"234 Proceedings of the Royal Irish Academy. 
structure of the country were pointed out, and as the further determi- 
nations herein recorded agree substantially with these directions, it is 
unnecessary to here recall these relations. It may, however, be noted 
that the two principal directions observed, JS". 14° 39' W. (with 52 
observed occurrences), and JN". 20° 5' E. (with 52 observed occurrences 
also), very distinctly represent the general directions of the coast line 
of Ireland between Carnsore Head and Dundalk Eay — that they re- 
present 15*3 per cent, of the whole of the observed directions of 
jointing, and thus fully bear out the proposition that the coast lines 
correspond in their general direction with the dominating systems of 
jointing observable in the neiglibourhood of the section of coast line 
considered. 
The strikes of the beds which crop out at Bray Head, as detailed 
in the accompanying Tables, show that those having an easterly direc- 
tion markedly predominate, and in the proportion of 60 to 14, or more 
than fourfold, the dips being to the north-west, or more or less westerly. 
Prom the Tables, it may be inferred that the predominating direc- 
tions of strike are— (I.) IS". 80° 15' E. ; (II.) K 55° 51' E. ; (III.) N. 
64° 31' E. ; and (lY.) 1^. 46° 36' E. 
I^ow, if these be compared with those easterly directions of joint- 
ing which present nearly similar values, as shown in the General 
Summary of Directions of Jointing (facing p. 256), it will be found 
that the relative frequencies stand as follows : — 
Strikes of Beds. 
(i.) 80°15'E. I (ii.) 55'51'E. | (m.) 64° 31' E. | (iv.) 46° 36' E. | (v.) 7r50'E. 
Directions of Jointing. 
(vii.) 8ri7'E. I (IX.) 53°33'E. | (vi.) 64°16'E. | (vii.) 46°24'E. \ (xi.) 71°20'E. 
It will be observed, that while the angular values of the two series 
approach closely, the degrees of frequency of occurrence as regards the 
values 64° and 46° differ so little, that taken in conjunction with other 
characteristics of these beds, the idea is suggested that there may be a 
relation existing between the beds on the one hand and the systems 
of jointing on the other. The continued examination of the rocks, and 
of their characteristics, led me, while engaged during two summers 
in taking the directions of jointing, to entertain this idea, and further 
examination of the question has brought me to the conclusion that, 
taking all the characteristics and conditions of the rocks of Bray Head 
into consideration, there are strong reasons for questioning the purely 
