400 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
cessful  utilization  of  these  deposits  will  depend  very  largely  on  the  depth  of  clay  which  must 
be  stripped  off  before  the  limestone  is  exposed;  in  general  this  thickness  will  be  greater  than 
in  the  case  of  most  of  the  "veins  "  now  worked.  In  prospecting,  the  thickness  of  the  covering 
material  can  be  tested  readily  with  an  auger  before  digging  is  attempted:  if  too  great  tol 
warrant  its  removal  the  prospect  may  be  abandoned  in  favor  of  a  locality  where  the  covering 
is  not  so  deep.  In  general  this  thickness  is  least  in  the  highlands  and  greatest  in  the 
lowlands ;  hence  the  former  offer  the  most  promising  field  for  prospecting. 
PORTLAND   CEMENT. 
The  possibility  of  utilizing  the  clays  which  are  abundantly  developed  in  the  Rockland 
region  and  which  in  some  places  directly  overlie  the  limestone,  in  the  manufacture  of  Port- 
land cement  has  already  received  some  attention  from  quarry  operators  in  this  region. 
The  matter  is  rather  fully  discussed  by  the  writer  in  another  part  of  this  bulletin,  in  an 
article  on  "Clays  of  the  Penobscot  Bay  region  "  (pp.  428-431).  In  this  article  the  abundance 
and  availability  of  the  clays  are  brought  out.  It  may  be  stated  here,  however,  that  the  clays 
have  a  composition  which  suits  them  to  this  purpose,  and  that  if  the  clays  obtained  from 
stripping  could  be  utilized  in  this  way  limestone  beds  could  be  profitably  worked,  which 
otherwise  it  would  not  pay  to  uncover.  For  cement-making  purposes  in  the  utilization  of 
I  lie  clay  the  magnesian  limestones  arc  not  serviceable,  for  when  mixed  with  clay  they  do 
not  form  so  strong  a  cement  as  the  calcium  limes. 
Analyses  <>/  limestone  and  limes  from  Knox  County,  Me. 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
53.  L3 
42. 94 
74.36 
21.62 
53.  52 
45. 13 
98. 17 
Oarbonate  of  magnesium 
.09 
55.10 
96.31 
1.13 
f     1.42 
1     1.08 
85. 51 
9.25 
2.74 
1.61 
38.70 
4.59 
1.G1 
2.87 
1.06 
1.85 
1.04 
[       .90 
1.08 
15 
100.00 
100.00 
98.87 
a 100.  00 
99.94 
&100.00 
'99.77 
a  Total  includes  moisture,  etc.,  0.45  per  cenl . 
b  Total  includes  0.89  per  cent  loss  on  ignition, 
c  Total  includes  0.28  per  cent  of  organic  matter. 
T.  Magnesian  lime  from  Gay  Farm  quarry,  2  miles  southwest  of  Rockland  along  the  railroad. 
R.  S.  Edwards,  analyst. 
II.  Magnesian  limestone  from  quarry  operated  by  S.  P.  Dunton,  1  mile  southwest  of  Rockland. 
Specimen  taken  at  depth  of  18  feet.     F.  C.  Robinson,  analyst,  Brunswick,  Me. 
III.  Magnesian  limestone  from  Levensaler  qua  rry,  1  mile  north  of  Thomaston.     Deficiency  in  total 
may  indicate  error  in  figures. 
IV.  Magnesian  limestone  from  quarries  at  West  Warren.     S.  P.  Sharpies,  analyst,  Boston,  Mass. 
V.  "Soft-rock"  lime  from  eastern  pit  of  Rockland-Rockport  Lime  Company,  near  Rockland.     R.  S. 
Edwards,  analyst. 
VI.  "Hard-rock"  lime  from  Fred  Ulmcr  "hard-rock"  quarry,  west  of  Rockland.     R.  S.  Edwards, 
analyst. 
VII.  "Soft-rock"  from  McNamara  quarry,  Rockland.    F.  C.  Robinson,  analyst,  Brunswick,  Me. 
