190 The American Geologist. September, 1904. 
and eight feet, six inches from buttress to buttress across the 
bottom of the canyon. From the surface of the water to the 
center of the arch above the hight is one hundred and ninety- 
seven feet, and over the arch at its highest point the solid mass 
of sandstone rises one hundred and twenty-five feet farther, 
to the level floor of the bridge. The causeway of the bridge, 
over which an army could march in columns of companies, as 
remarked by Mr. Dyar, is therefore three hundred and twenty- 
two feet above the stream. The floor of the bridge is one hun- 
dred and twenty-seven feet wide. Unfortunately, owing to the 
winding course of the canyon at this point and the consequent 
lack of perspective, the travelers were unable to obtain photo- 
graphic views conveying to the eye any adequate expression 
of the majesty of this bridge. Still Mr. Dyar succeeded in get- 
ting a sidewise view and the Century Magazine has reproduced 
it from a half-tone plate engraved by S. Davis. 
Three and a half miles above the Caroline bridge is the 
Augusta bridge, which is the most remarkable and majestic 
seen by the explorers. Of this a colored half-tone by Henry 
Fenn is given by the Century Magazine, occupying a full page, 
made from a photograph. This is described as magnificent, 
symmetrical and beautiful in its proportions, "so as to suggest 
that nature after completing the mighty structure of the Car- 
oline had trained herself for a finer and nobler form of archi- 
tecture." Here the cross-section of the canyon is three hun- 
dred and thirty-five feet and seven inches from wall to wall. 
The splendid arch is of sandstone sixty feet thick in the central 
part and forty feet wide. The opening beneath the arch is 
three hundred and fifty-seven feet in perpendicular hight. The 
lateral walls of the arch rise perpendicularlv nearly to the top 
of the bridge where they flare suddenlv outwards, giving the 
effect of an immense coping or cornice overhanging the main 
structure fifteen or twenty feet on each side, and extending 
with the greatest regularity and symmetry the whole length of 
the bridge. A large rounded butte at the edge of the canyon 
walls seems partly to obstruct the approach of the bridge at one 
end. 
"Here again," in the words of Mr. Dyar ."the curving walls 
of the canyon and the impossibihty of bringing the whole of 
the great structure into the narrow field ol the camera, except 
