67 



On the west side an adit has been driven in towards the 

 centre of the rock 30 ft. ; and in the floor of a chamber, 

 excavated 10 ft. in from the mouth, a winze has been sunk 

 a distance of 16 ft., and again from the bottom of this a drive 

 put in about 18 ft. to the west. 



Near the mouth of the adit, some 30 ft. below the top 

 of the rock, a fissure was observed, lined with a phosphate 

 similar to that on top of the rock. Within the rock, in chim- 

 ney-like pipes, a foot or more in diameter, and closed at either 

 end, a dark chocolate-coloured substance was observed in 

 crustified layers; this substance chiefly consists of ferric oxide, 

 with abundance of ammonia and nitrate, and a small quantity 

 of phosphate. In the vicinity of these chimneys the whole 

 body of the rock, which is a porous, ferruginous sandstone, is 

 charged with these fertilizers. More remote from such chan- 

 nels, the valuable contents diminish in amount until traces 

 only can be detected in the rock. Nitrogenous rock was met 

 in the lower drive, indicating a considerable vertical extension 

 of impregnation. 



IV. Origin of the Epigenetic Fertilizer Contents. 



A careful consideration of the nature of the occurrence 

 leaves no other conceivable explanation of genesis than that 

 this peculiar combination of substances originated from a 

 guano deposit. We surmise that a considerable accumula- 

 tion of bird-droppings have, in not remote times, been de- 

 posited on Elder Rock, and since largely removed by 

 rain water. As already remarked, there is evidence of 

 one-time swampy conditions in the vicinity, along the course 

 of Grampus Creek, favouring the possibility of abundant bird 

 life. In any case, its prominence determines it a natural 

 resting-place for flying creatures, and so present conditions, 

 even, are favourable to accumulations of bird guano. Con- 

 firmation of this latter argument, as well as the bird-derived 

 origin of the phosphate, is had in a similar, though smaller, 

 deposit, encrusting the summit of a lofty quartzite peak, about 

 one mile west of the Ajax Mine, near Beltana. At this latter 

 locality, when visited last January, recent bird-droppings were 

 found passing into material identical with that at Elder 

 Rock; moreover, a large eagle took flight from the spot as we 

 approached. 



The residuary yellow phosphate on top of Elder Rock has 

 resulted by various chemical changes effected in the guano ; 

 the more soluble compounds having passed away in solution 

 and the comparatively insoluble iron and aluminium phos- 

 phates remaining. This latter owes much, in a genetic 

 sense, to arid climatic conditions. Though not a simple mine- 

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