244 
MB.  E.  WE1HEBEH  OX  THE  MICROSCOPIC 
[May  i893r 
The  second  exposure  of'  the  M’enlock  Limestone  at  Ledburyr 
'which  I  have  selected  for  examination,  is  a  quarry  belonging  to- 
M.  A.  H.  Martin.  Esq.,  about  |  mile  distant  from  the  last-mentioned 
quarry,  on  the  road  to  Eastnor.  The  following  is  the  section : — 
Section  at  Martin’s  Quarry ,  Ledbury. 
[Top  of  Quarry.]  Approximate 
thickness, 
ft.  in. 
4.  Modular  Limestone  and  Argillaceous  Bed...  1  0 
3.  Crystalline  Blue  Limestone .  2  6  . 
2.  Blue  Limestone .  8  0 
1.  Massive  Blue  Limestone .  8  0 
[Base  of  Quarry.] 
It  will  be  observed  that  the  above  section  differs  materially  from 
that  given  of  Biddulph’s  Quarry  (see  p.  242).  This  is  partly 
accounted  for  by  the  fact  that  Martin’s  Quarry  is  not  so  extensively 
worked. 
Slides  from  the  Ledbury  Limestone  (2nd  Quarry). 
Bed  Xo.  1  is  a  massive  limestone,  made  up  chiefly  of  small  ossicles 
of  crinoids,  with  fragments  of  polyzoa,  valves  of  ostraeoda,  and  occa¬ 
sional  aggregations  of  Girvanella.  An  estimation  oi  the  residue 
insoluble  in  hydrochloric  acid  gave  2*9  per  cent.,  a  percentage  lower 
than  that  obtained  from  any  other  previous  estimation.  This  in¬ 
soluble  residue  is  made  up  of  grains  of  quartz,  numerous  small 
flakes  of  mica,  some  felspar,  zircon,  cryptocrystalline  siliceous 
aggregations,  and  a  quantity  of  pyrites. 
"Bed  Xo.  2  is  also  a  crinoidal  limestone,  but,  comparing  it  with 
Xo.  1,  the  remains  of  ostraeoda  and  small  aggregations  of  Girva- 
?z-e7?«-tubules  are  more  numerous.  The  bed  yielded  /  '3  per  cent,  of 
residue  insoluble  in  hydrochloric  acid,  made  up  of  minerals  similar 
to  those  mentioned  in  the  residue  from  the  previously  described 
bed,  but  there  is  less  pyrites. 
Bed  Xo.  3  is  more  crystalline  than  the  beds  below,  and  the  organic 
fragments  are  larger.  It  yielded  7‘6  per  cent,  of  insoluble  residue. 
The  calcareous  element  in  the  nodules  at  the  top  of  the  section  is  _ 
chiefly  derived  from  the  ossicles  of  crinoids,  some  few  fragments  of 
polyzoa,  and  aggregations  of  Girv anella pro blematica.  Some  of  the 
nodules  are  almost  entirely  calcareous  :  estimations  of  the  residue 
in  two  nodules  gave  respectively  2*7  and  9*5  per  cent.  The  residue 
contains  well-rounded  grains  of  quartz  (measuring  TO  millim.  in 
diameter),  crystals  of  zircon,  fragments  of  partially  decomposed 
felspar,  mica,  and  cryptocrystalline  siliceous  aggregations.  The 
very  fine  residue  is  made  up  of  a  vast  number  of  crystallites,  some 
of  which  give  brilliant  polarization-colours.  Among  them  are 
crystallites  of  quartz,  which  originate  from  the  breaking  up  of  the 
cryptocrystalline  siliceous  matter,  probably  during  the  process  oi 
boiling  the  residue  in  acid. 
