568  CONTRIBUTIONS   TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
380  and  443  feet  above  tide.  The  lake  valleys  are  very  deeply  filled 
about  their  heads  with  drift  and  lake  clays,  the  filling  at  Ithaca 
having  a  maximum  thickness  of  400  feet  and  at  Watkins  of  more  than 
1,000  feet.  Wells  located  about  the  heads  of  these  lakes  have  the 
advantage,  therefore,  not  only  of  starting  400  feet  or  more  nearer 
the  salt  than  in  other  valleys  of  the  region,  but  pass  in  the  upper  part 
of  their  course  through  the  comparatively  soft  and  easily  drilled 
clays  and  gravels  of  the  Ithaca  and  Watkins  deltas. 
General  geology. — The  surface  rocks  of  this  region  comprise  the 
sandy  shales  and  thin-bedded  sandstones  of  the  Chemung  and  Nunda 
formations.  There  is  a  general  southerly  inclination  of  the  rocks, 
interrupted  by  a  series  of  broad,  low  folds  with  east-west  trend. 
The  salt  beds  occur  in  the  Salina  formation  and  comprise  a  series 
of  beds  of  rock  salt  interbedded  with  green  and  reddish  shales.  In 
thickness  the  beds  of  salt  vary  from  more  than  50  feet  to  less  than  5 
feet.  Some  of  the  saline  horizons  are  represented  by  salt  crystals 
disseminated  through  the  shale  beds,  but  the  thicker  beds  are  com- 
posed of  nearly  pure  rock  salt. 
At  Ithaca  the  top  of  the  salt  has  been  reached  in  the  Remington 
well  at  a  depth  of  2,137  feet,  or  1,737  feet  below  sea  level.  The  log 
of  the  old  test  well  records  the  first  salt  at  a  depth  of  2,244  feet,  or 
1,844  feet  below  tide.  At  Watkins  the  wells  reach  the  salt  at  a  depth 
of  about  1,800  feet,  or  about  1,350  feet  below  sea  level.  Only  two 
wells  have  been  drilled  which  pass  through  the  entire  thickness  of 
the  salt  beds.  These  are  the  Ithaca  test  well  and  the  Hill  well  at 
Watkins. 
The  portions  of  these  records  which  include  the  salt  deposits  are 
here  given.  The  mouth  of  the  George  G.  Hill  well  is  located  about 
665  feet  above  tide.     Its  record  of  the  salt  deposits  is  as  follows: 
Log  of  the  George  G.  Hill  salt  well  at  Watkins,  N.  Y. 
Feet. 
1.  Gray  "shale" 1,880-2,005 
2.  Salt    (1) :___  2,005-2,270 
3.  Limestone  with  occasional  layers  of  shales 2,270-2,310 
4.  Salt    (2) 2,310-2,338 
5.  Brown  shale 2,338-2,378 
6.  Salt    (3) 2,378-2,450 
7.  Brown   shale 2,450-2,507 
8.  Salt    (4) 2,507-2,517 
9.  Brown  shale i 2,517-2,537 
10.  Salt    (5) 2,537-2,560 
11.  Brown   shale 2,560-2,630 
12.  Salt    ((>) 2,630-2,680 
13.  Limestone  and  shales -_ 2,680-2,810 
14.  Salt    (7) , '_'_ 2,810-2,820 
15.  Very  hard  limestone 2,820-2,920 
16-22.  "Slate,"  limestone  and  shale 2,920-3,315 
