Manchester Memoirs, Vol. lix. (191 5), No. 12. 65 



and carbonic acid, much as in the plate accompanying the 

 memoir " On the Constitution of Mixed Gases " read in 

 1 80 1 (Mem., 1802, 5, ii., Plate 8). On this sheet the 

 atoms are, in number, 



315 of nitrogen 

 81 of oxygen 

 9 of aqueous vapour 

 7 of carbonic acid. 



There is here a closer approach to the relative 

 numbers of molecules of the constituent gases of the 

 atmosphere, than in the memoir. The carbonic acid 

 figure is too high, and the sheet was therefore compiled 

 before Dalton's determination of the proportion of this 

 gas in the atmosphere (Mem., 1805, 6, 244. Paper read 

 in 1802). The date of the diagram is therefore probably 

 1 80 1 or 1802. 



Sheet 50. 



Fourteen atoms of nitric oxide are arranged regularly 

 within a rectangle ; in rectangles each exactly half the 

 size are arranged separately fifteen atoms of nitrogen and 

 fifteen of oxygen. 



Sheet 51. 



Spheres arranged as in " New System," I., i., Plate 3, 

 figs. 1 and 2, to illustrate the arrangement of atoms of 

 water and ice. The sheet differs from the figures in the 

 plate only in the numbers of spheres, not in their 

 arrangement. 



Sheet 52. 



Figures very like those of " New System," I., i., Plate 3, 

 figs. 3, 4, 5, 6. 



