HISTORY OF THE ATOMIC THEOEY. 55 



life occasionally he was accompanied by some of the younger 

 members of the family to whom he was now as a relation, and 

 we can well believe Miss Johns, when she says, " that to those 

 who have seen him only on ordinary occasions, it is impossible 

 to convey an idea of his enthusiasm on those occasions. He 

 never wearied." Jonathan Otley, the veteran guide, at 

 Keswick, who has spent his life mapping, describing, and 

 showing the country around, often accompanied Dalton, and 

 he has in a journal given an account of some of their excur- 

 sions* These were undertaken partly with a view of " bring- 

 ing into exercise a set of muscles, which would otherwise have 

 grown stiff," as Dalton said, and partly to make meteorological 

 observations, or to bring down air for analysis from the highest 

 points of the county, gas from the floating island, and minerals 

 from every hill. 



In order to give his habits of thought on objects not scien- 

 tific, a few of his letters may be introduced with advantage; at 

 the same time they will give an account of some portions of 

 his life, which would lose much of their interest if the words 

 of another were alone used. 



Having been invited to lecture at the Royal Institution, he 

 thus describes his visit in a letter to his brother, February 1st, 

 1804. His first visit to London had been made in 1792. 



" Dear Brother, I have the satisfaction to inform thee that 

 I returned safe from my London journey, last seventh day, 

 having been absent six weeks. It has, on many accounts, 

 been an interesting vacation to me, though a laborious one. 

 I went in a great measure unprepared, not knowing the nature 

 and manner of the lectures in the institution, nor the apparatus. 

 My first was on Thursday, December 22nd (1803), which 

 was introductory, being entirely written, giving an account of 

 what was intended to be done, and natural philosophy in 

 general. All lectures were to be one hour each, or as near as 

 might be. The number attending were from one to three 

 hundred of both sexes, usually more than half men. I was 



