LAKE    SUPERIOR   REGION.  113 
to  leave  no  doubt  of  their  common  origin  and  identity  of  age.  In 
general  the  beds  of  conglomerate  increase  in  frequency  in  nearing  the 
trap.  The  sandstone  does  not  repose  directly  on  the  trap,  but  almost 
invariably  a  bed  of  coarse  pebble  rock  is  found  interposed  between. 
A  trap  breccia  found  at  Cushman's  seems  to  be  a  product  of  the  inter- 
fusion of  trap  and  sandstone.  Compact  quartz  rock  or  jasper  occurs 
abundantly  in  mountain  masses  in  the  Porcupine  Mountains. 
Whitney  describes  a  deposit  of  limestone  which  rises  to  a  height  of 
about  300  feet  above  the  general  level  of  the  country  near  L'Anse. 
The  limestone  is  indistinctly  stratified  and  dips  from  zero  to  30°  at 
various  points.  At  certain  places  it  contains  numerous  fossils,  but 
the  greater  part  of  the  rock  seems  to  be  destitute  of  them.  Among 
the  fossils  are  encrinites,  orthoceratites,  and  others.  The  country 
around  is  low  and  swampy,  but  the  indications  are  for  nothing  but 
sandstone  horizontally  stratified.  As  the  limestone  is  apparently 
inclined  at  an  angle  of  30°,  it  seems  evident  that  this  is  the  oldest 
rock,  though  it  can  not  be  denied  that  the  stratification  of  the  lime- 
stone is  very  obscure  and  in  some  places  it  appears  to  lie  nearly  hori- 
zontal. On  the  data  collected  the  author  feels  unwilling  to  pronounce 
which  is  the  older  formation. 
Foster,16  in  1850,  finds  at  Copper  Harbor  the  junction  of  the  trap 
and  conglomerate.  At  the  point  of  contact  the  trap  is  vesicular,  but  a 
few  feet  distant  it  is  amygdaloidal.  The  conglomerate  is  made  up  of 
rounded  pebbles  of  greenstone,  porphyry,  and  rarely  granite,  ce- 
mented by  a  dark  iron  sand,  with  carbonate  of  lime  among  the  inter- 
stices. Near  the  Quincy  mine  the  conglomerate,  or  rather  sandstone, 
containing  quartz  pebbles,  forms  the  gorge  of  the  stream  below  the 
falls,  and  differs' essentially  from  that  on  the  northern  slope  of  Ke- 
weenaw Point.  Between  the  sandstone  and  compact  trap  is  a  bed  of 
red  slaty  trap  associated  with  amygdaloid.  At  L'Anse  sandstone  and 
conglomerate  are  found  resting  unconformably  upon  chlorite  slate, 
novaculite,  or  siliceous  slate.  In  the  Chippewa  land  district  are 
found  granite,  gneiss,  hornblende,  chlorite,  argillaceous  slates,  and 
magnetic  iron  ore.  In  sec.  1,  T.  46  N.,  R.  30  W.,  is  a  bed  of  quartz 
composed  of  rounded  grains,  with  small  specks  of  iron  disseminated, 
and  large  rounded  masses  of  the  same  material  inclosed,  constituting 
a  conglomerate.  This  bed  is  15  feet  in  thickness  and  is  succeeded 
again  by  a  specular  iron  exposed  in  places  to  a  width  of  100  feet. 
The  author  is  disposed  to  place  the  sandstone  of  Lake  Superior  at 
the  base  of  the  fossilif erous  series.  The  imbedded  traps  of  Keweenaw 
Point  and  Isle  Royal  have  broken  through  this  sandstone,  forming 
continuous  lines  of  elevation.  In  receding  from  the  trap  of  Kewee- 
naw Point  the  inclination  of  the  sandstone  diminishes  rapidly,  and 
5  or  6  miles  away  is  nearly  horizontal.     In  a  fork  of  Torch  River,  on 
5572 1 — B  nil.   360—09- 8 
