OLD  EED  SAJS’DSTONE  OF  THE  COUNTY  OF  WATEEFOED. 
339 
observation  without  observing  at  least  20  square  feet  of  the  plane,  and  in  many  cases 
the  surface  exposed  amounted  to  several  hundred  feet ; and  I may  add,  that  1 have  not 
omitted  a single  observation  made  by  me  from  the  discussion  contained  in  the  following 
Tables. 
Before  proceeding  to  the  discussion  of  the  observations,  I shall  give  my  reasons  for 
considering  the  planes  of  the  flaggy  structure  observed  by  me,  to  be  perpendicular  to 
the  lines  of  maximum  force.  I had  already  found  in  the  distorted  fossils  of  West  Water- 
ford conclusive  arguments  in  favour  of  the  view  put  forward  by  Mr.  Shaepe,  that  the 
planes  of  cleavage  were  perpendicular  to  the  line  of  maximum  force ; and  before  con- 
cluding that  the  platy  or  flaggy  structure  of  the  conglomerate  was  true  cleavage,  I was 
bound  to  show  that  its  planes  were  perpendicular  to  the  lines  of  greatest  force.  In  the 
absence  of  fossils  this  could  not  be  proved  in  the  usual  manner ; but  the  following  facts, 
ascertained  by  me,  leave  little  doubt  upon  this  important  point. 
Soon  after  I had  first  observed  the  flaggy  structure  of  the  cleavage  planes  of  the  con- 
glomerate, I found  that  this  structure  was  confined  to  planes  having  the  general  direc- 
tion of  the  system  (A),  already  noticed  in  speaking  of  faults,  although  it  was  occa- 
sionally observed  in  planes  parallel  to  the  system  (A').  I never  observed  the  flaggy 
structure  in  the  systems  C or  C' ; now,  as  the  line  of  greatest  force  in  a system  of 
elevated  beds  must  lie  in  the  vertical  plane,  or  nearly  so,  which  contains  the  direction 
of  the  dip  of  the  beds,  and  as  the  strike  of  the  beds  is  intermediate  between  the  systems 
A and  A',  it  is  evident  that  we  have  a close  approximation  to  Shaepe’s  law ; and,  on  the 
hypothesis  akeady  advanced,  of  two  systems  of  elevating  forces,  perpendicular  to  A and 
A'  respectively,  we  have  an  exact  conformity  to  this  laAV. 
I only  found  one  locality  in  the  whole  district  in  which  the  cleaved  flaggy  structure  had 
any  other  direction  than  either  A or  A',  and  in  this  locality  the  deviation  from  the  usual 
direction  of  cleavage  constitutes  a powerful  argument  in  favour  of  the  assertion,  that  the 
cleavage  structure  is  perpendicular,  or  nearly  so,  to  the  line  of  maximum  pressure. 
A little  north  of  Brownstown  Head,  on  the  side  of  Tramore  Bay,  near  a place  called 
Portoonaka  Beg,  and  close  to  the  Ordnance  Levelling  Mark  No.  1,  1841,  the  rocks  are 
beautifully  cleaved  with  the  peculiar  flaggy  or  platy  structure  already  so  often  described. 
The  cleavage  planes  have  a bearing  of  N.  12°  W.,  and  a dip  77°  E.  This  plane  corre- 
sponds with  the  system  C,  which  ought  to  be  a joint  and  not  a cleavage  plane ; but  it 
so  happens,  that  in  this  locality  there  is  considerable  local  contortion  in  the  bedding  of 
the  conglomerate  and  thin  shales ; and  throughout  the  entire  area,  in  which  the  flaggy 
cleavage  had  this  abnormal  direction,  I found  the  strike  of  the  beds  to  have  an  azimuth 
or  bearing  within  a few  degrees  of  that  of  the  cleavage.  The  bearing  of  the  beds,  in 
fact,  ranges  from  N.  5°  W.  to  N.  33°  W.,  dip  10°  N.  Thus  this  apparent  exception  to 
the  first  mechanical  law  of  cleavage  turns  out,  on  examination,  to  be  a remarkable  con- 
firmation of  it.  I should  add,  that  the  flaggy  structure  at  Portoonaka  Beg  divided  the 
rock  with  great  regularity  into  plates  of  4 or  5 inches  in  thickness  *. 
* My  attention  was  directed  to  this  exception  to  the  general  direction  of  the  flaggy  cleavage  by  the 
