OF DERWENT LAKE. 21 



been seen, although the water was on the 3rd of 

 October only about six inches higher than when 

 the island first made its appearance. 



Those who are inclined to attribute its rising 

 to some circumstance attending the change of 

 weather, may consider the present as support- 

 ing their argument ; but on such a supposition it 

 would be difficult to say, why it did not rise on 

 a similar change which took place in August. 



I cannot well account for the island* s going 

 down so readily ; as the temperature of both 

 the air and water have been kept up to an 

 unusual height for the season. Could the 

 lengthened nights and the want of light have 

 any effect in reducing the power or quantity of 

 the gas? 



I have frequently examined the temperature 

 of the lake, especially after its being strongly 

 agitated by the wind, in order to obtain a mean : 

 during the hot weather I sometimes found it 

 above 70°, and during the time of the island's 

 being above water it was about 62°. Before 

 the present month I never found it below 60°, 

 and this morning at six, after a very strong 

 S. S.W. wind, the water was 57°, the air being 

 59°. I never, since I kept a thermometer, found 



