PIEDMONT  PLATEAU  AND  PORTIONS  OF  THE  APPALACHIANS.      657 
small  and  the  gneiss  apparently  has  a  slight  roll.    The  gneissic  rock  is 
here  distinctly  bedded. 
Frazer,9  in  1880,  includes  in  the  post-Eozoic  series  of  Lancaster 
County  calcareous  argillites,  nacreous  slates,  hydromica  schists,  Chikis 
quartzite,  and  chloritic  series.  In  the  Eozoic  series  is  placed  the 
mica  schist  and  gneiss  belt.  Between  this  series  and  the  previous  one 
there  is  no  certain  evidence  of  unconformity,  the  transition  from 
one  rock  to  the  other  being  gradual  and  the  line  between  them  dif- 
ficult to  define. 
Frazer,10  in  1880,  states  that  the  chloritic  series  pass  into  the  Peach 
Bottom  slates  within  a  breadth  of  a  few7  hundred  yards,  and  equally 
abruptly  into  chlorites  again,  and  finally  into  greenish  chloritic 
quartzite,  in  all  respects  like  those  of  the  South  Mountain.  If  the 
Peach  Bottom  slates  are  of  Hudson  River  age,  as  supposed,  a  diffi- 
culty is  here  presented. 
Hall  (C.  E.),11  in  1881,  describes  Philadelphia  County  and  the 
southern  parts  of  Montgomery  and  Bucks.  The  schistose  rocks  are 
placed  in  the  three  belts  as  divided  by  Rogers,  but  there  is  an  inter- 
mediate belt  between  the  first  and  second  belts  of  Rogers.  The  first 
belt  is  made  up  of  gray  schistose  gneiss,  composed  of  quartz,  feldspar, 
and  brown  or  black  mica,  with  occasional  garnets,  interlaminated 
with  occasional  beds  of  black  hornblendic  slate  and  fine-grained 
sandy  gneiss.  The  second  belt  is  characterized  by  serpentine,  soap- 
stone,  silvery  micaceous  garnetiferous  schists.  And  light-colored  thin- 
bedded  sandy  gneisses,  with  disseminated  light-colored  mica  in 
minute  flakes.  The  third  belt  is  composed  chiefly  of  quartz,  feldspar, 
and  hornblende.  The  beds  are  often  massive,  but  usually  have  thin 
bands  of  mica  or  hornblende  through  them.  They  are  syenitic  and 
gneissic  granites  or  granitic  gneisses  in  which  is  found  a  peculiar 
variety  of  blue  quartz.  The  prevailing  northward  dips  of  the  schists 
and  gneisses  of  the  first  and  second  belts  do  not  hold  for  the  third. 
The  Primal  sandstone  (Potsdam),  wherever  it  occurs,  invariably 
rests  upon  the  rocks  of  the  third  belt,  and  its  sandstones  and  conglom- 
erates are  invariably  composed  of  debris  from  this  belt,  and  in  it  is 
found  not  a  single  flake  of  mica,  quartz,  or  other  material  which  can 
belong  to  the  first  or  second  belts.  For  considerable  distances  the 
Primal  rocks  are  found  between  the  third  belt  and  the  schists  of  the 
second  belt.  At  the  Schuylkill  the  rocks  of  the  first  and  second  belt 
rest  upon  and  against  the  rocks  forming  the  third  belt.  The  third 
belt  is  regarded  as  Laurent  ian  and  the  first  and  second  belt  are  as- 
signed a  position  above  the  Primal  Potsdam  sandstone  and  the  Auro- 
ral limestone.  In  the  midst  of  the  roofing  slates  of  Susquehanna 
River  occur  Hudson  River  fossils,  and  the  first  and  second  belts  are 
referred  to  or  above  the  Hudson  River  group,  while  the  third  belt  is 
referred  to  the  Laurentian. 
55721— Bull.  360—09 42 
