cvi Report of the Mineralogical Survey [No. 126*. 



secondary conglomerates, nor could the merest tyro on being shewn 

 both, hesitate to discriminate between them. The most obvious dis- 

 tinction is the less earthy or mechanical appearance of the basis and 

 the greater rarity of the imbedded pieces. Is the conglomerate struc- 

 ture, such at least as it is found in crystalline rocks, one which can 

 in any instance be explained by chemical composition, as affected 

 by the many disturbing causes which may well have been supposed to 

 influence the results ? In particular, can we derive any explanation of 

 such a phenomenon from the galvanic energy which we may suppose 

 would be developed by the interstratification of so many heterogeneous, 

 and consequently in some degree anti-polar substances ? Assuredly this 

 cause has had more effect than is generally attributed to it in many 

 of our geological phenomena. Whether the present be one which falls 

 within its domain, remains to be determined. 



2H4. Limestone begins to shew itself in detached masses and frag- 

 ments ; and before reaching Tirnee it occupies considerable extent, 

 and is seen crossing the river valley in well marked strata, which 

 dip N. E. It is generally very impure, being mostly argillaceous. 

 At Tirnee, I found blue argillaceous schist; on ascending a ridge the 

 limestone again appears, always argillaceous ; descending thence, argil- 

 laceous schist is once more established, and continues to Poondaroo 

 village, opposite Roodur Prag, the confluence of the Kalsee with the 

 Aluknunda. It presents some curious appearances, which require a 

 little detail. It is at first of a perfectly white color, soft and earthy, 

 similar in fact to chalk, in all save its schistose structure, and in this res- 

 pect it perfectly resembles the hard blue slate into which it gradually 

 passes. Below the point where this change has taken place, a mass 

 of the greenstone I have so often had occasion to notice may be seen. 

 There is not any transition to be seen between this rock and the blue 

 slate, but it passes into a green slate, whether chloritic schist or green- 

 stone slate, is difficult to determine. The specific gravity is rather in 

 favor of the latter. That of the greenstone is 3.0, it contains therefore 

 evidently either hornblende or augite (hemi-prismatic augite spar.) 

 Besides this, a light yellowish green mineral may be observed, very 

 much resembling serpentine. 



235. In its lower limits it appears to pass into a green quartz rock, 

 coloured no doubt by the same mineral to which it owes its character. 



