COUNCIL - MARCH 1920 - APPENDIX 



68 



At E 56, 33 readings were made at depths 10 and 65 metres and the cumula- 

 tive vectors based upon all the observations worked out at: — 



10 M — S. 87 E, 2.1. cm/sec; at 65 M — N 33 W, 3.2 cm/sec. 

 In order to compare with these results and also to bring the time factor more 

 definitely into regularity, similar resultants were prepared taking account only 

 of observations at hourly intervals. They gave — 



At 10 M — N 30 E, 1.6 cm/sec; at 65 M — N 18 W, 5.2 cm/sec. 



These variations are material, and in order to get a continuous series of 

 observations at smaller intervals than 1 hour, it was necessary to devise means 

 to interpolate vectors at times when no observation was taken. This was effected 

 by plotting separately on a time basis the abscissae and ordinates of all the actual 

 observation vectors, fitting curves to the two sets of points and reading off from 

 the curves the components of the new vectors. These are marked A in the diagrams 

 attached. By means of these curves, vectors at any given moment could be ob- 

 tained, and resultants were worked out from the vectors at 1/4 and ^/g hourly inter- 

 vals over periods of 12^/2 and 13 hours as far as the material allowed. They were: — 



At 10 metres. 'Starting at 5.45 



^2 hr. intervals covering 12^/2 hrs. N42E 



1.8 

 V4 - — — — N37E 



1.9 



— — 13 hrs. N73E 



1.7 



— — — N64E 



1.7 



V 



At 65 metres Starting at 6 6.15 6.30 6.46 



Vs hrs.intervals covering I2V2 hrs. N47W 5.1 N46W 4.5 N45W 4.6 N45W 4.2 



N46W 4.9 N46W 4.6 N45W 4.4 



N40W 4.4 N39W 4.2 N37W 4.3 



V4 



13 hrs. 



N39W 4.3 N38W 4.3 



These results differ materially from those previously found, and they show 

 considerable variations according to whether 12^/2 or 13 hours observations are 

 compounded. In addition when the duration of the period is uniform, but the 

 starting point is shifted, fairly material differences apparently in a definite direc- 

 tion are noticeable. This might have been due to faulty fitting of the curves at 

 the ends of the series, and in order to test this point, a series covering 24 hours, 

 taken at station H 2 off the Dutch coast, was chosen and resultant vectors were 

 prepared so that each was compounded for a period commencing ^/g hour later 

 than the previous one . The results so found varied as follows : — . 



