STEUCTUBE OF NOETH IEON HILL. 403 



phyry masses are, however, much more varied and numerous. It may be 

 safely assumed that they are mostly intrusive sheets, but the underground 

 workings are not yet sufficiently extensive to determine whether they may 

 all be considered so or not. As has already been noticed in the general 

 description, Part I, Chapter V, there is reason to suppose that one body of 

 Gray Porphyry, extending from Adelaide Park up the south slope of Yankee 

 Hill, has cut up across the formations from below. 



The different bodies of porphyry that have been thus far disclosed in 

 this portion of the hill may be enumerated as follows, commencing with 

 those which stand the highest in geological horizon: (1) The main body 

 of White Porphyry overlying the Blue Limestone; (2) a second sheet, cut- 

 ting across the basset edges of the limestone and connected with No. 1 ; (3) 

 a small body of Gray Porphyry between No. 2 and the Parting Quartzite; 

 (4) a thin sheet of White Porphyry, splitting the Parting Quartzite into two 

 parts ; (5) a heavy body of Gray Porphyry, with two smaller sheets, prob- 

 ably offshoots, above and below it, respectively, all three in the White 

 Limestone; (6) a lower sheet of White Porphyry, also in the White Lime- 

 stone. The distribution of these bodies and their probable extent can be 

 best seen by reference to Atlas sheet XXVII. 



Section A, drawn at an oblique angle to the strike, passes first through 

 the Argentine ground and then through the Adelaide, showing the dis- 

 tribution of the ore bodies in the latter. At its southeastern extremity only 

 White Porphyry is given as cut by it, as it is supposed to be in the strike 

 of the cross-cutting body of this rock. In the entire want of any actual 

 data this theoretical representation may not be absolutely correct. The 

 Blue Limestone is split into two wedge-shaped and probably overlapping 

 bodies. The upper or northeast portion has been eroded off in the Adelaide 

 and Argentine ground. Whether it has also been removed here, as repre- 

 sented in the section, or whether a portion should be shown in the White 

 Porphyry, can only be determined by actual developments. The lower 

 wedge-shaped portion of the Blue Limestone, extending to the south and 

 west in normal contact with the Parting Quartzite, is supposed to come in 

 a short distance southwest of this line, as shown in Section C, whose eastern 

 end is nearly in the plane of Section A. 



