430 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
Chemical  composition. — In  the  table  below  are  given  analyses  of  elays  from  three  loc  | 
ities  within  the  Rockland  quadrangle: 
Analyses  of  clays  from  Knox  County,  Me. 
Silica  (Si02) 
Titanium  oxide  (TiO-z) 
Alumina     \1.<  > 3) 
Ferric  iron  (F(>203)  — 
Ferrous  iron  (FcO) . . . 
Lime  (CaO) 
Magnesia  (MgO) 
Soda  (Na20) 
Potash  (K20) 
Water  (a1  107°  C.) 
Water  (on  ignition) ... 
Carbon  dioxide  (COj) . 
62.  80 
.87 
17.  30 
4.40 
«  2.  00 
.88 
L.  58 
1.48 
3.  05 
1.31 
4.39 
None 
100.  12 
02.33 
.79 
17.70 
5.19 
"  1.  72 
1.00 
1.53 
2.38 
2.41 
1.  11 
3.81 
Nolle. 
19.  : 
7. 
1.1 
i.i 
99. 97 
'.17. 
a  The  values  reported  tor  ferrous  iron  are  questionable  on  account  of  the  presence  of  a  small  amoui 
of  organic  matter. 
1.  Clay  from  brickyards  al  Thomaston,  Me.    W.  F.  Schaller,  analyst,  U.  S.  Geological  Survey  laboq 
lory. 
L'.  (lay  from  Haydeil  Point,  near  South  Thomaston.  Me.  W.  F.  Schaller,  analyst,  U.  S.  Geologica 
Survey  laboratory. 
3.  Clay  on  the  property  of  the  Rockland-Rockport  Linn  Company,  near  Rockland,  Me. 
Although  these  three  samples  were  taken  at  localities  several  miles  distant  from  eacl 
Other  their  analyses  are  closely  similar,  a  fact  which  suggests  that  throughout  this  region 
the  clays  possess  a  rather  uniform  composition.  From  the  chemical  analyses  and  also 
from  a  microscopic  examination  it  i>  seen  that  these  are  not  what  could  be  called  "sandy" 
clays,  though  the  amount  of  sand  i-  sufficient  so  that  none  need  he  added  in  mixing  for 
brickmaking.  Ries,a  from  a  consideration  of  several  hundred  analyses  of  brick  clays,  finds 
that  the  silica  percentages  range  from  34  to  nearly  91  per  cent,  with  an  average  of  about 
59  per  cent.  The  Penobscot  Bay  specimens  are  only  slightly  above  this  average.  The 
percentage  of  iron  is  fairly  constant  and  is  sufficient  to  give  the  burned  bricks  a  bright-red 
color.  The  average  for  brick  clays  is  about  5  per  cent.  The  absence  of  calcium  carbonate, 
shown  by  the  absence  of  C02  in  analyses  1  and  2,  is  a  desirable  feature,  as  is  also  the  rather 
high  percentage  ol  alkalies.  The  latter  are  the  most  important  fluxing  constituents  of  the 
clay,  and  on  burning  serve  to  bind  the  grains  together.  If,  as  in  this  case,  their  quantity 
is  large,  the  brick  may  be  burned  at  a  lower  temperature  than  otherwise. 
Future  utilization  in  brickmaking. — In  the  opinion  of  the  writer  the  high  quality  of  these 
clays,  their  abundance,  and  their  favorable  situation  on  the  seaboard,  warrant  a  much 
more  extensive  commercial  development.  A  factor  worthy  of  consideration  in  this  connec- 
tion is  the  possibility  of  utilizing  in  brick  manufacture  some  of  the  water  power  of  the 
coastal  region.  At  a  number  of  places  along  this  part  of  the  coast  long  tidal  estuaries 
penetrate  inland  for  considerable  distances  and  are  usually  much  contracted  in  width  at 
one  or  more  places.  Through  these  narrow  portions  the  tide,  both  at  ebb  and  at  flow, 
surges  with  great  power,  which,  if  harnessed,  could  be  made  to  serve  a  variety  of  useful 
purposes.  It  is  along  such  estuaries  that  the  marine  clays  are  best  developed,  and  the 
possibility  of  the  application  of  such  power  in  the  manufacture  of  brick,  especially  of  pressed 
brick,  naturally  suggests  itself.     A  good  example  is  the  case  of  Weskeag  River,  with  nanows 
a  Rics,  Heinrich,  The  clays  and  clay  industry  of  New  Jersey:  Final  rept.  State  geologist  New  Jersey, 
vol.  C,  p.  55. 
