van  hise.1  EASTERN    UNITED    STATES.  427 
and  Acadian),  partly   Upper   Azoic  rocks  (Huronian),  and  perhaps 
partly  Lower  Azoic  rocks  ( Laurent i an). 
Going  at  a  right  angle  with  the  strike,  from  northwest  to  southeast, 
is  found  the  following  zones,  which,  however,  cannot  be  sharply  sepa- 
rated. (1)  Siluricm. — Crystalline  limestones,  conglomerates,  heavy 
quartzites,  and  slates  (often  gold-bearing),  semi-metamorphosed.  (2) 
Huronian. — Mica-slates  and  schists  (with  garnets),  limestones,  coarse 
grained  granites,  diorites,  quartzites,  and  clay-slates  (sometimes  gold- 
bearing);  the  mica- schists  often  alternating  with  gneisses;  associated 
with  graphite  and  graphitic  slates,  itacolumite,  specular  ore,  brown 
hematite,  etc.  (3)  Huronian  or  Upper  Laurentian. — Gneisses  (micaceous 
and  hornblendic),  granite,  diorite,  mica-schists,  quartzites,  slates  (some- 
times gold-bearing),  associated  with  chloritic  schists  and  steatites,  mica 
with  tourmaline  crystals,  etc.  Some  of  the  granites  have  the  charac- 
teristics of  eruptive  rocks. 
GENERAL  LITERATURE. 
Britton,214  in  1886,  describes  at  Natural  bridge  the  contact  between 
sandstones  which  appear  to  be  under  the  Potsdam  and  over  the  Archean. 
The  two  are  widely  unconformable;  the  sandstone  dips  45°  to  the 
northwest  and  strikes  N.  40°  E.,  while  the  Archean  dips  05°  E.  and 
strikes  N.  5°  E.  The  Archean  rocks  consist  of  quartz-bearing  syenite 
and  granulite,  fragments  of  whieh  are  found  in  the  overlying  series. 
On  the  Doe  river,  in  eastern  Tennessee,  the  Archean  and  basal  Si- 
lurian quartzite  are  in  contact.  The  Archean  is  a  pegmatite,  with  no 
bedding  or  lamination.  Five  hundred  feet  east  of  the  contact  it  is  a 
much  contorted  hornblendic  gneiss  and  syenite.  These  rocks  are  in- 
tersected by  a  trap  dike.  The  quartzite  is  thickly  bedded  and  con- 
tains many  pebbles  of  quartz  and  much  feldspar,  so  as  to  make  the 
roek  in  places  an  arkose. 
On  the  French  Broad  river  are  found  quartzites  like  those  of  the  Do- 
river,  which  are  succeeded  by  basal  crystalline  rocks,  and  near  Mare 
shall  station  begins  a  stratified  micaceous  schistose  series.  The  char- 
acter of  the  transition  between  this  and  the  basal  Archean  rocks  was 
not  apparent.  About  Asheville  are  well  bedded  gneisses  and  mica 
sell  ists  which  bear  the  same  relation  to  the  heavily  bedded  basal  Archean 
as  do  the  Westchester  county,  New  York,  and  Philadelphia  gneisses 
to  the  basal  rocks  to  the  westward.  These  rocks  extend  to  the  top  of 
mount  Mitchell. 
SUMMARY   OF   RESULTS. 
The  state  of  knowledge  of  the  crystalline  rocks  of  the  southern  Ap- 
palachians is  in  a  still  less  advanced  condition  than  that  of  the  middle 
and  northern  Appalachians. 
It  is  reasonably  certain  that  from  northern  Virginia  to  Alabama 
there  are  large  areas  which  are  pre-Oambrian,  including  much  of  tbe 
