498 NOTE ON THE ORIGIN OF " KEROSENE SHALE," 



spore showers would fall with tolerable uniformity over the edges 

 of the plains of the Greta coal-basin, only such portions of the 

 showers as fell on the surface of the lakes would be fairly free 

 from admixture with vegetation, and so would form, when they 

 sank water-logged to the bottom, a tolerably pure inflammable 

 deposit, with, of course, a certain amount of peaty material 

 intermixed. Every one of the minute laminae of the kerosene 

 shale may therefore represent a spore shower, or a season 

 of spore showers, so that it may have taken many hundreds of 

 years to have admitted of the formation of a seam of kerosene 

 shale five feet thick, as at Hartley. It is possible, however, that 

 these lamin?e may be simply due to superincumbent pressure, 

 irrespective of individual spore showers, and they may therefore 

 have no special chronological value. Subsequent to these sap- 

 posed local accumulations of pure spore deposits in the shallow- 

 lakes of the Greta coalfield, there is evidence of sedimentation 

 having set in again, which, before the close of the Permo- 

 Carboniferous Period, buried the Greta coalfield in places under 

 at least 6000 feet of strata. The great pressure and considerable 

 heat consequent on the Greta coalfield being loaded with such a 

 thickness of sediments would tend to efiace the original sporaceous 

 character of the lacustrine spore beds, especially in those areas 

 where the deposit was so fine that the individual spores were in 

 close contact with one another ; but where they were much inter- 

 mixed with muddy sediment, the isolation of the individual 

 spores would prevent their being agglutinated, so that it is chiefly 

 to these impure varieties of kerosene shale that observation may 

 be most advantageously directed with a view to seek further 

 information as to the origin of the purer varieties. 



Possibly the minute spherical bodies observed by the author 

 in association with kerosene shale may be the spore cases of 

 Ehizocarps allied to Salvinia of the present day, and so abundant 

 in the bituminous Huron Shales of Ohio. 



The origin of the kerosene shale of New South Wales from 

 seeds or spores is stated by Mr. Dixon, in his paper above quoted, 

 to have been advanced before by some one, but up to the present 



