurates many of the rocks. This name 

 would cover both of the chemical processes, cementation and metasomatism, 

 and the igneous process of injection, but it is contradicted by the' mechanical 

 process of fracturing. It is more comprehensive than the name "belt of 

 cementation," but is inaccurate in that induration is not always characteristic 

 of the belt. The name "belt of saturation" well covers the fact that the 

 openings are commonly filled by water solutions, but this is also true of the 

 exceedingly minute openings of the zone of anamorphism. Furthermore, 

 the term "belt of saturation" would be likely to be understood to imply that 

 the solutions in the belt are always saturated with the compounds with which 

 they are in contact, and this is far from the truth. Certainly the term "belt 

 of cementation" is the one which seizes as distinctive the most characteristic 

 and obvious feature, evidences of which are seen in the field in all 

 major openings, and which are equalty evident through the microscope in 

 minor openings. 



The geological evidence that cementation is the universal law for the 

 part of the zone of fracture in which the rocks are usually saturated with 

 water seems to be conclusive. In mining operations the world over it has 

 been found that there is a tightening of the ground when the level of ground 

 water is reached. Above that level the rocks are likely, to be open and 

 porous, giving- the freest circulation to the waters of the belt of weathering'; 



