﻿ACADEMY 
  OP 
  SCIENCES. 
  211 
  

  

  tlie 
  two 
  ranges. 
  Tliis 
  ridge 
  bad 
  evidently 
  been 
  formed 
  by 
  an 
  eruption 
  of 
  

   tracliyte, 
  after 
  the 
  main 
  volcanic 
  beds 
  had 
  been 
  elevated. 
  Masses 
  of 
  green 
  

   trachyte 
  were 
  fouiul 
  on 
  its 
  crest, 
  and 
  the 
  older 
  volcanic 
  rocks 
  were 
  thrown 
  up 
  

   almost 
  perpendicularly 
  along 
  its 
  flanks. 
  The 
  main 
  ridge 
  here 
  attained 
  a 
  height 
  

   of 
  7,500 
  leet, 
  falling 
  off 
  rapidly 
  to 
  the 
  north 
  and 
  south. 
  On 
  crossing 
  the 
  sum- 
  

   mit, 
  at 
  about 
  two 
  miles 
  from 
  the 
  south 
  end 
  of 
  the 
  ridge, 
  and 
  descending 
  about 
  

   a 
  quarter 
  of 
  a 
  mile 
  on 
  its 
  western 
  slope, 
  strata 
  were 
  met 
  with, 
  evidently 
  of 
  

   aqueous 
  origin. 
  They 
  were 
  laying 
  perfectly 
  conformable 
  on 
  volcanic 
  rocks, 
  

   and 
  were 
  covered 
  in 
  by 
  a 
  layer 
  of 
  gray 
  trachyte, 
  also 
  perfectly 
  conformable 
  with 
  

   these 
  aqueous 
  beds. 
  The 
  beds 
  were 
  about 
  200 
  feet 
  thick, 
  consisting 
  of 
  strata 
  

   of 
  white 
  and 
  red 
  argillaceous 
  rocks, 
  rolled 
  conglomerate, 
  and 
  were 
  all 
  evidently 
  

   formed 
  from 
  the 
  debris 
  of 
  volcanic 
  rocks, 
  the 
  conglomerate 
  being 
  made 
  up 
  

   principally 
  of 
  rolled 
  pumice. 
  The 
  west 
  slope 
  of 
  the 
  range 
  gradually 
  descended 
  

   to 
  the 
  valley 
  on 
  the 
  west 
  side 
  without 
  any 
  apparent 
  disturbance, 
  the 
  slope 
  of 
  

   the 
  surface 
  during 
  the 
  whole 
  of 
  the 
  distance 
  being 
  about 
  conformable 
  to 
  the 
  

   strata. 
  

  

  As 
  before 
  stated, 
  this 
  volcanic 
  ridge 
  bends 
  to 
  the 
  east 
  at 
  each 
  end, 
  over- 
  

   lapping 
  the 
  ends 
  of 
  the 
  east 
  range. 
  At 
  the 
  north 
  end, 
  these 
  erupted 
  rocks 
  

   extend 
  about 
  three-quarters 
  of 
  a 
  mile 
  beyood 
  the 
  metamorphic 
  rocks, 
  and 
  are 
  

   here 
  composed 
  principally 
  of 
  grey 
  and 
  red 
  trachytes, 
  the 
  extreme 
  north 
  point, 
  

   however, 
  being 
  formed 
  by 
  vesicular 
  basalts. 
  At 
  the 
  S. 
  end 
  of 
  the 
  range, 
  the 
  

   whole 
  mass 
  of 
  the 
  mountain 
  appears 
  to 
  have 
  been 
  thrown 
  to 
  the 
  east 
  for 
  a 
  dis- 
  

   tance 
  of 
  five 
  or 
  six 
  hundred 
  yards. 
  There 
  the 
  metamorphic 
  and 
  volcanic 
  rocks 
  

   are 
  in 
  contact 
  for 
  a 
  distance 
  of 
  three-quarters 
  of 
  a 
  mile, 
  the 
  porphyritic 
  axis 
  

   of 
  the 
  latter 
  not 
  reaching 
  the 
  surface. 
  It 
  is 
  directly 
  opposite 
  and 
  to 
  the 
  east 
  

   of 
  this 
  great 
  dislocation 
  that 
  the 
  hot 
  spring 
  breaks 
  out 
  with 
  a 
  temperature 
  of 
  

   165°, 
  from 
  which 
  were 
  obtained 
  the 
  interesting 
  specimens 
  of 
  diatoms, 
  a 
  descrip- 
  

   tion 
  of 
  which 
  I 
  submitted 
  to 
  the 
  Academy 
  in 
  1871. 
  To 
  the 
  south 
  of 
  this 
  dis- 
  

   located 
  portion 
  of 
  the 
  range 
  is 
  a 
  deep 
  ravine, 
  and 
  beyond 
  this, 
  and 
  in 
  a 
  line 
  

   with 
  the 
  axis 
  of 
  the 
  metamorphic 
  range, 
  is 
  a 
  range 
  of 
  hills 
  running 
  south 
  about 
  

   three 
  miles, 
  and 
  gradually 
  disappearing 
  by 
  the 
  dip 
  of 
  the 
  strata 
  to 
  the 
  south. 
  

   These 
  hills 
  present 
  an 
  almost 
  perpendicular 
  escarpment 
  to 
  the 
  east, 
  forming 
  a 
  

   clilf 
  about 
  900 
  feet 
  high. 
  The 
  lower 
  part 
  of 
  the 
  cliff 
  is 
  covered 
  up 
  by 
  a 
  mass 
  

   of 
  talus, 
  which 
  itself 
  is 
  so 
  steep 
  and 
  loose 
  as 
  to 
  prevent 
  investigation 
  of 
  the 
  

   structure 
  of 
  the 
  rocks, 
  and 
  extends 
  to 
  a 
  height 
  of 
  300 
  feet 
  above 
  the 
  base 
  of 
  

   the 
  clitf. 
  The 
  rocks, 
  however, 
  are 
  evidently 
  stratified, 
  of 
  aqueous 
  origin, 
  and 
  

   composed 
  of 
  volcanic 
  materials 
  that 
  would 
  appear 
  to 
  have 
  been 
  cemented 
  

   together 
  by 
  a 
  siliceous 
  cement, 
  rendering 
  them 
  almost 
  proof 
  against 
  the 
  action 
  

   of 
  the 
  elements. 
  The 
  strata 
  were 
  very 
  numerous, 
  as 
  I 
  counted 
  six 
  different 
  

   strata 
  in 
  a 
  distance 
  of 
  about 
  tcj 
  feet. 
  They 
  were 
  of 
  different 
  colors, 
  white, 
  red, 
  

   yellow, 
  and 
  some 
  of 
  the 
  more 
  well-marked 
  beds 
  could 
  be 
  traced 
  along 
  the 
  whole 
  

   face 
  of 
  the 
  cliff, 
  getting 
  lower 
  towards 
  the 
  south. 
  At 
  one 
  part 
  there 
  was 
  

   evidence 
  of 
  a 
  fault, 
  the 
  beds 
  having 
  been 
  broken 
  off, 
  and 
  the 
  south 
  end 
  fiilling 
  

   about 
  fifteen 
  feet. 
  This 
  was 
  the 
  only 
  disturbance 
  that 
  showed 
  itself 
  in 
  these 
  beds. 
  

   The 
  cliff 
  itself 
  was 
  evidently 
  the 
  result 
  of 
  a 
  vast 
  fault, 
  by 
  which 
  the 
  ground 
  iu 
  

  

  