12 Meldrum, Dcvclopmen t of the A torn ic T/ieorj '. 



There is no reason to question this statement. It is 

 true that Dalton's historical narratives, as has been shown 

 in the second paper of this series, cannot be accepted at 

 their face value. But this is a contemporary statement, 

 and, as such, must receive a considerable degree of 

 credit. 



The physical theory was formed between April, 1800, 

 and September of the following year. There is no hint 

 of it in the title of the paper '.vhich Dalton read on the 

 1 8th April of the earlier year. Again, the date of the 

 first sketch of the theory, which he sent to NicJiolson's 

 Jotirnal, is the 14th September, 1801, and the theory can 

 hardly have arisen earlier than August. It is true that 

 Angus Smith assigns the reading of the essay " On the 

 Constitution of Mixed Gases" to July 31st, and October 

 2nd and i6th for the reading of the 2nd and 3rd essays 

 respectively.'^ But the dates mentioned at the head of 

 the papers in the MancJiester Memoirs, are the 2nd, i6th, 

 and 30th October. Dalton must have known the dates 

 on which his own papers were read, and as the author he 

 was interested in not dating them later than was neces- 

 sary. In the Minute-book of the Society the title of each 

 of these papers was entered on a left hand page, and the 

 date and other particulars of the meeting at which the 

 paper was read on the right hand page. Angus Smith 

 has made the slip, which one can easily understand, of 

 assigning the reading of a paper to the meeting minuted 

 on the previous page. 



The influence of Neivton on Dalton. 



The theory was formed under a new influence. 

 Between April, 1800, and August or September, 1801 



^" Angus Smith, "Memoir of Dalton," p. 254. These are not the 

 only wrong dates in his list of Dalton's papers. 



