Conglomerates, and Marls oj Devonshire. 
4] 
Each of the foregoing entries is the mean of several observa- 
tions, and, for faciUty of comparison, the directions are all entered 
in degrees from the north towards or through east. When cor- 
rected for magnetic declination, the entire series give an average 
dip of 5p towards N. 76^^ E. 
Measured in a direct line, the distance and bearing of Charton 
Bay from the Straight Point are respectively 16*5 miles and N 
69® E. Hence, since the general trend of the coast differs from 
the direction of the dip, the calculation is not quite so elementary 
as in the foregoing case, nevertheless it presents no difficulty. For 
let N S (Fig. 2) be a north-and-south line, S the Straight Point, 
C Charton Bay, and S B the direction in which the strata dip. 
Join S C, and from C draw C B perpendicular to SB, then 
CB represents the strike of the formation, SB its horizontal 
extension in the direction of the dip, and S C the general line of 
the coast. Then, since S C has a bearing of N 69*^ E, and 
SB of N 76^^ E, the angle BSC, which they contain, is 7^'^ 
(=76i— 69); and, as B is a right angle, SB =SC X cos. 
Z.BSC = 16-5 miles X cos. 7^*^ = 16-3 miles; a result so 
very near the length of the coast line that the calculation 
might have been omitted without entailing appreciable error. It 
appears then that the beds between the Straight Point and 
Charton are equivalent to a section 16-3 miles in length, and 
composed of strata dipping at an angle of 5^*^ in the direction of 
the section : data which, for this part of the formation, give a 
thickness of fully 1*5 mile. If to this we add the calculated 
thickness (4 miles) of the rocks from the Straight Point south- 
wards, we obtain a total of 5*5 miles for the entire formation as 
developed in our south-eastern cliffs. 
It is not improbable that the following objections may be made 
here : 
1 . That deductions should have been made for the important 
breaks which occur in the continuity of the formation. 
F 
