139 



viz. that all the Slate Series dips one way, with considerable regularly, instead of 

 exhibiting, either "mantle -shaped" strata, around the great mountain masses, on 

 which Geognosts had so often fabled, or the ridged and troughed structure, which 

 I had supposed, and that the Coal-measures and under-coal Limestones, &c., lap 

 round the denudated edges of your slaty mountains, unconformahly on all sides, 

 even on the south-eastwards. 



From Dr. Dalton. 



Manchester, January 15th, 1826. 

 Dear Friend, — 



I received your letter and parcel all safe in due time in October last, and 



have to apologize for my neglecting to acknowledge it for so long a time. In the 



first place I was very unwell at the time, being confined to the house for two or 



three weeks by the most severe cold I ever had, and indeed in a great part to bed. 



It was accompanied by an affection of hearing I had never before ; I was so deaf 



for two or three weeks that I could not hear the church bells across the street, 



unless I was out of doors. However, I have since entirely recovered my former 



state of health. 



I wished also to analyze the air before I wrote, which I did as soon as I 

 recovered. I also read the greatest part of your letter at one of our more vacant 

 meetings of the Society, and have to return you the Society's thanks for your 

 communication, as well as my own. Indeed, as soon as I heard of the floating 

 island being astir, I was hoping that you would not let slip the opportunity of some 

 farther observations. If you have not published the substance of your letter, you 

 will perhaps have the goodness to extract what you may think proper for our next 

 volume, which however will not be published perhaps for a year or two. 



1 examined the bottles, of air : the new air and the old were exactly of the 

 same quality, a circumstance to me very surprising : I also had some of the old air 

 left, and they were all found to agree as nearly as could be : a little carbonic acid 

 being washed out, they all yield about half carhuretted hydrogen and half azote, 

 proportions which I never before met with in mixture, though I have found the 

 proportions various. Nothing adverse to your theory occurs from this : but it is 

 wonderful the same proportions should be found as were before. 



I examined the air from Helvellyn and Skiddaw. The former was considerably 

 inferior in oxygen to the air below ; and the latter a little, but much less than the 

 other. You will remember the atmosphere was changing much about the time 

 from the odd appearance of the clouds the evening we left Skiddaw. 



We have just had some severe frost : on Friday morning, the thermometer 16* 

 in town and 4° or 6* in the vicinity ; a slight cover of snow and fine clear frost in 

 the country. 



I remain, yours truly, 



JOHN DALTON. 



