12 GEOLOGY OF OHIO. 



embankment, by far the greater portion of it is earth, obtained from a 

 ditch along the inner foot of the wall. Perhaps careful measurements 

 would show otherwise, but there appears to be more earth heaped up 

 than could be replaced in the trench; if so, the surplus was gathered up 

 close by. The gateways are comparatively narrow and few in number; 

 from the situation of some of them, it would seem they were little used; 

 others open toward the easiest approaches. The walls are massive; if 

 their cubic contents should be divided by their total length, it is probable 

 the quotient, representing the amount of earth in any given unit of length, 

 would exceed that similarly obtained in any other structure in the state. 

 It is doubtful whether nearly all of those described in the first section 

 would not suffer by the comparison. Unless the embankment has been 

 much reduced in height by atmospheric agencies since its abandonment, 

 with a corresponding increase in breadth and diminution of slope, some 

 of the difficulties in the way of ascribing a military purpose to the large 

 enclosures of the level lands apply with the same force here. Under 

 present conditions there would be small choice in position on either side 

 of the wall at equal distances from it. Possibly there was some additional 

 method of defense or protection of which no trace now remains. 



Surpassing all other hill fortifications in magnitude as well as in 

 systematic design is Fort Ancient in Warren county. Built on a spur 

 almost detached by deep hollows from the plateau, somewhat more than 

 two hundred feet above the level of the Little Miami River, which flows 

 close below, its walls follow accurately the tortuous course due to the 

 scores of ravines which give a crenulated outline to the brow of the hill. 

 The numerous openings, almost without exception, lead out on narrow 

 points overlooking ravines on either side, and commanding from two or 

 three directions every possible avenue of approach. The thought at once 

 suggests itself they were completed by bastions closing in the limited 

 outside space, usually only a few square yards in extent. Where facing 

 a slope easily defended, the embankment is quite low; parts most liable 

 to attack, or commanding important points, are greatly strengthened. 

 The portion crossing the level is nearly twenty feet in height; the ditch 

 here is on the outside; elsewhere it is within. 



Few modern fortifications equal Fort Ancient as a defensive work. 

 With ordinary care surprise would be impossible. Omitting the few rods 

 of level ground at the east, the walls can be reached only by ascending a 

 steep slope, in plain view of any who maybe on the watch; while from 

 the peculiar conformation of the ground nearly every portion of the hill- 

 sides may be placed under cross-fire. Properly garrisoned, the place 

 would withstand a prolonged siege by a well-equipped army; with primi- 

 tive methods of warfare it would be impregnable. 



Shown in Plate VIII. 



A perplexing element in the stud}'' of all these forts is the question of 

 water supply. No springs exist w T ithin them, as they are above drainage ; 



