68 



ral compound, we will, for the sake of brevity, refer to this 

 residuary phosphate as paratooite. No similar substance has, 

 to our knowledge, been previously recorded from South Aus- 

 tralia, though it is likely distributed in scattered occurrences 

 where the physiographic conditions are similar. 



The paixifooite from near Beltana encrusts quartzite and 

 contains only small quantities of iron. That from Elder Rock 

 contains abundance of iron, which has evidently been derived 

 by chemical changes from the underlying ferruginous breccia. 



Part of the soluble salts in the guano has been lost by 

 torrential rains; much appears to have sunk deep into the 

 porous rock below, and is specially concentrated, as already 

 remarked, on the walls of the- crevices and chimneys. 



Samples of rock taken at intervals in depth below 

 the paratooite showed, when tested qualitatively, a 

 regular decrease in phosphate contents and gradually 

 increasing ammonia and nitrace. Three chief zones were 

 recognized : At the surface, j,r/rafooite containing no appre- 

 ciable amount of ammonia or nitrate ; below, the rock was 

 found charged with phosphates and ammonia, and but mere 

 traces of nitrate; at greater depths, for example, in the 

 lower drive, 46 ft. below the top of the rock, ammonia and 

 nitrate were found in the rock, and only traces of phosphate. 



The ammonia content of the intermediate zone is regard- 

 ed as existing chiefly in the form of ammonium phosphate 

 (stercorite molecule). In the lowest zone it is likely com- 

 bined as ammonium nitrate. The possibility of the presence 

 of more than inappreciable amounts of the nitrates of sodium 

 and potassium is eliminated by the absence of these elements 

 in notable quantities, as proved by an analysis of a bulk 

 sample of the rock. The better quality of this impregnated 

 rock bulked about 5 per cent, of ammonium nitrate. 



The chimneys m.et with in excavating operations had no 

 connection with the exterior, and as no trace of bat guano or 

 bones was found, the main responsibility is thought to lie with 

 birds. 



V. Chemical Composition and Physical Characters of 

 Paratooite. 



The substances examined are mixtures of several phos- 

 phates, with much mechanically-admixed sandy matter. A 

 petrological examination revealed two main distinct mineral 

 forms in the paratooite, readily distinguished by being iso- 

 tropic and anisotropic respectively. 



Two samples were selected for analysis. One of these 

 chiefly composed of the isotropic variety, the other mainly 



