[ 333  ] 
XVII.  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 
HaughtojST,  M.A.,  F.G.S.,  Fellow  of  Trinity  College,  and  Professor  of  Geology  in 
the  University  of  Dublin.  Communicated  by  Professor  Tyndall,  F.R.S. 
Eeceived  January  19, — Bead  January  21,  1858. 
CoNTEjSTTS  ; — 
1.  Description  of  the  District. 
2.  Daults. 
3.  Joint  Planes. 
4.  Cleavage  Planes. 
5.  Observations  Tabulated. 
1.  Desm'i'ption  of  the  District. 
In  a paper  published  by  me  in  the  Philosophical  Magazine  I have  stated  my  views  in 
relation  to  cleavage  structure  of  rocks,  considered  in  connexion  with  the  distortion  of 
fossils,  and  arrived  at  the  following  results : — 
1st.  That  the  cleavage  is  in  planes  perpendicular  to  the  lines  of  maximum  pressure. 
2nd.  That  the  distortion  of  fossils,  in  any  plane  of  bedding,  depends  on  the  angle 
made  uith  the  plane  of  cleavage,  by  the  plane  of  bedding  considered ; increasing  with 
that  angle,  according  to  a lawy  which  I have  defined  in  the  paper  itself. 
During  the  course  of  the  past  summer  (1857),  I was  enabled  to  study  the  physical 
structure  of  the  Old  Red  Sandstone  conglomerate  of  the  county  of  Waterford ; a rock 
eminently  unsuited  to  the  production  of  cleavage,  or  indeed,  any  other  phenomena,  by 
the  influence  of  polar  forces ; and,  in  the  course  of  my  observations,  I arrived  at  facts 
which  appear  to  me  to  be  inexplicable  on  any  other  than  a mechanical  theory.  As  the 
facts  themselves  are  worthy  of  record,  whatever  opinion  may  be  formed  of  the  inferences 
I have  deduced  from  them,  and  as  the  observations  on  which  they  depend  (345)  are  more 
numerous  than  usual,  and,  as  I believe,  carefully  made,  I have  felt  myself  justified  in 
bringing  them  under  the  notice  of  the  Royal  Society,  and  thus  placing  them  on  record. 
The  Old  Red  Sandstone  conglomerate  of  the  South-east  of  the  county  of  Waterford 
extends  in  an  E.N.E.  and  W.S.W.  direction,  from  Creadan  Head,  Waterford  Harbour, 
to  Brownstown  Head,  east  of  Tramore  Bay,  a distance  of  7f  miles;  and  in  a perpen- 
dicular direction,  its  greatest  breadth  is  about  3^  miles.  The  average  bearing,  or  strike 
of  the  beds  of  which  it  is  composed,  is  parallel  to  the  line  of  greatest  length,  and  it  has 
throughout  a dip  or  inclination  towards  the  sea,  ranging  from  5°  to  20°.  Its  lowest 
portion  consists  of  some  200  feet  of  solid  conglomerate,  surmounted  by  varying  beds  of 
red  sandstone  and  shale  of  every  degree  of  mechanical  fineness  and  subdivision.  The 
* Philosophical  Magazine,  Pourth  Series,  vol.  xii.  p.  409. 
