112 DISCOVERY REPORTS 



in Europe, for the last four score years, it is incredible how very rarely any thing of this kind hath 

 been attended to. 



Humboldt's observations of 1802 indicated that the water was cooler than the air and 

 that the temperature rose rapidly with increasing distance from the shore. He thus 

 showed that the water must cool the air and not vice versa as Walter had suggested, and 

 in view of the northerly current and of the results obtained by Duperrey in ' La Coquille ' 

 he formulated the theory of a coastal current of Antarctic origin. Humboldt himself 

 publishes little upon these conclusions, but Berghaus, who had access to Humboldt's 

 manuscripts, expands his thesis and adds, as corroborative evidence, the observations 

 made at other times of the year by Holmfeldt, Meyen and Duperrey. 



At this time writers owed most of their knowledge to the French, who had equipped 

 three expeditions to collect scientific data. 'La Coquille' in 1823 under the command 

 of Duperrey, 'La Bonite' in 1836 and 'La Venus' in 1837-8, constitute important 

 attempts at collecting knowledge. In the published results of these and other works, 

 most authors adhere to Humboldt's view and Arago in 1840 added that the current 

 must have great depth (1780 m.), since if this cold water were to overlay warmer 

 water its greater density would cause it to sink. The ' Beagle ' visited the west coast in 

 1835, and although FitzRoy makes pertinent observations, neither he nor Darwin pays 

 much attention to ocean temperature. 



Bougainville (1837) is one of the earliest to level criticism at Humboldt's theory, 

 pointing out that in 1825 the surface temperatures olT Valparaiso were not much lower 

 than those found at Lima by Humboldt. In 1844 de Tessan takes the matter further, 

 arriving at the important conclusion that the low temperatures are the result of up- 

 welling of the lower layers. In 1844 too, Maury considered application of the Law of 

 Deviation to ocean currents, but this and upwelling do not seem to have been related 

 to one another as cause and effect until the publication of Witte's paper in 1880. 

 Dinklage in 1874 had nevertheless suggested that upwelling, together with a subsurface 

 current of compensation towards the coast, might result by aspiration from the wide- 

 spread westerly set caused by trade winds in the ocean at large. 



Since the opening of the twentieth century the question of the Peru Current 

 has been taken up afresh by writers with varying views. These are discussed on pp. 

 189-234, and it will suffice here to mention that as regards general principles the con- 

 clusions of Kriimmel, Schott, Sverdrup, Vallaux and Schweigger will probably meet 

 with general acceptance. Vallaux (1930) and Schott have examined the evidence 

 critically. Schott's work — the first two parts of which were published in Germany in 

 May 1 93 1, the very month in which the 'William Scoresby' began her investigations — 

 is the most complete account of the hydrology of this region that has yet appeared, and 

 it has put all future workers in his debt. The greater part of the paper is devoted to a 

 discussion of the intricate problems in the northern part of the area where the cooler 

 Peru Current converges with warmer equatorial water. Our knowledge of this interesting 

 region and of the Niiio Counter-current is drawn almost entirely from his work and 

 it is quoted frequently in the present report. For the more southerly parts of the 



