262 OCCURRENCE OF DIATOMACEOUS EARTH, 



In 1888 Professor Liversidge published an account of Tripoli or 

 Infusorial Earth* from Bar r aba. 



He states that the " tripoH " at Barraba is made up almost 

 entii'ely of the remains of Diatoms resembling Mehsira. The 

 same author refers to a deposit {oj). cit. p. 194) of " cimolite " 

 from the Richmond Kiver. There can now be little doubt that 

 this materia], described as " a ver}'- white and porous hydrous 

 silicate of alumina,! often sent down to Sydney as meerschaum," 

 must graduate into a clayey diatomaceous earth, as Diatoms in 

 some numliers have been observed by me in a similar rock from 

 the same locality. Professor Liversidge gives analyses of the 

 rocks from both the above localities. 



Mr. R. Etheridge, Junr., has published a short description of 

 some hand specimens of the diatomaceous earth from the 

 Warrumbungle Mountains, and also of similar specimens respec- 

 tively from the Lismore District, Tweed River, and Richmond 

 River Districts. |. 



He refers the barrel-shaped Diatoms, so conspicuous in these 

 deposits, to 3Ielosira, and notes the association with them of 

 spicules of freshwater sponges. 



Last September Judge Docker and the author were afforded an 

 opportunity, through the kindness of Mr. W. L. R. Gipps, of 

 Bearbong Station, of examining the deposit of diatomaceous 

 earth in the Warrumbungle Mountains. 



II. — General Geological Features of the District. 



In the neighbourhood of the diatomaceous earth deposit 

 there are two formations represented: — (1) The Permo-Carboni- 

 ferous Coal-measures, and (2) Trachyte lavas, dykes, and tuffs, 



* The Minerals of New South Wales, &e. By A. Liversidge, M.A. , 

 F.R.S. p. 177. Ti-iibner & Co. London, 1888. 



t Ann. Rept. Dep. Mines, for the year 1887, pp. 165-166. By Authority. 

 .Sydney, 1888. 



X Ann. Rept, Dep. Mines, for the year 1888, p. 190. By Authority. 

 Sydney, 1889. 



