32 Observations on the Temperature of the Ocean and 

 April 5th. S. lat. 24° 22". W. long. 27° 8". 



Like the atmosphere, the ocean is subject to irregidarities of 

 temperature. This fact is proved by the Journal in an ample 

 manner. The causes which produce these irregularities may be 

 divided, very generally, into three kinds, — tempestuous weather, 

 shoals, and currents. 



Independent of other modes of operation — and they are various 

 in tempestuous u-eather — superficial currents appear to be esta- 

 blished in the course of the prevailing winds. If the wind be 

 from a cold quarter, the temperature of this current is compa- 

 ratively low, and vice versa. This fact is manifest in the effect 

 of the gales we experienced between the 7th and r2th of April, 

 during which time, being south of the equator, and the wind 

 blowing from the south, the temperature of the sea was consi- 

 derably reduced. 



Where the sea is shallow, it is now a well-established fact*, 

 that the temperature of the water is comparatively low ; an im- 

 portant circumstance, highly deserving the attention of the prac- 

 tical navigator ; it may forewarn him of a bank in the darkness 

 of night, when nothing else would indicate it, and put him on 

 his guard when approaching low shores and shallows, time 

 enough to avoid their dangers. In advancing towards the Cape 

 of Good Hope, and in doubling that promontory, and in making 

 Cevlon, I collected some observations on this subject, the re- 

 sults of whicli I shall now introduce. On making Table-bay, 

 before land was to be seen, there was a decided fall of the tem- 

 perature of the water, viz. from above 60 to 58, thus. 



May 1 1th. S. lat. 34^ \" . E. long. 17° 51" at 



8 A.M. the temperature of the water was 62,5 

 10 .. ■ .. .. 62,5 



12 .. .. .. 61,5 



2 P.M. .. .. .. 61 



5 .. .. .. 60 



* Observed by Dr. Franklin, Mr. J. Williams, S:c. — See Williams's Ther- 

 mometrical Navigation. Philadelphia 17^0. 



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