CURRENT AND DRIFT OF THE SHIP 



127 



SOUTTHERLY DRIFT 



Fig. 8. Drift of the ship in a north and south direction, from noon on June 4 to noon on June 6, illustrated 

 diagrammatically from right to left. The data are given in Tables I and Appendix IV. The northerly drift 

 from noon on June 4 to 0507 on June 5 includes the time spent on St. WS 612, and the passage to within 8 

 miles of land (see Fig. 5); the subsequent drift, alternately south and north, took place while Sts. WS 613-620 

 were being worked. Four-hourly records of wind are given in the centre of the diagram, while below is 

 appended the distance from land at which each of the observations was made. 



might be regarded as evidence of northerly current we beHeve the data too few for 

 definite information. 



On the journey out from Antofagasta the wind blew at first east, and then un- 

 remittingly from the south with force 4, which increased to 5 from south-south-west 

 in the open sea; during some 36 hours from Sts. WS 622-630, the ship drifted 11 miles 

 to the northward, i.e. a mean drift of 8 miles a day. According to the track chart, 

 however, the greater part of the drift occurred within the coastal 15 miles, and as in 

 addition the drift had an appreciable westerly component, the mean rate exceeded 

 12 miles a day. Since the greater drift accompanied the lesser wind, some may be 

 ascribed to currents. 



The return journey commenced with moderation from force 5 to 2 in the southerly 

 wind which later changed direction to the north ; in spite of this the ship was carried in 

 a north-easterly direction as may be inferred from the positions at the beginning and end 

 of St. WS 630, during which the ship was drifting for 12 hours (Fig. 9 and see p. 145). 

 A heavy counter-current was met inshore off Bahia Herradura. 



On a later page, the surface drift off Antofagasta will be related to changes of surface 

 temperature : it is therefore of particular interest that the positions of stations in this 

 locality (Fig. 9) have been fixed with exceptional accuracy: those of the first seven 

 (Sts. WS 622 628) and the last six (Sts. WS 630-635) by cross-bearings on land and 

 that of St. WS 629 by observations on a sunny day; the ship's track is in consequence 

 a faithful record of her drift, but of the relative velocity of this drift on different points 

 of this line, it is misleading because there is no indication of the time spent on any 

 one part of the line. 



Winds inshore off Arica amounted to light airs, yet a north-westerly drift of 48 

 miles a day was noted, which must be due to inshore current (Fig. 11). 



The amount of drift and set experienced at various points along the San Juan line 

 of stations is of interest (Fig. 11). A strong wind from the south-east blew for almost 

 the whole period. Close to the shore its force attained 6-7 and drifted the ship to 



