132 



disappointed in not being able to sea the top of Scawfell, where we were the other 

 day. I observed one of the pikes of Broad Cragg, or whatever it may be called, 

 (I think it should have a more distinguishing appellation,) far above Gavel, with 

 Greatend, the difference is scarcely perceptible. Helvellyn is above the level, and 

 Skiddaw verj- little more than what may be allowed for the curvature. 



I left the hill a little before two, and by a rather rugged descent, found the 

 way to the Blacklead mines, where I rested a while. I arrived well at Keswick in 

 the evening ; the barometer had risen during my absence about the eleventh of an 

 inch. I hope you and your companion arrived safe at Kendal. 



(See also further correspondence on the subject of the Well loith Sir G. Airy.) 



Another letter to the same celebrated chemist gains additional 

 interest from its being one of the earhest inteIHgent accounts of the 

 Floating Island, and, as subsequently noticed, some of its particulars 

 were afterwards published in the Memoirs of the Manchester Philo- 

 sophical Society. 



September 14th, 1815. 

 Mr. Dalton, — 



I received yours of the Sth, and much obliged to you for the analysis of the 

 gas. The books for Mr. Knight shall be duly forwarded. 



Derwent Lake varied very little in height for about a month after you saw it, 

 which was unusually low for such a length of time. About the 6th day of August, 

 the Floating Island began to appear above water. I was upon it on the 21st, at 

 which time the lake had risen about eight inches, and the Island was only about 

 four inches above the level of the water ; its length was eighty-eight yards, its 

 greatest breadth twenty-five, but some part of it less than half that. The gas on 

 coming up had then a very perceptible smell, which I compare to that of a foul gun. 

 Whether this smeU is stronger when the Island first emerges, or whether when the 

 Island is sunk the smell is taken away by the greater depth of water through which 

 the gas ascends, I am not able to determine. I endeavoured to ascertain whether 

 the Island consisted of the same peat earth throughout, which I find to be nearly 

 the case ; and also to examine more particularly the earth underneath it, which I 

 have been inclined to call a Vegetable Oxide. On taking up some of this at the 

 depth of thirteen feet from the surface, I found it intermixed with specks of a 

 bluish green colour, which from its turning black with infusion of gall, I take to be 

 Sulphate of Iron ; this makes me suspect that in my hypothesis of the generation 

 of the gas, I may have laid too much stress upon the decomposition of vegetable 

 matter in the Island, or could the Iron be originally contained therein ? 



The gentleman who brought the book having kindly offered his services to take 



I 



