I9IT.] STEVENSON— FORMATION OF COAL BEDS. 91 



inches in diameter were converted into coal. ^Mineral charcoal is 

 abundant in a mine in Camden County, while at Murrurundi the 

 boghead " contains numerous fragments of mother-of-coal and small 

 fragments of what appears to be coniferous wood like Arancaria, 

 together with coniferous fruit." 



In the pages already cited, David gives ten analyses by Mungaye, 

 which show that at Murrurundi the ash varies from ly to 68 per 

 cent, and the fuel ratio from o.ii to 0.24; while at Ketoomba eight 

 analyses show ash from 10.7 to 78.1 and the fuel ratio from 0.13 

 to 1. 10. A specimen from Joadja Creek had "jy per cent, of silica 

 in the ash. 



The material studied by Bertrand and Renault consisted of two 

 great blocks, one in Paris and the other in Brussels, each more than 

 one meter thick, apparently the full thickness of the deposit. Like 

 the Autun mineral, the kerosene shale consists of a fundamental 

 brown, flocculent material, holding alg?e and remains of dead plant 

 tissues. The algae are assigned to the genus Rcinschia, now ex- 

 tinct, but belonging to a group which was spread widely during 

 Permo-Carboniferous times. The alg^e are all separate, though, at 

 times, owing to paucity of the fundamental matter, they are in con- 

 tact, they are still independent. They were free, floating on the 

 surface of absolutely tranquil brown water, and they rained down 

 upon the bottom, while at the same time, under the influence of cal- 

 careous waters, an ulmic jelly was precipitated to form the funda- 

 mental material. The great specimen in the Paris ^Museum shows 

 36,000 beds of these alg^e, but the proportion of algae varies in the 

 several layers from 0.019 to 0.900 of the whole mass. At Joadja 

 creek the mineral is often beautiful, with a satin-like homogeneous 

 surface, and it consists almost wholly of the alga?. 



Infiltrations are here as at Autun. The most important is red- 

 brown, in strings or sheets, and shows fluidal structure ; it is harder 

 than the fundamental material ; it often impregnates leaves and 

 wood ; some plants have the property of absorbing this to a notable 

 extent. Its mode of occurrence and its tendency to penetrate the 

 substance of plant remains suggest great resemblance to the thelotite 

 of Autun. The authors make no attempt to decide respecting the 



91 



