TRANSACTIONS OF SECTION C. 641 



generally basaltic, and similar to the underlying rocks described above, but with 

 some variation, as if they might represent a broken lava crust. They are crossed 

 by veins of calcite, and the ashy materials and other fragments are often cemented 

 by calcareous deposits. 



The history of Perim Island belorgs mainly to the Tertiar}^ era. We may 

 infer that the Red Sea, from its general contours and the steep descent of the bed 

 towards a central depression, forms part of the Great Rift Valley, extending from 

 Lake Tanganyika to the Jordan, along which at so many places volcanic outbursts 

 on a large scale have occurred. Both in Arabia and in Abyssinia extensive tracts of 

 volcanic rocks are found of more than one period. The rocks of Perim belong 

 probably to the later or so-called Aden group. The raised beaches of the island 

 are au evidence of oscillations of level, which are proved by upraised and submerged 

 coral reefs to have ailected other parts of the Red Sea. Denudation and weathering 

 of the surface took place, and calcareous sediment was deposited, while at different 

 times coral reefs became established in the adjacent shallow seas. 



10. Artesian Water in the State of Queensland, Australia. 

 By R. Logan Jack, LL.D., F.G.S. 



The western interior of Queensland is endowed with rich grasses, but has an 

 insufficient rainfall. This defect, however, has been to some extent compensated 

 by the success in boring for artesian water, which was commenced in 1885. It is 

 estimated that artesian or sub-artesian water is to be found beneath an area of 

 over 264600 square miles. 



The greater part of the western interior of Queensland is composed of soft 

 strata of Lower Cretaceous age, consisting of clay-shales, limestones, and sand- 

 stones. These strata are so disposed that the lower members of the series crop 

 out on the western flanks of the coast range, where not only is the elevation of the 

 surface greater than in the downs to the west, but the rainfall is also com- 

 paratively abundant. 



Along the eastern margin of the Cretaceous area there is a porous sandstone of 

 great thickness, the * Blythesdale Braystone,' and owing to the low dip the outcrop 

 of this permeable stratum occupies a belt from five to twenty-five miles wide ; but 

 the Braystone finally disappears beneath the argillaceous and calcareous upper 

 members of the series which forms the surface of the downs to the west. Several 

 rivers disappear while crossing the outcrop of the Braystone, and the water must 

 be carried in it beneath the clay-shales of the pastoral downs. 



It is believed that the subterranean water leaks into the Great Australian 

 Bight between the 124th and 134tb meridians of east longitude, and perhaps partly 

 into the Gulf of Carpentaria, as the pressures in the wells decrease with their 

 distance from the elevated outcrop of the Braystone. Mr. J. B. Henderson, 

 hydraulic engineer, has constructed a map showing lines of equal pressure, which 

 enable intending borers to judge whether or not, when they strike water, it will 

 rise to the surface. 



The following statistics are from Mr. Henderson's report for the year ending: 

 June 30, 1900:— 



Aggregate depth of bores 

 Number of bores 

 Number of flowing bores . 

 Deepest bore . 

 Highest temperature 

 Largest flow of a single bore 



185 miles. 



839. 



515. 



5040 feet. 



196° F. 



GOOOOOO gallons per day. 



Total output of the 515 flowing bores . 1174Q3574585 gallons per annum. 



The 515 wells would fill a canal 100 feet wide and 20 feet deep, 1779 milei 

 long, in twelve months ; or fill Loch Katrine in a year and a half. 



