6 
B.  Helland-Hansen. 
[No.  15 
The  chief  reason  why  the  grapnels  get  such  a firm  hold  on 
the  boat  after  the  cables  have  been  well  tautened  must  be  that 
the  friction  of  the  ropes  in  the  water  is  so  great  that  it  requires 
a stronger  force  than  the  boat  can  exert  to  tanten  the  rope,  even 
though  the  wind  is  pressing  upon  her.  The  hemp  line  we  use  is 
aboiit  3 V2  centimeters  in  circumference ; the  grapnels  weigh  about 
20  kilos  each. 
The  plan  that  we  adopted  with  the  boat  was  as  follows:— the 
first  grapnel  was  let  go  from  the  boat  itself,  which  was  then  towed 
by  the  steamer  in  the  direction  of  the  current,  until  the  cable  be- 
came  thoroughly  taut.  The  steamer  then  went  on  with  the  second 
grapnel,  and  it  was  let  go  after  sufficient  line  had  been  paid  out. 
As  a general  rule  it  raay  perhaps  be  said  that  the  length  of 
line  for  each  grapnel  should  be  double  the  depth  from  the  surface 
of  the  water  to  the  bottom.  When  the  grapnels  are  well  home,  the 
cables  are  tautened  as  much  as  possible  by  two  men:  and  after  a 
few  liours  it  will  generally  be  found  impossible  to  haul  in  a couple 
of  meters  on  either  of  them.  Even  after  a day  has  elapsed  they 
have  continued  exactly  in  their  original  position. 
A great  advantage  of  this  method  is  that  it  enables  us  to  use 
the  current-meter  from  the  boat  just  as  one  can  do  with  a water- 
bottle.  A number  of  observations  can  thus  be  made  within  the 
hour.  For  a five  minutes’  test  each  observation  doivn  to  a depth 
of  two  hundred  meters  or  so,  will  take  altogether  ten  minutes  or 
a little  more;  whereas  when  the  apparatus  is  buoyed  and  anchored, 
one  observation  an  hour  is  practically  all  that  can  be  made.^) 
The  strength  and  direction  of  currents  vary  to  such  an  exteut 
and  the  variations  are  often  so  irregular  that  one  is  compelled  as 
a result  to  take  frequent  m.easurements  at  the  different  depths. 
Koughly  about  one  observation  per  hour  for  each  depth  should  be 
recorded,  and  this  can  be  done  if  our  mode  of  procedure  is  adopted. 
While  engaged  in  taking  observations,  especially  in  the  fiords  iii 
the  neighbourhood  of  Bergen,  we  were  lately  using  two  instruments 
simultaneously,  one  of  which  was  constantly  at  work  at  a certain 
depth,  so  as  to  show  all  variations  there  with  the  greatest  pos- 
sible accuracy. 
See  Fridtjof  Nansen:  Methods  for  Measuring  Direction  and  Velocity  of 
Currents  in  tlie  Sea.  With  an  Appendix  by  Dr.  V.  Walerid  Ekman  (Publ.  de 
circ.  no.  34). 
