18 



Mr. Hopkins on the Structure of the 



till, about Seal, it amounts to 70° or 80", being everywhere exactly north. This 

 dip carries the chalk rapidly down under the tertiary beds, leaving a narrow and 

 lofty ridge of chalk. The basseting edge of the gault occupies a narrow strip at 

 the foot of the escarpment, but the upper beds of the lower greensand occupy a 

 far larger proportionate surface. This is owing to the fact of their inclination being 

 very much less than that of the chalk, as represented in the annexed diagram. 



4. Tertiaries. 

 3. Chalk. 

 2. Gault. 

 1, 1'. Lower Greensand. 



The section through Crookbury Hill is similar to the one here given, except that 

 the lower greensand rises to a greater height than in the instance before us. This 

 elevation shows that the beds of that formation must have a considerable dip from 

 thence to the Hog's Back ; and this dip, though much less than that of the chalk, 

 is considerably greater than that of the greensand beds further south, which would 

 otherwise have occupied a very much smaller space in that direction than they 

 actually occupy. This change in the magnitude of the dip probably takes place 

 near the hill, but I saw no distinct reason to suppose that the hill is anticlinal, as 

 Mr. Martin appears to think it. The same observation will apply I think to the 

 whole of his Pease Marsh antichnal line, east of the hill in question. The proper 

 line of flexure (as previously defined) from the western extremity of the Hog's 

 Back to the east of Puttenham is unquestionably very near the foot of the escarp- 

 ment ; and by Guildford, it runs not far south of St. Catherine's Hill, and close 

 under the hill above Shalford, and the prominent point on which Margaret's Chapel 

 is situated. At Guildford the incUnation of the chalk, though still very considerable, 

 is much less than it is farther to the west ; but here it is continued without dimi- 

 nution to the first escarpment of greensand, constituting the hills just mentioned. 

 That of Margaret's Chapel attains a higher elevation than the chalk escarpment, as 

 represented in the annexed section, though it is not much more than a quarter of a 



SECTION THROUGH MARGARET'S CHAPEL HILL, NEAR GUILDFORD. 



4. Tertiaries. 



3. Chalk. 



2. Gault. 



1, 1.' Lower Greensand. 



