1907] 
Cui-rent-Measurements. 
15 
departure  along  the  mean  direction  of  the  current.  The  broken 
line  gives  the  averag-e  streng-th  of  the  movements  looked  at  apart 
from  the  chang-es  of  direction.  The  difference  between  the  two 
curves  is  g^reatest  in  the  upper  layers,  where  the  chang-es  of  direc- 
tion are  more  striking-  than  in  the  deeper  lying-  Atlantic  water. 
Plate  I shows  us  a remarkable  change  of  direction  immediately 
after  midday  on  the  12th  July.  The  curves  of  direction  in  the 
rectangular  co-ordinate  system  make  this  even  clearer.  The  veloci- 
ties  in  the  upper  layer  doAvn  to  about  30  meters  shoAved  a minimum 
at  that  time  of  the  day;  Avhile  there  Avas  a maximum  of  velocity 
at  about  midnight,  there  maxima  occurring  only  once  in  the  24  hours. 
In  1885,  AAdien  taking  measurements  of  the  Gulf  Stream  in  the 
Strait  of  Florida,  J.  E.  Pillsbuey^)  shoAved  us  that  it  has  a daily 
period  there  as  far  as  velocities  go.  Our  observations  seems  to 
show  that  the  same  is  the  case  AAith  the  Gulf  Stream  at  the  Edge. 
In  the  deeper  layers  (100 — 200  meters)  the  period  Avas  tAvice  as 
great,  and  about  24  hours  intervened  betAveen  maximum  and  minimum. 
Future  researches  Avill  have  to  make  it  clear  Avhether  these  conditions 
b United  States  Coast  and  Geodetic  Survey  1885,  Eeport  p.  500. 
