SEASONAL CHANGES 



169 



Santa Elena show the poorly saline water of the Equatorial Counter-current extending 

 to a depth of about 40 m. Beneath is a mid-water tongue of subtropical water which 

 may be traced southwards from Sts. WS 719-724, when it comes to the surface. 



SEASONAL CHANGES 



Opportunities of repeating work occurred twice: the line off Callao was repeated 

 after a period of seven weeks : and during this period a series of observations was carried 

 out at one position near Palominos Island. Repeated observations are useful as controls 

 by illustrating the kind of changes that occur over relatively short periods ; they may also 

 illustrate the changes due to season and they emphasize the limited usefulness of observa- 

 tions made at only one time of the year, and even more so of isolated observations. 



The repeated observations off the little island rock of Palominos were made on 

 position 12° 09' 30" S, 77° i5'oo"W in 60 m. of water; the results are plotted in 

 Fig. 51. The depths of certain isotherms at various dates are indicated by continuous 

 lines (the I5"5° C. isotherm by a thickened line). The oscillating nature of the tempera- 

 ture over the stated period is at once apparent. From June 26 until the middle of the 

 first week in July the temperature of the whole column of water rose, and at the surface 

 from 16-85 to i7'33 C. Then followed a sharp reaction, and during the subsequent 



STATION NUMBER5_WS72Z 

 MILES FROM COAST _ 



WS708 W57I4 WS7I3 WS7i2 

 io ' ' 25 ' 



I 



ws7ce 



W57IIWS7I0I 



I I 



400 

 SOUNDING IN METRES_ 



1885 



Fig. 50. Distribution of salinity. Section off Capo Blanco, July 24-26. The position of this section is shown 

 in Figs. 2 and 70; the corresponding temperature section, in Fig. 41. 



