﻿r78 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Discussion 
  of 
  the 
  hypotheses 
  

  

  These 
  will 
  be 
  taken 
  up 
  and 
  discussed 
  in 
  the 
  order 
  in 
  which 
  tliey 
  

   have 
  been 
  stated. 
  

  

  Morainal 
  terrace 
  hypothesis. 
  This 
  type 
  of 
  terrace 
  has 
  been 
  

   defined 
  by 
  Gilbert'^ 
  in 
  the 
  following 
  language: 
  "When 
  an 
  

   alhivial 
  plain 
  or 
  alluvial 
  cone 
  is 
  built 
  against 
  the 
  side 
  or 
  front 
  

   of 
  a 
  glacier 
  and 
  the 
  glacier 
  is 
  afterward 
  melted 
  away, 
  the 
  alluvial 
  

   surface 
  becomes 
  a 
  terrace 
  overlooking 
  the 
  valley 
  that 
  contained 
  

   the 
  ice." 
  

  

  Chamberlin,^ 
  in 
  his 
  report 
  on 
  the 
  " 
  Terminal 
  moraine 
  of 
  the 
  

   second 
  glacial 
  epoch," 
  gives 
  the 
  following 
  description 
  of 
  a 
  

   morainic 
  terrace 
  : 
  " 
  In 
  the 
  deep 
  valleys 
  of 
  the 
  more 
  billy 
  regions 
  

   long 
  tongues 
  of 
  ice 
  were 
  thrust 
  forward 
  beyond 
  the 
  common 
  ice- 
  

   margin, 
  along 
  the 
  sides 
  of 
  which 
  drift 
  terraces 
  seem 
  to 
  have 
  been 
  

   formed, 
  which, 
  at 
  their 
  upper 
  or 
  ice-ward 
  extremity, 
  take 
  on 
  a 
  

   morainic 
  character, 
  but 
  at 
  their 
  lower 
  or 
  distal 
  extremity, 
  grade 
  

   away 
  into 
  a 
  smooth, 
  irregular 
  terrace 
  which 
  either 
  dies 
  away 
  or 
  

   abruptly 
  ends." 
  

  

  In 
  his 
  report 
  on 
  the 
  " 
  Surface 
  geology 
  in 
  New 
  Jersey," 
  Salis- 
  

   bury^ 
  has 
  proposed 
  the 
  name 
  karae 
  terrace 
  for 
  the 
  morainic 
  

   terrace 
  of 
  other 
  glacial 
  ists 
  After 
  describing 
  the 
  kame 
  terrace, 
  he 
  

   says 
  : 
  " 
  This 
  is 
  essentially 
  the 
  sense 
  in 
  which 
  the 
  term 
  moraine 
  

   terrace 
  has 
  been 
  used, 
  although 
  the 
  term 
  as 
  heretofore 
  used 
  does 
  

   not 
  imply 
  the 
  absence 
  or 
  essential 
  absence 
  of 
  motion 
  on 
  the 
  part 
  

   of 
  the 
  ice." 
  

  

  The 
  material 
  from 
  which 
  this 
  topographic 
  form 
  is 
  constructed 
  

   may 
  be 
  land-derived 
  or 
  ice-derived, 
  nearly 
  always 
  from 
  the 
  former, 
  

   and 
  generally, 
  to 
  a 
  greater 
  or 
  less 
  extent, 
  a 
  composite 
  of 
  the 
  two 
  

   sources 
  of 
  material, 
  inasmuch 
  as 
  both 
  kinds 
  enter 
  into 
  its 
  make 
  up 
  

  

  a 
  Gilbert, 
  G. 
  K., 
  Lake 
  Bonneville, 
  Monograph 
  1, 
  U. 
  S. 
  G. 
  S., 
  p. 
  81. 
  For 
  a 
  complete 
  description 
  

   see 
  p. 
  81-83. 
  

   b 
  Chamberlin, 
  T. 
  C, 
  Third 
  ann'l 
  report, 
  U 
  S. 
  G. 
  S., 
  1881-'82, 
  304. 
  

  

  c 
  Salisbury, 
  R. 
  D., 
  Ann'l 
  Report 
  New 
  Jersey 
  geol. 
  surv 
  for 
  the 
  year 
  1893, 
  p. 
  156; 
  also 
  consult, 
  

   Hitchcock, 
  E., 
  Smithsonian 
  contr. 
  knowl. 
  Vol. 
  9, 
  p. 
  6, 
  33 
  This 
  is 
  not 
  the 
  true 
  moraine 
  

  

  terrace 
  as 
  described 
  by 
  later 
  writers. 
  

   Jamieson, 
  On 
  the 
  last 
  stage 
  of 
  the 
  glacial 
  period 
  in 
  Great 
  Britain. 
  

  

  Quart, 
  journ. 
  geol. 
  soc. 
  (London), 
  1874, 
  30, 
  333. 
  The 
  author 
  gives 
  a 
  cut 
  

   illustrating 
  the 
  formation 
  of 
  lateral 
  moraine 
  terraces 
  formed 
  by 
  a 
  

   retreating 
  glacial 
  lobe. 
  Reproduced 
  from 
  

   jyiiller, 
  Hugh, 
  River 
  terraciog: 
  Its 
  math 
  )ds 
  and 
  their 
  reiults. 
  Read 
  before 
  Roy. 
  phys. 
  

   soc, 
  March 
  34, 
  1883. 
  

  

  