EXPLANATION OF SECTIONS. 267 



marking, is not indicated in the Blue Limestone in the basin of Little 

 Stray Horse Park, not because there is any reason to suppose that it does 

 not exist there, but simply because explorations have not proved its exist- 

 ence and in drawing sections the practice has been established of only in- 

 dicating replacement where it has been actually proved. The steep slope 

 given to the beds west of Fryer Hill, as they pass under the western syn- 

 cline, is deduced from data obtained on the line of the next following 

 section. It will be observed that the intersection of the line along which 

 the White Porphyry cuts across the Blue Limestone is here farther -east 

 than in the preceding section, and that the eastern extent of the lower 

 White Porphyry body is considerably greater is proved by actual develop- 

 ment. 



Section D. Section D starts from the same point on the eastern edge of 

 the map as the preceding, but follows a line slightly divergent from it, run- 

 ning due west. The planes of the two sections are so close together that 

 it will be only necessary to mention the points in which the structure of 

 the latter differs. In the South Evans anticline it shows the irregular 

 intrusive sheet of porphyry at the base of the Blue Limestone, developed 

 in the Last Chance shaft, and the lower sheet of White Porphyry, cutting 

 up into the Lower Quartzite and splitting off a portion _of it, as shown in 

 the Hoosier Girl (Gr-44). The intersection with the Colorado Prince fault 

 at an acute angle renders the representation of the western slope of the 

 South Evans anticline somewhat less simple. Its line passes through the 

 crest of Yankee Hill, showing the replacement of the Blue Limestone in the 

 Greenwood and Little Champion shafts, and, on the eastern rim of the Little 

 Stray Horse syncline, the steep dip of the contact which is developed in 

 the Scooper shaft. At Fryer Hill it passes along the bed of Little Stray 

 Horse gulch, showing that the Blue Limestone horizon has there been eroded 

 off. It likewise passes through the Bob Ingersoll shaft, and shows the steep 

 dip theoretically required on the western slope of the anticline by the 

 development of this shaft. 



section E. Section E runs due east and west along the parallel of lati- 

 tude 39 15', which forms the middle of the map, and is but a compara- 

 tively short distance south of the line of the two previous sections. On the 



