﻿286 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  12 
  

  

  placed 
  directly 
  at 
  the 
  point 
  most 
  useful 
  in 
  marking 
  a 
  danger, 
  or 
  in 
  de- 
  

   fining 
  a 
  safe 
  course; 
  they 
  have 
  the 
  disadvantage 
  of 
  being 
  liable 
  to 
  

   be 
  displaced 
  or 
  sunk, 
  but 
  this 
  is 
  to 
  some 
  extent 
  overcome 
  by 
  improved 
  

   design, 
  heavier 
  moorings, 
  and 
  constant 
  watchfulness 
  by 
  the 
  Lighthouse 
  

   Service 
  vessels 
  and 
  people. 
  

  

  The 
  Service 
  has 
  about 
  120 
  vessels 
  in 
  commission, 
  light 
  vessels 
  or 
  

   floating 
  lighthouses, 
  and 
  tenders, 
  or 
  supply 
  steamers. 
  Both 
  of 
  these 
  

   classes 
  require 
  vessels 
  of 
  special 
  design. 
  Important 
  problems 
  of 
  naval 
  

   architecture 
  have 
  to 
  be 
  solved, 
  particularly 
  in 
  the 
  plans 
  for 
  the 
  light 
  

   vessels. 
  This 
  country 
  maintains 
  these 
  on 
  49 
  stations, 
  of 
  which 
  22 
  

   are 
  exposed 
  stations 
  in 
  the 
  open 
  sea. 
  To 
  remain 
  anchored 
  on 
  a 
  sta- 
  

   tion 
  off 
  the 
  coast, 
  exposed 
  to 
  the 
  full 
  force 
  of 
  storms, 
  is 
  a 
  service 
  

   not 
  expected 
  of 
  any 
  other 
  ship, 
  and 
  for 
  a 
  long 
  time 
  difficulty 
  was 
  had 
  

   in 
  designing 
  vessels 
  that 
  would 
  meet 
  the 
  requirements. 
  It 
  was 
  73 
  

   years 
  from 
  the 
  first 
  attempt 
  before 
  a 
  lightship 
  was 
  successfully 
  main- 
  

   tained 
  on 
  Diamond 
  Shoal 
  off 
  Cape 
  Hatteras, 
  and 
  because 
  of 
  this 
  diffi- 
  

   culty 
  elaborate 
  attempts 
  involving 
  possible 
  large 
  expenditures, 
  were 
  

   made 
  to 
  build 
  a 
  lighthouse 
  on 
  the 
  Outer 
  Diamond 
  Shoal. 
  In 
  the 
  

   design 
  of 
  lightships, 
  the 
  lines 
  are 
  shaped 
  to 
  control 
  the 
  rolling 
  and 
  the 
  

   easy 
  riding 
  of 
  the 
  vessel 
  in 
  a 
  seaway. 
  The 
  framing 
  is 
  heavy, 
  and 
  

   ample 
  water-tight 
  bulkheads 
  are 
  provided. 
  Flush 
  deck 
  construction 
  

   is 
  used 
  with 
  a 
  minimum 
  of 
  upper 
  works, 
  so 
  as 
  to 
  allow 
  seas 
  to 
  sweep 
  

   over 
  the 
  vessel. 
  The 
  bow 
  is 
  high 
  to 
  ride 
  the 
  seas. 
  The 
  largest 
  light 
  

   vessels 
  in 
  this 
  Service 
  are 
  only 
  about 
  135 
  feet 
  in 
  length. 
  They 
  are 
  

   moored 
  with 
  mushroom 
  anchors 
  up 
  to 
  7500 
  pounds 
  in 
  weight 
  on 
  the 
  

   exposed 
  stations, 
  with 
  heavy 
  mooring 
  chains, 
  180 
  fathoms 
  or 
  1,080 
  

   feet 
  in 
  length, 
  weighing 
  approximately 
  28,000 
  pounds. 
  The 
  chain 
  

   passes 
  through 
  a 
  hawse 
  pipe 
  in 
  the 
  stem, 
  near 
  the 
  water 
  line, 
  so 
  that 
  

   the 
  vessel 
  may 
  ride 
  as 
  easily 
  as 
  possible. 
  Lightships 
  anchored 
  in 
  the 
  

   more 
  exposed 
  positions 
  are 
  subjected 
  to 
  most 
  severe 
  treatment 
  by 
  

   the 
  combination 
  of 
  gales 
  and 
  cross 
  currents, 
  and 
  every 
  precaution 
  is 
  

   taken 
  to 
  secure 
  their 
  safety, 
  and 
  their 
  remaining 
  on 
  station. 
  The 
  

   modern 
  vessels 
  are 
  self-propelled, 
  and 
  the 
  strain 
  on 
  the 
  mooring 
  chains 
  

   during 
  storms 
  is 
  relieved 
  by 
  judicious 
  use 
  of 
  the 
  propelling 
  machinery. 
  

   At 
  a 
  few 
  stations 
  a 
  spherical 
  mooring 
  buoy 
  is 
  shackled 
  to 
  a 
  submerged 
  

   portion 
  of 
  the 
  chain 
  to 
  carry 
  a 
  part 
  of 
  the 
  weight 
  and 
  ease 
  the 
  strains 
  

   due 
  to 
  the 
  vessel 
  surging. 
  

  

  The 
  lighthouse 
  tenders 
  are 
  the 
  supply 
  and 
  construction 
  vessels, 
  

   and 
  care 
  for 
  the 
  buoys 
  and 
  lightships. 
  They 
  are 
  equipped 
  with 
  

   powerful 
  hoisting 
  gear 
  for 
  handling 
  the 
  heavy 
  buoys 
  and 
  moorings, 
  

  

  