﻿164 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  in 
  both 
  form 
  and 
  relation. 
  They 
  lack 
  concentric 
  parallelism, 
  in 
  

   other 
  words 
  are 
  not 
  in 
  regular 
  series 
  ; 
  and 
  they 
  are 
  not 
  always 
  

   transverse 
  or 
  normal 
  to 
  the 
  line 
  of 
  motion 
  of 
  the 
  tool, 
  as 
  shown 
  

   by 
  the 
  band 
  of 
  crushing 
  or 
  gouging. 
  Figure 
  14 
  shows 
  these 
  

   characters. 
  

  

  /^ 
  To 
  summarize: 
  the 
  gouge 
  

  

  or 
  dragging 
  fractures 
  would 
  

   seem 
  to 
  be 
  the 
  effect 
  of 
  a 
  

   steady 
  dragging 
  motion 
  of 
  a 
  

   boulder 
  with. 
  large 
  contact 
  sur- 
  

   face, 
  while 
  the 
  chatters 
  are 
  the 
  

   product 
  of 
  unsteady, 
  percus- 
  

   sive 
  or 
  pounding 
  movement 
  of 
  

   points 
  of 
  boulders 
  or 
  small 
  

   contact 
  surfaces. 
  

  

  Limestone 
  flutings. 
  Over 
  

   large 
  districts 
  in 
  the 
  southern 
  

   part 
  oif 
  the 
  limestone 
  area 
  the 
  

   Fig. 
  14 
  Gouge 
  fractures 
  ^^^y, 
  surface 
  is 
  wom 
  iuto 
  series 
  

  

  of 
  parallel, 
  cylindrical 
  ridges 
  of 
  several 
  feet 
  diameter, 
  separated 
  by 
  

   equally 
  regular 
  troughs 
  or 
  hollows. 
  These 
  features 
  which 
  can 
  be 
  

   attributed 
  only 
  to 
  ice 
  erosion 
  are 
  illustrated 
  in 
  plates 
  60-63. 
  As 
  the 
  

   amount 
  of 
  erosion 
  and 
  the 
  direction 
  of 
  the 
  ribs 
  and 
  ice 
  movement 
  

   are 
  inconsistent 
  with 
  the 
  work 
  of 
  the 
  latest 
  ice 
  sheet 
  the 
  discussion 
  

   of 
  the 
  topic 
  is 
  deferred 
  to 
  the 
  next 
  chapter. 
  

  

  Prewisconsin 
  glaciation 
  

  

  Theoretic 
  considerations. 
  In 
  the 
  preceding 
  pages 
  several 
  

   features 
  have 
  been 
  mentioned 
  as 
  difficult 
  of 
  explanation 
  or 
  incon- 
  

   sistent 
  with 
  the 
  conception 
  of 
  a 
  single 
  ice 
  invasion. 
  The 
  facts 
  

   and 
  argument 
  favoring 
  the 
  view 
  of 
  multiple 
  glaciation 
  will 
  be 
  

   summarized 
  here. 
  

  

  If 
  the 
  generally 
  accepted 
  conclusions 
  of 
  glacialists, 
  that 
  the 
  north- 
  

   eastern 
  states 
  have 
  been 
  repeatedly 
  glaciated 
  since 
  Tertiary 
  time, 
  

   are 
  well 
  founded, 
  it 
  is 
  quite 
  impossible 
  to 
  except 
  or 
  exclude 
  

   New 
  York 
  from 
  all 
  ice 
  invasions 
  earlier 
  than 
  the 
  latest, 
  or 
  Wis- 
  

   consin. 
  The 
  several 
  glacial 
  epochs 
  recognized 
  in 
  the 
  Mississippi 
  

   valley 
  have 
  been 
  named 
  on 
  page 
  137. 
  The 
  very 
  old 
  drift 
  of 
  New 
  

   Jersey 
  and 
  southeastern 
  Pennsylvania 
  is 
  believed 
  to 
  be 
  as 
  old, 
  cer- 
  

   tainly, 
  as 
  the 
  Kansan, 
  and 
  probably 
  represents 
  the 
  Preaftonian, 
  

   which 
  is 
  now 
  sometimes 
  called 
  the 
  Jerseyan 
  when 
  referring 
  to 
  the 
  

  

  