EXPLANATION OF THE PLATES. 



Plate XXIX, 



Contains three geometrical elevations of Cader Idris, with the heights, in feet, above 

 the level of the sea. The base of the North elevation is the valley of the river 

 from Dalgelle to the sea. That of the South elevation is the valley of Tal y Llyn. 

 That of the Section is a line running from the head of Tal y Llyn lake in a 

 N.N.W. direction, through the summit of Cader Idris, to the river Mavvddach. 



PLATE XXX. 



Illustrates Mr. Lyell's papers, on the Strata of the Plastic Clay Formation exhibited 

 in the Cliffs between Christchurch Head, Hampshire, and Studland Bay, Dorset- 

 shire ; and on the Freshwater Strata of Hordwell Cliff, Beacon Cliff, and 

 Barton Cliff, Hampshire. 



Fig. 1. Section of the coast from Muddiford, Hants, to Studland Bay, Dorset. 



Fig. 2. Section of the lower freshwater strata in Hordwell, Beacon and Barton, Cliflfs, 

 Hants. 



PLATES XXXL & XXXII. 



Illustrate Mr. Murchison's paper on the Brora Coal-field, and some other Stratified 

 Deposits in the North of Scotland. 



Plate XXXI. 



Fig. 1. A map of all that part of the S. E. coast of Sutherlandshire in which any 

 members of the oolitic series have been traced, including the coal-field of Brora; 

 showing also the nature of the mountain chain which bounds the Vales of Brora, 

 Loth and Navidale. 



In the lower part of the same figure is a sectional view of the coast laid down 

 in the map. 



Fig. 2. Consists of transverse sections. The first is ideal, explaining the entire order 

 of superposition on the east coast of Sutherland, Cromarty and Ross ; followed 

 by six actual sections from the shore to the mountain chain, — of which that on 

 the line C, D of the map particularly explains the relations of the Brora coal- 

 field. 



Fig. 3. A sectional view of part of the east coast of Ross and Cromarty, to explain 

 the relations of the lias, as seen at low-water near Shandwick and Ethic bays. 

 The second section from the left injig. 2. relates also to this tract, showing the 

 red conglomerate to be alone interposed between the lias and the primitive rocks. 



Fig. 4. A sectional view of part of the Coast of Skye near Portree. The small valley 

 of Beal inclosed by mountains of trap, is composed of cornbrash limestone, &c. 

 resting upon the inferior oolite. This limestone of Beal is traversed by fissures, 

 one of which is still occupied by compact zeolitic greenstone. 



