58 
Small balustrade of reeds^ which extends along' 
the road leading to the upper bridge. 
Sixty feet below this natural bridge is another^ 
to which we are led by a narrow pathway^ which 
descends upon the brink of the crevice. Three 
enormous masses of rock are fallen so as to 
support each other. That in the middle forms 
the key of the arch ; an accident which might 
have given the natives the idea of arches in 
masonry^ unknown to the people of the new 
world, as well as to the ancient inhabitants of 
Egypt. I shall not decide the question whether 
these masses of rock have been projected from a 
great distance, or whether they are the frag- 
ments of an arch broken on the spot, but origi- 
nally like the upper natural bridge. The latter 
conjecture seems probable, from a similar event 
which happened to the Coliseum at Rome, 
where, in a half ruined wall, several stones were 
stopped in their descent, because in falling 
they accidentally formed an arch. 
In the middle of the second bridge of Ico- 
nonzo is a hollow of more than eight metres 
square, through which the bottom of the abyss is 
perceived. We there made our experiments on 
the fall of bodies. The torrent seems to flow 
through a dark cavern, whence arises a lugubri- 
ous noise, caused by the numberless flights of 
nocturnal birds that haunt the crevice, and 
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