Secondary Series. 513 



siderable distances from the spots on which they grew. Proofs are 

 daily increasing in favour of both opinions : viz. that some of the 

 vegetables which formed our beds of coal grew on the identical 

 banks of sand and silt and mud, which being now indurated to 

 stone and shale, form the strata that accompany the coal ; whilst 

 other portions of these plants have been drifted, to various distances, 

 from the swamps, savannahs, and forests that gave them birth, par- 

 ticularly those that are dispersed through the sandstones, or mixed 

 with fishes in the shale beds. 



The cases are very few in which I have ever seen fossil trees, or 

 any smaller vegetables erect and petrified in their native place. 

 The Cycadites and stumps of large Coniferous trees on the surface 

 of the oolite in Portland, and the stems of Equisetaceous plants 

 described by Mr. Murchison in the inferior oolite formation near 

 Whitby, and erect plants which I have found in sandy strata of the 

 latter formation near Alencon, are examples of stems and roots over- 

 laid by sediment and subsequently petrified without removal from 

 the spots in which they grew. At Balgray, three miles north of 

 Glasgow, I saw in the year 1824, as there still may be seen, an un- 

 equivocal example of the stumps of several stems of large trees stand- 

 ing close together in their native place in a quarry of sandstone of 

 the coal formation. 



In a paper on the sinking of the surface over coal mines, Mr. Bud- 

 die has shown that the depressions produced on the surface by the 

 excavation of beds of coal near Newcastle-on-Tyne are regulated by 

 the depth and thickness of the coal, the nature of the strata above 

 it, and also the partial or total extraction of the beds of coal. The 

 accumulation of water forming ponds in these superficial depressions, 

 and the sinkings of a railway, have afforded accurate measures of the 

 amount of the subsidences in question. 



WEALDEN AND PORTLAND FORMATIONS. 



In the north of Germany Mr. Roemer, of Hildesheim, has identified 

 beneath the Cretaceous system, the Purbeck stone and beds of the 

 Wealden formation, with nearly all its characteristic shells, and three 

 minute species of Cypris. He has also found the Portland sand 

 and the upper and lower Green sand and the Gault clay, in the 

 north of Germany. He has, moreover, found the Wealden forma- 

 tion near Bottingen in the High Alps. 



CHALK FORMATION. 



In extension of our knowledge of the Chalk formation, the Rev. 

 J. Gunn has sent us a short communication, accompanied by a litho- 

 graph representing the columnar disposition of some Paramoudras 

 to the height of many feet one above another in the chalk of Norfolk. 

 The history of these enormous urn-shaped flints, which were first 

 noticed by Professor Buckland in an early volume of our Transactions, 

 1st series, vol. iv. p. 413. pi. 24., is still involved in much obscurity. 

 Their form is most probably due to siliceous matter collected around 

 and penetrating throughout the substance of gigantic spongiform 

 bodies ; but we have yet to learn the reason why they are occasion- 



PhiL Mag. S. 3. Vol. 17. Supplement, No. 113. Jan. 1841, 2 L 



