310 H. I. JENSEN. 
folding, uplift and dissection; the early Permo-Carbonifer- 
ous peneplanation; and the Meozoic and Tertiary periods 
plateau uplift, dissection and erosion. 
9. One mineral deposit characteristic of the area has 
been briefly described and its probable origin outlined. 
Further work in the area will be taken up when time 
permits. The present paper is necessarily of a highly 
generalised nature and based upon scattered observations 
rather than detailed work, except at the Ettrema Canon, 
where more than a week was spent on field work. 
It is interesting also to note that at Sassafras and in all 
the gorges heading in this tableland, the caves in the sand- 
stone cliffs contain an efflorescence of alum. It is possible 
that the production of this mineral may be partly due to 
the slow evolution of sulphuretted hydrogen by the sulphide 
minerals in the underlying formations, and the upward 
passage of the gas into the sandstones in solution in spring 
water. On approaching the surface oxidation to sulphuric 
acid by the aid of iron oxides in the sandstone and the 
reaction of the acid with felspar might easily give rise to 
alum. It may also be due to organic matter in the 
sedimentary rocks. 
On the divide between the Endrick and Ettrema_head- 
waters some dry basins, amphitheatre-like in shape, occur. 
Here the sandstone seems to cave in and drainage appears 
to be subterranean. If appearances be true these basins 
probably overlie cavernous limestone. The matter requires 
further investigation. 
