1 lisr ACCESSIBLE VALLEYS 11 



remarkable than the Yosemite itself. This plateau forms 

 the eastern side of the Blue Mountains, and at its eastern 

 margin is about 1,000 feet above the sea level ; but going 

 westward it rises about 100 feet in a mile, so that at its 

 further side, at a distance of twenty-five miles it is 3,400 

 feet above the sea. This slightly undulating monotonous 

 surface is, however, deeply intersected by widely branching 

 ravines which increase in depth as we proceed westward, 

 and which everywhere present perpendicular crags and 

 cliffs of a very remarkable character. The ravines which 

 discharge their waters into the little river Cox occupy an 

 area of 1,212 square miles. The whole forms the basin of 

 this mountain stream, and is bounded by cliffs increasing 

 from about 1,000 feet near its outlet to about 2,500 feet 

 near its western limits, the valley bottom being not much 

 above the sea level, and the only outlet being through a 

 gorge about a third of a mile wide. 



Further to the north is the smaller valley of the Grose, 

 whose diverging ravines interlock, as it were, with those 

 of the Cox, forming a great obstacle to the early explorers 

 in their attempts to cross the plateau. The Grose valley 

 has still grander precipices than that of the Cox, rising at 

 the upper end to 3,000 feet in vertical height. The best 

 account of these valleys is that given in Darwin's work on 

 Volcanic Islands, the last chapter of which is devoted to 

 Australia and other places visited on the homeward 

 voyage. He says : 



It is not easy to conceive a more magnificent spectacle than is 

 presented to a person walking on the summit-plains, when without 

 any notice he arrives at the brink of one of these cliffs, which are 

 so perpendicular that he can strike with a stone (as I have tried) 

 the trees growing at a depth of 1,500 feet below him ; on both 

 hands he sees headland beyond headland of the receding line of 

 cliff, and on the opposite side of the valley, often at a distance of 

 several miles, he beholds another line, rising up to the same height 

 with that on which he stands, and formed of the same horizontal 

 strata of pale sandstone. The bottoms of these valleys are moder- 

 ately level, and the fall of the rivers floAving in them, according 

 to Sir T. Mitchell, very gentle. The main valleys often send into 

 the platform great bay -like arms, which expand at their ujjper ends ; 

 and, on the other hand, the platform often sends promontories into 

 the valleys, and even leaves in them great, almost insulated, masses. 



