﻿Ko. 
  122.] 
  61 
  

  

  anticipation 
  of 
  the 
  plotted 
  sheet 
  that 
  there 
  is 
  not 
  less 
  than 
  eighteen 
  

   and 
  a 
  quarter 
  feet 
  of 
  water 
  on 
  any 
  part 
  of 
  Pot 
  Rock 
  at 
  low 
  tide 
  

   to-day. 
  As 
  soon 
  as 
  possible 
  I 
  will 
  give 
  you 
  the 
  plans 
  of 
  reference 
  

   to 
  mean 
  low 
  water. 
  

  

  " 
  Yours 
  truly, 
  

  

  W. 
  A. 
  BARTLETT, 
  

   U: 
  S. 
  M. 
  and 
  Assistant 
  in 
  the 
  Coast 
  Survey.^'' 
  

  

  From 
  the 
  7th 
  of 
  November 
  to 
  the 
  12th 
  of 
  December, 
  ninety- 
  

   one 
  charges 
  of 
  one 
  hundred 
  and 
  twenty-five 
  pounds 
  each, 
  were 
  

   fired 
  upon 
  Pot 
  Rock. 
  The 
  aggregate 
  weight 
  of 
  these 
  ninety-one 
  

   charges 
  is 
  eleven 
  thousand 
  three 
  hundred 
  and 
  seventy-five 
  

   pounds. 
  

  

  The 
  number 
  of 
  charges 
  fired 
  from 
  August 
  2dth 
  to 
  Dec. 
  12th, 
  

   is 
  two 
  hundred 
  and 
  thirty- 
  four, 
  and 
  the 
  aggregate 
  weight 
  of 
  

   powder 
  in 
  the 
  234 
  charges 
  is 
  twenty-seven 
  thousand 
  nine 
  hun- 
  

   dred 
  and 
  eighty-one 
  pounds. 
  

  

  The 
  present 
  surface 
  of 
  Pot 
  Rock 
  is 
  very 
  large, 
  being 
  equal 
  to 
  

   that 
  of 
  four 
  full 
  sized 
  building 
  lots, 
  twenty-five 
  feet 
  by 
  one 
  

   hundred. 
  

  

  When 
  M. 
  Maillefert 
  commenced 
  operations 
  on 
  Pot 
  Rock, 
  he 
  

   could 
  only 
  fire 
  at 
  high 
  tide 
  and 
  during 
  slack 
  water. 
  No 
  charge 
  

   could 
  be 
  fired 
  on 
  the 
  rock 
  while 
  the 
  tide 
  was 
  running. 
  The 
  tide 
  

   turned 
  very 
  quick 
  on 
  the 
  rock, 
  the 
  longest 
  period 
  for 
  working 
  

   being 
  less 
  than 
  sixteen 
  minutes, 
  during 
  which 
  only 
  two 
  charges 
  

   could 
  be 
  fired. 
  In 
  the 
  early 
  part 
  of 
  November 
  he 
  had 
  broken 
  

   down 
  so 
  much 
  of 
  the 
  rock 
  as 
  to 
  change 
  the 
  current 
  to 
  such 
  an 
  

   extent 
  that 
  he 
  was 
  enabled 
  on 
  the 
  2Qth 
  of 
  that 
  month 
  to 
  fire 
  

   thirteen 
  charges 
  in 
  one 
  day, 
  at 
  both 
  high 
  and 
  low 
  water, 
  using 
  

   sixteen 
  hundred 
  and 
  twenty-five 
  pounds 
  of 
  powder, 
  or 
  sixty-five 
  

   kegs 
  in 
  a 
  single 
  days 
  work. 
  

  

  When 
  operations 
  were 
  commenced 
  in 
  August, 
  there 
  was 
  but 
  

   fourteen 
  feet 
  of 
  water 
  on 
  the 
  rock 
  at 
  high 
  tide, 
  now 
  there 
  is 
  

   more 
  than 
  twenty-Jive 
  feet. 
  The 
  greater 
  the 
  depth 
  of 
  water 
  on 
  

   the 
  rock, 
  the 
  more 
  effective 
  is 
  the 
  force 
  of 
  the 
  explosions. 
  

  

  