BY T. W. EDGEWORTH DAVID. 495 



patches and lumps, like the retinite in the altered brown coal of 

 Invercargill and Kawa Kawa, Bay of Islands, New Zealand, but 

 such do not as a rule occur in the shale. 



(4) Drift timber would be sure to carry fragments of rock or 

 lumps of earth entangled in its roots, and these would be liable 

 to be imbedded in the shale, during the process of maceration, but 

 this is not found to be the case. 



(5) The results of the decomposition of resinous trees would 

 probably be to produce some true resin, but from the reports above 

 quoted of Mr. Dixon and Professor Liversidge, kerosene shale is 

 not appreciably soluble in alcohol, ether, or bisulphide of carbon, 

 and it certainly would have been partly soluble had it contained 

 resin in large proportion. 



Arguments against Theory of Distillation hy Intrusive Igneous 

 Rocks. — (1) In some cases, as at Greta, kerosene shale has been 

 found far removed from intrusive igneous rocks. 



(2) At Joadja, if the shale had resulted from distillation, the 

 seam would have had a tolerably uniform composition, instead of 

 being separated into three distinct layers. 



(3) Oil would be found in the crevices and interstices of the 

 rock wherever it is at all porous. But this has not been observed. 



Arguments against Oil-spriytg Theory. — These would be the 

 same as those already advanced against drift-timher theory^ with 

 the exception of (4) and (5), and with the additional objection 

 that there would be no apparent source for the oil-springs. 



Arguments against Vegetable Secretion Theory. — No valid argu- 

 ments have occurred to the author against this theory, with the 

 exception that it does not fully account for the very lenticular 

 character of the shale, nor from its development being chiefly 

 confined to the edge of the coal basin. It appears, however, by 

 far the best of the theories already advanced, and may be the 

 correct one, though the author thinks that there is more evidence 

 in favour of his own theory. 



