Notices of Memoirs — Biatotnaceous Earth. 227 



nietliylene-iodide, burn away when heated in a current of oxygen, 

 and are unaltered if heated in a current of carbonic acid : the 

 stony matter containing them scratches corundum. Hence 

 Dr. Friedlander infers that they are diamond, and that the South 

 African diamond may have been actually formed, as already sug- 

 gested, by the action of a molten silicate, such as olivine, on 

 graphite : carbonaceous shales are interrupted by the diamond- 

 bearing rock, and numerous fragments of the shale, much altered, 

 are found enclosed in the rock itself. The paper is illustrated with 

 seven micro-photographs. 



II. — Note on the Occurrence of Diatomaoeous Earth at the 

 Wakrumbungle Mountains. New South Wales. By Professor 

 T. W. Edgeworth David, B.A., F.Gr.S. Proc. Linn. Soc. New 

 South Wales, 1896, pt. 2, pp. 261-268, pis. xv-xvii. 

 Diatomaoeous Earth Deposits of New South Wales. By 

 G. W. Card, F.G.S., and W. S. Dun. Eecords Geol. Surv. 

 New South Wales, vol. v, pt. 3, 1897, pp. 128-148, pis. xii-xv. 



DEPOSITS of Diatomaoeous Earth occur not infrequently in 

 Victoria and Queensland as well as in New South Wales, but 

 so far there is no record of them in South Australia or in Western 

 Australia, They are widely distributed in the older colony of New 

 South Wales, for deposits are known at Cooma, about 260 miles to 

 the south of Sydney ; at Bathurst and the Mundooran district, 250 

 miles to the west ; and also in the Warrumbungle Mountains, the 

 Eiohmond River district, and at Barraba, from 300 to 350 miles 

 to the north of Sydney. 



At Cooma the deposit is over 20 feet in thickness ; it lies in 

 a hollow partly inclosed by hills of basalt, and is now only covered 

 bj' surface soil. In the Warrumbungle Mountains there is a bed of 

 diatomaoeous earth 3 ft. 9 in. in thickness, interstratified in trachytic 

 rocks, which are regarded by Professor David as of early Eocene or 

 late Cretaceous age. In the Richmond River district the earth is 

 found in depressions of scoriaceous basalt, and is overlaid by beds 

 of the same material. At Barraba the diatom bed is eight feet in 

 thickness, with a single intermediate band of coarse sand two inches 

 in thickness; beneath it are mudstones and lava fragments imbedded 

 in diatomaoeous material, and it is overlaid by a flow of basalt 

 considered by Mr. E. F. Pittman to be of Miocene age. This 

 covering of basalt is now the summit of an elevated tableland. 



In these various deposits there is a very close resemblance in the 

 character of the diatomaoeous earth, which is a light, whitish, 

 powdery material, typically similar to that known from other parts 

 of the world. In some instances the siliceous constituents have been 

 partially dissolved, and now form bands and nodular masses of hard, 

 homogeneous, colloid silica. Chemical analyses show from 81 to 97 

 per cent, of silica, with, as a rule, small amounts of ferric oxide, 

 alumina, and carbonates of lime and magnesia. 



Microscopic examination shows, further, a very singular uniformity 

 in the diatoms composing these different deposits in New South 



