232 



The Primary Upheaval of the 



quiet retreat in its waters, being cut off from the sea by an 

 effectual bariuer, formed on one side by the waste materials 

 carried down by those streams, and on the other by an accu- 

 mulation of sand caused by the meeting of the marine current 

 witli that of the Yarra. The vast bar or bank of sand (now 

 called by us Sandridge) which was thus created, appears to 

 have been formed by separate deposits acting at long intervals, 

 and not as many suppose, by the drift sands of the coast being 

 carried inland, although the rising of the coast must un- 

 doubtedly have materially assisted in the formation of this 

 remarkable sand-belt. 



The shells and other organic substances in the crater, 

 buried under the clay in the manner above described, by 

 the process of decomposition, evolved nitrogen, hydrogen, 

 oxygen, and sulphur ; the accidental combinations of which 

 resulted in the following chemical changes : — 



1. The combination of sulphur with hydrogen* 



2. The formation of hydro-sulphate of ammonia, by the 



combination of nitrogen, hydrogen, and sulphur. 

 Some hydrogen being subsequently expelled, sulphate 

 was formed, and at length sulphate of ammonia 

 produced. 



3. The formation of water by the combination of oxygen 



and hydrogen. 



My hypothesis assumes the decomposition of sulphate of 

 ammonia to have taken place, owing to a certain elevation of 

 temperature, and the cotemporaneous resolution of the shells 

 (carbonate of lime) into their constituent parts, lime and 

 carbonic acid. The carbonic acid of the shells, combining 

 with the ammonia, was volatilized ; and the lime, uniting 

 quickly with the sulphuric acid of the decomposed sulphate, 

 formed sulphate of lime or gypsum (ca/s.'"}-2 H,) the crystal- 

 ising process bemg effected with a rapidity commensurate 

 with the quantity of crystalising water present. This water 

 results from the decomposition of organic matter, as men- 

 tioned above (vide 3J, and, if present in a less ratio than 

 20*78 per cent, no crystals are produced. 



The specimens accompanying this paper are obtained from 

 Batman's Hill, in the neighbourhood of Melbourne. I am 

 of opinion that gypsum might be subsequently found In 

 considerable quantity in that locality, and if so, will become 

 an article of commercial value, being the substance which, 

 burnt and powdered, forms the well-known material plaster 

 of Paris, extensively used for stuccoing buildings. When 



