440 V. H. BARNETT 
mass spanning the gulch is about four feet at one end and two feet 
at the other. As may be seen by the illustration it is about ten feet 
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Fic. 2.—A natural bridge in the Lance formation at head of a gulch on the divide 
between Cow and Lightning creeks, Wyo. 
Fic. 3.—Natural bridge in the Fort Union formation about 30 miles northeast of 
Douglas, Wyo. (Photograph by D. E. Winchester.) 
above the bottom of the gulch. This bridge is apparently more 
stable than either of the others cited. From the appearance of the 
