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spot. At that time the weather was dry, and the spring 

 water only gently oozed from the ground, trickling away with 

 an irridescent oil-like scum. Tiny colourless crystals were 

 observed deposited on sticks and other rubbish in its course. 

 These latter proved to be gypsum; the irridescent scum, a 

 hydratod oxide of iron. The water was found to be charged 

 with sulphates, chiefly of calcium. 



About six weeks later, it being wet weather, a second 

 visit was made. The waters were, on this occasion, observed 

 flowing away white and milky. The milk-like appearance 

 was found to be due to an abundant fine white precipitate of 

 calcium sulphate. 



Putting these observed facts together, it is evident that 

 the Wadella Springs are deep-seated in their origin, and 

 mineralized with abundant sulphate contents. Iron sulphate 

 is a notable constituent, no doubt derived from the oxyda- 

 tion of pyritous bodies below. The iron in such chalybeate 

 waters is readily thrown out as hydrated oxide by calcium 

 carbonate, or organically derived substances, such as ammon- 

 ium humate, occurring in surface waters. Under ordinary 

 conditions the process is slow, and the calcium sulphate formed 

 crystallizes out as gypsum ; in wet weather, when surface 

 water, saturated with calcium carbonate, flowing over the 

 ground, meets the spring water, an abundant, fine white pre- 

 cipitate of calcium sulphate (gypsum) takes place, producing 

 the milky appearance. 



It is further evident that the bog-iron ore deposit in 

 proximity has originated from these spring waters. The fact 

 that the present outlet of the springs is about 50 feet below 

 the top of the ironstone deposit indicates the lapse of a con- 

 siderable period of time since the maximum phase of activity 

 when notable ore-deposition was in progress. The ore body 

 is very similar to the scattered limonite deposits in the Mit- 

 tagongf district of New South Wales. 



The Wadella Springs are of further interest, as affording 

 an illustration of how sfypsum deposits may originate, thereby 

 aiding: to explain the vast accumulations and widespread dis- 

 tribution of the latter mineral in self-contained inland drain- 

 age basins of South Australia, where abundant calcareous and 

 pyritic schists are exposed for denudation. 



