MM. Wilson and Quilter — Rhcetic Section at Wigston. 415 



a piece of tracing paper draw two straight lines crossing each other 

 at right angles ; place this on the graticule in a position such that 

 one of the lines shall cut the two radii representing the given 

 directions of dip at points corresponding to their respective angles, 

 and the otlier lie over the origin, then the point of intersection will 

 give the direction and amount of the true dip. This method is 

 represented by the dotted line in Fig. 2. 



(J)) When both the given dips are less than the maximum angle 

 on the scale of tangents ; the said scale to be used throughout. 

 Take two pieces of paper whose edges are truly square, and lay one 

 with its edge along the radius representing the direction of one of 

 the given dips, and its corner at the point corresponding to the dip 

 in that direction, and lay the other in a corresponding position on 

 the radius representing the second direction of given dip, then the 

 intersection of the free edges will give the direction and amount of 

 the true dip. This method is represented by broken lines in Fig. 2. 



It will be seen that neitlier of these methods are applicable in 

 every case, but only when both the dips fall on to a single scale ; 

 but as the scale can be extended so as to embrace 70" of the quadrant 

 without becoming cumbrous, one or other method will be applicable 

 in every case likely to occur in practice. 



(3) Given the dip of a bed and the slope of the ground, to 

 determine the direction of its outcrop. The methods given under 

 (2) are to be employed, but in the reverse manner, viz. that described 

 under (2&), where the scale of cotangents has to be used, and that 

 under (2 a), where the scale of tangents must be used. 



If the direction of outcrop and of the slope of the ground be 

 given, the true dip can be obtained by fii'st determining the respective 

 angles of slope in the given directions of outcrop as described under 

 heading (1), and then combining these by methods (2 a) or (2 h) as 

 may be most suitable. Any other modification of these, which are 

 all that ordinarily occur in practice, are too obvious to necessitate a 

 detailed description. 



As regards problems falling under heading (4), viz. those connected 

 with the tilting of already inclined beds, Mr. Marker's method can 

 be followed, on the graticule I have described, by means of a piece 

 of tracing paper, but this method is cumbrous, presents no advantage 

 whatever over a direct and purely graphical solution, a matter of the 

 less consequence, as the interest of these problems is rather fanciful 

 than practical, the data required for their solution being seldom or 

 never obtainable. 



VI. — The EHiETio Section at Wigston, Leicestershire. 

 By E. Wilson, F.G.S., and H. E. Quilter. 



ALTHOUGH Eheetic rocks have already been noticed at one or 

 two points in Leicestershire, viz. at Leicester by Mr. W. J. 

 Harrison and between Barrow and Sileby by Mr. Etheridge,^ the 

 complete sequence of this series has not hitherto been observed in 

 that county. Very recently our attention has been directed to a 

 1 Quart. Jouru. Geol. Soc. vol. xxxii. p. 212 ; Geol. Mag. 1874, p. ■180. 



