CURRENT AND DRIFT OF THE SHIP 131 



When shaping courses to take observations midway between the Lobos de Afuera 

 and the Lobos de Tierra, allowance was made as far as possible for the effects of drift 

 and set which were pronounced on all parts of the line (Fig. 12). At 1 16 miles offshore 

 the drift of 30 miles a day was almost due westerly (264°) : at 78 miles offshore 36 miles 

 a day south-westerly (213°): to the westwards of the Lobos de Afuera (45 miles from 

 the mainland) the drift was north-easterly (032°) with a velocity of 24 miles a day, and 

 between the two archipelagoes and at distances of less than 20 miles from the mainland 

 the drift was north-westerly with a velocity of 36 miles a day. The winds during this 

 time were on the whole light, and drift, at any rate inshore, must be ascribed very 

 largely to surface currents. This accords with the traditional records of current off this 

 stretch of the coast (p. 190). 



A considerable current affected the ship within 33 miles of Punta Aguja. The total 

 drift northwards was 18 miles in 12 hours. In a slightly stronger wind off Pichidanque 

 Bay where there was no current the ship had drifted at 20 miles a day. Allowance for 

 wind off Punta Aguja would thus leave a clear balance of 16 miles a day which can 

 be attributed to the northerly current. Between 100 and 171 miles offshore a south- 

 westerly current appears to have drifted the ship at 14 miles a day against a wind 

 force 1-2 from south-east and south-south-west. 



The currents off Capo Blanco were complicated by the intrusion along the coast 

 of hot water of low salinity southwards from the Gulf of Guayaquil and the coast of 

 Ecuador. Local currents were very strong: while the ship was working a station 

 in the hot water inshore a south wind blew with a force of 5-6 strong enough to give 

 her a northward leeway drift of some 18 miles a day. But against the wind a surface 

 current raced southwards at an estimated 48-96 miles a day, and overcoming the effect 

 of the strong wind, carried the ship southwards at 41 miles a day. Farther from the 

 shore the current weakened (Fig. 70). 



Off the Gulf of Guayaquil itself three records indicate that surface movement is 

 considerable (see Table I): but within 50 miles of Santa Elena none was recorded. 



These data suggest that the ship's drift has been caused to a great extent by wind. 

 Estimations of northerly drift resulting from the action of current alone indicate that 

 it had a velocity of 16 miles a day off Punta Aguja and of 48 miles a day off Arica; 

 considerable current was noted off the Lobos Islands but less off the Guanape 

 Islands, Antofagasta and Caldera. Off Cape Carranza, Pichidanque Bay, Callao and 

 Santa Elena the ship's drift seemed to be entirely due to windage. Off Capo Blanco, 

 San Juan, northwards of Antofagasta and Caldera, southerly currents were also 

 recorded. 



Inferences of a general character may be made by averaging the drift at different 

 distances from the shore. The mean drift off Chile and Peru separately and off the west 

 coast as a whole is illustrated in Figs. 14 and 15 ; the first gives the mean gross drift in both 

 northerly and southerly directions ; the second gives the mean residual drift either north 

 or south after subtracting the lesser from the greater. A key showing the number of 

 observations averaged at different distances from the shore is given beside each graph. 



