STRUCTURE OF RUBY HILL. 33 



into the Albion, where it is smaller and less distinct and probably disap- 

 pears altogether. 



The Ruby Hiii fault and the quaruite. — Wherever the main fissure comes in contact 

 with the quartzite the dip of the face of the latter corresponds with the dip 

 of the fissure. The reason for this coincidence of dip is obvious. The 

 face of the quartzite when in contact with the fissure is no longer the orig- 

 inal contact of quartzite and limestone, but is the fault face of the south- 

 western uplifted country. The manner of this upheaval is explained in 

 Fig. 2, Plate IV. The change of dip of the face of the quartzite when it 

 comes in contact with the fissure can be noticed on the vertical cross sec- 

 tions (Plates V. to XII.). Up to the present time no signs of the fissure enter- 

 ing the quartzite have been observed, and it is not to be expected that it 

 will do so until a much greater depth is obtained. Nevertheless, as all the 

 shale and limestone beds and the quartzite pitch off flatter as the valley is 

 approached, it is but reasonable to suppose that the fissure will eventually 

 enter the quartzite unless the dip of the fissure also should decrease very 

 materially. From the fact that an important fault has taken place on the 

 fissure, it is not likely that depth will effect its dip in any marked degree. 

 Neither is it probable that it will disappear at any depth to which explora- 

 tions can be carried, as the fault which produced it is so widely extended. 



Mr. Hague says that the thickness of the Prospect Mountain limestone 

 can be taken at 3,050 feet. As close a calculation as it has been possible 

 to make of the thickness of the bed of limestone between the lower or in- 

 tercalated bed of shale and the Secret Canon shale gives this bed a thick- 

 ness of about 1,300 feet. Allowing 100 feet for the thickness of the lower 

 shale, there remain 1,650 feet of Prospect Mountain limestone. This cal- 

 culation is based upon the measurements that have been made near the 

 Eureka main incline and the Locan shaft, and presupposes that the dip of the 

 strata is 40°. If there were no other factors to be regarded, the distance 

 at which the Ruby Hill fault could be expected to enter the quartzite would 

 be about 2,200 feet below the twelfth level of the Eureka, or 3,230 below 

 the top of the Lawton shaft. It is almost certain, however, that this dis- 

 tance will be very much decreased, owing to the fact that this lower bed 

 of limestone has been very much crushed and pressed together by the 

 2654 L 3 



