60 Mr. Harvey on the Formation of Mists. 



The relations of these temperatures are exceedingly curious. 

 The temperature of the water being greater than that of the air 

 above it, was the cause of the formation of the mist ; — and the 

 temperature of the ground being below that of the air which re- 

 posed on its surface, was also the cause why no mist was ob- 

 served over its surface. The mass of air over the water was 

 8^ degrees, coWer than the stream; whereas the air on the 

 borders of the channel was 4° warmer than the ground on 

 which it reposed. 



Early in the month of September, at about 2 P.M., immense 

 masses of mist rolled in from the sea, filling the whole of the 

 harbour, and covering a portion of the surrounding land. At 

 three, the greater part had disappeared ; but a fine column of it 

 was observed in a perfect state of repose, over the bosom of 

 the creek which runs up to the little village of St. John's, at 

 the entrance to Hamoaze. Having taken a boat, for the pur- 

 pose of performing a few experiments, I found the temperature 

 of the air near the shore to be 68°, and the water 63°. On 

 approaching the mist, however, a depression of temperature 

 was gradually perceptible, and the thermometer was found suc- 

 cessively to indicate 65°, 64°, and 63° ; — and when the boat 

 was rowed into the centre of the mist, the temperature was 

 found to be 62°, and that of the water about 63^°. On retiring 

 from the mist, an elevation of temperature was immediately 

 perceptible, the mercury standing at 64°; and by proceeding to 

 a still greater distance, the temperature successively increased 

 to 65° and 67°, being within a degree of what it was on leav- 

 ing the shore. The column of mist soon afterwards disap- 

 peared. 



On the 13th of November, at 6 A.M., a very dense mist 

 covered the neighbouring land and water, rising above the 

 highest of the surrounding hills. At 8 A.M., I had occasion 

 to cross the river Tamer, the mist still shrouding the whole of 

 its surface, and that of the adjacent country. The part crossed 

 was about a mile in breadth, and many opportunities therefore 

 presented themselves, of estimating the temperatures of the sea 

 and mist. On the eastern border of the river, the air was 42°; 



