598 A NATURALIST IN THE PACIFIC 



instance the plane of 60. Whilst south of Ancon (lat. n 45' S.) it was 

 rarely deeper than four fathoms, north of this latitude it descends rapidly, 

 being probably about ten fathoms down at Salaverri and Eten and 

 about twenty fathoms deep at Payta, in latitude 5 S., where the Humboldt 

 Current leaves the coast. Within the Gulf of Guayaquil it is probable 

 that the plane of 60 would descend to nearer thirty fathoms, the region 

 being outside the influence of the current. 



Some interesting facts are also elicited from the variation of the surface- 

 temperatures. When we were coasting along at a distance of five or six 

 miles from shore the readings were fairly constant from hour to hour 

 varying only a degree or so. But nearer the land, for instance, about two 

 or three miles away, the variation from hour to hour amounted to two or 

 three degrees, whilst within the limits of the anchorages, a mile and 

 less from the coast, the change from hour to hour amounted to three 

 or four degrees. Nor was there any uniformity at the same hour over the 

 surface of a roadstead. The temperature would often rise or fall a degree 

 every few boat-lengths. Sometimes the inshore water was the coolest and 

 sometimes it was the warmest. Thus at Iquique the inshore water was 

 three degrees warmer than the water half a mile out, whilst at Mollendo, 

 when the temperature one-third of a mile off the shore was 70, it was 63 

 close to the rocky coast. The same thing was exhibited at Pisagua, where 

 the surface-water two miles out at sea was 61, whilst close inshore at the 

 anchorage it was 58. It was evident that there was a considerable inter- 

 mingling of the warmer surface and the colder, deeper waters on the coasts 

 of Chile and Peru. This was particularly noticeable on a rocky, steep-to 

 coast, or where there was an uneven bottom. At some places, indeed, the 

 warm upper layer did not exist, the cold water welling up all along 

 the coast. This was especially the case between the 22nd and iQth 

 parallels of latitude, a tract of coast in which lie Tocopilla, Iquique, and 

 Pisagua, and probably the coolest part of the sea-border at this season of 

 .the year. 



During a fortnight spent at Ancon (11 45' S.), between January 27 and 

 February 10, I paid considerable attention to the local climatic conditions, 

 and especially to the temperature of the inshore water. The daily range of 

 the air-temperature was only five or six degrees, the average minimum and 

 maximum being 71 and 75*9, and the mean for the period 73*5. The 

 mean temperature of the surface-water at the head of the pier, from 

 observations taken at about 7 a.m. and 4 p.m., was 68'6, or five degrees 

 cooler than the air, the mean temperature in the morning being 69*1 and 

 in the afternoon 68. 



The Ancon climate at this period is full of oddities and abnormalities, 

 and in this way typifies much of the coast of Peru. Thus, since the heat 

 of the day is tempered by the cool south-westerly winds which die away in 

 the evening and give place usually to warm, light, northerly and north- 

 westerly breezes, there is, as above remarked, but a small difference between 



