CONSTRUCTION OF THE EARTH. 141 



face, and has over it various strata of sandstone and 

 shale, 1, 2, 3, 4, and 5. In the divisions B and D there 

 is only the stratum 5 above the coal, which is only 200 

 feet from the surface, while in the division C the coal 

 lies 700 feet deep. Now, notwithstanding this displace- 

 ment of the strata, there is* no appearance of the up- 

 heavals on the surface of the coal-field, but that is level. 

 If the material all remained on the spot, we should have 

 an uneven surface, and at O O there would be an eleva- 

 tion of TOO feet, for that is the amount of uplift in the 

 strata at that part of the field. The inference is that all 

 this great mass of material, indicated by the dotted line, 

 was removed by denudation. Near Chambersburg, Pa., 

 there is a fault 20 miles in length, and the depth of the 

 dislocation is 20,000 feet, and yet a man can stand with 

 one foot on one side of this fracture and the other foot 

 on the other side. "What has become, then, of this im- 

 mense mass of material 20,000 feet in height ? " It must 

 have been swept," says Mr. Lesley, who gives the ac- 

 count, "into the Atlantic by the denuding flood." If 

 this had not been done there would have stood there a 

 bold precipice nearly four miles in height and twenty 

 miles in length. Long ages must have been required 

 for water to effect such a denudation. The proximity 

 in which such a fault places rocks of epochs far distant 

 from each other bring to the mind grand and over- 

 whelming conceptions of the vast periods of time which 

 have elapsed in the building up of the world. On the 

 one side of that crevice you step on limestone that was 

 made long ages before the slaty rock that you step on 

 upon the other, and by accident there are lodged in that 

 crevice fragments of a rock of still another epoch be- 

 tween the epochs of those on either side. 



226. How Mountains were Made. You are now pre- 

 pared to see how mountains were built up. They were 

 not all constructed and shaped in the same way, but 

 there is much variety. I will indicate some of the prin- 



