PORTLAND    CEMENT    MATERIALS    NEAR    DUBUQUE,  IOWA.        227 
the  bluff.  In  several  lateral  ravines  and  valleys  large  enough  for  mill 
sites  the  Platteville  beds  are  favorably  situated  for  quarrying,  so  that 
the  broken  rock  may  be  loaded  into  a  mill  by  gravity.  Five  such 
localities  were  sectioned  and  sampled  in  detail.  In  the  order  of  their 
distances  from  Dubuque  they  are  as  follows:  (1)  Near  Zollicoffer 
Lake,  Peru  Township,  Iowa,  in  the  SW.  \  sec,  23,  T.  90  N.,  R.  2  E.; 
(2)  at  Spechts  Ferry,  Iowa;  (3)  near  Potosi  Station,  Wis.,  in  the  SE.  \ 
sec,  4,  T.  2  N.,  R.  3  W.;  (4)  about  1  mile  above  Waupeton,  Iowa,  in 
the  NE.  \  sec,  25,  T.  91  N.,  R.  1  W.;  (5)  near  McCartney,  Wis.,  in  sec, 
4,  T.  2  N.,  R.  4  W. 
CHARACTER   OF   MATERIALS. 
A  generalized  section  of  the  Platteville  includes  the  following  divi- 
sions : 
Generalized  section  of  Platteville  formation. 
Foot. 
4.  Limestone,  principally  in  thin  beds,  and  shale 10-15 
3.  Limestone,  fine  grained,  brittle,  and  thin  bedded 15-25 
2.  Limestone,  magnesian,  thick  bedded 15-25 
1.  Shale,  bluish,  sandy  in  places 1-5 
41-70 
Nos.  3  and  4  of  the  above  generalized  section  contain  the  purest 
limestone,  but  in  places  part  of  No.  2  also  is  found  to  contain  less 
than  5  per  cent  of  magnesium  carbonate,  The  following  table  gives 
the  stratigraphic  details  and  the  corresponding  chemical  analyses  of 
the  beds  at  two  localities  in  Iowa: 
