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Digitized  by  the  Internet  Archive 
in  2011  with  funding  from 
The  Library  of  Congress 


http://www.archive.org/details/cruiseofschoolshOOnewy 


U-  .  jv  .,. 


Department  of  ]JuOftc  dOaritics  aiif)  (Coirection 


CEUISE 


SCHOOL-SHIP  "MERCURY" 


TROPICAL  ATLANTIC  OCEAN. 


J       1870-1871.      ^L,^^^ 


^  ^  ^ 


KEW  YOEK: 

THE    KEW    YORK    PRINTING-    COMPANY, 

Nos.  81,  83,  AND  85  Centre  Street. 

1871. 


\ 


REPORT 


Department  of  Public  Chaeities  and  Correction,  ) 

Corner  of  Third  avenue  and  Eleventh  street^  V 

Kew  YorKj  September  I25  1871.  ) 

Hon.  A.  Oakey  Hall,  Mayor  : 

Sir— The  Commissioners  of  Public  Charities  and  Correction  respect- 
fully submit  a  report  of  the  practice-cruiso  of  the  school-ship  Mercury, 
from  her  anchorage  ground  at  Hart's  Island  to  Sierra  Leone,  and  from 
thence  via  St.  Thomas  to  this  port,  during  the  winter  of  1870-71. 

But,  before  narrating  the  history  of  the  cruise,  it  is  proper  to  state 
more  specifically  than  in  the  annual  report  the  reasons  which  induced 
the  Commissioners  to  establish  a  nautical  school,  and  to  describe  the 
character  of  the  boys  who  are  assigned  to  it.  With  the  increase  of  the 
population  of  the  city  there  had  been  a  greatly  increased  number  of 
boys  committed  to  the  care  of  the  Commissioners  by  the  magistrates, 
for  slight  misdemeanors  and  vagrancy.  Others,  and  in  large  numbers, 
had  been  committed  by  their  parents  as  incorrigible,  or  because  of  evil 
associates,  who  were  leading  them  to  ruin.  These  boys  were  at  first 
sent  to  the  Industrial  Schools  on  Hart's  Island,  but  the  number  in- 
creased so  rapidly  that  the  Commissioners  w^ere  embarrassed  as  to  the 
disposition  which  should  be  made  of  them. 

They  could  not  without  a  long  probationship  be  recommended  as  ap- 
prentices, because  of  tlieir  wayward  and  reckless  character,  nor  could 
they  be  discharged  without  the  probability  that  they  would  again 
become  vagrants,  or  fall  into  their  former  wicked  associations.  Under 
these  circumstances  it  was  deemed  expedient  to  establish  a  nautical 
school,  as  well  for  the  purpose  of  relieving  the  department  of  a  con- 
stantly increasing  number  of  unruly  boys,  as  of  providing  for  them  a 
sure  and  honest  means  of  livelihood  suited  to  their  adventurous  spirit. 


Wlieii  the  school  was  establisliecl  it  was  contemplated  from  considera- 
tions of  economy  to  teach  them  the  rudiments  of  seamanship  while  the 
ship  was  at  anchor  in  the  harbor,  and  by  occasional  trips  of  short 
duration  at  sea,  during  the  summer  months  ;  and  this  method  was  fur- 
ther commended  by  the  consideration  that  the  boys  w^ould  be  under 
the  direct  and  constant  supervision  of  the  Commissioners. 

But  the  experience  of  a  few  months  demonstrated  that  the  oiily  effec- 
tual mode  of  instruction  is  the  continuous  handling  of  a  sliip  at  sea, 
and  that  the  manifold  duties  of  a  thorough  seaman  can  oidy  be  learned 
by  actual  service. 

The  cruise,  of  which  the  following  papers  constitute  the  report,  was 
made  in  pursuance  of  these  convictions  and  for  the  purpose  of  qualify- 
ing the  boys  for  immediate  entrance  on  their  return  into  the  service  of 
the  navy  or  mercantile  marine.  In  this  respect  the  result  of  the  cruise 
was  highly  satisfactory,  for  of  the  crew  of  two  hundred  and  fifty-eight 
boys  over  one  hundred  were,  in  the  opinion  of  the  captain,  capable  on 
the  return  of  the  ship  of  discharging  the  duties  of  ordinary  sea- 
men. 

It  is  proposed  to  apply  to  Congress  at  its  next  session  for  authority  to 
be  vested  in  the  Secretary  of  the  Navy  to  discriminate  in  enlistments 
in  favor  of  boys  who  have  been  educated  in  school-ships. 

The  exploration  of  the  ocean  has  become  an  object  of  deep  interest 
to  governments  as  well  as  to  men  of  science.  The  United  States  Coast 
Survey,  under  the  wise  direction  of  Professor  Baclie,  and  now  of  Pro- 
fessor Pierce,  has  for  many  years  been  diligently  engaged  in  adding  to 
the  limited  information  possessed  of  deep-sea  soundings,  temperatures, 
and  currents,  and  more  recently  the  British  Government,  under  the  su- 
pervision of  Dr.  Carpenter,  has  solved  several  problems  of  scientific 
importance,  added  largely  to  the  stock  of  general  knowledge,  and  made 
discoveries  which  will  be  of  practical  benefit  to  commerce  and  naviga- 
tion. 

With  the  hope  that  the  cruise  of  the  Mercury  might  be  made  to  con- 
tribute something  of  value  to  science.  Captain  Giraud  w^as  directed  to 
obtain  a  series  of  soundings  on  the  line  of  or  near  the  Equator,  from  the 


coast  of  Africa  to  the  mouth  of  the  Amazon,  to  observe  the  set  of  the 
surface  currents,  and  the  temperature  of  the  water  at  various  depths. 
The  following  is  a  copy  of  his  letter  of  instructions : 


Department  of  Public  Charities  and  Correction,  ) 
New  York,  December  13,  1870.  f 

Sir — You  will  proceed  to  sea,  in  command  of  the  Mercury,  on  the 
16th  instant,  by  way  of  Montauk  Point,  and  cruise  between  the  latitudes 
10°  north  and  5°  south  of  the  equator,  and  of  longitude  from  5°  east  to 
45°  west  of  Greenwich,  until  the  10th  of  March,  when  you  will  return 
to  your  anchorage  at  Hart's  Island,  unless  on  your  approach  to  the  coast 
you  shall  deem  it  prudent,  from  stress  of  weather,  to  enter  at  Sandy 
Hook. 

You  will  keep  at  sea  as  much  as  possible,  going  into  port  only  to 
obtain  water  and  provisions  or  for  repairs.  As  often  as  may  be  prac- 
ticable, you  will  forward  to  this  office  detailed  reports  of  the  health  of 
the  officers  and  crew,  and  the  progress  made  By  the  boys  in  seamanship 
and  in  their  studies  at  school. 

The  routine  duties  of  the  ship,  as  laid  down  in  the  rules  for  the  edu- 
cation of  the  boys  in  seamanship,  will  be  strictly  adhered  to. 

You  will,  as  often  as  may  be  practicable,  take  soundings  of  the  bed 
of  the  Atlantic,  on  or  near  the  line  of  the  Equator,  from  the  coast  of 
Africa  to  the  mouth  of  the  Amazon. 

You  will  also  frequently  observe  and  record  the  temperature  of  the 
ocean  at  the  surface  and  at  twenty,  fifty,  one  hundred,  and  two  hun- 
dred fathoms,  and  obtain  specimens  of  water  at  those  depths,  which 
you  will  cause  to  be  evaporated  on  board,  and  the  solid  matter  ana- 
lyzed, or  you  will  bring  the  specimens  home  in  bottles  provided  for  the 
purpose. 

You  will  also  obtain  sea-plants  from  as  great  depths  as  may  be  prac- 
ticable, together  with  animalculse  and  other  minute  forms  of  animal 
life,  which  you  will  preserve  or  cause  accurate  drawings  thereof  to  be 


made,  for  wliicli  purpose  you  will  be  furnished  with  a  microscope  of 
large  powers. 

An  accurate  knowledge  of  the  set  and  velocity  of  currents  is  of 
great  importance  to  commerce.  You  will  be  pleased  to  note  and  care- 
fully determine  the  direction  of  all  currents  with  which  you  may 
fall  in. 

A  favorable  opportunity  will  be  afforded  to  note  with  approximate 
accuracy  their  rate  and  direction  when  you  are  engaged  in  taking  your 
deep-sea  soundings  from  an  open  boat. 

It  is  desirable  that  the  misplaced  reliance  of  many  navigators  on 
dead-reckoning  may  be  demonstrated,  and  to  this  end  you  will  fre- 
quently, when  you  have  determined  your  position  by  astronomical 
observation,  throw  your  registering  log  and  let  it  remain  in  the  water 
for  twenty-four  or  forty-eight  hours,  or  until  you  have  taken  another 
observation,  when  you  will  compare  the  progress  you  have  made  by 
dead  reckoning  with  your  actual  progress,  as  determined  by  observation. 

While  the  chief  object  of  the  cruise  of  the  Mercury  will  be  to  per- 
fect the  boys  under  your  command  in  seamanship,  the  Commissioners 
indulge  the  hope  that,  by  the  careful  observation  of  yourself  and  officers, 
the  interests  of  commerce  may  be  promoted,  and  the  cause  of  science 
advanced. 

Yery  respectfully, 

ISAAC   BELL, 

President, 
To  Caj^tain  Piekee  Giraud, 

Coininanding  ScJiool-sJiip  Mercitry. 

The  ship  sailed  from  Hart's  Island  on  the  20th  December,  1870,  and, 
after  stopping  at  Madeira  and  the  Canary  Islands,  arrived  at  Sierra 
Leone  on  the  14th  of  February. 

On  the  21st  of  February  she  left  Sierra  Leone,  and  on  the  22d  Cap- 
tain Giraud  connnenced  his  deep-sea  soundings,  which  he  continued  in 
nearly  a  straight  line  to  the  Island  of  Barbadoes,  a  distance  of   about 


2,800  miles.  His  soundings  range  from  500  fathoms  to  3,100  fathoms, 
or  3J-  miles,  from  which  depths  he  brought  up  in  most  instances  speci- 
mens of  bottom.  The  current  observations  will  be  of  value  in  the 
navigation  of  the  South  Atlantic,  and  the  ascertained  temperatures  of 
the  water  at  from  200  to  500  fatlioms  are  confirmatory  of  the  theory  that 
a  cold  current  from  the  Poles  underlies  the  surface-waters  of  the  tropi- 
cal seas. 

The  daily  meteorological  observations,  the  direction  and  velocity  of 
currents,  and  the  temperatures  of  the  oc^an  at  various  depths,  are  set 
forth  in  his  report,  which  is  herewith  annexed.  These  papers,  together 
with  the  specimens  obtained  from  the  bed  of  the  ocean  and  of  sea- 
w^ater,  were  placed  in  the  hands  of  Professor  Henry  Draper  of  the  Kew 
York  University  for  examination. 

Professor  Draper's  report,  which  is  herewith  submitted,  contains 
precise  tabulated  statements  of  the  meteorological  observations  of  the 
voyage,  of  the  direction  and  velocities  of  the  currents,  and  of  the 
temperatures  at  the  several  depths  obtained,  together  with  an  analysis 
of  the  specimens  of  water  from  various  depths.  The  report  also  con- 
tains a  diagram  of  the  bed  of  the  Atlantic,  i'rom  Sierra  Leone  to 
Barbadoes,  as  established  by  the  soundings,  and  is  replete  with  interest- 
ing disquisitions  on  all  the  questions  of  deep-sea  explorations.  The 
specimens  of  animal  life  which  were  obtained  from  the  bottom  were 
forwarded  for  examination  by  Professor  Draper  to  Dr.  Carpenter.  He 
reports  that  they  are  the  ordinary  forms  of  deep-sea  foraminifera. 
With  the  specimens  Professor  Draper  also  sent  a  table  of  the  tempera- 
tures, and  in  respect  to  them  Dr.  Carpenter  remarks,  "  that  they  are  of 
great  interest,  and  especially  those  at  one  hundred  and  two  hundred 
fathoms.  They  show,''  he  continues,  "  how  thin  is  the  surface  stratum 
affected  by  the  gulf -stream,  or  by  direct  solar  radiation.  The  sudden 
drop,"  he  remarks,  *^  in  the  temperature  at  two  hundred  fathoms,  between 
17°  46'  west  longitude,  and  19°  36'  west  longitude,  and  the  continuation 
of  this  reduction  with  the  increased  westing  as  far  as  50°  38'  is  a  very 
curious  phenomenon,  and  I  cannot  help  connecting  it  with  some  great 
oceanic  movement,  especially  as  at  68°  47'  west  longitude,  and  at  83° 
the  higher  temperatures  reappear.  I  trust  that  hereafter  much  atten- 
tion will  be  given  to  this  point." 


Tlio  conclusion  at  which  Professor  Draper  has  arrived,  from  a  care- 
ful examination  of  the  results  obtained,  is  that  there  exists,  all  over  the 
bottom  of  the  Atlantic  and  Caribbean  Sea,  a  stratum  of  cold  water, 
and  that  the  ci'uise  of  the  Mercury  must  be  considered  as  offering  con- 
firmatory proof  of  the  correctness  of  Dr.  Carpenter's  theory,  drawn 
from  the  cruises  of  the  Englisli  exploring  vessels,  that  there  is  a  general 
movement  of  the  lower  w^aters  of  the  Atlantic  towards  the  Equator, 
and  a  corresponding  flow  of  the  surface-waters  towards  the  Poles. 

The  object  of  the  cruise  was,  as  has  been  stated,  to  perfect  the  boys 
in  seamanship.  The  scientific  explorations  were  incidental  and  subsi- 
diary, but  enough  has  been  accomplished  to  encourage  the  hope  that  the 
practice  voyages  of  the  Mercury  may  be  made  to  contribute  to  the 
stock  of  knowledge,  and  help  to  explain  the  mysteries  of  the  Great 
Deep. 

The  experiment  of  the  school-ship,  as  a  Reformatory,  has  thus  far 
been  satisfactory.  There  is  reason  to  believe  that  it  is  the  most  effec- 
tive mode  to  reclaim  erring  boys,  whose  errors,  caused  by  the  love  of 
adventure,  by  evil  associations,  or  ungovernable  tempers,  are  fast  hn- 
pelling  them  to  ruin.  Brought  under  the  inflexible  discipline  of  a 
ship  in  actual  service,  they  are  taught  in  a  few  months  the  duties  of  a 
profession,  wdiich  directs  and  gratifies  their  love  of  adventure,  and  pro- 
vides for  them  the  means  of  an  honest  and  useful  livelihood. 

Eespectf  ully  submitted. 

Isaac  Bell,  1  ^>         .    . 

Owen  W.  Brennan,     (^o^J^i^^^^ners 

Jas.  B.  Nicholson,'  V  ,f  ^^^^^^  , 
Alex.  Feear,  |    <^f^r^t^e8(lnd 

James  BowEN,  J      (Correction. 


int/i  the  res(>ccts  of 

Professor    HENRY    DRAPER,     M.     D. 


University  of  the  City  of  Nnv   York. 


REPORT 


oinmififiioner^  of  ;)ubl^  lluiritij^  am!  H^orrfctiou 


CITY   OF  NEW   YORK, 

ON    THE    CHEMICAL    AND    PHYSICAL    FACTS    COLLECTED    FROM   THE 

DEEP    SEA    RESEARCHES 

MADE  DURING  THE  VOYAGE  OF  THE 

NAUTICAL  SCHOOL-SHIP  "MERCURY," 

UNDERTAKEN  BY  THEIR  ORDER  IN  THE 

TROPICAL  ATLANTIC  AND  CARIBBEAN  SEA, 

1870-71. 

By  henry  DEAPEE,  M.D., 

Professor  of  Analytical  Chemistry  and  Physiology  in  the  University  of  New  York. 


11 


REPORT. 


GontenU — Introduction — Outline  op  voyage — Its  three  stages— General  air  tem- 
perature—Barometric TABLE — Pressure  increases  on  nearing  America — Tables 
OF  sea  currents— Collection  of  samples  op  water,  and  necessary  precau- 
tions—Effects of  pressure  on  gaseous  and  saline  ingredients- Determination 
OP  specific  gravity  of  samples  collected,  with  table — Thermometric  observa- 
tions, with  description  of  registering  thermometer — Tables  op  air  tempera- 
tures,   AND    OP    water    at     VARIOUS    DEPTHS  —  DISCUSSION     OF     SOUNDINGS  —  CrOSS- 

section  of  Atlantic— Suggestions  of  effect  of  Amazon  and  Orinoco — Tempera- 
ture AND  specific  GRAVITY  OP  WATER  INCREASE  TOWARD  WeST — PrOOF  THAT  A 
STRATUM  OF  COLD  WATER  EXISTS  AT  THE  BOTTOM  OP  THE  TROPICAL  ATLANTIC— EXAM- 
INATION   OF   DISSOLVED   GASES,    OF  ORGANIC    MATERIAL— SPECTRUM   ANALYSIS   OF    SOLID 

RESIDUES — Organic  remains. 

The  Commissioners  of  Public  Charities  and  Correction,  having  sub- 
mitted to  me  for  examination  certain  documents  and  specimens  con- 
nected with  the  voyage  of  the  nautical  school-ship  Mercury,  I  have 
the  honor  to  make  thereupon  the  following  report ; 

Much  attention  has  recently  been  given  to  deep-sea  researches,  in 
consequence  of  the  investigations  made  by  the  United  States  Govern- 
ment on  its  coast,  and  by  Dr.  Carpenter,  Mr.  Gwyn  Jeffreys,  and  Pro- 
fessor Wyville  Thomson,  in  the  North  Atlantic  and  the  Mediterranean 
Sea.  IN^ot  only  have  many  of  the  facts  so  ascertained  been  corroborated 
by  this  voyage  of  the  Mercury,  but  the  Commissioners,  by  authori- 
zing it,  have  also  added  much  that  is  new  and  interesting  to  our 
knowledge  of  the  physical  condition  of  the  deep  sea. 

The  voyage  of  the  ,  Mercury  may  be  divided  into  three  stages : 
1st,  from  K'ew  York,  by  way  of  the  Madeira  and  Canary  Islands,  to 
Sierra  Leone  ;  2d,  from  Sierra  Leone,  tlu'ough  the  tropical  Atlantic,  to 
Barbadoes ;  3d,  from  Barbadoes,  through  the  Caribbean  Sea,  to  the 
north  of  Cuba,  and  thence,  along  the  coast  of  the  United  States,  back 
to  New  York. 

The  chief  scientific  interest  of  this  voyage  is  connected  with  its 
second  and  part  of  its  third  stage. 


12 

The  sliip  left  Kew  York  on  December  20, 1870.  Slie  reached  Funchal 
(Miideira  Islands)  on  January  17,  1871  ;  Las  Palmas,  in  the  Canaries, 
on  January  2-i,  and  Sierra  Leone  on  February  14.  On  the  21st  of  that 
montli  she  sailed  for  Barbadoes,  and  reached  that  island  on  the  morn- 
ing of  March  17.  She  sailed  from  Barbadoes  on  Marcli  2'4j  and  ar- 
rived in  New  York  on  April  21. 

It  is  necessary  to  give  these  particulars,  with  a  view  of  indicating 
that  tlie  voyage  was  made  in  the  winter  season  of  the  year,  the  season 
of  the  lowest  air  temperatures.  The  mean  temperature  of  the  air  at  8 
P.M.,  while  at  Funchal,  was  70|-°,  the  maximum  being  70°  aud  the  min- 
imum 6S°.  "While  at  Las  Palmas  it  was  63°,  the  maximum  being  ()Q° 
and  the  minimum  57°.  While  at  Sierra  Leone  it  was  83°,  the  maximum 
being  85°,  the  minimum  79°.  In  the  passage  across  the  Atlantic,  from 
Sierra  Leone  to  Barbadoes,  the  mean  temperature  was  7S|-°  ;  the  max- 
ima were  on  leaving  the  African  and  on  approaching  the  American 
coast.  For  nearly  a  fortnight,  during  the  mid-passage,  the  variations 
were  included  between  76°  and  79°. 

In  this  report  the  degrees  of  temperature  are  according  to  Fahren- 
heit's scale.  Though  the  thermometer  was  observed  regularly,  three 
times  each  day,  at  midnight,  at  noon,  and  at  8  p.m.,  I  have  adopted  the 
latter  only,  since  it  is  recognized  by  meteorologists  that  the  tempera- 
ture at  8  P.M.  very  closely  approaches  the  mean  for  the  entire  day. 

As  regards  the  barometer,  the  following  table  v^ill  show  its  height, 
as  determined  by  three  observations  each  day  during  the  passage  from 
Sierra  Leone  to  Barbadoes  : 


13 


Table   I. 

Barometric  Ohservations  from  Sierra  Leone  to  Bai'ladoes. 


DATE. 

MIDNIGHT. 

NOON. 

8   P.M. 

Feb      21     

29.64 
29.70 
29.76 
29.70 
29.68 
29.74 
29.76 
29.74 
29.68 
29.72 
29.72 
29.72 
29.72 
29.80 
29.78 
29.78 
29.79 
29.76 
29.77 
29.74 
29.78 
29.82 
29.80 
29.78 

29.66 
29.68 
29.70 
29.68 
29.68 
29.74 
29.76 
29.68 
29.66 
29.68 
29.70 
29.74 
29.73 
29.78 
29.78 
29.76 
29.79 
29.76 
29.73 
29.76 
29.76 
29.81 
29.80 
29.78 

29  60 

Feb      22 

29  70 

Feb.     23 

29  74 

Feb      24           

29  66 

Feb.      25 

29  70 

Feb.      26 

20  74 

Feb.      27 

29  76 

Feb.      28 

29  64 

Marcli    1 . 

29  66 

March    2 

Marcli    3   

29.68 
29  70 

March    4 

29  72 

29.74 

29  78 

March    6 

March    7 

29  78 

March    8 

29  76 

March    9 . .             .... 

29  78 

March  10 

29  76 

March  11 

29  73 

March  12 

29  76 

March  13 

29  76 

March  14 

29  82 

March  15 

29  74 

March  IG 

29  80 

Mean  of  all  the  observations '. . . 

29.745 

29.733 

29.730 

From  this  it  will  be  seen  how  small  the  barometric  variations  were. 
Examining,  for  instance,  those  of  8  p.m.,  the  minimum  was  only  J/-Q-inch 
below,  and  the  maximum  y|-Q-inch  above  tlie  mean.  It  may  also  be 
remarked  that,  in  a  general  manner,  the  pressure  of  tlie  air  increased 
on  Hearing  the  American  coast. 

On  leaving  the  African  coast  the  atmosphere  was  liazj,  as  is  usual 
in  that  region.  On  March  5  the  north-east  trade  winds  wxre  struck, 
and  they  accompanied  the  ship  to  Barbadoes.  Previously  to  reaching 
them  her  mean  daily  progress  had  been  only  57  miles  ;  after  that  time 
it  was  187  miles. 

The  ocean  currents,  as  reported  on  the  days  when  other  important 
observations  were  made,  are  shown  by  the  following  table : 


14 

Table   II. 

Direction    and   Velocity   of    Currents    hetioeen    Sierra    Leone    and 

Barhadoes. 


Date. 

Direction, 

Velocity. 

1 

Date. 

Direction. 

Velocity. 

Feb.     23 

S.W. 

y  knot. 

1 

March    4 

S. 

K  knot. 

"      25 

S.  S.W. 

X  knot. 

''     10 

S.W. 

K  knot. 

'*      26 

S.  by  W. 

}4  knot. 

"     11 

S.W.  by  W. 

%  knot. 

"      27 

S 

}4  knot. 

"     13 

W.  S.W. 

%  knot. 

"      28 

S.  by  W. 

}4  knot. 

•'     14 

W.  S.W. 

i|  knot. 

March  3 

S.  S.W. 

%  knot. 

''     15 

W. 

y^  knot. 

Table   III. 

Direction  and  Velocity  of  Currents  in  the  West  India  Seas. 


Date. 

Direction. 

Velocity. 

Date. 

Direction. 

Velocity. 

April  4 

W. 
W. 

W.  by  N. 
W.  by  ]^. 

y  knot. 
}4  knot. 
y  knot. 
3>|  knot. 

April  8 

W.  N.W. 

W. 

S.W. 

N.  N.  W. 

y  knot. 
}i  knot. 

"    5..".".".'"'.'.'. 

''     9 

"6 

"   11 

%  knot. 

"   13 

Jl"  knot. 

During  the  second  stage  of  her  voyage  the  ship's  track  was  over  a  par- 
allel included  substantially  between  the  eleventh  and  thirteenth  degrees 
of  north  latitude.  She  obtained  soundings  at  various  depths,  from  290  to 
3,100  fathoms,  and  on  eleven  occasions  specimens  from  the  bottom.  In 
the  third  stage  of  her  voyage,  while  in  the  West  Indian  seas,  three 
other  bottom-specimens  were  secured.  The  apparatus  used  was  Brooks' 
detaching  apparatus,  with  two  thirty-two  pound  shot.  The  sounding- 
line  was  cotton  cord,  one-seventh  of  an  inch  in  diameter.  All  the 
soundings  were  made  from  a  boat.  On  March  6,  the  maximum  depth 
of  3,100  fathoms  in  the  Atlantic  was  reached,  but  on  reeling  in,  the 
line  unfortunately  parted,  and  2,200  fathoms  were  lost.  This  is  one 
of  the  deepest  accurate  soundings  ever  made. 

Samples  of  water  from  the  surface,  and  also  from  deptlis  varying 
from  two  hundred  to  five  hundred  fathoms,  as  shown  in  Table  lY., 


15 

were  procured.  The  temperature  of  the  sea,  both  at  the  surface  and 
at  those  depths,  was  ascertained.  The  samples  of  water  were  collected 
in  the  usual  apparatus,  a  metal  cylinder,  presently  to  be  more  particu- 
larly described,  having  at  its  bottom  and  top  valves  opening  upwards. 
By  this  contrivance  as  water  obtained  from  a  great  depth  is  drawn 
toward  the  surface,  it  and  its  included  gases  have  liberty  to  expand,  the 
excess  escaping  through  the  upper  valve.  If  such  provision  were  not 
made,  the  cylinder,  no  matter  how  strong  it  might  be,  would  unavoida- 
bly be  burst  open.  It  should  be  borne  in  mind  that  the  compressil)ility 
of  water  is  about  ^^^^q  for  each  atmosphere  of  pressure  it  sustains,  and 
at  depths  such  as  were  here  reached  the  pressure  was  about  1,250 
,  pounds  per  square  inch,  or  more  than  eighty  atmospheres. 

There  are  certain  precautions  which  must  be  attended  to  in  the  use 
of  this  collecting  cylinder.  These  more  particularly  refer  to  securing 
the  perfect  action  of  its  valves.  It  is  intended  that  these  valves  should 
remain  open  during  the  entire  period  of  the  descent  of  the  cylinder  in 
the  sea,  and  remain  closed  during  its  ascent,  except  in  so  far  as  the 
upper  one  may  be  opened  by  the  interior  pressure  to  allow  the  excess 
of  included  water  and  its  dissolved  gases  to  escape.  Obviously,  how- 
ever, these  conditions  may  be  interfered  with  by  a  variety  of  accidental 
causes,  such  as  the  adhesion  of  the  valves  by  verdigris  or  other  im- 
purity, or  by  the  cylinder  assuming  an  inclined  instead  of  a  vertical 
position. 

The  constitution  of  the  water  as  it  exists  at  great  depths  is  not  cor- 
rectly represented  by  the  samples  thus  obtained.  A  considerable  por- 
tion of  the  gases  dissolved  therein  may  escape,  as  j  iist  stated,  under  the 
relief  of  pressure  as  the  cylinder  is  drawn  toward  the  surface,  and  hence 
examinations  of  such  samples,  as  regards  their  gaseous  ingredients,  are 
liable  to  be  deceptive.  The  low  temperature  and  great  pressure  of 
these  deep  strata,  moreover,  increase  the  solvent  power  of  the  water 
over  gases,  and  this  power  is  diminished  as  the  cylinder  is  brought  into 
the  warmer  strata  above,  and  into  the  open  air.  Even  the  saline  ingre- 
dients will  suffer  disturbance  when  they  are  held  in  solution  by  gases 
that  will  thus  escape.  For  instance,  this  is  the  case  with  carbonate  of 
lime.     'No  method  has  hitherto  been  practised  which  furnishes  a  means 


16 

of  obtaining  samples  of  sea-water  from  great  depths  with  their  true 
constitution  undistui-bed,  though  obviously  an  apparatus  might  be  de- 
vised which  would  accomplish  that  purpose. 

As  thus  procured  the  specimens  of  water  were  preserved  in  well- 
corked  glass  bottles  with  sealing-wax  on  the  cork,  until  submitted  to 
me  for  examination.  These  samples  are  fifty  in  number,  divisible  into 
two  groups,  surface  and  deep  ones,  from  each  locality.  In  quantity 
they  vary  from  four  to  sixteen  ounces. 

I  have  determined  the  specific  gravities  of  these  specimens  and  most 
of  them  are  inserted  in  Table  lY.  To  insure  correct  results  sevei-al 
precautions  must  be  taken.  The  difference  of  density  between  water 
collected  at  the  surface  and  that  from  great  depths  is  so  small  that  a 
slight  variation  in  temperature  is  sufticient  to  mask  it  completely. 
Hence  it  is  only  in  laboratories,  Avhei-e  means  can  be  used  to  provide 
against  temperature  variations  and  where  balances  of  precision  can  be 
employed,  that  accurate  results  can  be  obtained.  It  will,  therefore,  be 
imderstood  that  in  the  experiments  upon  which  the  following  table  has 
been  constructed  such  precautions  have  been  carefully  attended  to.  It 
may  be  remarked  that  on  board  ship,  where,  on  account  of  the  motion, 
balances  cannot  be  applied,  the  hydrometer  maist  be  resorted  to,  but 
any  conclusions  drawn  from  its  indications  should  be  accepted  with 
much  reserve.  It  is  difiicult  to  read  its  scale  wutli  exactness,  and  it  is 
almost  impossible  under  such  circumstances  to  secure  the  proper  tem- 
perature conditions.  In  some  of  the  more  interesting  instances  the 
variation  of  a  single  degree  in  the  temperature  would  lead  to  a  conclusion 
in  direct  opposition  to  the  true  one. 


17 


Table  IY. 
Kcijic  Gravity  of  Samples  of  Sea-icater  at  75' 


DATE. 

LATITUDE. 

LONGITUDE. 

DEPTH. 

SPECIFIC 
GKAVITY. 

Feb.    25       

9°  14' 

9°  14' 
10°  04' 
10°  04' 
10°  42' 
10°  42' 
11°  35' 
11°  35' 
11°  39' 
11°  39' 
11°  35' 
11°  35' 
11°  06' 
11°  06' 
12°  38' 
12°  38' 
13°  02' 
13°  02' 
13°  06' 
13°  06' 
13°  08' 
13°  08' 
12°  55' 
12°  55' 
17°  13' 
17°  13' 
17°  08' 
17°  08' 
17°  09' 
17°  09' 
17°  27' 
17°  27' 
17°  27' 
18°  11' 
18°  11' 
19°  12' 
19°  12' 
20°  17' 
20°  17' 
20°  48' 
20°  48' 
23°  19' 
,  23°  19' 
23°  19' 

17°  09' 

17°  09' 
17°  33' 
17°  33' 
17°  46' 
17°  46' 
18°  20' 
18°  20' 
18°  33' 
18°  33' 
19°  35' 
19°  35' 
21°  55' 
21°  55' 
42°  31' 
42°  31' 
44°  51' 
44°  51' 
50°  38' 
50°  38' 
53°  48' 
53°  48' 
56°  46' 
56°  46' 
67°  29' 
67°  29' 
68°  48' 
68°  48' 
71°  47' 
71°  47' 
74°  33' 
74°  33' 
74°  33' 
76°  00' 
76°  00' 
77°  54' 
77°  54' 
80°  35' 
80°  35' 
83°  02' 
83°  02' 
84°  17' 
84°  17' 
84°  17' 

Surface 

1026  72 

Feb.    25  

200  fathoms 

Surface 

1026  68 

Feb     26 

1026  42 

Feb     26     

200  fathoms 

Surface 

1026  50 

Feb.    27  

1026  72 

Feb.    27 

200  fathoms 

Surface 

1026  66 

March  1 

1026  53 

March  1 

200  fathoms 

Surface 

1026  53 

March  2 

1026  80 

March  2           

200  fathoms 

Surface   ... 

1026  80 

March  3   

1026  76 

March  3 

200  fathoms 

Surface 

1027  00 

March  4 

1026  92 

March  4  

200  fathoms 

Surface 

1026  77 

March  10 

1027  28 

March  10 

200  fathoms 

Surface 

1027  32 

March  11 

1027  10 

March  11 

200  fathoms.    . .  . 
Surface 

1027  28 

March  12 

1026  58 

March  12 

200  fathoms 

Surface           , 

1026  81 

March  13 

1026  72 

March  13 

420  fathoms 

1026  88 

March  15 

1026  53 

March  15 

100  fathoms 

S\irface 

1027  03 

April      4 

1026  83 

April      4 

400  fathoms 

Surface 

1026  87 

April      5 

1026  78 

April      5 

200  fathoms 

Surface 

1026  83 

April      6 

1026  87 

April      6 

(9)       

1026  79 

April      7 

Surface     . .  . 

1026  88 

April      7 

300  fathoms 

400  fathoms 

Surface 

1027  03 

April      7 

April      8 

1027.16 

1026  88 

April      8 

200  fathoms 

Surface 

1026  83 

April      9 

1027  04 

April      9 

200  fathoms 

Surface 

1026  96 

April    10 

1027  56 

AprH    10 

100  fathoms 

Surface 

1027  48 

April    11 

1027  08 

April    11 

200  fathoms 

Surface 

1027  04 

AprU    13 

1027  16 

AprU    13 

100  fathoms 

200  fathoms 

1027  20 

April    13 

1027  16 



Tlie  temperatures  under  the  sea-surface  were  obtained  by  a  self- 
registering  thermometer  of  the  form  known  as  Six's  construction.  It 
had  no  provision  to  protect  it  from  variations  of  pressure.     Compensa- 

2 


18 


tion  for  tliese  variations  must  be  determined  in  tlie  case  of  each  indi- 
vidual instrument,  for  the  amount  of  this  error  will  vary  with  the 
varying  thickness  of  the  glass,  its  form,  and  its  power  of  resisting  com- 
pression. In  the  experiments  made  by  Dr.  Miller  on  self-registering 
thermometers  for  deep  sea  sounding,  published  in  the  report  of  the 
Meteorological  Committee  of  the  lloyal  Society  for  18G9,  it  is  show^n 
that  certain  nnprotected  thermometers  submitted  to  a  pressure  of  two 
and  one  half  tons  per  square  inch  in  a  hydraulic  press,  though  made 
wdth  bulbs  of  nnusual  thickness,  would  indicate 
temperatures  from  6j\°  to  8j\°  too  higli,  and  in 
other  experiments  when  the  pressure  was  raised  to 
three  tons  on  tlie  inch  the  error  was  ll-J-°.  In  these 
instances,  however,  a  part  of  the  rise,  perhaps  as 
mnch  as  1-^-°,  was  due  to  the  heat  disengaged  from 
the  water  itself  in  the  act  of  compression.  In 
most  of  the  sul)joined  observations,  the  depth  not 
exceeding  200  fathoms,  the  pi-essure  upon  the  ther- 
mometer was  one  quai'ter  of  a  ton  per  square  inch. 
In  the  apparatus  used  on  board  the  Mercury,  the 
thermometer  was  inclosed  in  the  water-collecting 
cylinder.  It  was,  as  in  Six's  form,  alcoholic,  the 
reservoir  consisting  of  a  tube  about  five  inches  long 
and  one-third  of  an  inch  in  diameter,  made  of  pretty 
substantial  glass,  and,  though  the  influence  of 
pressure  upon  it  has  not  yet  been  determined  ex- 
perimentally, tliere  is  reason  to  suppose  that  at  the 
depths  in.  question  the  en'or  would  not  exceed  one 
or  two  degrees.  No  index  error  was  found  on 
comparing  this  instrument  with  a  standard  Kew. 


The  wnter-collecting  cylinder  consisted  of  a  copper 
tube  thirteen  inches  long  and  one  and  three  quar- 
ters in  diameter,  weiglited  witli  a  hollow  cone  of 
lead  at  its  lower  extremity.  The  valves  above  and 
below  were  one  inch  in  diameter.  In  w^hat  may  be 
called  the  front  of  the  cylinder  there  were  inserted 
SECTION   OF   WATER-COL- strips  of  platc  glass,  through  which  the  indications 


LECTING  CYLINDER  AND 
THERMOMETER. 


of  the  thermometer  might  be  read  without  removing 


19 

it  from  the  cylinder.    The  glass  was  protected  from  injnry  bj  brass 
rods. 

In  the  above  figure  cm  is  the  copper  cylinder,  he  the  two  valves, 
dd  the  handle  for  connection  to  the  sounding  line,  e  the  Six's  ther- 
mometer, ff^Q  weight  at  the  bottom. 


Table  Y. 


Air  Temperatures  between  Sierra  Leone  and  the  Flmida  Capes 


Temperature  of 

Air  at 

Temperature  of 

Air  at 

Date. 

Date. 

IMidnight. 

Noon. 

8  p.m. 

Midnig-ht. 

Noon. 

8  p.m. 

Feb.  21.... 

79° 

84° 

81° 

Mar.  14.  .  .  . 

78 

81° 

81° 

"  22.... 

79° 

84° 

83° 

"  15.... 

74° 

79° 

77° 

"  23.... 

80° 

83° 

79° 

"  16.... 

79° 

85° 

85° 

"  24.... 

78° 

81° 

79° 

"  24.... 

86° 

87° 

85° 

"  25.... 

78° 

84° 

80° 

"  25 

79° 

82° 

82° 

"  26.... 

77° 

82° 

76° 

"  26.... 

80° 

86° 

84° 

"  27.... 

74° 

82° 

77° 

"  27. . . . 

81° 

86° 

83° 

"  28.... 

74° 

78° 

79° 

April  3.!!! 

82° 

84° 

84° 

Mar.  1.... 

75° 

80° 

78° 

"  4.... 

80° 

83° 

82° 

"  2.... 

73° 

80° 

78° 

"  5.... 

80°  ■ 

81° 

83° 

"  3.... 

74° 

80° 

76° 

"  6.... 

81° 

84° 

87° 

"  4.... 

75° 

77° 

77° 

"  7.... 

84° 

84° 

81° 

"  5.... 

74° 

80° 

76° 

"  8.... 

82° 

82° 

86° 

"  6  ... 

74° 

79° 

76° 

"  9.... 

83° 

84° 

88° 

"  7.... 

74° 

79° 

79° 

"  10.... 

84° 

84° 

80° 

"  8.... 

73° 

78° 

77° 

"  11.... 

82° 

84° 

82° 

"  9.... 

74° 

78° 

76° 

"  12.... 

82° 

85° 

84° 

"  10.... 

75° 

80° 

77° 

"  13.... 

80° 

84° 

84° 

"  11.... 

76° 

81° 

81° 

"  14.... 

80° 

86° 

78° 

"  12.... 

76° 

81° 

80° 

"  15.... 

80° 

86° 

78° 

"  13.... 

78° 

84° 

81° 

It  will  be  remarked  that  in  the  foregoing  table  the  temperatm^es  are 
given  for  midnight,  noon,  and  8  p.m.  But  as  the  soundings  were 
usually  taken  at  other  hours,  more  commonly  at  3  p.m.,  I  give  in  the 
following  table  the  temperatures  observed  at  those  hours,  both  at  the 
surface  and  at  the  depths  specified. 


20 


Table  YI. 

Temperature  of  the  Air,  of  the  Sea-surface,  and  of  the  water  at  various  deptlis. 


Date. 

Hour. 

Latitude 

Lon^- 
tude. 

Temperature  op 

Air. 

Water 
Sur- 
face. 

Water  at  various 
Depths. 

Feb. 

u 

23 

25 

2  P.M. 

3  P.M. 
3  P.M. 
3  P.M. 
3  P.M. 

8°  50' 
9°  15' 
10°  05' 
10°  42' 
11°  24' 
11°  26' 
11°  39' 
11°  35' 
11°  06' 
11°  32' 
12°  38' 
13°  03' 
13°  06' 
13°  08' 
12°  55' 
17°  13' 
17°  13' 
17°  08' 
17°  09' 
17°  09' 
17°  27' 
17°  27' 
18°  11' 
19°  12, 
20°  48' 
23°  19' 
23°  19' 

15°  47' 

17°  12' 
17°  35' 
17°  46' 
18°  09' 
18°  20' 
18°  33' 
19°  33' 
21°  55' 
29°  13' 
42°  31' 
44°  51' 
50°  38' 
53°  48' 
56°  46' 
67°  29' 
67°  29' 
68°  48' 
71°  47' 
71°  47' 
74°  33' 
74°  33' 
76° 

77°  54' 
83°  01' 
84°  17' 
84°  17' 

79° 

78° 
76° 
78° 
77° 
80° 
82° 
77° 
76° 
76° 
83° 
84° 
80° 
80° 
81° 
80° 
80° 
84° 
82° 
82° 
82° 
82° 
85° 
84° 
84° 
84° 
84° 

78° 
79° 
74° 
77° 
76° 
77° 
77° 
76° 
77° 
75° 
76° 
76° 
75° 
79° 
80° 
84° 
84° 
84° 
84° 
84° 
84° 
84° 
85° 
85° 
85° 
86° 
86° 

200  fath. 
200  fath. 
200  fath. 
200  fath. 
200  fath. 
200  fath. 
200  fath. 
200  fath. 
200  fath. 

'266 'fath.' 
200  fath. 
200  fath. 
400  fath. 
100  fath. 
100  fath. 
400  fath. 
200  fath. 
200  fath. 
500  fath. 
300  fath. 
400  fath. 
200  fath. 
200  fath. 
200  fath. 
100  fath. 
200  fath. 

54° 

58° 

u 

26   

60° 

u 

27 , 

28  

60° 
53° 

March 

1 

53° 

2 

53° 

(( 

3   

3  P.M. 
3  P.M. 
3  P.M. 
2  P.M. 
2  P.M. 
11  A.M. 
2  P.M. 
2  P.M. 

53° 

K 

4  

52° 

U 

6 

10 

"56°* 

u 

11      

51° 

(( 
u 

13 

14   

51° 

47° 

u 

15  

62° 

April 

4 

70° 

4 

3  P.M. 
3  P.M. 

48° 

(( 

5 

59° 

u 

6   

62° 

u 

6   

4  P.M. 

48° 

u 

7  

54° 

7 

8 

4  P.M. 

3  P.M. 
4i  P.M. 

4  P.M. 

50° 
62° 

(( 

9   

62° 

(( 

11  

62° 

u 

13  

72° 

(( 

13 

5  P.M. 

62° 

For  a  proper  appreciation  of  the  conclusions  to  be  drawn  from  these 
tables,  it  is  necessary  to  point  out  the  facts  indicated  by  the  soundings 
of  the  ship.  For  the  sake  of  brevity  I  restrict  these  remarks  to  the 
second  stage  of  the  voyage. 


Parting  from  the  African  coast, 
the  bed  of  the  ocean  sinks  very 
rapidly.  A  couple  of  degrees  west 
of  the  longitude  of  Cape  Yerde  the 
soundings  are  2,900  fathoms.  From 
that  point  the  mean  depth  across 
the  ocean  may  be  estimated  at  about 
2,400  fathoms,  but  from  this  there 
are  two  striking  departures — first  a 
depression,  the  depth  of  which  is 
3,100  fathoms,  and  second  an  eleva- 
tion, at  which  the  soundings  are  only 
1,900 — the  general  result  of  this 
being  a  wide  and  deep  trough  on 
the  African  side,  and  a  narrower 
and  shallower  trough  on  the  Amer- 
ican. It  may  be  that  this  peculiar- 
ity is  a  result  of  the  river  distribu- 
tion on  the  two  continents  respect- 
ively, there  being,  with  the  excep- 
tion of  the  Senegal  and  Gambia,  no 
important  streams  on  the  African 
side,  whilst  on  the  American  there 
are  many,  and  among  them,  preem- 
inently, the  Orinoco  and  the  Ama- 
zon, these  vast  rivers  carrying  their 
detritus  far  out  to  sea,  and  helping 
to  produce  the  configuration  of  the 
ocean-bottom  in  question.  How- 
ever this  may  be,  it  is  doubtless 
through  these  deep  troughs  that 
much  of  the  cold  water  of  the  ]S"orth 
Polar  current  finds  its  way. 

In  accordance  with  this,  we  per- 
ceive, on  examining  the  tempera- 
ture of  the  water,  after  the  African 
verge  of  the  greater  or  eastern  sea 
trough  is  reached,  that  there  is  a 
difference  in  temperature  between 
the  surface  and  that  at  a  depth  of 


22 


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23 

not  more  than  two  liundrecl  fathoms,  exceednig  twenty-five  degrees 
in  many  cases.  This  decline  of  temperature  inci'eases  as  the  depth 
increases,  one  observation  giving  an  additional  fall  of  four  de- 
grees at  an  additional  depth  of  200  fathoms.  It  is  not,  however,  in- 
tended to  affirm  that  the  mass  of  cold  water  is  restricted  to  these  deep 
troughs,  since  even  in  the  West  India  seas,  at  similar  depths,  low  tem- 
peratures are  observed,  and  this,  though  the  heat  of  the  surface-water 
has  become  very  much  higher.  In  those  seas,  while  the  surface  tempe- 
rature was  84°,  the  thermometer,  at  depths  of  400  and  500  fathoms, 
marked  48°,  and  these,  it  must  be  remembered,  were  the  indications  of 
an  uncompensated  insfruraeut,  which  was  bearing  a  pressure  of  at  least 
half  a  ton  on  each  square  inch  of  its  surface,  and  hence  registering 
deo^rees  that  were  hi^'her  than  the  truth.  This  accords  with  the  ob- 
servation  of  Mr.  Barrett,  that  in  the  deepest  part  of  the  sea,  near 
Jamaica,  there  exists  a  temperature  not  far  above  that  of  the  freezing 
point  of  fresh  water. 

The  foregoing  diagram  represents  the  temperatures  of  the  air,  those 
of  the  surface  of  the  water  and  at  different  depths,  usually,  however,  at 
200  fathoms,  from  Sierra  Leone  to  Barbadoes,  and  from  Barbadoes  to 
Havana.  The  solid  line  represents  the  temperatures  of  the  air,  the 
dotted  line  that  of  the  surface  of  the  water,  the  broken  line  that  of  the 
water  at  200  fathoms  Here  and  there,  as  will  be  easily  recognized, 
isolated  observations  at  100,  300,  400,  and  500  fathoms  have  been  in- 
troduced. The  vertical  lines  indicate  longitudes,  the  degrees  of  tem- 
perature are  seen  at  the  side. 

This  diagram  shows  that  the  air  line,  after  its  oscillations  near  the 
African  coast  are  over,  exhibits  a  general  rise  to  Barbadoes  and  thence 
to  Havana.  There  is,  however,  a  marked  departure  from  the  gradual 
character  of  this  rise  at  a  distance  of  about  two-thirds  of  the  way 
across.  The  surface  temperatures  are  for  the  most  part  lower  than  the 
air  temperatures,  until  the  West  India  seas  are  reached,  when  they 
become  higher.  They  do  not  exhibit  that  sudden  rise  observed  in  the 
air  temperatures  at  45°  west  longitude.  The  line  of  deep-water  tem- 
peratures is,  of  course,  lower  than  that  of  the  surface  all  the  way  across, 
and  exhibits  the  same  contour  in  a  general  manner  as  the  surface-line, 
rising  as  it  comes  into  the  Caribbean  Sea. 


24 

From  Table  TV.  it  appears  that  the  specific  gravit}-  of  the  water  be- 
comes greater  as  the  location  is  further  west.  This  conclusion  I  found 
to  be  confirmed  by  an  examination  of  the  solid  residue  left  after  evap- 
oration to  dryness  of  different  samples.  I  need  not  quote  many  of 
these  confirmatory  experiments.  It  will  be  understood  that  the  cus- 
tomary care  was  taken  in  ascertaining  the  weight  of  these  solid  residues 
to  avoid  hygrometric  complication  and  the  escape  of  their  more  volatile 
ingredients.  As  an  example,  it  may  be  mentioned  that  surface  water 
taken  near  the  African  coast  on  March  1,  gave  39.600  grammes  of 
solid  residue  in  1,000  grammes  of  water,  and  another  sample  of 
surface-water  taken  on  April  10,  in  the  Caribbean  Sea,  gave  40.520 
grammes  in  1,000  grammes.  It  is  probable  that  the  concentration 
here  remarked  was  due  to  the  drying  effect  of  the  north-east  trade 
wind. 

The  specific  gravity  of  the  surface-water  is  of  course  affected  by  the 
rate  at  which  evaporation  is  taking  place,  a  concentration  ensuing  as 
evaporation  goes  on,  and  the  density  becoming  greater.  There  is, 
therefore,  a  tendency  in  such  concentrated  waters  to  leave  the  surface 
and  pass  downward,  until  they  reach  a  region  in  wdiich  the  density  cor- 
responds to  their  own.  These  considerations  have  led  some  persons  to 
suppose  that  this  descent  w^ould  be  continued  to  very  great  depths,  and 
that  this  movement  must  sensibly  affect  the  general  motion  taking  place 
in  the  w^aters  of  the  sea.  If,  however,  we  compare  the  density  of  the 
surface-waters  in  the  tropical  Atlantic  as  I  have  represented  them  in 
the  foregoing  tables,  with  the  density  of  surface-water  in  higher  lati- 
tudes, where  both  the  air  and  water  are  much  colder,  and  wdiere  evapo- 
ration is  much  less  active,  as  shown,  for  instance,  in  latitudes  between 
50°  and  60°  north  in  the  cruises  of  Dr.  Carpenter,  we  see  how  small 
the  difference  is.  When  w^e  remember,  also,  how  slight  a  variation  of 
temperature,  as  has  been  already  said,  completely  masks  these  differen- 
ces arising  from  concenti-ation,  we  may  safely  conclude  that  the  cause 
of  disturbance  may  be  overlooked. 


25 


In  the  adjoining  diagram  the  ver- 
tical lines  represent  longitudes,  the 
horizontal  lines  speciiic  gravities,  the 
solid  line  specific  gravities  of  the 
surf  ace- water,  the  dotted  specific 
gravity  of  water  at  two  hundred 
fathoms.  On  comparing  the  two 
latter  lines  together,  we  see  that  they 
almost  coincide  ;  and  again,  on  com- 
paring this  diagram  with  that  of 
the  temperatures  and  also  with  the 
cross  section  of  the  Atlantic  basin, 
a  curious  resemblance  will  be  readily 
detected,  viz.,  that  they  all  exhibit 
an  elevation  about  the  meridian  of 
45°  west  longitude,  as  though  the 
contour  of  the  bottom  was  not  with- 
out influence  on  the  physical  state 
of  the  water  above  it. 

The  general  conclusion  which 
may  be  drawn  from  these  results  as 
to  temperatures  and  specific  gravities 
is,  that  there  exists  all  over  the  bot- 
om  of  the  tropical  Atlantic  and  Car- 
ibbean Sea  a  stratum  of  cold  water, 
— cold,  since  its  temperature  is  be- 
low 50°.  This  is  the  conclusion  to 
which  Dr.  Carpenter  has  come,  as 
respects  the  Atlantic  in  higher  north 
latitudes ;  and  in  this  important  par- 
ticular the  cruise  of  the  Mercury 
must  be  considered  as  offering  con- 
firmatory proofs  of  the  correctness 
of  the  deductions  drawn  from  the 
cruises  of  the  Lightning  and  Por- 
cupine. 

There  are  reasons  for  supposing 
that,  so  far  from  this  water  being 


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26 

stagnant,  its  whole  mass  lias  a  motion  toward  tlie  Equator,  wliilst  the 
surface-waters  in  their  turn  have  a  general  movement  in  the  opposite 
direction. 

As  the  samples  of  water  had  already  been  kept  for  some  months 
before  they  came  into  my  possession,  though  the}^  had  been  confined,  as 
has  been  said,  in  bottles  closed  by  corks  covered  w^ith  sealing-wax, 
their  gaseous  ingredients  must  have  undergone  much  change,  I  have 
already  pointed  out  the  disturbance  that  necessarily  ensues  in  these 
gaseous  ingredients  as  they  are  being  draw^n  to  the  surface,  and  another 
disturbance  occurs  when  they  are  brought  more  fully  in  contact  with 
the  air  on  being  poured  into  the  bottles.  Interchange  by  diffusion  then 
rapidly  takes  place,  tending  to  make  their  proportions  approach  those 
of  surface-water.  For  these  reasons  I  did  not  consider  it  necessary  to 
make  an  analj^sis  of  the  gases  afforded  by  these  specimens.  Dr.  Car- 
penter, from  his  experiments,  concluded  that  when  freshly-drawn  water 
is  tested,  the  proportion  of  carbonic  acid  increases  as  the  stratum  of 
water  is  from  deeper  sources. 

I  made  some  examinations  of  the  organic  matter  contained  in  these 
waters,  both  by  incinerating  the  solid  residue  and  by  the  permanganate 
test.  It  has  been  customary  to  divide  such  organic  ingredients  into  two 
groups,  the  decomposed  and  decomposable,  in  investigations  respecting 
the  sustenance  of  animal  life  at  great  ocean  depths.  To  estimate  the 
relative  proportion  of  these  groups,  a  sample  of  the  water  is  divided 
into  two  parts — one  is  acidified,  and  then  to  both  an  excess  of  a  standard 
solution  of  permanganate  of  potassa  is  added.  After  three  hours, 
iodide  of  potassium  and  starch  are  introduced  to  check  further  reac- 
tion, and  the  excess  of  permanganate  in  each  sample  is  then  estimated 
by  a  standard  solution  of  hyposulphite  of  soda.  From  the  portion  to 
which  free  acid  was  added  the  decomposed  and  easily-decomposable 
organic  matter  can  be  estimated,  and  from  the  other  the  decomposed 
alone.  I  resorted  to  this  method  of  examination  in  several  instances, 
but  was  discouraged  from  prosecuting  it,  for  such  reasons  as  have 
already  been  stated  in  the  foregoing  case  of  the  gaseous  constituents. 
It  needed  no  special  j)roof  that  organic  matter  was  present  in  every  one 
of  these  samples,  for  the  clearest  of  them  contained  shreddy  and  floccu- 
lent  material,  some  of  them  quantities  of  sea-weed  in  various  stages  of 


decomposition.  With  these  vegetable  substances  were  the  remains  of 
minute  marine  animals.  As  bearing  upon  this  subject,  I  found,  on 
incinerating  the  solid  residue  of  a  sample  of  water  taken  from  two  hun- 
dred fathoms,  that  the  organic  and  volatile  material  was  not  less  than 
eleven  per  cent,  of  the  whole.  Though  the  quantity  of  organic  substance 
diminished  as  the  stratum  under  examination  was  deeper,  there  still  re- 
mained a  visible  amount  in  the  water  of  four  hundred  or  five  hundred 
fathoms.  It  is  probable,  therefore,  that  even  at  the  bottom  of  the  ocean 
such  organic  substance  may  exist,  not  only  in  solution  affording  nutri- 
ment to  animals  inhabiting  those  dark  abysses,  as  Professor  Wyville 
Thompson  has  suggested,  but  also  in  the  solid  state.  Plants  of  course 
cannot  grow  there,  on  account  of  the  absence  of  light. 

In  order  to  determine  whether  any  hitherto-unknown  element  existed 
in  these  w^aters,  I  subjected  the  solid  residue  to  examination  with  the 
spectroscope,  volatilizing  the  substances  by  the  aid  of  a  voltaic  current 
and  induction  coil.  A  careful  examination  did  not  reveal  the  presence 
of  any  spectral  lines,  other  than  those  belonging  to  the  well-knowu 
elementary  substances  in  sea-water. 

The  specimens  of  the  bottom,  obtained  by  attaching  to  the  sounding- 
line  quills  or  wooden  tubes,  I  have  transmitted  to  Dr.  Carpenter,  who 
has  kindly  consented  to  'examine  them. 

In  a  letter  dated  August  10, 1871,  recently  received,  he  says  :  "As  far 
as  I  can  see,  they  consistof  the  ordinary  Atlantic  mud,  chalk  in  process 
of  formation,  with  the  ordinary  types  of  deep-sea  foraminifera."  The 
chemical  composition  of  this  mud,  according  to  Mr.  Forbes,  as  taken 
from  soundings  at  1,443  fathoms  in  the  North  Atlantic,  is : 

Carbonate  of  lime 50.12 

Alumina  (soluble  in  acids) 1.33 

Sesquioxide  of  iron  (soluble  in  acids) 2.17 

Silica  (in  a  soluble  condition) 5.04 

Fine  insoluble  gritty  sand  (rock  debris) 26.77 

Water ' .  2.90 

Organic  matter 4. 19 

Chloride  of  sodium  and  other  soluble  salts 7.48 

100.00 
All  of  which  is  respectfully  submitted.  »=___ 

HENRY  DRAPER,  M.D. 


28 

SCITOOL-SHIP    MeRCUEY,         ) 

New  York,  April  29,  1871.  j 
Sir — I  would  respectfully  submit  to  your  Honorable  Board  the  fol- 
lowing report  of  all  reliable  deep-sea  soundings  made  from  this  ship 
during  her  late  practice  cruise,  together  with  a  description  of  the  man- 
ner in  which  they  were  made.  The  soundings  were  taken  within  the 
parallels  of  eleven  and  thirteen  north  latitude,  from  the  coast  of 
Africa,  in  the  vicinity  of  Sierra  Leone,  to  the  Island  of  Barbadoes, 
W.  I.,  through  the  Caribbean  Sea  to  the  west  end  of  Cuba.  The 
instrument  used  was  a  detaching  apparatus,  invented  by  the  late  Lieur 
tenant  J.  M.  Brooke,  U.  S.  ]^.,  and  supplied  to  this  ship  through  the 
kindness  of  Commodore  James  Alden,  Chief  of  the  Bureau  of  Navi- 
gation, Navy  Department,  AVashington.  I  found  it  worked  admirably, 
never  failing  to  bring  up  specimens  of  the  bottom,  except  when  coming 
in  contact  with  rocky  bottom.  The  quills  inserted  in  the  cell  or  holder, 
as  seen  in  the  accompanying  sketch  of  the  apparatus,  preserve  tha 
specimens  in  better  condition  for  microscopic  examination  than  the 
ordinary  "  arming"  of  soap  or  tall(~>w  would  bring  up. 

Two  spherical  shot,  weighing  thirty-two  pounds  each,  were  used  at 
every  cast  as  a  sinker,  the  sounding-line  made  of  cotton,  one-seventh  of 
an  inch  in  diameter,  capable  of  sustaining  one  hundred  and  sixty 
poimds  in  the  air ;  the  cord  carefully  waxed  to  overcome,  as  much  as 
possible,  the  resistance  of  the  line  from  friction  of  the  water.  x\ll 
soundings  were  made  from  a  boat,  as  repeated  trials  satisfied  me  that 
no  reliance  could  be  placed  on  those  made  from  the  ship,  on  account  of 
the  difficulty  of  keeping  the  vessel  in  position  and  the  line  "  up  and 
down."  A  boat,  fitted  expressly  for  the  purpose,  with  a  reel  holding 
four  thousand  fathoms,  working  on  friction  rollers,  the  line  passing 
over  the  bow  through  a  leader,  thus  enabling  the  boat,  with  the  aid  of 
oars,  to  be  kept  in  position  and  the  line  perpendicular  on  the  shot,  thus 
determining  to  a  certainty  when  the  sinker  reached  the  bottom. 

Temperature  and  specimens  of  sea-water  at  various  depths  were 
obtained  by  a  self -registering  metallic  thermometer  carefully  adjusted  ; 
all  specimens  secured  have  been  carefully  preserved,  and  now  await 
your  order.  All  soundings  were  made  under  my  immediate  super- 
vision, and  the  position  of  the  ship  at  the  time  of  sounding  carefully 
noted,  for  which  I  respectfully  refer  you  to  the  accompanying  table. 
Yery  respectfully,  your  obedient  servant, 

P.  GIRAUD,  Captain. 
Isaac  Bell,  Esq.,  President,  etc. 


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From  Hart's  Island, 

Rough  sea,  ship  rolling  heavily. 

Rough  sea,  ship  rolling  heavily. 

Fresh  gale,  high  sea. 

Heavy    gale,    accompanied    by    fnrious 

squalls. 
Light  breeze,  confused  sea,  sky  overcast. 
M(jderate    breeze   and  pleasant  weather 

throughout. 
Current  ENE  twelve  miles,  sky  overcast. 
Moderate  breeze  and  pleasant. 
Moderate   breeze   and   pleasant,    passing 

clouds. 
Moderate  breeze  and  fine  weather. 
Fine  weather,  light  passing  clouds. 
Light  airs,  accompanied  by  squalls. 
Clear  and  pleasant. 
Fine  weather. 

Moderate  breeze  and  cloudy. 
Fresh  breeze  and  squally,  sea  rough. 
Moderate  breeze,  heavy  passing  clouds. 
Moderate  breeze  and  cloudy,  sea  rough. 
Moderate  breeze  and  fine  weather. 
Light  and  baffling,  cloudy. 
Fine  weather. 
Sky  overcast,  sea  smooth. 
Fresh  breeze  and  squally. 
Fresh  breeze,  passing  clouds,  rough  sea, 

SSE  current  one  knot  per  hour. 
Heavy  passing    squalls,   squally,   rolUng 

swell  NW. 
First    part    fine    weather,    second    part 

squally  and  rainy. 
At  9  A.M.  anchored  at  Funchal,  Madeira, 

lat.  32°  38',  long.  16°  55'. 

•spuTAV 

WNW  to  SW 

NW  to  NNE 

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50°  37' 

51°  .5.5' 
49°  50' 

46°  05' 
45°  08' 
42°  15' 

38°  02' 
30°  15' 
34°  54' 
31°  30' 
30°  47' 
30°  .35' 
31°  05' 
31°  02' 
30°  18' 
29°  10' 
28°  50' 
28°  .33' 
27°  20' 
25°  30' 
22°  20' 

19°  50' 

17°  20' 

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