vanhise.]  LAKE    SUPERIOR    REGION.  141 
Wall  ravine  the  sandstone  and  conglomerate  bearing  fragments  of  the 
porphyry-conglomerate,  with  which  rock  the  contact  here  occurs,  are 
found  to  dip  at  a  considerable  angle  away  from  the  eruptive  rock  and 
to  rest  directly  upon  it.  At  the  St.  Louis  ravine  the  sandstone  is  found 
upon  approaching  the  Keweenaw  series  to  become  rapidly  tilted  up- 
ward, and  before  reaching  the  Keweenawan  rocks  to  become  vertical, 
while  the  interstratified  eruptives  and  detrital  rocks  of  the  Keweenaw 
series  dip  away  from  the  sandstone.  At  the  Douglass  Houghton  ra- 
vine  the  horizontal  sandstone  is  found  upon  approaching  the  Keweenaw 
series  to  become  bent  into  a  series  of  folds  and  to  dip  downward  under 
the  traps  and  porphyries,  which  dip  at  a  steeper  angle  in  the  same  di- 
ection.  Along  the  contact  the  trap  is  shattered.  At  Torch  lake 
piarry  the  sandstone  is  found  to  be  in  a  horizontal  position,  there  being 
lio  evidence  whatever  found  that  this  structure  is  jointing  or  that  the 
:eal  dip  has  an  inclination,  as  described  by  Wadsworth.  The  crystal 
outlined  grains  of  sand  here  contained  are  found  to  be  produced  by 
econdary  growth  rather  than  crystals  derived  from  quartz-porphyry. 
At  the  Hungarian  ravine  the  relations  are  much  the  same  as  those  at 
;he  Douglass  Houghton  ravine,  except  that  the  Keweenawan  diabase  is 
nterstratihed  with  conglomerate  instead  of  quartz-porphyry.  Along 
he  contact  the  sandstone  is  broken. 
In  getting  at  an  explanation  of  the  facts  there  must  be  taken  into 
iccount  the  bedded  nature  of  the  Keweenaw  series;  the  uniformity- and 
steadiness  of  dip ;  the  enormous  thickness  of  the  Keneenaw  series ;  the 
general  horizontality  of  the  Eastern  sandstone ;  the  quartzose  character 
)f  the  Potsdam  sands  in  distinction  to  the  silicate  nature  of  the  Kewee- 
lawan  sands 5  the  mutual  relations  and  distribution  of  the  two  series; 
;he  relations  to  topography;  the  relations  of  the  two  series  to  drain- 
age; the  comparative  straightness  but  gentle  undulations  of  the  junc- 
ion  line  throughout  its  course  of  nearly  100  miles;  the  coincidence 
)f  the  line  of  escarpment  with  the  line  of  junction  of  the  two  series; 
he  disturbance  along  the  line  of  contact;  the  special  character  of  the 
iistortions;  the  character  of  the  junction;  the  junction  debris;  theirreg- 
ilar  and  broken  contact  faces  of  the  two  series;  the  fact  that  the  con- 
tact occurs  between  the  Eastern  sandstone  and  different  members  of 
bhe  Keweenaw  series;  the  discordance  of  strike;  the  derivation  of  the 
pebbles  of  the  Eastern  sandstone  from  the  Keweenaw  series;  'the  dis- 
tribution of  the  pebbles,  those  of  the  Keweenaw  series  being  found 
^nly  near  the  immediate  junction;  the  imperfect  assortment  of  the 
pebbles  and  matrix  near  the  junction;  the  angularity  of  the  pebbles  at 
this  place;  the  absence  of  large  fallen  masses  of  trap  in  the  Eastern 
Sandstone;  and  the  proximity  and  relations  of  the  Trenton  limestone, 
nesting  as  it  does  upon  the  Eastern  sandstone  within  a  short  distance. 
These  specifications  are  taken  to  point  with  distinctness  to  the  conclu- 
sion that  the  Keweenaw  series  is  much  older  than  the  Eastern  Potsdam 
I  sandstone,  that  it  was  upturned,  faulted  along  the  escarpment  and 
