BENEFICIAL EFFECTS OF UNDULATIONS. 405 



ductive qualities, and variously adapted to the habitation of 

 Man, and the inferior tribes of terrestrial animals. 



In our last Chapter we considered the advantages of the 

 disposition of the Carboniferous strata in the form of Basins. 

 It remains to examine the farther advantages that arise from 

 other disturbances of these strata by Faults or Fractures, 

 which are of great importance in facilitating the operations 

 of Coal mines ; and to extend our inquiry into the more ge- 

 neral effect of similar Dislocations of other strata, in pro- 

 ducing convenient receptacles for many valuable Metallic 

 ores, and in regulating the supplies of Water from the inte- 

 rior of the earth, through the medium of Springs. 



I have elsewhere observed* that the occurrence of Faults 

 and the hicUned position in which the strata composing the 

 Coal measures are usually laid out, are facts of the highest 

 importance, as connected with the accessibility of their mi- 

 neral contents. From their inclined position, the thin strata 

 of Coal are worked with greater facility than if they had 

 been horizontal ; but as this inclination has a tendency to 

 plunge their lower extremities to a depth that would be in- 

 accessible, a series of Faults, or Traps, is interposed, by 

 which the component portions of the same formation are 

 arranged in a series of successive tables, or stages, rising 

 one behind another, and elevated continually upwards to- 

 wards the surface, from their lowest points of depression. 

 (See PI. 65. Fig. 3. and PI. 66. Fig. 2.) A similar effect is 

 often produced by Undulations or contortions of the strata, 

 which give the united advantage of inclined position and of 

 keeping them near the surface. The Basin-shaped struc- 

 ture which so frequently occurs in coal fields, has a ten- 

 dency to produce the same beneficial consequences. (See 

 PI. 65 Figs. 1. 2. 3.) 



But a still more important benefit results from' the occur- 

 rence of Faults or Fractures,-f without which the contents of 



* Inaugural Lecture, Oxford, 1819. 



t " Faults," says Mr. Conybeare, " consist of fissures traversing the 

 strata, extending often for several miles, and penetrating to a depth, in 



