. Manchester Memoirs, Vol. Iv. (191 1), No. 45. 3 



This table of atomic weights is of extraordinary 

 interest because, besides being the earliest known, it is 

 based on the same ideas as the one published in the " New 

 System '' five years later. There is only one change : 

 sulphurous and sulphuric acids in the earlier table are 

 virtually SO and SOj respectively, and in the later table 

 they are SO. and SO.,. But this does not affect the fact 

 that after the table was drawn up in 1803, Dalton made 

 no essential change in the theory. The principles of 1S03 

 remain as nearly as possible unchanged in 1808, so far as 

 one can judge of principles by results. In the one 

 scheme just as in the other, the compound atom of water 

 consists of I atom of hydrogen and i of oxygen, that of 

 ammonia of i of hydrogen and i of nitrogen. Nitrous 

 gas is virtually NO, nitric acid is NO., nitrous oxide 

 N.O, carbonic oxide is CO, carbonic acid is CO2. 



Debus on the '' Dalton- Avogadro " hypothesis. 



Debus has devoted a series of papers to the study of 

 the principles on which Dalton arrived at chemical 

 formulae and atomic weights. The whole series may be 

 said to depend on the assumption that Dalton deliberately 

 made a mystery of the evolution of his theory. " Der 

 geniale Baumeister hat sorgfaltig alle Werkzeuge und 

 Plane entfernt und zeigt ohne einleitende Bemerkungen 

 sofort das fertige Gebaude." - This is the kind of state- 

 ment which ought not to be made except as the result of 

 an exhaustive study of the available material. Everyone 

 must admit that the subject is obscure, but, as will appear 

 in the course of this paper, there is little justification for 

 saying that Dalton deliberately (sorgfaltig) made it so. 

 The true explanation of the obscurity is that the task of 



- Zeitsch. pliysik. Chan., 1899, vol. 29, p. 266. 



