8 
B.  Helland-Hansen. 
[No.  15 
and  simple  transition  forms.  From  sucli  curves  the  velocity  and 
direction  has  been  worked  out  for  each  hour,  and  the  values  found 
by  means  of  this  graphical  interpolation  are  shown  as  progressive 
or  central  vector-diagrams  (see  figs  2 and  12  also  Plates  I and  II). 
The  progressive  vector-diagrams  show  the  displacement  of  the  particles 
of  water  and  depict  their  lines  of  flowage.  The  progressive  vector- 
diagrams  have  been  employed  to  fix  the  average  velocity  and  direc- 
tion of  the  resulting  curi-ents  during  the  course  of  one  or  two  tidal 
periods  (figs  3,  4,  7 and  13). 
In  the  short  narration  which  we  shall  give  in  the  following 
pages  it  must  be  borne  in  mind  that  we  are  confining  ourselves  to 
a description  of  the  conditions  as  we  found  them  at  the  particular 
time  when  we  were  engaged  in  our  researches  in  the  various  localities. 
It  is  too  early  yet  to  draw  general  conclusions  from  these  observations, 
unless  perhaps  where  they  can  be  otherwise  verified.  However  the 
measurements  present  general  problems  of  considerable  importance, 
even  though  the  solution  cannot  yet  be  quite  satisfactorily  given. 
