vanhise.1  DISCUSSIONS    OF    PRINCIPLES.  525 
or  reviews  of  literature,  to  mention  the  opinions  which  appear  to  be 
prevalent  in  reference  to  the  pre-Cambrian  of  Europe. 
In  the  first  place,  it  is  not  universally  held  that  in  Europe  there  are 
pre-Canibrian  elastics.  It  is  probable  that  this  difference  of  opinion 
results  in  part  because  it  is  not  agreed  as  to  the  lower  limit  of  the  Cam- 
brian. If  this  could  be  settled  it  would  be  comparatively  easy  to  decide 
as  to  the  existence  of  pre-Cambrian  sedimentaries. 
Nowhere  has  there  been  in  the  past  a  wider  difference  of  opinion  on 
this  question  than  in  Great  Britain,  but  now  the  consensus  of  opinion 
appears  to  be  that  pre-Cambrian  elastics,  either  water-deposited  or 
volcanic,  or  both,  occur  at  various  places.  The  officers  of  the  official 
survey  have,  until  very  recently,  denied  that  such  rocks  occur ;  but  the 
Director- General  states,  in  a  late  paper,  that  in  western  Scotland,  asso- 
ciated with  the  fundamental  gneiss,  are  small  areas  of  schist  and 
limestones  which  are  possibly  sedimentary  5  that  within  the  complex  of 
rocks  in  Scotland,  for  which  the  term  Dalradian  is  proposed,  there  are 
probably  pre-Cambrian  elastics  both  of  sedimentary  and  volcanic  ori- 
gin, and  that  Callaway  is  correct  as  to  the  pre-Cambrian  age  of  the 
Uriconian  volcanics.  Still  more  recently  it  has  been  announced  that 
the  Torridon  sandstone,  8,000  or  10,000  feet  thick,  which  contains 
traces  of  annelids  and  other  obscure  organic  remains,  lies  unconforma- 
bly  below  theOlenellus  Cambrian  and  must  therefore  be  classed  as  pre- 
Cambrian. 
The  head  of  the  official  survey  of  France,  Michel-Levy,  states  that 
in  the  pre-Cambrian  are  placed  only  those  rocks  which  are  completely 
crystalline  and  which  antedate  all  the  clastic  series.  The  Cambrian  is 
delimited  below  by  the  appearance  of  the  first  layers,  which  are  incon- 
testably  clastic.  It  passes  insensibly  into  the  crystalline  rocks  re- 
garded as  pre-Cambrian.  The  Cambrian  is  delimited  above  by  the 
overlying  accordant  or  discordant  strata-bearing  fossils.  The  rocks 
placed  in  the  Cambrian  are  for  the  most  part  nonfossiliferous,  and, 
while  clastic  as  a  whole,  are  locally  much  altered  by  contact  action  and 
are  more  crystalline  than  the  later  formations.  The  foregoing  positions 
are  very  different  from  those  held  by  Barrois,  another  of  the  official 
geologists.  This  author  holds  that  in  France  there  is  at  least  one 
series  of  pre-Cambrian  rocks  of  clastic  origin  to  which  he  has  applied 
the  term  Huronian. 
In  Germany  there  is  a  radical  difference  of  opinion  between  the  lead- 
ing geologists  as  to  whether  pre-Cambrian  elastics  exist,  although  a 
large  majority  maintains  that  belonging  here  are  the  Obermittweida 
conglomerate  and  similar  rocks  in  other  localities.  Others  hold  that 
these  rocks  are  in  folded  parts  of  the  Cambrian  or  post-Cambrian.  The 
commonly  accepted  classification  of  the  pre-Cambrian  rocks,  according 
to  Lossen,  is  as  follows :  (1)  Urgneiss  or  fundamental  gneiss,  which  in 
places  is  rather  a  granite  than  a  gneiss.  Toward  the  top,  the  forma- 
tion takes  in  Jbe<ls  of  limestone,  quartzite,  and  amphibolite,  generally, 
