O'Eeilly — On Jointing in jRocIcs about Buhlin Bay, S^c. 309 



wliicli, for the reason previously cited, is a fair approximation to the 

 theoretical angle of 40°. (This direction of 30° 08' E. is very re- 

 markahle at Ireland's Eye.) 



Nearly similar intervals occur between the directions 89° 45' "W"., 

 50° 12' W., and 9° 27' W. : thus we have 39° 33', and 40° 45' as 

 these intervals; while the mean of the four values, 42° 15', 39° 35', 

 39° 33', and 40° 45', is 40° 32', which sufficiently represents the 

 angular relation adopted by the theory. 



It would be easy to multiply the number of cases of intersections 

 at angles closely approximating to the values 80°, 70°, 40° ; but there 

 is a simpler and more direct proof of the correspondence of the actual 

 lines with the theoretical : it is, that the Grreat Circles already men- 

 tioned correspond in a marked manner with actual lines of direction, 

 such as main jointing, river valleys, and mountain ridges, and that 

 from them may be derived most, if not all, the principal coast line 

 directions. If it were possible to have the main lines of jointing 

 carefully laid down for the whole of Ireland, it would be still more 

 easy to multiply cases of intersection at the angles indicated, since it 

 is fair to presume that the conclusions to be drawn from their corre- 

 lation with the coast lines, and the Grreat Circles already cited, would 

 not be less in accordance with the theory than those arrived at for the 

 neighbourhood of the Bay of Dublin. 



