INTRODUCTION. liij 



diversity of climate as to temperature and moisture. Through the 

 kindness of several gentlemen, I obtained information upon this sub- 

 ject, but have not deemed it necessary to embrace it on the dia- 

 gram. The principal causes affecting the climate of the Cape, are 

 the warm and cold currents ; those on the southeast side flow from 

 the equator, whilst those on the west come from the south polar 

 regions ; the winds from the southeast prevail from November to 

 April; these pass over the warm currents, and acquire their tem- 

 perature ; while those that prevail from May till October come 

 from the north and northwest, which pass over the cold currents. 

 The mean temperature in summer varies from 73 to 79, and in 

 winter from 57 to 62. The mean annual temperature is 67 Fahr. 

 The southeast, though they are polar winds, bring fine weather; those 

 from north and northwest, tropical winds, are accompanied by fogs, 

 mists, and rain. It is true that the former period comprises the sum- 

 mer, and the latter the winter months ; yet the peculiarity of climate 

 cannot well be accounted for, unless we ascribe it to these winds pass- 

 ing over and acquiring the temperature of the ocean water. During 

 our stay the mean height of the barometer was 3O078 inches, the 

 temperature of the air varied from 57 to 81, the degree of moisture 

 was found to be - 855. The height of the vapour plain is marked on 

 the face of the Table Mountain, at 1,000 feet above the level of the 

 sea. Near the Cape refractions in the atmosphere are very common. 

 I have made mention of them in the Narrative, to which I would 

 refer. These phenomena were constantly seen when the thermo- 

 meter at the mast-head differed from the one on deck. 



CAPE OF GOOD HOPE TO ST. HELENA AND NEWYOSK. Our passage 



was made to St. Helena in 15 days, during the latter part of April. 

 The course was direct: the temperature of the air on reaching the 17th 

 degree of latitude had increased from 64 to 73, that of the water 

 from 66'5 to 74. The barometer for the first feAV days continued 

 to fluctuate, and stood below 30 inches ; but as we increased our dis- 

 tance from the African coast, and until we reached St. Helena, it 

 remained above 30 inches. 



We entered the trades in 24 south latitude, 2 40' east longitude; 

 the winds had been quite moderate and very light from southwest to 

 southeast with a smooth sea, for ten days previously, and scarcely a 

 swell to give motion to the ship, during which time we passed over 

 800 miles of ocean. 



St. Helena is situated in mid-ocean, and affords a comparison 



14 



