Tlte Origin of the Bridge. 61 



The passage gradually enlarged until all the waters of the creek 

 passed through it and the bridge began its existence. What the 

 length of this subterranean passage was is a matter of conjecture ; 

 it ma}^ have been one hundred or several hundred feet. All of 

 its roof has disappeared except the narrow span of the bridge, 

 and the abutting walls have been worn back b}^ erosion until 

 the gorge or canyon is much wider than at the bridge. The 

 bridge is massive and strong, and the supporting walls rise in 

 solid, almost unbroken, mural faces to the spring of the arch, 

 nearly 200 feet above the bed of C!edar creek, as clearly shown 

 in the accompanying plate (which is reproduced mechanically 

 from a photograph taken by the author). 



The position of the massive layers of limestone at the center 

 of the low synclinal gives them power to resist erosion to a much 

 greater extent than the upturned strata above and below the 

 bridge. The condition of the latter favors rapid disintegration, 

 and the result is shown in the widening of the gorge. The re- 

 treating lower level of the stream is now at Lace falls, nearly 

 a mile above the bridge. The gorge below the bridge widens 

 out more rapidly, owing partly to the erosion caused by a small 

 brook that enters from the north, partly to the greater period 

 of erosion to which it has been subjected. 



On the northern side, opposite Pulpit rock, about twenty feet 

 west of the public road, the summit of the bridge is 2o6 feet 

 above the water, and this part of the arch has a thickness of 44 

 feet and a span of from 45 to 60 feet. The western edge is about 

 ten feet higher, and the eastern edge about ten feet lower than 

 the central point. 



The massive layers of limestone forming the bridge are grad- 

 ually wearing away on the outer edges from the action of water 

 and frost. If water-breaks were arranged so that the water could 

 not flow in upon the bridge and about it from the southwestern 

 side, and if a shed with water-tight roof were built over the arch, 

 disintegration and destruction would be indefinitely postponed. 

 As it is, itrwill be many centuries before the natural processes of 

 erosion now at work upon and within the arch will completely 

 break it clown. 



Since the preceding was written, an article has appeared in the 

 Neio York Tribune of May 15, 1893, in which an account is given 

 of the discovery of a passage in the limestones near Natural 



