EXPLANATION OF THE PLATES. 



2. Grey marl, with marlstone in its lowest region. 

 a a. Coarse granular limestone, loaded with grains and veins of hydrate of iron. 

 b b. Light brown and yellow calcareo-siliceous sands and sandstones, often highly 

 micaceous. 

 Fig. 2. Section showing details of the Oxford oolite near the east extremity of Weymouth 



Bay. 

 Fig. 3. Detailed section of the strata that occur in the Isle of Portland. 



Note. — Since the paper was printed to which these sections refer, a notice has appeared in 

 the London and Edinburgh Philosophical Magazine, August 1, 1833, p. 158, by Mr. R. PhilHps, 

 containing a minute analysis of the water of two sulphureous springs of similar quality near Wey- 

 mouth, both of which issue from near the junction of the lower beds of the Oxford clay with the 

 cornbrash or upper beds of the Forest Marble Formation. One is situated at Nottington, about 

 three miles on the North of Weymouth, and was described by Dr. Pickford in a small treatise 

 printed at Weymouth in 1821. The other rises at Radipole, about one mile from Weymouth, and 

 was discovered but a short time ago. The most important of the ingredients of these mineral 

 waters is sulphuretted hydrogen, which is derived from the passage of the water through strata 

 that contain iron pyrites in a state of decomposition. Mr. Phillips remarks that " the saline con- 

 tents of these waters are so small in quantity, that they must be considered as quite inert, and 

 therefore those who wish to avail themselves merely of the sulphuretted hydrogen, may take them 

 in larger quantity than if they were active in other respects. 



Plates IV. & V. 



Illustrate Professor Sedgwick's paper introductory to the General Structure of the Cum- 

 brian Mountains, with a description of the great dislocations by which they have 

 been separated from the neighbouring carboniferous chains : p. 47. 



Plate IV. 



Map exhibiting the geological structure of the district, and the range of the band of lime- 

 stone and calcareous slate between the quartzose green slate and the grey wacke slate. 



Plate V. 



Sections exhibiting some of the great dislocations produced by the elevation of the 

 northern carboniferous chain : p. 59. 



Plate VI. 



Illustrates Professor Sedgwick's paper on a Series of longitudinal and transverse sections 

 through a portion of the carboniferous chain between Penigent and Kirkby 

 Stephen : p. 69. 



