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EXPOSITION  AT  VIENNA.

Y.  Materials  eor  Pottery.
The  materials  iised  in  the  manufacture  of  pottery  were  exhibited
  in  several  of  the  sections,  notably  from  Japan.  Much
more  attention  has  been  given  abroad  to  explorations  for  clays
and  to  their  examination  chemically,  and  experimentally  in  the
furnace,  than  in  the  United  States.  Collections  are  made
under  government  auspices  to  illustrate  and  promote  the
potter’s  art.  The  Museum  of  Practical  Geology  in  London
contains  very  full  collections,  illustrating  the  qualities  of  the
clays  and  plastic  strata  of  Great  Britain,  selected  with  a  view
to  their  applicability  to  ceramic  manufactures.  There  are
over  one  hundred  and  twenty-three  localities  represe.nted  in
the  series,  and  each  set  of  specimens  contains  six  examples.
They  are  all  arranged  in  geological  sequence,  commeuciug
with  the  newer  deposits  and  ranging  downwards.
As  already  stated  in  the  general  sui-vey,  there  is  no  lack  in
the  United  States  of  suitable  clays  for  pottery.  They  are
widely  distributed,  not  only  in  recent  deposits  along  the
granite  ranges  of  the  country,  but  in  the  tertiary  and  older
formations.  They  result  from  the  gradual  disintegration  and
decay  of  feldspathic  rocks.  This  decay  and  softening  is  seen
on  a  grand  scale  in  the  Southern  States,  but  at  the  North  the
decayed  portions  appear  to  have  been  removed  by  the  mcchanical
  force  of  ice.  The  antiquity  of  the  decomposition  and
its  great  extent  in  past  geological  ages,  has  been  pointed  out
by  Prof.  T.  Sterry  Hunt,  who  believes  it  to  have  been  accomplished
  in  great  part  by  an  atmosphere  of  carbonic  aeid,  aided
by  warmth  and  moisture.  He  connects  it  with  the  slow  purification
  of  the  atmosphere  which  has  been  in  progress  from
very  early  times.  The  alkalies,  lime  and  magnesia,  set  free
by  the  decomposition,  absorbed  the  carbonic  acid,  and  carried
in  solution  to  the  ocean,  gave  riso  to  limestones,  dolomites
and  common  salt.
In  New  England  the  principal  known  deposits  of  clay  suitable ­
  for  potters’  use,  are  along  the  western  base  of  the  Green
Mountains  in  tertiary  deposits.  They  have  been  worked  at
Brandon,  and  Monkton,  in  Vermont.  From  the  former  place
quantities  have  been  taken  for  fire-brick  and  for  putting  into