by t. w. edge worth david. 489 



Previous Theories about its Origin. 



(1) Drift Tinnher Theory. — With reference to the origin of 

 kerosene shale, the late Rev. W. B. Clarke"^ states that "it has 

 unquestionably resulted from the local deposition of some resinous 

 wood, and passes generally into ordinary coal, many portions of 

 the same bed in the Illawarra mines exhibiting the unmistakable 

 features of the latter and the impress of fronds of Glossopteris as 

 plainly as they are shown on ordinary coal shale." On the follow- 

 ing page Mr. Clarke states, " presuming that the origin above 

 suggested is correct, viz., the occasional occurrence in the 

 ancient deposits of trees of a peculiar resinous constitution, there 

 is no anomaly in finding in one spot a mere patch amidst a coal 

 seam (as is the case at Anvil Creek on the Hunter River), or 

 thick-bedded masses of greater area as in the coal seams of Mount 

 York, or of American Creek in the Illawarra, depending on the 

 original amount of drift timber." This theory is the one at 

 present most generally accepted. 



(2) Distillation Theory. — The late Examiner of Coalfields, Mr. 

 Wm. Keene, F.G.S., was of opinion that kerosene shale owed its 

 origin to a natural distillation of the hydrocarbons from bitu- 

 minous seams through the heat of igneous rocks intruded into 

 the coal-measures subsequent to the formation of the coal-seams. 

 He considered, therefore, that igneous rocks of later date than 

 the coal-measures formed everywhere a necessary accompaniment 

 to kerosene shale. 



(3) Oil-spring Theory. — The late Professor Denton, when in 

 Sydney a few years ago, suggested that kerosene shale was due 

 to local outbreaks of oil-springs, which may have overflowed at 

 the surface and saturated the peaty material in the coal-swamps 

 for a considerable radius around the scene of the outbreak. This 

 explanation, however, simply puts the difficulty back a stage, but 



* Sedimentary Formations of New South Wales, Sydney, i878, p. 66. 



