COAL. 303 



containing bitumen, carbonaceous matter, and vege- 

 table fragments. In the clays, imbedded nodules, or 

 distinct strata of argillaceous ironstone often occur, 

 and in conspicuous quantities ; forming the principal 

 supply of ore for the iron-foundries. Galena and 

 blende are sometimes found with the ironstone, as is 

 pyrites in the coal itself, as well as in the accompa- 

 nying strata ; being the not infrequent cause of spon- 

 taneous combustion. When porcelain jasper exists, 

 it must be considered as a casual and artificial mineral, 

 produced by this cause. The most singular, as the 

 rarest mineral, observed in this series, is that inflam- 

 mable substance called Hatchetine, imbedded in very 

 small quantities in the ironstones. 



Though the coal series is situated between the older 

 and newer red sandstones, it is impossible to give an 

 universal description of its geological connexions. The 

 exact relations, distribution, and number of the strata, 

 throughout even Europe, are far from being satisfac- 

 torily ascertained ; and as to the world at large, our 

 ignorance is still greater. The difficulty has been much 

 increased by confounding the upper deposits of coal, 

 here ranked as lignites, with those of the present 

 series ; the mineral alone, as is too common with ge- 

 ologists, having formed the chief object of atten- 

 tion, to the exclusion of the geological characters and 

 positions. I must therefore limit this description to 

 Britain, where the subject has alone been accurately 

 studied ; and thus, supposing the series complete, the 

 old red sandstone and the mountain limestone are fol- 

 lowed by the coal series, to which succeeds the mag- 

 nesian limestone and the red marl, and, subsequently, 

 such other strata as may be present in that particular 

 tract. 



Now it is essential to remark, that the old red sand- 



