Temperature of the Sea and the Air 115 



As the ship left the Channel in the middle of winter, and 

 proceeded nearly due south, the temperature of the water 

 rose rapidly at first. Observations were begun on January 21, 

 in lat. 34 N., and between this latitude and lat. 10 N. the 

 of rise was very steady, averaging 0-36 C. per degree 

 <>f latitude. From lat. 5 N. to 15 S. the temperature is vary 

 uniform and high, averaging 26-86 C. After passing lat. 15 S. 

 temperature falls, and begins to show greater variations, 

 he shallow water on the Abrolhos Bank is approached. 

 The average temperature of the water over this bank was 

 ')C. After passing Cape Frio, and between the parallels 

 S D and 30 of south latitude, the variations of temperatun 

 considerable and often abrupt; the maximum observed 

 in this part was 26-7 C., and the minimum 24-3 C. As the 

 higher temperature generally accompanies a greater salinity, 

 probable that these variations are due, not to any terres- 

 trial source, such as large rivers, but to an oceanic cause, the 

 ne and colder water of the deeper ocean strata being 

 thrown up against the coast, and mixing imperfectly with the 

 hot and dense surface water. In lat. 30 S. the influence of 

 River Plate makes itself distinctly felt by a general rapid 

 fall of temperature. As the ship got into soundings, with 

 in colour and other properties of the water, the 

 perature Ml rapidly to between 23 and 24 C., and to 

 C. in six fathoms off Flores Island close to Monte Video. 

 The minimum temperature observed in this part was 20 C. 



i. between Lobos Island and Maldonado Point. 

 Excluding the latter part of the voyage between the Ki\< i 

 an. I lat. 15 S.. where the conditions are a good deal 

 affected by purcl causes, the surface water shows well 



>.<<! diurnal maxima and minima of t< IHJM -ratui v. From 

 'N. to lat. 2 N. the ship passed through tin- c<piai 



nid i. tin-, which M'parates the regions of the noi t h 

 and the BOUtb-easI trade winds from each othe: 

 rised by a calm sea, a cloudy sky. and lu a 

 temperature was subject to very little diurnal vari.' 

 (o3 IMM- St Paul's Rock miles north 



louds cleared away comph -t.-ly, and t 



82 



