HOOSAO MOUNTAIN. 71 



As regards the structural observations it was not practicable to attempt 

 these in detail; in the first or westerly band <>t' white gneiss, found only in 

 manholes, both east and west dips were observed, and no contact was seen 

 with the next rock — the albite schist. 



This next band, the albite-schist, has in general an easterly dip, hut 

 towards the contact with the next band of white gneiss lias a very steep dip 

 varying from east to west. There is a conformable contact and transition 

 between the two rocks. 



In the next band of white gneiss dips were noted varying from steep 

 east to west: the observations are put down in the section. At about 6,000 

 feet the rock becomes coarser in character, corresponding to the white 

 gneisses, transitional to the granitoid; it contains frequent round pebbles of 

 blue quartz, corresponding to the conglomerate found in the dumps of the 

 tunnel. From here for about 700 feet we have transitions to the coarse 

 gneiss; lenses or layers of fine-grained gneiss are frequently seen. Nearly 

 a whole day was spent here in searching for a contact, by careful hammer- 

 ing, but none could be found; there is an evident transition, as observed 

 elsewhere at points outside the tunnel. 



The area of the coarse granitoid gneiss contains rock of an even char- 

 acter: whatever structure exists by arrangement of mica planes, etc., 

 remains flat or gently rolling east and west. The east contact between this 

 rock and the conglomerate-gneiss is concealed by the brickwork. 



This east band of the conglomerate-gneiss, as on the surface, is char- 

 acterized by a steady, well-marked easterly dip of 20° to 30°, ami this 

 ends very near the central shaft, where the rock is overlain by the albite- 

 schist; its thickness is accordingly about 600 feet, which agrees closely 

 with that found on the surface. The structural planes of the two rocks are 

 absolutely conformable, both dipping east about 25°. The line of contact 

 is easily found; within a few inches of rock they pass into each other with- 

 out a break. From here through the rest of the tunnel only the albite- 

 schist, passing in the last 6,000 feet into fine-grained greenish schists, is 

 found. The dip of the structural planes is always steep east. The rock 

 varies in character as on the surface, in color, coarseness, amount of albite, 

 quartz lenses, etc. 



The main facts then brouffht out in the tunnel are that there is a large 



