108 



January 21, 1858. 



Dr. J. D. HOOKER, V.P., in the Chair. 

 The following communication was read : 



" On the Physical Structure of the Old Red Sandstone of the 

 County of Waterford, considered with relation to Cleavage, 

 Joint Surfaces, and Faults." By the Rev. SAMUEL HAUGH- 

 TON, Fellow of Trinity College, Dublin, and Professor of 

 Geology. Communicated by Dr. TYNDALL, F.R.S. Received 

 January 19, 1858. 



After describing the general features of the district and giving his 

 reasons for selecting it, the author proceeds to give a detailed account 

 of the faults, joint surfaces, and cleavage planes, 345 in number, 

 observed by him during the course of his survey. 



The faults are nineteen in number and reducible to two pairs of 

 rectangular systems. The bearings of these systems are E. 7 30' N. 

 and E. 34 22' N. The other faults, which form nearly right angles 

 with the preceding and may be called Conjugate Faults, have the 

 following bearings, N. 3 45' W. and N. 33 24' W. 



The author considers that the existence of two systems of conju- 

 gate faults indicates two distinct systems of upheaving force in the 

 district ; a supposition which is strongly confirmed by the fact that 

 the average strike of the beds is E. 10 46' N., a direction inter- 

 mediate between those of the systems of faults. He then demon- 

 strates from 345 observed planes, that the systems of joint and 

 cleavage planes are also conjugate systems, reducible to four, of which 

 two are identical with the two conjugate systems of faults already 

 established. The average observed angles between the conjugate 

 axes of these four systems of planes are 89 1 1', 91 52', 91 20', and 

 90 30' respectively; and the bearings of their cleavage planes are 



