272 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 25, 



Hillock of quartz with summit of axis-plane thrown over 

 to the south. 



flexures, produced apparently by the weight of the superincum- 

 bent mass on the lower part when in a pasty state. 



Proceeding in our southern course, a second short east and west 

 range is met with, formed of three principal hills, of which the first 

 (960 feet high) is anticlinal with a broken summit. The second 

 hill is also anticlinal, with horizontal strata on its broad summit, 

 showing traces of curvature towards the edges : the inclination is 

 rather greater on the south than on the north side. Between this 

 second and third hill there is an anticlinal hillock, the strata on its 

 south side dipping at an angle of 59°, and its summit folded as repre- 

 sented in the diagram. 3. 

 We here see that the 

 upper part of the axis- 

 plane, to use a conve- 

 nient term of the Pro- 

 fessors Rogers, has 

 been pushed over to 

 the south. Throughout 

 the third hill the strata 

 at first appear all con- 

 formable, dipping from 50° to 55° N. by E.; but on examination I 

 found a small portion, only fifty yards across in the line of the dip, 

 inclined at an angle 



of 26° southward; and ^' 



the tips of the adjoin- 

 ing beds were, as re- 

 presented in the dia- 

 gram, abruptly arched. 

 Hence this hill has been 

 formed by a mass of 

 strata doubled on them- 

 selves, with the axis-plane thrown quite over to the south, as was the 

 case with the upper part alone in the above-mentioned hillock. 



I have described this hill more particularly on account of a curious 

 appearance presented by the arched parts of the strata. The arching 

 has been so abrupt, that in some loose fragments, presenting a natural 

 section, the radius of the curve is seen to be only seven feet. The 



end section of one such fragment, twelve feet in length, is accurately 



given in the following woodcut (No. 5), but allowance must be made 



for a little displacement from an open fissure crossing it. In this 



case the convex or outer and exposed 



surface is remarkably even and smooth ; 



it is traversed in the line of the axis 



of curvature by numerous parallel 



veins, from the tenth to the twentieth 



of an inch in thickness, and from half 



an inch to two inches apart from each 



other : these often thin out at both 



ends, but where one thins out, another 



commences either a little above or 



below. The veins are partially filled 



by transverse threads of quartz very 



strata of quartz dipping 50° to 55° north, with a fold in the 

 middle, only fifty yards across. 



5. 



Open fissure. 



6 feet 9 inches 



Base of an arched fragment of quartz. 



