592 
Where the hasalt has decomposed into soil on the spot it gives rise to open, 
well-grassed country, almost bare of trees. Where, on the other hand, the soil has been 
re-deposited in alluvial flats on the sides of the river courses, it is usually covered by 
dense tropical jungle. 
The surface of the basalt coulees, as well as of the dome-shaped centres of 
eruption, are frequently scoriaceous in a marked degree, forming spongy masses, light 
and porous as pumice-stono. Occasionally the basalt of the coulees is columnar, as at 
the Waterfalls in the Endeavour, between Williams’s Station and Brannigan’s. There 
the basalt is of the usual character, but contaiirs occasional hornblende crystals and 
much olivine. It also contains lievrite in geodes. 
Gate’s Look-out is a volcanic centre of a different character — the once deep-seated 
stump or “ neck ” of a crater, which discharged showers of ashes from its mouth. It 
forms a conspicuous mountain of tuff, and can be seen from Isabella Creek to cut 
through the escarpment of a thickbed of the Desert Sandstone. Therock is an agglomerate 
of volcanic dilris, with a certain rude bedding — courses of larger alternating with 
courses of smaller bombs — having a dip to the east at about 15°. That the 
bombs are not detached fragments of an already consolidated rock, but have been 
consolidated from a molten mass while whirling through the air, is proved by the 
spherical envelope of vesicular basalt which invariably enfolds them. The interior of 
the bombs, which range from an eighth of an inch to a foot in diameter, is a mass of 
black and green crystals of augite and olivine.* 
The Morgan Tableland is a fragment of the Desert Sandstone, about four miles 
across, and resting on upturned slates. Near its northern extremity a bald — i.e., 
treeless — mamelon, another of the volcani jbei, rises out of the slates, below the level 
of the Desert Sandstone. Another, which I was unable to visit owing to the prevalence 
of “ Devil-Devil ” country of a very pronounced type, was seen about three miles east 
of the Morgan Tableland. 
Below the level of the tableland of Older Yolcanic rocks, a flow of basaltic lava 
partly fills up the Valley of the Mulgrave Eiver, and doubtless covers alluvial deposits. 
This lava must, of course, have been poured out after the Older Volcanic rocks 
abutting against the granitic Bellenden-Ker Eange had been cut through by the 
Mulgrave. 
In the Herberton Deep Lead, stream tin ore in considerable quantities has been 
obtained from a gravelly wash beneath a capping of basalt, which fills up the Valleys of 
Nigger Creek and the Wild Eiver. The wash rests on granite. 
Some remarks on the basalt-flows down the Valley of Eeedy Brook, &c., and 
volcanic foci, which I suspect belong to the Newer Volcanic period, although occurring 
in connection with Older Volcanic lavas, will be found on page 581. 
In the neighbourhood of Gunnawarra Station (Herbert Eiver waters) “ the 
prevailing rocks are vertical schists overlain in places by sheets of basalt, which appear 
to occupy portions of some of the existing valleys.” f 
Besides the localities above refeiTed to, basaltic lavas occur in the following 
places under conditions which show that the Desert Sandstone had been denuded before 
they were poured out : — 
California Greeh {Tate River ). — The floor of the valley above the tin-mining 
township of Ord is covered by a flow of doleritic lava. 
* Report by R.L. J. on E.vplorations in Cape York Peninsula, 1878-9. Brisbane ; by Authority : 
1881. 
+ Report on the Coolgarra Tin Mines and Surrounding District. By A. Gibb Maitland. Brisbane : 
by Authority : 1891. 
