62 Professor BucklancTs Address. 



considers that no drifted plants occur in coal-fields, and that all the ve- 

 getables which are now converted into coalj grew upon swampy islands 

 covered with luxuriant vegetation, which accumulated in the manner of 

 peat-bogs ; that these islands, having sunk beneath the sea, were there 

 covered with sand, clay, and shells, till they again became dry land, and 

 that this operation was repeated in the formation of each bed of coal. In 

 denying altogether the presence of drifted plants, the opinion of the au- 

 thor seems erroneous ; universal negative propositions are at all times 

 dangerous, and more especially so in geology : that some of the trees 

 which are found erect in the coal-formation have not been drifted, is, I 

 think, established on sufficient evidence ; but there is equal evidence to 

 shew that other trees and leaves innumerable which pervade the strata 

 that alternate with the coal, have been removed by water to considerable 

 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 ac- 

 company the coal ; whilst other portions of the plants have been drifted 

 to various distances from the swamps, savannahs, and forests that gave 

 them birth, particularly those that arc 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 cyca- 

 dites and stumps of large coniferous trees on the surface of the oolite in 

 Portland, and the stems of equisetaceous plants described by Mr Mur- 

 chison in the inferior oolite-formation near Whitby, and erect plants 

 which I have found in sandy strata of the latter formation near Alcncon, 

 are examples of stems and roots overlaid by sediment and subsequently 

 petrified without removal from the spots in which they grew. At Bal- 

 gray, three miles north of Glasgow, I saw, in the year 1824, as there still 

 may be seen, an unequivocal example of the stumps of several stems of 

 large trees standing 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 Buddie 

 has shewn that the depressions produced on the surface by the excavation 

 of beds of coal near Ncwcastle-on-Tyne are regulated by the depth and 

 thickness of the coal, the nature of the strata above it, and also the par- 

 tial or total extraction of the beds of coal. The accumulation of water 

 forming ponds in these superficial depressions, and the sinkings of a rail- 

 way, have afforded accurate measures of the amount of the subsidences 

 in question. 



Wealden and Portland Formations. — In the north of Germany, Mr Itoe- 

 mer of Hildesheim has identified beneath the cretaceous system the Pur- 

 beck stone and beds of the Wealden formation, with nearly all its charac- 

 teristic 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, 



