§ 13. WEALDEN OF THE ISLE OF PURBECK. 381 



are unequal, and indicate therefore a variation from year to 

 year in the climate of the country in which they grew. 

 The wood exhibits, under the microscope, the coniferous 

 structure seen in the Araucaria (Norfolk Island Pine), the 

 rows of glands or ducts being placed alternately ; and the 

 appearance is similar to that of the fossil wood of Willingdon 

 in Sussex.* I observed no traces of the foliage or fruit of 

 these trees, with the exception of a small cone, scarcely so 

 large as that of the larch. f In the strata that overlie the 

 fossil forest, thin interrupted seams and irregular masses of 

 lignite, more or less impregnated with and permeated by 

 iron pyrites, are very abundant. 



13. Wealden of the Isle of Purbeck. — The Wealden 

 deposits are next seen in the Isle of Purbeck, the south- 

 eastern part of Dorsetshire, which is distant about fifteen 

 miles across the Channel, from the western extremity of 

 the Isle of Wight. This island is an irregular oval area, 

 between thirteen and fourteen miles in length, and seven in 

 average breadth, from north to south. It consists of cre- 

 taceous, wealden, and oolitic strata, which occur in their 

 natural order of succession, but highly inclined, in the 

 section exposed in Swanage Bay, on the east of the island.J 

 In this line of coast the geological structure of the Isle of 

 Purbeck is clearly displayed. In Studland Bay, which is 

 to the north of Swanage, the white chalk is seen to emerge 

 from beneath the eocene strata, and form the cliffs ; rising 

 up into the range of downs that traverses the island from the 

 east to the south-western shore. The curious flexures 

 produced on the beds of chalk and flint by the elevations to 

 which they have been subjected, are remarkably distinct at 



* Medals of Creation, vol. i. p. 160. 



\ An account of the fossil bones, plants, &c. of the Wealden, which 

 have been discovered along the coast in Brook and Brixton Bays, will 

 be found in Excursions round the Isle of Wight, chap. x. and xi. 



X Ibid. chap. xii. 



