34 



As the chemical composition of the scoriaceous material 

 was likely to afford some evidences that might be useful for 

 determination, a typical sample was placed in the hands of 

 Mr. W. T. Chapman, Analyst and Assayer at the Adelaide 

 School of Mines and Industries, who kindly undertook to 

 analyse the specimen. 



LLC oJiJ^UIXXJ.CJJ.. J-"V iVfij 



Si0 2 







.. 71-48 



A1 2 3 







.. 1217 



Fe 2 3 







.. 1-73 



FeO 







.. 332 



MgO 







.. 202 



CaO 







.. 312 



Na 2 







.. 106 



K 2 







•92 



Water at 100° C. 







.. 145 



Water over 100° C. 







.. 207 



Ti0 2 







•52 



MnO 







present 



99-86 



A vesicular rock, such as those found in the Findon 

 gravels, if of volcanic origin, would probably represent an 

 extrusive lava of basic composition, such as are commonly 

 known as basalts, or allied forms. The chemical analysis, 

 however, as shown above, does not suggest such a relationship. 

 There is an excess of silica as compared with the basaltic 

 group, as well as a low proportion of the ferro-magnesian 

 elements, and also a low percentage of lime. This discordance 

 in chemical composition, as well as the very high probability 

 that there are no extrusive lavas in the country within 

 hundreds of miles of the place where the stones were found, 

 practically negatives the idea of their volcanic origin. 



I venture to suggest that these scoriaceous stones have 

 had their origin in bush fires. Some large tree stumps have 

 been known to smoulder for weeks after a bush fire. A little 

 alkaline material in the soil would assist the fusion of mineral 

 substances, and the presence of organic matter in combustion, 

 under superincumbent pressure, might yield the gas necessary 

 for the formation of a vesicular structure. A termite's nest 

 in the soil at the base of a large tree, or within a hollow 

 stump, might be favourable for the formation of stones of 

 this kind. 



Other Localities. — Specimens of a simliar kind have 

 turned up from other localities. Many years ago I received 

 a stone of an open and cindery structure sent down from 

 Central Australia, the sender being under the impression 

 that it was a meteorite. Mr. A. Canning, late school teacher 



