FIG. III. 



Longitudinal Section or Profile of Graduated Diggings (at 

 range D, in Fig. II.) Scale 40 feet to inch. 



EXPLANATIONS. 



a, a, Surface of ground, and level of highest part of graded 



roadway. 



m, m, Overlying earth, 6 feet thick. 

 n, n, Marl, 7 to 8 feet thick. 

 *, *, Green-sand earth, of unknown thickness. 

 a, o, r, Headway, descending 6 feet in 96, from surface of 



land a, to bottom of marl, r. 

 v } v, v, Successive perpendicular excavations, beginning at r, 



made after digging down to the inclined plane, o, r. 

 n, o, Marl either excavated like v, v, or subsequently by a re- 

 . versed direction of descending grade. 



