. Natural science: a monthly review of scientific progress. her deposits near the coast. The lower part of the RollingDowns Formation (b i) is that which is of chief importance; it iscalled the Blythesdale Braystone, and consists of a series of soft, gray,very friable sandstones, grits and conglomerates, which absorb waterwith avidity. The outcrop of this rock forms a belt with an averagewidth of five miles, and is estimated to present a gathering-ground forwater of 5,000 square miles. These beds rest unconformably againsta series of Triassic and Jurassic rocks, viz., the Darling DownsBasalt (
. Natural science: a monthly review of scientific progress. her deposits near the coast. The lower part of the RollingDowns Formation (b i) is that which is of chief importance; it iscalled the Blythesdale Braystone, and consists of a series of soft, gray,very friable sandstones, grits and conglomerates, which absorb waterwith avidity. The outcrop of this rock forms a belt with an averagewidth of five miles, and is estimated to present a gathering-ground forwater of 5,000 square miles. These beds rest unconformably againsta series of Triassic and Jurassic rocks, viz., the Darling DownsBasalt (c); Slates, Sandstones, and Coal-seams (d); ToowoombaBasalt (e) ; Murphys Creek Sandstone (f); Ipswich Shales, Sand-stones, and Coals (f 1). Below all come the folded PalaeozoicRocks (g). Above the Rolling Downs Formation lie patches of anUpper Cretaceous Rock, the Desert Sandstone, which once extendedas a sheet over all the rocks just mentioned, but which is now foundonly in isolated patches, some of which obscure the outcrop of theBlythesdale Geological Section, Western Queensland.—R. L. Jack. There are a few water-bearing beds in the higher part of theRolling Downs Formation ; but for effective supplies the bores have topenetrate to the Blythesdale Braystone. This derives its watermainly from the annual rainfall of twenty-seven inches over itsintake area. Much, also, is absorbed from numerous large streams 366 NATURAL SCIENCE. June, which cross its outcrop, but run for only a small portion of the Desert Sandstone is also very absorbent, and where it lies likea full sponge on the top. ... of the Blythesdale Braystone, musttend to equalise the supply by feeding the latter long after the rivershave ceased to run. There is also evidence that the sandy beds d, f,and f1 of the diagram may abut in places on the BlythesdaleBraystone, and still further tend to equalise the supply. Theseauxiliary beds are of greater importance if it be the case, as somesuppose,
Size: 2664px × 938px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisherlondo, bookyear1895
