124 
Farming  of  Gloucestershire. 
It  contains  37  beds  of  coal,  altogether  amounting  to  78  feet,  whilst  the 
separate  beds  range  from  a few  inches  to  3 or  4 feet,  and  in  single  in- 
stances amount  to  5 and  G feet. 
The  coal-measures  in  the  central  parts  of  Dean  Forest  are  2310  feet 
deep  (see  Section),  of  which  the  upper  shales  amount  to  1255  feet,  and  the 
central  sandstones  to  about  1055  feet:  the  lower  shales  are  wanting. 
There  are  27  beds  of  coal,  making  an  aggregate  thickness  of  40  feet  8 
inches.  These  seams  vary  from  1 or  2 inches  to  2 or  3 feet,  and  in  one  in- 
stance (the  Coleford  High  Delf)  to  5 feet. 
At  Bowlsden,  near  Newent,  a bed  of  coal  5 feet  6 inches  thick  was  for- 
merly worked  in  a small  tract  of  coal  strata,  which  descend  eastward 
under  the  new  red-sandstone  and  oolites  up  the  valley  of  the  Severn ; but 
even  here,  though  found  at  the  depth  of  only  T20  feet,  the  works  were 
abandoned  on  account  of  the  bad  state  of  the  roof  above  the  coal. 
The  great  and  valuable  deposits  of  argillaceous  iron-ore  in  the  coal- 
measure  of  South  Wales  and  Shropshire  do  not  extend  into  this  county, 
though  one  unimportant  bed  of  ironstone  occurs  in  the  central  and  highest 
part  of  the  Dean  Forest. 
The  coal  districts  are  to  a very  small  account  under  the  dominion  of  the 
plough,  but  it  may  be  inferred  that  where  so  many  and  various  substrata 
come  to  the  surface  in  a small  space,  there  must  be  many  tracts  of  good 
soil.  A country  which  has  produced  oak  timber  for  so  many  ages  would 
surely  grow  corn. 
7.  New  Red-Sandstone. — This  general  term  is  applied  to  a formation 
whose  prevailing  colour  is  red,  from  the  diffusion  of  peroxide  of  iron,  and 
which  in  the  south  of  England  immediately  succeeds  the  coal.  It  appears 
not  to  have  been  formed  till  the  palaeozoic  rocks  were  consolidated  and  up- 
heaved,  for  its  lowest  beds  are  generally  a conglomerate  formed  of  frag- 
ments from  the  adjacent  rock,  cemented  together  by  carbonate  of  lime, 
with  occasionally  so  much  magnesia  as  to  have  acquired  the  name  of  mag- 
nesian conglomerate,  and  to  be  considered  to  be  the  equivalent  of  the 
great  magnesian  limestone  of  the  north.  In  this  district  the  conglome- 
rates seem  rather  to  point  at  the  coast-line  of  the  new  red-sandstone. 
Section  by  New  Road  from  Clifton  to  the  Hotwells. 
In  the  Bristol  district  the  magnesian  conglomerate  is  succeeded  by  red 
marls,  very  little  sandstone  intervening ; but  in  the  vales  of  Gloucester  and 
Worcester  the  red-sandstone  forms  a lower  division  of  great  thickness, 
whilst  the  marls  above  contain  the  sulphate  of  lime,  salt-mines,  and  brine 
springs,  for  which  Droitwich  and  Northwich  are  famous.*  At  Aust  Cliff, 
* On  the  soils  above  the  saliferous  marls  many  plants  have  been  observed  which, 
requiring  salt  or  soda  in  large  quantities,  usually  grow  only  by  the  sea. — (See  Ure’s 
Dictionary  of  Arts,  & c.,  ‘ Salt.’)  Mr.  Buckman  lias  suggested,  with  great  probability, 
that  these  plants  were  introduced  there  when  the  Severn  was  an  arm  of  the  sea. — 
Tran.  Brit.  Assoc.,  1817.  ‘ Straits  of  Malvern,  1819.’ 
