252  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
metamorphosed  in  the  area  between  Trinity  and  Bonavista  bays.  The 
peculiar  manner  in  which  the  granitic  rocks  vary  into  the  slates  by 
gradual  interlaminations,  combined  with  the  occurrence  of  fragments 
of  the  schists  within  the  granite,  so  well  described  by  Jukes  and  cor- 
roborated by  Howley,  indicate  that  a  large  part  of  the  rocks  referred  to 
the  Laurentian  are  certainly  intrusive,  and  that  the  more  crystalline 
character  of  the  clastic  formations  adjacent  to  them  are  due  to  meta- 
morphism.  It  is  then  by  no  means  clear  that  within  Avalon  are  any 
rocks  of  sedimentary  origin  older  than  the  series  referred  to  the  Huro- 
nian,  although  the  fact  mentioned  by  Jukes  of  a  single  bowlder  of  syen- 
ite in  the  older  slate  series  indicates  the  probability  of  a  pre-Huronian 
syenitic  or  gneissic  series.  At  present  we  have,  however,  no  means  of 
judging  what  part  of  the  rocks  referred  to  the  Laurentian  are  later  in- 
trusives  and  what  part,  if  any,  are  older  than  the  pre- Cambrian  clastic 
series. 
As  to  the  rocks  referred  to  the  Upper  Laurentian  because  of  the  pres- 
ence of  anorthosite  rocks  and  limestones,  the  question  arises  as  to 
whether  the  crystalline  limestones  associated  with  the  gneisses  are  not 
of  later  age  than  supposed,  being  perhaps  more  metamorphosed.  The 
associated  anorthosite — that  is,  a  probably  eruptive  rock — may  be  an 
explanation  of  this  metamorphism.  If  the  presence  in  Newfoundland 
of  a  Lower  Laurentian  is  doubtful,  it  is  much  more  doubtful  whether 
here  an  upper  series  of  fragmental  rocks  has  been  shown  to  exist  which 
are  older  than  the  pre-Cambrian  series  referred  to  the  Huronian. 
The  observations  made  by  Jukes  as  to  the  relations  of  slaty  cleavage 
and  bedding  are  of  the  greatest  interest  and  importance.  The  strike 
of  the  cleavage  is  in  a  great  majority  of  instances  parallel  to  the  strike 
of  the  beds,  but  not  invariably  so.  The  cleavage  is  much  more  con- 
stant as  regards  its  strike  and  dip  than  is  the  strike  and  the  dip  of  the 
beds.  The  dip  of  cleavage  is  never  at  a  less  angle  than  45°,  while  in 
the  majority  of  instances  it  is  nearly  perpendicular. 
NOTES. 
1  The  Metatnorphic  Rocks  of  the  Notre  Dame  Mountains,  Alexander  Murray.  Rept. 
of  Prog.  Geo!.  Survey  of  Canada  for  1845-'46,  pp.  111-114. 
2  Report  of  Progress  of  the  Geological  Survey  of  Canada  from  its  Commencement 
to  1863,  W.  E.  Logan,  pp.  983.     With  an  atlas. 
3  Report  of  Observations  on  the  Stratigraphy  of  the  Quebec  Group  and  the  Older 
Crystalline  Rocks  of  Canada,  A.  R.  C.  Selwyn.  Rept.  of  Prog.  Geol.  Survey  of  Can- 
ada for  1877-78,  pp.  1-15  A. 
4 Notes  on  the  Geology  of  the  Southeastern  Portion  of  the  Province  of  Quebec,  A. 
R.  C.  Selwyn.  Rept.  of  Prog.  Geol.  and  Nat.  Hist.  Survey  of  Canada  for  1880-'81-'82, 
pp.  1-7  A. 
5  The  Quebec  Group  in  Geology,  with  ah  Introductory  Address,  A.  R.  C.  Selwyn. 
Proc.  and  Trans,  of  the  Royal  Soc,  of  Canada  for  1882  and  1883,  vol.  i,  sec.  4,  1882,  pp. 
1-13. 
0  Report  on  the  Geology  of  a  Portion  of  the  Eastern  Townships  of  Quebec,  ^elat- 
ing more  especially  to  the  Counties  of  Comptou,  Stanstead,  Beauce,  Richmond^  and 
