CLAYS    OF    PENOBSCOT    BAY    REGION,  MAINE.  429 
Depth.— The  depth  of  the  clay  deposits  varies  greatly,  being  in  general  greatest  on  the 
lowlands  and  least  on  the  higher  hill  slopes.  Depths  of  15  to  35  feet  are  very  common, 
and  well  records  in  some  cases  seem  to  show  a  depth  of  from  50  to  75  feet.  The  record  of 
a  well  at  the  brickworks  in  Thomaston  showed  45  feet  of  clay  resting  upon  limestone. 
Age  and  origin. — The  distribution  of  these  clays  with  respect  to  the  present  coast  line 
at  once  suggests  their  marine  origin,  and  such  a  conclusion  is  sustained  by  the  presence 
here  and  there  within  the  clays  of  the  shells  of  marine  animals.  The  clays  represent,  in 
truth,  old  clam  flats  formed  at  a  time  when  the  sea  level  was  considerably  higher,  relative 
to  the  land,  than  it  is  at  present.  Their  age  is  fixed  by  their  relation  to  the  deposits  made 
by  the  glaciers  which  covered  the  State  in  the  Pleistocene  period.  In  several  localities 
they  were  seen  to  overlie  deposits  of  glacial  bowlder  clay,  while  they  were  overlain  in  turn 
by  gravels  deposited  by  streams  flowing  from  the  melting  ice;  they  were  deposited  there- 
fore during  the  glacial  occupation.  The  streams  flowing  from  the  melting  glaciers  were 
heavily  laden  with  sediment;  the  coarser  portions,  the  gravels  and  sands,  were  deposited 
on  the  land  surface  or  in  the  ocean  close  to  the  shore,  but  the  finer  portions  were  carried 
farther  out  and  deposited  as  these  beds  of  marine  clay.  They  differ  from  the  clam  flats 
of  to-day  only  in  the  greater  rapidity  with  which  the  muds  were  deposited. 
Present  utilization  in  bricJcmalcing. — These  clays,  in  common  with  the  limestone  and 
much  of  the  granite  of  Maine,  possess  the  commercial  advantage  of  proximity  to  the  coast, 
where  the  manufactured  product  can  be  easily  and  cheaply  shipped  by  water.  Plants  for 
the  manufacture  of  common  brick  are  numerous  along  the  lower  portion  of  Penobscot  River; 
near  Damariscotta,  on  Damariscotta  River;  and  at  other  localities  within  the  area  under 
discussion.  Within  the  Rockland  quadrangle  there  is  only  one  company  engaged  in  brick 
manufacture;  this  is  the  Thomaston  Face  and  Ornamental  Brick  Company,  with  a  plant 
in  the  eastern  part  of  the  village  of  Thomaston.  This  plant  is  given  special  mention  because 
it  has  been  studied  by  the  writer  in  more  detail  than  other  plants,  and  because  its  modern 
equipment  seems  to  point  out  the  lines  to  be  followed  in  the  future  development  of  these 
deposits.  The  clay  at  this  brickyard  is  buff  gray  in  color  and  free  from  pebbles  or  con- 
cretions. As  it  occurs  in  the  banks  it  is  moderately  dry.  It  is  dug  by  steam  shovel  and 
transferred  in  small  cars  to  the  disintegrator,  where  it  is  dry  crushed.  The  clay  is  worked 
by  the  stiff-mud  process,  the  dry  material  being  carried  by  a  belt  from  the  disintegrator 
to  a  Raymond  pug  mill,  where  it  is  mixed  with  about  20  per  cent  of  water  and  fed  into  a 
Raymond  "999"  brick  machine  provided  with  an  automatic  down-cut  cutting  table.  This 
machine  has  a  capacity  of  8,000  to  12,500  standard  side-cut  bricks  per  hour.  The  bricks 
are  dried  in  a  10-tunnel  drier  having  a  capacity  of  75,000  bricks.  The  burning  is  done  in 
an  ordinary  scove  kiln.  The  bricks  show  an  air  shrinkage  of  one  thirty-second  of  their 
length  and  a  fire  shrinkage  of  one  sixty-fourth,  and  incipient  fusion  takes  place  at  about 
3,000  °F.  The  product  goes  principally  to  Massachusetts  and  is  shipped  by  rail,  although 
water  shipment  is  equally  feasible.  At  present  the  company's  product  does  not  correspond 
to  its  name,  for  its  whole  output  is  common  brick;  but  the  clay  is  considered  to  be  of  too 
high  a  grade  for  use  solely  for  this  purpose,  and  the  company  is  now  installing  machinery 
for  the  production  of  pressed  brick. 
Bull.  285—06 28 
