﻿482 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  To 
  the 
  south 
  of 
  the 
  trough 
  of 
  the 
  Mohawk 
  valley 
  we 
  have 
  first 
  

   the 
  shales, 
  followed 
  in 
  ascending 
  series 
  by 
  the 
  Medina 
  and 
  Oneida 
  

   sandstones, 
  the 
  shales 
  and 
  limestones 
  of 
  the 
  Clinton 
  formation, 
  

   the 
  Niagara 
  limestones, 
  the 
  rocks 
  of 
  the 
  salt 
  group, 
  the 
  Helder- 
  

   berg 
  limestone, 
  the 
  Oriskany 
  sandstone, 
  the 
  Onondaga 
  limestone, 
  

   and 
  finally 
  the 
  extended 
  area 
  covered 
  by 
  the 
  Catskill 
  and 
  Che- 
  

   mung 
  sandstones. 
  The 
  headwaters 
  of 
  Schoharie 
  creek 
  issue 
  

   mostly 
  from 
  the 
  Catskill 
  formation, 
  although 
  the 
  extreme 
  head- 
  

   waters 
  flow 
  from 
  off 
  the 
  Oneonta 
  sandstone, 
  which, 
  however, 
  is 
  

   closely 
  allied 
  to 
  the 
  Catskill. 
  The 
  shorter 
  streams 
  on 
  the 
  south 
  

   side 
  issue 
  from 
  the 
  horizon 
  of 
  the 
  Hudson 
  and 
  Utica 
  shales, 
  the 
  

   same 
  as 
  short 
  streams 
  to 
  the 
  north. 
  1 
  

  

  The 
  soils 
  of 
  a 
  considerable 
  portion 
  of 
  the 
  Mohawk 
  river 
  catch- 
  

   ment 
  area 
  are 
  consequently 
  heavy 
  and 
  impermeable, 
  and 
  further 
  

   tend 
  to 
  give 
  heavy 
  runoffs 
  at 
  time 
  of 
  flood-flow. 
  

  

  As 
  regards 
  flood-flows 
  in 
  the 
  lower 
  Mohawk 
  river, 
  the 
  stream 
  

   divides 
  naturally 
  at 
  Little 
  Falls. 
  Below 
  that 
  point 
  the 
  flat 
  area 
  

   is 
  relatively 
  more 
  restricted, 
  and 
  the 
  flood-flows 
  probably 
  larger 
  

   in 
  volume 
  than 
  at 
  Little 
  Falls. 
  We 
  have 
  already 
  given 
  particu- 
  

   lars 
  of 
  the 
  highest 
  flood 
  at 
  Rexford 
  Flats, 
  where 
  the 
  catchment 
  is 
  

   3385 
  square 
  miles. 
  According 
  to 
  the 
  Report 
  on 
  Water 
  Power 
  in 
  

   the 
  Tenth 
  Census, 
  in 
  an 
  extreme 
  flood 
  which 
  occurred 
  about 
  1860 
  

   to 
  1865 
  there 
  is 
  stated 
  to 
  have 
  been 
  a 
  depth 
  of 
  12 
  feet 
  of 
  water 
  on 
  

   the 
  Cohoes 
  dam, 
  which 
  is 
  1400 
  feet 
  in 
  length. 
  If 
  such 
  a 
  depth 
  

   actually 
  occurred, 
  the 
  discharge 
  may 
  have 
  been 
  over 
  200,000 
  cubic 
  

   feet 
  per 
  second 
  or 
  at 
  the 
  rate 
  of 
  over 
  59 
  cubic 
  feet 
  per 
  second 
  per 
  

   square 
  mile. 
  The 
  information 
  at 
  hand 
  does 
  not 
  indicate 
  a 
  flow 
  

   over 
  about 
  78,350 
  cubic 
  feet 
  per 
  second 
  or 
  23 
  cubic 
  feet 
  per 
  second 
  

   per 
  square 
  mile 
  at 
  the 
  Rexford 
  Flats 
  dam. 
  The 
  maximum, 
  how- 
  

   ever, 
  in 
  view 
  of 
  the 
  foregoing, 
  may 
  be 
  placed 
  at 
  a 
  considerably 
  

   higher 
  figure 
  than 
  this. 
  

  

  Floods 
  in 
  Cayadutta 
  creek. 
  The 
  maximum 
  flood 
  of 
  this 
  stream 
  

   near 
  Johnstown 
  is 
  stated 
  to 
  have 
  occurred 
  in 
  the 
  spring 
  of 
  1896, 
  

   at 
  which 
  time 
  the 
  flow 
  was 
  2895 
  cubic 
  feet 
  per 
  second 
  (catchment, 
  

   40 
  square 
  miles), 
  or 
  at 
  the 
  rate 
  of 
  72 
  cubic 
  feet 
  per 
  second 
  per 
  

   square 
  mile. 
  

  

  a 
  Also 
  see 
  statements 
  regarding 
  geology 
  of 
  Mohawk 
  valley 
  on 
  p. 
  411. 
  

  

  