﻿CJD.WALGOTT. 
  

  

  THE 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [THIRD 
  SERIES.] 
  

  

  Art. 
  XLYII. 
  — 
  On 
  PercivaVs 
  map 
  of 
  the 
  Jura-Trias 
  trap- 
  

   belts 
  of 
  Central 
  Connecticut, 
  with 
  observations 
  on 
  the 
  up- 
  

   turning, 
  or 
  mountain-making 
  disturbance, 
  of 
  the 
  Forma- 
  

   tion 
  / 
  by 
  James 
  D. 
  Dana. 
  With 
  a 
  map. 
  Plate 
  XYI. 
  

  

  In 
  my 
  paper 
  on 
  the 
  features 
  of 
  non- 
  volcanic 
  igneous 
  ejec- 
  

   tions 
  as 
  illustrated 
  in 
  the 
  Four 
  " 
  Rocks 
  " 
  of 
  the 
  New 
  Haven 
  

   region 
  at 
  page 
  79 
  of 
  this 
  volume, 
  the 
  resemblances 
  in 
  general 
  

   structure 
  and 
  system 
  of 
  arrangement 
  between 
  the 
  West 
  Rock 
  

   trap-ridge 
  and 
  the 
  other 
  trap-ridges 
  of 
  the 
  Jura-Trias 
  in 
  the 
  

   Connecticut 
  valley 
  are 
  referred 
  to 
  as 
  evidence 
  of 
  oneness 
  in 
  

   method 
  of 
  origin 
  ; 
  and 
  also 
  of 
  oneness 
  in 
  time 
  of 
  origin, 
  

   whether 
  before 
  or 
  after 
  the 
  upturning 
  of 
  the 
  sandstone, 
  the 
  

   great 
  mountain-making 
  event 
  of 
  the 
  valley. 
  This 
  evidence 
  — 
  

   now 
  contested 
  though 
  formerly 
  considered 
  conclusive 
  — 
  cannot 
  

   be 
  fully 
  appreciated 
  without 
  a 
  knowledge 
  of 
  the 
  general 
  ar- 
  

   rangement 
  of 
  the 
  trap-belts 
  of 
  the 
  valley. 
  Happily, 
  we 
  have 
  

   an 
  excellent 
  map 
  of 
  these 
  belts 
  in 
  Percival's 
  geological 
  chart, 
  

   published 
  in 
  his 
  Report 
  of 
  1842 
  on 
  the 
  Geology 
  of 
  the 
  State 
  

   of 
  Connecticut.* 
  

  

  * 
  An 
  octavo 
  volume 
  of 
  496 
  pages, 
  with, 
  a 
  folded 
  geological 
  chart 
  of 
  the 
  State. 
  

  

  James 
  G-. 
  Percival, 
  born 
  and 
  brought 
  up 
  in 
  the 
  township 
  of 
  Berlin, 
  southwest 
  

   of 
  Hartford, 
  was 
  early 
  familiar 
  with 
  all 
  the 
  intricacies 
  of 
  that 
  knotty 
  region 
  of 
  

   trap-belts. 
  He 
  became 
  a 
  great 
  scholar 
  in 
  all 
  the 
  learning 
  of 
  the 
  day 
  — 
  an 
  excel- 
  

   lent 
  mathematician, 
  a 
  professor 
  of 
  chemistry 
  in 
  1824, 
  a 
  learned 
  linguist 
  and 
  phi- 
  

   lologist, 
  one 
  of 
  the 
  best 
  of 
  geographers 
  ; 
  and 
  in 
  all 
  departments 
  he 
  was 
  an 
  acute 
  

   and 
  thorough 
  student 
  and 
  observer. 
  Along 
  with 
  this 
  he 
  had 
  a 
  wonderfully 
  good 
  

   eye 
  for 
  topography, 
  and 
  a 
  memory 
  which 
  retained 
  all 
  the 
  facts 
  that 
  ever 
  en- 
  

   tered 
  it. 
  Nearly 
  all 
  the 
  money 
  he 
  received 
  went 
  for 
  the 
  purchase 
  of 
  books, 
  and 
  

   he 
  thus 
  acquired 
  a 
  very 
  valuable 
  library 
  at 
  the 
  expense 
  of 
  poverty 
  to 
  himself. 
  At 
  

  

  Am 
  Jour. 
  Sci.— 
  Third 
  Series, 
  Vol. 
  XLII, 
  No. 
  252.— 
  December, 
  1891. 
  

   30 
  

  

  