226 Review of " Outlines of the 



ics being limited to a few testacea. The trunks, leaves, 

 and, nnore rarely, the pericarps of various vegetables occur 

 in this formation; and all of them are very different from 

 known genera and species, and apparently the growth of 

 a hot, rather than a temperate, climate ; and of moist, 

 rather than dry, situations. The trunks, that have been 

 discovered, belong to a peculiar order of plants, "distin- 

 guished by the cortical part being entirely covered by reg- 

 ular impressions resulting from the petioles of fallen leaves, 

 ranging around them in spiral lines." These remains form 

 but few genera, and, at the most, not above 400 species. 



Trap rocks abound in the coal fields; and this "affords 

 the first instance in descending the series, in which any of 

 the great formations in England appear to be strikingly 

 connected with rocks of this family.'' These traps are ei- 

 ther of the class of greenstones, or of the dolerite class of 

 the French, which is the augite rock of Mac Culloch, in 

 which augite predominates. Varieties of these rocks are 

 a porphyroidal trap and toadstone. They are connected 

 with the coal measures, either as overlying masses, resting 

 unconformably on the subjacent strata, or as dykes, or as 

 beds, conformably interstratified and regularly alternating 

 with the other strata. 



Dr. Mac Culloch found, in the Isle of Sky, that a single 

 mass of trap often occupied all the three positions mention- 

 ed above ; so that the relative position of such rocks fur- 

 nishes no indication of their age. The greenstone, occur- 

 ring in the coal formation along the Connecticut river in 

 New-England, constitutes overlying masses, dykes, and beds, 

 just as in Old England. 



Although Mr. Conybeare has little to do with the Wer- 

 nerian distinctions of transition and secondary, yet if call- 

 ed to decide to which of these the coal measures belong, 

 he would have no hesitation in referring them to the for- 

 mer; " since at least ten characters will be found in com- 

 mon between the carboniferous and transition class, for one 

 which would lead to an opposite arrangement." His rea- 

 sons for this opinion are given at length, and appear coii- 

 elusive; but we have not room to extract them. 



The vast importance of the English collieries, to their im- 



