592  PRE-CAMBRIAN    GEOLOGY    OF    NORTH   AMERICA. 
Iii  western  Rhode  Island  there  is  an  area  of  pre-Cambrian  gneiss, 
which  extends  westward  into  Connecticut  and  northward  a*s  far  as 
Southboro,  Mass.  This  rock  is  described  by  Emerson  as  a  medium 
to  coarse-grained  light-colored  gneiss.  In  texture  it  is  granitoid, 
sometimes  porphyritic,  but  more  often  presents  a  mashed  or  stretched 
facies.  This  Xorthbriclge  gneiss  of  Emerson  is  to  be  distinguished, 
however,  from  the  porphyritic  granite  gneiss  which  borders  the 
Cambrian  rocks  on  the  south  and  east  side  of  the  Narragansett  basin, 
since  that  granite  is  probably  intrusive  in  the  Cambrian  strata. 
The  metamorphosed  sediments  termed  the  "  Blackstone  series  "  by 
Woodworth  and  assigned  b/\7  him  to  the  Algonkian  are  now  believed 
by  Emerson  to  be  of  Cambrian  age. 
NOTES. 
1  First  annual  report  on  the  geology  of  the  State  of  Maine,  by  Charles  T. 
Jackson.     Augusta,  1837,  pp.  viii,  9-128,  24  plates. 
2  Sketch  of  the  geology  of  Portland  and  its  vicinity,  hy  Edward  Hitchcock. 
Jour.  Boston  Soc.  Nat.  Hist,  vol.  1,  1834-1837,  pp.  306-347,  with  a  geological 
map. 
3  Third  annual  report  on  the  geology  of  the  State  of  Maine,  by  Charles  T. 
Jackson.     Augusta,  1839,  pp.  xiv,  1-276. 
4  General  report  upon  the  geology  of  Maine,  by  Charles  H.  Hitchcock.  Pre- 
liminary report  upon  the  natural  history  and  geology  of  the  State  of  Maine, 
1861,  pp.  146-328. 
5  Reports  on  the  geology  of  Maine,  by  Charles  H.  Hitchcock.  Seventh  Ann. 
Kept.  Sec.  Maine  Board  Agr.,  1862,  pp.  223-312,  323-332,  345-352,  377-382, 
388-395,  404-413,  422^30,  with  map. 
6  The  geology  of  Portland,  by  Charles  H.  Hitchcock.  Proc.  Am.  Assoc.  Adv. 
Sci.,  vol.  22,  1874,  pp.  163-175. 
7  Geology  of  the  region  about  the  headwaters  of  the  Androscoggin  River, 
Maine,  by  J.  H.  Huntington.     Idem,  26th  meeting,  1878,  pp.  277-286. 
8  First  annual  report  on  the  geology  of  New  Hampshire,  by  Charles  T.  Jack- 
son.    Concord,  1841,  pp.  164. 
9  Final  report  on  the  geology  and  mineralogy  of  the  State  of  New  Hampshire, 
with  contributions  toward  the  improvement  of  agriculture  and  metallurgy,  by 
Charles  T.  Jackson,  1844,  pp.  viii,  376,  with  a  map  and  sections. 
10  On  the  geological  age  of  the  White  Mountains,  by  Henry  D.  and  William  B. 
Rogers.    Am.  Jour.  Sci.,  2d  ser.,  vol.  1,  1846,  pp.  411-121. 
11  On  the  geological  age  of  the  White  Mountains,  by  Charles  T.  Jackson.  Proc. 
Boston  Soc.  Nat.  Hist.,  vol.  2,  1848,  pp.  147-148. 
12  The  geology  of  New  Hampshire,  by  C.  H.  Hitchcock,  State  geologist ;  J.  H. 
Huntington,  Warren  Upham,  G.  W.  Hawes,  assistants;  vol.  2,  Concord,  1877, 
pp.  684,  with  a  six-sheet  geological  map.  See  also,  by  C.  H.  Hitchcock,  idem, 
vol.  1,  1874,  pp.  667,  with  maps.  First  annual  report  on  the  geology  and  min- 
eralogy of  New  Hampshire,  Manchester,  1869,  pp.  36,  with  a  map.  Second  an- 
nual report  on  the  geology  and  mineralogy  of  New  Hampshire,  Manchester, 
1870,  pp.  37,  with  a  map.  Report  of  the  geological  survey  of  the  State  of  New 
Hampshire,  showing  its  progress  during  the  year  1870,  Nashua,  1871,  pp.  82. 
Report  of  the  geological  survey  of  New  Hampshire,  its  progress  during  1871, 
Nashua,  1872,  pp.  56,  with  a  map.  Norian  rocks  in  New  Hampshire.  Am.  Jour. 
Sci.,  3d  ser.,  vol,  3,  1872,  pp.  43^17.     Recent  geological  discoveries  among  the 
