DISTIllBUTION OF POEPHYRY BODIES. 209 



from this sheet. A small sheet is found above the Blue Limestone on Iron 

 and Dome Hills. A large bod}^, probably coming up from below, occurs on 

 the southeast face of Yankee Hill, extending across Adelaide Park. Several 

 small sheets are found in the White Limestone on the north end of L-on Hill 

 and in California gulch, and three well-developed dikes cross Printer Bo)^ 

 and Long and Derry Hills. 



On the northwest slope of Printer Boy Hill the Printer Boy Porphyry 

 forms an important mass ; in Iowa gulch is the Green Porphyry, under the 

 White Limestone; and on Long and Derry Ridge, the Josephine Porphyry, 

 above the Blue Limestone. Mount Zion Porphjay, which is closely allied 

 to the White Porphyry, forms a body of great thickness in the Weber Grits 

 on Prospect Mountain, and is found also in Evans gulch, but seems to be 

 simply a local occurrence which reaches its greatest development beyond 

 the limits of the map, and has apparently had little or no influence upon 

 the ore deposits of the district. 



In what follows will be given in detail the various facts upon which 

 the geological deductions represented on the map and sections have been 

 founded, which will probably prove of interest only to those who wish to 

 verify these deductions on the ground or examine into their soundness. 

 For convenience of description the region will be divided into the areas 

 naturally blocked out by the lines of the principal faults, and these will be 

 treated in topographical order, proceeding- from the east westward, and in 

 each block from the south northward. 



AREA EAST OF MOSQUITO FAULT. 



Between Mosquito fault and the crest of the range is a considerable 

 area, occupied principally by Archean exposures, whose description prop- 

 erly belongs to that of the Leadville region, although only a small por- 

 tion of it is actually shown in the extreme southeast corner of that map. 

 In it, immediately below the main crest, are the two great glacial amphi ■ 

 theaters in which headed the gjaciers that carved out Evans and Iowa 

 gulches, and which offer the best opportunities in the immediate vicinity of 

 Leadville for the study of the relations of the ancient crystalline rocks and 

 of the eruptive bodies that have been intruded through them into the over- 



MON XII 14 



