454 GEOLOGY A^:D MINING INDUSTRY OF LEADVILLE. 



sive body of White Porphyry was found in it. In other portions it has 

 not yet been actually cut, but its existence is readily deduced from the 

 position of the formations above it. 



Fryer Hill map. — Before proceeding to a description of the underground 

 workings of the various Fryer Hill mines, it may be well to explain what is 

 intended to be i-epresented on the map of that region (Atlas Sheet XXXI) in 

 somewhat greater detail than is given in the legend. It has been attempted 

 here to show on a single sheet the actual surface of the ground, the rock- 

 surface beneath the Wash (distinguishing the different formations which 

 make up that rock-surface), and the underground workings of the various 

 mines, with the outlines of the bonanzas or ore bodies, as far as could be 

 determined at the time of examination. The attempt to delineate so much 

 on a single sheet has resulted in a complication, which it will require the 

 reader's closest attention to unravel. He must first bear in mind that the 

 black contours indicate the actual surface of the ground, and the figures 

 attached to them, their relative elevation above the 10,000-foot curve. 

 Second, that the geological colors indicate the outcrops of the various rocks 

 and formations as they would appear if the superincumbent Wash material 

 (which, as shown by the sections, has a thickness of from thirty to one hundred 

 feet over the whole surface) were entirely removed. Third, that the drifts 

 of the various mines and the outlines of the ore bodies, as determined by 

 the explorations of those drifts and shown in black dots, are projected on a 

 plane surface, or, in other words, are represented as if the rock material 

 above them were entirely transparent and without regard to its thickness. 

 These drifts, while in the main following an approximately horizontal plane, 

 are in many mines on two or even three different levels. Owing to their 

 approximate horizontality it was impossible, without too great complication, 

 to indicate these different levels by any series of colors or conventional 

 signs, but figures have been placed within the drifts to show their elevation 

 in feet above the 10,000-foot curve. The map thus furnishes the data from 

 which a section may be constructed along any given line, and from it the 

 various sections represented on Atlas Sheets XXXII, XXXIII, and XXXIV 

 have been so constructed. In unexplored portions these sections are more 

 or less ideal, and actual exploration may prove them to be not absolutely 



