426 TROPICAL NATURE VII 
ing three miles in length, and containing not less than three 
million cubic feet of earth. This area incloses numerous 
sacrificial mounds and symmetrical earthworks, in which 
many interesting relics and works of art have been found. 
The second class—the sacred inclosures—may be compared 
for extent and arrangement with Avebury or Karnak, but 
are in some respects even more remarkable. One of these 
at Newark, Ohio, covers an area of several miles, with its 
connected groups of circles, octagons, squares, ellipses, and 
avenues on a grand scale, and formed by embankments from 
twenty to thirty feet in height. Other similar works occur 
in different parts of Ohio; and by accurate survey it is found, 
not only that the circles are true, though some of them are 
one-third of a mile in diameter, but that other figures are 
truly square, each side being over 1000 feet long; and, what 
is still more important, the dimensions of some of these 
geometrical figures, in different parts of the country and 
seventy miles apart, are identical. Now this proves the use, 
by the builders of these works, of some standard measures of 
length ; while the accuracy of the squares, circles, and, in a 
less degree, of the octagonal figures, shows a considerable 
knowledge of rudimentary geometry and some means of 
measuring angles. The difficulty of drawing such figures on 
a large scale is much greater than any one would imagine 
who has not tried it; and the accuracy of these is far beyond 
what is necessary to satisfy the eye. We must, therefore, 
impute to the builders the wish to make these figures as 
accurate as possible, and this wish is a greater proof of 
habitual skill and intellectual advancement than even the 
ability to draw such figures. If, then, we take into account 
this ability and this love of geometric truth, and further 
consider the dense population and civil organisation implied 
by the construction of such extensive systematic works, we 
must allow that these ancient people had reached the earlier 
stages of a civilisation of which no traces existed among the 
savage tribes who alone occupied the country when first 
visited by Europeans. 
The animal mounds are of comparatively less importance 
for our present purpose, as they imply a somewhat lower 
grade of advancement; but the sepulchral and_ sacrificial 
