52 Coward & Harden, Daltoris Lecture Sheets. 



Sheet ii. 



Plate VI. 



Formula, inscribed " Ether, 104." 

 This requires C = 47, a value which we have not found 

 elsewhere. The representation of ether as a hydrocarbon, 

 C 2 H, appears in the note-books of 1803 and 1805, and 

 with doubt expressed in 1807. 



Sheet 12. 



Five oxides of nitrogen, represented as compounds of 

 one atom of nitrogen with one, two, three, four and five 

 atoms of oxygen respectively. It is improbable that 

 Dalton himself ever adopted these formulae for the oxides 

 of nitrogen. The sheet was perhaps used to illustrate 

 some contemporary views on the subject {e.g. T. Thomson, 

 Ann. Phil. 1814, 3, 135, gives a list containing four of 

 these oxides), or possibly even those of W. Higgins, " A 

 Comparative View of the Phlogistic and Antiphlogistic 

 Hypotheses," 132 — 5, 1789. 



Sheet 13. 



Five oxides of nitrogen, with names, as follows : 



1 atom nitrogen + 1 atom oxygen. ... "Nitrous gas," 



2 atoms ,, 1 ,, ,, ... "Nitrous oxide." 



1 atom ,, 2 atoms ,, ... "Nitrous acid." 



2 atoms ,, 3 ,, ,, ... " Subnitrous acid." 

 2 „ „ 5 „ ,, ... " Nitric acid." 



This represents Dalton's view at the time of the publi- 

 cation of the second volume of the " New System " (1827). 

 The same list is found in his paper in Thomson's Ann. 

 Phil. 1817, 9, 186, and is much different from that expres- 

 sing his opinions in 18 10. The note-books (vi, 20, 40) show 

 that the change in view occurred mainly in September or 

 October, 18 14. 



