20 
B.  Helland-Hansen. 
[No.  15 
Fig.  7.  Eesulting  cuiTents.  Lingbank  (St.  312). 
wliole  mass  of  water  only  amouuted  to  3 — 4V2  cm.  per  second 
(about  2 nautical  miles  in  24  hours,  or  1 nautical  mile  during  the 
tidal  period).  The  same  is  indicated  by  the  central  vector-diagrams 
in  the  lower  series  on  Plate  II,  and  in  figure  5 by  the  differences 
in  the  maxima  of  velocity. 
From  the  detailed  records  we  can  see,  that  the  single  dmections 
during  the  measurements  at  Ling  Bank  varied  a good  deal.  The 
sea  became  so  disturbed,  that  further  work  had  to  be  given  up, 
and  this  may  partially  account  for  the  spreading  of  the  shot  in  the 
apparatus.  The  mean  directions  however  seem  to  be  all  right.  It 
is  thus  quite  evident,  that  if  we  had  made  only  one  observation  of 
the  direction  in  each  case,  we  would  have  obtained  a more  unreli- 
able  picture,  and  would  in  all  probability  have  failed  to  trace  some 
of  the  results.  By  means  of  several  determinations  of  the  direction 
the  errors  caused  by  the  rolling  of  the  boat  are  obviously  very 
much  reduced  and  may  generally  be  neglected. 
