NATURAL BRIDGES BY STREAM EROSION 



319 



Since the writer has not visited this region, and consequently has not 

 made a study of the bridges on the ground, his conclusions are necessarily 

 based on the observations of others. In the case of the Caroline bridge, 

 the mode of formation seems to be the same as that of the foregoing 

 bridges, judging from the rough sketches of the region submitted to the 

 writer, one of which is produced here (figure 3). It is possible that in 

 this case the perforation of the neck of the meander was hastened by the 

 work of Armstrong Creek. 



The Edwin bridge (plate 19, figure 1) offers a variation from the type 

 already discussed, as will be seen by the accompanying diagram (figure 

 4).* The neck of land perforated was not a meander, but a narrow strip 

 of land at the juncture of two streams. It appears from the evidence 



I 



Figure 4. — Diagram showing Origin of the Edwin Bridge, Utah 

 Modified from diagram by H, L. A. Culmer in a letter to the author 



that the perforation was made by the lateral cutting of the former Edwin 

 Creek by Armstrong Creek or by a combined action of the two. 



The information concerning the Augusta (plate 19, figure 2) and 

 Nonnezoshi bridges is very incomplete, but from what could be gathered 

 from those who had visited them, and also from the fact that the bridges 

 are composed of the same material as the Edwin and Caroline bridges, 

 and are situated in a region of incised meanders, it seems probable that 

 they were formed in the same manner as the Edwin and Caroline bridges. 



< These diagrams are from rough sketches made by Culmer to show In general the 

 courses of the present and former streams, and are not drawn to scale. 



W. W. Dyar : Century Magazine, vol. 68, August, 1904. 



H. L. A. Culmer : Technical World, September, 1908, pp. 49-55. 



Letters to the writer from Mr. H. L. A. Culmer, 1907. 



Other descriptions have appeared In the Sunday supplements of several daily papers, 

 the National Geographic Magazine, Scientific American, Collier's. 



