liitk Observations on the Analysis of SuU-hrines. 35 



observes, that at the border of the bank the current is strongest; 

 the high temperature of the water there, at least ten degrees 

 above the neighbouring seas, is readily accounted for on that 

 idea. We appear to have continued in the current seventeen 

 hours, the course the ship was going was nearly due east, her 

 averaoe rate 7'65 miles an hour; and hence, supposing we were 

 sailing immediately across the stream, as probably we were, or 

 very nearlv, its width may be inferred to be about 130 miles ; a 

 distance little differing from that commonly assigned to it. 

 Having traversed this current, we seem, from the low tempera- 

 ture of the water for two hours, to have been passing a bank 

 twelve miles wide, and then to have entered a second current 

 running in the same direction as the first. 



I have alluded to a connexion between these currents and 

 the covering of dense mist, that occasionally occurs on the Ta- 

 ble-mountain, called the " Table-doth." The connexion is 

 evident, and readily explained. The ph3enomenon only presents 

 itself when a cold wind blows, viz. the south-east. This wind 

 must condense the aqueous vapour rising from the warm current, 

 and carry it towards the land. During the short stay we made 

 at the Cape, I once had an opportunity of seeing the mist ad- 

 vancing; it came rapidly over the surface of the sea, which it 

 entirely concealed, whilst the air above was perfectly clear; it 

 soon reached the land, spread along the coast gradually, ascended 

 the mouutain, and there remained almost stationary, enveloping 

 the summit, sometimes increasing and descending on the opposite 

 side overhanging Cape Town, and sometimes diminishing and 

 retreating. That it should remain so nearly stationary on the 

 top of Table Hill, whilst the south-east wind continues, is not 

 surprising, considering the height of this hill, 3582 feet above the 

 level of the sea, its precipitous sides, and the extensive surface 

 of its top ; nor is it strange, that it should rarely descend, ex- 

 cept when the wind blows hard, taking into account the situation 

 of the ground beneath, sheltered and warm, and the site of a 

 large town, from which a current of hot air must be constantly 

 rising. 



I cannot conclude without insisting with Mr. JonathanWilliams 

 on the use of the thermometer at sea ; if commonly employed, 

 and the observations made with it recorded, a general knowledge 

 might soon Ije obtained of the average temperature of all parts 

 of the ocean, and a fund of curious and useful information might 

 be collected, especially respecting currents and shoals, that to 

 practical navigators could not fail of being highly serviceable. 



In another letter, I propose communicating to you the obser- 

 vations I have collected on the temperature of man and other 

 animals in different climates. The experiments were made du- 



C 2 ring 



