WESTEEIf PORTION OF THE AQUARIUS. 295 



Water Pocket fold on the east appears to have been, during the latter part 

 of the Cretaceous age, an island. It is apparently possible to designate 

 roughly the positions of large portions of its east and west coast-lines. In 

 a word, those coast-lines may have been approximately coincident with the 

 axes of those two flexures. The northern part of this island cannot at 

 present be ascertained, because the lavas have deeply buried it, and there 

 is not even sufficient basis for conjecture. But of the portions now indi- 

 cated it is possible to infer that the length of this island must have been at 

 least 90 miles and its maximum width about 35 miles. 



The northwestern angle of the Aquarius is laid open by an immense 

 gorge. A mass of lavas and conglomerate more than 2,000 feet thick is 

 revealed, and beneath them hes the Tertiary. Near the opening of this 

 gorge the Grass Valley fault cuts across it, throwing down the platform to 

 the west. Along the western base of the Aquarius the faulting becomes 

 very complicated, and the displacements are great in their vertical extent. 

 The faults are repetitive, or " stepped," with numerous instances of the 

 dropping of large blocks between faults of opposite throw. These blocks 

 usually sag in the middle, and there is occasionally some chaos produced 

 in the component masses. An effort was made to find the proper restor- 

 ation, but I am doubtful whether it has been very accurately done. (See 

 stereogram.) 



The western wall of the Aquarius, which looks down upon the south- 

 em portion of Grass Valley and the Panquitch Hayfield, is of great gran- 

 deur, rising more than 4,000 feet above the valley below. Apparently it 

 is composed of volcanic materials from top to bottom, but the thickness of 

 the volcanic masses is less than it seems at first. The wall rises by success- 

 ive steps, and each step represents a fault, so that the aggregate thickness 

 of lava and conglomerate probably will not exceed 2,000 feet on the aver- 

 age. The rocks are mainly trachytic, but a large proportion of augitic 

 andesites is associated with them. At the summit of the plateau near the 

 western crest and upon the thrown blocks which are successively passed 

 as we descend, are numerous fields of ancient basalt much eroded, and 

 presenting a similar appearance to the scattered basalts spoken of in the 

 preceding chapter as occurring upon the surface of the Awapa. Their 



