54 Mr Andrew Taylor on the Coal incrusting the 



such speculations as to the formation of coal. Thus Pro- 

 fessor Newberry of America holds that there is neither 

 sharp dividing line nor permanence in the so-called carbon 

 minerals, — that they are all alike probably the product of 

 the decay of animal or vegetable tissue, liave no fixity, but 

 are constantly forming ; that there appears little call for 

 high heat, time, or pressure in the formation of coal. 

 At the great pitch lake of Trinidad, two kinds of tar, with 

 their solid products, maltha and ozokerite, may be seen 

 simultaneously forming, while not far away may be traced 

 the present formation of lignite. Exhausted oil wells in 

 Pennsylvania are known to be replenished after a few 

 years' rest. It is now thought that petroleum maj' be there 

 filtering up through the great sandstone deposits lying 

 above immense shale beds. When such matter is thrown 

 into a fissure, and becomes inspissated, coals like the Alber- 

 tite of Nova Scotia and Virginia are formed. A tem- 

 perature, then, little if above the ordinary appears sufii- 

 cient for tlie changes indicated by Sir E. Ohristison in 

 these fossils; the heat may have been evolved, and the 

 transformation into coal may have been nearly completed 

 even at the time of deposition. The Sigillaria found in 

 the trap rock in the neighbourhood of Binny Craig {vide 

 Proceedings, 1856) by Dr Sellar may also have been 

 thus formed. Such internal chemistry going on in the 

 underlying shale may act not only as products of material 

 but as dialysers in the process of bitumenisation. Many 

 years ago, in sinking a pit near Bathville, Armadale, Lin- 

 lithgowshire, a sandstone hed was cut through, in which 

 round balls of charcoal, externall}'- amorphous, were regu- 

 larly diffused ; as coal beds were above and beneath, it was 

 [)r(>bably an example of Sir Eobert's thesis. So; indeed, are 

 probably certain beds or " fakes " of sandstone shale, with 

 fossils in the state of charcoal, usually above clean free- 

 stone beds in sandstone quarries. In some well-known 

 household coal seams at Slamannan and in Fife, thin seams 

 of charred wood, sometimes an inch thick, are found inter- 

 calated with the caking coal, 



A special point in Sir Robert's hypothesis of the forma- 

 tion of the coal incrusting these trunks is the origination from 

 8[)ecial centres of the bitumenisation seen in tlie formation 



