Yol.  49.] 
THE  BASE  OF  THE  KEUPER  IX  DEVON. 
79 
2.  The  Base  of  the  Keeper  Formation  in  Devon.  By  the  Rev.  A. 
Irving,  B.A.,  D.Sc.  (Bond.),  F.G.S.  (Read  November  23rd, 
1892.) 
In  my  two  previous  communications  to  the  Society  on  the  Devon 
Red  Rocks1  I  have  recognized  the  insufficiency  of  the  evidence 
then  available  for  drawing  a  clear  and  well-defined  boundary-line 
between  the  Keuper  and  the  Bunter  in  the  country  lying  west  of 
Sidmouth ;  and  now  that  the  Permian  age  of  the  lower  breccia- 
series  has  been  definitely  recognized  by  the  Director-General  of  the 
Geological  Survey  in  his  Presidential  Address  of  last  February,2  this 
may  be  said  to  be  the  only  remaining  dubious  point  of  importance 
in  our  new  classification  of  the  Red  Rocks  of  Devonshire,  and  their 
correlation  with  the  Permian  and  Trias  of  the  Midlands  and  the 
Severn  country.  The  difficulty  I  found  in  drawing  the  basement¬ 
line  of  the  Keuper  in  my  1888  paper  seems  to  have  been  felt  by 
Mr.  Strahan  in  the  Cheshire  area,3  for,  after  discussing  the  evidence 
on  both  sides,  he  seems  inclined  to  think  that  there  are  about  as  good 
reasons  for  drawing  the  basement-line  of  the  Keuper  at  the  bottom 
of  the  4  Waterstones  ’  (as  I  did  in  Devon  four  years  ago)  as  for 
drawing  it  at  the  base  of  the  4  Lower  Keuper  Sandstones  ’  of 
Prof.  Hull.  Briefly,  these  seem  to  resolve  themselves  into  two : — 
(1)  overlap  in  places  of  the  Waterstone  series;  (2)  lithological 
similarity  of  the  Keuper  basement-beds  to  the  mottled,  current- 
bedded  soft  sandstones  of  the  Upper  Bunter — a  similarity  which, 
as  I  showed  in  my  paper  of  last  year,  is  even  stronger  than  he  has 
made  it  out  to  be  in  Cheshire,  for  the  beds  in  the  coast-section  north¬ 
east  of  Otterton  Point.  The  present  communication  will  perhaps 
serve  to  show  that  in  the  Devon  area,  where  no  signs  of  overlapping 
have  been  recorded  at  this  stage  of  the  Trias,  there  is  a  great  prepon¬ 
derance  of  evidence  in  favour  of  the  lower  of  these  two  horizons 
being  accepted  as  marking  the  true  downward  limit  of  the  Keuper 
formation. 
In  my  last  paper  (published  in  Feb.  1892),  at  the  suggestion  of 
Prof.  Hull  I  definitely  accepted  the  breccia,  which  is  clearly  marked 
on  the  left  bank  of  the  Sid  at  Sidmouth,  for  the  base  of  the 
Keuper — as  that  formation  is  exhibited  in  its  entirety  in  the  coast- 
section  from  Sidmouth  eastwards  to  Seaton  :  but  I  had  not  then 
satisfactory  data  for  determining  a  similar  basement-line  through 
the  country  lying  to  the  west  of  Sidmouth  and  between  the  valleys 
1  Quart.  Journ.  Geol.  Soc.  vol.  xliv.  (1888)  pp.  149-163;  and  vol.  xlviii. 
(1892)  pp.  68-77. 
2  I  can  scarcely  see  how  I  have  ’  followed  Murchison,’  who  merely  gave  an 
opinion  on  the  value  of  the  correlation  of  the  Devon  breccias  with  the  Itoth- 
liegendes  of  Germany  by  Buckland  and  Conybeare.  My  correlation,  like 
theirs  (of  which  I  was  ignorant  at  the  time),  was  based  on  direct  knowledge 
acquired  in  the  field,  as  my  papers  plainly  show. 
3  ‘On  the  Lower  Keuper  Sandstone  of  Cheshire,’  Geol.  -  Mag.  for  1881, 
pp.  396  et  seq. 
