TEMPERATURE i53 



from shore: here the i8° C. isotherm was 12 miles closer to land on the return outward 

 than on the shoreward run: and at 50 miles the 20° C. isotherm had shifted shorewards 

 about 9 miles. There seems to be no reason for thinking that this apparent change in 

 the position of surface isotherms is due to an error in the ship's position and the 

 synchronous change in wind suggests as more likely that the latter is related to the 

 former as cause and effect (cf. conditions at Antofagasta). The question whether the 

 section in Fig. 38 represents a process of subsidence after upwelling rather than a 

 state of incipient active upwelling, is examined on pp. 208-9 and 213. 



Since the ship was prevented from taking observations at less than 7 miles from the shore by the 

 position of the Guanape Islands, three additional stations were worked in Salaverry Roads for 

 the purpose of examining inshore conditions. Here a temperature of 16° C. was recorded at 5 miles 

 from the shore (Appendix IV), and since it was recorded very soon after the change of wind from 

 east to south-west, it may be conjectured that this is a legacy of the former strong wind rather 

 than a consequence of the weaker. 



Table IV. C/wfige in position of surface isotherms off the GuaHape Islands 



With a change of wind from east to west the isotherms of 17, 18, 19 and 20° C. shifted towards the 

 shore. 



The lines off the Lobos Islands and off Punta Aguja, situated comparatively close to 

 one another, are similar in plan, illustrating the progressive widening of the Peru Coastal 

 Current and the progressive homogeneity of the upper layers. 



The better part of a week elapsed between completion of the Guaiiape Islands and 

 commencement of the Lobos Islands line, the work being interrupted by a visit to 

 Callao. The dangers of heavy drift around the rocky isles Lobos de Tierra and Lobos de 

 Afuera precluded the usual course of letting the ship drift before wind and current : 

 also an endeavour was made to examine the effects of these rocks upon the hydrological 

 conditions. Accordingly courses were shaped, first to take observations off the exposed 

 (south and south-east) aspects of the Lobos de Afuera, and then to place stations along 

 a line midway between the latter and the Lobos de Tierra. 



Compared with other lines, upwelling off the Lobos Islands seems in abeyance and 

 the surface layer is comparatively warm, a value of 17-38° C. being the warmest inshore 

 temperature met. This layer is also seen in Fig. 47 to be more saline than the sur- 

 rounding water. Such a distribution of warm saline water leading to a slackening of 



