FEDERAL SCHOOL OF MINES. 329 



the deposit ; the gases, as they escaped through the oozy and 

 plastic mud, elevated the sediment around the several points 

 of eruption into ring-like layers. 



The sample which I now exhibit occurs at Picton, New 

 South Wales, in the upper course of the Picton Creek, which 

 traverses a valley locally known as Glenforsa. The hills on 

 either side are well-grassed slopes of Wianamatta shales, 

 which are of Triassic Age, and are generally considered of 

 fresh-water origin. I do not know of any extensive slieil- 

 beds or other lime deposit found in the shales, but when 

 traversing the glen some irregular nodules of calcium 

 carbonate were picked out of the banks of the creek. The 

 cone-in cone mineral occurs as a horizontal layer, which is 

 exposed at the bed of the creek, but passes under the 

 adjoining bank. So far as I could learn, it is not now in 

 process of formation. The thickness is about two inches, 

 composed entirely of cones within cones closely packed 

 together. It has been asserted that in some European 

 specimens the apices of the cones point both upward and 

 downward, but in the specimen now under consideration all 

 apices point doM^nward. The open bases of the cones, 

 formed of amphitheatre-like cavities, are about half an inch 

 in diameter, and small ones are sometimes formed within the 

 larger ones. The chemical composition of the sf)ecimen is, 

 approximately — Calcium carbonate, 67"54 per cent. ; matter 

 insoluble in strong hydrochloric acid, 21-2 ; sesquioxide of 

 iron, 4-14 ; magnesium carbonate, "7 ; water, 31. In some 

 parts the mineral is distinctly crystalline, and, in my opinion, 

 a purely mechanical origin can scarcely be entertained. It 

 appears to be a chemical precipitate which has resulted in 

 imperfect or disguised crystallisation. The floor crystallisa- 

 tions, known as " crystal cities," at the Jenolan Caves, 

 N.S.W., have a somewhat similar external form. The 

 mineral might have been formed in the drying up of the 

 calcareous waters of a lake. 



3.— NOTES ON SOME OF THE ADVANTAGES OF A 

 FEDERAL SCHOOL OF MINES FOR AUSTRAL- 

 ASIA. 



Btj JOHN PROVIS. 



The economic development of the mining and metallurgical 

 industries of these Colonies is so intimately related to their 

 future prosperity that I am induced to offer a few suggestions 



